Tandem [2 + 2] cycloaddition-cycloreversion reactions in highly polar media: A convergent one-pot entry to substituted alkenes and dienes

Article abstract of DOI:10.1016/0040-4039(96)01562-6

Reaction at room temperature between acyl chlorides and aromatic or α,β-unsaturated aldehydes in the presence of a tertiary base and in 5M lithium perchlorate-diethyl ether (5M LPDE) as solvent yields substituted alkenes in satisfactory yields. The reaction is formally conceived as a [2 + 2] cycloaddition between the aldehyde and the in situ formed ketene, followed by thermal decarboxylation of the intermediate 2 oxetanone. Ketene itself yields α,β-unsaturated acids under these reaction conditions.