摘要:

Mendeleev Communications Electronic Version, Issue 5, 2001 1 New reactions of Hünig’s base with S2Cl2: formation of monocyclic 1,2-dithioles Lidia S. Konstantinova,a Oleg A. Rakitin*a and Charles W. Rees*b a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation. Fax: +7 095 135 5328; e-mail: orakitin@ioc.ac.ru b Department of Chemistry, Imperial College of Science, Technology and Medicine, London SW7 2AY, UK. E-mail: c.rees@ic.ac.uk 10.1070/MC2001v011n05ABEH001493 Systematic variation of the ratio of Hünig’s base 1 to S2Cl2 in their reactions in chloroform shows that, in addition to known tricyclic bisdithiolothiazine thiones 4 and 5, monocyclic dithiole-3-thiones 6 and 7 can be isolated; when the inert base DABCO is added the extent of sulfuration of the products is reduced and thiones are replaced by their oxo analogues, and diisopropylamines 15 are converted into monocyclic dithiol-3-ones 16; an overall mechanistic rationalisation of the results, extending earlier work, is presented.We have shown that N-ethyldiisopropylamine (Hünig’s base) 1 and other N-alkyldiisopropylamines are converted in one-pot reactions by disulfur dichloride, S2Cl2, and 1,4-diazabicyclooctane (DABCO) into fully unsaturated tricyclic bis[1,2]dithiolo- [3,4-b][4',3'-e][1,4]thiazines such as 3, 4 and 5.1–3 We proposed a mechanism for this transformation, which involves the conversion of isopropyl groups into 3-chlorodithiolium salts followed by formation of the central 1,4-thiazine ring and final nucleophilic displacement of the reactive 3-chloro groups.1 If the S2Cl2 is in molar excess over DABCO the dithiole rings are chlorinated further to give tricyclic N,N-bis(chlorodithiolyl)- amines, such as 2, as well as tricyclic products, such as 3 (Scheme 1).4 In all of these reactions, both isopropyl groups have been transformed into 1,2-dithiole rings.If only one isopropyl could be so transformed, we would have a new synthesis of monocyclic 3H-1,2-dithioles under unusually mild conditions.5 We therefore systematically investigated the reaction of Hünig’s base 1 with S2Cl2, varying the ratio of the reactants, initially in the absence of another base such as DABCO.The two reactants were mixed in chloroform for 3 days at 0 °C and then quenched by brief heating with formic acid, which gives cleaner reactions by converting the intermediate 1,2-dithiolium salts into 1,2-dithiol-3-ones.1 The four products shown in Scheme 2 were isolated in the yields given in Table 1.When the molar quantities of 1 and S2Cl2 are in ratio 0.9 to 1.2 (Table 1, entries 1–4), the main products are tricyclic bisdithiolothiazines 41 and 5.1 As the ratio of 1 to S2Cl2 increases, there is insufficient S2Cl2 to react with the second isopropyl group in 1 and monocyclic 1,2-dithiole-3-thiones 6† and 7 are indeed formed.In 6 the dithiole has been sulfurated at the 3- and 5-positions but as the relative amount of S2Cl2 decreases further, product 7 of mono-sulfuration appears. Separate experiments showed that 6 and 7 are converted into 4 and 5 in high yield by S2Cl2 (in the presence of DABCO or triethylamine to neutralise the hydrogen chloride liberated). It is striking that all the products in Scheme 2 have thiono groups, in spite of the final quench with formic acid, which usually converts chlorodithiolium intermediates into the keto compounds (see, for example, Scheme 1).This suggests that in the DABCO-free reactions the 3-chlorodithiolium ions are further chlorinated by S2Cl2 to give 3,5-dichloro salts and that both the mono- and dichlorodithiolium salts are attacked by some reactive sulfur nucleophile,‡ which is present in the Hünig’s base reactions without added DABCO, but not in those 1 L 6&O '$%&2 LL +&2+ 1 6 6 6 6 &O &O 2 2 1 6 6 6 6 2 2 6 6FKHPH N S S S S O S 4 S 1 i, S2Cl2, ii, HCO2H N S S S S S S 5 S N S S S 6 HS N S S S 7 Scheme 2 † General procedure for the reactions of tertiary amines with S2Cl2.Disulfur dichloride was added dropwise to a stirred solution of a corresponding amine and DABCO (in the case of N-ethyldiisopropylamine without DABCO) in chloroform at –15–20 °C. The mixture was stirred at 0 °C for 72 h.Formic acid (3.75 ml, 100 mmol) was added; the mixture was refluxed for 1.5 h, and filtered, and the solvents were evaporated. The residue was separated by column chromatography (Merck 60 Silica Gel, light petroleum and then light petroleum–CH2Cl2 mixtures). All new compounds were fully characterised by elemental analysis, 1H and 13C NMR, IR and mass spectra and HMRS. 15a: obtained from the commercial hydrochloride (Aldrich). 15b: an oil prepared from 15a and sodium azide in DMSO at room temperature in 88% yield. 6: yellow crystals, mp 128–130 °C. 1H NMR (CDCl3) d: 1.24 (t, 6H, 2Me, J 6.5 Hz), 1.61 (d, 3H, Me, J 6.5 Hz), 3.55 and 4.78 (2m, 2H, CH2), 4.93 (septet, 1H, CH, J 6.5 Hz), 8.70 (br. s, H, SH). 13C NMR (CDCl3) d: 198.73 (C=S), 193.71 (=C–SH), 133.83 (sp2 tertiary C), 57.75 (CH), 46.32 (CH2), 20.27, 18.97 and 10.76 (3Me).MS, m/z: 251 (M+, 100%), 236 (15), 218 (19), 208 (39). 7: yellow oil. 1H NMR (CDCl3) d: 0.99 (t, 3H, Me, J 7.2 Hz), 1.11 (d, 6H, 2Me, J 6.5 Hz), 3.06 (q, 2H, CH2, J 7.2 Hz), 3.96 (septet, 1H, CH, J 6.5 Hz), 7.71 (s, 1H, CH). 13C NMR (CDCl3) d: 211.89 (C=S), 154.69 (sp2 tertiary C), 141.07 (CH), 51.29 (CH), 40.35 (CH2), 20.15 and 13.43 (2Me).MS, m/z (%): 219 (M+, 69%), 204(36), 176 (38), 142 (31), 128 (28). 16a: yellow oil. 1H NMR (CDCl3) d: 1.11 (d, 6H, 2Me, J 6.5 Hz), 3.31 (m, 1H, CH), 3.39 (s, 4H, 2CH2). 13C NMR (CDCl3) d: 187.96 (C=O), 155.37 and 137.92 (2sp2 tertiary C), 54.65 (CH), 48.89 and 43.71 (2CH2), 22.45 (Me). IR, n/cm–1: 2980 (CH), 1660 (C=O). MS, m/z (%): 275 (M+, 4%), 273 (M+, 16), 271 (M+, 23), 236 (20), 222 (22), 182 (23), 180 (64). 16b: yellow oil. 1H NMR (CDCl3) d: 1.12 (d, 6H, 2Me, J 6.5 Hz), 3.17 and 3.29 (2m, 4H, 2CH2), 3.35 (m, 1H, CH). 13C NMR (CDCl3) d: 187.43 (C=O), 154.87 and 137.02 (2sp2 tertiary C), 54.33 (CH), 50.80 and 44.98 (2CH2), 21.50 (Me). IR, n/cm–1: 2970 (CH), 2120 (N3), 1660 (C=O). MS, m/z (%): 278 (M+, 10%), 222 (69), 180 (100). 16c: yellow oil. 1H NMR (CDCl3) d: 1.15 (d, 6H, 2Me, J 6.5 Hz), 3.51 (septet, 1H, CH, J 6.5 Hz), 4.01 (s, 2H, CH2). 13C NMR (CDCl3) d: 187.17 (C=O), 155.97 and 136.12 (2sp2 tertiary C), 117.15 (CN), 53.59 (CH), 35.92 (CH2), 21.17 (Me). IR, n/cm–1: 2980 (CH), 2140 (CN), 1660 (C=O). MS, m/z (%): 248 (M+, 57%), 233 (43), 212 (32), 206 (55), 179 (36). ‡ This nucleophile is not S8 formed in the reaction since addition of S8 to the initial reaction mixture made no significant difference to the product distribution.Mendeleev Communications Electronic Version, Issue 5, 2001 2 with DABCO.This difference could arise from the greater nucleophilicity of DABCO over Hünig’s base. DABCO could attack S2Cl2 at sulfur to give salt 8, whilst the much more sterically demanding Hünig’s base is more likely to attack S2Cl2 at a terminal chlorine atom to give 9.The latter generates the Cl–S–S– anion, which could rapidly convert a 3-chlorodithiolium salt into the corresponding 3-thione and SCl2. An outline mechanism for the formation of 4 to 7 is suggested in Scheme 3. Some of the early steps have been given in more detail before.1 In the DABCO-containing reaction, electrophilic species 8 could act as a chlorinating agent to give ultimately tetrachloro compound 13, which, in the absence of a strong sulfur nucleophile like Cl–S–S–, would be converted by formic acid into bis-keto compound 2.The formation of monocyclic products 6 and 7 and their conversion into tricyclic products 4 and 5 lends support to our overall mechanism1 in which the dithiole rings are formed first, followed by completion of the central 1,4-thiazine ring to give tricyclic bisdithiolothiazines 3–5.Having established (Scheme 2) that treatment of Hünig’s base with S2Cl2 could provide a route to monocyclic 1,2-dithiole-3- thiones 6 and 7, we tried to enhance the utility of the reactions by replacing that part of starting amine 1 which is acting simply as a base by another more inert tertiary amine, DABCO.Furthermore, the reactions were conducted at 0 °C to minimise conversion of the second isopropyl group. Under these conditions, a new reaction, which involved an attack at the ethyl rather than isopropyl group of Hünig’s base, was observed; however, other substituted diisopropylamines gave monocyclic 1,2-dithioles in low to modest yields among other products.Thus, the treatment of amines 15a, 15b and 15c6 with S2Cl2 (7 equiv.) and DABCO (7 equiv.) in chloroform at 0 °C for 3 days followed by addition of formic acid and heating under reflux for 1.5 h gave 5-chloro- 1,2-dithiol-3-ones 16a (32%), 16b (12%) and 16c (20%), respectively (Scheme 4). In agreement with the proposed mechanism (Scheme 3), the combination of an excess of S2Cl2 over tertiary amine 15 and the presence of DABCO is expected to yield dichlorodithiolium salt (cf. 11 in Scheme 3), which, in the absence of a strong sulfur nucleophile, gives 5-chlorodithiol-3-one 16 rather than dithiole-3-thione. In summary, these experiments throw further light on the likely mechanism of the complex reactions between Hünig’s base and S2Cl2, which have now produced no less than 13 different products.Furthermore, they show that monocyclic 1,2-dithiol- 3-ones and 3-thiones can be added to the bicyclic and tricyclic products already reported for these simple one-pot reactions.1–4 This work was supported by the Russian Foundation for Basic Research (grant no. 99-03-32984a), the Royal Society, MDL Information Systems (UK) Ltd and an RSC Journals Grant to O.A.R., and we thank the Wolfson Foundation for establishing the Wolfson Centre for Organic Chemistry in Medical Science at Imperial College. References 1 (a) C.F. Marcos, C. Polo, O. A. Rakitin, C.W. Rees and T. Torroba, Angew. Chem., Int. Ed. Engl., 1997, 36, 281; (b) C. W. Rees, A. J. P. White, D. J. Williams, O.A. Rakitin, C. F. Marcos, C. Polo and T. Torroba, J. Org. Chem., 1998, 63, 2189. 2 (a) C. F. Marcos, O. A. Rakitin, C. W. Rees, L. I. Souvorova, T. Torroba, A. J. P. White and D. J. Williams, Chem. Commun., 1998, 453; (b) C. W. Rees, A. J. P. White, D. J. Williams, O. A. Rakitin, L. S. Konstantinova, C. F. Marcos and T. Torroba, J. Org. Chem., 1999, 64, 5010. 3 (a) C. F.Marcos, O. A. Rakitin, C. W. Rees, T. Torroba, A. J. P. White and D. J.Williams, Chem. Commun., 1999, 29; (b) L. S. Konstantinova, N. V. Obruchnikova, O. A. Rakitin, C. W. Rees and T. Torroba, J. Chem. Soc., Perkin Trans. 1, 2000, 3421. 4 S. Barriga, L. S. Konstantinova, C. F. Marcos, O. A. Rakitin, C. W. Rees, T. Torroba, A. J. P. White and D. J. Williams, J. Chem. Soc., Perkin Trans. 1, 1999, 2237. 5 C. Th. Pedersen, Adv. Heterocycl. Chem., 1982, 31, 63. 6 D. B. Luten, J. Org. Chem., 1939, 3, 588. Table 1 Reaction of Hünig’s base 1 (x mmol) with S2Cl2 (10 mmol) in CHCl3 (25 ml). Entry Quantity of Hünig’s base 1 (x mmol) Product yield, mmol (%)a aYields are calculated on the basis that 15 mol of Hünig’s base 1 should give 1 mol of 4 or 51 together with 14 mol of the Hünig’s base hydrochloride, and analogously 7 mol of the Hünig’s base should give 1 mol of 6 or 7. 4 5 6 7 1 9 0.20 (33) 0 0 0 2 10 0.14 (21) 0.01 (1.5) 0 0 3 11 0.11 (15) 0.03 (4) 0.04 (2.5) 0 4 12 0.08 (10) 0.06 (7.5) 0.06 (3.5) 0 5 13 0 0.13 (15) 0.12 (6.5) 0 6 15 0 0.12 (12) 0.12 (5.5) 0 7 18 0 0 0.38 (15) 0.08 (3) 8 20 0 0 0.72 (25) 0.23 (8) 9 22 0 0 0.68 (22) 0.32 (10) 1 1 6 6 &O &O 6 6 &O &O1(W3U L N S S Cl 10 1 S2Cl2 N S S S S Cl Cl N S S S 6 HS N S S S 7 Scheme 3 N S2Cl2 12 SSCl N S S Cl 11 Cl S2Cl2 SSCl S2Cl2 N S S S S Cl Cl 13 Cl Cl SSCl N S S S S Cl S 14 Cl Cl SSCl 5 4 SSCl HCOOH 5 1 5 1 6 6 &O 2 L 6&O '$%&2 LL +&2+ D 5 &+&+&O E 5 &+&+1 F 5 &+&1 6FKHPH Received: 4th July 2001; Com. 01/1819

