Syntheses of 2-Alkyl-2-cyclopentenones and 2-Alkylcyclopentanones from 1-Alkyl-cis-2, 3-epoxycyclopentanols

Abstract

A mixture of 2-alkyl-2-cyclopentenone (2) and 2-alkylidenecyclopentanone (3) was obtained in good yield by the treatment of 1-alkyl-cis-2, 3-epoxycyclopentanols (1) in an aqueous mineral acid. In case of the use of aqueous 10% hydrochloric acid, 1-alkyl-3-chloro-1, 2-cyclopentanediols (4) were produced remarkably. It was presumed that (2) and (3) were produced via the enol forms by intramolecular dehydrochlorination of (4).cis-1, 2-Diols (5) were produced nearly quantitatively by the reduction of (1) with LiAlH4 in dried tetrahydrofuran. When (5) were reacted in an aqueous mineral acid, 2-alkylcyclopentanones (6) were obtained in 8895% yield. It was suggested that (6) were produced via the enol form by dehydration of (5).