Bisoxazolidine-Catalyzed Enantioselective Alkynylation of Aldehydes

摘要

The ever-increasing industrial and academic demand for enan-tiopure chemicals has been accompanied by the development of numerous asymmetric synthetic methods utilizing highly efficient chiral catalysts and auxiliaries.Ideally,a practical asymmetric catalyst is inexpensive,readily available in both enantiopure forms,and provides high yields and enantioselectivities for a wide range of substrates in various reactions.Among the many chiral catalysts reported to date,a relatively small number derived from rigid C_2-symmetric ligands including BINOL,BOX,salen,DIOP,DUPHOS,and TADDOL have proved to be exceptionally versatile and effective.