Enantioselective Base-Free Phase-Transfer Reaction in Water-Rich Solvent
作者:Rongjun He、Seiji Shirakawa、Keiji Maruoka
DOI:10.1021/ja906821y
日期:2009.11.25
development of enantioselective phase-transfercatalysis for preparing important natural products or physiologically active compounds is quite attractive and challenging in terms of environmental consciousness. Although quaternary ammonium salts as phase-transfer catalysts are believed to require base additives for phase-transferreactions, we have discovered that even without any base additives, the enantioselective
phase‐transfer reaction system can be applied to highly enantioselectiveconjugateaddition and aldol reactions under the influence of chiral bifunctional ammonium bromides as key catalysts. The structure of the chiral ammonium enolate intermediate is discussed based on the single‐crystal X‐ray structures of relevant ammonium salts and the importance of bifunctional design of catalyst is clearly explained in the