摘要:
An efficient method for catalytic asymmetric allylic alkylation (AAA) of allylic phosphates with vinylaluminum reagents is reported. The vinylmetal reagents are prepared by reaction of commercially available DIBAL-H and a terminal alkyne. The resulting vinylaluminum reagent can be used directy, without isolation or purification. AAA reactions are promoted in the presence of 0.5-2.5 mol % of a readily available chiral N-heterocyclic carbene (NHC) complex and 1-5 mol % commercially available and air stable Cu salt (CUCl2-2H(2)O). The desired products are typically obtained within 2-12 h in 74% to 95% isolated yield, 77% to >98% ee, and in >98% E selectivity: >98% S(N)2' selectively is obtained in all but one instance (90%). The hydroalummation/catalytic AAA sequence can be performed in a single vessel, on gram scale.