摘要:

Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) n-Pentane carbonylation with CO on sulfated zirconia: an in situ solid-state 13C NMR study Mikhail V. Luzgin, Alexander G. Stepanov,* Vera P. Shmachkova and Nina S. Kotsarenko G. K. Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russian Federation. Fax: +7 3832 34 3056; e-mail: a.g.stepanov@catalysis.nsk.su 10.1070/MC2001v011n01ABEH001345 Using 13C CP/MAS NMR, the first evidence has been obtained for n-pentane carbonylation with carbon monoxide into C6 aldehydes, ketones and carboxylic acids on a sulfated zirconia catalyst.Since the discovery of its strong catalytic activity,1 sulfated zirconia (SZ) has found potential applications as a catalyst. The strong acidity of SZ opens up new, yet to be studied feasibility of its using as a catalyst, especially for light alkanes conversion. 2 Among the promising applications of SZ is a direct conversion of alkanes into carbonyl-containing compounds, which are of great importance for industrial organic chemistry. It is a common knowledge that alkanes can be carbonylated with carbon monoxide in superacids,3 in the presence of polyhalomethane- based superelectrophilic systems4 and in the presence of aluminium chloride as the strong solid Lewis acid.5 In this paper, using in situ solid state 13C NMR spectroscopy,† we present the first evidence for n-pentane carbonylation with CO on pure SZ as a catalyst.Figure 1 displays the 13C CP/MAS NMR spectra of the products formed from n-pentane and CO on SZ at 70 °C.‡ If unlabelled n-pentane and 13C-labelled carbon monoxide were coadsorbed [Figure 1(a)], the most intense signal becomes visible at 231 ppm from the 13C-labelled carbonyl groups of both aldehydes and ketones, strongly interacting with SZ acid sites.8 In case of using [2-13C]n-pentane 1 and unlabelled CO, only 13C-labelled groups were observed in the 13C NMR spectra: both 2-13CH2 group of 1 and carbon atoms in which the 2-13CH2 group is transformed during the reaction.The following spectral features from the reaction products appeared in the spectrum [Figure 1(b)]. Besides the signal from the labelled 13CH2 group of unreacted 1 at 24.5 ppm,6,9 two intense signals at 32.2 and 33.8 ppm [Figure 1(b)] arise from the product of n-pentane isomerization, isopentane 5 with 13C-labels at the CH and CH2 groups, respectively.9 Nine signals from the aliphatic fragments of the carbonylation products are also readily identified in this spectrum [Figure 1(b),(c)] at 22.5–54.3 ppm.Six of them, namely, at 22.5, 29.1, 36.7, 46.3, 50.8 and 54.3 ppm, originate from 2-methylpentanal 6, 2-ethylbutanal 7, 2-methylpentan- 3-one 9 and 3-methylpentan-2-one 10 (see Scheme 1§).We further confirmed the formation of the aldehydes and ketones by high-resolution 13C NMR analysis of the products extracted with Et2O from SZ.¶,†† The less intense signal at 194 ppm [Figure 1(a)], belonging to 13COOH carboxylic groups,7,11 points to the formation of carboxylic acids in addition to aldehydes and ketones.The † General experimental details. A SZ sample of low temperature tetragonal phase with a surface area of 60 m2 g–1 and 9.9 wt.% of SO3 content was synthesised according to the procedure described earlier.6 The SZ sample was calcined at 600 °C in air and at 400 °C in a vacuum (10–3 Pa) for 2 h. Equal amounts of n-pentane and CO (or n-pentane, CO and H2O) (ca. 300 µmol g–1 of each coadsorbate) were adsorbed on SZ in a vacuum at the temperature of liquid nitrogen.After sealing a glass tube with the SZ sample off from the vacuum system, it was heated at 50–150 °C for 1 h, the initial pressure of CO in the sealed tube could reach 10 atm at 150 °C. The reaction products were analysed in situ by 13C CP/MAS NMR in the sealed glass tubes containing the catalyst with adsorbed reaction products and ex situ by high-resolution 13C NMR spectroscopy in CDCl3 solution. 13C NMR spectra with cross-polarization and magic angle spinning (13C CP/MAS NMR) and high-resolution 13C NMR spectra in solution were recorded on a Bruker MSL-400 NMR spectrometer at room temperature (~23 °C). The conditions used for CP experiments are described in ref. 7, the spinning rate was 3–4 kHz. A few thousands of scans have been collected for each spectrum. The 13C chemical shifts for carbon nuclei were measured with respect to TMS as an external standard. To facilitate NMR analysis, n-pentane labelled with 13C at the second carbon atom, [2-13C]n-pentane (82% isotope enrichment), or 13CO (90% isotope enrichment) were used in NMR experiments. [2-13C]n-Pentane was prepared from [1-13C]ethanol (82% 13C) via a six-step synthesis.‡ To follow selectively the transformation of the initial reactants and for the identification of reaction products adsorbed on SZ by 13C NMR, either CO or n-pentane labelled with the 13C isotope were used. In this case only signals from 13C-labelled carbon atoms in both reactants and reaction products were preferentially observed in the spectrum.§ In Scheme 1, 13C chemical shifts for the carbons in the adsorbed initial [2-13C]n-pentane and reaction products are indicated only above the carbons with 13C labels expected in these carbon atoms as the result of the reaction according to Scheme 1. ¶ The products exhibited the following 13C NMR chemical shifts in CDCl3 solution, d: 6, 13.2 (Me), 13.9 (5-Me), 20.2 (4-CH2), 32.8 (3-CH2), 46.1 (2-CH), 204.7 (C=O); 7, 11.3 (Me), 21.5 (CH2), 55.0 (CH), 204.8 (C=O); 9, 7.7 (Me), 18.3 [(Me)2], 33.4 (CH2), 40.6 (CH), 214.5 (C=O); 10, 11.5 (5-Me), 15.7 (Me), 25.9 (4-CH2), 27.9 (1-Me), 48.7 (3-CH), 212.0 (2-C=O).The data are in complete accordance with the chemical shifts for these compounds.10 ††The conversion of n-pentane was 41% at 70 °C.The selectivity towards the reaction products was as follows: 5, 35%; 6, 12%; 7, 8%; 9, 18%; 10, 15%; 11, 5%; 12, 2.5%; and 13, 4%. * * * * * * * * * * * * * n-C5H12 + 13CO 231 194 300 250 200 150 100 50 0 d/ppm 33.8 32.2 24.5 22.5 Experimental Simulated * * * * (a) (b) (c) 54.3 50.8 46.3 43.9 36.7 35.8 29.1 27.3 * * ×2 70 60 50 40 30 20 10 0 d/ppm 65 55 45 35 25 15 5 Figure 1 13C CP/MAS NMR spectra of the products formed from n-pentane and CO on sulfated zirconia at 70 °C: (a) coadsorption of 13CO and n-C5H12; (b) coadsorption of the [2-13C]n-C5H12 and CO; (c) simulation of experimental spectrum (b).Asterisks (*) denote spinning side bands. [2-13C]n-C5H12 + COMendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) signals from 13C-labelled aliphatic carbons of the acids at 22.5, 27.3, 35.8, 43.9 and 46.3 ppm belong to 2-methylpentanoic 11, 2-ethylbutanoic 12 and 2,2-dimethylbutanoic 13 acids‡‡ (see Scheme 1§). When the reaction was carried out in the presence of water, carboxylic acids 11–13 were formed as the only products of n-pentane carbonylation. No signals from aldehydes and ketones were observed (Figure 2).§§ Thus, the following processes occur in the interaction of n-pentane with CO on SZ (see Scheme 1).Two secondary carbenium ions 2 and 3, which seem to be generated via hydride abstraction from n-pentane by SZ, react further with CO and the hydride ion to produce 6 and 7. In addition, n-pentyl cation 2 undergoes isomerization giving rise to tertiary isopentyl cation 4, from which 5 evolves. 2,2-Dimethylbutanal 8, whose formation from 4 could be expected, was not detected. Instead, two ketones 9 and 10 are generated according to the well-known property of aldehydes with a carbonyl group attached to a quaternary carbon atom to rearrange in liquid acid3(b),13 and in the presence of solid AlCl3 5(c),5(e),14 by an alkyl shift to form the corresponding ketone. Acids 11–13 seem to be formed by partial oxidation of aldehydes15 6, 7 and 8 with SZ sulfate groups,16 complete oxidation of aldehydes to acids occurs in the presence of water.15 There are two alternative routes for aldehyde formation from n-pentane.One of them involves hydride abstraction from the alkane with the formation of carbenium ions 2 and 3, the subsequent formation of oxocarbenium ions, which are further reduced under acidic hydride-transfer conditions. The other implies direct formylation of the alkane by the formyl cation [H+CO].3(b) Evidence for the reaction of n-pentane carbonylation by the first route is the formation of 5, which implies hydride abstraction from 1 to form intermediate cations 2 and 4.The formation of intermediate formate species on SZ with a signal at 176 ppm from the –HCO fragment17 [Figure 2(a)] is in Me *CH CH2 CH2 Me 2a Me *CH2 CH2 CH Me 2b Me *CH2 CH CH2 Me 3 Me *CH2 CH2 CH2 Me – H– SZ 24.5 Me *CH CH2 *CH2 Me Me *C *CH2 Me Me 4a,b Me *CH *CH2 Me Me + H– 5 Me *CH CH2 *CH2 Me 2 32.2 33.8 + CO, H– Me *CH2 CH2 *CH C 6 22.5 Me H O 50.8 [O] Me *CH2 CH2 *CH C 11 22.5 Me OH O 43.9 Me *CH2 CH CH2 Me 3 + CO, H– Me *CH2 CH C 7 22.5 H O [O] CH2 Me Me *CH2 CH C 12 27.3 OH O CH2 Me Me *C *CH2 Me Me 4 + CO, H– Me *CH2 *C C 8 H O [O] Me Me Me *CH2 *C C 13 OH O Me Me 35.8 46.3 Me *CH C *CH2 Me Me 9 O 46.3 36.7 Me *CH2 *CH C 10 Me 29.1 54.3 O Me Scheme 1 ‡‡The carboxylic acids extracted with Et2O from the catalyst reveal the following 13C NMR chemical shifts in CDCl3 solution, d: 11, 13.9 (5-Me), 16.8 (Me), 20.5 (4-CH2), 35.9 (3-CH2), 39.4 (2-CH), 183.9 (1-COOH); 12, 11.8 (Me), 24.9 (CH2), 49.0 (CH), 183.3 (COOH); 13, 9.2 (Me), 24.5 [(Me)2], 33.3 (CH2), 42.6 (C), 185.4 (COOH).The data are in complete accordance with the chemical shifts for these compounds. 12 §§ In the presence of water, the conversion of n-pentane was 40% at 150 °C with the following selectivity: 5, 83%; 11, 5%; 12, 5%; and 13, 7%.n-C5H12 + 13CO + H2O (a) (b) (c) 194 176 * * * * * * * * Experimental Simulated 100 90 80 70 60 50 40 30 20 10 0 d/ppm d/ppm 300 250 200 150 100 50 0 46.3 43.9 35.8 27.3 22.5 * Figure 2 13C CP/MAS NMR spectra of the products formed from n-pentane, CO and water on sulfated zirconia at 150 °C: (a) coadsorption of 13C-labelled CO, unlabelled n-C5H12 and water; (b) coadsorption of [2-13C]n-C5H12, unlabelled CO and water; (c) simulation of experimental spectrum (b). Asterisks (*) denote spinning side bands.[2-13C]n-C5H12 + CO + H2OMendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) favour of the second route. The formyl cation can be formed from formate as an equilibrated species.To date, we cannot elucidate by which of the two routes the carbonylation occurs. We assume that both routes for aldehyde formation are possible, similarly to the case with isobutane carbonylation on SZ.18 In conclusion, this work represents the first example of n-pentane carbonylation on a SZ catalyst. This study opens up new possibilities of using SZ catalysts for direct carbonylation of alkanes to produce valuable chemical products (carboxylic acids, aldehydes and ketones).This research was supported by the Russian Foundation for Basic Research (grant no. 99-03-32454). We are grateful to A. V. Krasnoslobodtsev for his assistance in the extraction experiments and to V. N. Zudin for the synthesis of 13C-labelled n-pentane. References 1 M. Hino, S. Kobayashi and K.Arata, J. Am. Chem. Soc., 1979, 101, 6439. 2 X. Song and A. Sayari, Catal. Rev. Sci. Eng., 1996, 38, 329. 3 (a) R. Paatz and G. Weisberger, Chem. Ber., 1967, 100, 984; (b) O. Farooq, M. Marcelli, G. K.S. Prakash and G. A. Olah, J. Am. Chem. Soc., 1988, 110, 864; (c) S. Delavarenne, M. Simon, M. Fauconet and J. Sommer, J. Am. Chem. Soc., 1989, 111, 383. 4 I. Akhrem, A. Orlinkov, L.Afanas’eva, P. Petrovskii and S. Vitt, Tetrahedron Lett., 1999, 40, 5897. 5 (a) H. Hopff, Ber., 1931, 64, 2739; (b) H. Hopff, Ber., 1932, 65, 482; (c) H. Hopff, C. D. Nenitzescu, D. A. Isacescu and I. P. Cantuniari, Ber. Dtsch. Chem. Ges. B, 1936, 69, 2244; (d) H. Pines and V. N. Ipatieff, US Patent, 2346701, 1944; (e) A. T. Balaban and C. D. Nenitzescu, Liebigs Ann. Chem., 1959, 625, 66. 6 V. M. Mastikhin, A. V. Nosov, S. V. Filimonova, V. V. Terskikh, N. S. Kotsarenko, V. P. Shmachkova and V. I. Kim, J. Mol. Catal., 1995, 101, 81. 7 M. V. Luzgin, A. G. Stepanov, A. Sassi and J. Sommer, Chem. Eur. J., 2000, 6, 2368. 8 D. H. Barich, J. B. Nicholas, T. Xu and J. F. Haw, J. Am. Chem. Soc., 1998, 120, 12342. 9 A. G. Stepanov, V. N. Sidelnikov and K. I. Zamaraev, Chem. Eur.J., 1996, 2, 157. 10 G. E. Hawkes, K. Herwig and J. D. Roberts, J. Org. Chem., 1974, 39, 1017. 11 A. G. Stepanov, M. V. Luzgin, V. N. Romannikov, V. N. Sidelnikov and K. I. Zamaraev, J. Catal., 1996, 164, 411. 12 P. A. Couperus and A. D. Clague, Org. Magn. Reson., 1978, 11, 590. 13 (a) S. Danilow and E. Vanus-Danilowa, Ber. Dtsch. Chem. Ges. B, 1926, 59, 377; (b) G. A. Olah, D. H. O’Brien and M. Calin, J. Am. Chem. Soc., 1967, 89, 3582. 14 G. A. Olah, A. Burrichter, G. Rasul, G. K. S. Prakash, M. Hachoumy and J. Sommer, J. Am. Chem. Soc., 1996, 118, 10423. 15 R. T. Morrison and R. N. Boyd, Organic Chemistry, Allyn & Bacon, Inc., Boston, 1970. 16 T. H. Clingenpeel, T. E. Wessel and A. I. Biaglow, J. Am. Chem. Soc., 1997, 119, 5469. 17 (a) T. M. Duncan and R. W. Vaughan, J. Catal., 1981, 67, 49; (b) N. D. Lazo, D. K. Murray, M. L. Kieke and J. F. Haw, J. Am. Chem. Soc., 1992, 114, 8552. 18 A. G. Stepanov, M. V. Luzgin, A. V. Krasnoslobodtsev, V. P. Shmachkova and N. S. Kotsarenko, Angew. Chem., Int. Ed. Engl., 2000, 39, 3658. Received: 22nd June 2000; Com. 00/1671

