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901.
Krasovsky A. L. Pissarev S. A. Nenajdenko V. G. Balenkova E. S. 《Russian Chemical Bulletin》2003,52(8):1791-1796
A procedure was developed for the synthesis of previously unknown CF3-containing -azolyl-substituted enones by the reactions of 1,1,1-trifluoro-4-sulfonyl-3-butene-2,2-diols with various azoles. Quaternization of the azolyl group with methyl triflate afforded -azolium-substituted enones in quantitative yields. 相似文献
902.
903.
Trisubstituted methylalkenes react with methyl sulfite at 25°C in the presence of BF3 · Et2O in the ene-type fashion to give the corresponding methallyl sulfinates. Such compounds can also be prepared under considerably milder conditions by the Et2AlCl-catalyzed reaction of thionyl chloride with mono- and dienes followed by methanolysis of intermediate alkyl sulfinyl chlorides. These reactions represent a new method for terminal functionalization of linear isoprenoids.Deceased Nov.1, 1992.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 105–107, January, 1993. 相似文献
904.
A kinetic and product study of the reaction of a series of α‐methyl‐substituted N‐methylpiperidines with thermally generated 1O2 in MeCN was carried out. It was found that as the number of α‐methyl groups (Me in α‐position relative to the N‐atom) increases, the rate of 1O2 quenching (physical plus chemical) slightly decreases. This finding shows that, with respect to the reaction rate, steric effects are much more important than electronic effects as the latter should have produced the opposite result. The opposite outcome was instead found for the chemical quenching that leads to the N‐demethylation products and N‐formyl derivatives. The same trend was observed for the ratio between N‐demethylation and formation of the N‐formyl derivatives (NH/NCHO ratio). All these results are consistent with the mechanism reported in Scheme 1 where an exciplex is first formed that by a H‐atom transfer process produces an α‐amino‐substituted C‐radical. The latter forms the product of N‐demethylation by one electron oxidation, or affords the N‐formyl derivative by radical coupling (Scheme 1). Similar results were obtained with N,N‐dimethylcyclohexanamine. However, this ‘acyclic’ amine exhibited behaviors quite distinct from those of the N‐methylpiperidines series, with respect to reaction rate, extent of chemical quenching, and NH/NCHO ratio. 相似文献
905.
Gas chromatography (GC) was investigated for the determination of residual methyl methacrylate (MMA) in heat-processed poly(methyl methacrylate) (PMMA) denture base material emphasizing recovery and validation. Standard solutions of MMA and emulsion-polymerized PMMA in dichloromethane were analysed, before and after distillation by a room-temperature air stream into a liquid nitrogen trap, and in the presence of PMMA by direct injection. Quantitative NMR analysis using dimethyl sulphoxide as internal calibration standard in deuterated chloroform solutions provided validation. Good concordance was observed between results under all conditions; no problems arose from direct injection of PMMA solution for GC. Good straight line responses in log-log plots were generally observed. For GC and MMA: log-log calibration curve (slope: 0.9552 +/- 0.0051, r2: 0.9992, n = 32) indicated some non-linearity (t = 8.875, p approximately 4 x 10(-10)). Distillation gave slope: 0.9751 +/- 0.0213 (NS versus unity; t = 1.172, p > 0.25). For PMMA solutions, distillation (r2: 0.9301) gave greater scatter than direct injection (r2: 0.9704). For NMR: log-log plot of calculated versus actual MMA (slope: 0.9363 +/- 0.0157, r2: 0.9969, n = 13) again indicated non-linearity (t = 4.0682, p = 0.0019). PMMA solutions gave slope: 0.9477 +/- 0.0328, r2 = 0.9858 (NS versus unity; t = 1.5941, p = 0.13). Determination of MMA in PMMA by GC is recommended. 相似文献
906.
Correlation times for rotation of deuterated methyls in crystalline leucine, valine, and cyclo-L-alanyl-L-alanine are calculated with molecular dynamics and compared with NMR data. The simulations distinguish between methyls having different steric environments in the crystal, yielding correlation times differing by a factor of up to 30 for methyls within a given crystal. MD and NMR correlation times agree to within a factor of 2. However, averaging over nonequivalent methyls can yield correlation functions that, although actually multiexponential, are well fit by single exponentials. This may have significance for interpreting NMR data; previous NMR data did not distinguish between the methyls in these crystals. Adiabatic rotational barriers calculated with the X-ray structure differ from effective barriers during simulation by up to +/-1 kcal/mol; the difference indicates that dynamical effects have a significant role in determining rotational correlation times. 相似文献
907.
908.
The title compound (1) was treated with NaH at room temperature in anhydrous DMF to give a sodium salt (containing nitrogen anion)which could shift the methyl group from oxygen to nitrogen atom to form N-methyl phosphinic acid as the reaction temperature was increased to 120 ℃.Three nitro derivatives containing 5,10-dihydrophenophosphazine ring system were prepared for the investigation on the above reaction mechanism which would be possible regarded as a special inter-molecular substitution.viz.,the nucleophilic nitrogen anion from one molecule of 1 attacked the cabon atom of the O-methyl of another 1.In addition,the chemical structures of seven compounds containing 5,10-dihydrophenophosphazine ring system involved in the experiment were confirmed by IR,^1 H NMR,^31P NMR and mass spectroscopy. 相似文献
909.
Piperonyl methyl ketone was obtained by oxidizing isosafrole with hydrogen peroxide and formic acid.Dianion of ethyl acetoacetate reacted with piperonyl methyl ketone and 5,6-dihydro-6-methyl-6-piperonyl-2H-pyran-2,4-dione was prepared,which reacted with substituted anilines in the presence of ethyl orthoformate to obtain 3-anilinomethylene-5,6-dihydro-6-methyl-6-piperonyl-2H-pyran-2,4-diones.Their structure were confirmed by ^1HNMR and elemental analysis. 相似文献
910.