Dimerization of Alkyl Vinyl Ketones Catalyzed by Triphenylphosphine

Abstract

Dimerization of alkyl vinyl ketones [1] in the presence of triphenylphosphine as a catalyst was studied. In the reaction of 1-penten-3-one [1a], 4-methylene-3, 7-nonanedione [5 a] was obtained. The dimerization of [1 b-h] gave dimers, 2-methylene-1, 5-dione derivatives [5b-h], in 42-85% yields. The reactions were considered to proceed through phosphonium betaine intermediates which attack the j9-carbon of the alkyl vinyl ketones as in the Michael type addition.