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年代:2001

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Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) Solvent-free stereoselective synthesis of â-aryl-â-amino acid esters by the Rodionov reaction using microwave irradiation Nelly N. Romanova,* Alexander G. Gravis, Pavel V. Kudan and Yuri G. Bundel’ Department of Chemistry, M. V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation. Fax: +7 095 932 8846; e-mail: rom@org.chem.msu.su 10.1070/MC2001v011n01ABEH001360 A rapid method for the title synthesis of â-aryl-â-amino acid esters was developed, and the absolute configurations of newly formed C-3 chiral centres in the major and minor diastereomers of the resulting ethyl N-[(S)-á-methylbenzyl]-â-amino-â-phenylpropionate were determined.The stereoselective synthesis of â-lactams, which are structure constituents of many natural compounds and pharmaceuticals, is of considerable importance.Homochiral â-lactams can be prepared by cyclisation of enantiomeric esters of â-amino acids that should be stereoselectively synthesised. The preparation of â-amino acid esters by the Michael reaction is performed under severe conditions and does not always result in adequate yields.1 Previously,2 it was proposed to activate the Michael reaction using microwave irradiation.This technique made it possible to obtain esters of some â-amino acids in good yields for several minutes. Note that ethyl cinnamate reacted only with morpholine under these conditions. As an extension of our studies on the rapid synthesis of â-amino acid esters, we examined the effect of microwave irradiation on the chemical yield and stereoselectivity of the Rodionov reaction.3 This reaction is primarily used for the synthesis of â-amino acids (R = H);4 however, it was found5 that â-amino acid esters (R = Et) can also be obtained by this reaction: The synthesis of â-amino esters was performed on long heating of the reactants in alcohol; however only ammonia was introduced into condensation with monoethyl malonate and substituted benzaldehydes.In this case, substituted cinnamates were always formed in considerable amounts in addition to â-amino esters. In this study, monoethyl malonate, its C-alkyl derivatives, aromatic aldehydes, benzylamine, (S)-á-methylbenzylamine and the acetates and Schiff bases of these amines were used as substrates.The conditions of the Rodionov reaction under microwave irradiation were optimised for the synthesis of ethyl N-[(S)- á-methylbenzyl]-â-amino-â-phenylpropionate. The procedure developed† was used for the syntheses of other esters (Table 1). Microwave irradiation provides some advantages in the synthesis of â-aminoesters by the Rodionov reaction. Thus, when the synthesis of ethyl N-[(S)-á-methylbenzyl]-â-amino-â-phenylpropionate was performed under conventional conditions of the Rodionov reaction (on boiling the reactants in ethanol for 10–12 h), only insignificant amounts of the ethyl ester were isolated (Table 1, entries 3 and 5).However, this ester can be obtained in a moderate yield at a similar stereoselectivity under conditions of microwave irradiation in a matter of minutes (Table 1, entry 2).On the other hand, malonic acid and monoethyl esters of C-alkyl substituted malonic acids cannot be introduced into the reaction under typical conditions, whereas ethyl malonate underwent almost quantitative conversion. Note that the replacement of benzylamine with á-methylbenzylamine did almost not decrease the chemical yields of â-amino esters (Table 1, entries 1 and 2 or 9 and 10).At the same time, substituents at the aromatic nucleus of benzaldehyde considerably affected the course of the Rodionov reaction. Electron- donating substituents in the para-position of the phenyl ring resulted in that ethyl â-amino-â-arylpropionate was not † An equimolar mixture of an aldehyde, an amine acetate, and a malonic acid derivative (without a solvent) was irradiated in an open glass vessel in a microwave oven (Funai MO785VT, 170 W) for several minutes (until the release of CO2 was complete).The reaction was monitored by TLC. The reaction products were separated by column chromatography on silica gel with a benzene–ethyl acetate eluent (2:1). Note that an increase in the microwave power up to 350 W resulted in a decrease in the yield of the target amino ester.R3 COOR COOH R1CHO R2NH2 COOR R3 R2HN R1 * * R = H, Et Scheme 1 Table 1 Chemical and optical yields of ternary Rodionov condensation.a aMicrowave experiments (MW) were performed at a power of 170 W. The chemical yields are given for chromatographically pure compounds. The structures of the compounds were supported by IR and 1H NMR spectroscopy and GC–MS.The diastereomeric composition was determined from 1H NMR spectra (400 MHz). bBoiling in ethanol. cAn azomethine was used in the reaction. dá-Methylbenzylamine was used in the reaction. eThe initial amounts of the reactants were 1 mmol. f The initial amounts of the reactants were 5 mmol. Entry Ar R t/min Reaction conditions Yield of I (%) d.e.I (%) Yield of II (%) 1 Ph PhCH2 10 MW 18 — 80 2 Ph (S )-PhCHMe 10 MW 19 35 67 3 Ph (S )-PhCHMe 720 —b 2 36 95 4 Ph (S )-PhCHMe 10 MWc 17 40 74 5 Ph (S )-PhCHMe 600 —b,c 4 32 92 6 Ph (S )-PhCHMe 14 MWd,e 17 51 68 7 Ph (S )-PhCHMe 14 MWd,f 8 53 85 8 o-O2NC6H4 (S)-PhCHMe 8 MW 21 14 72 9 p-O2NC6H4 PhCH2 10 MW 23 — 68 10 p-O2NC6H4 (S)-PhCHMe 14 MW 27 27 72 11 p-Me2NC6H4 (S)-PhCHMe 20 MW 0 — 87 12 p-Me2NC6H4 (S)-PhCHMe 16 MWc 0 — 28 13 p-MeOC6H4 (S)-PhCHMe 15 MW 0 — 34 ArCHO + RNH2·MeCOOH + HOOCCH2COOEt ArCH(NHR)CH2COOEt + ArCH=CHCOOEt I II COOEt Ph HN Ph 3 3'' 1 COOEt Ph HN Ph 3 3'' 1 3R, 3''S 3S, 3''S 2.6 : 1 EtMgBr 55% N Ph O Ph 4 1' 1' S, 4R 1' S, 4S 2.1 : 1 N Ph O Ph 4 1' Scheme 2Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) formed at all under microwave conditions (Table 1, entries 11– 13). In contrast, the electron-acceptor nitro group in the orthoor para-position increased the chemical yields of corresponding â-amino esters with respect to unsubstituted benzaldehyde (Table 1, entries 8 and 2, 9 and 1, 10 and 2). It should be emphasised that the Rodionov reaction was stereoselective with the use of the above substrates.Thus, for benzaldehyde and á-methylbenzylamine acetate under optimum conditions, d.e. was 35% (Table 1, entry 2). The presence of a nitro group at the para-position of an aromatic nucleus of benzaldehyde decreased the stereoselectivity (d.e. is as low as 27%, Table 1, entry 10). It is likely that the electron-acceptor nitro group decreases the activation energy of the addition of monoethyl malonate to an azomethine, and steric factors become less significant. The nitro group at the ortho-position results in a more dramatic decrease in the stereoselectivity (Table 1, entries 8 and 10).To study the stereochemistry of the synthesis of â-aryl-â- aminopropionates by the Rodionov reaction under microwave irradiation, we chemically determined6 the absolute configurations of the newly formed C-3 chiral centre for the major and minor diastereomers of ethyl N-[(S)-á-methylbenzyl]-â-amino- â-phenylpropionate.A mixture of the diastereomers was subjected to cyclisation to form a mixture of the corresponding diastereomers of N-[(S)-á-methylbenzyl]-4-phenylazetidin-2-one, the 1H NMR spectra of which were published.7 A comparison between the 1H NMR spectral data of the prepared â-lactam diastereomers‡ with published data7 allowed us to conclude that the major and minor diastereomers of ethyl N-[(S)-á-methylbenzyl]-â-amino-â-phenylpropionate exhibit 3Rand 3S-configurations, respectively.§ Thus, microwave activation can be successfully used for the stereoselective synthesis of â-amino acid esters by the Rodionov reaction without solvent. The procedure is easy to perform, and the esters can be obtained in moderate chemical and optical yields in 10–14 min.References 1 N. N. Romanova, A. G. Gravis and Yu. G. Bundel’, Usp. Khim., 1996, 65, 1170 (Russ. Chem. Rev., 1996, 65, 1083). 2 (a) N. N. Romanova, A. G. Gravis, G. M. Shaidullina, I. F. Leshcheva and Yu. G. Bundel’, Mendeleev Commun., 1997, 235; (b) N.N. Romanova, A. G. Gravis, I. F. Leshcheva and Yu. G. Bundel’, Mendeleev Commun., 1998, 147. 3 K. V. Vatsuro and G. L. Mishchenko, Imennye reaktsii v organicheskoi khimii (Named Reactions in Organic Chemistry), Khimiya, Moscow, 1976, p. 361 (in Russian). 4 (a) V. M. Rodionov and A. M. Fedorova, Ber. Dtsch. Chem. Ges., 1927, 60, 804; (b) T. Johnson and J.Evans, J. Am. Chem. Soc., 1930, 52, 4993; (c) V. M. Rodionov and N. G. Yartseva, Izv. Akad. Nauk SSSR, Otdel. Khim. Nauk, 1952, 103 (in Russian); (d) V. M. Rodionov and E. V. Yavorskaya, Zh. Org. Khim., 1953, 23, 983 (in Russian); (e) V. M. Rodionov and K. P. Preobrazhenskaya, Zh. Org. Khim., 1954, 24, 1971 (in Russian); ( f ) V. P. Mamaev, N. N. Suvorov and E. M. Rokhlin, Dokl.Akad. Nauk SSSR, 1955, 101, 269 (in Russian). 5 V. M. Rodionov and N. N. Bezinger, Izv. Akad. Nauk SSSR, Otdel. Khim. Nauk, 1952, 696 (in Russian). 6 (a) M. Furukawa, T. Okawara and Y. Terawaki, Chem. Pharm. Bull., 1977, 25, 1319; (b) N. Asao, T. Shimada, T. Sudo, N. Tsukada, K. Yazawa, Y. S. Gyoung, T. Uyehara and Y. Yamamoto, J. Org. Chem., 1997, 62, 6374. 7 E. Rogalska and C.Belzecki, J. Org. Chem., 1984, 49, 1397. ‡ The NMR spectra were recorded on a VXR-400 Varian spectrometer (400 MHz) in a CDCl3 solution at 28 °C using TMS as an internal standard. Protons in the 1H NMR spectra are numbered as follows: 1H NMR, d: major isomer: 1.76 (d, 3H, Me, JMe,H-1 7.30 Hz), 2.78 (dd, 1H, Ha-3, JHa-3,Hb-3 14.61 Hz, JHa-3,H-4 2.56 Hz), 3.24 (dd, 1H, Hb-3, JHb-3,Ha-3 14.61 Hz, JHb-3,H-4 5.23 Hz), 4.26 (q, 1H, H-1, JH-1,Me 7.30 Hz), 4.33 (dd, 1H, H-4, JH-4,Ha-3 2.56 Hz, JH-4,Hb-3 5.23 Hz); minor isomer: 1.28 (d, 3H, Me, JMe,H-1 7.25 Hz), 2.79 (dd, 1H, Ha-3, JHa-3,Hb-3 14.77 Hz, JHa-3,H-4 5.26 Hz), 3.20 (dd, 1H, Hb-3, JHb-3,Ha-3 14.77 Hz, JHb-3,H-4 2.58 Hz), 4.28 (dd, 1H, H-4, JH-4,Ha-3 5.26 Hz, JH-4,Hb-3 2.58 Hz), 5.01 (q, 1H, H-1, JH-1,Me 7.25 Hz). 1H NMR spectra for the major and minor diastereomers correspond to those reported7 for (1'S,4R)- and (1'S,4S)-isomers, respectively. N Ha Hb H Ph O Me Ph H 1 2 3 4 § 1H NMR, d: major diastereomer: 1.16 (t, 3H, Me-1, JMe-1,C(2)H2 7.14 Hz), 1.25 (d, 3H, Me-6, JMe-6,H-5 6.71 Hz), 1.94 (s, 1H, NH), 2.51 (dd, 1H, Ha-3, JHa-3,Hb-3 15.03 Hz, JHa-3,H-4 5.14 Hz), 2.61 (dd, 1H, Hb-3, JHb-3,Ha-3 15.03 Hz, JHb-3,H-4 9.04 Hz), 3.48 (q, 1H, H-5, JH-5,Me-6 6.71 Hz), 3.80 (dd, 1H, H-4, JH-4,Ha-3 5.14 Hz, JH-4,Hb-3 9.04 Hz), 4.06 [q, 2H, C(2)H2, JC(2)H2,Me-1 7.14 Hz], 7.15–7.35 (m, 10H, Ph). 13C NMR, d: 14.12 (Me-6), 25.05 (Me-1), 43.55 (C-3), 55.03 and 56.82 (C-4 and C-5 or reverse), 60.33 (C-2), 126.79–128.49 (Ph-4 and Ph-5), 171.57 (C=O). NH Me Ph H Ph O Me O 1 2 3 4 5 6 Received: 13th July 2000; Com. 00/1686

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摘要:

Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) Prins reaction under manganese dioxide control: the synthesis of 6-oxa-2-azabicyclo[3.2.1]octan-4-ones from tetrahydropyridines and formaldehyde Anatoly T. Soldatenkov,* Kyrill B. Polyanskii, Ayalew W. Temesgen, Svetlana A. Soldatova, Nataliya D. Sergeeva, Nadezhda M. Kolyadina and Nikolai N. Lobanov Peoples' Friendship University of Russia, 117198 Moscow, Russian Federation.Fax: +7 095 433 1511 10.1070/MC2001v011n01ABEH001386 The course of the acid-catalysed Prins reaction of tetrahydropyridines 1 with formaldehyde, leading to derivatives of piperidinodioxane 4 and 3-oxa-7-azabicyclononanes 5 and 6, is dramatically changed in the presence of manganese dioxide to give new products, 6-oxa-2-azabicyclo[3.2.1]octan-4-ones 7 and 8.The previous studies of acid-catalysed condensation of 4-arylsubstituted terahydropyridines (THPs) 1 with an excess of formaldehyde and sulfuric acid have shown that this Prins reaction gave 3-hydroxymethyl THPs 21 or, in the case of a tenfold molar excess of formaldehyde, corresponding piperidinodioxanes 32 (Scheme 1). In repeating an analogous reaction of THP 1a with a fourfold excess of formaldehyde, we separated not only known 1,3-dioxane 3a but also three new products: 8-hydroxymethyl derivative of piperidinodioxane 4 and 3-oxa- 7-azabicyclo[3.3.1]nonanes 5 and 6, the last two being isomers by the position of 9-hydroxyl in respect to the ring nitrogen atom (cis N/9-OH and trans N/9-OH, respectively).The X-ray diffraction data suggest that piperidine and tetrahydropyrane rings in the crystalline form of cis-isomer 5 (Figure 1 shows the general view and numeration of atoms in a molecule of 5) exhibit a chair conformation; the hydroxyl group of one molecule forms an intermolecular hydrogen bond with the nitrogen atom of another molecule.In solution, the piperidine ring of the same isomer (1H NMR spectra in CDCl3) has a boat conformation fixed by an intramolecular hydrogen bond.As a continuation of our work on the new oxidative reactions of hydropyridines initiated by manganese compounds,3–5 we report the reaction of THPs 1a,d with an excess of formaldehyde in the presence of manganese dioxide with an emphasis on the modification of the Prins method to prepare an oxidatively new heterocyclic system (Scheme 2, conditions i).A conventional chromatographic procedure gave product 7 in an isolated yield of 31% (from THP 1a) and a product 8 in 35% yield (from 1d). The structures of these compounds were different from those of compounds obtained by the Prins reaction previously1,2,6 or in this work (Scheme 1, conditions ii). Compounds 7 and 8 showed spectroscopic data consistent with the structure of 6-oxa-2-azabicyclo[ 3.2.1]octan-4-ones, indicating an unexpected addition of formaldehyde at the á-position of a THP heterocycle and unusual oxidation of the latter into a â-piperidone fragment.The key step in the mechanism of the formation of bicyclooctanes 7, 8 may be the oxidative dehyrogenation of the initial THPs to form intermediate 1,2-dihydropyridines.It is clear that analogous dihydropyridines should be formed as intermediates in other experiments (Scheme 2, conditions ii), which demonstrated the readiness of THPs 1a,d to transformation into pyridines 9, 10 on boiling in toluene in the presence of MnO2. The data thus obtained allow us to propose the following sequence for the synthesis of bicyclooctanones 7, 8 (Scheme 3).Dihydropyridines I formed at the initial oxidative step are then selectively attacked by protonated formaldehyde at the á-position (C-6) to give carbocations II stabilised by species III. The intramolecular cycloaddition yields bicyclic cation IV, which leads to final products 7 and 8 via hydroxylation followed by the oxidative dehydrogenation of intermediate alcohol V.The trasformation of secondary alcohols into ketones under the action of MnO2 is well documented.7 The 1H and 13C NMR spectral data together with the Dreiding modelling and molecular mechanic calculations of conformer energies are consistent with a distorted (flatted) boat conformation of a piperidine ring cis-1,3-diaxially condensed with a tetrahydrofuranic ring, which has a rigid envelope confomation.Thus, the series of conversions demonstrates a new useful method for an effective control of the Prins reaction by man- N O O R Ph N Ph R N Ph R OH 3a–c 1a–c 2a–c i i ii N O O Me Ph HO N O Me HO Ph N O Me Ph OH 3a 4 5 6 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 a R =Me b R = CH2Ph c R = But Scheme 1 Reagents and conditions: i, CH2O, H+; ii, 1a:CH2O = 1:4, boiling in aqueous H2SO4, 7 h, then 20 °C, 18 h.Scheme 2 Reagents and conditions: i, 1:CH2O:MnO2:H2SO4 = 1:3:5:6, boiling in an aqueous solution, 7 h; ii, 1:MnO2 = 1:10, boiling in toluene, 3 h. 7, 9 Ar = Ph 1d, 8, 10 Ar = p-MeC6H4 N Ar Me 9, 10 1a,d 7, 8 ii i 1 2 3 4 5 6 7 8 N Ar O N Ar O Me 1a,d N Ar Me N Ar Me OH N Ar Me OH N Ar Me O [O] I II III N Ar Me O + H2O – H+ OH [O] 7, 8 IV V Scheme 3Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) ganese dioxide, which dramatically changes the course of condensation of tetrahydropyridines with formaldehyde leading to a new group of 6-oxa-2-azabicyclo[3.2.1]octan-4-ones. The structures of compounds 3a and 4–10 were confirmed spectroscopically.† This work was supported by the Russian Foundation for Basic Research (grant no. 99-03-32940a). References 1 C. J. Schmidle and R. C. Mansfield, US Patent 2748140, 1956 (Chem. Abstr., 1957, 51, 2880f). 2 A. F. Casy, A. B. Simmonds and D. Staneforth, J. Org. Chem., 1972, 37, 3189. 3 A. T. Soldatenkov, A.W. Temesgen, L. N. Kuleshova and V. N. Khrustalev, Mendeleev Commun., 1998, 193. 4 A. T. Soldatenkov, A. W. Temesgen, I. A. Bekro, T.P. Khristoforova, S. A. Soldatova and B. N. Anissimov, Mendeleev Commun., 1997, 243. 5 A. T. Soldatenkov, A. W. Temesgen, I. A. Bekro, S. A. Soldatova and B. N. Anissimov, Mendeleev Commun., 1998, 137. 6 A. F. Casy and F. Ogungbamila, Heterocycles, 1981, 16, 1913. 7 S. P. Korshunov and L. I. Vereshchagin, Usp. Khim., 1966, 35, 2255 (Russ. Chem. Rev., 1966, 35, 942). 8 A.E. Chichibabin and D. I. Orochko, Zh. Russ. Fiz.-Khim. Obshch., 1930, 62, 1201 (in Russian). † NMR spectra were recorded at 300 MHz (1H) and 75.5 MHz (13C), standard TMS, CDCl3. Compounds 3a and 4–10 gave satisfactory elemental analyses. For 3a: yield 15%, mp 60–62 °C (lit.,2 3a·HCl, mp 320 °C). 1H NMR, d: 1.8 (m, 2H, 8-CH2), 2.37 (s, 3H, Me), 2.5–3.2 (m, 5H, 5-CH2 and 7-CH2 and 4-Ha), 3.6 (d, 1H, 4-CH2, 2J 11.5 Hz), 3.8 (dd, 1H, 4-CH2, 2J 11.5 Hz, 3J 2.5 Hz), 4.77 and 4.83 (2d, 1H each, 2-CH2, 2J 6.5 Hz), 7.3 (m, 5H, Ph).MS (EI, 70 eV), m/z (%): 233 (7) [M+], 174 (38), 128 (5), 105 (11), 77 (12), 57 (13), 44 (100). For 4: yield 6%, mp 88–90 °C. 1H NMR, d: 1.57 (br. s, 1H, 8-H), 2.34 (s, 3H, Me), 2.83–3.05 (m, 6H, 5-CH2 and 7-CH2 and CH2OH), 3.53 (d, 1H, 4-CH2, 2J 11.6 Hz), 3.61 (dd, 1H, 4-CH2, 2J 11.6 Hz, 3J 2.6 Hz), 3.9 (dd, 1H, 4-Ha, 3J 11.7 Hz, 4J 2.0 Hz), 4.75 and 4.83 (2d, 1H each, 2J 6.1 Hz), 7.28–7.5 (m, 5H, Ph). 13C NMR, d: 35.1 (8-C), 46.1 (Me), 47.1 (4a-C), 55.2 (5-C), 57.2 (7-C), 65.8 (COH), 66.2 (4-C), 77.7 (Cquat–O), 89.4 (2-C), 126.5, 127.5, 128.4, 129.3 and 140.7 (6C, Ph); MS, m/z: 263 [M+]. IR (KBr, n/cm–1): 3310 (OH). Found (%): C, 68.21; H, 8.16; N, 5.28.Calc. for C15H21NO3 (%): C, 68.44; H, 7.99; N, 5.32. For 5: yield 14%, mp 176 °C. 1H NMR, d: 2.38 (s, 3H, Me), 2.68 (m, 2H, 1-H and 5-H), 2.84 (dd, 2H, 6-H and 8-H, 2J 11.1 Hz, 3J 2.5 Hz), 3.25 (dd, 2H, 6-H and 8-H, 2J 11.1 Hz, 3J 7.3 Hz), 3.64 (d, 2H, 2-H and 4-H, 2J 11.4 Hz), 3.75 (d, 2H, 2-H and 4-H, 2J 11.4 Hz), 7.3–7.5 (m, 5H, Ph). 13C NMR, d: 37.9 (1-C and 5-C), 45.1 (Me), 55.9 (6-C and 8-C), 69.8 (2-C and 4-C), 71.8 (9-C), 126.1, 127.8, 128.9 and 141.6 (6C, Ph).MS, m/z (%): 233 (100) [M+], 232 (38), 216 (27), 190 (20), 184 (8), 170 (10), 133 (34), 128 (35), 105 (38), 91 (15), 77 (16). IR (KBr, n/cm–1): 3220 and 3410 (br. OH). Found (%): C, 71.92; H, 8.27; N, 5.85. Calc. for C14H19NO2 (%): C, 72.10; H, 8.27; N, 6.01.For 6: yield 7%, mp 180 °C. 1H NMR, d: 2.12 (s, 3H, Me), 2.37 (m, 2H, 1-H and 5-H), 2.42 (d, 2H, 6-H and 8-H, 2J 11.4 Hz), 3.0 (d, 2H, 6-H and 8-H, 2J 11.4 Hz), 4.02 (dd, 2H, 2-H and 4-H, 2J 10.9 Hz, 3J 2.3 Hz), 4.54 (dd, 2H, 2-H and 4-H, 2J 10.9 Hz, 3J 2.3 Hz), 7.3–7.5 (m, 5H, Ph). 13C NMR, d: 38.3 (1-C and 5-C), 46.5 (Me), 58.3 (6-C and 8-C), 67.4 (2-C and 4-C), 71.3 (9-C), 125.4, 128.0, 129.1, 142.4, (6C, Ph).MS, m/z (%): 233 (100) [M+]. IR (KBr, n/cm–1): 3200 and 3420 (br. OH). Found (%): C, 72.2; H, 8.23; N, 5.91. Calc. for C14H19NO2 (%): C, 72.10; H, 8.27; N, 6.01. C(15) C(16) C(14) C(17) C(13) C(12) C(5) O(11) C(4) C(6) C(10) C(3) C(7) C(8) O(9) N(1) C(2) Figure 1 General view and numeration of atoms in a molecule of 5 (X-ray diffraction data).Received: 17th October 2000; Com. 00/1712 For 7: yield 31%, colourless oil (purified by chromatography on a silica gel column; eluent, acetone; Rf 0.7). 1H NMR, d: 2.51 (s, 3H, Me), 3.0 (t, 1H, 8-Ha, 2J » 3J 12.6 Hz), 3.16 (br. d, 1H, 8-He, 2J 12.6 Hz), 3.73 (t, 1H, 7-Ha, 2J 10.7 Hz), 4.0 (m, 1H, 1-He), 4.12 (d, 1H, 3-Ha, 2J 9.5 Hz), 4.23 (br. d, 1H, 7-He, 2J » 3J 10.7 Hz), 4.42 (br.d, 1H, 3-He, 2J 9.5 Hz), 7.3–7.5 (m, 5H, Ph). MS, m/z (%): 217 (16) [M+], 202 (43), 187 (15), 131 (12), 105 (100), 77 (37). IR (paraffin oil, n/cm–1): 1680 (C=O), 3360 (br. OH). Found (%): C, 71.7; H, 7.03; N, 6.52. Calc. for C13H15NO2 (%): C, 71.89; H, 6.91; N, 6.45. For 8: yield 35%, colourless oil (purified by chromatography on a silica gel column; eluent, acetone; Rf 0.7). 1H NMR, d: 2.39 (s, 3H, Me), 2.51 (s, 3H, Me), 2.98 (t, 1H, 8-Ha, 2J » 3J 12.9 Hz), 3.16 (br. d, 1H, 8-Ha, 2J 12.9 Hz), 3.76 (t, 1H, 7-Ha, 2J 10.9 Hz), 4.07 (m, 1H, 1-He), 4.10 (d, 1H, 3-Ha, 2J 9.4 Hz), 4.20 (br. d, 1H, 7-He, 2J 10.9 Hz), 4.40 (br. d, 1H, 3-He, 2J » 3J 9.4 Hz), 7.27 and 7.86 (AA'BB' system, 4H, Ar, 3J 7.2 Hz, 4J 1.1 Hz). 13C NMR, d: 22.6 (CMe), 40.3 (1-C), 40.8 (NMe), 55.8 (8-C), 70.2 (7-C), 86.7 (3-C), 129.7 (5-C), 129.3, 130.5, 144.3, 145.4 (Carom.), 200.0 (C=C). MS, m/z (%): 231 (7) [M+], 216 (36), 203 (6), 188 (28), 172 (34), 160 (38), 145 (12), 119 (100), 91 (45). IR (paraffin oil, n/cm–1): 1675 (C=O), 3350 (br. OH). Found (%): C, 73.01; H, 7.49; N, 5.90. Calc. for C14H17NO2 (%): C, 72.72; H, 7.36; N, 6.06. For 9: yield 45%, mp 76–78 °C (lit.,8 mp 76–78 °C). 1H NMR and mass spectra are identical to those given in ref. 3. For 10: yield 42%, mp 43–45 °C. 1H NMR, d: 2.4 (s, 3H, Me), 7.25 and 7.5 (AA'BB' system, 4H, Ar, 3J 7.1 Hz, 4J 1.1 Hz), 7.61 and 8.63 (AA'XX' system, 4H, Py, 3J 5.4 Hz, 4J 2.0 Hz). MS, m/z (%): 169 (100) [M+], 168 (43), 155 (95), 91 (20). Found (%): C, 84.98; H, 6.67; N, 8.01. Calc. for C12H11N (%): C, 85.21; H, 6.51; N, 8.28.

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年代:2001

数据来源: RSC

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Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) Hexamethyldisilazane as an amination agent: one-pot synthesis of isoamarine and its pyridine analogue Electron A. Mistryukov N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119992 Moscow, Russian Federation. Fax: +7 095 135 5328 10.1070/MC2001v011n01ABEH001384 The ability of hexamethyldisilazane to convert aldehydes into Schiff bases was adapted to the one-pot syntheses of isoamarine and its pyridine analogue.Here, the conversion of a non-enolisable aldehyde function into a Schiff base with hexamethyldisilazane (HMDS) under LiBr catalysis via amination–dehydration is reported.1 The choice of aldehydes is connected with the synthesis of vicinal diamines such as diphenylethylenediamine and its pyridine analogue.For these purposes, two aldehydes (benzaldehyde 1a and 2-pyridinecarboxaldehyde 1b) were used as starting materials for the synthesis of isoamarine 2a† and its pyridine analogue 2b‡ as intermediates for the corresponding vicinal diaryl ethylenediamines. The reported procedure for 1,2-diphenylethylenediamine- 1,2 includes reduction and hydrolysis of 2a.2 The multistage synthesis of 2a is known,3 where the first product is bis-Schiff base 3a§ formed by deamination of a probable unstable trimeric Schiff base, sym-triazine 4a.Corresponding sym-triazine 4b, a derivative of aldehide 1b, is a stable compound.4 In the case of 1a, when HDMS is an amination agent, we found that the sequence 1a ® 4a ® 3a ® ® 5a ® 2a can be performed with a high yield by a one-pot procedure.Moreover, if 3a, 5a or 2a is the aim product, the reaction may be stopped at any intermediate stage by changing the conditions (Scheme 1). For example, if the first intermediate of aldehyde amination by HMDS (compound 3a) is to be isolated, the reaction is performed in a THF or diethyl ether solution with no basic catalyst added.Trasformation to cyclic products requires a basic catalyst and thermal treatment. The kinetic product of cyclization, cis-imidazoline 5a, may be obtained by the thermal process in DMSO with sodium hydroxide catalysis under mild conditions. The reaction of HMDS with aldehyde 1b is of special interest. Here, no catalyst addition is required, the reaction is exothermic and gives, depending on conditions, either itermediate bis-Schiff base 3b¶ or pyridoisoamarine 2b.The conversion of 3b into cyclic product 2b is to be noted. Contrary to the conversion of 3a into a cyclic product, where a thermal or catalytic reaction gives different products, cis-5a or trans-2a, compound 3b gives the same isomer (probably, trans-2b) by either catalytic (NaOH) or thermal process, although the latter is much slower (ca. 30% coversion after 1 h at 140 °C). Deep colour formation at the NaOH-catalysed conversion of 3b into 2b indicates different structures of transition states for 2a and 2b. References 1 N. Duffaut and J.-P. Dupin, Bull. Soc. Chim. Fr., 1966, 3205. 2 E. J. Corey and F. N. M. Kuhnle, Tetrahedron Lett., 1997, 38, 4466. 3 O. F. Williams and J. C.Bailer, J. Am. Chem. Soc., 1959, 81, 4466. 4 C. Harries and G. Lenart, Liebigs Ann. Chem., 1915, 410. † Synthesis of 2a, one-pot procedure. To a solution of 1a (0.1 mol, 10.13 ml) and 0.1 g of LiBr in 20 ml of DMSO (argon) HMDS (0.11 mol, 23.05 ml) was added with stirring. The spontaneous temperature raise was accompanied by ammonia evolution (T ~ 50 °C). After the exothermal stage NaOH (1 g) was added, and siloxane was distilled off by a gradual raise of temperature to 120–130 °C.After 2 h at 130 °C the cooled mixture was poured onto aqueous ammonia (50 ml), and the suspension was left to stand overnight. The product was filtered off, washed with ammonia, acetone and hexane and dried on the filter. The yield of 2a was 8.15 g (83%), mp 198–201 °C. 1HNMR (CDCl3) d: 7.97–7.26 (m, 15H), 4.93 (s, 2H, CH), 1.7 (br. s 1H NH).‡ Synthesis of 2b. One-pot procedure. A mixture of 1b (0.1 mol, 9.52 ml), 0.1 mol of HMDS (20.9 ml) and 20 ml of DMSO was stirred under argon. The temperature gradually raised to ca. 90 °C (30 min) with ammonia evolution. When the temperature started to drop, the mixture was heated to 90 °C for 15 min. To the cooled heterogeneous mixture (the upper layer of siloxane) 1.2 g NaOH was added to immediately give a deep red colour.By gradual heating up to 135 °C, siloxane was distilled off and, after 1 h at 130 °C, the cooled mixture was treated with 1.8 ml of AcOH and then 30 ml of ammonia. After 12 h at room temperature, the suspention was filtered, washed with ammonia (2×10 ml), the filter cake was dried by suction and washed with diethyl ether (2×10 ml).After drying, the product was dissolved in 60 ml of hot toluene and filtered through a silica gel bed. On cooling, the precipitated crystals of 2b were filtered off and washed with toluene and hexane. Total yield 6.8 g, mp 132–133 °C. 1H NMR (DMSO) d: 8.0 (br. s, 1H, NH), 7.2–8.7 (m, 12H, Py), 5.25 (s, 2H, CH). § Synthesis of 3a.The mixture of 0.1 mol of 1a, 0.1 g LiBr, 0.1 mol of HMDS and 20 ml of THF was stirred under argon at 50–80 °C until evolution of ammonia subsided (ca. 2 h). The solvent was removed on a rotary evaporator, and the residue was dissolved in hot hexane. The solution was filtered through a silica gel bed and cooled. After filtration, the yield of 3a3 was 9.33 g (94%), mp 101–102 °C. 1H NMR (DMSO) d: 6.05 (s, 1H, CH), 7.3–7.9 (m, 15H, ArH), 8.7 (s, 2H, CH). ¶ Synthesis of 3b. A solution of 1b (0.1 mol, 9.52 ml), 0.1 mol of HMDS (20.9 ml) in 20 ml DMSO was stirred under argon. The temperature spontaneously raised to ca. 90 °C with ammonia evolution and when the exothermal stage subsided, this temperature was kept for additional 20 min. On cooling, the two-phase reaction mixture gave copious crystals. After filtration and washing with dioxane and toluene, the yield of 3b was 7.4 g (86%), mp 149–150 °C. 1H NMR (DMSO) d: 7.7 (br. s, 1H), 6.9– 8.7 (m, 12H), 5.6 (br. s, 2H). Scheme 1 Reagents and conditions: i, HDMS, NH3, – H2O, DMSO, LiBr cat.; ii, – NH3, heat; iii, heat; iv, NaOH cat. RCHO HN N NH R R R H i ii N N R R R iii NH N R R R 1a,b 4a,b 3a,b 5a,b a R = Ph b R = 2-pyridyl NH N R R R 2a,b iv Received: 16th October 2000; Com. 00/1710

