摘要:

O RO O 1 R = H 2 R = SO3H O HO HO CO2H OH O O O 3 O RCO2 RCO2 CO2Me X RCO2 O AcO AcO CO2Me AcO O RO RO CO2Me RO R O O O 4 R = Me, X = Br 6 R = Me, X = I 8 R = But, X = Br 7 R = b-OAc 10 R = a/b-OH 11a R = a-OC 11b R = b-OC ( NH)CCl3 ( NH)CCl3 5 R = Ac 9 R = ButCO O HO HO NaO2C OH O OH CO2Na 12 370 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 370–371† Intermediates for Glucuronide Synthesis: 7-Hydroxycoumarin Glucuronide† Richard T. Brown,a Feodor Scheinmannb and Andrew V.Stachulski*b aDepartment of Chemistry, The University of Manchester, Oxford Rd., Manchester M13 9PL, UK bSalford Ultrafine Chemicals and Research Ltd., Synergy House, Guildhall Close, Manchester Science Park, Manchester M15 6SY, UK A convenient synthesis of the important metabolite 7-hydroxycoumarin glucuronide 3 is presented, including a first report of the b-imidate 11b, together with new preparations of the iodosugar 6 and a-imidate 11a: stability data on 11a and 11b are also given, and the importance of carefully controlled hydrolysis in the last step of the preparation of 3 is emphasised. Coumarin is nowadays a ubiquitous additive to many foods and cosmetic products:1 it is therefore important that its in vivo metabolic products should be available as analytical standards.The major phase 1 metabolic process in humans is cytochrome P-450 mediated hydroxylation to 7-hydroxycoumarin 1; subsequent conjugation steps lead to the finally eliminated products, namely the sulfate 2 and glucuronide 3.Indeed, the production of 3 is regarded as a valuable test of the metabolic viability of liver slices.2 We are aware of only one literature synthesis of 3, namely phase-transfer-catalysed reaction of 1 with the bromosugar 4 followed by removal of protecting groups (6.5% overall).2 We now describe a greatly improved synthesis of 3 using imidate methodology3 together with new chemistry of the glucuronate intermediates, especially a first report of a b-imidate in the acyl glucuronate series.Under a variety of conditions,2,4,5 reaction of 4 with 1 gave no better than 10% of the conjugate 5. The iodosugar 6, conveniently prepared in fair yield directly from the b-tetraester 74 by treatment with BF3 .Et2O and KI in acetonitrile at reflux, rather than by halogen exchange on 4,6 gave a faster reaction but no better yield. Undoubtedly the low stabilities of 4 and 6 under the reaction conditions are a major problem, and indeed the pivaloyl bromosugar 8 described by Snatzke7 gave a 30% yield of the corresponding conjugate 9 using the lithium phenolate method.5 However, it then proved impossible to remove the protecting groups without irreversibly opening the lactone.Finally, trimethylsilyl trifluoromethanesulfonate- mediated reaction8 of 7 with 1 gave no reaction in dichloromethane and only 7-acetoxycoumarin in acetonitrile. Such ‘acyl transfer’ is thought to arise from an orthoester intermediate9 and in our experience is rather facile with acyl glucuronates in MeCN, making this a poor glucuronidation solvent.However, the imidate method worked very well. The required hemiacetal 10 has been obtained in various ways10–12 from the bromosugar 4 or tetraester 7; condensation of 10 (a 5:1 a:b mixture) with 7-hydroxycoumarin under Mitsunobu conditions13 gave a modest (20%) yield of 5. This is generally a viable procedure for relatively acidic phenols.It was known in the glucose series that base-catalysed reaction of hemiacetals like 10 with trichloroacetonitrile could be tuned to give either the a- or b-imidate through the operation of what Schmidt has termed the ‘kinetic’ anomeric effect.14,15 Previously only the a-anomer 11a was known in the acyl glucuronate series:16 here, using K2CO3 (rather than NaH as previously) in CH2Cl2, it was obtained in 81% recrystallised yield. Using a still weaker base, however, significant amounts of 11b were detected (TLC, NMR); brief treatment with NaHCO3 in MeCN gave 11b as the major product, and it could be isolated in 30% yield free of 11a by virtue of its lower solubility.Concern expressed over the likely stabilityof imidates such as 11a appears exaggerated.16a Crystalline 11a is stable for months at 20 °C under desiccation and shows no significant degradation over three weeks in NMR-grade CDCl3 solution. Anomer 11b is much less stable, and after a few days in CDCl3 is largely decomposed, giving mainly 10 with other more complex products.Using BF3 .Et2O catalysis in CH2Cl2, 11a and freshly prepared 11b couple equally well to 7-hydroxycoumarin: 5 has been thus obtained in 61% yield. Neither ZnBr2 nor MgBr2, which are effective catalysts in similar glucose examples,17 work here. Finally, we note that the hydrolysis of 5 to give 3 requires great care, for even a slight excess of base leads to irreversible lactone opening, giving 12 (NMR shows J 13.5 Hz, consistent with an E-olefin).It is safest to treat 5 with Na2CO3 in aqueous MeOH at 20 °C for 3 h, followed by acidification to pH 6; highly pure 3 can then be isolated at its sodium salt in 70% yield. This procedure also lessens the risk of generating any 4,5-didehydroglucuronide, a known elimination by-product from such hydrolyses.18 *To receive any correspondence (e-mail: info@ultrfine.u-net.com). †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J.Chem. Research (S), 1997, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M).J. CHEM. RESEARCH (S), 1997 371 Experimental For general procedures, see the previous paper from these laboratories.19 Methyl 1-Deoxy-1-iodo-2,3,4-tri-O-acetyl-b-D-glucopyranuronate 6.·Methyl 1,2,3,4-tetra-O-acetyl-b-D-glucopyranuronate 74 (0.38 g, 1 mmol) was stirred and heated under argon with potassium iodide (0.33 g, 2 mmol) and boron trifluoride–diethyl ether (0.23 cm3) in anhydrous acetonitrile (5 cm3) at gentle reflux for 2 h.The cooled mixture was poured onto ice-cold satd. aq. NaHCO3 and extracted with ethyl acetate (2Å), then the combined organic phases were washed with 5% aq. sodium thiosulfate, satd. aq. NaHCO3 and water. Evaporation gave an orange gum (0.335 g) which was chromatographed, eluting with 10% ethyl acetate–hexane, then 20% and finally 50%: appropriate fractions were pooled and evaporated to give the iodosugar 6 (0.145 g, 32%) as a white solid, mp 108–110 °C (decomp.) (Found: C, 35.2; H, 3.9.C13H17IO9 requires C, 35.1; H, 3.8%); dH 2.10, 2.11, 2.14 (9 H, 3 s, 3ÅCH3CO), 3.81 (3 H, s, CH3O), 4.28 (1 H, dd, 2-H), 4.42 (1 H, d, 5-H), 5.32, 5.57 (2 H, 2 d, 3-H+4-H) and 7.07 (1 H, d, J 4, 1-H); m/z (CI; NH3) 462 (MNH4 +). Methyl [1-(2-Oxo-2H-benzopyran-7-yl)-2,3,4-tri-O-pivaloyl-b-Dglucopyran] uronate 9.·Methyl 1-bromo-1-deoxy-2,3,4-tri-O-pivaloyl- b-D-glucopyranuronate7 8 (0.45 g, 0.86 mmol) was added to a stirred solution of 7-hydroxycoumarin 1 (0.16 g, 1 mmol) in methanol (2 cm3) containing lithium hydroxide hydrate (0.042 g, 1 mmol).Tetra-n-butylammonium bromide (0.050 g) was added; after 7 days at 20 °C, TLC (EtOAc–hexane, 1:1) showed appreciable conversion into a less polar spot, and treatment with sodium iodide and/or heating to 50 °C had little further effect. The mixture was diluted with ethyl acetate, washed with 10% aq.sodium carbonate (2Å), 10% aq. sodium thiosulfate and water and evaporated to a residue (0.370 g) which was chromatographed, eluting with 25% ethyl acetate –hexane, then 33%. Evaporation of appropriate fractions gave the ester 9 (0.154 g, 30%), mp 187–189 °C (Found: C, 61.8; H, 6.8. C31H40O12 requires C, 61.6; H, 6.6%); dH 1.15–1.25 (27 H, 2 s, 3ÅMe3C), 3.79 (3 H, s, CH3O), 4.31 (1 H, d, 5p-H), 5.25 (1 H, d, 1p-H), 5.35–5.55 (3 H, m, 2p-H+3p-H+4p-H), 6.36 (1 H, d, 3-H), 6.90–7.00 (2 H, m, 5-H+6-H), 7.45 (1 H, d, 8-H) and 7.70 (1 H, d, 4-H); m/z (CI; NH3) 622 (MNH4 +). Methyl 2,3,4-Tri-O-acetyl-1-O-(trichloroacetimidoyl)-a-D-glucopyranuronate 11a.·A solution of methyl 1-hydroxy-2,3,4-tri- O-acetyl-a,b-D-glucopyranuronate 1010–12 (1.67 g, 5 mmol) in anhydrous dichloromethane (25 cm3) and trichloroacetonitrile (3.6 cm3) was stirred at 20 °C with potassium carbonate (3.8 g).After 16 h the reaction mixture was filtered through a silica pad, eluting with diethyl ether, then 1:1 ethyl acetate–hexane.Appropriate fractions were pooled and evaporated, then the residue was recrystallised from ethyl acetate–hexane to give the imidate 11a (1.93 g, 81% in two crops), mp 109–110 °C (lit.,16a 108 °C). Methyl 2,3,4-Tri-O-acetyl-1-O-(trichloroacetimidoyl)-b-D-glucopyranuronate 11b.·A solution of the 1-hydroxysugar 10 (0.84 g, 2.5 mmol) in HPLC-grade acetonitrile (10 cm3) and trichloroacetonitrile (2.50 cm3) was stirred with sodium hydrogen carbonate (0.42 g, 5 mmol) over 4 Å molecular sieves at 20 °C. After 3 h the mixture was stored at 0 °C for 1 h, then diluted with diethyl ether and washed with water.The aqueous phase was again extracted with diethyl ether, then the combined extracts were washed with water and evaporated to a yellow gum which was triturated with diethyl ether–hexane; the resulting white crystals were isolated and recrystallised from ethyl acetate–hexane to give the imidate 11b (0.36 g, 30% in two crops), mp 153–154 °C (Found: C, 37.9; H, 3.8; N, 2.8.C10H15Cl3NO10 requires C, 37.6; H, 3.8; N, 2.9%); dH 2.08, 2.10 (9 H, 2 s, 3ÅCH3CO), 3.80 (3 H, s, CH3O), 4.31 (1 H, m, 5-H), 5.35–5.45 (3 H, m, 2-H+3-H+4-H), 5.98 (1 H, d, J 7.5, 1-H) and 8.82 (1 H, br s, NH). The spectrum was complicated by virtual coupling, but irradiation at d 5.4 collapsed the 5-H to a singlet. Methyl [1-(2-Oxo-2H-1-benzopyran-7-yl)-2,3,4-tri-O-acetyl-b-Dglucopyran] uronate 5.·Boron trifluoride–diethyl ether (0.030 cm3) was added at µ15 °C to a stirred suspension of 7-hydroxycoumarin 1 (0.16 g, 1 mmol) and imidate 11a (0.48 g, 1 mmol) in dichloromethane (5 cm3) which had previously been stirred under argon at 20 °C for 2 h over freshly baked 4 Å molecular sieves. After 1.25 h, when the temperature had been allowed to rise to +5 °C, the mixture was re-cooled to µ10 °C and further catalyst (0.030 ml) was added, stirring being then continued for 16 h while the mixture regained ambient temperature. Ethyl acetate (25 cm3) was added, then the solution was washed with satd. aq.NaHCO3 (3Å), water and evaporated. Chromatography on silica, eluting with from 30 to 70% ethyl acetate in hexane, afforded on evaporation of appropriate fractions a semi-solid which on crystallisation from methanol gave in two crops the ester 5 (0.292 g, 61%), mp 192–193 °C (lit.,2 185.5–187.5 °C). 1-(2-Oxo-2H-1-benzopyran-7-yl)-b-D-glucopyranosiduronic Acid 3.·A suspension of ester 5 (0.400 g, 0.84 mmol) in methanol (12 cm3) was stirred at 20 °C with a solution of anhydrous Na2CO3 (0.238 g, 2.24 mmol) in water (5 cm3).After 5 h water (6 cm3) was added, followed by addition of glacial AcOH to pH 6.2, then the product was precipitated by addition of ethanol (25 cm3). The resultant solid was filtered off and recrystallised from aq. EtOH to afford the glucuronide 3 as its sodium salt (0.21 g, 70%), mp 295–296 °C (decomp.) [lit.,2 282–287 °C (decomp.)].We are most grateful to Drs S. Mayalarp and K. W. Lumbard for skilled experimental assistance. Received, 9th June 1997; Accepted, 25th June 1997 Paper E/7/03997B References 1 R. O’Kennedy and R. D. Thornes, Coumarins: Biology, Applications and Mode of Action, Wiley, Chichester, 1997. 2 J. S. Walsh, J. E. Patanella, K. A. Halm and K. L. Facchine, Drug Metabl. Dispos., 1995, 23, 869. 3 R. T. Brown, S. P. Mayalarp, A. T. McGown and J. A. Hadfield, J. Chem. Res.(S), 1993, 496 and references cited therein. 4 G. N. Bollenback, J. W. Long, D. G. Benjamin and J. A. Lindquist, J. Am. Chem. Soc., 1955, 77, 3310. 5 B. Berrang, C. E. Twine, G. L. Hennessee and F. I. Carroll, Synth. Commun., 1975, 5, 231. 6 P. M. Collins and R. J. Ferrier, Monosaccharides, Wiley, Chichester, 1995. 7 J. Vlahov and G. Snatzke, Liebigs Ann. Chem., 1983, 570. 8 T. Ogawa, K. Beppu and S. Nakabayashi, Carbohydr. Res., 1981, 93, C6. 9 Ref. 6, pp. 157–159. 10 N. Pravdic and D. Keglevic, J. Chem. Soc., 1964, 4633. 11 L. F. Tietze and R. Seele, Carbohydr. Res., 1986, 148, 349. 12 A. Nudelman, J. Herzig, H. E. Gottlieb, E. Keinan and J. Sterling, Carbohydr. Res., 1987, 162, 145. 13 G. T. Badman, D. V. S. Green and M. Voyle, J. Organomet. Chem., 1990, 388, 117. 14 R. R. Schmidt, J. Michel and M. Roos, Liebigs Ann. Chem., 1984, 1343. 15 R. R. Schmidt and W. Kinzy, Adv. Carbohydr. Chem. Biochem., 1994, 50, 21 (review). 16 (a) B. Fischer, A. Nudelman, M. Ruse, J. Herzig, H. E. Gottlieb and E. Keinan, J. Org. Chem., 1984, 49, 4988; (b) J. C. Jacquinet, Carbohydr. Res., 1990, 199, 153; (c) P. N. Rao, A. M. Rodriguez and D. W. Miller, J. Steroid Biochem., 1986, 25, 417. 17 F. J. Urban, B. S. Moore and R. Breitenbach, Tetrahedron Lett., 1990, 31, 4421. 18 M. Adamczyk, Y.-Y. Chen and J. R. Fishpaugh, Org. Prep. Proced. Int., 1992, 24, 546. 19 A. V. Stachulski, D. E. Nichols and F. Scheinmann, J. Chem. Res. (S), 1996, 30.

