Catalytic Asymmetric Conjugate Allylation of Coumarins

A catalytic asymmetric conjugate allylation was successfully developed to synthesize potential pharmacologically active 4-allyl-2-oxochroman skeletons. A dual activation strategy was employed by using N,N'-dioxide-Yb(OTf)(3) to activate coumarins and using (CuOTf)(2)•C(7)H(8) to activate tetraallyltin via transmetalation, respectively. Good yields and enantioselectivities were obtained under mild conditions.