TANDEM [2-CYCLOADDITION-CYCLOREVERSION REACTIONS IN HIGHLY POLAR MEDIA - A CONVERGENT ONE-POT ENTRY TO SUBSTITUTED ALKENES AND DIENES(2])

Reaction at room temperature between acyl chlorides and aromatic or al pha,beta-unsaturated aldehydes in the presence of a tertiary base and in 5M lithium perchlorate-diethyl ether (5M LPDE) as solvent yields su bstituted alkenes in satisfactory yields. The reaction is formally con ceived as a [2+2] cycloaddition between the aldehyde and the in situ f ormed ketene, followed by thermal decarboxylation of the intermediate 2-oxetanone. Ketene itself yields alpha,beta-unsaturated acids under t hese reaction conditions. Copyright (C) 1996 Published by Elsevier Sci ence Ltd