ISSN:0308-2342    

DOI:10.1039/a703997b

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

374 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 374–375† Effect of Cation Capture by Crown Ether and Polar Solvent in the Carboxylation with CO2 of Alkali Metal 2-Naphtholates under Ordinary Conditions† Joseph Baxter and Tatsuaki Yamaguchi* Department of Industrial Chemistry, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino-shi, Chiba 275, Japan An efficient method for the carboxylation of sodium 2-naphtholate and potassium 2-naphtholate in benzene with 10 mol% of crown ether or aprotic polar solvents under 1 atm of carbon dioxide at 60 °C affords 2-hydroxynaphthalene-1-carboxylic acid in yields ranging from 14.6 to 43.8% and 26.7 to 66.0%, respectively.A useful process for the carboxylation of alkali metal 2- naphtholates has been developed based on the principles of crown ether chemistry. Crown ethers have been exhaustively studied in the last 25 years.1–3 These macrocyclic ligands are well known for their superb selectivity towards metal ions.4,5 This modified carboxylation procedure occurs at a reasonable temperature and carbon dioxide pressure and is practical for the manufacturing of 2-hydroxynaphthalene-1-carboxylic acid (2-H-1-NA), which is useful as a chemical intermediate for dyes, heat-sensitive dyes, photographic materials, liquid crystals, chemical feedstock, etc.It is well known that carboxylation of alkali metal naphtholates can be carried out under normal temperatures and pressures because a polar solvent is used.6–9 However, we found that benzene together with a small amount of crown ether or polar solvent, which creates a homogeneous solution, could be used instread. Our reaction in essence is similar to the alkylation reaction of potassium phenoxide with butyl bromide using various crown ethers,10 however only a 10 mol% of crown ether is needed.The reaction readily occurs at atmospheric pressure and at 60 °C for the carboxylation of potassium 2-naphtholate and sodium 2-naphtholate to give high selectivity and a relatively high yield of 2-H-1-NA.These solvation effects were clarified because crown ethers were used to separate the metal cation from the naphtholate anion, thereby increasing the charge of the free naphtholate anion, creating a homogeneous solution, and making a stronger nucleophilic reagent. Similar results were found using at trace amount of polar solvents, which solvate the potassium ion creating a solvent-separated ion-pair.The results are shown in Table 1, and the yields were calculated after purification. The highest yields were achieved using the aliphatic crown ethers as compared to the other crown ethers because the oxygen basicity of the aliphatic crown ethers is higher than that of the aromatic-containing crown ethers. An increase in the basicity of the crown ether increases both its solvating and chelating ability.11 To support our proposal that the solvation and/or removal of the cation is necessary in benzene, polar aprotic solvents (0.001 mol) were added to the carboxylation reaction without the use of a crown ether (Table 2).12 A polar solvent aids in solvating the alkali metal naphtholate, thereby creating a solvent-separated ion-pair.It acts in a similar way as a crown ether: increasing the alkali cation and oxygen intranuclear distance and creating a homogeneous solution. The yields of 2-H-1-NA in polar aprotic solvents were greater than the crown ether yields when nitrobenzene, 1,4-dioxane, ethylene carbonate, or DMSO were added.For all of the solvents, except 1,4-dioxane and DMSO, the reaction time was shortened to 3 h. The greatest yield (66%) after purification was with DMSO; however, DMF, which is also a very polar solvent, unexpectedly gave much lower yields. The reason for this dichotomy is as yet unknown. The yields were probably lower with crown ethers because a crown ether can only react once to bind the cation; however, a polar solvent can make many solvent-separated ion-pairs through the course of the reaction.In conclusion, the reaction of alkali metal naphtholates with CO2 has been clarified through the use of crown ethers and polar solvents in benzene. The yields seem to vary with the solvating strength of the crown ether or polar solvent. The crown ether aids in the dissolution of the naphtholate salt to make a homogeneous solution similar in principle to polar solutions that solvate the cation-anion pair increasing their intramolecular distances.The anionic charge is then more pronounced on the oxygen and naphthalene ring, easing the electrophilic attack of CO2, as supported by MNDO and H�uckel calculations. Further experimentation and calculations are being performed to elucidate the mechanistic details. Experimental General Procedure for the Preparation of 2-H-1-NA.·A cylindrical Pyrex reactor was fitted with a Teflon stopper with two holes, *To receive any correspondence.†This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1997, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Table 1 Effects of crown ethers on the carboxylation of alkali metal 2-naphtholates (0.01 mol) in benzene (15 ml)a Crown ethers Alkali Time Yield of (0.001 mol) metal salt (t/h) 2-H-1-NA (%) None Dibenzo-18-crown-6 Benzo-15-crown-5 15-Crown-5 18-Crown-6 potassium potassium sodium potassium sodium potassium sodium 6666656 0.5 27.5 21.0 14.6 43.7 43.8 29.8 aReaction temperature, 60 °C; atmospheric pressure of CO2.Table 2 Effects of additive polar aprotic solvents on the carboxylation of potassium 2-naphtholate (0.01 mol) in benzene (15 ml)a Additives (0.001 mol) Time (t/h) Yield of 2-H-1-NA (%) None DMSO DMF Ethylene carbonate 1,2-Dimethoxyethane 1,4-Dioxane Nitrobenzene 6633363 0.5 66.0 39.4 45.3 26.7 58.5 50.5 aReaction temperature, 60 °C; atmospheric pressure of CO2.J.CHEM. RESEARCH (S), 1997 375 one for a thermometer and the other one for a gas inlet tube. A gas burette was attached to the reaction apparatus to monitor the carbon dioxide uptake. A crown ether such as 18-crown-6 (0.001 mol) was used as received or a polar solvent such as DMSO (0.001 mol) was placed in the reaction apparatus with dry benzene (15 ml) and stirred. Dry potassium 2-naphtholate (0.01 mol), made from 2-naphthol and KOH, was then added to the flask and put under vacuum.Successful incorporation of K+ into the crown ether was indicated by an immediate formation of a bright lavender solution. The reaction vessel was heated to 60 °C, then the inner atmosphere was substituted with carbon dioxide (1 atm). The reaction was stopped when the CO2 was no longer being absorbed. The solution was evaporated to dryness under reduced pressure and the product was dissolved in water and made neutral to litmus to precipitate 2-naphthol, which was filtered off at 20 °C.The filtrates were acidified with H2SO4 to Congo Red at 55 °C and the precipitated 2-H-1-NA was filtered off at 18 °C, washed and centrifuged. The product was dried at 45 °C for 2 days. The products were identified by HPLC and mass spectrometry. Received, 19th May 1997; Accepted, 1st July 1997 Paper E/7/03432F References 1 C. T. Pedersen and H. K. Frensdorff, Angew. Chem., Int. Ed. Engl., 1972, 11, 16. 2 J. M. Lehn, Acc. Chem. Res., 1978, 11, 49. 3 D. J. Cram and J. M. Cram, Acc. Chem. Res., 1978, 11, 8. 4 J. M. Lehn, Science, 1985, 227, 849. 5 R. M. Izatt, J. S. Brawshaw, S. A. Neilson, J. D. Lamb, J. J. Christensen and D. Sen, Chem. Rev., 1985, 85, 271. 6 F. Seidel, L. Wolf and H. Krause, J. Prakt. Chem., 1955, 91, 53. 7 W. H. Meek and C. H. Fuchsman, J. Chem. Eng. Data, 1969, 14, 388. 8 T. Yamaguchi, N. Nagaoka and K. Takahashi, J. Chem. Soc. Jpn., 1989, 7, 1164. 9 K. Takahashi and T. Yamaguchi, Jpn. Kokai Tokkyo Koho JP, 01,316,343, 1989. 10 L. M. Thomassen, T. Ellingsen and J. Ugelstad, Acta. Chem. Scand., 1971, 254, 3024. 11 C. J. Pedersen, J. Am. Chem. Soc., 1967, 89, 7017. 12 K. Takahashi and T. Yamaguchi, Jpn. Kokai Tokkyo Koho JP, 02,235,844, 199