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年代:2001

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Mendeleev Communications Electronic Version, Issue 5, 2001 1 Direct conversion of N-ethylamines into functionalised amides by S2Cl2 Lidia S. Konstantinova,a Oleg A. Rakitin*a and Charles W. Rees*b a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation. Fax: +7 095 135 5328; e-mail: orakitin@ioc.ac.ru b Department of Chemistry, Imperial College of Science, Technology and Medicine, London SW7 2AY, UK.E-mail: c.rees@ic.ac.uk 10.1070/MC2001v011n05ABEH001504 Hunig¡�s base 1 is known to react extensively with S2Cl2 to give monocyclic, bicyclic and fused tricyclic 1,2-dithioles with the N-ethyl group intact, but with S2Cl2 and DABCO in chloroform at 0 ¡ÆC 1 is converted into dichloroacetamide 2 by selective reaction of the N-ethyl group in a new one-pot transformation; ethyl-substituted derivatives of 1, diethylisopropylamine 17 and triethylamine react similarly though the last, less bulky, amine also gives trichloroacetamide 20.We have recently shown that the complex reaction between Hunig¡�s base 1 and disulfur dichloride, S2Cl2, which gives bicyclic bis(1,2-dithiol-4-yl)amines1 and tricyclic bis[1,2]dithiolo- [1,4]thiazines2 can, with a deficiency of S2Cl2, also give intermediate monocyclic 1,2-dithioles in low to moderate yield.3 Since this reaction is an unusually mild route to 1,2-dithioles,4 we attempted to increase its synthetic utility by replacing that part of the Hunig¡�s base which neutralises the hydrogen chloride liberated, by another amine DABCO; also the reaction temperature was lowered to 0 ¡ÆC to minimise conversion of the second isopropyl group. Unexpectedly, these conditions led to an entirely different reaction in which the isopropyl groups are unchanged and the ethyl group is transformed into a dichloroacetyl group, which, as far as we are aware, is a new transformation. Thus, Hunig¡�s base with S2Cl2 (7 equiv.) and DABCO (7 equiv.) in chloroform at 0 ¡ÆC for 3 days followed by addition of formic acid1.3 and heating for 1.5 h gave (N-dichloroacetyl)diisopropylamine 2¢Ó (41%) (Scheme 1).This conversion of Hunig¡�s base into amide 2 is the first example that we have encountered, in many such S2Cl2 reactions, of attack at its ethyl rather than isopropyl group, in the presence or absence of other bases.1,2 The key reaction is presumably oxidation of the tertiary amine to an iminium ion by S2Cl2.DABCO complex 3,3 which is a potential source of Cl+ and Cl., and the outcome depends upon which iminium ion is formed.We assume that the present mild (0 ¡ÆC) conditions result in oxidative removal of the less hindered ¥á-hydrogen, i.e., from ethyl rather than isopropyl, to give kinetically controlled iminium ion 4 (Scheme 2) rather than the, presumably more stable, alternative.Ion 4 can isomerise to enamine 5, which can be oxidised further, as shown in Scheme 2, to give ultimately tetrachloro species 6, which is converted into product 2 by formic acid. Once the ethyl group has been oxidised (Scheme 2), the N-isopropyl groups will be deactivated to electrophilic attack.N-Dichloroacetyl diisopropylamine 2 is inert to the reaction mixture even at room temperature, and we have previously shown that N-acetyl- and N-cyanodiisopropylamine are inert to S2Cl2 under similar conditions.2 The formation of iminium ion 4 to the exclusion of its isomer has previously been demonstrated by Schreiber10 in the oxidation of Hunig¡�s base with trifluoroacetic anhydride in dichloromethane at 0 ¡ÆC; no attack at isopropyl was detected.In the Hunig¡�s base.S2Cl2 reactions, there is a relatively fine balance between conversion of the ethyl group into dichloroacetyl (Schemes 1 and 2) and the isopropyl group into dithioles,3 bisdithioles1 and bisdithiolothiazines.2 It could be instructive to see how substituents on the ethyl group influence this balance.We therefore treated N-(2-chloroethyl)diisopropylamine 7 with S2Cl2, DABCO and formic acid under the same conditions as for 1. Two products were isolated: the same dichloroacetyl compound 2 (21%) as from 1 and 1,2-dithiole-3-one 83 (34%) (Scheme 3). The chloroethyl group has been oxidised like the ethyl group but presumably more slowly, thus allowing competing oxidation of isopropyl to give dithiolone 8.On the above ¢Ó General procedure for the reaction of tertiary amines with S2Cl2. Disulfur dichloride (0.8 ml, 10 mmol) was added dropwise at .15.20 ¡ÆC to a stirred solution of a corresponding amine (2 mmol) and DABCO (10 mmol) (in the case of N-ethyldiisopropylamine without DABCO) in chloroform (25 ml). The mixture was stirred at 0 ¡ÆC for 72 h.Formic acid (3.75 ml, 100 mmol) was added, the mixture was refluxed for 1.5 h and filtered; and the solvents were evaporated. The residue was separated by column chromatography (Silica gel Merck 60, light petroleum and then light petroleum.CH2Cl2 mixtures). All new compounds were fully characterised by elemental analysis, 1H and 13C NMR, IR and mass spectra, and HMRS. Dichloroacetamides 2, 18, 19, trichloroacetamide 20 and compound 11 are identical with the known compounds.5.9 9: an oil prepared from 7 and sodium azide in DMSO at room temperature in 88% yield. 10: yellow oil. 1H NMR (CDCl3) d: 1.10 (d, 6H, 2Me, J 6.5 Hz), 3.10. 3.45 (m, 5H, CH, 2CH2). 13C NMR (CDCl3) d: 187.42 (C=O), 154.87 and 137.02 (2sp2 tertiary C), 54.33 and 50.80 (2CH2), 44.98 (CH), 21.50 (Me).IR, n/cm.1: 2980 (CH), 2120 (N3), 1660 (C=O). MS, m/z (%): 278 (M+, 11%), 222 (69), 180 (100). 13: yellow oil. 1H NMR (CDCl3) d: 1.12 (d, 6H, 2Me, J 6.6 Hz), 3.51 (q, 1H, CH, J 6.5 Hz), 4.01 (s, 2H, CH2). 13C NMR (CDCl3) d: 187.17 (C=O), 155.97 and 136.12 (2sp2 tertiary C), 117.15 (CN), 53.59 (CH), 35.93 (CH2), 21.17 (Me). IR, n/cm.1: 2980 (CH), 2140 (CN), 1660 (C=O). MS, m/z (%): 248 (M+, 74%), 233 (47), 206 (61), 179 (33). 14: yellow crystals, mp 75.78 ¡ÆC. 1H NMR (CDCl3) d: 1.35 (d, 6H, 2Me, J 6.2 Hz), 1.57 (d, 6H, 2Me, J 6.2 Hz), 4.26 (br. s, 2H, 2CH). 13C NMR (CDCl3) d: 163.74 (C=S), 113.02 (CN), 51.86 (CH), 21.42 and 18.53 (2Me). IR, n/cm.1: 2980 (CH), 2150 (CN). MS, m/z (%): 170 (M+, 87%), 127 (86), 113 (14), 101 (43). N i, S2Cl2, DABCO, 0 ¡ÆC ii, HCO2H 1 N CHCl2 2 O N N S S Cl Cl. 3 Scheme 1 1 R2N R2N R2N Cl Cl. 5 4 R2N Cl Cl R2N Cl Cl R2N Cl Cl R2N Cl Cl R2N CHCl2 O Cl Cl. R2N Cl Cl Cl Cl 6 HCO2H 2 Scheme 2 R = PriMendeleev Communications Electronic Version, Issue 5, 2001 2 mechanism (Scheme 2) formation of isopropyl-functionalised product 8 should be favoured by a higher reaction temperature and formation of ethyl-functionalised product 2 by a lower reaction temperature.Some evidence for this was obtained by running the reaction exactly as before but in boiling chloroform (61 °C) when several products, all of which were cyclic 1,2-dithiole derivatives,1–3 were formed in low yields, and only traces of compound 2 were seen (TLC). When the same reaction was run at –20 °C, all transformations were much slower and only a low yield (12%) of compound 8 could be isolated.N-(2-Azidoethyl)diisopropylamine 9 treated similarly also reacted by both pathways to give corresponding dithiolone 103 (12%) and an acyldiisopropylamine; the latter was not the analogous 2-azidoacetyl derivative but cyanoformyl derivative 11 (19%) (Scheme 4) obtained as a yellow oil. This product could arise readily by the general mechanism of Scheme 2 with a late diversion, caused by elimination of nitrogen and formation of the cyano group, as shown in Scheme 4.Formation of cyanoformamide 11 from azidoethyl compound 9 prompted similar treatment of N-(cyanomethyl)diisopropylamine 12,11 which was expected to give the same product 11 but possibly in higher yield. However, cyanothioformyl derivative 14 (24%), mp 75–77 °C, was formed instead, together with dithiolone 133 (20%) (Scheme 5).Formation of thioamide 14 instead of carboxamide 11, after formic acid treatment, suggests that a different mechanism is operating. It seems reasonable that S2Cl2 could be reactilfur, with the activated methylene group of 12. This could be through its ketenimine tautomer 15 as shown in Scheme 5 or by a radical mechanism induced by the enhanced stabilisation of captodative radical 16.12 When one of the isopropyl groups of Hünig’s base was replaced by ethyl, the same conversion of ethyl into dichloroacetyl by S2Cl2 was observed. Thus, diethylisopropylamine 17 with S2Cl2 and DABCO in chloroform at 0 °C for 3 days, followed by the formic acid treatment, gave dichloroacetamide 18 (34%); when run at 20 °C for 3 days, the yield was 54% (Scheme 6).When both isopropyl groups of Hünig’s base were replaced by ethyl, the same reaction was observed, to give dichloroacetamide 19 in 51% yield; however, at lower temperatures (0 °C and –20 °C), the yield of 19 is much reduced (to 8% and to traces, respectively) and the major product is now trichloroacetyl derivative 20 (22%). The direct transformation of N-Et to N-COCCl3 also appears to be new.Formation of 20 in addition to 19 could result from reduced steric hindrance by the ethyl groups in the chlorination sequence of Scheme 2, before the formic acid reaction. The established formation of monocyclic, bicyclic and fused tricyclic 1,2-dithioles from ethylisopropylamines and S2Cl2 requires attack at the isopropyl groups.We have now shown that the presence of DABCO in the cold reaction mixture favours selective attack at the ethyl group to give N-dichloroacetyl derivatives such as 2, 18 and 19, probably by the mechanism of Scheme 2. Ethyl-substituted diisopropylamines behave similarly, by minor variations of this mechanism, to give 2, 11 and 14, and the less bulky triethylamine also gives some of trichloroacetyl derivatives 20.This work was supported by the Russian Foundation for Basic Research (grant no. 99-03-32984a), the Royal Society, MDL Information Systems (UK) Ltd and an RSC Journals Grant to O.A.R., and we thank the Wolfson Foundation for establishing the Wolfson Centre for Organic Chemistry in Medical Science at Imperial College.References 1 S. Barriga, L. S. Konstantinova, C. F. Marcos, O. A. Rakitin, C.W. Rees, T. Torroba, A. J. P. White and D. J. Williams, J. Chem. Soc., Perkin Trans. 1, 1999, 2237. 2 (a) C. F. Marcos, C. Polo, O. A. Rakitin, C. W. Rees and T. Torroba, Angew. Chem., Int. Ed. Engl., 1997, 36, 281; (b) C. W. Rees, A. J. P. White, D. J.Williams, O.A. Rakitin, C. F. Marcos, C. Polo and T. Torroba, J. Org. Chem., 1998, 63, 2189; (c) C. F. Marcos, O. A. Rakitin, C. W. Rees, L. I. Souvorova, T. Torroba, A. J. P. White and D. J. Williams, Chem. Commun., 1998, 453; (d) C. W. Rees, A. J. P. White, D. J. Williams, O. A. Rakitin, L. S. Konstantinova, C. F. Marcos and T. Torroba, J. Org. Chem., 1999, 64, 5010; (e) C. F. Marcos, O.A. Rakitin, C. W. Rees, T. Torroba, A. J. P. White and D. J. Williams, Chem. Commun., 1999, 29; (f) L. S. Konstantinova, N. V. Obruchnikova, O. A. Rakitin, C. W. Rees and T. Torroba, J. Chem. Soc., Perkin Trans. 1, 2000, 3421. 3 L. S. Konstantinova, O. A. Rakitin and C.W. Rees, Mendeleev Commun., 2001, 165. 4 (a) C. Th. Pedersen, Adv. Heterocycl. Chem., 1982, 31, 63; (b) C. Th. Pedersen, Sulfur Rep., 1995, 16, 173. 5 A. D. Swensen and W. E.Weaver, J. Am. Chem. Soc., 1948, 70, 4060. 6 H. Hansen, K. Eicken and B. Wuerzer, Patent Ger. Offen. 2832974, 1980 (Chem. Abstr., 1980, 92, 192747t). 7 A. J. Speziale and R. C. Freeman, J. Am. Chem. Soc., 1960, 82, 903. 8 A. J. Speziale and R. C. Freeman, in Organic Syntheses, ed. N. Rabjohn, John Wiley, New York–London–Sydney, 1973, coll. vol. 5, p. 387. 9 W. G. Phillips and K. W. Ratts, J. Org. Chem., 1972, 37, 1526. 10 S. L. Schreiber, Tetrahedron Lett., 1980, 21, 1027. 11 D. B. Luten, J. Org. Chem., 1938, 3, 588. 12 D. J. Pasto, J. Am. Chem. Soc., 1988, 110, 8164. N Cl N Cl i, S2Cl2, DABCO, 0 °C ii, HCO2H S S Cl O N CHCl2 O Scheme 3 7 8 2 N N3 N N3 i, S2Cl2, DABCO, 0 °C ii, HCO2H S S Cl O N CN O Scheme 4 R2N Cl H N3 9 10 11 [Cl+] R2N Cl H N Cl N2 – N2 – H+ R2N CN Cl Cl R = Pri HCO2H N CN N CN i, S2Cl2, DABCO, 0 °C ii, HCO2H S S Cl O N CN S Scheme 5 R2N C H 12 13 14 R2N S H R2N CH R = Pri N H Cl S SCl SCl CN CN 15 16 – HCl – "S" Scheme 6 N N CHCl2 O i, S2Cl2, DABCO ii, HCO2H 17 18 Et3N i, S2Cl2, DABCO ii, HCO2H Et2N COCHCl 2 Et2N COCCl3 19 20 Received: 18th July 2001; Com. 01/1830

