Gold(I)-catalyzed highly diastereo- and enantioselective alkyne oxidation/cyclopropanation of 1,6-enynes.

ABSTRACT

A highly enantioselective oxidative cyclopropanation of 1,6-enynes catalyzed by cationic Au(I)/chiral phophoramidite complexes is presented. The new method provides convenient access to densely functionalized bicyclo[3.1.0]hexanes bearing three contiguous quaternary and tertiary stereogenic centers with high enantioselectivity (up to e.r. 982). Control experiments suggest that the quinoline moiety of the ß-gold vinyloxyquinolinium intermediate in the reaction plays an important role in promoting good enantioselectivity through a transitional auxiliary effect in the transition state.