The allenic Alder-ene reaction: constitutional group selectivity and its application to the synthesis of ovalicin

The scope of the novel allenic Alder-ene reaction using Rh(I) and Ir(I) catalysts has been extended to differentially substituted 1,1,3-trisubstituted allenes. This allenyl substitution pattern can give three possible cross-conjugated triene products. The selectivity of this transformation can be controlled by varying reaction temperature, solvent, and catalyst. Progress toward the synthesis of ovalicin using this triene forming protocol is described.