ISSN:0959-9436     

出版商:RSC    

年代:2001

数据来源: RSC

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Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) Novel synthesis of 3,4-dicyanofuroxan Tat’yana M. Mel’nikova, Tat’yana S. Novikova, Lenor I. Khmel’nitskii and Aleksei B. Sheremetev* N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119992 Moscow, Russian Federation. Fax: +7 095 135 5328; e-mail: sab@cacr.ioc.ac.ru 10.1070/MC2001v011n01ABEH001369 3,4-Dicyanofuroxan was synthesised by diazotization of aminofurazans bearing the second substituent that can be eliminated as a cationic species.Reactions of aminofurazans 1, where R = alkyl or (hetero)aryl, with nitrosating agents is known to produce á-hydroxyiminoacetonitrile derivatives 2.1 The formation of acyclic products 2 has been attributed to the initial elimination of dinitrogen from the diazonium cation, the migration of a cationic centre with ring cleavage and the trapping of a proton from the medium.Despite the relative ease of this cleavage reaction, its synthetic potential appears to be unexplored. To the best of our knowledge, only a single example of its effective utilization for preparation of 1-cyano-2-hydroxytetrazole 3 was reported.2 We believed that the diazotization reaction can be a versatile route to heterocyclic compounds via a ring opening/reclosure strategy.Here, we demonstrate that 3,4-dicyanofuroxan 4 can be prepared via diazotization of aminofurazans bearing the second substituent that can be eliminated as a cationic particle. The treatment of 3-amino-4-nitrofurazan 53 with 3–6 equivalents of NaNO2 in H2SO4/AcOH at 30–35 °C afforded furoxan 4† in 4–8% yield and an additional water-insoluble product, 3-azido- 4-nitrofurazan 6,† in 2–5% yield.Pure compound 4 was obtained by preparative chromatography on silica gel. However, the diazotization of 5 resulted in water-soluble triazene 7† (59– 77%) as a principal product (Scheme 1). The reaction of 3-aminofurazancarboxylic acid 87 under similar conditions‡ afforded furoxan 4 as a single water-insoluble product in 22% yield (Scheme 2).The most successful diazotization approach to compound 4 appears to be a similar reaction‡ of readily available 3-amino- 4-nitrosofurazan 9,§ in which 4 was obtained in 72% yield after 1 h. No other products were detected. Moreover, when this reaction was carried out in the presence of a solvent able to extract product 4 but not dissolving starting compound 9 (for example, CH2Cl2–pentane, 1:1), pure 4 was isolated in 91% yield.The mechanism for the formation of 4 is proposed in Scheme 3. The reaction proceeds via dinitrogen elimination from diazonium cation 10 to give labile furazan cation 11. Calculations¶ suggest that in 11 cleavage of N–O bond nearer to the carbocation centre, would be preferred.This results in acyclic cation 12. The intermediate is stabilised by elimination of a cationic species (NO2 + from 5, H+ and CO2 from 8 or NO+ from 9) to form cyanogen mono-N-oxide 13. The dimerization of nitrile oxide 13 produced target furoxan 4.†† † Compounds 4,4 6,5 and 75,6 corresponded to materials described previously.‡ General procedure. Sodium nitrite (15 mmol) was added to conc. H2SO4 (90 mmol) at 0–5 °C; then, a solution of an aminofurazan (3– 10 mmol) in AcOH (~10 ml) was added dropwise at room temperature. After stirring at 30–35 °C for 1–2 h and cooling to room temperature, the reaction mixture was poured into CH2Cl2–H2O. The organic layer was washed and dried over Na2SO4. After the removal of the solvent, the residue was purified by sublimation. Furoxan 4 was obtained as offwhite flakes, mp 42–42.5 °C (lit.,4 42 °C). N O N R NH2 NO+ N O N R N2 – N2 N O N R ON R N R NOH CN 1 2 N O N N3 NH2 NO+ N3 NOH CN N N N N CN OH 3 § The synthesis of 3-amino-4-nitrosofurazan 9 was carried out by a modification of the procedure reported for the synthesis of other nitrosofurazans. 8 To a mixture of benzene (200 ml) and 27.5% H2O2 (145 ml, 1290 mmol) at 5–10 °C, Na2WO4·2H2O (16.5 g, 50 mmol) (in small portions) and then H2SO4 (10 ml, 180 mmol) were added. 3,4-Diaminofurazan (5 g, 50 mmol) was added slowly, and the resulting mixture was stirred at 10–15 °C for 1.5 h. The green organic layer was separated. An additional portion of benzene (100 ml) was introduced. The emulsion was stirred at room temperature for 1 h, and the organic layer was separated.The green extracts were combined, washed and dried over Na2SO4. The solvent was removed on a rotary evaporator, and the residue was purified by sublimation to provide 4.92 g (86.4%) of dimeric nitroso compound 9 as a khaki solid: mp 79–80 °C; UV-VIS (CCl4, lmax/nm): 750. IR (KBr, n/cm–1): 3439, 3335, 1639, 1490, 1420, 1310– 1290, 1120, 1020, 890, 780.Found (%): C, 20.97; H, 1.91; N, 49.01. Calc. for C4H4N8O4 (%): C, 21.06; H, 1.76; N, 49.12. ¶ To estimate the strength of chemical bonds, we calculated the enthalpies of dissociation by semi-empirical quantum-chemical methods (MOPAC code). N O N O2N NH2 5 N O N NC CN 4 O N O N O2N N3 6 N O N O2N N N O N NO2 NH N 7 i Scheme 1 Reagents and conditions: i, NaNO2/H2SO4, 5 in AcOH, 30– 35 °C, 1–2 h.N O N HO2C NH2 8 N O N NC CN 4 O N O N ON NH2 9 i i Scheme 2 Reagents and conditions: i, NaNO2/H2SO4, 8 or 9 in AcOH, 30–35 °C, 1–2 h.Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) 3,4-Dicyanofuroxan 4 is an important building block in organic synthesis,4,9–15 and exhibits interesting biological and pharmacological properties, for instance, as a vasodilator.16 It can be used as an ingredient of explosives17 and rocket propellants. 11,18 Previously, compound 4 was prepared by oxidation of dicyanoglyoxime,12 by treatment of cyanoacetic acid with nitrating mixtures,9,17 and by dehydration of 3,4-bis- (hydroxyiminomethyl)furoxan.19 Although these reactions are effective, alternative processes with other precursors may be very useful.References 1 A. B. Sheremetev, N. N. Makhova and W. Friedrichsen, Adv. Heterocycl. Chem., 2000, 78, 65. 2 A.M. Churakov, S. L. Ioffe, V. S. Kuzmin, Yu. A. Strelenko, Yu. T. Struchkov and V. A. Tartakovsky, Khim. Geterotsikl. Soedin., 1988, 1666 [Chem. Heterocycl. Compd. (Engl. Transl.), 1988, 24, 1378]. 3 T.S. Novikova, T. M. Mel’nikova, O. V. Kharitonova, V. O. Kulagina, N. S. Aleksandrova, A. B. Sheremetev, T. S. Pivina, L. I. Khmel’nitskii and S. S. Novikov, Mendeleev Commun., 1994, 138. 4 M. Barbieux-Flammang, S. Vandervoorde, R. Flammang, M. W. Wong, H. Bibas, C. H. L. Kennard and C. Wentrup, J. Chem. Soc., Perkin Trans. 2, 2000, 473. 5 A. B. Sheremetev, N. S. Aleksandrova, T.M.Melnikova, T. S. Novikova, Yu. A. Strelenko and D. E. Dmitriev, Heteroatom Chem., 2000, 11, 48. 6 A. M. Churakov, S. L. Ioffe, Yu. A. Strelenko and V. A. Tartakovsky, Tetrahedron Lett., 1996, 37, 8577. 7 G. Longo, Gazz. Chim. Ital., 1931, 61, 575. 8 A. B. Sheremetev, T. S. Novikova, T. M. Mel’nikova and L. I. Khmel’nitskii, Izv. Akad. Nauk SSSR, Ser. Khim., 1990, 1193 (Bull. Acad.Sci. USSR, Div. Chem. Sci., 1990, 39, 1073). 9 C. O. Parker, W. D. Emmons, H. A. Rolewicz and K. S. McCallum, Tetrahedron, 1962, 17, 79. 10 E. C. Lupton and G. Hess, J. Chem. Eng. Data, 1975, 20, 135. 11 W. R. Carpenter, US Patent, no. 3386968, 1968 (Chem. Abstr., 1968, 69, 28106]. 12 C. Grundmann, G. W. Nickel and R. K. Bansal, Liebigs Ann. Chem., 1975, 1029. 13 J. H. Boyer and T.P. Pillai, Heterocycles, 1982, 19, 1063. 14 T. Shimizu, Y. Hayashi, T. Taniguchi and K. Teramura, Tetrahedron, 1985, 41, 727. 15 G. Kh. Khisamutdinov, T. A. Mratkhuzina, R. M. Gabdullin, I. Sh. Abdrakhmanov, S. P. Smirnov, O. A. Rakitin, T. I. Godovikova and L. I. Khmel’nitskii, Izv. Akad. Nauk, Ser. Khim., 1995, 1559 (Russ. Chem. Bull., 1995, 44, 1499). 16 R. Ferioli, G. C. Folco, C. Ferretti, A. M. Gasco, C. Medana, R. Fruttero, M. Civelli and A. Gasco, Br. J. Pharmacol., 1995, 114, 816. 17 R. H. Homewood, V. J. Krukonis and R. C. Loszewski, US Patent, no. 3832249, 1974 (Chem. Abstr., 1975, 82, 113795). 18 D. D. Denson and F. M. VanMeter, US Patent, no. 3740947, 1973 (Chem. Abstr., 1973, 79, 94195). 19 H. Wieland, Liebigs Ann. Chem., 1925, 444, 7. ††The synthesis of 4 by dimerization of 13 was discussed previously.9,10 N O N X N2 10 N O N X 11 – N2 N X N O 12 – X+ CN N O 13 4 Scheme 3 Received: 24th August 2000; Com. 00/1695