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Mendeleev Communications Electronic Version, Issue 5, 2001 1 Planar hexacoordinated boron in organoboron compounds: an ab initio study Tatyana N. Gribanova, Ruslan M. Minyaev* and Vladimir I. Minkin Institute of Physical and Organic Chemistry, Rostov State University, 344090 Rostov-on-Don, Russian Federation. Fax: +7 8632 43 4667; e-mail: minyaev@ipoc.rsu.ru 10.1070/MC2001v011n05ABEH001461 Ab initio [MP2(fu)/6-31G**, MP2(fu)/6-311G**] and DFT [B3LYP/6-31G**, B3LYP/6-311G**] calculations predict stable planar structures of the nonclassical compounds BB6(CH)3 and BB6X2 .(X = NH, O) containing a hexacoordinated central boron atom. Nonclassical organoelement systems, particularly those containing hypercoordinated planar centres are of considerable theoretical and practical interest.1 Recently, unusual stable planar molecular systems 1 and 2 and their isomers containing planar hexacoordinated carbon centres have been predicted by ab initio calculations.2,3 These structures with a hexacoordinated planar carbon atom are stabilized through the multicentre interactions of the central atom with the ligands.One may expect that the same bonding type may also occur in similar structures of hypercoordinated central atoms of other main-group elements, particularly, in boron-containing compounds.A possibility of stabilization of such compounds is supported by theoretical works on boron clusters including planar or quasi-planar boron atoms.4.6 Here, we report on ab initio [MP2(fu)/6-31G**, MP2(fu)/ 6-311G**]7 and density functional theory [B3LYP/6-31G**, B3LYP/6-311G**]8 calculations on compounds 3 and 4 (X = = NH, O), which contain a hexacoordinated planar boron centre.According to the calculations, compounds 3 and 4 (X = NH, O) possess highly symmetrical planar structures and correspond to minima (l = 0; hereafter, l designates the number of hessian negative eigenvalues at a given stationary point) on the corresponding potential energy surfaces (PES).Their geometric and energy characteristics are listed in Table 1 and depicted in Figure 1. The Bc.B bond lengths formed by the central boron (Bc) with the vicinal borons in 3 are about ~1.7 A; this value is in the range of available experimental data9 on BB single bonds. These bonds are 0.1 A longer than the peripheral BB bonds.The multicentre type of bonding in the BcB6 coordination site is illustrated by the shapes of the respective molecular orbitals of 3 shown in Figure 2. An additional contribution to the stability of the planar polycyclic structure of 3 is provided by the interaction of the vacant pz-orbital located at the Bc centre with the ¥�-system of the ligand environment. The molecule of 3 is a 6¥�-electron aromatic system with three occupied ¥�-orbitals (Figure 3).Electron density corresponding to the 1a2''-orbital (Figure 3) is delocalised on the entire system, electron density defined by the 1e''-orbitals is localised inside of the B2CH fragments. Thus, these three ¥�-orbitals are bonding. According to Mulliken orbital population analysis, central boron in 3 possesses a vacant p¥�-orbital and, thus, does not contribute electrons into the total ¥�-system.Each of the B2CH fragments contributes two ¥�-electrons to the total ¥�-system of 3. Therefore, it is ¥�-isoelectronic to the aromatic cyclopropenyl cation and possesses ¡®local¡� aromaticity. Rather strong ¥�-interaction inside the B2CH fragments is evidenced by the short (1.46.1.47 A) lengths of the BC bonds, which are considerably shorter than single BC bonds (1.6.1.7 A)10,11 and are close to the lengths of typical BC double bonds (~1.4.1.45 A).12 Compound 3 also has short peripheral BB bonds (1.64 A) whose lengths are comparable with those of BB double bonds (~1.63 A).12 The stability of anions 4 with central hypercoordinated boron is also due to the formation of multicentre bonds of the central atom with surrounding ligands. The calculated bond lengths BB¥á and BB¥â are in the range characteristic of standard single BB B C B B B B B X X C C B B B B C X = NH, O 1, D2h 2, C2v B B B B B B B X X X = NH, O 4, D2h ¥á ¥â B B B B B B B H H H 3, D3h Table 1 Ab initio and DFT data for compounds 3 and 4.a aEtot (in a.u.) is the total energy (1 a.u.= 627.5095 kcal mol.1); l is the number of the negative hessian eigenvalues; ZPE (in a.u.) is the harmonic vibration zero-point correction; w1 (in cm.1) is the lowest harmonic vibration frequency.Compound Method Etot l ZPE w1 3 MP2(fu)/6-31G** MP2(fu)/6-311G** B3LYP/6-31G** B3LYP/6-311G** .288.986615 .289.207299 .289.947847 .290.005892 0000 0.074912 0.073563 0.073959 0.073558 63.8 71.7 119.3 115.2 4 (X = NH) MP2(fu)/6-31G** MP2(fu)/6-311G** B3LYP/6-31G** B3LYP/6-311G** .283.772298 .284.019274 .284.677995 .284.757773 0000 0.061120 0.060076 0.060390 0.059998 87.4 93.4 120.6 91.7 4 (X = O) MP2(fu)/6-31G** MP2(fu)/6-311G** B3LYP/6-31G** B3LYP/6-311G** .323.472887 .323.753393 .324.438428 .324.529137 0000 0.036851 0.036185 0.036625 0.036344 35.0 46.0 95.7 34.3 Figure 1 Geometry parameters of the structures of 3 and 4 calculated by ab initio and DFT methods.The bond lengths and angles are indicated in angstrom units and degrees, respectively. 3, D3h 4 (X = NH), D2h 4 (X = O), D2hMendeleev Communications Electronic Version, Issue 5, 2001 2 bonds (~1.7 A). A peculiar feature of systems 4 is very short B¥á.B¥â bonds (1.55.1.57 A), which are appreciably shorter than experimentally determined BB double bonds (~1.63 A).12 The ¥�-electronic system of anions 4 contains eight ¥�-electrons, two of which coming from the B¥á centre.Thus, the valent state of the B¥á atoms in 4 does not correspond to the ¡®classical¡� sp2-hybridization with a vacant p¥�-orbital. The electron occupation of the B¥á p¥�-orbitals is corroborated by the data of Mulliken population analysis indicating a large (about .0.3 e) negative charge on each of the B¥á atoms.As distinct from B¥á, the valent state of other four boron atoms, B¥â, may be described in terms of ¡®classical¡� sp2-hybridization with a vacant p¥�-orbital. Such a distinction facilitates the B¥á.B¥â charge transfer, leads to strong interligand ¥�-interaction and contributes to stabilization of the planar system with hypercoordinated central boron.Another stabilising factor is the aromaticity of anions 4: all bonding ¥�-orbitals are occupied by electrons, whereas all antibonding ¥�-orbitals remain vacant. Note that all of the BN bonds in the polycyclic system of 4 (X = NH) are weaker than usual ¥�-dative BN bonds: the calculated lengths of the BN bonds in 4 are equal to 1.44 A, and they are notably longer than the experimental lengths of ¥�-dative BN bonds (1.38.1.41 A).13 Similar effect of weakening ¥�-interaction between B and N in the case of inclusion of boron atoms into BB double bonds is well known.13 The replacement of NH groups by a more electronegative oxygen atom leads to strengthening the BB¥â bonds in 4 (X = O) and to weakening the B¥á.B¥â and B.B¥á bonds.The latter effect leads to destabilization of the system. Nonetheless, the structure of 4 (X = O) corresponds to a minimum (l = 0) on the PES. At the same time, low values of the first harmonic vibration frequencies point to the shallowness of this minimum and, consequently, to low kinetic stability of the structure of 4 (X = O).In conclusion, the results of the calculations of hypothetical compounds 3 and 4 testify that there are three important factors leading to the stabilization of planar hexacoordinated central boron atom: (1) the ¥�-interaction of hypercoordinated central boron with the ligands in its environment; (2) the strong interligand bonding and (3) the aromaticity of polycyclic systems (the occupation of all bonding and the vacancy of all anti-bonding ¥�-orbitals).This work was supported by the Russian Foundation -97320). References 1 V. I. Minkin, R. M. Minyaev and Yu. A. Zhdanov, Nonclassical Structures of Organic Compounds, Mir, Moscow, 1987. 2 R. M. Minyaev and T. N. Gribanova, Izv. Akad. Nauk, Ser.Khim., 2000, 786 (Russ. Chem. Bull., 2000, 49, 783). 3 K. Exner and P. v. R. Schleyer, Science, 2000, 290, 1937. 4 J. E. Fowler and J.M. Ugalde, J. Phys. Chem., 2000, 104, 397. 5 (a) I. Boustani, Surface Sci., 1997, 370, 355; (b) I. Boustani, Phys. Rev. B, 1997, 55, 1. 6 I. Boustani, A. Quandt and A. Rubio, J. Solid State Chem., 2000, 154, 269. 7 M. W. Schmidt, K. K. Baldridge, J.A. Boatz, S. T. Elbert, M. S. Gordon, J. H. Jensen, S. Koseki, N. Matsunaga, K. A. Nguyen, S. J. Su, T. L. Windus, M. Dupuis and J. A. Montgomery, J. Comput. Chem., 1993, 14, 1347. 8 M. J. Frisch, G.W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, V. G. Zakrzewski, J. A.Montgomery, Jr., R. E. Stratmann, J. C. Burant, S. Dapprich, J. M. Millam, A. D. Daniels, K.N. Kudin, M. C. Strain, O. Farkas, J. Tomasi, V. Barone, M. Cossi, R. Cammi, B.Mennucci, C. Pomelli, C. Adamo, S. Clifford, J. Ochterski, G. A. Petersson, P. Y. Ayala, Q. Cui, K. Morokuma, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. Cioslowski, J. V. Ortiz, A. G. Baboul, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, R. L. Martin, D.J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, J. L. Andres, C. Gonzalez, M. Head-Gordon, E. S. Replogle and J. A. Pople, Gaussian 98, Revision A.9, Gaussian, Inc., Pittsburgh PA, 1998. 9 M. Hildenbrand, H. Pritzkow and W. Siebert, Angew. Chem., Int. Ed. Engl., 1985, 24, 759. 10 M. Hargittai and I. Hargittai, The Molecular Geometries of Coordination Compounds in Vapour Phase, Akademia Kiado, Budapest, 1975. 11 A. F. Wells, Structural Inorganic Chemistry, 5th edn., Claredon Press, Oxford, 1986. 12 P. Power, Inorg. Chim. Acta, 1992, 198.200, 443. 13 A. Moezzi, R. A. Bartlett and P. P. Power, Angew. Chem., Int. Ed. Engl., 1992, 31, 1082. Figure 2 Shapes of multicentre ¥ò-molecular orbitals in the structure of 3 [MP2(full)/6-31G** calculations]. 6a'1 8e' Figure 3 Occupation of ¥�-orbitals in 3 [MP2(full)/6-31G** calculations]. 2 0 .2 .4 .6 .8 .10 .12 Received: 18th April 2001; Com. 01/17

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年代:2001

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Mendeleev Communications Electronic Version, Issue 5, 2001 1 Interaction of trimethylsilyl isocyanate with xenon difluoride and fluoroxenonium triflate in the presence of alkenes Namig Sh. Pirkuliev,a,b Valery K. Brel,*a Novruz G. Akhmedov,b Nikolai S. Zefirova,b and Peter J. Stangc a Institute of Physiologically Active Compounds, Russian Academy of Sciences, Chernogolovka, 142432 Moscow Region, Russian Federation.Fax: +7 095 913 2113; e-mail: brel@ipac.ac.ru b Department of Chemistry, M. V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation c Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA 10.1070/MC2001v011n05ABEH001492 The title reactions lead to the corresponding â-fluoroisocyanates and â-isocyanatotriflates with the formation of the intermediates FXeNCO and OCNXeOSO2CF3.Xenon difluoride and its derivatives have been used in organic synthesis for fluorination,1 oxidative decarboxylation,2 fluorodeiodination, 3 generation of nitrenes,4 mono-2 and biradicals5 and intermolecular rearrangements,6 as well as for the oxidation of organoelement compounds. The last direction is of great interest since it opens up possibilities for the synthesis of novel xenon compounds.In particular, the cleavage reactions of the Si–C, Si–Cl and Si–N bonds with XeF2 were studied in detail.1(a),7 These reactions are assumed to occur through the formation of intermediates with Xe–N and Xe–C bonds.7 We studied the interaction of trimethylsilyl isocyanate with XeF2 and FXeOSO2CF3 in the presence of unsaturated compounds.The initial fluoroxenonium triflate as a solution in CH2Cl2 was obtained from xenon difluoride and triflic acid (or trimethylsilyl triflate) in accordance with a well-known procedure. 8 The subsequent addition of trimethylsilyl isocyanate to the resulting solution afforded a solution of OCNXeOSO2CF3 1. If at the first step XeF2 was treated with trimethylsilyl isocyanate, highly reactive intermediate FXeNCO 2 was generated.Intermediates 1 and 2 were obtained at –40 to –30 °C as clear solutions in CH2Cl2. Our attempts to isolate intermediates 1 and 2 resulted in their fast decomposition at –20 °C with the formation of, presumably, Xe, CO and N2. The formation of a homogeneous solution during a metathetical reaction at –30 °C indicated the end of the reaction, and the resulting solution of compounds 1 and 2 can be used for further transformation in situ.The conclusions concerning the structure of 1 and 2 were made on the basis of published data1(a),9 and the results of the subsequent chemical transformations, particularly, the reactions with alkenes. The reactions of compounds 1 and 2 with cyclohexene and hex-1-ene were investigated.† The addition of an alkene to a solution of fluoroxenonium isocyanate 2 in CH2Cl2 at –78 °C resulted in rapid darkening of the reaction mixture.However, xenon evolution and concomitant reactions were observed only upon warming the reaction mixture to –30 °C. The products were isolated by column chromatography on silica gel. The ratio of the regioisomers in the reaction mixture and their structure were determined by NMR spectroscopy.In general, â- fluoroisocyanate 3b–5b and â-isocyanotriflate 3a–5a were relatively unstable and slowly decomposed in storage at room temperature. The reactions of isocyanatoxenonium triflate 1 and fluoroxenonium isocyanate 2 with cyclohexene lead to only product 3. The cis configuration of 3 was established by the vicinal H–H and H–F couplings in the 1H NMR spectra.The sum of JHH for H1 and H2 is 13–14 Hz, which is typical of cis substituted cyclohexanes. 10 The reactions of xenonium compounds 1 and 2 with hex- 1-ene resulted in the mixture of products 4 and 5 with domination of regioisomers 4. Each of the regioisomers was isolated and identified by 1H and 19F NMR. The 19F NMR spectrum of regioisomer 4b has the F signal as a doublet of triplets (d 220.7 ppm) with a geminal proton coupling of 47 Hz and a vicinal coupling of JHF = 23 Hz, while regioisomer 5b exhibited an analogous signal as multiplets with a chemical shift of 183 ppm.[FXeNCO] XeF2 [CF3SO2OXeNCO] Me3SiNCO i, CF3SO2OH or CF3SO2OSiMe3 ii, Me3SiNCO 1 2 † General procedure for the interaction of OCNXeOSO2CF3 1 with alkenes: TMSNCO (5.52 mmol) was added to a suspension of FXeOTf8 (4.72 mmol) in methylene chloride (20 ml) at –78 °C with stirring.The reaction mixture was then stirred at –40 °C for 1 h until formation of a colourless solution. The solution was cooled down to –78 °C, and a solution of an appropriate alkene (8 mmol) in methylene chloride (5 ml) was added.The reaction mixture was heated to 10 °C, washed with 30 ml of ice water, extracted with CH2Cl2, dried with Na2SO4, and concentrated in a vacuum at 10 °C. Products 3a–5a were separated by column chromatography on silica gel with 2:1 petroleum ether–diethyl ether as an eluent. cis-1-Trifyloxy-2-isocyanatocyclohexane 3a: oil, yield 53%. 1H NMR (CDCl3) d: 1.2–2.3 (m, 8H, 4CH2), 4.4–4.7 [m, 2H, CH(OTf)CHNCO]. 19F NMR (CDCl3) d: –74.9 (CF3SO3). 1-Trifyloxy-2-isocyanatohexane 4a: unstable oil, yield 45%. 1H NMR (CDCl3) d: 0.9–1.8 (m, 9H, Bu), 4.1–4.7 [m, 3H, CH(NCO)CH2OTf]. 19F NMR (CDCl3) d: –73.9 (CF3SO3). 1-Isocyanato-2-trifyloxyhexane 5a: unstable oil, yield 11%. 1H NMR (CDCl3) d: 0.9–1.9 (m, 9H, Bu), 4.2–4.9 [m, 3H, CH(OTf)CH2NCO]. 19F NMR (CDCl3) d: –74.7 (CF3SO3). General procedure for reactions of FXeNCO 2 with alkenes: TMSNCO (5.52 mmol) was added to a suspension of XeF2 (4.72 mmol) in dichloromethane (20 ml) at –78 °C with stirring.The reaction mixture was then stirred at –40 °C for 1 h. The resulting solution was cooled down to –78 °C, and a solution of an appropriate alkene (8 mmol) in CH2Cl2 (5 ml) was added. The mixture was allowed to warm to 10 °C with stirring.When the evolution of xenon gas ceased (0.5–1 h), the mixture was poured into solution of ice water, then extracted three times with CH2Cl2, dried (MgSO4), and concentrated in a vacuum at 10 °C. Products 3b–5b were isolated by column chromatography on silica gel with 2:1 petroleum ether–diethyl ether as an eluent. cis-1-Fluoro-2-isocyanatocyclohexane 3b: oil, yield 47%. 1H NMR (CDCl3) d: 1.4–2.1 (m, 8H, 4CH2), 4.54 (m, 1H, CHNCO), 4.82 (dddd, 1H, CHF, 1JHF 48 Hz, 2JHH 8, 2.5 and 2.5 Hz). 19F NMR (CDCl3) d: –74.6 (CF3SO3), –193.4 (CHF). 1-Fluoro-2-isocyanatohexane 4b: unstable oil, yield 51%. 1H NMR (CDCl3) d: 1.2–2.1 (m, 9H, Bu), 4.2–4.8 [m, 3H, CH(NCO)CH2F]. 19F NMR (CDCl3) d: –74.8 (CF3SO3), –220.7 (dt, CH2F, 1JHF 47 Hz, 2JHF 47 Hz, 2JHF 23 Hz). 1-Isocyanato-2-fluorohexane 5b: unstable oil, yield 15%. 1H NMR (CDCl3) d: 1.0–2.1 (m, 9H, Bu), 4.2–4.8 (m, 3H, CHFCH2NCO). 19F NMR (CDCl3) d: –73.5 (CF3SO3), –183 (CHF). NCO Y YXeNCO BuCH CH2 Y NCO 4 1, 2 3 BuCH CH2 NCO Y 5 a Y = OSO2CF3 b Y = FMendeleev Communications Electronic Version, Issue 5, 2001 2 In the light of these observations, we can suggest a mechanism1( a) that involves the initial electrophilic addition of the xenonium ion to the double bond leading to an organoxenonium intermediate.At the second step, nucleophilic substitution of Xe with the neighbouring fluorine or triflate anion occurs. This is an SN2 type process, which is analogous to the reactions of iodine(III) with olefins.11 Thus, we found that the reactions of xenon difluoride and fluoroxenonium triflate with trimethylsilylisocyanate in the presence of alkenes lead to the corresponding â-fluoroisocyanates and â-isocyanatotriflates. This fact indirectly confirms the formation of the intermediates FXeNCO and OCNXeOSO2CF3.We are grateful to NIH, FIRCA (2R03 TW00437) for financial support. References 1 (a) V. K. Brel, N. Sh. Pirkuliev and N.S. Zefirov, Usp. Khim., 2001, 70, 262 (Russ. Chem. Rev., 2001, 70, 231); (b) New Fluorinating Agents in Organic Synthesis, eds. L. German and S. Zemskov, Springer-Verlag, Berlin, 1989. 2 (a) Y. Tanabe, N. Matsuo and N. Ohno, J. Org. Chem., 1988, 53, 4582; (b) V. K. Brel, A. S. Koz’min, I. V. Martynov, V. I. Uvarov, N. S. Zefirov, V. V. Zhdankin and P. J. Stang, Tetrahedron Lett., 1990, 31, 4789; (c) I.V. Martynov, V. K. Brel, V. I. Uvarov, I. A. Pomutkin, N. N. Aleinikov and S. A. Kashtanov, Izv. Akad. Nauk SSSR, Ser. Khim., 1988, 466 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1988, 37, 386). 3 E. W. Della and N. J. Head, J. Org. Chem., 1992, 57, 778. 4 S. V. Kovalenko, V. K. Brel, N. S. Zefirov and P. J. Stang, Mendeleev Commun., 1998, 68. 5 V.K. Brel, V. I. Uvarov, N. S. Zefirov, P. J. Stang and R. Caple. J. Org. Chem., 1993, 58, 6922. 6 (a) T. B. Patrick and L. Zhang, Tetrahedron Lett., 1997, 38, 8925; (b) T. B. Patrick, L. Zhang and Q. Li, J. Fluorine Chem., 2000, 102, 11; (c) T. B. Patrick and S. Qian, Org. Lett., 2000, 2, 3359. 7 (a) J. A. Gibson, R. K. Marat and A. F. Janzen, Can. J. Chem., 1975, 53, 3044; (b) M. Patersson, J. Khriachtchev, E. Isoniemi and M. Rasanen, J. Am. Chem. Soc., 1998, 120, 7979. 8 (a) M. Wechsberg, P. A. Bulliner, F. O. Sladky, R. Mews and N. Bartlett, Inorg. Chem., 1972, 11, 3063; (b) T. M. Kasumov, N. Sh. Pirguliyev, V. K. Brel, Y. K. Grishin, N. S. Zefirov and P. J. Stang, Tetrahedron, 1997, 53, 13139. 9 A. Schulz and T. M. Klapotke, Inorg. Chem., 1997, 36, 1929. 10 N. S. Zefirov, V. V. Samoshin, O. A. Subbotin, I. V. Baranenkov and S. Wolf, Tetrahedron, 1978, 34, 2553. 11 N. S. Zefirov, V. V. Zhdankin and A. S. Kozmin, Tetrahedron Lett., 1986, 27, 1845. Received: 3rd July 2001; Com. 01/1818