ISSN:0308-2342    

DOI:10.1039/a703432f

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

• • • • H H H H H H H H 1 • • • • Me Me Me Me Me Me Me Me 2 376 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 376–377† Configurations of Cyclododeca-1,2,4,5,7,8,10,11-octaene and Its Octamethyl Derivative† Issa Yavari,*a Davood Nori-Shargh,b Robabeh Baharfara, Rahim Hekmat-Shoara and Hassan Norouzi-Arasib aDepartment of Chemistry, University of Tarbiat Modarres, P.O. Box 14155-4838, Tehran, Iran bDepartment of Chemistry, Islamic Azad University, Arak, Iran MNDO, AM1 and PM3 semi-empirical SCF MO calculations are used to calculate the structure optimization and configurational properties of cyclododeca-1,2,4,5,7,8,10,11-octaene (1) and its octamethyl derivative (2); the combination of four allenic units of the same chirality yields an enantiomeric pair of D4 symmetry, which is the most stable configuration of 1 and 2.Cyclododeca-1,2,4,5,7,8,10,11-octaene (1), with four allenic chromophores, could experience eight-electron cyclic interactions of both the in-plane and out-of-plane p bonds of the four allenic moieties.1–3 This ‘expanded cyclooctatetraene’ is expected to manifest special configurational properties.Conceptually, 1 may be regarded to be constructed by inserting a carbon atom in the carbon–carbon double bonds of cycloocta-1,3,5,7-tetraene. This structural feature suggests that combination of four units of the same chirality yields an enantiomeric pair (RRRR and SSSS) of D4 symmetry, while combination of three units of the same chirality and a unit of opposite chirality produces an enantiomeric pair (RRRR or SSSR) of C2 symmetry (see Scheme 1).Combination of two pairs of units of opposite chirality yields two meso compounds RRSS and RSRS of C2h and D2d symmetries, respectively. Intrigued by the fascinating molecular structure of the cyclic tetra-allene 1, we carried out semi-empirical SCF MO calculations4,5 on eight possible configurations of 1 and 2. Although 1 and 2 are presently unknown, their configurations are of interest.Calculations Initial estimates of the geometry of structures 1 and 2 were obtained by a molecular-mechanics program PCMODEL (88.0)6 followed by full minimization using semiempirical MNDO,7 AM18 and PM39 methods in the MOPAC 6.0 computer program,5,10 implemented on a VAX 4000-300 computer. Optimal geometries were located by minimizing energy, with respect to all geometrical coordinates, and without imposing any symmetry constraints. All geometries were characterized as stationary points, and true local energy minima on the potential energy surface were found using Keyword FORCE.All geometries obtained in this work are calculated to have 3Nµ6 real vibrational frequencies.11 Results and Discussion Heats of formation (DH°f ) for the eight configurational diastereoisomers of cyclododeca-1,2,4,5,7,8,10,11-octaene (1) and its octamethyl derivative (2), as calculated by MNDO, AM1 and PM3 methods, are shown in Table 1.The highly symmetrical crown configuration, with D4 point group, is calculated by all three methods to be the most stable geometry of 1 and 2. This configuration is constructed by a combination of four allenic moieties of the same chirality. While the axial symmetrical twist configuration of 1 is calculated by MNDO and PM3 methods to be the next most stable geometry, the best (RSRS, D2d) configuration of 1 is predicted by the AM1 method as the second most stable diastereoisomer.All three methods predict the twist (C2) configuration to be the second most stable geometry of the octamethyl derivative 2. *To receive any correspondence. †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1997, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Scheme 1 Table 1 Calculated energies (kJ molµ1) in various configurations of cyclododeca-1,2,4,5,7,8,10,11-octaene (1) and its octamethyl derivative (2) 1 2 MNDO AM1 PM3 MNDO AM1 PM3 Geometry DH°f DDH°f a DH°f DDH°f a DH°f DDH°f a DH°f DDH°f a DH°f DDH°f a DH°f DDH°f a RRRR, D4 731.6 00.0 801.0 00.0 819.4 00.0 475.5 00.0 581.2 00.0 537.8 00.0 RRRS, C2 748.7 17.1 809.4 8.4 829.2 9.8 511.8 36.3 596.3 15.1 558.6 20.8 RSRS, D2d 750.0 18.4 804.5 3.5 829.3 9.9 545.3 69.8 547.6 16.4 566.8 29.0 RRSS, C2h 752.6 21.0 809.7 8.7 829.3 9.9 522.2 46.7 598.4 17.2 560.7 22.9 aRelative to the best configuration of the same compound.(–78)–76 (86)84 (–71)–72 77(83) –15 –75 87 (–18) (89) (–78) 119 174 124 126 (178)180 (123) (122) (174) (118) 172(171) 120 • • • • • • • • • • • • • • • • (118) 122(121) 177(178) Crown ( RRRR, D4) Twist ( RRRS, C2) (118)116 (–73)–72 (0)0 (72)69 (0)0 123(121) 174(175) Boat ( RSRS, D2d) Chair ( RRSS, C2h) 120(119) 174(175) 123(121) J.CHEM. RESEARCH (S), 1997 377 The relevant structural parameters for various con- figurational diastereoisomers of 1 and 2, as calculated by the AM1 method, are given in Fig. 1. The C�C�C moieties are bent in various configurations of 1 and 2 and they are 1–9° compressed from the normal value of 180°. In general, the internal angle deformations increase from chiral geometries, such as crown and twist, to meso configurations. The C�C·C bond angles in all geometries of the octamethyl derivative 2 are 1–2° more compressed in comparison to those in 1, as a result of the methyl substituents.The C(sp2)·C(sp2)·C(sp2)·C(sp2) arrangements in the allenic moieties of the twist and meso configurations (boat and chair) of 1 and 2 are fairly twisted (7–21°) from their energy minimum at 90°, as a result of ring strain. However, the extent of this torsional deformation in the crown geometry is much smaller. The boat configurations of 1 and 2 have favoured torsional angles of single bonds flanked by two double bonds. The stabilization (negative strain energy) resulting from the conjugative effects of double bonds in the twist and meso geometries are more than offset by the unfavourable torsions and bond angles around the allenic moieties in these configurations.In conclusion, semi-empirical calculations provide a picture of the configurations of cyclododecaoctaene 1 and its octamethyl derivative (2) from both structural and energetic points of view. All three methods employed in this work predict that combination of four allenic chromophores of the same chirality yields an enantiomeric pair of crown (D4) configuration, which is the most stable diastereoisomer of 1 and 2.It would be valuable, of course, to have direct structural data on 1 and 2 for comparison with the results of the semi-empirical SCF MO calculations. We gratefully acknowledge financial support from the Research Council of the Islamic Azad University, Arak. Received, 2nd May 1997; Accepted, 1st July 1997 Paper E/7/03617E References 1 A. Greenberg and J. F. Liebman, Strained Organic Molecules, Academic Press, New York, 1978. 2 R P. Johnson, Chem. Rev., 1989, 89, 1111. 3 P. G. Garrat, K. C. Nicolaou and F. Sondheimer, J. Am. Chem. Soc., 19734, 95, 4582. 4 D. M. Hirst, A Computational Approach to Chemistry, Blackwell Scientific Publications, Oxford, 1990. 5 J. J. P. Stewart, J. Comput.-Aided Mol. Des., 1990, 4, 1. 6 Serena Software, Box 3076, Bloomington, IN, USA. 7 M. J. S. Dewar and W. Thiel, J. Am. Chem. Soc., 1977, 99, 4899, 4907. 8 M. J. S. Dewar, E. G. Zeobish, E. F. Healy and J. J. P. Stewart, J. Am. Chem. Soc., 1985, 107, 3907. 9 J. J. P. Stewart, J. Comput. Chem., 1989, 10, 221. 10 J. J. P. Stewart, QCPE 581, Department of Chemistry, Indiana University, Bloomington, IN, USA. 11 J. W. McIver, Jr., Acc. Chem. Res., 1974, 7, 72. Fig. 1 Calculated AM1 structural parameters (bond angles and dihedral angles in degrees) in various configurations of 1: the parameters shown in parentheses belong to the octamethyl derivati