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Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) New functional glycoluril derivatives Konstantin Yu. Chegaev, Angelina N. Kravchenko, Oleg V. Lebedev and Yurii A. Strelenko N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119992 Moscow, Russian Federation. Fax: +7 095 135 5328 10.1070/MC2001v011n01ABEH001357 Functional glycoluril (2,4,6,8-tetraazabicyclo[3.3.0]octan-3,7-dione) derivatives containing 2-hydroxyethyl, carboxyl and amino groups were synthesised.It is well known that glycoluril derivatives (2,4,6,8-tetraazabicyclo[ 3.3.0]octan-3,7-diones, TABODs) show a wide range of biological activity,1,2 for example, 2,4,6,8-tetramethyl- 2,4,6,8-tetraazabicyclo[3.3.0]octan-3,7-dione is used in clinical practice as the tranquilliser Mebicar.3 The capability of TABODs to exhibit simultaneously both hydrophilic and lipophilic properties is responsible for the physiological action of these compounds.On the one hand, they can easily penetrate into the body and, on the other hand, readily overcome the hematoencephalic barrier. It is interesting to perform a combinatorial synthesis of TABODs with other known classes of biological substances in order to refine the mechanism of biological effects.To solve this problem, we prepared functional TABOD derivatives containing amino, 2-hydroxyethyl and carboxyl groups for the first time. The addition of functional groups to nitrogen atoms of TABODs was almost not described in the literature. Only particular examples of N-hydroxymethyl derivatives, which were prepared by the reaction of TABODs with an alkaline formaldehyde solution, are known.4 For the most part, di-Nhydroxymethyl and tetra-N-hydroxymethyl derivatives of TABODs were synthesised.Two approaches may be suggested to prepare TABOD derivatives of interest. One of them consists in the introduction of a functional group into a completed TABOD molecule, which is used for the hydroxymethyl derivatives of TABODs.The other uses a bicyclization reaction involving specially synthesised ureas containing functional groups at nitrogen atoms. We decided on the latter method because the nitrogen atoms of TABODs exhibit a weak nucleophilicity. It is well known that TABODs can be prepared by the reaction of ureas with á-dicarbonyl compounds or 4,5-dihydroxyimidazolidin- 2-ones in aqueous or aqueous-ethanol media in the presence of acids5 (Scheme 1).The syntheses of ureas containing amino acid units starting from amino acid esters are known.6,7 We developed a simple procedure for preparing ureas directly from relevant amino acids 1a–c (Scheme 2). With the use of S(+)-á-alanine, the S(–) isomer of 1c was isolated, as found by polarimetry ([a]D 23 –8.25°, c = 2, H2O).Other ureas 1d and 1e containing 2-(N-acetyl)aminoethyl and 2-hydroxyethyl groups, respectively, were prepared according to standard procedures.8,9 Ureas 1a–e were entered into a bicyclization reaction with dihydroxyimidazolidin-2-ones 2a,b. As a result, new functional TABOD derivatives 3a–g were obtained (Scheme 3). It is interesting to note that the reaction of S(–) 1c with 2a is diastereoselective.The 1H NMR spectrum of 3e exhibits signals due to protons of two diastereoisomers. An analysis of the most informative portion of the 1H NMR spectrum (the range 4.0– 4.5 ppm of signals due to CH protons) indicated that according to integral intensities the ratio between diastereoisomers in the reaction mixture is 2:5.This ratio remained almost unchanged in the course of isolation of 3e.† Scheme 1 O NH NH R R R O R O N N HO R HO R R R O N N R R O N N R R O R R H+ O NH NH R R H+ (CH2)n H2N R OH O (CH2)n HN R OH O O NH2 i 1a n = 1, R = H 1b n = 0, R = H 1c n = 0, R = Me Scheme 2 Reagents and conditions: i, H2O, KCNO, reflux for 20 min, addition of HCl to pH 3. a R1 = H, R2 = CH2CH2COOH b R1 = H, R2 = CH2COOH c R1 = H, R2 = CH(Me)COOH d R1 = Me, R2 = CH2CH2NHCOMe e R1 = Me, R2 = CH2CH2OH a R3 = H b R3 = Me a R1 = R3 = H, R2 = CH2CH2COOH b R1 = H, R2 = CH2CH2COOH, R3 = Me c R1 = R3 = H, R2 = CH2COOH d R1 = H, R2 = CH2COOH, R3 = Me e R1 = R3 = H, R2 = CH(Me)COOH f R1 = Me, R2 = CH2CH2OH, R3 = H g R1 = R3 = Me, R2 = CH2CH2NHCOMe 1 2 3 2: 1: 3: Scheme 3 Reagents and conditions: i, H2O, pH 1, 90 °C, 1 h.O NH NH R1 R2 N N R3 R3 O N N R3 R3 O N N R1 R2 O i HO HO HN O NH OH Me HN O NH NH Me Me O 1d 1eMendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) It would be expected that not only compound 3g, but also alternative compounds 3g' and 3g'' result from the reaction between 1d and 2b. The structure of 3g was supported by 15N NMR spectroscopy.Thus, in an INEPT experiment adjusted to the direct coupling constant 15N–1H, the 15N NMR spectrum exhibited a doublet of the NH group at –266.8 ppm with the constant 1J(15N–1H) = 91.9 Hz. On the selective polarisation transfer from the protons of the MeCO group (1.72 ppm in the 1H NMR spectrum), the 15N NMR signal was observed with the same chemical shift and splitting due to direct NH coupling, J 91.9 Hz, and antiphase splitting, J 2.0 Hz, due to long-range coupling with Me protons.This is indicative of the presence of the MeCONH unit in the molecule of only compound 3g. Compounds 3a–g are of special interest as biologically active substances, and the introduced functional groups make it possible to combine TABODs with a wide variety of natural compounds.This work was supported by INTAS (grant no. 99-0157). References 1 O. V. Lebedev, L. I. Khmel’nitskii, L. V. Epishina, L. I. Suvorova, I. V. Zaikonnikova, I. E. Zimakova, S. V. Kirshin, A. M. Karpov, V. S. Chudnovskii, M. V. Povstyanoi and V. A. Eres’ko, in Tselenapravlennyi poisk novykh neirotropnykh preparatov (Directed Search for Novel Neurotropic Drugs), Zinatne, Riga, 1983, p. 81 (in Russian). 2 Uspekhi khimii v sozdanii novykh biologicheski aktivnykh soedinenii (Chemical Advances in the Development of New Biologically Active Compounds), ed. A. A. Bakibaev, Tomsk Polytechnic University, Tomsk, 1998, p. 67 (in Russian). 3 M. D. Mashkovskii, Lekarstvennye sredstva (Drugs), Meditsina, Moscow, 1993, p. 99 (in Russian). 4 H. Petersen, Text.Res. J., 1971, 41, 239. 5 H. Petersen, Synthesis, 1973, 243. 6 C. Harries and M. Weiss, Liebigs Ann. Chem., 1903, 355. 7 H. Knolker and T. Braxmeier, Synlett, 1997, 925. 8 T. L. Davis and K. C. Blachard, J. Am. Chem. Soc., 1923, 45, 1818. 9 F. Arndt, C. R. Noller and J. Georgsteinsson, Org. Synth., 1953, 15, 48. † The 1H, 13C and 15N NMR spectra of solutions in [2H6]DMSO were recorded on a Bruker AM 300 spectrometer.Chemical shifts were measured with reference to the signals of the solvent at d 2.50 ppm ([2H6]DMSO, 1H NMR) and 39.50 ppm (13C NMR) or with the use of an external standard (MeNO2, 15N NMR). The structures of new compounds were confirmed by elemental analysis. 1a: yield 96%, mp 180–182 °C. 1H NMR ([2H6]DMSO) d: 2.30 (t, 2H, CH2), 3.17 (q, 2H, CH2), 5.70 (s, 2H, NH2), 6.22 (t, 1H, NH). 1b: yield 98%, mp 193–195 °C. 1H NMR ([2H6]DMSO) d: 3.65 (d, 2H, CH2), 5.69 (s, 2H, NH2), 6.22 (t, 1H, NH). 1c: yield 84%, mp 224–226 °C. 1H NMR ([2H6]DMSO) d: 1.22 (d, 3H, Me), 4.05 (m, 1H, CH), 5.57 (s, 2H, NH2), 6.22 (d, 1H, NH), 12.0– 12.8 (br. s, 1H, COOH). 1d: yield 76%, mp 155–157 °C. 1H NMR ([2H6]DMSO) d: 1.76 (s, 3H, MeCO), 2.43 (s, 3H, Me), 3.02 (m, 4H, 2CH2), 5.48 (s, 2H, NH2), 6.01 (d, 1H, NH). 1e: yield 93%. 1H NMR ([2H6]DMSO) d: 2.48 (d, 3H, Me), 3.01 (q, 2H, CH2), 3.35 (t, 2H, CH2), 4.4 (br. s, OH), 5.05 (d, H, CH), 6.0 (br. s, 2H, 2NH). 3a: yield 58%, mp 215–217 °C. 1H NMR ([2H6]DMSO) d: 2.3–2.6 (m, 2H, CH2), 2.9–3.3 (m, 2H, CH2), 5.12 (d, 1H, CH), 5.23 (d, 1H, CH), 7.11 (s, 1H, NH), 7.20 (s, 1H, NH), 7.28 (s, 1H, NH). 3b: yield 28%, mp 187–191 °C. 1H NMR ([2H6]DMSO) d: 2.35–2.60 (m, 2H, CH2), 2.64 (s, 3H, Me), 2.83 (s, 3H, Me), 3.20–3.60 (m, 2H, CH2), 5.09 (d, 1H, CH), 5.22 (d, 1H, CH), 7.68 (s, 1H, NH), 12.2–12.4 (br. s, 1H, COOH). 3c: yield 60%, mp 273–275 °C. 1H NMR ([2H6]DMSO) d: 3.62 (d, 1H, CH2), 3.97 (d, 1H, CH2), 5.28 (s, 2H, CH–CH), 7.29 (s, 2H, 2NH), 7.51 (s, 1H, NH). 3d: yield 31%, mp 258–260 °C. 1H NMR ([2H6]DMSO): 2.66 (s, 3H, Me), 2.76 (s, 3H, Me), 3.83 (d, 1H, CH2), 4.03 (d, 1H, CH2), 5.14–5.23 (m, 2H, CH–CH), 7.90 (s, 1H, NH). 3e: yield 37%. 1H NMR ([2H6]DMSO) d: diastereomer 1: 1.38 (d, 3H, Me), 4.02 (q, 1H, CH), 5.21 (d, 1H, CH), 5.30 (d, 1H, CH), 7.19 (s, 1H, NH), 7.23 (s, 1H, NH), 7.41 (s, 1H, NH); diastereomer 2: 1.41 (d, 3H, Me), 4.31 (q, 1H, CH). 13C NMR: diastereomer 1: 14.66 (Me), 51.82 (CH), 62.68 (CH), 67.68 (CH), 158.73 (CO), 160.95 (CO), 172.05 (COOH); diastereomer 2: 15.83 (Me), 51.96 (CH), 62.80 (CH), 67.08 (CH), 159.35 (CO), 161.21 (CO), 172.38 (COOH). 3f: yield 21%, mp 142–144 °C. 1H NMR ([2H6]DMSO) d: 2.66 (s, 3H, Me), 3.05–3.25 (m, 2H, CH2), 3.46 (t, 2H, CH2), 5.21 (d, 1H, CH), 5.29 (d, 1H, CH), 7.25–7.50 (br. s, 2H, NH). 3g: yield 34%, mp 127–130 °C. 1H NMR ([2H6]DMSO) d: 1.72 (s, 3H, COMe), 2.68 (s, 3H, Me), 2.71 (s, 3H, Me), 2.75 (s, 3H, Me), 2.95– 3.15 (m, 2H, CH2), 3.28–3.42 (m, 2H, CH2), 4.78 (d, 1H, CH), 5.06 (d, 1H, CH), 7.18 (t, H, NH). 13C NMR, d: 22.15 (Me), 37.31 (CH2), 42.41 (CH2), 68.88 (CH), 71.91 (CH), 158.35 (CO), 158.76 (CO), 170.07 (CO). N N Me O N N Me Me O HN O Me N N Me Me O N NH N O Me O Me N N Me Me O N N O Me O NHMe 3g 3g' 3g'' Received: 7th July 2000; Com. 00/1683

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Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1.42) Iminophosphites as new chiral P,N-bidentate ligands Konstantin N. Gavrilov,*a Alexei I. Polosukhin,b Oleg G. Bondarev,b Andrei V. Korostylev,b Sergey E. Lyubimov,a Alexei A. Shiryaev,a Zoya A. Starikovab and Vadim A. Davankovb a Department of Chemistry, S. A. Esenin Ryazan State Pedagogical University, 390000 Ryazan, Russian Federation.Fax: +7 095 135 6471; e-mail: chem@ttc.ryazan.ru b A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 117813 Moscow, Russian Federation 10.1070/MC2001v011n01ABEH001356 The coordination of new chiral P,N-hybrid ligands possessing a phosphite-type phosphorus donor centre and azomethine nitrogen to [Rh(CO)2Cl]2 and PdCl2(cod) was examined. In the mid-1980¡�s, H.Brunner introduced chiral phosphoruscontaining ligands bearing a distant imino group . iminophosphines. 1 In the last years, such P,N-bidentate compounds were widely used in asymmetric metal complex catalysis and coordination chemistry.2.5 Although they vary in molecular structure, all iminophosphines possess identical diphenylphosphine phosphorus centres.On the other hand, increasing the P-centre ¥�-acidity of the P,N-bidentate ligand is well known to favour high chemical and optical yields in a number of catalytic reactions. The most effective way to increase the ¥�-acidity and catalytic efficiency is to replace carbon atoms in the first coordination sphere of phosphorus by oxygen and/or nitrogen atoms. Some impressive results have been already achieved this way.6.9 Hence, the inclusion of a distant imino group into a phosphorous acid ester molecule results in P,N-bidentate ligands of a new type, iminophosphites, which are promising for enantioselective catalysis.In this study, we prepared the first optically active compounds of this class based on our previous experience in developing chiral aminophosphites.9 New chiral iminophosphites 1a.c bearing a distant azomethine group have been obtained by one-step phosphorylation¢Ó of corresponding iminoalcohols¢Ô (Scheme 1).Compounds 1a.c¡× are readily soluble in organic solvents and stable on keeping dry for several months. Their complexation¢Ò leads to metal chelates with cis-oriented phosphorus and nitrogen atoms (Scheme 2).In the case of 2a.c, it is proved by n(CO), n(Rh.Cl) and 1J(P,Rh) values (Table 1), which are characteristic of chlorocarbonyl RhI complexes with chelate-forming nitrogen-containing phosphites.14 It should be added that 1J(C,Rh) values are in the range 68.75 Hz typical of cis-[Rh(CO)Cl(PN)] chelates.14 The presence of a Pd.P bond in the complexes 3a,b is proved by dP and .dP values (Table 2) typical of six-membered palladium chelates with acyclic nitrogen-containing phosphites.15 Two equally intense n(Pd.Cl) bands in the far IR region of 3a,b result from the cis-configuration of chlorine ligands and different trans-influences of phosphorus and nitrogen centres (Table 2).A comparison between the spectral data for free and coordinated iminophosphites demonstrates significant downfield coordination shifts of the resonances of carbon atoms adjacent to phosphorus (.dC 2.8 ppm) and nitrogen atoms.The azomethine carbon exhibits a large value of .dC (9.11 ppm), which is indicative of binding an imine nitrogen atom to a metal atom. Compounds 2a and 2b were isolated as single crystals and their structures were determined by X-ray diffraction studies.¢Ó¢Ó The angular distortions of the Rh coordination geometries in both 2a and 2b molecules are almost equal, a Rh atom is situated at 0.073(2) A (2a) and 0.101(2) A (2b) from the P(1)Cl(1)N(1)C(1) basal plane.The chelate metal rings exhibit asymmetrically distorted Rh(1),C(3)-boat and N(1),O(2)-boat conformations in 2a and 2b, respectively. ¢Ó General procedure. An equimolar mixture of (RO)2PNEt2 [R = (1S)- endo-(.)-bornyl,10 Pri 11] (0.01 mol) and a corresponding iminoalcohol in toluene (20 ml) was stirred under reflux for 4 h.Then, the solvent was evaporated and the residue was distilled at 0.8 mmHg (65.80% yield). [a]D 20 = .4.63 (c 2.42, CHCl3, 1a), [a]D 15 = +17.35 (c 1, CHCl3, 1b), [a]D 20 = .7.71 (c 1.2, CHCl3, 1c). ¢Ô Syntheses of the iminoalcohols {(2R)-2-[N-(benzylideneamino)]-3- methylpropan-1-ol12 and (2R)-2-[N-(p-dimethylaminobenzylideneamino)]- 3-methylbutan-1-ol, [a]D 19 = +9.82 (c 10, CH2Cl2)} are analogous to the described procedures.13 ¡× All compounds gave spectroscopic and analytical data consistent with the proposed structure. (RO)2PNEt2 HO N R1 Ar N R1 Ar O P RO RO 1a.c a R = Pri, R1 = Et, Ar = Ph Me Me b R = , R1 = Et, Ar = Ph c R = R1 = Pri, Ar = 4-Me2NC6H4 Scheme 1 Me .HNEt2 ¢Ò General procedure. A solution of 1a.c, 4 (3.6¡¿10.4 mol) in CH2Cl2 (5 ml) was added dropwise to a solution of [Rh(CO)2Cl]2 (1.8¡¿10.4 mol) or PdCl2(cod) (3.6¡¿10.4 mol) in the same solvent (15 ml) at 20 ¡ÆC with stirring. The reaction mixture was stirred at 20 ¡ÆC for 0.5 h. The excess of the solvent was then removed in a vacuum (40 mmHg), and 10 ml of hexane (in the case of 2a.c, 5) or diethyl ether (in the case of 3b,c) was added to the residue.The precipitate obtained was separated by centrifugation, washed with hexane (10 ml) or diethyl ether and dried in a vacuum (1.5 mmHg) to give a product in 80.95% yield. Table 1 Selected spectroscopic data for compounds 2a.c and 5.IR/cm.1 31P NMR 13C (CO) NMR n(CO), CHCl3 (KBr) n(Rh.Cl) CHCl3 (Nujol) dP/ppm 1J(P,Rh)/ Hz dC(CO)/ ppm 1J(C,Rh)/ Hz 2J(C,P)/ Hz 2a 2019 (1999) 289 (285) 128.20 250.9 188.42 73.76 18.16 2b 2016 (2012) 290 (294) 130.22 254.3 187.46 72.95 18.77 2c 2014 (1996) 291 (288) 129.65 255.4 187.61 72.13 18.61 5 2022 (2011) 296 (296) 128.00 264.8 185.34 71.53 20.85 Table 2 Selected spectroscopic data for compounds 3a,b.IR, n(Pd.Cl)/cm.1, CHCl3 (Nujol) 31P NMR (CDCl3) dP /ppm .dP a / ppm a.dP = dP(complex) . dP(ligand). 3a 339, 328, 298 (335, 326, 295) 76.10 .63.1 3b 344, 294 (342, 284) 76.62 .64.2Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1.42) When designing chiral P,N-bidentate ligands, not only the ¥�-acceptor ability of a phosphorus centre but also the ¥ä-donor ability of nitrogen should be taken into account.Thus, in a series of ferrocene-based phosphinopyrazoles, optical yields in Rh-catalysed hydroboration.oxidation of alkenes16,17 and in Pd-catalysed hydrosilylation.oxidation of alkenes18 increased with the electron- donor ability of a pyrazole unit. In this connection, a concept of electronically non-symmetric ligands was suggested (the higher the ¥�-acceptor ability of the P-centre and the ¥ä-donor ability of the N-centre, the more electronically asymmetric the compound).This parameter can be estimated using the value of n(CO) in the IR spectrum of the chlorocarbonyl complex [Rh(CO)Cl(PN)].17 In particular, for structurally similar complexes with identical phosphorus centres and different nitrogen centres, a compound with a lower value of n(CO) possesses a more active ¥ò-donor nitrogen-containing centre and hence is more electronically asymmetric.¢Ô¢Ô On this basis, we synthesised a Rh(I) chlorocarbonyl complex with the same P-centre as in 2b but bearing a tertiary amino group¡×¡× (Scheme 3).Selected spectral data for 5 are shown in Tables 1 and 2. Note that n(CO) (in CHCl3) for 2b is 6 cm.1 lower than that for 5 (Table 1).It indicates a higher electron-donating ability of an imino group in comparison to an amino group and, therefore, a more pronounced electronic asymmetry of iminophosphite 1b. An increase in the electron-donor ability of a nitrogen-containing unit causes a decrease of 1J(P,Rh) (Table 1). A similar behaviour was observed when the spectral parameters of 2a and its recently obtained11 analogue 5 [R = Pri, n(CO) 2022 cm.1 (CHCl3), 1J(P,Rh) 261.7 Hz (CDCl3)] were compared.¢Ó¢ÓCrystallographic data for 2a: at .80 ¡ÆC crystals of C18H are monoclinic, space group P21, a = 9.042(4), b = 8.727(4), c = = 13.904(7) A, b = 92.32(4)¡Æ, V = 1096.3(9) A3, Z = 2, M = 491.74, m(MoK¥á) = 0.995 mm.1, 2778 reflections were measured, 2567 (Rint = = 0.0443) independent reflections were used in all calculations.The final wR(F2) was 0.0883 (all data), R1(F) = 0.0327 [F, 2298 reflections with I > 2s(I)]. All hydrogen atoms (except from six atoms) were located from the difference Fourier syntheses and refined in an isotropical approximation, the hydrogen atoms in two Me groups [C(14)H3 and C(15)H3] were placed in geometrically calculated positions and included in the refinement using the rigid model approximation with the temperature factors Uiso = 1.5Ueq(C), where Ueq(C) is the equivalent isotropical temperature factor for carbon atom bonding to the corresponding hydrogen atom.Crystallographic data for 2b¡�0.25CH2Cl2: at .163 ¡ÆC crystals of C32.25H48Cl1.50NO4PRh are tetragonal, space group I4, a = 30.230(2), b = 30.230(2), c = 7.5935(5) A, V = 6939.5(7) A3, M = 700.77, Z = 8, m(MoK¥á) = 0.688 mm.1, 37077 reflections were measured, 9499 (Rint = = 0.0610) independent reflections were used in all calculations.The final wR(F2) was 0.1431 (all data), R1(F) = 0.0606 [F, 5092 reflections with I > 2s(I)]. All hydrogen atoms were placed in geometrically calculated positions and included in the refinement using the rigid model approximation with the temperature factors Uiso = 1.2Ueq(Ci) or 1.5(Cii), where Ci and Cii are sp2- and sp3-carbon atoms to which the corresponding hydrogen atom is attached.The solvate CH2Cl2 molecules are disordered over several positions in channels along a four-fold axis. Yellow crystals of 2a and 2b¡�CH2Cl2 were obtained from dichloromethane solutions by slow evaporation.A Bruker SMART (2a) or Syntex P21 diffractometer (2b¡�CH2Cl2) was used. The structures were solved using direct methods and refined by full-matrix least-squares on F2. All calculations were performed using the SHELXTL PLUS 5.0 program. Atomic coordinates, bonds 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 1135/75.C(5) C(4) C(3) Cl(1) N(1) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(1) C(2) O(1) O(2) O(3) Rh(1) P(1) O(4) Figure 1 General view of a molecule of 2a.Selected bond lengths (A): Rh(1).C(1) 1.813(6), Rh(1).N(1) 2.123(4), Rh(1).P(1) 2.186(2), Rh(1). Cl(1) 2.400(2), O(2).C(2) 1.436(7); principal bond angle (¡Æ): N(1).Rh(1). P(1) 88.02(13). L P O N Rh OC Cl Ar R1 RO RO P O N Pd Cl Cl Ph Et RO RO 1/2[Rh(CO)2Cl]2 L = 1a.c [PdCl2(cod)] L = 1a,b 2a.c 3a, b Scheme 2 .CO . cod ¢Ô¢Ô In the alkylation of dimethyl malonate with 1,3-diphenylprop-2-enyl acetate catalysed by [Pd(All)Cl]2, ligands 1a and 1c gave ee 13 (S) and 57% (S), respectively (the chemical yield is quantitative). We are grateful to R. Hilgraf (University of Basel, Switzerland) for catalytic experiments. ¡×¡× Synthesis of ligand 4 was described previously.10 P O N Rh OC Cl RO RO 1/2[Rh(CO)2Cl]2 5 Scheme 3 N O P RO RO Me Me Me Me Me Me 4 R = Me .CO C(5) C(4) C(3) Cl(1) N(1) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(1) C(2) O(1) O(2) O(3) Rh(1) P(1) O(4) Figure 2 General view of a molecule of 2b. Selected bond lengths (A): Rh(1).C(1) 1.833(7), Rh(1).N(1) 2.114(5), Rh(1).P(1) 2.164(2), Rh(1). Cl(1) 2.405(2), O(2).C(2) 1.441(7); principal bond angle (¡Æ): N(1).Rh(1).P(1) 86.1(2). C(19) C(20) C(21) C(22) C(23) C(24) C(25) C(26) C(27) C(28) C(29) C(30) C(31) C(32)Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1.42) References 1 H. Brunnel and H. Weber, Chem. Ber., 1985, 118, 3380. 2 T. Hayashi, C. Hayashi and Y. Uozumi, Tetrahedron: Asymmetry, 1995, 6, 2503. 3 H. Brunnel, I.Deml, W. Dirnberger, K.-P. Ittner, W. Rei¥âer and M. Zimmermann, Eur. J. Inorg. Chem., 1991, 51. 4 A. Saitoh, K. Achiwa and T. Morimoto, Synlett, 1999, 483. 5 H. A. Ankersmit, B. H. Loken, H. Kooijman, A. L. Spek, K. Vrieze and G. van Koten, Inorg. Chim. Acta, 1996, 252, 141. 6 J. M. Brunnel, T. Constantieux and G. Buono, J. Org. Chem., 1999, 64, 8940. 7 R. Hilgraf and A. Pfaltz, Synlett, 1999, 1814. 8 D. K. Heldmann and D. Seebach, Helv. Chim. Acta, 1999, 82, 1096. 9 K. N. Gavrilov, A. V. Korostylev, O. G. Bondarev, A. I. Polosukhin and V. A. Davankov, J. Organomet. Chem., 1999, 585, 290. 10 K. N. Gavrilov, I. S. Mikhel, K. A. Lyssenko, M. Yu. Antipin, G. I. Timofeeva, A. I. Polosukhin and A. V. Korostylev, Zh. Neorg. Khim., 1997, 42, 593 (Russ. J. Inorg. Chem., 1997, 42, 520). 11 K. N. Gavrilov, A. V. Korostylev, O. G. Bondarev, A. V. Petrovskii, K. A. Lyssenko, A. I. Polosukhin and V. A. Davankov, Izv. Akad. Nauk, Ser. Khim., 2000, 530 (Russ. Chem. Bull., 2000, 49, 533). 12 N. Heuser, M. Klein, J. Messinger, V. Buss, E. Raabe, C. Krueger, J. Chem. Soc., Chem. Commun., 1987, 945. 13 H. Brunner, I. Deml, W. Dirnberger, B. Nuber and W. Reiber, Eur. J. Inorg. Chem., 1998, 43. 14 K. N. Gavrilov, Zh. Neorg. Khim., 1997, 42, 433 (Russ. J. Inorg. Chem., 1997, 42, 368). 15 K. N. Gavrilov, A. V. Korostylev, G. I. Timofeeva, A. I. Polosukhin, O. G. Bondarev and P. V. Petrovskii, Koord. Khim., 1998, 24, 610 (Russ. J. Coord. Chem., 1998, 24, 570). 16 A. Snyder, L. Hintermann and A. Togni, Angew. Chem., Int. Ed. Engl., 1995, 34, 931. 17 A. Schnyder, A. Togni and V. Weisli, Organometallics, 1997, 16, 255. 18 A. Togni, R. Dorta, C. Kollner and G. Pioda, Pure Appl. Chem., 1998, 70, 1477. Received: 6th July 2000; Com.