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年代:2001

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Mendeleev Communications Electronic Version, Issue 5, 2001 1 Xenon difluoride–trimethylsilyl isocyanate–triflic acid as a new system for the amination of aromatic compounds Namig Sh. Pirkuliev,a,b Valery K. Brel,*a Novruz G. Akhmedov,b Nikolai S. Zefirova,b and Peter J. Stangc a Institute of Physiologically Active Compounds, Russian Academy of Sciences, Chernogolovka, 142432 Moscow region, Russian Federation.Fax: +7 095 913 2113; e-mail: brel@ipac.ac.ru b Department of Chemistry, M. V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation c Department of Chemistry, Unversity of Utah, Salt Lake City, UT 84112, USA 10.1070/MC2001v011n05ABEH001514 In the title system, OCNXeOSO2CF3 is formed, which readily oxidises iodobenzene to [PhI+–NCO –OTf]. The direct amination of aromatic substrates is possible with the use of XeF2–Me3SiNCO–CF3SO3H. Since the discovery of the first xenon compounds by Bartlett1 in 1962, a large number of xenon derivatives with Xe–F, Xe–Cl, Xe–O, Xe–N, Xe–C and Xe–N bonds were prepared.2 The methodology of Xe–element bond formation is based on the rupture of M–element bonds (where M = Bi, Sb or Si) with the aid of xenon fluorides.The Si–element fission bond is most promising and interesting for obtaining compounds with Xe–N bonds.2(a),3 Thus, D. D. DesMarteau3(c) used this approach for the preparation of the relatively stable compound FXe(NSO2F)2. Recently, theoretical computations and product analysis of the reaction of XeF2 with NaN3 and NaOCN indicated the intermediate formation of FXeN3 and FXeNCO.4 Previously, we found that the reaction of trimethylsilyl isocyanate with XeF2 or FXeOSO2CF3 in the presence of olefins proceeds through the formation of FXeNCO and OCNXeOSO2CF3 intermediates, which are easily added at the double bond of an olefin.In a continuation of this work, we studied the interaction of trimethylsilyl isocyanate with XeF2 or FXeOSO2CF3 in the presence of aromatic compounds.It is well known that, in this case, the reaction path strongly depends on the order in which the reactants were added. In particular, if finely dispersed XeF2 in CH2Cl2 was transformed into FXeOTf5 and the latter was treated with trimethylsilyl isocyanate and then with iodobenzene, mixed iodonium sulfonate 36 was obtained.† When trimethylsilyl isocyanate was added to a XeF2 solution in CH2Cl2 and the resulting mixture was subsequently treated with triflic acid and iodobenzene, phenyl(p-iodophenyl)iodonium triflate 4 and iodoanilines 5, 6 (as a mixture of ortho and para isomers) were isolated from the reaction mixture as a final products.‡ Note that in this case the formation of compound 3 was not detected.Consequently, the XeF2–Me3SiNCO–CF3SO3H system acts as an aminating reagent for aromatic compounds.7,8 Moreover, we found that with the use of other aromatic compounds such as benzene, toluene, chlorobenzene and o-xylene instead of iodobenzene the formation of amines 7 and 8 takes place (Table 1).† Typical procedure for the preparation of [PhI+NCO –OTf]. 5.52 mmol of Me3SiNCO was added to a stirred suspension of 4.72 mmol of CF3SO2OXeF5 in 20 ml of CH2Cl2 at –78 °C under argon.The mixture was allowed to warm up to –40 °C and stirred until the formation of a yellow homogeneous solution. The solution was cooled to –78 °C; then, 4.72 mmol of iodobenzene was added using a syringe. The mixture was allowed to warm to –5 °C and stirred for ~2 h. The precipitate was filtered off under argon, washed with cold diethyl ether and dried in vacuo to yield the material of >98% purity.The analytically pure compound can be obtained by recrystallization from CH2Cl2–Et2O. [Isocyanato(trifyloxy)-l3-iodo]benzene 3. 1HNMR (CD3CN) d: 8.3–7.5 (m). 13C NMR (CD3CN) d: 172.5 (CO), 136.6, 135.0, 132.9, 122.7 (Ph), 120.8. 19F NMR (CD3CN) d: –78.6 (CF3). IR (CCl4, n/cm–1): 2510, 1625 (NCO), 1258, 1178, 1023 (OTf).XeF2 + HOTf FXeOTf [Xe(OTf)(NCO)] TfO– PhI+–NCO CH2Cl2 Me3SiNCO – TMSF PhI – Xe 1 2 3 Scheme 1 ‡ Reaction of iodobenzene with XeF2–Me3SiNCO–HOTf. XeF2 (4.72 mmol) was dissolved in dry CH2Cl2 (15 ml)10 under argon; then, Me3SiNCO (5.1 mmol) was added. Triflic acid (10 mmol) was slowly added dropwise at –78 °C to the solution of FXeNCO in dry CH2Cl2 and then the mixture was stirred at –30 °C for ~1 h.Then, a large excess of PhI (12 mmol) was added to the suspension at –78 °C, and the mixture was stirred until no more gas (Xe) was evolved (see Table 1 for total reaction time). The solution was heated to room temperature and poured into a dilute solution of HCl with ice. An excess of iodobenzene and phenyl(p-iodophenyl)- iodonium triflate 4 were extracted with dichloromethane (3×15 ml).The volatile materials were then removed under reduced pressure to give an oily residue, which was dissolved in dry diethyl ether. The mixture was vigorously shaken for several minutes to precipitate slightly coloured crystals. Analytically pure samples were obtained by recrystallization from CH2Cl2–Et2O. The aqueous layer was neutralised with a 30% sodium hydroxide solution to pH ~13.The mixture of o- and p-iodoanilines 5, 6 was then extracted with dichloromethane and dried with MgSO4. Products were isolated after evaporating the solvent. Isomeric mixtures were analysed by 1H NMR. Phenyl(p-iodophenyl)iodonium triflate 4: yield 44%, mp 146–147 °C (lit.,11 144–148 °C). 1H NMR (CDCl3) d: 7.48 (m, 2H, Ph), 7.64 (m, 1H, Ph), 7.80 (m, 4H, C6H4), 8.10 (m, 2H, Ph). 19F NMR (CDCl3) d: –78.4 (CF3SO3). I I CF3SO2O I NH2 I H2N R NH2 R R' R' H2N 4 5 6 7a–d 8a–d i, Me3SiNCO ii, CF3SO2OH IC6H5 XeF2 a R = R' = H b R = Cl, R' = H c R = Me, R' = H d R = R' = Me Scheme 2 RR' C6H4 Table 1 Amination of aromatic compounds with XeF2–Me3SiNCO–CF3SO3H. Substrate Reaction time/h Yielda (%) aIsolated yields based on XeF2 used.orthoisomer paraisomer Yielda of 4 (%) C6H6 3 45 — MeC6H5 3 40 54 46 IC6H5 4 38 50 44 44 ClC6H5 6 35 45 48 o-Xylene 3 43 — —Mendeleev Communications Electronic Version, Issue 5, 2001 2 These results indicate that the XeF2–Me3SiNCO–CF3SO3H system makes it possible to perform conveniently electrophilic one-step amination of aromatic compounds with the formation of anilines in moderate yields.Highly deactivated aromatics slowly react under these conditions to form anilines in low yields. Thus, with nitrobenzene, the yields of nitroanilines were lower than 5%. In this case, the deactivation of a benzene ring probably occurs not only owing to the nitro group but also due to the further deactivation of the ring by the protonation of the nitro group in a triflic acid medium.9 It is believed that the amination of aromatic compounds§ involves the formation of the reactive triflate [H2N+=C=O –OTf] at the stage of the interaction of FXeNCO with triflic acid.This explanation was additionally supported by studies of the reactions with Me3SiOTf in place of HOTf. In this case, the [H2N+=C=O –OTf] species was not formed, apparently, due to the absence of hydrogen ions.Most likely, the formation of OCNXeOSO2CF3 occurs, and hence the reaction with iodobenzene leads to the formation of only iodonium sulfonate 3 (Scheme 1). Thus, we found that in the case of the XeF2–CF3SO3H– Me3SiNCO system the formation of OCNXeOSO2CF3 takes place, which readily oxidises iodobenzene to [PhI+–NCO –OTf].The direct amination of aromatic substrates with reasonable yields is possible with the use of XeF2–Me3SiNCO–CF3SO3H. We are grateful to NIH and FIRCA (2RO3TW000437) for financial support. References 1 N. Bartlett, Proc. Chem. Soc., 1962, 218. 2 (a) V. K. Brel, N. Sh. Pirkuliev and N. S. Zefirov, Usp. Khim., 2001, 70, 262 (Russ. Chem. Rev., 2001, 70, 231); (b) New Fluorinating Agents in Organic Synthesis, eds. L.German and S. Zemskov, Springer–Verlag, Berlin, 1989. 3 (a) D. D. DesMarteau, J. Am. Chem. Soc., 1978, 100, 6270; (b) D. D. DesMarteau, R. D. LeBlond, S. F. Hossain and D. Nothe, J. Am. Chem. Soc., 1981, 103, 7734; (c) J. F. Sawyer, G. J. Schrobilgen and S. J. Sutherland, J. Chem. Soc., Chem. Commun., 1982, 210; (d) A. A. A. Emara and G.J. Schrobilgen, Inorg. Chem., 1992, 31, 1323. 4 A. Schulz and T. M. Klapotke, Inorg. Chem., 1997, 36, 1929. 5 (a) T. M. Kasumov, N. Sh. Pirguliyev, V. K. Brel, Y. K. Grishin, N. S. Zefirov and P. J. Stang, Tetrahedron, 1997, 53, 13139; (b) M.Wechsberg, P. A. Bulliner, F. O. Sladky, R. Mews and N. Bartlett, Inorg. Chem., 1972, 11, 3063. 6 V. V. Zhdankin, C. M. Critell, P. J. Stang and N.S. Zefirov, Tetrahedron Lett., 1990, 31, 4821. 7 (a) R. Schroter and E. Muller, Houben–Weyl, Methoden der Organischen Chemie, Thieme Verlag, Stuttgart, 1957, vol. XI/1, pp. 341–488; (b) P. Kovacic, Friedel–Crafts and Related Reactions, Interscience Publishers, New York, 1964, vol. II/2, p. 1493; (c) T. Sheradsky, The Chemistry of Amino, Nitroso and Nitro Compounds and Their Derivatives, John Wiley, New York, 1982, part 1, pp. 395–416. 8 (a) C. Graebe, Ber. Dtsch. Chem. Ges., 1901, 34, 1778; (b) G. F. C. Jaubert and R. Hebd, Seances Acad. Sci., 1901, 132, 841; (c) P. Kovacic, R. L. Russel and R. B. Bennett, J. Am. Chem. Soc., 1964, 86, 1588; (d) P. Kovacic and R. B. Bennett, J. Am. Chem. Soc., 1961, 83, 221; (e) G. A. Olah and T. D. Ernst, J. Org. Chem., 1989, 54, 1203. 9 G. A. Olah, G. K. S. Prakash and J. Sommer, Superacids, John Wiley, New York, 1985. 10 D. D. Perrin, W. L. F. Armaredo and D. R. Perrin, Purification of Laboratory Chemicals (2nd edition), Pergamon Press, New York, 1980. 11 T. Kitamura, J.-I. Matsuyuki, K. Nagata, R. Furuki and H. Taniguchi, Synthesis, 1992, 945. § General procedure for the amination of aromatic compounds. The reactions with other aromatics were carried out as described above for the interaction of iodobenzene with XeF2–Me3SiNCO–HOTf system. Isomeric arylamines 7 and 8 were isolated in moderate yields (Table 1). Physico-chemical constants and spectral properties of 7 and 8 are in agreement with the published data. Received: 10th August 2001; Com. 01/1840