ISSN:0308-2342    

DOI:10.1039/a703617e

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

R1 O R2 R1 N3 OH R2 SnCl2•2H2O/Mg/THF NaN3 + H2O O O O CH CH2 O Ph CH CH O Ph Ph CH CH2 O CH2 O Ph OH N3 N3 OH OH N3 N3 OH Ph CH N3 CH2 OH Ph CH OH CH Ph N3 CH2 CH OH CH2 O Ph N3 O 378 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 378–379† An Efficient Nucleophilic Cleavage of Oxiranes to 1,2-Azido Alcohols† Chintamani Sarangi,a Nalin B. Das,*a Bhagabat Nanda,a Amalendu Nayaka and Ram P. Sharmab aRegional Research Laboratory, Bhubaneswar-751013, India bCentral Institute of Medicinal and Aromatic Plants, Lucknow-226015, India Regioselective ring opening of oxiranes has been induced by the SnCl2 .2H2O–Mg–THF/NaN3–H2O system to give the corresponding 1,2-azido alcohols in good yields. Epoxides are valuable intermediates in organic synthesis because their nucleophilic cleavage leads to 1,2-difunctionalized systems.1 Preparations of 1,2-azidoalcohols have been reported2–8 regioselectively through nucleophilic cleavage of oxirane rings.The present work has been undertaken in order to determine the general applicability of the reaction with epoxides, as well as to determine the direction of ring opening for a number of representative symmetrical and unsymmetrical epoxides.In continuation of our earlier studies on applications of metal reagents,9,10 we have found that SnCl2 .2H2O–Mg/NaN3–H2O/THF is a promising system for regioselective ring opening of oxiranes to the corresponding 1,2-azido alcohols. In the system SnCl2·2H2O–Mg/NaN3–H2O with cyclohexene oxide, azide ion readily attacks the epoxide ring carbon through a bimolecular nucleophilic displacement reaction which proceeds with inversion, to give the azido alcohol.In unsymmetrical epoxides (entries 2, 3, 4 and 7), the ring opening appears preferably at the less substituted carbon, leading to nucleophilic attack occurring predominantly at the sterically less hindered site. In the case of styrene oxide, azide ion attacks exclusively at the secondary carbon atom of the epoxide ring.This interesting observation proves the structure of the corresponding azido alcohol (Table 1, entry 5) from its known reduction product, 2-amino-2-phenylethanol, with the reducing agent LiAlH4. This has been further attributed to the fact that an unsaturated group, viz. phenyl, helps to promote the positively charged secondary carbon atom of the epoxide ring, in the presence of a nucleophilic reagent, owing to its high degree of resonance stabilization.The increase in electrophilicity of the oxirane carbon with this system promotes the participation of the azide anion with trans stereoselectivity, which is probably due to steric and electronic effects. The cleavage of oxirane rings has also been tried using SnCl2 .2H2O–NaN3–THF alone but the reaction did not occur. However, the use of a stoichiometric amount of magnesium facilitated the reaction. In addition, the possibility exists of active zero-valent tin generated in principle by the reduction of SnII to Sn0 in the presence of magnesium effectively inducing nucleophilic attack.The reaction has also been tried with MgCl2 instead of SnCl2 for a longer period but no trace of the required reaction product was obtained. Owing to the general interest in the smooth and selective cleavage of these compounds, the mild reaction conditions, good yields and some possible synthetic generalization, the SnCl2 .2H2O–Mg–THF/NaN3–H2O system will be a useful addition to existing methods.Experimental 1H NMR spectra were recorded in deuteriochloroform on a JEOL FX-90 instrument. IR spectra were recorded on a JASCO FT/IR-5300 instrument in chloroform. Mass spectra were recorded *To receive any correspondence. †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1997, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Table 1 Oxirane ring opening with SnCl2·2H2O/Mg/THF/NaN3–H2O Entry Oxirane Time (t/h) Producta Yield (%)b Lit.ref. 1 0.5 85 6, 7, 8 2 0.75 83 11 3 0.5 88 6, 7 4 0.75 70 3 5 0.5 95 6, 7 6 1.5 82 8 7 2 92 6, 7 aAll the products were confirmed by spectral data. bTotal yield of the regioisomers.J. CHEM. RESEARCH (S), 1997 379 on an MS-30 instrument. TLC and preparative TLC were performed on silica gel (E. Merck). General Procedure.·To a stirred suspension of SnCl2.2H2O (442 mg, 2 mmol), Mg powder (36.5 mg, 1.5 mmol) and oxirane (1 mmol) in tetrahydrofuran (5 ml) was added sodium azide (97.5 mg, 1.5 mmol) in H2O (5 ml) slowly at room temperature.The reaction mixture was stirred for 0.5–2 h. After completion of the reaction (TLC), the resulting mixture was filtered and usual workup was carried out with dichloromethane. Removal of the organic solvent under reduced pressure followed by purification through preparative chromatography afforded the corresponding 1,2-azido alcohols. Selected spectral data.Entry 1: dH (CDCl3) 1.15–2.20 (8 H, m), 2.95 (1 H, br s), 3.25–3.7 (2 H, m); vmax/cmµ1 (neat) 3400 (OH), 2100 (N3). Entry 3: dH (CDCl3) 1.25–1.85 (10 H, m), 2.20 (1 H, br s), 3.30 (2 H, s); vmax/cmµ1 (heat) 3400 (OH), 2100 (N3). Entry 5: dH (CDCl3) 2.33 (1 H, s), 3.95 (2 H, d), 5.00 (1 H, t), 7.45 (5 H, m); vmax/cmµ1 (neat) 3400 (OH), 2102 (N3). We thank Professor H. S. Ray, Director, and Dr Y. R. Rao, Head F&M Division, Regional Research Laboratory, for their valuable suggestions.C. S. acknowledges the pool scheme of the Government of India. Received, 26th February 1997; Accepted, 3rd July 1997 Paper E/7/01358B References 1 J. G. Smith, Synthesis, 1984, 629. 2 M. Caron and K. B. Sharpless, J. Org. Chem., 1985, 50, 1560. 3 D. Sinou and M. Emziane, Tetrahedron Lett., 1986, 27, 4423. 4 C. Blandy, R. Choukroun and D. Gervais, Tetrahedron Lett., 1983, 24, 4189. 5 M. Caron, P. R. Carlier and K. B. Sharpless, J. Org. Chem., 1988, 53, 5187. 6 S. Saito, S. Yamashita, T. Nishikawa, Y. Yokoyama, M. Inaba and T. Moriwake, Tetrahedron Lett., 1989, 30, 4153. 7 S. Saito, T. Nishikawa, Y. Yokoyama and T. Moriwake, Tetrahedron Lett., 1990, 31, 221 and references cited therein. 8 G. K. Biswas, A. K. Maiti and P. Bhattacharyya, J. Chem. Res. (S), 1994, 380 and references cited therein. 9 C. Sarangi, A. Nayak, B. Nanda, N. B. Das and R. P. Sharma, Tetrahedron Lett., 1995, 36, 7119. 10 C. Sarangi, A. Nayak, B. Nanda, N. B. Das and R. P. Sharma, J. Chem. Res. (S), 1996, 28 and references cited therein. 11 M. Chini, P. Crotti and F. Macchau, Tetrahedron Lett., 1990, 31, 5641.

ISSN:0308-2342    

DOI:10.1039/a701358b

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

X NO2 NH Z X NO2 N Z R Br R ( a) ( b) ( a) Z = Ph: NaOH–K2CO3–BTAC–benzene, heat ( b) Z = 4-Me-C6H4SO2, COMe: K2CO3–BTAC–acetone Z = Ph, 4-Me-C6H4SO2: SnCl2–Zn–HCl–AcOH 1 Z = COMe: Fe–EtOH–AcOH X NH2 N Z R 2 X N N Me R 4 X N2 + N Z R i, NaNO2–HCl ii, NaN3 h-j X N3 N Z R X N N N N R Z benzene heat H Ph H H Ph Me H Ph Ph Cl Ph H Cl Ph Me Cl Ph Ph Cl Ph 4-Me-C6H4SO2 H COMe H H COMe Me H COMe Ph a b c d e f g h i j XZ R 3 5 380 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 380 J.Chem. Research (M), 1997, 2215–2226 Intramolecular Azide Cycloadditions leading to [1,2,3]Triazolo[1,5-a]quinoxalines Gianluigi Broggini, Luisa Garanti, Giorgio Molteni* and Gaetano Zecchi Dipartimento di Chimica Organica e Industriale dell’Universit`a and Centro CNR, Via Golgi 19, 20133, Milano, Italy A general synthetic route to the title heterocyclic compounds has been developed based on the title reaction. We report here the synthesis of a variety of [1,2,3]triazolo[ 1,5-a]quinoxalines6,7 based upon the intramolecular cycloaddition of suitably functionalised aryl azides.As illustrated in the Scheme, our synthetic sequence involves the following steps: (i) preparation of N-substituted N-(2-alkynyl)-o-nitroanilines 1; (ii) reduction of their nitro group to a primary amino group; (iii) diazotisation of the so-formed anilines 2 and subsequent reaction with sodium azide to form the desired azidoderivatives 3; (iv) heat treatment of 3 in order to promote the intramolecular cycloaddition onto the acetylenic bond (see Table 1).Techniques used: IR, 1H NMR, mass spectrometry References: 11 Tables 2–5: Physical and spectral data for compounds 1b–j, 2b–j, 3, 4h, j and 5 Table 6: Elemental analyses of new compounds Received, 30th January 1997; Accepted, 23rd June 1997 Paper E/7/00705A References cited in this synopsis 6 J. C. Kauer and R. A. Carboni, J. Am. Chem. Soc., 1967, 89, 2633. 7 E. Lippmann and M. Vogel, Stud. Org. Chem. (Amsterdam), 1988, 35, 394. *To receive any correspondence (e-mail: garanti@icil64.cilea.it). Table 1 Reaction of azides 3a Reaction time Products and yields (%) Substrate (t/h) 5 Eluent 3a 3b 3c 3d 3e 3f 3g 3h 3i 3j 4 12 54441.5 1.5 21 4 80 63 76 60 60 67 78 91 80 96 — Et2O–CH2Cl2 (1:5) ———— AcOEt–Light petroleumb (1:1) Et2O–CH2Cl2 (1:5) CH2Cl2–Light petroleumb (5:1) aRefluxing in benzene solution (0.05 M). bBp 40–60 °C. Scheme