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Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1.42) New derivatives of dehydroacetic acid: synthesis of 2-polyfluoroalkyl-7-methylpyrano[4,3-b]pyran-4,5-diones Vyacheslav Ya. Sosnovskikh,*a Boris I. Usachev,a Andrei G. Blinova and Mikhail I. Kodessb a Department of Chemistry, A. M. Gor¡�ky Urals State University, 620083 Ekaterinburg, Russian Federation. Fax: +7 3432 61 5978; e-mail: Vyacheslav.Sosnovskikh@usu.ru b Institute of Organic Synthesis, Urals Branch of the Russian Academy of Sciences, 620219 Ekaterinburg, Russian Federation 10.1070/MC2001v011n01ABEH001354 The condensation of dehydroacetic acid with RFCO2Et in the presence of LiH in THF afforded fluorine-containing 3-acetoacetyl- 4-hydroxy-6-methylpyrones, which underwent cyclization to 2-polyfluoroalkyl-7-methylpyrano[4,3-b]pyran-4,5-diones on treatment with concentrated sulfuric acid at room temperature.Previously,1.4 it was found that triacetic lactone and dehydroacetic acid react with acetoacetic acid esters to form pyranopyranediones 1 and 2, which are highly reactive molecules with several reaction centres.5 It is also known6.8 that aromatic aldehydes react with dehydroacetic acid, which can be considered as a heterocyclic analogue of 2-hydroxyacetophenone, to afford styrene derivatives 3, which can be transformed into ¥ã-pyrones 4 in acidic media.However, there is no published data on the reactions of dehydroacetic acid with carboxylic acid esters. To extend our studies concerning 2,3-dihydro-6-trifluoromethyl- 4-pyrones9.11 and 2-polyfluoroalkylchromones,12.14 we examined the reactions of dehydroacetic acid with the esters of fluorinated carboxylic acids for the synthesis of fluorinated analogues of 2,7-dimethylpyrano[4,3-b]pyran-4,6-dione (Praill¡�s ¥á,¥ã-bispyrone) 1.It is well known that the presence of fluorine atoms in the ¥ã-position of ¥â-diketones increases the degree of enolization.15,16 As a rule, the methylene group in fluorinecontaining ¥â-diketones 5 (R = H) cannot be detected in the 1H NMR spectra, and the diketo form appears only in the presence of a substituent at the ¥á-position (5, R = Me or Br).17 The condensation products of 2-hydroxyacetophenones with RFCO2Et (6, RF = CF3) exist only in a cyclic semiketal form18 both in solutions and in a crystalline state, whereas at RF = (CF2)2H or C2F5 they exist as a mixture of open-chain completely enolised (20%) and cyclic (80%) forms in a CDCl3 solution.19 We found that the condensation of dehydroacetic acid with RFCO2Et in the presence of LiH in THF afforded 3-polyfluoroacetoacetyl- 2-pyrones 7a.c in 70.77% yields.¢Ó Under these conditions, ethyl acetate, ethyl dichloroacetate, and ethyl trichloroacetate did not enter into this reaction. The starting dehydroacetic acid was isolated in the case of ethyl acetate, whereas resinification of the reaction mixture due to the haloform cleavage and carbene formation was observed with the other two esters.20 In contrast to ¥â-diketones 5 (R = H), the 1H NMR spectra of compounds 7a.c in a CDCl3 solution exhibited two sets of signals; one of them corresponds to ketodienol form A, and the other, to two diketoenol forms B and C, which are indistin- O O Me O O Me 1 O O O Me O Me 2 O O H O O Me 3 Ar O O Me 4 Ar Scheme 1 ¢Ó 4-Hydroxy-6-methyl-3-(4,4-difluoroacetoacetyl)-2-pyrone 7a: yield 77%, mp 133.134 ¡ÆC (ethanol). 1H NMR (250MHz, CDCl3) d: A (70%): 2.30 (d, 3H, Me, 4J 0.6 Hz), 5.98 [q, 1H, =CH(5), 4J 0.6 Hz], 6.07 (t, 1H, CF2H, 2JH,F 53.7 Hz), 7.38 [s, 1H, =CH(2')], 13.41 [br.s, 1H, HO.C(3')], 15.42 [s, 1H, HO.C(4)]; B (30%): 2.30 (s, 3H, Me), 4.20 (s, 1H, CH2), 6.02 (s, 1H, =CH), 6.03 (t, 1H, CF2H, 2JH,F 53.8 Hz), 15.46 (s, 1H, OH). 1H NMR (400 MHz, CDCl3 + [2H6]DMSO) d: D (100%): 2.29 (d, 3H, Me, 4J 0.7 Hz), 2.87 (AB system, .d 0.39 ppm, 2H, CH2, JAB 16.1 Hz), 6.05 (t, 1H, CF2H, 2JH,F 54.5 Hz), 6.20 (s, 1H, =CH), 8.71 (br.s, 1H, OH). 19F NMR (75.3 MHz, C6F6, CDCl3) d: A (70%): 36.32 (d, CF2H, 2JH,F 53.9 Hz); B (30%): 33.09 (d, CF2H, 2JH,F 53.9 Hz). IR (Vaseline oil, n/cm.1): 3315 (OH), 3105 (=CH), 1760 (O.C=O), 1645 (C=O), 1530 (C=C). Found (%): C, 48.80; H, 3.30. Calc. for C10H8F2O5 (%): C, 48.79; H, 3.28. 4-Hydroxy-6-methyl-3-(4,4,4-trifluoroacetoacetyl)-2-pyrone 7b: yield 76%, mp 130.131 ¡ÆC (ethanol). 1H NMR (250 MHz, CDCl3) d: A (80%): 2.31 (s, 3H, Me), 6.00 [s, 1H, =CH(5)], 7.53 [s, 1H, =CH(2')], 13.47 [br. s, 1H, HO.C(3')], 15.18 [s, 1H, HO.C(4)]; B (20%): 2.31 (s, 3H, Me), 4.32 (s, 1H, CH2), 6.03 (s, 1H, =CH), 15.30 (s, 1H, OH). 1H NMR (400 MHz, CDCl3 + [2H6]DMSO) d: D (100%): 2.32 (s, 3H, Me), 2.98 (AB system, .d 0.26 ppm, 2H, CH2, JAB 16.3 Hz), 6.19 (s, 1H, =CH), 9.29 (br.s, 1H, OH). 13C NMR (100MHz, CDCl3 + [2H6]DMSO) d: 20.13 (Me), 40.94 (C.3), 98.70 (C.10), 98.88 (q, C.2, 2JC,F 34.6 Hz), 99.20 (C.8), 120.72 (q, CF3, 1JC,F 285.56 Hz), 156.14 (C.7), 169.66 (C.9), 171.88 (C.5), 181.75 (C.4). IR (Vaseline oil, n/cm.1): 3310 (OH), 3100 (=CH), 1760 (O.C=O), 1645 (C=O), 1550, 1530 (C=C). Found (%): C, 45.44; H, 2.69.Calc. for C10H7F3O5 (%): C, 45.47; H, 2.67. 4-Hydroxy-6-methyl-3-[2-(2,2,3,3-tetrafluoropropionyl)acetyl]-2-pyrone 7c: yield 70%, mp 113.114 ¡ÆC (ethanol). 1H NMR (250 MHz, CDCl3) d: A (80%): 2.31 (d, 3H, Me, 4J 0.8 Hz), 5.99 [q, 1H, =CH(5), 4J 0.8 Hz], 6.04 [tt, 1H, (CF2)2H, 2JH,F 52.9 Hz, 3JH,F 4.7 Hz], 7.55 [s, 1H, =CH(2')], 13.63 [br. s, 1H, HO.C(3')], 15.21 [s, 1H, HO.C(4)]; B (20%): 2.31 (s, 3H, Me), 4.34 (s, 1H, CH2), 6.02 (s, 1H, =CH), 6.10 [tt, 1H, (CF2)2H, 2JH,F 52.5 Hz, 3JH,F 5.2 Hz], 15.37 (s, 1H, OH). 1H NMR (400MHz, CDCl3 + [2H6]DMSO) d: D (70%): 2.31 (s, 3H, Me), 3.00 (AB system, .d 0.36 ppm, 2H, CH2, JAB 16.3 Hz), 6.24 (s, 1H, =CH), 6.54 (tt, 1H, CF2CF2H, 2JH,F 51.9 Hz, 3JH,F 5.8 Hz), 9.38 (br. s, 1H, OH); A (30%): 2.29 (s, 3H, Me), 6.17 [s, 1H, =CH(5)], 6.54 (tt, 1H, CF2CF2H, 2JH,F 51.9 Hz, 3JH,F 5.8 Hz), 7.30 [s, 1H, =CH(2')]. 19F NMR (75.3 MHz, C6F6, CDCl3) d: A (80%): 24.35 (dt, CF2H, 2JH,F 52.9 Hz, 3JF,F 6.9 Hz), 37.05 (dt, CF2H, 3JH,F 4.8 Hz, 3JF,F 6.9 Hz); B (20%): 24.15 (dt, CF2H, 2JH,F 52.7 Hz, 3JF,F 7.2 Hz), 36.88 (q, CF2, 3JH,F ¡í 3JF,F 6.5 Hz). IR (Vaseline oil, n/cm.1): 3315 (OH), 3105 (=CH), 1760 (O.C=O), 1645 (C=O), 1530 (C=C).Found (%): C, 44.70; H, 2.64. Calc. for C11H8F4O5 (%): C, 44.61; H, 2.72. O Ar R RF OH O Ar R RF O OH Ar R RF O OH O RF OH R R O O RF OH 6 5 Scheme 2Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1.42) guishable on an NMR time scale because of rapid intrachelate tautomerization. It is interesting that an increase from two to three fluorine atoms in a polyfluoroacyl substituent resulted in an increase in the ketodienol A content from 70 to 80%, whereas an increase from three to four fluorine atoms left the composition of the tautomer mixture unchanged (according to 1H and 19F NMR spectra).Note that the 1H NMR spectra of compounds 7a.c exhibit no signals due to cyclic form D, which is typical of products 6 obtained from 2-hydroxyacetophenones.18,19 We believe that the observed differences in the structure of compounds 5,6 on the one hand and compounds 7a.c on the other hand (the presence of a singlet due to a CH2 group at 4.20. 4.34 ppm and the absence of signals due to cyclic form D) result from the keto.enol equilibrium B C. The rapid [1,5]H sigmatropic shift between the endo and exo cyclic enol fragments of tautomers B and C results in partial enolization of the carbonyl group attached to the ¥á-pyrone ring and hence in a decrease in the electron-acceptor effect. Thus, an increase in the electron-acceptor effect of one carbonyl group (by the introduction of fluorine atoms) is compensated by a loss at the other carbonyl group (because of the participation in tautomerization); finally, this resulted in only 70.80% enolization, as is the case in acetylacetone.15 At the same time, the equilibrium B C is responsible for a decrease in the nucleophilicity of the OH group, and a strong intramolecular hydrogen bond (a narrow singlet at 15.30.15.46 ppm) hin the conformational flexibility of the molecule. As a result, in contrast to compounds 6, cyclic form D was not detected in a CDCl3 solution.However, as judged from the appearance of a typical AB system of a CH2 group with JAB 16.1.16.3 Hz at 2.87.3.00 ppm, the equilibrium is almost completely shifted towards form D on the addition of dimethyl sulfoxide to solutions of compounds 7a,b in CDCl3. This is likely due to the rupture of intramolecular hydrogen bonds, which stabilise open forms A.C, under the action of basic dimethyl sulfoxide molecules.In the case of compound 7c, ketodienol form A (30%) was present along with cyclic form D (70%); this fact indicated that the (CF2)2H group is less capable of stabilising semiketal D.9,19 Thus, polyfluoroacyl derivatives 7a.c of dehydroacetic acid exist as either openchain forms A.C or semiketal form D depending on the nature of solvent.We also found that compounds 7a.c undergo dehydration on dissolution in concentrated sulfuric acid at room temperature to form a pyranopyranedione system, which can be described by isomeric structures 8 and 9 depending on the direction of enolization in the ring. We cannot unambiguously choose between structures 8 and 9 based on the 1H NMR spectra of dehydrated products, which exhibit a singlet or doublet of the Me group (2.37.2.39 ppm), a singlet or quartet (6.23.6.27 ppm) and a singlet (6.62.6.76 ppm) of vinyl protons.The 13C NMR spectrum of a product obtained from 7a exhibits two downfield signals at 171.80 and 168.96 ppm, which are also inadequate for deciding between ¥á- and ¥ã-pyrone carbonyls. However, the IR spectra of compounds formed from 7a.c under exposure to H2SO4 exhibit an intense absorption band at 1740.1755 cm.1, which is typical of ¥á-pyrones;21 thus, structure 8 analogous to Praill¡�s ¥á,¥ã-bispyrone 11 can be suggested.¢Ô Thus, we described the condensation of dehydroacetic acid with RFCO2Et, which is characteristic of only polyfluorinated carboxylic acid esters, as the first example of dehydroacetic acid reactions with esters.Compounds 8 are promising highly reactive RF-containing synthons. This work was supported by the Russian Foundation for Basic Research (grant no. 99-03-32960). References 1 P. F. G. Praill and A. L.Whitear, Proc. Chem. Soc., London, 1961, 112. 2 A.K.Muller, F. Raninger and E. Ziegler, Liebigs Ann. Chem., 1976, 400. 3 S. K. Talapatra, A.Basak, B. C. Maiti and B. Talapatra, Indian J. Chem., 1980, 19B, 546. 4 S. K. Talapatra, P. Pal, K. Biswas, A. Shaw, R. Chakrabarti and B. Talapatra, J. Indian Chem. Soc., 1998, 75, 590. 5 L. Crombie, D. E. Games and A. W. G. James, J. Chem Soc., Perkin Trans. 1, 1996, 2715. 6 R. H. Wiley, C. H. Jarboe and H. G. Ellert, J. Am. Chem. Soc., 1955, 77, 5102. 7 N.S.Vul¡�fson, E.V. Savenkova and L. B. Senyavina, Zh. Obshch. Khim., 1964, 34, 2743 [J. Gen. Chem. USSR (Engl. Transl.), 1964, 34, 2766]. O O H O O H Me O RF 1 2 3 4 5 6 1' 2' 3' O O H O O Me O RF A B O Me O O RF HO O 1 2 3 4 5 6 7 8 9 10 D O Me O O H O C RF O CDCl3 CDCl3 [2H6]DMSO a RF = CF2H, A:(B + C) = 70:30 b RF = CF3, A:(B + C) = 80:20 c RF = (CF2)2H, A:(B + C) = 80:20 Scheme 3 7a.c O O O RF Me O O O H O H O RF O Me O O Me O RF O H2SO4 .H2O 8a.c 9 7a.c Scheme 4 ¢Ô 2-Difluoromethyl-7-methylpyrano[4,3-b]pyran-4,5-dione 8a: yield 65%, mp 188.189 ¡ÆC (ethanol). 1H NMR (250 MHz, CDCl3) d: 2.37 (d, 3H, Me, 4J 0.5 Hz), 6.23 [q, 1H, =CH(8), 4J 0.5 Hz], 6.41 (t, 1H, CF2H, 2JH,F 53.4 Hz), 6.62 [s, 1H, =CH(3)]. 19F NMR (75.3 MHz, C6F6, CDCl3) d: 37.78 (d, CF2H, 2JH,F 53.1 Hz).IR (Vaseline oil, n/cm.1): 3090.3130 (=CH), 1755 (O.C=O), 1685, 1645, 1555 (C=O, C=C). Found (%): C, 52.77; H, 2.46. Calc. for C10H6F2O4 (%): C, 52.65; H, 2.65. 2-Trifluoromethyl-7-methylpyrano[4,3-b]pyran-4,5-dione 8b: yield 82%, mp 245.246 ¡ÆC (ethanol). 1H NMR (250 MHz, CDCl3) d: 2.39 (s, 3H, Me), 6.27 [s, 1H, =CH(8)], 6.76 [s, 1H, =CH(3)]. 1H NMR (400MHz, [2H6]DMSO) d: 2.35 (s, 3H, Me), 6.68 [s, 1H, =CH(8)], 6.99 [s, 1H, =CH(3)]. 13C NMR (100 MHz, CDCl3 + [2H6]DMSO) d: 19.97 (Me), 97.99 (C-8), 105.78 (C-10), 116.27 (C-3), 117.83 (q, CF3, 1JC,F 273.4 Hz), 148.83 (q, C-2, 2JC,F 39.2 Hz), 155.90 (C-7), 168.84 (C-9), 168.96 (C-5), 171.80 (C-4). IR (Vaseline oil, n/cm.1): 3070 (=CH), 1755 (O.C=O), 1685, 1650, 1550 (C=O, C=C). Found (%): C, 48.71; H, 1.92. Calc.for C10H5F3O4 (%): C, 48.80; H, 2.05. 2-(2,2,3,3-Tetrafluoroethyl)-7-methylpyrano[4,3-b]pyran-4,5-dione 8c: yield 94%, mp 196.197 ¡ÆC (ethanol). 1H NMR (250 MHz, CDCl3) d: 2.38 (d, 3H, Me, 4J 0.5 Hz), 6.08 [tt, 1H, (CF2)2H, 2JH,F 52.9 Hz, 3JH,F 2.8 Hz], 6.26 [q, 1H, =CH(8), 4J 0.5 Hz], 6.75 [s, 1H, =CH(3)]. 19F NMR (75.3 MHz, C6F6, CDCl3) d: 27.02 (dt, CF2H, 2JH,F 52.9 Hz, 3JF,F 3.9 Hz), 41.08 (q, CF2, 3JH,F ¡í 3JF,F 3.4 Hz).IR (Vaseline oil, n/cm.1): 3090 (=CH), 1740 (O.C=O), 1680, 1640, 1555 (C=O, C=C). Found (%): C, 47.57; H, 2.18. Calc. for C11H6F4O4 (%): C, 47.50; H, 2.17.Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) 8 N. S. Vul’fson, E. V. Savenkova and L. B. Senyavina, Izv. Akad. Nauk SSSR, Ser. Khim., 1966, 1600 (Bull.Acad. Sci. USSR, Div. Chem. Sci., 1966, 15, 1541). 9 V. Ya. Sosnovskikh and M. Yu. Mel’nikov, Zh. Org. Khim., 1998, 34, 303 (Russ. J. Org. Chem., 1998, 34, 276). 10 V. Ya. Sosnovskikh and M. Yu. Mel’nikov, Izv. Akad. Nauk, Ser. Khim., 1999, 983 (Russ. Chem. Bull., 1999, 48, 975). 11 V. Ya. Sosnovskikh, M. Yu. Mel’nikov and S. A. Pogozhikh, Izv. Akad. Nauk, Ser. Khim., 1999, 1334 (Russ. Chem. Bull., 1999, 48, 1323). 12 V. Ya. Sosnovskikh, V. A. Kutsenko and D. S. Yachevskii, Mendeleev Commun., 1999, 204. 13 V. Ya. Sosnovskikh and V. A. Kutsenko, Izv. Akad. Nauk, Ser. Khim., 1999, 817 (Russ. Chem. Bull., 1999, 48, 812). 14 V. Ya. Sosnovskikh, Yu. G. Yatluk and V. A. Kutsenko, Izv. Akad. Nauk, Ser. Khim., 1999, 1825 (Russ. Chem. Bull., 1999, 48, 1800). 15 J. L. Burdett and M. T. Rogers, J. Am. Chem. Soc., 1964, 86, 2105. 16 H. Koshimura, J. Saito and T. Okubo, Bull. Chem. Soc. Jpn., 1973, 46, 632. 17 Q. T. H. Le, S. Umetani, M. Suzuki and M. Matsui, J. Chem. Soc., Dalton Trans., 1997, 643. 18 E. Morera and G. Ortar, Tetrahedron Lett., 1981, 22, 1273. 19 V. Ya. Sosnovskikh, unpublished data. 20 W. E. Parham and E. E. Schweizer, J. Org. Chem., 1959, 24, 1733. 21 L. R. Zehnder, J. W. Dahl and R. P. Hsung, Tetrahedron Lett., 2000, 1901. Received: 3rd July 2000; Com. 00/

