New thermal rearrangements of vinylogous ketoketenes and related intermediates

Abstract

2-Oxopyran-5-carbaldehydes (e.g. 3) containing a trapping group in the 5-position rearrange thermally by a sequence involving electrocyclic ring opening, E/Z isomerisation and ring closure; a similar strategy has enabled the first cases of thermal interconversion of pyran-2-ones and 2-pyridones, and of automerisation of 2-pyridones to be identified.

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