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Mendeleev Communications Electronic Version, Issue 5, 2001 1 The effect of pressure on the diastereoselectivity of the reaction of prenal with monoalkyl ylidenemalonates catalysed by homochiral secondary amines Edward P. Serebryakov,* Albert G. Nigmatov and Mikhail A. Shcherbakov N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation. Fax: +7 095 135 5328; e-mail: ser@cacr.ioc.ac.ru 10.1070/MC2001v011n05ABEH001502 The dienamine-mediated formation of 6-substituted cyclohexa-1,3-dienes from the title reactants catalysed by either (S)- or (R)- prolinol at 8 kbar proceeds with different net enantioselectivities depending on the structure of RCH=C(CO2H)CO2Alk to give a product with the same configuration as that obtained at atmospheric pressure (if R = Me2C=CH) or with a configuration opposite to the latter (if R = Ph); by contrast, with both dienophiles the sense of enantioselectivity does not change with pressure when (S)-¥á,¥á-diphenyl-2-pyrrolidinemethanol is used as the catalyst.Recently, the catalytic synthesis of optically active cyclohexa- 1,3-dienes from ¥â-branched ¥á,¥â-alkenals and various monoalkyl ylidenemalonates was described,1 and factors affecting the apparent (net) enantioselectivity of this process were studied.2 The reaction mechanism (Scheme 1)1.3 involves the transient formation of a dienamine followed by two consecutive, inherently diastereoselective reactions.One of them, intermolecular [4+2] cycloaddition, is strongly accelerated by pressure,4 whereas the other is believed to proceed via a six-membered transition state,5 which can also be affected by pressure.Since the net enantioselectivity of cyclohexadiene formation diminishes with temperature,1,2 we used a high-pressure technique as an alternative to heating for accelerating the process without damaging the ee of its products. Scheme 2 demonstrates two examples examined.The experiments were performed in dry toluene at 20¡¾2 ¡ÆC both under normal pressure (~1 bar) and at 8 kbar.¢Ó Enantiopure (S)-¥á,¥á-diphenyl-2-pyrrolidinemethanol 6, (S)-prolinol 7 and (R)-prolinol ent-7 (0.1 equiv. each) were used as catalysts. The results are shown in Table 1. Table 1 indicates that the application of a high pressure results in diminished chemical yields of target products 3 and 5.However, with all three catalysts, prolonged exposures of process (2) to high pressure markedly increased the ee of ester 5 (cf. runs 2.2.2.3, 2.5.2.6, 2.8.2.9); this trend can be useful from the preparative standpoint. In process (1), the sense of its net enantioselectivity is not altered by a high pressure. The ee of ester (S)-3 slightly diminishes when catalyst 6 is used, whereas a relatively high increase in ee is observed if this process is catalysed by 7 or ent-7.R2 R1 O A RR* NH R2 R1 NRR* B + H2O B CO2Alk CO2H R3 C R1 R2 R3 AlkO2C O O H NRR* D D R1 R2 R3 CO2Alk E + CO2 + HNRR* (1) (2) (3) Scheme 1 R1 ©ö H ¢Ó Experiments at 1 bar were carried out as described earlier,2 however, dry toluene was used instead of benzene.Acid esters 2 (mp 84 ¡ÆC) and 4 (mp 95 ¡ÆC) were prepared as Z isomers of ~100% geometrical purity (1H and 13C NMR data) according to refs. 2 and 6, respectively. Experiments at 8 kbar were performed using a termostatted Barostat HP unit in 2 ml Teflon ampoules. The ampoules were filled at 0.5 ¡ÆC first with dienophiles 2 or 4 (0.4.0.5 mmol) in 0.5 ml of PhMe and then with solutions of enal 1 (0.4.0.5 mmol) and a chiral amine (0.04.0.05 mmol) in toluene to the total volume of 2 ml.The time span between the application of the pressure and the attainment of a steady state was ~10 min. At both pressures, the work-up of the reaction mixture included its concentration in vacuo, the extraction of an oily residue with pentane, and the fractionation of the pentane-extracted solute by column chromatography (SiO2).The purity of the products was controlled by TLC on Silufol plates (hexane.AcOEt, 6:1; Rf 0.55 for 3 and 0.45 for 5) and by 1H NMR spectroscopy (Bruker AM-300 instrument, in d6-benzene). Enantiomer ratios (er) and the values of ee in scalemic 3 and 5 were determined by correlating the [a]D of a specimen with the ratio of peak areas belonging to R and S antipodes in the 1H NMR spectrum recorded in the presence of (S)- or (R)-BINOL (for details, see refs. 1, 2). For the enantiomers of 3, this correlation was linear in the whole range of ee (from ~0 to ~100%). In the case of 5, this correlation was also linear up to the largest ee attainable at atmospheric pressure (32%); further estimates of ee were made using [a]D alone on the assumption that the linearity still holds.For (S)-5 and (R)-5 with 100% ee, an extrapolation gave |[a]D| = 186¡Æ. All [a]D (measured in benzene at 20¡¾4 ¡ÆC) and the corresponding enantiomer ratios and ee given in Table 1 are the mean values of three significantly close results. Material balances for processes (1) and (2) at both pressures revealed methyl 5-methylhexa-3,5-dienoate (from 2) or ethyl cinnamate (from 4) as main low-molecular-weight by-products (up to 3% at 1 bar and below 1.5% at 8 kbar), and polar polymers (Rf < 0.05), which are insoluble in pentane (up to 35% at normal pressure6 and up to 50% at 8 kbar in the case of dienophile 4).O 1 CO2H CO2Me 2 cat. Me O OMe * 3 Process (1): Process (2): 1 + CO2H CO2Et cat. Me O OEt Ph * 5 N OH Ph Ph H 6 N OH H 7 N OH H ent-7 Scheme 2 4Mendeleev Communications Electronic Version, Issue 5, 2001 2 The application of a high pressure to process (2) led to somewhat puzzling results.First, at 8 kbar, amine 7 catalysed the formation of dextrotatory ester (S)-5, while under atmospheric pressure it favoured the formation of levorotatory (R)-5. As the complement to this reversal, instead of (S)-5, which was obtained at 1 bar using ent-7 as the catalyst, (R)-5 was isolated when a mixture of 1, 4 and ent-7 was exposed to 8 kbar.With both catalysts, the reversal of net enantioselectivity increased at prolonged exposures to a high pressure. Second, while process (1) catalysed by bulky amine 6 at 8 kbar afforded a specimen of (S)-3 with a lower ee than that attained at 1 bar, a specimen of (S)-5, which was isolated when process (2) was catalysed by 6 at 8 kbar, had a higher ee than that of an analogous specimen of (S)-5 obtained at 1 bar.Different patterns of the net enantioselectivity of processes (1) and (2) under high pressure imply that the preferred transition states of their pivotal steps are different. This difference may originate from different diastereofacial selectivities with which each of the two reactive conformations of transient dienamines (e.g., s-cis1-8a,b and s-cis2-8a,b generated from enal 1 and amines 6 or 7) approaches – in both endo and exo modes – the preferred conformations of dienophiles 2 or 4 (F and G, respectively, as determined using the PC MODEL program2) (Figure 1).Note that, by contrast with pressure-assisted asymmetric Diels– Alder reactions of achiral 1,3-dienes with homochiral dienophiles, 4(c) analogous pressure-assisted processes involving conformationally flexible homochiral dienamines and achiral dienophiles rarely occur in high-pressure organic chemistry. We thank Dr. M. I. Struchkova and Mr. A. V. Ignatenko (N. D. Zelinsky Institute of Organic Chemistry, Moscow) for their help in determining the ee of the products by the 1H NMR– chiral solvating agent technique, and to Professor V.M. Zhulin and Dr. I. V. Zavarzin for their kind permission to use their highpressure equipment. This work was supported by the Russian Foundation for Basic Research (grant nos. 96-03-33396 and 99- 03-32992) and by INTAS (grant no. 96-1109). References 1 A. G. Nigmatov and E. P. Serebryakov, Izv. Akad. Nauk, Ser. Khim., 1996, 663 (Russ. Chem. Bull., 1996, 45, 623). 2 E. P. Serebryakov, A. G. Nigmatov, M. A. Shcherbakov and M. I. Struchkova, Izv. Akad. Nauk, Ser. Khim., 1998, 84 (Russ. Chem. Bull., 1998, 47, 82). 3 A. G. Nigmatov and E. P. Serebryakov, Izv. Akad. Nauk SSSR, Ser. Khim., 1991, 1079 (Bull.Acad. Sci. USSR, Div. Chem. Sci., 1991, 40, 961). 4 (a) G. Jenner, in Organic High Pressure Chemistry, ed. W. J. leNoble, Elsevier, Amsterdam, 1988, pp. 143–203; (b) R. van Eldik, T. Asano and W. J. leNoble, Chem. Rev., 1989, 89, 549; (c) G. Jenner, Tetrahedron, 1997, 53, 2669; (d) M. Ciobanu and K. Matsumoto, Liebigs Ann. Chem., 1997, 623; (e) L. F. Tietze, M. Henrich, A. Niklaus and M.Bubak, Chem. Eur. J., 1999, 5, 297. 5 (a) C. Mannich and E. Ganz, Ber., 1922, 55, 3504; (b) N. Campbell and R. S. MacPherson, J. Chem. Soc., Perkin Trans. 1, 1974, 43. 6 A. G. Nigmatov, I. N. Kornilova and E. P. Serebryakov, Izv. Akad. Nauk, Ser. Khim., 1996, 154 (Russ. Chem. Bull., 1996, 45, 144). Table 1 The effect of pressure on the chemical yields and net enantioselectivities of processes (1) and (2) in the presence of amines 6, 7 and ent-7 in dry toluene at 20±2 °C.Run Amine P/bar t/h Yield (%)a aIsolated yield. bMeasured at 20±4 °C in dry benzene (c 1.0). cAt 50 °C, because at 20 °C process (2) is not observed. dFor a specimen with ee ~100%, it was extrapolated1 that |[a]D| = 186°. [a]D b R:S ratio ee (%) Process (1): 1 + 2 ® 3 1.1 6 1.0 360 39 +296° <2:98 > 96 1.2 6 8000 72 27 +238° 10:90 80 1.3 7 1.0 120 52 +53° 41:59 18 1.4 7 8000 96 18 +76° 37:63 26 1.5 ent-7 1.0 120 54 –41° 57:43 14 1.6 ent-7 8000 72 35 –82° 64:36 28 Process (2): 1 + 4 ® 5 2.1a 6 1.0 360 0 — — 2.1b 6 1.0 20c 7c +53° c 34:66 32d 2.2 6 8000 48 5 +71° 31:69 38d 2.3 6 8000 240 6 +167° 5:95 90d 2.4 7 1.0 360 20 –14.5° 54.5:45.5 9d 2.5 7 8000 24 6 +34° 41:59 18d 2.6 7 8000 336 6.5 +60° 36:64 28d 2.7 ent-7 1.0 120 14 +17° 45:55 10d 2.8 ent-7 8000 24 3.5 –12.5° 53:47 14d 2.9 ent-7 8000 168 7 –74° 70:30 40d Me H H N Me H H N s-cis2 s-cis1 X Me Me H H F O OMe HO H G OEt O HO O H H Figure 1 X 6 X = Ph2COH 7 X = CH2OH O Received: 13th July 2001; Com. 01/1828