ISSN:0308-2342    

DOI:10.1039/a700705a

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

Synthesis and First Separation of Chiral TrimetalCarbonyl Clusters containing an RuCoMo(m3-S) CoreEr-Run Ding,a Qing-Shan Li,a Yuan-Qi Yin*a and Jie SunbaState Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute ofChemical Physics, Chinese Academy of Science, Lanzhou 730000, ChinabShanghai Institute of Organic Chemistry, Chinese Academy of Science, Shanghai 200032, ChinaClusters RuCoMo(3-S)(CO)8C5H4R [R HC(O) 2, MeC(O) 3, PhC(O) 4, MeOC(O)C6H4C(O) 5] were obtained bythe reaction of (3-S)RuCo2(CO)9 1 and [M(CO)3RC(O)Cp]£¾, clusters 3 and 5 have been solved by single crystalX-ray diffraction and cluster 3 was resolved on amylopection tris(phenylcarbamate) (ATP) chiral stationary phases(CSPs).Transition-metal cluster compounds are currently underintensive scrutiny because of their potential catalytic appli-cations, both as models for understanding catalytic metalsurfaces1 and as catalysts in their own right.3 Our interest inthe reactivity of chiral clusters prompted us to prepare tetra-hedral skeleton complexes containing RuCoMoS cores andto nd a good method of resolution of enantiomers byliquid chromatography on CSPs.Reuxing a solution of NaMo(CO)3(C5H4)R [R HC(O),MeC(O), PhC(O), MeOC(O)C6H4C(O)] with cluster 1 inTHF gave clusters 2¡Ó5 in moderate yield (Scheme 1).Reduction of cluster 3 by NaBH4 in methanol at roomtemperature gave cluster 6.The IR spectra of all clustersexhibited a large number of absorption bands between 1856and 2087 cm£¾1, which were assigned to terminal carbonylvibrations.The spectra of the cluster 6 revealed OH absorp-tion peaks at 3383 cm£¾1. These results are consistent withthe reduction of the C.O groups (1686 cm£¾1) in cluster 3 bythe action of NaBH4.The structures of clusters 3 and 5 were determined byX-ray structure analysis and crystal data are collected inTable 1. The structure of cluster 3 unexpectedly revealsthe presence of two isomeric molecules A and B in the unitcell (Fig. 1). Each unit displays a RuCoMoS tetrahedralgeometry. The acute angles in the tetrahedral core of cluster3 about the basal atoms range from 50.12 to 64.098, andthose about the sulfur atom average 73.468, which deviateconsiderably from perfect tetrahedral geometry. This resultsbecause the metal¡Ómetal bonded RuCoMo triangle restrictsthe angles around the sulfur atom. The distances from thesulfur atom to the metal are not equal [Ru¡ÓS 2.330(3) A ,Mo¡ÓS 2.37692) A , Co¡ÓS 2.205(3) A ].The Ru¡ÓS bondlength is roughly equal to that in a known complexHRu3(CO)9[(m2-S)Mo(CO)3(NCMe)2] (Ru¡ÓS 2.334 A ) butis shorter than that found typically.11 Cluster 5 contains atetrahedral skeleton formed by Ru, Co, Mo and S, theslightly distanced triangular Ru¡ÓCo¡ÓMo moiety beingcapped by a sulde ligand as in cluster 3 (Fig. 2. The dis-tance of the Mo atom to the Cp ring center is 1.992 A .Treating m3-S as a four-electron donor and the cyclopenta-dienyl group as a ve-electron donor, cluster 5 contains atotal of 48 valence electrons and is electronically saturated.J.Chem. Research (S),1998, 624¡Ó625J. Chem. Research (M),1998, 2601¡Ó2657Table 1 Summary of crystal and intensity data for complexes 3 and 5Complex 3 5Formula C15H7O9SRuCoMo C22H11O11SCoRuMoMw 619.22 739.11Crystal system Orthorhombic TriclinicSpace group Pbca P1a/A 26.229(7) 8.174(3)b/A 18.200(6) 19.454(4)c/A 15.929(4) 8.042(3)a/8 92.78(2)b/8 108.74(3)g/8 88.73(1)Z 8 2V/A 3 7604(6) 1209.5(7)Dc/g cm£¾3 2.163 2.030l/A 0.71069 0.71069T/8C 20 20m(moKa) cm£¾1 24.51 19.51F(000) 4768.00 720.00No observations [I > 3.00s(I)] 3343 2674Total no.reflections 4883 3861Residuals: R, Rw 0.033, 0.045 0.056, 0.074Scheme 1*To receive any correspondence (e-mail: hcom@ns.lzb.ac.cn).624 J. CHEM. RESEARCH (S), 1998In our attempts to separate the enantiomers of 3 we found that a general separation procedure did not apply. However, an enantiomer separation via chromatography over an optically active adsorbent was successful.The chiral ability of the CSP depends on the thickness of the coating. Usually, the greater the amount of chiral agent, the better the chiral discrimination. For coated cellulose CSP, Okamoto et al.12 chose a coating of ca. 20¡¾25 mass%. However, we found that this level resulted in low optical resolution on the 25 mass % ATP-coated phase; a coating of 15 mass % appeared to be optimal. This indicates that it is important to reduce non-chiral interactions with Si¡¾OH or ¡¾NH2 groups by a well distributed and ordered coating and overloading may destroy this characteristic. Fig. 3 shows the chromatogram of 3 on a 15 mass % coated phase. We are grateful to the Laboratory of Organometallic Chemistry at Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences for the ¢çnancial support of our work. Techniques used: 1R, 1H NMR, MS, HPLC Table 2: Atomic coordinates and Biso/Beq for cluster 3 Table 3: Atomic coordinates and Biso/Beq for cluster 5 Table 4: Selected intramolecular distances (AE ) and bond angles (8) for cluster 3 Table 5: Selected intramolecular distances (AE ) and bond angles (8) for cluster 5 Table 6: The e€ects of propan-2-ol concentration on the resolution References: 18 Appendix: Crystallographic data for cluster 3 and 5 Received, 19th February 1998; Accepted, 15th June 1998 Paper E/8/01418C References cited in this synopsis 1 G.Su E ss-Fink, Angew. Chem., 1994, 104, 71. 3 J. R. Shapley, Strem Chem., 1978, 6, 3. 11 L. A. Hoferkamp, G. Rhenwald, H. Stoeckli-Evans and G. Suss- Fink, Organometallics, 1996, 15, 704. 12 Y. Okamoto, K. Hatada, T. Shibata, I. Okamato, H. Namikoshi and Y. Yuki, Eur. Pat. Appl., 1984, EP 147804. Fig. 1 Crystal structure of cluster 3 Fig. 2 Crystal structure of cluster 5 Fig. 3 The chromatograms of resolution of the cluster 3 on a 15% ATP-coated column Mobile phase: hexane¡¾propan-2- ol a 95:5 (v/v); Flow rate: 0.5 ml min¢§1; 0.02 AUF J. CHEM. RESEARCH (S), 1998 625

