Enantioselective synthesis of tetrasubstituted allenes via addition/arylation tandem reaction of 2-activated 1,3-enynes

We report the development of a new class of multifunctional chiral guanidine/Pd(0) catalyst system for 1,4-addition/arylation tandem reaction. A variety of tetra-substituted allenes were readily accessible from three-component “one-pot” transformations of acyclic or cyclic 2-activated 1,3-enynes, malonates and halobenzenes under mild reaction conditions. High levels of yield and enantioselectivity were achieved in the construction of stereogenic center and axis using readily available acyclic guanidine-amides. The mechanistic studies suggest that the guanidine/Pd(0) collaboration has obvious synergism to both base-dominated conjugate addition, and Pd(0)-dominated Heck-type reaction.