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Mendeleev Communications Electronic Version, Issue 5, 2001 1 Selectivity of the Lewis acid-induced transformations of polyfunctional compounds containing a 4,6-dialkoxy-7-(arylthio)heptene moiety Dmitrii S. Chekmarev,a Andrei V. Maskaev,a Georgy V. Zatonsky,b Margarita I. Lazareva,b,c Ron Caplec and William A. Smit*b a Higher Chemical College, Russian Academy of Sciences, 125047 Moscow, Russian Federation.Fax: +7 095 200 4204 b N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation. Fax: +7 095 135 5328 c Department of Chemistry, University of Minnesota-Duluth, Duluth, Minnesota 55812, USA 10.1070/MC2001v011n05ABEH001513 The interaction of the title adducts with Lewis acids may proceed as an attack at either â-alkoxy or ä-alkoxy group to the arylthio substituent leading to the formation of substituted cyclohexane or 1,3-diene derivatives, respectively.As was reported earlier, a set of structurally diverse adducts containing a 7-arylthio-4,6-dialkoxyheptene moiety can be readily assembled from four simple precursors with the help of the one-pot protocol that involves three consecutive intermolecular AdE reactions (Scheme 1).1(a)–(d) These compounds can be used as substrates for further reactions.We report here the Lewis acid-induced reactions of the title adducts. It seems reasonable to assume that an initial attack of a Lewis acid could be directed at either â- or ä-alkoxy group of the adducts (Scheme 2). In both cases, the subsequent elimination of an alkoxy group should be facilitated by the nucleophilic assistance of the properly positioned arylthio substituent.Hence, the formation of either the episulfonium ion (ESI) or the thiophanium ion (TPI) as an intermediate is to be expected as an immediate result of the â- or ä-attack, respectively. As found earlier,2(a)–(e) the ESI salts, once formed as transient intermediates, exhibit a rather high reactivity as electrophiles.In structurally related systems, they react readily with a nucleophilic double bond present in the substrate to give cyclic products. Hence, the â-attack should lead to the formation of cyclohexane derivatives as shown in Scheme 2. At the same time, according to published data,3 the TPI salts are stable and unreactive species; therefore, the final outcome of the ä-attack cannot be predicted certainly.Initial experiments were carried out with 2-methyl-4,6-dimethoxy- 7-(p-methylphenylthio)hept-1-ene 1 prepared via the coupling p-TolSCl + methyl vinyl ether + methyl vinyl ether + trimethylmethallylsilane following the general protocol outlined in Scheme 1.† The interaction of this model compound with a Lewis acid may occur via either ä- or â-attack depending on the nature of the employed reagent.Thus, the treatment of individual diastereomers (1a or 1b) or their mixture (1a,b) with 2 equiv. of trimethylsilyl triflate (TMSOTf) in CH2Cl2 at ambient temperature followed by the quenching of the reaction mixture with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) resulted in the formation of a mixture of conjugated dienes (E)-2-methyl-6- methoxy-7-(p-tolylthio)hepta-2,4-diene 2a and (E)-2-methyl- 6-methoxy-7-(p-tolylthio)hepta-1,3-diene 2b in 50% total yield‡ (2a:2b = 7:1, 1H NMR data).The TLC monitoring of this reaction revealed an almost instantaneous conversion of 1a,b (Rf = = 0.5, hexane–ethyl acetate, 5:1) into a highly polar intermediate (Rf < 0.05, hexane–ethyl acetate, 5:1), which was converted into final product 2a,b (Rf = 0.6, hexane–ethyl acetate, 5:1) upon the treatment with DBU.These data suggested that, under the chosen conditions, the reaction of 1a,b occured as an initial attack of TMSOTf at the ä-methoxy group to give an intermediate which was presumably identified as TPI salt 3.§ The latter underwent further ring opening and proton elimination upon the treatment with a base (Scheme 3).We assume that the predominant formation of 2a is due to the isomerization of initially formed isomer 2b, which is thermodinamically less stable. † General procedure for the preparation of the starting adducts was described earlier.1(a),(b). Below are specified the reaction conditions (Lewis acid, solvent, temperature, time, yields and diastereomer ratio). 1a,b: LiClO4, MeNO2, –25 °C, 3 h, 82%, 1:1.4. 6a,b: LiClO4, MeNO2, –25 °C, 20 °C, 10 h, 94%, 1:1.1. 7a,b: LiClO4, MeNO2, –25 °C to 20 °C, 20 h, 93%, 1:1.1. 12: TiCl4, CH2Cl2, –70 °C to 20 °C, 24 h, 65%, single diastereomer. OR1 ArSCl + OR1 Cl ArS AdE-I OR2 Lewis acid AdE-II S Ar OR2 R1O (– MR3) AdE-III MR3 (M = Si, Sn; R = Alkyl) + ArS OR1 OR2 â ä Scheme 1 ‡ Yields refer to the isolated compounds purufied by flash chromatography on SiO2.The identity of all compounds was established by 1H and 13C NMR data and elemental microanalyses. ArS OR1 OR2 â ä L. a. L. a. â-attack (– OR1) ä-attack (– OR2) OR2 ArS ESI AdE R2O SAr B: ? S R1O Ar TPI B: ? Scheme 2Mendeleev Communications Electronic Version, Issue 5, 2001 2 On the other hand, the treatment of 1a with a TMSOTf– Et2AlCl mixture (1:1, 2 equiv.) followed by quenching with DBU afforded 1-methyl-3-(p-tolylthiomethyl)-5-methoxycyclohex- 1-ene 4a in 65% yield.‡ The TLC monitoring of the reaction revealed the initial formation of a highly polar material (Rf < < 0.05, hexane–ethyl acetate, 5:1).To isolate the latter, the reaction mixture formed upon the complete conversion of 1a was poured into absolute CCl4 at –20 °C.An oily precipitate was separated from the supernatant liquid; it was carefully washed with CCl4 and dissolved in CD2Cl2. The presence of impurities did not allow us to carry out the complete analysis of 1H NMR spectra of this sample. However, these NMR data are consistent with the structure of bicyclic TPI salt 5a, as presented in Scheme 3.¶ This compound is a true intermediate in the above transformation of 1a since the treatment of isolated salt 5a with DBU furnished the same product 4a.These data suggest that cyclohexane derivative 4a was formed as a result of a multistep sequence starting with an initial attack of a Lewis acid (TMSOTf–Et2AlCl) at the â-methoxy group followed by a nearly concerted intramolecular cyclization of the transient ESI-like intermediate to give stabilised bicyclic TPI salt 5a [cf.refs. 2(a),(d),(e)], which can be further converted into the final adduct via sulfonium ring opening and proton elimination. The interaction of the diastereomer 1b with Et2AlCl–TMSOTf followed the pattern established for 1a (TLC monitoring) except that bicyclic intermediate 5b is less stable and more reactive than 5a.The conversion of this intermediate into final product 4b (yield 59%) did not require the presence of DBU and proceeded easily upon the treatment of the reaction mixture with aqueous NaHCO3. Adduct 4b‡ differs from product 4a only in the configuration of the methoxy substituent. Hence, it follows that the conversions 1a ® 4a and 1b ® 4b proceed as highly diastereoselective reactions.Finally, we also found that both the preparation of adducts 1a,b (via four-component coupling, cf. Scheme 1) and the cyclizaton to give product 4a,b (82%, a:b = 1:1.4) can be carried out as a one-pot sequence of three intermolecular and one intramolecular AdE reactions as represented in Scheme 3.†† This unprecedented sequence‡‡ resulted in the assemblage of a cyclohexane ring from simple precursors with the formation of three new C–C bonds.§ The intermediacy of 3 was substantiated by the 1H NMR monitoring of the reaction of 1a with TMSOTf (CD2Cl2, 20 °C). After 2 h, the 1HNMR spectrum indicated a nearly complete formation of a new compound, which was tentatively identified as thiophanium salt 3 by the appearance of downfield-shifted signals of the protons of the MeC6H4 fragment (0.3– 0.5 ppm as compared to the respective signals in 1a,b or 2a,b) (vide infra).S Me OMe OMe p-TolS TMSOTf CH2Cl2 20 °C, 15 min S MeO p-Tol Me DBU Me Me OMe p-TolS : Me OMe p-TolS 1a,b (a:b = 1:1.4) 3 (TPI) 2a 2b ä-attack: Me OMe OMe p-TolS: â-attack: Et2AlCl–TMSOTf CH2Cl2 20 °C, 5 h Me S p-Tol OMe ESI 1a H H Me H H Tol-p OMe 5a (TPI) DBU Me OMe STol- p 4a Me OMe OMe p-TolS Me OMe STol- p 4b 1b A one-pot sequence of 1a,b assemblage followed by cyclization into 4a,b: OMe i, ArSCl –78 °C, CH2Cl2 OMe Cl ArS ii, , Et2AlCl OMe –78 °C, 15 min –78 °C, 3 h Me SiMe 3 iii, 1a,b iv, TMSOTf 20 °C, 10 h 5a,b v, DBU 4a,b Scheme 3 ¶ Analysis of 1H NMR spectra of crude salt 5a revealed the presence of only one MeO singlet, the absence of olefinic proton signals, and a downfield shift of signals of the protons of the MeAr fragment typically observed in related sulfonium salts [cf.data in ref. 1(c),(d)].§§ †† Procedure of the one-pot preparation of 4a,b: To a stirred solution of p-TolSCl (0.159 mg, 1 mmol) in CH2Cl2 (20 ml) at –78 °C a solution of methylvinyl ether (0.174 mg, 3 mmol) in CH2Cl2 (2 ml) was added followed by the addition of Et2AlCl (0.363 g, 3 mmol) in toluene (1.08 ml).The mixture was kept at the same temperature for 15 min and then methallylsilane (0.257 g, 2 mmol) was introduced. TLC monitoring revealed that after two more hours at –78 °C the formation of the adduct 1a,b came to the completion. After that the temperature was raised up to 20 °C, TMSOTf (0.066 g, 3 mmol) was added and the reaction mixture was kept at ambient temperature for 5 h.Thereafter, TLC data indicated the complete disappearance of a spot corresponding to adducts 1a,b (Rf = 0.50, hexane–ethyl acetate, 5:1) substituted by a spot of a highly polar compound (Rf < 0.05). Treatment of the reaction mixture with DBU at 20 °C followed by the usual workup furnished cyclic products 4a,b (yield 82%, a:b = 1:1.4).‡ p-TolS OMe OMe R Me Me 6a,b R = H 7a,b R = Me TMSOTf or TMSOTf–Et2AlCl CH2Cl2, 20 °C, 6 h S MeO p-Tol Me Me R 9 R = H 11 R = Me p-TolS OMe R Me Me 8 R = H, 45% (TMSOTf) 91% (TMSOTf–Et2AlCl) 10 R = Me, 70% DBU OMe i, p-TolSCl –78 °C ii, TMSOTf, Me Me –78 °C –78 to 20 °C, 30 h iii, 6a,b iv, TMSOTf 20 °C, 100 h 8 Scheme 4 OMe SiMe3 65%Mendeleev Communications Electronic Version, Issue 5, 2001 3 The protocol outlined in Scheme 1 was also employed for the preparation of adducts 6a,b and 7a,b.† Treatment of 6a,b with TMSOTf (CH2Cl2, 20 °C) resulted in a fast disappearance of the starting material and appearance of a highly polar compound (TLC monitoring data, cf.data for the similar reaction of 1a,b).The subsequent treatment of the reaction mixture with DBU furnished conjugated diene 8 in 45% isolated yield‡ (Scheme 4). This transformation also proceeds via the intermediate formation of thiophanium salt 9. Much to our surprise, the reaction of 6a,b with TMSOTf–Et2AlCl followed the same ä-attack route to give the same diene 8 (91% yield). The presence of an additional methyl susbstituent at the double bond of adduct 7a,b did not affect the reaction course, and diene 10 was formed as the only isolable product regardless of the nature of the Lewis acid used.Dienes 8 can also be obtained in 65% yield using a one-pot procedure, which involves the in situ assemblage of starting adducts 6a,b from the respective precursors followed by treatment of these adducts with an additional amount of the same Lewis acid (TMSOTf) under a slightly more severe conditions (Scheme 4).As was shown earlier, the sequence outlined in Scheme 1 can also be used for the coupling of cyclic vinyl ethers as the alkene components, which resulted in the highly diastereoselective formation of cyclic adducts.2(d) These adducts react with Lewis acids via a ä-attack. Thus, the reaction of adduct 12† with either TMSOTf or TMSOTf–Et2AlCl with the subsequent treatment of the resulting complex with a base gave diene 13 in 70–80% yield (Scheme 5).‡ The intermediacy of TPI salt 14 in this conversion was established by the results of NMR monitored experiment which indicated an almost instantaneous formation of this intermediate as the only observable product upon the treatment of 12 with TMSOTf.§§ The structure of 14 was unambiguously proved by 1H and 13C NMR spectroscopy with the use of 2D protocols (homo- and heteronuclear correlations, NOESY and ROESY).At present it is hardly possible to advance a fully consistent explanation of the observed sensitivity of the reaction outcome to the nature of the substrates and/or reagents.However, above results clearly demonstrate a possibility to control the selectivity of the Lewis acid-induced transformation of the title multifunctional adducts and thus attest to the promise of further studies in this field. This work was supported by the Russian Foundation for Basic Research (grant no. 00-03-3790), the US CRDF Agency (grant no.RC2-2207) and the Donors of the Petroleum Research Fund administered by the American Chemical Society (ACP-PRF grant no. 35453-B1). References 1 (a) M. I. Lazareva, Yu. K. Kryschenko, A. Hayford, M. Lovdahl, R. Caple and W. A. Smit, Tetrahedron Lett., 1998, 39, 1083; (b) M. I. Lazareva, Yu. K. Kryschenko, A. D. Dilman, A. Hayford, R. Caple and W. A. Smit, Izv. Akad. Nauk, Ser.Khim., 1998, 924 (Russ. Chem. Bull., 1998, 47, 895); (c) M. I. Lazareva, Yu. K. Kryschenko, R. Caple, D. Wakefield, A. Hayford, W. A. Smit and A. S. Shashkov, Tetrahedron Lett., 1998, 39, 8787; (d) M. I. Lazareva, Yu. K. Kryschenko, R. Caple, W. A. Smit, K. A. Lyssenko and A. S. Shashkov, Izv. Akad. Nauk, Ser. Khim., 2000, 82 (Russ. Chem. Bull., 2000, 49, 85). 2 (a) M. T. Mustafaeva, W.A. Smit and V. F. Kucherov, Izv. Akad. Nauk SSSR, Ser. Khim., 1973, 1349 (Bull. Acad. Sci. USSR, Div. Chem. Sci., 1973, 22, 1315); (b) C. Liu, K. Kuda, Y. Hashimoto and K. Saigo, J. Org. Chem., 1996, 61, 494; (c) S. R. Harring and T. Livinghouse, J. Org. Chem., 1997, 62, 6388; (d) A. Kamimura, H. Sasatani, T. Hashimoto and N. Ono, J. Org. Chem., 1989, 54, 4998; (e) A. van Oeveran and B.L. Feringa, J. Org. Chem., 1996, 61, 2920. 3 A. C. Knipe, in The Chemistry of Sulfonium Group, eds. C. J. M. Stirling and S. Patai, Wiley, New York, 1981, ch. 14, pp. 313–376. 4 (a) L. F. S. Tietze, Chem. Rev., 1996, 96, 115; (b) T. Hudlicky, Chem. Rev., 1996, 96, 3. ‡‡ It is noteworthy that among more than dozens of various reaction types employed in the one-pot multistep sequences cationic reactions are most typically represented by the intramolecular electrophilic cyclizations.4 OMe STol-p OMe 12 TMSOTf CH2Cl2, 0 °C, 1 h OMe STol-p 13, 73% S OMe Tol-p 1 6 7 8 9 OTf 14 DBU Scheme 5 Received: 8th August 2001; Com. 01/1839 §§Preparation and NMR data of salt 14: To the stirred solution of 12 (0.033 g, 0.3 mmol) in CD2Cl2 (5 ml) at 0 °C TMSOTf (0.041 g, 0.2 mmol) was added. After 30 min, TLC data indicated the complete conversion of 12 into a highly polar compound. The solution was transferred into an NMR tube, and the 1H and 13C NMR spectra were immediately recorded at 20 °C. 1H NMR (500 MHz, CD2Cl2) d: 1.41 (m, Ha at C-3), 1.51 (m, Ha at C-4), 1.63 (m, Ha at C-5), 1.69 (m, He at C-4), 1.91 (m, He at C-2), 1.98 (m, He at C-3), 2.11 (dd, HA at C-7, J1 12.3 Hz, J2 14.0 Hz), 2.19 (m, Ha at C-2), 2.25 and 2.43 (m, 2H at C-9), 2.40 (m, He at C-5), 2.51 (s, 3H, MeAr), 2.92 (dd, HB at C-7, J1 6.0 Hz, J2 14.0 Hz), 3.29 (s, 3H, MeO), 4.06 (dd, Ha at C-1, J1 4.2 Hz, J2 12.5 Hz), 4.23 (m, H at C-8), 4.82 and 5.24 (dd, 2H at C-11, J 10.3 and 17.2 Hz), 5.52 (m, H at C-10), 7.75 and 7.71 (dd, 4HAr). 13C NMR, d: 19.0 (C-4), 21.3 (MeAr), 23.0 (C-2), 24.8 (C-3), 28.3 (C-5), 33.5 (C-9), 40.5 (C-7), 49.0 (MeO), 58.0 (C-8), 70.9 (C-1), 82.0 (C-6), 119.2 (C-11), 131.5 (C-10), 131.8, 133.0, 132.2 and 147.4 (Ar).

