Studies on DMDO-mediated benzylidene acetal oxidation
摘要:
We have shown that dimethyldioxirane (DMDO) can be used to effect an oxidative partial deprotection of benzylidene acetals derived from both 1,2- and 1,3-diols to afford hydroxy benzoate products. A wide range of functional groups are tolerated, and good to excellent yields are usually observed. The reactions are easy to perform and produce little waste other than acetone. (C) 2008 Elsevier Ltd. All rights reserved.
Synthesis of optically active 2-hydroxy monoesters via-kinetic resolution and asymmetric cyclization catalyzed by heterometallic chiral (salen) Co complex
作者:Wenji Li、Santosh Singh Thakur、Shu-Wei Chen、Chang-Kyo Shin、Rahul B. Kawthekar、Geon-Joong Kim
DOI:10.1016/j.tetlet.2006.03.042
日期:2006.5
The binuclear chiral (salen) Co complexes bearing Lewis acids of Al and Ga catalyze regio- and enantioselective ring opening of terminal epoxides with carboxylic acids. The ring opened product of epichlorohydrin with carboxylic acids followed by cyclization step in the presence of catalyst and base represent straightforward, efficient methods for the synthesis of enatiomerically enriched (>99% ee)
作者:Emilia Caselli、Giovanni Tosi、Arrigo Forni、Maria Bucciarelli、Fabio Prati
DOI:10.1016/s0014-827x(03)00189-7
日期:2003.10
Levodropropizine, an antitussive drug, was prepared in high enantiomeric excess in three steps, starting from dichloroacetone (2). Monosubstitution of 2 with sodium benzoate and subsequent baker's yeast reduction stereoselectively afforded the corresponding chlorohydrin in 73% ee, which was converted to levodropropizine and enantiomerically enriched up to 95% ee by fractional crystallisation.