Cage ketones from dimethyl-1,4-benzoquinones and quinonoid carbanions ; A charge-transfer controlled synthesis

Abstract

3-Methyl-1,4-naphthoquinon-2-ylmethyl anion ( la ) adds 2,6-dimethyl-l,4-benzoquinone reversibly giving, in addition to products of types already known, a derivative ( 2 ) of the cage hydrocarbon decahydro-4,l,7-ethanylylidene-naphthalene which can be obtained as the major product. A similar reaction with 2, 5-dimethyl-l,4-benzoquinone gives a similar cage compound ( 3 ) but derived from decahydro-8,2,5-ethanylylidenenaphthalene ( 14 ), a member of the twistane series. This reaction can be modified to yield the more complex cage compound ( 4 ) derived from the hydrocarbon tetradecahydro-5,8,9,10-[l,2,3,4] butatetraylanthracene. Since the only anions that initiate cage formation in benzoquinones have themselves quinonoid structures it is suggested that charge-transfer complexation aligns the interacting rings and promotes reversibility in Michael reactions, thus allowing steric repulsions to control the regiospecificity.