Lipase-catalyzed kinetic resolution of .gamma.-hydroxy phenyl sulfones
摘要:
Lipase PS (from Pseudomonas cepacia) catalyzed the enantioselective transesterification of racemic gamma-hydroxy-alpha,beta-unsaturated phenyl sulfones 1 and their alpha,beta-saturated derivatives 3 with vinyl acetate in an organic solvent (usually (i)Pr2O). Remarkably, in substrates 1 with (E)-stereochemistry, the enantioselectivity of the process was little influenced by the nature of the R chain. Hence, very high enantiomeric ratios (E greater-than-or-equal-to 45) were observed in substrates 1 bearing short (R = Me or Et), long (R = n-Cr6H13 or n-C10H21), bulky (R = (i)Pr), or functionalized R chains. The (R)-enantiomer was the fast-reacting enantiomer in all cases. Concerning the reactivity, the rate of the reaction decreased significantly with an increase in size or length of the R chain (reaction time for 50% conversion from 3.5 to 162 h). Less satisfactory enantioselectivities (E = 5-48) were obtained when the saturated substrates 3 were used instead of the corresponding alpha,beta-unsaturated alcohols 1.
Preparation of hydrindenones from 2-methylcyclopent-2-enone and the carbanion of (E)-but-2-enyldiphenylphosphine oxide: efficient enolate trapping with β-sulphonylvinyl ketones
作者:Richard K. Haynes、Simone C. Vonwiller
DOI:10.1039/c39870000092
日期:——
The β-sulphonylvinyl ketones (5), (7), (9), and (10), easily prepared from β-(phenylthio)propionyl chloride or from methyl vinyl ketone, react efficiently with the enolate produced by the conjugate addition of the carbanion of (E)-but-2-enyldiphenylphosphine oxide to 2-methylcyclopent-2-enone to provide in highly stereoselective fashion vinylogous β-diketones, two of which upon hydrogenation and aldol
Vinylsulfones have been efficiently synthesized by treatment of alkenes with sodium arene sulfinates using potassium iodide and sodium periodate in the presence of a catalytic amount of acetic acid at room temperature. The products are formed in high yields (87-95%) within 2.5-8 hours. vinylsulfone - alkene - arylsulfinate - synthetic methods Part 229 in the series ‘Studies on Novel Synthetic Methodologies’