ISSN:0308-2342    

DOI:10.1039/a801418c

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

Oxidation of 3-Aryl-4-(1-hydroxyethyl)sydnones using DMSO-Ac2O as Oxidant Shaw-Tao Lin,*a Hsien-Ju Tienb and Jinn-Tsair Chenb aDepartment of Applied Chemistry, Providence University, Sha-Lu, Taichung Hsien, 433, Taiwan, ROC bDepartment of Chemistry, National Cheng Kung University, Tainan, 701, Taiwan, ROC Treatment of 3-aryl-4-(1-hydroxyethyl)sydnones with DMSO-Ac2O yielded esters and ketones, depending on the amount of Ac2O used; application of a limited amount of Ac2O with DMSO as an oxidant has been found to be the only method to convert the title compounds to the ketones.Transformation of functional groups is a very important topic in organic chemistry.1 The reactivity of any speci®c functional group is strongly dependent on the nature of its environment, i.e., electron density, steric factors etc. The sydnone ring is a non-benzenoid heterocyclic aromatic ®ve- membered ring and possesses some unusual characteristics. It can be regarded as a mesoionic system with positive and negative charges distributed around the ring depending on their resonance forms.2 In general it is believed that C(4) possesses negative character and N(2) is positive, based on their orientation and calculations.Reduction and oxidation (redox) reactions involve electron transfer from one reactant to another. The feasibility of a redox process therefore strongly depends on the electron density of a functional group. Although, reduction of the carbonyl group of ketones or aldehydes by using sodium tetrahydroborate is a very feasible process,3 only the carbonyl group at the C(4) position in the sydnone ring can be reduced by NaBH4 in methanol media, because of the electron-donating char- acter of the C(4) position.4 On the other hand, a number of attempts to oxidize C(4) of 1-hydroxyethylsydnone to form an acetyl group have consistently failed.These attempts mainly involved use of dichromate±sulfuric acid in acetone or manganese dioxide in acetic acid with ultrasonic agitation4 as the oxidation conditions.Strong oxidants (former) are hence likely to decompose the sydnone ring, while weaker oxidant (latter) does not cause any reaction. In the present work, a combination of dimethyl sulfoxide (DMSO) and acetic anhydride (Ac2O) is used as an oxidant to convert the hydroxyl group to a carbonyl group. Esteri®cation can be achieved along with this reaction in the presence of an excess of anhydride.Results and Discussion DMSO is known as a mild oxidant and is able to convert primary or secondary alcohols to the corresponding aldehydes or ketones without formation of acid or other oxidation products.6 The oxidation is often activated by the presence of electrophilic reagents, such as thionyl chloride, oxalyl chloride, halogens, sulfuric trioxide/pyridine or acetic anhydride. Among these electrophilic agents, acetic anhydride is the most convenient. In this study, a solution of 4-(1-hydroxyethyl)sydnone, DMSO and acetic anhydride was heated at 100 8C for 10 min to achieve oxidation.After the work-up process, ketones and/or esters were obtained from 3-aryl-4-(1- hydroxyethyl)sydnones, which contained various sub- stituents on the phenyl ring. The relative fractions of ester and ketone thus produced have been found to depend on the amount of acetic anhydride used (Table 1). When a limiting amount of acetic anhydride was used as a catalyst, the reaction led to formation of ketones as the only product (condition A) while large amounts of acetic anhydride in the mixture yielded more ester products (conditions B and C).The esteri®cation can be directed between the alcohol and acetic anhydride or acetyl group. This process is enhanced by the addition of acetate ions from either sodium acetate or triethylamine in the mixture of DMSO and acetic anhydride (entries 6, 7). To bring about oxidation of the hydroxy group, DMSO ®rst reacts with an electrophilic reagent (i.e., acetic anhydride) to form an intermediate a with a positive charge on the sulfur atom (Scheme 1).Thus sulfur facilitates a nucleophilic attack by the oxygen atom of the hydroxy group that separates from the acetic acid to J. Chem. Research (S), 1998, 626±627 J. Chem. Research (M), 1998, 2783±2791 Table 1 Product distributions from the reaction of 4-(2-hydroxyethyl)sydnones by using DMSO±Ac2O oxidant Yield (%) Entry Reactant Conditiona Ketone (K) Ester (E) 1 1 A 84 – 2 1 B 46 38 3 1 C 31 53 4 1 D – – 5 1 E – 40 6 1 F – 75 7 1 G – 63 8 2 A 70 – 9 2 C 35 40 10 3 A 83 – 11 3 C 15 70 12 4 A 76 – 13 4 C – 70 14 5 A 65 – 15 5 C 20 40 16 6 A 80 – 17 6 C 8 80 18 7b A 63 – 19 7b C 20 47 20 8 A 50 – 21 8 C 15 42 22 9 A 54 – 23 9 C 16 46 aIsolated yields.The mixtures containing sydnone (2.4 mmol) were heated at 100 8C for 10 min. A, DMSO±Ac2O [10.0 ml: 0.5 ml (2.0 equiv)]; B, DMSO±Ac2O (5.0 ml: 5.0 ml); C, DMSO±Ac2O [0.2 ml (1.0 equiv.)/10.0 ml]; D, AcOH (10.0 ml) used only; E, Ac2O (10.0 ml) used only; F, NaOAc (1.0 g, 12.2 mmol) was added to solution B; G, Et3N (1.0 ml, 7.2 mmol) was added to solution B.bReaction time was 20 min instead of 10 min. *To receive any correspondence. 626 J. CHEM. RESEARCH (S), 1998form intermediate b. This pathway involves abstraction of hydrogen from a methyl group next to the sulfur atom in intermediate b to form c. Notably, the acidity of the hydrogens of the methyl group is enhanced by the positive charge on the sulfur atom. The methylene anion in c sub- sequently abstracts a hydrogen from the carbon attached at C(4) of the sydnone ring, followed by loss of dimethyl sul¢çde to form the ketone as the ¢çnal product.Abstraction of a hydrogen from the carbon attached at C(4) of the sydnone ring followed by loss of a DMSO molecule might be an alternative pathway for the formation of ketones. In general, the presence of a nitro group lowered the yield of both ketones and esters.At least 20 min reaction time is required to yield comparable results for 4-(1-hydroxyethyl)- 3-(4-nitrophenyl)sydnone (7, entries 18¡¾23). The electron- withdrawing group on the phenyl ring decreases the electron density at the C(4) position on the sydnone ring which further destabilizes intermediate b, and consequently a€ords a lower yield. This mechanism shows the presence of a positive charge on intermediates b.Experimental 3-Substituted 4-(1-hydroxyethyl)sydnones were prepared by the reactions of the corresponding 4-lithiosydnones with acetaldehyde according to the literature.7 Typical Oxidation of 3-Aryl-4-(1-hydroxyethyl )sydnone using DMSO¡¾Ac2O.�¢After the mixture of DMSO¡¾Ac2O (10 ml, with ratios as given in Table 1), containing 3-aryl-4-(1-hydroxyethyl)- sydnone, was heated at 100 8C for 10 min, the solution was cooled and chloroform (30 ml) added. This mixture was then washed with water (50 ml5) to remove DMSO and acetic acid.The organic layer was dried (MgSO4), evaporated, and then absorbed by silica gel for chromatographic separation by using ethyl acetate¡¾n-hexane (1:2, v/v) as eluent. The product ester was washed out before the product ketone. Melting points of the known 4-acetyl derivatives were compared with those of the authentic compounds. All of the 4-(1-ethoxycarbonyl)sydnones are new compounds synthesized in this study and their properties are reported in Table 2 (CHN elemental analyses within20.05%).Financial support for this work by the National Science Council of the Republic of China is gratefully acknowl- edged. Techniques used: 1H NMR, MS, IR, elemental analysis References: 7 Received, 4th March 1998; Accepted, 6th May 1998 Paper E/8/01789A References 1 R. C. Larock, in Comprehensive Organic Transformations: A Guide to Functional Group Preparation, VCH Publishers, Inc., New York, NY, 1989. 2 C. G. Newton and C. A. Ramsden, Tetrahedron, 1982, 38, 2965. 3 Reductions in Organic Synthesis: Recent Advances and Practical Applications, ed. A. F. Abdel-Magid, ACS Symp. Ser. 641, 1996. 4 H. J. Tien, J. Y. Cherng and S. T. Lin, J. Chin. Chem. Soc., 1995, 42, 987. 5. Tsuboi, N. Ishii, T. Sakai, I. Tari and M. Utaka, Bull. Chem. Soc. Jpn., 1990, 63, 1888. 6 W. W. Epstein and F. W. Sweat, Chem. Rev., 1967, 67, 247; R. F. Butterworth and S. Hanessian, Synthesis, 1971, 10; M. Hondo, T. Katsuki and H.Yamaguchi, Tetrahedron Lett.. 1984, 25, 3857. 7 H. J. Tien, G. M. Fang, S. T. Lin and L. L. Tien, J. Chin. Chem. Soc., 1992, 39, 107. Scheme 1 Table 2 Physical properties and spectral data of new 4-acetyl- (A) and 4-acetoxy- (B) sydnones Product Mp/8C (colour) IR ( /cm¢§1)a dH (CDCl3) (J/Hz) m/zb 2 102¡¾104 red flakes 1713 1.38 (t, 3 H, J 7.2), 1.57 (d, 3 H, J 7.5), 4.38 (q, 1 H, J 7.2), 4.63 (q, 1 H, J 7.5), 7.81 (d, 2 H, J 8.5), 8.25 (d, 2 H, J 8.5) 278, 176 7 112¡¾114 yellow powder 1731 1.59 (d, 3 H, J 7.2), 4.65 (q, 1 H, J 7.2), 7.81 (d, 2 H, J 8.7), 8.14 (d, 2 H, J 8.7) 251, 148 8 121¡¾123 yellow crystals 1737 1.59 (t, 3 H, J 7.3), 4.65 (q, 1 H, J 7.3), 7.81 (t, 1 H, J 8.7), 8.14 (d, 1 H, J 8.7), 8.70 (d, 1 H, J 8.7), 8.73 (s, 1 H) 251, 148 9 124¡¾126 yellow powder 1719 1.53 (d, 3 H, J 7.3), 4.60 (q, 1 H, J 7.3), 7.80 (d, 1 H, J 8.5), 7.91¡¾ 7.96 (m, 2 H), 8.35 (t, 1 H, J 8.6) 251, 148 2A 132¡¾134 light yellow flakes 1783, 1769 1.24 (t, 3 H, J 7.2), 2.54 (s, 3 H), 4.30 (q, 2 H, J 7.2), 7.88 (d, 2 H, J 8.7), 8.25 (d, 2 H, J 8.7) 251, 176 9A 142¡¾144 light yellow flakes 1731, 1530,c 1350c 2.47 (s, 3 H), 7.55 (d, 1 H, J 8.5), 7.89¡¾7.94 (m, 2 H), 8.44 (d, 1 H, J 8.5) 249, 148 1B 58¡¾60 white flakes 1737 1.59 (d, 3 H, J 8.6), 1.92 (s, 3 H), 5.52 (q, 1 H, J 8.6), 7.47 (m, 5 H) 248, 104 2B 89¡¾91 red granules 1731 1.25 (t, 3 H, J 7.3), 1.61 (d, 3 H), 1.95 (s, 3 H), 4.39 (q, 2 H, J 7.3), 5.50 (q, 1 H, J 8.5), 7.60 (d, 2 H, J 8.7), 8.25 (d, 2 H, J 8.7) 320, 176 3B 51¡¾52 white granules 1746 1.60 (d, 3 H, J 8.5), 1.95 (s, 3 H), 2.46 (s, 3 H), 5.53 (q, 1 H, J 8.5), 7.39 (m, 4 H) 262, 118 4B .red liquid 1743 1.58 (d, 3 H, J 8.5), 2.20 (s, 3 H), 4.63 (q, 1 H, J 8.5), 7.26 (d, 2 H, J 9.0), 7.55 (d, 2 H, J 90) 326, 182 5B 68¡¾70 white granules 1743 1.31¡¾2.08 (m, 10 H), 1.66 (d, 3 H, J 8.5), 2.02 (s, 3 H), 4.62 (m, 1 H), 5.75 (q, 1 H, J 8.5) 254, 84 6B 85¡¾86 white granules 1746 1.32 (t, 3 H, J 7.5), 1.54 (d, 3 H, J 8.5), 1.94 (s, 3 H), 4.01 (q, 2 H, J 7.5), 5.47 (q, 1 H, J 8.5), 6.93 (d, 2 H, J 8.5), 7.32 (d, 2 H, J 8.5) 292, 148 7B 130¡¾131 light yellow powder 1734, 1545,c 1360c 1.65 (d, 3 H, J 8.5), 1.98 (s, 3 H), 5.47 (q, 1 H, J 8.5), 7.79 (d, 2 H, J 9.0), 8.46 (d, 2 H, J 9.0) 293, 267 8B 107¡¾109 light yellow needles 1737, 1550,c 1350c 1.65 (d, 3 H, J 8.5), 1.95 (s, 3 H), 5.48 (q, 1 H, J 8.5), 7.81 (t, 1 H, J 9.0), 8.64 (d, 1 H, J 9.0), 8.78 (m, 2 H) 293, 148 9B 104¡¾106 yellow needles 1740, 1560,c 1355c 1.65 (d, 3 H, J 8.5), 1.96 (s, 3 H), 5.45 (q, 1 H, J 8.5), 7.50 (d, 1 H, J 9.0), 7.68 (t, 1 H, J 9.0), 7.93 (t, 1 H, J 9.0), 8.34 (d, 1 H, J 9.0) 293, 148 a CO; bMass unit of the molecular ion and the base peak. c NO2 . J. CHEM. RESEARCH (S), 1998 627