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年代:2001

数据来源: RSC

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Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1�C42) Hydrodechlorination of polychlorinated benzenes in the presence of a bimetallic catalyst in combination with a phase-transfer catalyst Valentina I. Simagina* and Irina V. Stoyanova G. K. Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russian Federation. Fax: +7 3832 34 3056; e-mail: simagina@catalysis.nsk.su 10.1070/MC2001v011n01ABEH001302 Bimetallic supported catalysts (Pd�CNi/C and Ni�CCu/C) in combination with a phase-transfer catalyst were found efficient and selective in the liquid-phase hydrodechlorination of polychlorinated benzenes under mild conditions.Polychlorinated aromatic compounds are carcinogenic and mutagenic chemicals, which are environmentally stable and can undergo bioaccumulation in fatty tissues.1 Presently, catalytic hydrodechlorination is a viable alternative for halogenated waste handling because hazardous materials are transformed into recyclable products in a closed system with no toxic emissions.2 Hydrodechlorination is known to be promoted by Group VIII noble metals.Polychlorinated aromatic compounds can be successfully dechlorinatied using nickel catalysts under severe reaction conditions (high temperature and high hydrogen pressure).Palladium and ruthenium catalysts make it possible to perform the dechlorination of polychlorinated aromatic compounds under mild conditions; however, they are expensive and hence cannot be used on industrial scale.3 It was found4,5 that the complete dechlorination of 1,2,4,5- tetrachlorobenzene in the presence of a Pd/C catalyst and Aliquat 336 (tricaprylylmethylammonium chloride) as a phasetransfer agent with hydrogen can be performed at atmospheric pressure.However, only isomeric o-, m- and p-dichlorobenzenes (and dibromobenzenes) can be rapidly reduced with hydrogen under mild conditions using Raney nickel.In this work, we found that efficient and inexpensive catalytic systems for the hydrodechlorination of hexachlorobenzene under mild conditions can be designed using a bimetallic (Ni�CPd/C or Cu�CNi/C) catalyst in combination with a phasetransfer agent. Mono- and bimetallic catalysts were prepared by the impregnation of a support with aqueous solutions of transition metal chlorides followed by reduction with NaBH4.The catalysts of choice are transition metals (Pd, Ni and bimetallic Pd�CNi and Ni�CCu catalysts) supported on a Sibunit carbon (C) support.6 Catalysts with the total metal (Ni, Pd, Ni + Pd or Ni + Cu) content 1.7¡Á10�C4 mol per gram of the catalyst were used. The catalysts were designated as Pd2Ni98/C and Ni92Cu8/C, where the subscripts indicate the mole ratios between the corresponding metals in the catalysts.The hydrodechlorination reactions of chlorobenzene and hexachlorobenzene were studied in a two-phase system (an aqueous 50% KOH solution and an organic isopropanol�Ctoluene phase) at 50 ¡ãC. The hydrodechlorination was performed in a thermostatically controlled glass reactor with a magnetic stirrer (700 rpm) under a constant (atmospheric) pressure of hydrogen.Hydrogen was supplied at a flow rate of about 4 cm3 min�C1. In the course of the reaction, samples of the reaction mixture were analysed by GLC on an LKhM-80 chromatograph using a 2 m¡Á3 mm stainless-steel column packed with 5% SE 30 on Chromaton N AW-DMCS, a flame-ionisation detector, and argon as a carrier gas at a flow rate of 60 cm3 min�C1.Undecane was used as an internal standard. The degree of dechlorination (X) was calculated as follows: where Ci is the molar concentration of a substance containing i chlorine atoms in the molecule and C0 is the initial concentration of hexachlorobenzene. Table 1 indicates that the reaction rate was very high in the presence of a phase-transfer agent. The Pd/C catalyst is most active among the studied catalysts.The Pd2Ni98/C bimetallic catalyst exhibits a higher activity in the hydrodechlorination than the nickel catalyst and a mixture of the monometallic catalysts with the same transition metal content as in the bimetallic catalyst. It is well known7,8 that the activity of bimetallic catalysts is a nonadditive function of the composition.Thus, the activity of a Pd�CNi/SiO2 catalyst for butadiene hydrogenation increases with the content; however, this increase is not proportional to the concentration because palladium demonstrates a strong tendency to migrate to the surface. Table 2 shows that the hydrodechlorination of hexachlorobenzene with Pd2Ni98 supported on Sibunit is effective in the Table 1 Degree of dechlorination (X) of hexachlorobenzene in the presence of mono- and bimetallic catalysts; Me4N+Cl�C (phase-transfer catalyst), T = 50 ¡ãC, 50% KOH, PH2 = 1 atm, isopropanol�Ctoluene (4:7) solvent (15 ml).Catalyst (Cat) S(C�CCl):Cat ratioa aThe substrate (S):metal (Cat) ratio was determined as the substrate amount on a basis of the C�CCl unit. bThe ratio Pd (Cat):phase-transfer catalyst is 1:200.cThe reaction was carried out without phase-transfer agents. Time/h X (%) Pd/Cb 50:1 0.5 98 Pd/Cc 50:1 0.5 18 Pd2N98 /C 10:1 1.5 98 Pd/C + Ni/C 10:1 1.5 54 Ni92Cu8 /C 10:1 5.5 50 Ni/C 10:1 6 43 100 50 0.5 1.0 1.5 1 2 3 4 5 6 7 Time/h Figure 1 Hydrodechlorination of hexachlorobenzene with Ni98Pd2/C and Me4N+Cl�C as a phase-transfer catalyst: (1) hexachlorobenzene; (2) pentachlorobenzene; (3) tetrachlorobenzene isomers; (4) trichlorobenzene isomers; (5) dichlorobenzene isomers; (6) chlorobenzene; and (7) benzene.Concentration (%) X = (1 �C¦�iCi/6C0)¡Á100% i = 0 6 Table 2 Degree of dechlorination (X) of hexachlorobenzene in the presence of alkylammonium salts; catalyst, Pd2Ni98/C; S(C�CCl):Cat ratio, 10:1; T = 50 ¡ãC; 50% KOH; PH2 = 1 atm; solvent, isopropanol�Ctoluene, 4:7 (15 ml).Phase-transfer catalyst Time/h X (%) Me4N+Cl�C 1.5 98 Et4N+Cl�C 1.5 85 Et4N+OH�C 4.0 94 (C8H17)3MeN+Cl�C 1.5 90Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) presence of alkylammonium chlorides as phase-transfer catalysts. Different selectivity patterns were obtained with the use of various metal catalysts.The reaction of hexachlorobenzene with hydrogen catalysed by Pd2Ni98/C at atmospheric pressure resulted in dehalogenation via the rapid replacement of chlorine atoms in polychlorinated benzenes to form benzene (Figure 1). Figure 2 shows that dehalogenation with hydrogen at atmospheric pressure in the presence of a Ni92Cu8/C catalyst proceeds only to the formation of trichlorobenzene isomers.Thus, a proper combination of metal catalysts can affect selectivity of halogen removal. In conclusion, note that these results show the possibility of designing active bimetallic catalysts and catalytic processes for the hydrodechlorination of environmentally problematic compounds. Such reactions are also a very promising means for the selective removal of halogens from aromatic compounds in organic synthesis. This work was supported by the Russian Foundation for Basic Research (grant nos. 96-15-97557 and 93-03-32159a). References 1 W. J. Hayes and E. R. Laws, Handbook of Pesticide Toxicology, Academic Press, San Diego, 1991. 2 B. F. Hagh and D. T. Allen, Chem. Eng. Sci., 1990, 45, 2695. 3 L. N. Zanaveskin, V. A. Aver’yanov and Yu. A. Treger, Usp. Khim., 1996, 65, 667 (Russ.Chem. Rev., 1996, 65, 617). 4 C. A. Marques, O. Rogozhnikova, M. Selva and P. Tundo, J. Mol. Catal., 1995, 96, 301. 5 C. A. Marques, M. Selva and P. Tundo, J. Chem. Soc., Perkin Trans. 1, 1993, 529. 6 Yu. I. Yermakov, V. F. Surovikin, G. V. Plaksin and V. A. Likholobov, React. Kinet. Catal. Lett., 1986, 23, 435. 7 I. F. Faudon, F. Senocq, G. Bergeret, B. Moraweck, G. Clugnet, C. Nicot and A. Renouprez, J. Catal., 1993, 144, 460. 8 A. Renouprez, J. F. Faudon, J. Massardier, J. L. Rousset and G. Bergeret, J. Catal., 1997, 170, 181. 100 50 2 4 6 Time/h 1 2 3 4 Figure 2 Hydrodechlorination of hexachlorobenzene with Ni92Cu8/C and Me4N+Cl– as a phase-transfer catalyst: (1) hexachlorobenzene; (2) pentachlorobenzene; (3) 1,2,4,5-tetrachlorobetion (%) Received: 17th March 2000; Com. 00/1628

