3-Alkoxypropenals as precursors in the synthesis of conjugated and semiconjugated polyenes: methyl-substituted octa- and nona-tetraenes

Abstract

Vinylic and allylic Grignard reagents react cleanly and rapidly with 3-ethoxypropenal and 2-methyl-3-ethoxypropenal to produce excellent yields of conjugated and semiconjugated dienals useful in the subsequent preparation of substituted octa- and nona-trienols. Variations in the substitution pattern allow the preparation and isolation of 2-, 3-, and 4-methylocta-1,3,5,7-tetraenes, nona-1,3,5,8-tetraene, and 5-methylnona-1,3,5,8-tetraene in good yield from the octa- and nona-trienols. Thus oxopropenylation of unsaturated Grignard reagents allows the straightforward preparation of numerous previously unknown and uncharacterized polyenes.