Metal-catalyzed rearrangements of allylic esters

It has been shown that Pd(CH 3 CN) 2 Cl 2 catalyzes the rearrangement of allylic esters. Carbamates rearrange more rapidly than acetates which in turn rearrange more rapidly than carbonates. Allylic carbamates are more rapidly isomerized by Pd(CH 3 CN) 2 Cl 2 than by Hg(OCOCF 3 ) 2 . The rearrangement proceeds well except in cases where the central carbon of the allylic system is fully substituted.In contrast to the reported rearrangement of allylic carbamates by Hg 2+ and previous reports of Pd 2+ -catalyzed rearrangements of allylic esters, this work showed the latter are extremely E specific; thus, E allylic acetates yield equilibrium mixtures free of Z allylic isomers, under conditions in which Z allylic acetates are unreactive. This E specificity is applied to stereospecific 1,3-diene synthesis from bis E,Z-allylic acetates.