Base-Induced Cyclization of Derivatives of Bispropargylated Acetic Acid to m-Toluic Acid

Abstract

A base-induced cyclization reaction of 1,1-bispropargyls has been examined. Alkali treatment of 2,2-bispropynyl acetic acid derivatives in aqueous ethanol mostly provided 3-methylbenzoic acid. Investigations on substituent effects indicate the requirement of an electron-withdrawing group causing CH acidity and the center of the dipropargylic structure. Besides, an intramolecular hydrogen transfer causing the rearrangement of one terminal alkyne into a corresponding allene appears to be essential. Despite an unsatisfying conversion yield of below 40%, the reaction is interesting due to the mild cyclization conditions.

Key words

alkyne–allene isomerization - vinylogous enolate - 6-endo-dig cyclization - bispropargyl - intramolecular proton transfer

• References and Notes

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