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Mendeleev Communications Electronic Version, Issue 5, 2001 1 Metal complex with the enaminoketone derivative of 2-imidazoline nitroxide Pavel A. Petrov,a Sergei V. Fokin,a Galina V. Romanenko,b Yuri G. Shvedenkov,a Vladimir A. Reznikova and Victor I. Ovcharenko*b a Department of Natural Sciences, Novosibirsk State University, 630090 Novosibirsk, Russian Federation b International Tomography Centre, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russian Federation.Fax: +7 3832 33 1399; e-mail: ovchar@tomo.nsc.ru 10.1070/MC2001v011n05ABEH001472 Functional derivatives of iminonitroxides were prepared by introducing a functional group into the side chain of 1-hydroxy-2- methyl-2-imidazoline; a K+ salt and a Cu2+ bischelate with the first enaminoketone derivative of 2-iminonitroxide were synthesised and structurally characterised. Heterospin systems based on metal complexes with 2-imidazoline nitroxides are widely used in molecular magnet design.1 However, the syntheses of nitronyl nitroxides 1 and iminonitroxides 2 containing functional groups R (Scheme 1), which are favourable for metal complex formation, were confined to only one synthetic procedure.This method, which was proposed by Ullman, involves the condensation of dihydroxyamine 3 with aldehydes or their synthetic equivalents and the subsequent oxidation of dihydroxyimidazolidines 4. Iminonitroxides 2 were generated by the reduction of 1.2 In this work, a donor group R (enaminoketone fragment) was introduced at the 2-position of a heterocyclic ring using another approach, the modification of 1-hydroxy-2- methyl-2-imidazoline (5, R = Me).First, we found an effective approach to the synthesis of 5. The process looks like the ‘thermal dehydration’ of 4 to 5 (Scheme 1). It proceeds with a high yield in boiling heptane (or toluene at 100 °C).† We found that the dehydration was not accelerated in the presence of para-toluenesulfonic acid.The conversion of 4 to 5 by thermal dehydration does not proceed in an inert atmosphere. The presence of atmospheric oxygen is indispensable. Thermal dehydration of 4 is a very effective onepot synthesis of 5. This easy route to 5 permits one to use 2,4,4,5,5-pentamethyl- 1-hydroxy-2-imidazoline (5, R = Me) as a starting compound for the syntheses of persistent enaminoketones of 2-imidazoline nitroxide.The reactions of 5 (R = Me) with esters in the presence of lithium diisopropylamide give enaminoketones 6 (Scheme 2). The introduction of the nitrile substituent into enaminoketones 6 (R1 = Ph, CF3) and further oxidation led to relatively persistent nitroxides 7 (MS, m/z: 276 [M+] R1 = CF3; m/z: 284 [M+] R1 = Ph). Nitroxide analogues of 7 with hydrogen substituted for the nitrile group are unstable and quickly decompose in solution.Nitroxide 7 (R1 = CF3) turned out to be the most long-living. However, we converted it every time to potassium salt 8 persistent under normal conditions. Single crystals of potassium salt 8‡ and Cu2+ complex 9§ with nitroxide 7 (R1 = CF3) were obtained, whose structures are shown in Figures 1 and 2, respectively.Synthesis¶ of 9 is actually a logical end of the chain of transformations presented in Scheme 2. NHOH NHOH RCHO N N OH R OH – H2O N N R OH 4 3 5 N N O R O 1 N N R O 2 Scheme 1 Scheme 2 Reagents and conditions: i, LDA, R1CO2Et, Et2O, 0 ºC; ii, NCS, CHCl3, room temperature; iii, NaCN, DMSO, room temperature; iv, PbO2, CHCl3. N N OH 5 N N OH 6 R1 O ii–iv i N N O 7 R1 O CN H H N N O 8 R1 = CF3, M = K R1 O CN 9 R1 = CF3, M = Cu/2 M R1 = CF3, Ph, CO2Et R1 = CF3, Ph † A typical procedure includes the boiling of a suspension of 1 g of 4 in 30–40 ml of heptane for 10–12 h.The precipitate of 1-hydroxy-2- imidazoline 5 was filtered off (85% yield for R = Me, 70% for R = Et and 50% for R = Ph) after recrystallization from hexane–ethyl acetate. 5 (R = Me): mp 104–106 °C. 1H NMR ([2H6]DMSO) d: 1.08 (s, 6H), 1.09 (s, 6H, 4,5-Me2), 1.93 (s, 3H, 2-Me), 8.08 (br. s, OH). 13C NMR ([2H6]DMSO) d: 13.5 (2-Me), 18.6, 23.4 (4,5-Me2), 65.1, 69.8 (C-4, C-5), 162.1 (C-2). IR (KBr, n/cm–1): 3160, 2900–2600, 1616. Found (%): C, 61.5; H, 10.5; N, 17.9. Calc. for C8H16N2O (%): C, 61.5; H, 10.3; N, 17.9. 5 (R = Et): mp 121–123 °C. 1HNMR (CD3OD) d: 1.15 (t, 3H, CH2Me), 1.21 (s, 6H), 1.24 (s, 6H, 4,5-Me2), 2.45 (q, 2H, CH2Me).IR (KBr, n/cm–1): 3110, 2900–2600, 1613. Found (%): C, 62.9; H, 11.1; N, 16.3. Calc. for C9H18N2O (%): C, 63.5; H, 10.7; N, 16.5. 5 (R = Ph): mp 190–191 °C. 1H NMR (CDCl3) d: 1.36 (s, 6H), 1.43 (s, 6H, 4,5-Me2), 7.25, 7.49 (2m, 5H, Ph), 8.33 (br. s, 1H, OH). IR (KBr, n/cm–1): 3110, 2900–2600, 1611, 1591, 1573.Found (%): C, 71.3; H, 8.2; N, 12.6. Calc. for C13H18N2O (%): C, 71.5; H, 8.3; N, 12.8. Hydroxylamine precursors of 7 (R1 = Ph): mp 213–214 °C. 1H NMR ([2H6]DMSO–CD3COCD3) d: 1.18 (s, 6H), 1.29 (s, 6H, 4,5-Me2), 7.39– 7.71 (m, 5H, Ph), 9.6 (br. s, 1H, NH), 10.1 (s, 1H, OH). 13C NMR (CD3OD) d: 18.5, 23.1 (4,5-Me2), 62.6 (C-4), 71.6 (C-5), 121.7 (CºN), 128.7, 128.9, 131.6, 141.5 (Ph), 166.3 (C-2), 194.0 (C=O).IR (KBr, n/cm–1): 3200–2800, 2209 (CºN), 1600, 1577, 1534. Found (%): C, 67.3; H, 6.8; N, 14.6. Calc. for C16H19N3O2 (%): C, 67.4; H, 6.7; N, 14.7. (R1 = CF3): mp 189–191 °C. 1HNMR ([2H6]DMSO) d: 1.11 (s, 6H), 1.21 (s, 6H, 4,5-Me2), 9.30 (s, NH), 10.4 (s, OH). 13C NMR ([2H6]DMSO) d: 18.3, 22.2 (4,5-Me2), 61.9 (C-4), 63.6 (=C–CN), 70.3 (C-5), 115.8 (CºN), 117.2 (q, CF3, JC–F 291 Hz), 162.8 (C-2), 173.8 (q, C=O, JC–F 32 Hz).IR (KBr, n/cm–1): 3400–3200, 2218 (CºN), 1620, 1547. Found (%): C, 47.7; H, 4.5; N, 14.8. Calc. for C11H14N3O2F3 (%): C 47.7; H, 5.1; N, 15.2.Mendeleev Communications Electronic Version, Issue 5, 2001 2 The structure of 8 is ionic. The distances between the paramagnetic centres in 8 are at least 6.71 A, leading to constant meff (1.68 B.M.) in the temperature range from 300 to 10 K.In complex 9, the distorted octahedral environment of the central atom is formed by the O and N atoms of the two deprotonated enaminoketone ligands and by the N atoms of acetonitrile, and the nitrile group of the neighbouring bis-chelate molecule, leading to formation of polymer chains.The temperature dependence of the magnetic susceptibility of 9 is presented in Figure 3. It is adequately approximated by a cluster model with the parameters g = 2.0, J = 90 cm.1 and nJ' = .0.3 cm.1. The J value is the highest positive value of the intramolecular exchange interaction energy among the known copper bis-chelates with stable nitroxides. This value points to the presence of highly effective exchange clusters inside the bis-chelate fragments.Thus, a convenient route to a series of 4,4,5,5-tetramethyl-1- hydroxy-2R-2-imidazolines (5, R = Me, Et, Ph) has been found. Derivative 5 (R = Me) may be used as a substrate for syntheses of persistent spin-labeled enaminoketones (7, R1 = CF3, Ph). The first metal complex with the enaminoketone derivative of 2-iminonitroxide 9 has been isolated.A transition from metal complexes with spin-labeled 3-imidazoline enaminoketones, characterised by intramolecular exchange interaction energies of about 5.15 cm.1, to the complex with 2-imidazoline analogue allowed us to achieve noticeably higher intramolecular exchange interaction energies between the unpaired electrons of paramagnetic centres (90 cm.1).Studies are currently under way to synthesise other metal complexes with the enaminoketone derivatives of 2-imidazoline nitroxide and to investigate their structure and magnetic properties. This work was supported by CRDF (grant REC-008), Russian Foundation for Basic Research (grant nos. 00-03-32987 and 00-03-04006) and the ¡®Integration¡� Foundation. ¢Ô Crystal data for 8: C11H12F3KN3O2, M = 314.34, monoclinic, a = = 11.068(2) A, b = 9.203(2) A, c = 14.177(3) A, b = 92.19(3)¡Æ, V = = 1443.0(5) A3, T = 293 K, space group P21/c (no. 14), Z = 4, dcalc = = 1.447 g cm.3, m(MoK¥á) = 0.405 mm.1. 2194 Ihk(2012 unique Ihkl, Rint = 0.1104) were measured on a Bruker AXS P4 four-circle automatic diffractometer (lMoK¥á, graphite monochromator, q/2q-scan, 2.64 < q < < 24.98¡Æ).The structure was solved using the SIR97 program and refined by the full-matrix least-squares technique in an anisotropic approximation for all non-hydrogen atoms. All hydrogen atoms were located in a difference Fourier map and then refined in an isotropic approximation. The final R indexes are: R1 = 0.0542, wR2 = 0.1006 for 2012 unique Ihkl > 2s(I), GOOF = 0.664.¡× Crystal data for 9: C24H27CuF6N7O4, M = 655.07, orthorhombic, a = = 14.045(2) A, b = 12.342(2) A, c = 17.259(3) A, V = 2991.7(8) A3, T = = 293 K, space group Pca21 (no. 29), Z = 4, dcalc = 1.454 g cm.3, m(MoK¥á) = 0.809 mm.1. 2723 Ihkl (2723 unique Ihkl) were measured on a Bruker AXS P4 four-circle automated diffractometer (lMoK¥á, graphite monochromator, q/2q-scan, 2.36 < q < 24.99¡Æ, empirical absorption correction). The structure was solved by the SIR97 program and refined by the full-matrix least-square technique in an anisotropic approximation for all non-hydrogen atoms.Positions of all hydrogen atoms were located in a difference Fourier map and than refined in an isotropic approximation. The final R indexes for 406 refined parameters are: R1 = 0.0576, wR2 = = 0.1427 for Ihkl > 2s(I), GOOF = 1.024.All calculations were carried out using the SHELX97 program. Atomic coordinates, bond lengths, bond angles and thermal parameters have been deposited at the Cambridge Crystallographic Data Centre (CCDC). For details, see ¡®Notice to Authors¡�, Mendeleev Commun., Issue 1, 2001. Any request to the CCDC for data should quote the full literature citation and the reference number 1135/98.¢Ò For the synthesis of 8, a solution of KOH (4.0 mmol) in MeOH (5 ml) was added to the solution of 7 (R1 = CF3) (1 g, 3.6 mmol) in ethyl acetate (100 ml) with stirring. Salt 8 was precipitated from the reaction mixture by adding toluene (50% yield). Single crystals were grown by slow diffusion of benzene into an ethyl acetate solution of 8.To prepare 9, a mixture of Cu(NO3)2(H2O)3 (39 mg, 0.16 mmol) and 8 (100 mg, 0.32 mmol) was dissolved in 10 ml of dry acetonitrile, and the solution was allowed to stand at .10 ¡ÆC. After 2 days, the KNO3 precipitate was filtered off; after one more day, dark red crystals of the complex were isolated (yield 45%). 8: mp 257.262 ¡ÆC (decomp.).IR (KBr, n/cm.1): 2190 (C��N), 1603, 1553. Found (%): C, 41.8; H, 3.9; N, 13.1. Calc. for C11H12N3O2F3K (%): C, 42.0; C, 3.9; N, 13.4. 9: mp 176.179 ¡ÆC (decomp.). IR (KBr, n/cm.1): 2220 (C��N), 1588, 1523. Found (%): C, 43.6; C, 4.0; N, 14.8. Calc. for C24H27N7O4F6Cu (%): C, 44.0; H, 4.2; N, 15.0. Figure 1 Molecular structure of 8 with displacement ellipsoids drawn at a 35% probability level (hydrogen atoms omitted for clarity).Selected distances (A) and angles (¡Æ): K.O(11a) 2.688(4), K.O(1) 2.719(4), K.N(2a) 2.821(7), K.N(1) 2.854(5), O(1).C(1) 1.255(7), C(1).C(2) 1.343(7), C(2). C(21) 1.407(9), C(2).C(3) 1.422(7), C(21).N(2) 1.172(8), O(11).N(11) 1.281(5), C(3).N(1) 1.287(6); O(1).K.N(1) 62.78(13), C(1).O(1).K 120.9(4), O(1).C(1).C(2) 126.9(6), C(1).C(2).C(3) 121.6(6), N(2).C(21).C(2) 177.5(8), O(11).N(11).C(3) 126.4(5), O(11).N(11).C(4) 123.4(4), C(3).N(11).C(4) 109.8(5), N(1).C(3).C(2) 127.6(5), C(3).N(1).K 124.9(4). O(11a) C(52) C(51) C(41) C(42) C(4) N(11) N(1) K N(2a) C(3) O(11) C(2) O(1) C(1) C(11) F(3) F(1) F(2) Figure 2 Molecular structure of 9 with displacement ellipsoids drawn at a 35% probability level (hydrogen atoms omitted for clarity). Selected distances (A) and angles (¡Æ): Cu.O(2) 1.953(7), Cu.O(1) 1.963(6), Cu.N(1) 2.024(6), Cu.N(2) 2.033(6), Cu.N(11a) 2.299(9), Cu.N(1a) 2.774(14), O(1).C(1) 1.290(10), C(1).C(2) 1.368(11), C(2).C(3) 1.437(11), C(2).C(21) 1.441(12), C(21).N(111) 1.142(11), C(3).N(1) 1.266(10), N(11). O(11) 1.264(10), O(2).C(6) 1.263(11), C(6).C(7) 1.386(14), C(7).C(8) 1.409(14), C(7).C(71) 1.435(15), C(71).N(211) 1.148(16), C(8).N(2) 1.296(10), N(21).O(21) 1.269(10), N(1a).C(1a) 1.071(17), C(1a).C(2a) 1.43(2); O(1).Cu.N(1) 87.9(3), O(2).Cu.N(2) 88.5(3), N(11a).Cu.N(1a) 178.0(4), C(1a).N(1a).Cu 139.8(13).F(6) F(5) F(4) C(06) C(6) O(2) C(1a) C(2a) N(2) C(10) C(102) C(101) C(9) C(92) C(91) N(21) O(21) C(8) C(7) C(71) N(211) N(1a) Cu N(11a) C(5) C(51) C(52) C(4) C(42) C(41) O(11) N(11) C(3) N(1) C(2) N(111) C(21) C(1) O(1) F(1) F(2) F(3) C(01) 3.8 3.6 3.4 3.2 3.0 0 50 100 150 200 250 T/K 300 meff (B.M.) Figure 3 The temperature dependence of meff for 9.Mendeleev Communications Electronic Version, Issue 5, 2001 3 References 1 (a) A. Caneschi, D. Gatteschi, R. Sessoli and P. Rey, Acc. Chem. Res., 1989, 22, 392; (b) O. Kahn, Molecular Magnetism, VCH, New York, 1993; (c) V. I. Ovcharenko and R. Z. Sagdeev, Usp. Khim., 1999, 68, 381 (Russ. Chem. Rev., 1999, 68, 345). 2 (a) E. F. Ullman, L. Call and J. H. Osiecki, J. Org. Chem., 1970, 35, 3623; (b) J. H. Osiecki and E. F. Ullman, J. Am. Chem. Soc., 1968, 90, 1078; (c) D. G. B. Boocock, R. Darcy and E. F. Ullman, J. Am. Chem. Soc., 1968, 90, 5945; (d) E. F. Ullman, J. H. Osiecki, D. G. B. Boocock and R. Darcy, J. Am. Chem. Soc., 1972, 94, 7049. Received: 7th May 2001; Co

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年代:2001

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Mendeleev Communications Electronic Version, Issue 5, 2001 1 Outer-sphere association of hexacyanoferrate and nitrogen betaine anions Vitalii Yu. Kotov,*a Yuliya G. Gorbunova,a Sof¡�ya A. Kostina,a Gul¡�nara K. Kadorkina,b Vasilii R. Kostyanovskyb and Remir G. Kostyanovskyb a N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian Federation.Fax: +7 095 954 1279; e-mail: tsir@elch.chem.msu.ru b N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 119991 Moscow, Russian Federation. Fax: +7 095 938 2156; e-mail: kost@center.chph.ras.ru 10.1070/MC2001v011n05ABEH001464 The electronic spectrum of an aqueous solution of an equimolar mixture of nitrogen betaine (pK1 = 1.72, pK2 = 3.62) and hexacyanoferrate anions exhibited a charge-transfer band at 26100 cm.1, which is indicative of the outer-sphere association of these ions.The cations of aromatic nitrogen-containing heterocycles [such as methyl viologen (MV2+) and pyridinium salts] are used as test materials in the studies of electron-transfer processes. Because the electron affinity of these cations is high, ion pairs with the participation of these cations exhibit absorption in the visible region of the electronic spectrum:1,2 It is well known that charge-transfer bands are characteristic of not only cation.anion associates but also anion.anion systems.3,4 In these latter, the complex ions [Fe(CN)6]3., [FeNO(CN)5]2.or [Co(edta)]. serve as electron acceptors. The contact between anions in these systems takes place by the cooperative interaction: We examined the association of hexacyanoferrate(II) ions and the anions of a nitrogen betaine, 2-N-pyridiniumhydrosuccinate- 1 1.Compound 1 was prepared according to the published procedure5 by the reaction of pyridine with maleic acid in an aqueous solution (10 days at 20 ¡ÆC).¢Ó The dissociation constants of protonated (1 + H)+ and neutral 1 forms of the nitrogen betaine were found by potentiometric titration¢Ô (pK1 = 1.72¡¾0.05 and pK2 = 3.62¡¾0.05).Betaine anion (1 . H). is resistant to an excess of an alkali (pH 11) at 20 ¡ÆC. This fact allowed us to examine its properties in aqueous solutions of compound 1 containing an excess of K2CO3. Note that the potassium salt is more readily soluble in water than compound 1, as evidenced by the 1H NMR spectrum (in D2O) of the residue after evaporation of a solution of the potassium salt (cf.ref. 5). The electronic absorption spectrum¡× of (1 . H). exhibited a long-wavelength absorption band at 38300 cm.1 (e = 3750 dm3 mol.1 cm.1) and no absorption in the visible and UV regions of the spectrum. Thus, the concentration can be varied over a wide range in the course of spectrophotometric measurements.The electronic absorption spectrum of an aqueous solution containing compound 1, K4[Fe(CN)6]¡�3H2O (0.06 mol dm.3 each) and an excess of K2CO3 (CK+ = 2 mol dm.3) exhibited a broad band at 26100¡¾100 cm.1 (n1/2 = 4700¡¾100 cm.1), which was absent from the spectra of the initial components of the mixture. The 1:1 composition of the resulting complex was determined by the isomolar series method (Figure 1).The stability constant (0.54¡¾0.06 mol dm.3 at CK+ = 2.34 mol dm.3) and the molar extinction coefficient at a band maximum (115¡¾15 dm3 mol.1 cm.1) were calculated by the Benesi.Hildebrand method6 (Figure 2). The molar extinction coefficient is close to the typical values of 150.200 dm3 mol.1 cm.1 found for ion pairs of the hexacyanoferrate ion with N-heterocyclic cations.1 The stability constant of the complex formed is close to 0.05.0.3 dm3 mol.1, which is characteristic of outer-sphere anion.anion associates.3,4 Thus, the ¢Ó 1: yield 85%, mp 214 ¡ÆC. 1HNMR (D2O) d: 3.43 (m, 2H, CH2, ABX3 spectrum, .n 68.0 Hz, 3JAX 9.9 Hz, 3JBX 4.4 Hz, 2JAB .18.0 Hz), 5.64 (dd, 1H, CH), 8.02 (dd, 2H, 2¥â-H, 3J 6.1 Hz, 3J 7.8 Hz), 8.52 (t, 1H, ¥ã-H, 3J 7.8 Hz) 8.88 (d, 2H, 2¥á-H, 3J 6.1 Hz).Found (%): N, 7.10, 7.20. Calc. for C9H9O4N (%): N, 7.18. The 1H NMR spectra were measured on a Bruker WM-400 spectrometer. K4[Fe(CN)6]¡�3H2O and other chemicals were of reagent grade. ¢Ô The potentiometric titration of a 0.1 M solution of compound 1 and its mixture with 0.1 M HCl was performed using a 0.1 M NaOH solution and a Mettler Delta 340 pH-meter with a combined pH electrode.¡× The electronic absorption spectra were measured on a Cary 100 spectrophotometer (Varian) in the frequency range 20000.50000 cm.1 at 25 ¡ÆC using quartz cuvettes with an optical path length of 1 cm. The absorption bands were approximated by Gaussian functions. MV2+ + [Fe(CN)6]4.= MV2+,[Fe(CN)6]4. MV2+,[Fe(CN)6]4. + hv ¢ç MV+,[Fe(CN)6]3. [Fe(CN)6]3. + nK+ + [Fe(CN)6]4. = [Fe(CN)6]3.,nK+,[Fe(CN)6]4. [Fe(CN)6]3.,nK+,[Fe(CN)6]4. + hv ¢ç [Fe(CN)6]4.,nK+,[Fe(CN)6]3. + 1 &22+ &+&22+ + + 1 &22 &+&22+ + 1 &22 &+&22 ¡¾ + ¡¾ + ¡¾ + 0.21 0.18 0.15 0.12 0.09 0.06 0.03 0.00 0.0 0.2 0.4 0.6 0.8 1.0 A Mole fraction Figure 1 Absorbance of the anion.anion complex (1 .H).,nK+,[Fe(CN)6]4. at n = 25000 cm.1 as a function of the mole fraction of (1 . H).. C(1-H) + + CFe(CN)6 = 0.12 mol dm.3, CK = 2 mol dm.3. 0.10 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 C0lAmax .1 /mol dm.3 cm C.1/dm3 mol.1 Figure 2 Absorbance of the anion.anion complex (1 .H).,nK+,[Fe(CN)6]4. as a function of the concentration of (1 . H). in the Benesi.Hildebrand equation coordinates. CFe(CN)6 = 0.12 mol dm.3, CK = 2.34 mol dm.3.Mendeleev Communications Electronic Version, Issue 5, 2001 2 observed absorption band can be reliably attributed to the outersphere charge transfer between the anions: The position of the charge-transfer band maximum in the test associate at the boundary between the visible and UV regions of the spectrum indicates that the electron affinity of nitrogen betaine anion (1 – H)– is lower than that of N-heterocyclic cations, which were studied previously.1 The absorption bands of the ion pairs of these N-heterocyclic cations with [Fe(CN)6]4– lie in the visible region of the spectrum, and the electron affinity is 2.8–3.5 eV, as estimated according to ref. 7. An analogous estimation gave a value of 2.5 eV for (1 – H)–. This study was supported by the Russian Foundation for Basic Research (grant nos. 00-03-40104 and 00-03-81187) and INTAS (grant no. 99-0157). References 1 H. E. Toma, Can. J. Chem., 1979, 57, 2079. 2 J. C. Curtis, B. P. Sullivan and T. J. Meyer, Inorg. Chem., 1980, 19, 3833. 3 R. Billing and D. E. Khoshtariya, Inorg. Chem., 1994, 33, 4038. 4 A. B. Nikol’skii and V. Yu. Kotov, Mendeleev Commun., 1995, 139. 5 R. G. Kostyanovsky, V. R. Kostyanovsky, G. K. Kadorkina and V. Yu. Torbeev, Mendeleev Commun., 2000, 83. 6 H. A. Benesi and J. H. Hildebrand, J. Am. Chem. Soc., 1949, 71, 2703. 7 S. I. Gorelsky, V. Yu. Kotov and A. B. P. Lever, Inorg. Chem., 1998, 37, 4584. (1 – H)– + nK+ + [Fe(CN)6]4– = (1 – H)–,nK+,[Fe(CN)6]4– (1 – H)–,nK+,[Fe(CN)6]4– + hv ® (1 – H)2–,nK+,[Fe(CN)6]3– Received: 20th April 2001; Com.