ISSN:0308-2342    

DOI:10.1039/a801789a

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

Alumina in Methanesulfonic Acid (AMA) as a New Efficient Reagent for Direct Acylation of Phenol Derivatives and Fries Rearrangement. A Convenient Synthesis of o-Hydroxyarylketones Hashem Sharghi* and Babak Kaboudin Department of Chemistry, Shiraz University, Shiraz 71454, Iran Alumina in methanesulfonic acid is used to prepare o-hydroxyarylketones, by acylation of phenol and naphthol derivatives with carboxylic acids and Fries rearrangement of phenolic esters. The Friedel�}Crafts acylation is one of the most popular reactions for the synthesis of aromatic ketones,8 and direct acylation of phenol derivatives, using AlCl3 or TiCl4 as a promoter, also provides useful synthetic methods for the preparation of o-hydroxyarylketone derivatives.9�}11 However, treatment of the aluminium residue has, some- times, induced environmental problems and the drastic reaction conditions have caused some severe side reactions.On the other hand, acid chlorides or acid anhydrides are commonly used as acylating reagents in these reactions.These reagents are usually prepared from carboxylic acids, and, therefore, it would be useful if the acylations could be carried out by using carboxylic acids as acylating reagents.12�}14 An alternative method is the Fries rearrange- ment of acyloxy benzenes or naphthalenes which provides useful routes to these compounds.15 The acid�}base proper- ties of metal oxide supports have a signiRcant role in the selectivity exhibited by heterogeneous catalysts.19a�}d One of the most common solid supports in heterogeneous catalysis is alumina, which has been used as a dehydrating agent in aromatic cyclodehydration.20a,b We herein present work that describes the direct acylation of phenol derivatives with car- boxylic acids by a mixture of acidic alumina (type 504C) in methanesulfonic acid (AMA).We have also noticed that AMA catalyses the Fries rearrangement of acyloxybenzenes for the preparation of o-hydroxyarylketones (Scheme 2).The reaction of 1d with 2d at 100 8C for 12 h in methane- sulfonic acid a€orded 3d in 15% yield. Unfortunately, the extension of the reaction time, and the increase of the reaction temperature, decomposed the reaction mixture,18 and a darkened solid, which would dissolve in organic solvents, was obtained. Reaction of 1d with m-cresol in the presence of alumina failed in chlorobenzene, toluene and 1,2-dichloroethane when boiled under re�Pux for 24 h.In nitrobenzene, however, compound 5d was obtained in 20% yield. Since attempts to prepare 3d were unsuccessful, atten- tion was turned to methanesulfonic acid/alumina mixtures, which have not yet been used for this purpose. The reaction of 1d (2 mmol) with 2d (2 mmol) in methanesulfonic acid (1 mL) and acidic alumina (0.2�}0.3 g) at 100 8C for 12 h produced 3d in 50% yield. When the reaction was carried out at 140 8C, 3d was produced in 85% yield after 1 h. The extension of this new reagent to the Fries rearrangement of 5d was also successful and 3d was produced in 70% yield after 2 h (Table 2).The reaction of benzoic acid derivatives with m-cresol and Fries rearrangement of m-tolylbenzoate derivatives in the presence of AMA a€ord 2-hydroxyarylketones in high yields (Table 2). The results clearly show that the reactions seem to be faster when the aromatic part of the acid carries electron-donating groups. Acetic acid, cyclo- hexylcarboxylic acid, phenylacetic acid, hexanoic acid and 11-bromoundecanoic acid were also employed as acylating reagents.Fries rearrangement of m-tolylalkanoates also occurs in the presence of AMA and a€ords the desired products in excellent yields. Upon reaction of o-cresol with benzoic acid and Fries rearrangement of corresponding ester, the para isomer was obtained in high yield. With a J. Chem. Research (S), 1998, 628�}629 J. Chem. Research (M), 1998, 2678�}2693 Table 2 Comparison of results obtained from the reaction of phenol derivatives with carboxylic acids and Fries rearrangements of phenolic esters in the presence of AMA Aa Bb Entry Product 3 and ester 5 R1 R2 R3 R4 Time (t/min) Yield (%)c Time (t/min) Yield (%)c 1 a H CH3 H Ph 10 86 120 60 2 b H CH3 H o-ClC6H4 25 82 60 81 3 c H CH3 H m-CH3C6H4 5 90 60 80 4 d H CH3 H m-BrC6H4 60 85 120 70 9 i H CH3 H CH3 5 85d 15 80 13 m H CH3 H Br-(CH2)10 5 80 30 80 14 n H F H CH3 120 63d 180 60 15 o H OH H CH3 30 82d �} �} 18 r OH H H Ph 60 83 �} �} 22 v H H CH3 Ph 20 10(90)e 50 15(85)e 23 w H H Cl Ph 60 13(87)e 90 15(85)e 24 x H OH H Ph 30 85 �} �} 25 y H H CH3 PhCH2 5 12(88)e 10 15(85)e 26 z H H CH3 CH3 5 8(92)e 10 15(85)e 28 b' a-Naphthol CH3(CH2)4 20 91 15 60 29 c' Pyrogallol CH3 20 83d �} �} 30 d' NO2 H H Ph 720f �} 720 �} 31 e' H CH3 H p-NO2-C6H4 720 �} 720 �} aDirect acylation method.bFries rearrangement phenolic esters. cYields refer to isolated yield. dReaction was carried out at 120 8C. eValues in parentheses are referred to the yield of 4-acylated product.fIn this case 15% ester was produced. *To receive any correspondence. 628 J. CHEM. RESEARCH (S), 1998�uorine group at the meta and para positions, acylation and Fries rearrangement give the corresponding 2-hydroxy isomer in good yields. Three mechanistic pathways are proposed in the literature for the Fries rearrangement: (a) intramolecular,23±25 (b) intermolecular26±28 and (c) bimolecular.29±34 Mechanistic studies show that the acylation reaction in AMA occurs through a prior esteri®cation, followed by a Fries rearrange- ment of the phenolic ester by an intermolecular mechanism.In summary, AMA is introduced as an e�cient reagent in the direct acylation reactions of phenol and naphthol derivatives with carboxylic acids, and in Fries rearrange- ments of acyloxy benzene and naphthalene derivatives. The present methods have the following advantages: (a) the reagent is readily available, safe to handle and inexpensive; (b) the procedure is simple; (c) the reaction times are very short, and the reaction can be performed with a wide range of carboxylic acids and phenol derivatives; and (d) workup is easy.Further investigations to develop other synthetic reactions using AMA are now in progress. Techniques used: 1H NMR, IR and mass spectrometry References: 38 Schemes: 4 Table 1: Reaction of m-bromobenzoic acid (1d) with m-cresol (2d) in the presence of some Lewis and some protic acids Table 3: The reaction of o-chlorobenzoic acid (1b) with m-cresol (2b) in AMA Table 4: Progress of the Fries rearrangement of the ester 5b Received, 5th January 1998; Accepted, 16th June 1998 Paper E/8/00158H References cited in this synopsis 8 G.A. Olah, Friedel±Crafts Chemistry, Wiley-Interscience, New York, 1973. 9 (a) B. M. Trost and M. G. Saulnier, Tetrahedron Lett., 1985, 26, 123; (b) L. Crombie, R. C. F. Jones and C.J. Palmer, Tetrahedron Lett., 1985, 26, 2933. 10 G. N. Dorofeenko and V. V. Tkachenko, Khim. Geterotsikl. Soedin., 1971, 7, 1703; Chem. Abstr., 1972, 76, 153503k. 11 G. Sartori, G. Casnati and F. Bigi, J. Org. Chem., 1990, 55, 4371. 12 G. Fodor, J. Kiss and M. Szekerke, J. Org. Chem., 1950, 15, 227. 13 (a) R. M. G. Roberts and A. R. Sadri, Tetrahedron, 1983, 39, 137; (b) M. Hino and K. Arata, J. Chem. Soc., Chem. Commun., 1985, 112; (c) B. Chiche, A. Finiels, C. Gauthier and P.Geneste, J. Org. Chem., 1986, 51, 2128; (d) T. Keumi, K. Yoshimura, M. Shimada and H. Kitajima, Bull. Chem. Soc. Jpn., 1988, 61, 455. 14 S. Kobayashi, M. Moriwaki and I. Hachiya, Tetrahedron Lett., 1996, 12, 2053. 15 R. Martin, Org. Prep. Proced. Int., 1992, 24, 369. 19 (a) K. Tanabe, Solid Acids and Bases, Academic Press, New York, 1970; (b) M. C. Kung and H. H. Kung, Catal. Rev. Sci. Eng., 1985, 27, 425; (c) K. Tanabe, Catalysis by Acids and Bases, Elsevier, Amsterdam, 1985; (d) K. Tanabe, M. Misono, Y. Ono and H. Hattori, New Solid Acids and Bases, Elsevier, Amsterdam, 1989. 20 (a) F. A. Vingiello and A. Borkovec, J. Am. Chem. Soc., 1956, 78, 3205; (b) G. H. Posner, Angew. Chem., Int. Ed. Engl., 1978, 17, 487. 23 Y. Ogata and H. Tabuchi, Tetrahedron, 1964, 20, 1661. 24 N. M. Gullinane and B. F. R. Edwards, J. Chem. Soc., 1958, 2926. 25 A. Furka and T. Szel. Gibson and L. S. Hart, J. Chem. Soc., Perkin Trans 2, 1991, 1343. 27 (a) I. M. Dawson, J. L. Gibson, L. S. Hart and J. S. Littler, J. Chem. Soc., Perkin. Trans 2, 1985, 1601. 28 M. R. Banks, J. Chem. Soc., Perkin Trans 1, 1986, 507. 29 J. R. Norell, J. Org. Chem., 1973, 38, 1924. 30 E. H. Cox, J. Am. Chem. Soc., 1930, 52, 352. 31 A. M. El-Abbady, F. G. Baddar and A. Labib, J. Chem. Soc., 1961, 1083. 32 C. R. Hauser and E. H. Man, J. Org. Chem., 1952, 17, 390. 33 A. Schonberg and A. Mustafa, J. Chem. Soc., 1943, 642. 34 D. S. Tarbell and P. E. Fanta, J. Am. Chem. Soc., 1943, 65, 2169. Scheme 2 J. CHEM. RESEARCH (S), 1998 629

