A Base-Mediated Rearrangement of the Benzylic 1,5-Hexadipyridynyl Moiety.

Abstract

We report a previously unrecognized base-mediated rearrangement of a benzylic 1,5-hexadipyridynyl moiety. Upon exposure to base, we show this structural motif to rearrange into a constrained vinyl-pyridine substituted cyclobutene. Computational modeling indicates that the rearrangement takes place following a route involving stepwise deprotonation, shifted reprotonation, and 4-π-electrocyclization. Furthermore, non-base-mediates rearrangements, through well-known Cope-like [3,3]-sigmatropic shifts, were found to be high in energy and therefore take a backseat to the base-mediated pathway. This rearrangement may provide a novel reactivity pathway of conjugated systems for synthetic methodology development.