Palladium(0)-Catalyzed Asymmetric Cycloaddition of Vinyloxiranes with Heterocumulenes Using Chiral Phosphine Ligands: An Effective Route to Highly Enantioselective Vinyloxazolidine Derivatives
作者:Chitchamai Larksarp、Howard Alper
DOI:10.1021/ja964335l
日期:1997.4.1
Cycloaddition reaction of 2-vinyloxiranes with carbodiimides using Pd2(dba)3·CHCl3, and TolBINAP as the chiral ligand, in THF at ambient temperature, afforded 4-vinyl-1,3-oxazolidin-2-imines in 70−99% yield and in up to 95% ee. The stereoselectivity is strongly influenced by the structure of the chiral phosphine ligands and substrates, as well as by the reaction conditions. The enantiodetermination
使用 Pd2(dba)3·CHCl3 和 TolBINAP 作为手性配体,在 THF 中,2-乙烯基环氧乙烷与碳二亚胺的环加成反应,在室温下,以 70-99% 的产率得到 4-乙烯基-1,3-恶唑烷-2-亚胺并且高达 95% ee。立体选择性受手性膦配体和底物的结构以及反应条件的强烈影响。对映测定步骤假定为氮亲核试剂对 π-烯丙基钯中间体的亲核攻击。使用相同的催化剂体系使 2-乙烯基环氧乙烷与异氰酸酯反应以高产率但不超过 50% ee 得到 4-乙烯基-1,3-恶唑烷-2-酮。