ISSN:0308-2342    

DOI:10.1039/a800158h

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

Azo Dyes as Side Chains in Liquid Crystalline Oligomers for Holographic Application Oliver Haak,a Cheung-Bok Jeoung,a Andreas Pawlik,a Peter Boldt,*a Walter Grahn,*a Franz-Heinrich Kreuzer,b Horst Leigeberb and Hans-Peter Weitzelb aInstitute fu�â r Organische Chemie, Technische Universita�â t Braunschweig, D-38092 Braunschweig, Germany bConsortium fu�â r elektrochemische Industrie GmbH, Zielstattstra��e 11, D-81379 Mu�â nchen, Germany In a systematic study on materials for holographic data storage, a wide variety of azo dyes of different shapes and optical properties were covalently bound to cholesteric liquid crystalline oligosiloxanes; some of these materials exhibit high holographic efficiency and/or sensitivity but no general correlation between the holographic writing efficiency and/or the sensitivity with the structure was found.Most promising materials for optical storage are nematic or cholesteric liquid crystalline polymers that possess arylazo groups as side chains.2 The general structure of our liquid crystalline materials is shown in Scheme 1 with a simple azo dye as an example.They are composed of an octacyclo- siloxane backbone with diphenyl- and cholestanyl-p- hydroxybenzoates and the azo dyes as side chains. They were made by palladium-catalysed hydrosilylation of the appropriate alkenes with the oligosiloxane.5 A HeCd laser (442 nm) and a NdYAG laser (with fre- quency doubled emission at 532 nm) were used in the holo- graphic experiments as the writing beam.The holographic eciency was measured with a HeNe laser (633 nm, reading beam). The structural variations of the azo dyes were carried out for the following reasons: (1) To tune the position of the long wavelength absorption band by variation of the strength of the electron-acceptor group.6 (2) To generate a hypsochromic shift of the long wavelength absorption band by donor�}donor substitution, by acceptor�}acceptor substi- tution and by steric hindrance of the azo bridge.6 (3) So as to investigate the in�Puence of the length of the spacer on the liquid crystalline properties.(4) To study the e€ect of side-on instead of end-on binding on the mesogenic properties. (5) To get some information on the e€ect of the length of the photomechanically switched molecular part: the eciency of the writing process should be higher the more the liquid crystalline order is disturbed, i.e. the longer the free part of the switching azo molecule is at the photo- chemical isomerization.Simple azo dyes were made by the usual methods.8 Styryl and arylethynyl groups were introduced into the azo dyes by palladium-catalysed cross-coupling reactions.9 The results of the optical measurements, the long wave- length absorption bands, the optical densities (OD) of the siloxane Rlms, the eciencies (E€ ) and the sensitivities (S) of the holographic writing process at 442 and 532 nm are given in Table 1.Some of these materials exhibit high holographic e- ciency and/or sensitivity. But for a given azo dye/oligo- siloxane system no prediction of the holographic optical storage properties can be made: as expected, the systems absorbing at short wavelengths have low ODs at 532 nm J. Chem. Research (S), 1998, 630�}631 J. Chem. Research (M), 1998, 2701�}2735 Scheme 1 Table 1 Optical properties of the arylazo dyesa Dye lmax (nm, sol.) OD442 OD532 Eff442 Eff532 S442 S532 5c 464 >4 4 24 26 1 2.1 5d 476 >4 4 21 16 1.3 1.2 5e 486 2.6 2.7 22 29 1.2 6 5f 446 >4 0.9 17 40 0.8 1.4 5g 458 >4 4 9 23 1 1.7 6a 442 >4 2.7 16 30 0.5 0.3 6b 424 >4 0.8 5 9 0.2 0.2 6c 408 >4 0.25 11 12 0.3 0.03 7c 438 0.9 0.05 23 1 1.1 0.01 7d 438 0.5 0.02 24 0.2 2 0.05 7e 436 0.8 0.08 28 0.2 1.4 0.01 7f 436 0.33 0.03 10 0.2 0.3 0.03 7g 464 1.9 0.4 25 31 0.5 0.7 7h 470 0.35 0.13 21 15 0.8 0.4 7i 448 0.5 0.08 17 10 1.9 0.3 7j 446 0.6 0.08 20 15 3.3 0.6 7k 442 0.2 0.05 7 0.4 0.11 0.01 7l 458 0.2 0.08 4 7 0.07 0.06 8a 464 1.8 0.2 0.1 0.1 0.01 0.01 9a 436 4 0.55 21 18 1.9 1.3 9e 464 3.6 1.9 15 34 3.2 2.7 9f 464 4 3.2 22 32 2.8 3.2 9h 454 4 1.2 26 24 3.2 5.5 10a 450 >4 2.5 30 34 3.4 6.6 10b 450 >4 2.4 25 35 3 6.1 11c 380 3.8 0.12 15 5 1.8 0.06 13a 438 >4 0.9 18 26 3.1 3.5 13b 438 >4 0.06 19 0.1 1.6 0.01 13c 420 >4 0.07 31 17 1.4 0.1 13d 438 >4 0.2 34 20 1.4 0.4 13f 420 >4 0.05 15 0.1 1 0.01 aAbsorption wavelengths in solution, all other measurements in an oligosiloxane matrix.*To receive any correspondence. (E-mail: P.Boldt@tu-bs.de and W.Grahn@tu-bs.de). 630 J. CHEM. RESEARCH (S), 1998(connected with low eciencies and sensitivities). Never-theless some of these compounds exhibit high values. Nofurther relationship seems to exist between the structure orthe properties of the azo dye moieties and the E or S. It isnoteworthy that completely dierent molecules, i.e. extendedarylazostilbenes and arylazoimines and a simple azo dye,exhibit the best values.The nancial support of the Bundesministerium fu rBildung und Forschung (project no. 03 M 4059) is gratefullyacknowledged.Techniques used: IR, UV¡ÓVIS, 1H and 13C NMR, EI and FABmass spectrometryReferences: 17Schemes: 2Fig. 1: Absorption spectra of 5e, in methylcyclohexane (q), atmax=452 nm normalized to OD 1; after irradiation for 5 minwith a xenon lamp 250 W cm£¾2, Schott lter GG 385 nm (r);in siloxane matrix (w), at max1483 nm normalized to OD 1.The strong absorption below 350 nm is owing to the oligosiloxanemoietyFig. 2: Dependency of the eciency (E ) on the optical density. Eof 7c¡Óf, k; 8a; 13b, f<1Fig. 3: Dependency of the sensitivity (S) on the optical density. S of6a¡Óc; 7c¡Óf, h, j¡Ól; 11c; 13b¡Ód, fE0.6Fig. 4: Correlation of the sensitivity (S) with the eciency (E ) ofoligosiloxanes with arylazo dye side chainsTable 2: Method of preparation and analytical data of the arylazocompounds 5a¡Ói, 6a¡Óc, 7a¡Ól and 8a,bTable 3: Method of preparation and analytical data of the (E)-arylazo stilbenes 9a¡Ók, 11a¡Óc and arylazoimines 10a,bTable 4: Method of preparation and analytical data of the benzo-thiophenes 12a,b and the arylazo compounds 13a¡ÓfReceived, 25th March 1998; Accepted, 26th June 1998Paper E/8/02336KReferences cited in this synopsis2 (a) M.Eich and J. H. Wendor, Makromol. Chem., RapidCommun. 1987, 8, 59; (b) K. Anderle, R. Birenheide, M. Eich andJ. H. Wendor, Makromol. Chem., Rapid Commun. 1989, 10, 477;(c) R. Ortler, C. Bra uchle, A. Miller and G. Riepl, Makromol.Chem., Rapid Commun. 1989, 10, 189; K. Ichimura, Y. Suzuki,T. Seki and Y. Kawanishi, Makromol. Chem., Rapid Commun.1989, 10, 5; G. S. Kumar and D. C. Neckers, Chem. Rev., 1989,89, 1915; A. Shishido, O. Tsutsumi and T. Ikeda, Mater. Res.Soc. Symp. Proc. 1996, 425, 213; B. Fleck, D. A. Dowling andL. Wenke, J. Modern Opt., 1996, 43, 1485.5 G. Riepl, F.-H. Kreuzer and A. Miller, Consortium fu r elektro-chemische Industrie GmbH, EP 333022, 1989, Mu nchen.6 For a discussion of the inuence of the hindrance on theUV¡ÓVis-spectra see: (a) O. Haak, Dissertation, TechnischeUniversita t, Braunchweig, 1994; (b) C. B. Jeoung, Dissertation,Technische Universita t, Braunschweig, 1993.8 H. Zollinger, Color Chemistry, 2nd edn., VCH Verlagsgesell-schaft, Weinheim, 1991.9 C.-B. Jeoung, O. Haak, W. Grahn and P. Boldt, J. Prakt. Chem.,1993, 335, 521.J. CHEM.

ISSN:0308-2342    

DOI:10.1039/a802336k

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

A Novel Synthesis of 5-Hydrazono-4a,7- dihydrodipyrazolo[3,4-b;4,3-e]pyridin-3(2H)-ones and their Cyclization to Fused Triazines Fawzy A. Attaby,*a Sanaa M. Eldinb and Mohamed A. A. El-Neairya aChemistry Department, Faculty of Science, Cario University, Giza, Egypt bNational Research Center, Dokki, Egypt Several 5-hydrazono-4a,7-dihydrodipyrazolo[3,4-b;4,3-e]pyridin-3(2H)-ones and triazines derived thereform were synthesized via the reaction of diazotized dipyrazolopyridines with active-methylene-containing reagents.In conjunction with our previous work1±5 and the reported biological activities of pyrazolopyridines8 as well as pyrazo- lotriazines9 we were interested to synthesize new compounds for our medicinal chemistry programme and to investigate novel chemical transformations. It has been found that 5-diazotized-4a,7-dihydrodi- pyrazolo[3,4-b;4,3-e]pyridin-3-(2H)ones (3a±c) couple with malononitrile (4a) to give the 4-amino-6,9-dihydro-10H- pyrazolo[40,30:5',6']pyrido[2',3':3,4]pyrazolo[5,1-c] [1,2,4]- triazin-10-one derivatives 6a±c, respectively.In contrast to the behaviour of 4a towards coupling with 3a±c, it was found that both ethyl cyanoacetate (4b) and o-cyanoaceto- phenone (4c) coupled with each of 3a±c to give the corre- sponding 5-hydrazono derivatives 5d±i, respectively, which cyclized to give the 4-amino-6,9-dihydro-10H-pyrazolo- [40,30:5',6']pyrido[2',3':3,4]pyrazolo[5,1-c][1,2,4]triazin-10-one derivatives 6d±i respectively (Scheme 1).The synthetic potential of 3a±c was further investigated through their reaction with other active-containing reagents. Thus 3a coupled with each of ethyl benzoylacetate (8a) and diethyl malonate (8b) to give the corresponding 5-hydrazono derivatives 9a±f respectively. Compounds 9a±f were cyclized J. Chem. Research (S), 1998, 632±633 J. Chem. Research (M), 1998, 2754±2768 Scheme 1 *To receive any correspondence. 632 J. CHEM. RESEARCH (S), 1998Scheme 2 in boiling ethanol that contained triethylamine to a€ord 10a�}f, respectively.The synthetic potential of 3a�}c was also further investigated through their reactions with cyanothio- acetamide (11a) and cyanoacetamide (11b) to a€ord the corresponding 5-hydrazono derivatives 12a�}f, respectively. Compounds 12a�}f readily underwent addition to the CN group to give the pyrazolo[40,30:5',6']pyrido[2',3':3,4]- pyrazolo[5,1-c][1,2,4]triazin-10-ones 15a�}f, respectively (Scheme 2). The synthons 3a�}c also reacted with each of acetylacetone (16a) and ethyl acetoacetate (16b) to a€ord the corresponding 5-hydrazono derivatives 17a�}f, respect- ively.Compounds 17a�}f were cyclized to a€ord 18a�}f, respectively, via loss of water. Techniques used: 1H NMR, FT-IR, UV and mass spectrometry Schemes: 2 References: 13 Table 1: Physical and analytical data of the compounds prepared Table 2: IR and 1H NMR spectral data of the newly synthesized compounds Received, 4th March 1998; Accepted, 25th June 1998 Paper E/8/01793J References cited in this synopsis 1 F. A. Attaby and S. M. Eldin, Phosphorus Sulfur, Silicon Relat. Elem., 1991, 55, 59. 2 F. A. Attaby, L. I. Ibrahim, S. M. Eldin and A. K. El-Louh, Phosphorus Sulfur, Silicon Relat. Elem., 1992, 73, 127. 3 F. A. Attaby and S. M. Eldin, Arch. Pharm. Res., 1990, 13, 274. 4 F. A. Attaby, Arch. Pharm. Res., 1990, 13, 342. 5 F. A. Attaby, S. M. Eldin and M. Abdel-razik, Phosphorus Sulfur, Silicon Relat. Elem., 1995, 106, 21. 8 M. Komura, R. Ishida and H. Uchida, Arzneim-Forsch., 1992, 42, 48. 9 D. R. Rao, S. P. Raychaudhuri and V. S. Verma, Int. J. Tropical Plant Dis., 1994, 12, 177. J. CHEM. RESE

ISSN:0308-2342    

DOI:10.1039/a801793j

出版商:RSC    

年代:1998

数据来源: RSC