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年代:2001

数据来源: RSC

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Mendeleev Communications Electronic Version, Issue 5, 2001 1 Crystal and electronic structure of new organic semiconductors with rare-earth metal counter-anions Olga N. Kazheva,a Marc Gener,b Victor V. Gritsenko,a Nataliya D. Kushch,a Enric Canadellb and Oleg A. Dyachenko*a a Institute of Problems of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, Russian Federation.Fax: +7 096 515 3588; e-mail: doa@icp.ac.ru b Institut de Ciencia de Materials de Barcelona (CSIC), 08193 Bellaterra, Spain. Fax: +34 93 580 57 29; e-mail: canadell@icmab.es 10.1070/MC2001v011n05ABEH001477 The new molecular semiconductors (ET)5[M(NCS)6NO3]¡�EtOH (M = Dy, Y) have been studied by X-ray crystallography at 295 and 110 K, and the electronic band structure of these salts has been examined.A search for suitable counter-ions is one of the main strategic tasks in the preparation of new organic conductors and superconductors based on the salts of bis(ethylenedithio)tetrathiafulvalene (ET) and its derivatives. Here, we report on the use of rare-earth metal-complex anions for the preparation of new ET salts. In addition, changing the filling of the f shells along the lanthanide series may influence the electroconducting and magnetic properties of the possible compounds.This paper describes the crystal and electronic band structure of the new salts (ET)5[M(NCS)6NO3]¡�EtOH (M = Dy, Y) of dysprosium and yttrium. The new salts were prepared by the electrochemical oxidation of ET using the salt (Bu4N)3[M(NCS)4(NO3)2] as an electrolyte. A Bruker AXS SMART 1000 instrument1 with a CCD detector (MoK¥á line, graphite monochromator, w scanning, scanning pitch 0.3¡Æ, frame measuring time 30 s, 2q ¡Ì 60¡Æ) was used.The crystal structure was solved by direct methods and subsequent Fourier syntheses using the SHELXL-93 program package.2 The crystals of salts (ET)5[Dy(NCS)6NO3]¡�EtOH 1 and (ET)5[Y(NCS)6NO3]¡�EtOH 2 (Table 1)¢Ó are isostructural and have a layered structure (Figure 1).The crystal structure is characterised by the alternation of conducting radical cation layers including ET and ethanol molecules and anionic layers containing the complex units [M(NCS)6NO3]4. (M = Dy, Y) along the c axis. The ET layers show a clathrate architecture in which groups of four ET pairs form cavities (Figure 2).The cavities along the a and b axes are uniformly occupied in an alternating way by ET and EtOH molecules, while the cavities along the ab diagonal are occupied by only ET molecules. Note that although the donor layers of (ET)5[M(NCS)6NO3]¡�EtOH (M = Dy, Y) remind those of the well-known k-phases, first found in the organic superconductors (ET)4Hg3Cl8,4 (ET)4Hg2.78Cl8 5 and (ET)4Hg2.89Br8,5 in the present case, they contain both dimeric and monomeric ET units (and ethanol molecules).Thus, the radical cation layers have a new packing type which we propose to refer to as w-type. The conducting layers of salts 1 and 2 exhibit many short S¡�¡�¡�S contacts between ET molecules. The anionic layer contains isolated four-charged complex units [M(NCS)6NO3]4.(M = Dy, Y). The M atom of the complex anion is coordinated to six N atoms from NCS groups and to one bidentate NO3 group. Thus, the complex anion has an approximately pentagonal bipyramidal shape (Figure 3). The conductivity of (ET)5[M(NCS)6NO3]¡�EtOH (M = Dy, Y) crystals measured along the b axis in the plane of the radical ¢Ó Atomic coordinates, bond lengths, bond angles and thermal parameters have been deposited at the Cambridge Crystallographic Data Centre (CCDC).For details, see ¡®Notice to Authors¡�, Mendeleev Commun., Issue 1, 2001. Any request to the CCDC for data should quote the full literature citation and the reference number 1135/99. 6 6 6 6 6 6 6 6 (7 Figure 1 A fragment of the crystal structure of the (ET)5[M(NCS)6NO3]¡�EtOH (M = Dy, Y) salts. 0 a b c Table 1 Main crystal data for the (ET)5[M(NCS)6NO3]¡�EtOH (M = Dy, Y) salts. 1 1 2 Formula C58H46DyN7O4S46 C58H46DyN7O4S46 C58H46YN7O4S46 M 2542.28 2542.28 2468.69 T/K 295 110 110 Crystal system Monoclinic Monoclinic Monoclinic Space group P21/n P21/n P21/n a/A 17.877(4) 17.670(1) 17.749(2) b/A 15.863(3) 15.548(1) 15.567(2) c/A 33.165(11) 33.002(2) 33.052(2) b/¡Æ 97.62(2) 97.858(2) 97.921(2) V/A3 9322(4) 8981.7(9) 9045(2) Z 4 4 4 dcalc/g cm.3 1.812 1.880 1.813 m/cm.1 14.332 (CuK¥á) 1.952 (MoK¥á) 1.757 (MoK¥á) No.of observed reflections 2667 4987 7154 [F0 > 4s(F0)] GOF 1.209 1.178 1.060 Final R, wR 0.056, 0.127 0.078, 0.190 0.076, 0.175 Figure 2 View of the w-packing of the radical cations in the (ET)5- [M(NCS)6NO3]¡�EtOH (M = Dy, Y) salts.The dotted line shows short intermolecular S¡�¡�¡�S contacts [r(S¡�¡�¡�S) ¡Ì 3.68 A].3Mendeleev Communications Electronic Version, Issue 5, 2001 2 cation layers is 0.1.0.2 Ohm.1 cm.1 at room temperature. The salts exhibit a semiconducting behaviour.6 The electronic structure of these salts was analysed by tightbinding extended Huckel type calculations7 for their donor layers using a modified Wolfsberg.Helmholz formula.8 Double-z Slater type orbitals were used for C and S and single-z Slater type orbitals, for H.The exponents, contraction coefficients and parameters were taken from ref. 9. The repeating unit of a donor layer contains ten ET donors so that the band structure in the vicinity of the Fermi level contains ten HOMO bands.The calculated band structure for a donor layer of salt 2 is shown in Figure 4. Given the stoichiometry and the tetravalent nature of the anion, there must be eight holes in these HOMO bands. As shown in Figure 4, there is an energy gap between the four upper bands and the lower ones so that, in agreement with the conductivity results, salt 2 should be a semiconductor. The interaction between the two ET donors of every pair is strong so that the two HOMOs of each of these pairs lead to a low-lying orbital, which we will refer to as (Y+)HOMO, and to an upper-lying orbital, which we will refer to as (Y.)HOMO.The four upper bands in Figure 4 are built from the four (Y.)HOMO orbitals associated with the four ET pairs in the repeating unit of the donor layer.The six filled bands in Figure 4 can be divided into two groups: (a) two very flat bands, at the top of this group of filled bands, which are each associated with the HOMO of one of the single ETs and (b) four bands, slightly lower in energy, which are built from the (Y+)HOMO orbitals of the four ET pairs. Consequently, since the four empty bands are mostly based on the ET pairs, we can conclude that the paired ET donors must be considered as ET+, whereas the single ET donors must be considered as ET0.At this point the question arises of how the single ET donors should be considered, as a real part of the donor lattice or as just filling the cavities of the donor lattice built from the ET pairs (i.e., like the EtOH molecules). As far as the HOMO¡�¡�¡� HOMO interactions are concerned, this question can be answered by evaluating the so-called bHOMO.HOMO interaction energies, which are a measure of the interaction between two HOMOs in adjacent sites of the lattice.10 There are three types of HOMO¡�¡�¡� HOMO interactions: (a) intra-pair, (b) inter-pair (every ET of one pair interacts with two ETs of adjacent pairs so that every ET pair interacts with four adjacent pairs) and (c) interactions between the single ETs and the paired ones (every single ET makes a total of eight interactions with the eight donors of four adjacent ET pairs).The calculated bHOMO.HOMO values for salt 2 are very large for the intra-pair interactions (around 0.8 eV) and quite sizeable for the inter-pair interactions (0.14.0.26 eV). In contrast, of the eight interactions between the single and paired ETs, only one is associated with a sizeable bHOMO.HOMO (0.18), whereas the remaining seven are around one order of magnitude smaller.Cd, as far as the the HOMO¡�¡�¡�HOMO interactions are concerned (i.e., those determining the shape of the band structure around the Fermi level), the ET sublattice of these salts can be described as a series of ET+ dimers interacting relatively strongly among themselves but only weakly with single ET0 units partially filling the cavities of the dimers lattice.To check this conclusion, we calculated the band structure of the same ET lattice from which the single ETs are removed. The calculated band structure is very similar to that in Figure 4 except for the absence of the two upper filled very flat bands associated with the single ETs.However, as far as the band structure of Figure 4 is correct, it cannot be concluded that the single ETs do not influence the conductivity of the lattice: the holes of these semiconductors are associated with the upper flat bands (i.e., mainly with the HOMOs of the weakly interacting single ETs) and the electrons with the bottom of the more dispersive empty bands [i.e., mainly with the set of interacting (Y.)HOMO orbitals of the ET dimers].In conclusion, the novel radical cation salts (ET)5[M(NCS)6NO3]¡� EtOH (M = Dy, Y) were prepared and their crystal and electronic structures were examined. These salts have radical cation layers with a new packing type (w-type) separated by anionic layers.Despite the presence of a great number of intermolecular and intramolecular short S¡�¡�¡�S contacts in the two-dimensional radical cation layers, the salts exhibit semiconducting properties. This work was supported by the Russian Foundation for Basic Research (grant no. 00-03-32809), DGI Spain (project no. BFM2000-1312-C02-01) and Generalitat de Catalunya (1999 SGR 207).References 1 SMART (control) and SAINT (integration) Software, Version 5.0, Bruker AXS Inc, Madison, WI, 1997. 2 G. M. Sheldrick, SHELXL 93. Program for the Refinement of Crystal Structures, University of Gottingen, Germany, 1993. 3 Yu.V.Zefirov, Kristallografiya, 1997, 42, 936 (Russ. Crystallography, 1997, 42, 111). 4 R. N. Lyubovskaya, R.B. Lyubovskii, R. P. Shibaeva, M. Z. Aldoshina, L. M. Goldenberg, L. P. Rosenberg, M. L. Khidekel and Ju. F. Shulpyakov, JETP Lett., 1985, 42, 380. 5 R. N. Lyubovskaya, E. I. Zhilyaeva, S. I. Pesotskii, R. B. Lyubovskii, L. O. Atovmyan, O. A. Dyachenko and T. G. Tahkirov, JETP Lett., 1987, 46, 188. 6 N. D. Kushch, O. N. Kazheva, V. V. Gritsenko, L. I. Buravov, O. A. Dyachenko and K. V.Van, Transaction on Dielectrics and Electrical Insulation, 2001, 8, 429. 7 M.-H. Whangbo and R. Hoffmann, J. Am. Chem. Soc., 1976, 100, 6093. 8 J. Ammeter, H.-B. Burgi, J. Thibeault and R. Hoffmann, J. Am. Chem. Soc., 1976, 100, 3686. 9 A.Penicaud, K. Boubekeur, P. Batail, E. Canadell, P. Auban-Senzier and D. Jerome, J. Am. Chem. Soc., 1993, 115, 4101. 10 M.-H.Whangbo, J. M.Williams, P. C.W. Leung, M. A. Beno, T. J. Emge and H. H. Wang, Inorg. Chem., 1985, 24, 3500. S(1) C(1) N(1) S(4) C(4) N(4) N(2) C(2) S(2) N(6) C(6) S(6) N(5) C(5) S(5) O(2) N(7) O(1) O(3) C(3) N(3) S(3) M Figure 3 Structure of the [M(NCS)6NO3]4. complex anion. The M.N and M.O bond lengths at 110 K for 1 are (A): Dy.N(1) 2.39(1), Dy.N(2) 2.42(1), Dy.N(3) 2.42(1), Dy.N(4) 2.39(1), Dy.N(5) 2.35(1), Dy.N(6) 2.37(1), Dy.O(2) 2.55(2), Dy.O(3) 2.54(2). The M.N and M.O bond lengths at 110 K for 2 are (A): Y.N(1) 2.365(5), Y.N(2) 2.433(5), Y.N(3) 2.409(6), Y.N(4) 2.434(7), Y.N(5) 2.410(8), Y.N(6) 2.340(6), Y.O(2) 2.668(9), Y.O(3) 2.57(1). .7.3 .7.8 .8.3 .8.8 ¥Ã X M Y ¥Ã Energy/eV Figure 4 Calculated band structure for the donor layer of 2; the dashed line refers to the Fermi level. G = (0, 0), X = (a*/2, 0), Y = (0, b*/2) and M = (a*/2, b*/2). Received: 15th May 2001

ISSN:0959-9436     

出版商:RSC    

年代:2001

数据来源: RSC