ISSN:0959-9436     

出版商:RSC    

年代:2001

数据来源: RSC

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Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) Structure of detonation nanodiamonds Alexander L. Vereshchagin*a and Gennady V. Sakovichb a Biysk Technological Institute, I. I. Polzunov Altay State Technical University, 659305 Biysk, Russian Federation. Fax: +7 3854 25 2486; e-mail: val@bti.secna.ru b ‘Altay’ Federal Research and Production Centre, 659322 Biysk, Russian Federation 10.1070/MC2001v011n01ABEH001275 Nanoparticles of diamond were formed from detonations, and density and other measurements indicate they are hollow.The most likely explanation is that they condensed from liquid carbon which is less dense than diamond. In contrast to other synthetic diamonds, the particles of superdispersed diamonds are characterised by a round shape with diameter 4 nm.1,2 Weathers and Bassett3 described the formation of spherical diamond particles from 5 to 1000 nm in diameter in the course of melting graphite and diamond at high pressures.The samples of dispersed diamonds as a mixture with sodium chloride were placed between diamond anvils and heated by laser radiation. Round-shaped particles up to 100 nm in size were formed by detonation of a mixture of carbon with cyclotrimethylenetrinitramine4 or by pulse heating of graphite particles mixed with a metal.5 The density of superdispersed diamonds is about 3.1–3.3 g cm–3,6–9 whereas natural and synthetic diamonds have densities approximately equal to a theoretical value of 3.515 g cm–3.Therefore, we examined the structure of superdispersed diamonds.According to our experimental data, the X-ray powder diffraction pattern of superdispersed diamonds exhibits only five reflections with a changed distribution of relative intensities: (111) 85.0% {44}, (220) 14.0% {22}, (113) 0.5% {18}, (400) 0.3% {4}, (331) 0.2% {12} (the relative values of a share of reflections for a standard diamond sample on ASTM Index 6-675 are given in braces).The crystal lattice parameter is 0.3562±0.0004 nm, whereas it is equal to 0.3567 nm for natural diamond. These data suggest that the theoretical density of the nanodiamonds is 3.527 g cm–3. However, the helium pycnometric density is as low as 3.05–3.10 g cm–3. The heating of superdispersed diamonds in inert atmospheres for 2 h affected their density (Table 1). The maximum density of nanodiamonds (3.21 g cm–3) was achieved by heating in an argon atmosphere up to 1073 K (similar values were reported6–9 for superdispersed diamonds after different treatments).Note that the theoretical density10 of liquid carbon is 3.2191 g cm–3. A difference between the theoretical (X-ray) and experimental (helium pycnometry) densities can be explained, if we suppose that diamond was formed through a liquid phase in all of the above explosive processes.Melted diamond has a greater molar volume than that of the equilibrium solid phase.11,12 Because of this, cavities will be formed in the crystallization of melted diamond particles upon external cooling (as is the case, for example, in the crystallization of liquid aluminum oxide on the combustion of aluminum particles13).It is reasonable to believe that hollow spheres will be formed in rapid crystallization of liquid particles of diamond at high temperature and pressure gradients. To evaluate the sizes of these cavities, we used helium pycnometric density data. This estimation is rough because of the experimental error (±0.001 g cm–3) and the presence of oxidised carbon groups at the surface of superdispersed diamonds.Let us assume that this distinction is caused by the presence of spherical cavities in superdispersed diamond particles 4 nm in size (note that the density of superdispersed diamonds is 3.21 g cm–3 and the density of natural diamond is 3.515 g cm–3). Then, the volume of cavities was calculated to be 1 – 3.21/3.515 = = 0.087 or 8.7%.For a particle 4 nm in diameter (volume of 33.493 nm3), the volume of a cavity is 2.913 nm3, which corresponds to a sphere 1.77 nm in diameter. Similar calculations based on the X-ray density of superdispersed diamonds (3.527 g cm–3) gave the diameter of an internal sphere equal to 1.79 nm. Thus, the average wall thickness is 1.10 nm, which is somewhat longer than seven C–C bond lengths (0.154 nm).It is well known that the maximum particle size of superdispersed diamonds prepared by benzotrifuroxane (C6N6O6) detonation is 31 nm.14 In this case, the diameter of an inner sphere and the wall thickness were calculated to be 13.74 and 8.7 nm, respectively; the latter value corresponds to 56 C–C bond lengths (for the pycnometric density of superdispersed diamonds 3.21 g cm–3).Thus, we may believe that, as distinct from fullerenes, diamond spheres formed as a result of solidification exhibit variable structure. The following characteristic properties of superdispersed diamonds can be explained by the presence of these internal cavities: (1) The presence of only five reflections with a changed distribution of relative intensities in the X-ray diffraction patterns of superdispersed diamonds.(2) The absence of high-order reflections from the X-ray diffraction patterns.15 (3) The apparent presence of a high volumetric fraction of an amorphous phase of diamond in superdispersed diamonds (up to 70%)6 (the part of a sphere through which X-rays pass perpendicularly to the surface appears as a phase amorphous to X-rays, and the part through which radiation passes at a tangent to the surface, as a crystalline phase).(4) A lower heat conductivity of composite materials based on superdispersed diamonds as compared with materials containing the same mass fraction of synthetic diamonds of static synthesis.16 This can also explain unsuccessful attempts to obtain samples of superdispersed diamonds of a higher density by removal of nondiamond carbon species from the surface of superdispersed diamonds via gradual oxidation of carbon9 and a constant density of superdispersed diamonds (3.05 g cm–3) after shockwave sintering,17 as well as the explosion of such diamonds after laser irradiation18 (statically synthesised diamonds did not explode under these conditions).In the 13C NMR spectra, the chemical shift of superdispersed diamonds is 34.5 ppm,15 whereas the corresponding values for diamonds of static synthesis and natural diamonds are 40 and 50 ppm, respectively.19 Thus, superdispersed diamonds exhibit a difference from other diamond species.Table 1 Pycnometric densities of superdispersed diamonds after heating in inert atmospheres. Temperature/K Pycnometric density/g cm–3 Atmosphere Ar H2 CO2 473 3.05 3.07 3.09 573 2.99 3.02 3.11 673 3.10 3.11 3.03 773 3.00 3.05 3.00 873 3.02 3.07 3.03 973 3.03 3.11 3.03 1073 3.21 3.15 2.99 1173 3.08 3.06 3.02 1273 3.09 3.03 3.09Mendeleev Communications Electronic Version, Issue 1, 2001 (pp. 1–42) It may be expected that cavities will be present in diamond particles prepared through a liquid phase of carbon by other methods such as detonation of carbon with cyclotrimethylenetrinitramine (in this case, the density was 3.15–3.25 g cm–3)20 and pulse heating of carbon mixtures with a metal.5 It is likely that in experiments21 on laser melting of diamond particles under conditions of a sharp decrease in the pressure and temperature (as is the case in detonation methods) hollow diamond particles rather than continuous fullerene structures 200 nm in size may be formed.Probably, diamonds formed in space explosions will also exhibit such a hollow structure.22 It may also be expected that the density of melted diamond will be 3.21–3.25 g cm–3. The lower density of the majority of superdispersed diamond samples can be explained by an additional contribution from dissolved gases to the volume of a formed cavity and by a fractal structure resulting from closed pores which were formed on the consolidation of separate liquid carbon particles.The volume of closed cavities can be estimated from the following relationship between the specific volumes of solid diamond and liquid carbon phases: where r and r1 are the densities of superdispersed diamonds and a liquid carbon phase, which are equal to 3.05 and 3.22 g cm–3, respectively, and Vc is the volume of closed cavities.Hence, it follows that Vc = 1.7×10–5 m3 kg–1. References 1 A. M. Staver, N. V. Gubareva, A. I. Lyamkin and E. A. Petrov, Fiz. Goreniya Vzryva, 1984, 20 (5), 100 (in Russian). 2 N. R. Greiner, D. S. Phillips, J. D. Johnson and F. Volk, Nature, 1988, 333, 440. 3 M. S. Weathers and W. A. Bassett, Phys. Chem. Minerals, 1987, 15, 105. 4 K. Yamada and A. B. Sawaoka, Carbon, 1994, 32, 665. 5 J. Kleiman, R. B. Heinmann, D. Hawken and N. M. Salansky, J. Appl. Phys., 1984, 56, 1440. 6 G. M. Gryaznov, E. A. Ekimov and V. P. Philonenko, in Fizikokhimiya ul’tradispersnykh sistem (Physics and Chemistry of Superdispersed Systems), Moscow Eng.Phys. Inst., Moscow, 1999, p. 318 (in Russian). 7 E. E. Lin, S. A. Novikov, A. B. Glushak, S. V. Koritskaya, V. G. Kuropatkin, A. N. Malyshev, V. A. Medvedkin, V. I. Skokov, V. I. Sukharenko, N. A. Yukina, V. D. Blank, G. A. Dubitskii and E. E. Semenova, in Fizikokhimiya ul’tradispersnykh sistem (Physics and Chemistry of Superdispersed Systems), Moscow Eng. Phys. Inst., Moscow, 1999, p. 289 (in Russian). 8 E. E. Lin, S. A. Novikov, V. I. Sukharenko, E. V. Levakov, V. D. Blank, G. A. Dubitski and V. M. Prokhorov, in Fizikokhimiya ul’tradispersnykh sistem (Physics and Chemistry of Superdispersed Systems), Moscow Eng. Phys. Inst., Moscow, 2000, p. 313 (in Russian). 9 K. S. Baraboshkin, T. M. Gubarevich and V. F. Komarov, Kolloidn. Zh., 1992, 54 (6), 9 (Colloid J., 1992, 54, 832). 10 A. M. Molodets, M. A. Molodets and S. S. Nabatov, Fiz. Goreniya Vzryva, 1999, 35 (2), 81 (in Russian). 11 M. Thiel and F. H. Ree, in Shock Compression of Condensed Matter, eds. S. C. Schmidt, J. N. Johnson and L. M. Davison, Elsevier, Amsterdam, 1990, p. 165. 12 F. P. Bundy, W. A. Bassett, M. S. Weathers, R. J. Hemley, H. K. Mao and A. F. Goncharov, Carbon, 1996, 34, 141. 13 S.-C. Wong and S. R. Turns, Combust. Sci. Technol., 1989, 66, 75. 14 V. F. Anisichkin, D. S. Dolgushin and E. A. Petrov, Fiz. Goreniya Vzryva, 1995, 31, 109 (in Russian). 15 A. L. Vereshchagin, G. V. Sakovich, V. F. Komarov and E. A. Petrov, Diamond Relat. Mater., 1993, 3, 160. 16 G. V. Sakovich, E. A. Petrov, V. F. Komarov and N. V. Kozyrev, in Conversion Concepts for Commercial Applications and Disposal Technologies of Energetic Systems. NATO ASI Series, ed.H. Krause, Kluver Academic Publishers, Amsterdam, 1997, p. 55. 17 D. S. Dolgushin, V. F. Anisichkin and V. F. Komarov, Fiz. Goreniya Vzryva, 1999, 35, 143 (in Russian). 18 R.-W. Lin, C. L. Cheng and H. C. Chang, Chemistry of Materials, 1999, 10, 1735. 19 H. L. Retcofsky and R. A. Fridel, J. Phys. Chem., 1973, 77, 68. 20 G. A. Adadurov, T. V. Bavina, O. N. Breusov, V. N. Drobyshev, M. J. Messinev, A. I. Rogacheva, A. V. Ananiin, V. N. Appolonov, A. N. Dremin, V. N. Doronin, F. I. Dubovitsky, L. G. Zemlyakova, S. N. Pershin and V. F. Tatsy, US Patent, no. 4483836, 1984. 21 W. A. Bassett and M. S. Weathers, in Proc. Joint Intern. Ass. Res. Adv. High Pressure Sci. Technol., eds. S. C. Schmidt, J. W. Shaner, G. A. Samara and M. Ross, AIP Press, AIP Conf. Proc. 309, Colorado 1993, part 1, p. 651. 22 S. E. Haggerty, Science, 1999, 285, 851. 1/r = 1/r1 + Vc, Received: 7th February 2000; Com. 00/1601

ISSN:0959-9436     

出版商:RSC    

年代:2001

数据来源: RSC