The thermal rearrangements of pentadienylammonium ylides. Competing [1,2], [3,2], and [5,2] rearrangements

Abstract

The pentadienylammonium ylides (9) rearrange thermally to give the products (14), (15), (16), and (17) by two distinct reaction pathways; the first is formally a forbidden sigmatropic rearrangement and it involves an interacting radical pair having some translational freedom giving predominantly the products of [1,2] and [5,2] rearrangements, and the second is formally an allowed [3,2] sigmatropic rearrangement which involves an interacting radical pair indistinguishable from the transition state of a concerted pericyclic process.