Carboxymethylation of p,αββ-tetramethylstyrene by manganese(III) acetate. Reductive cyclization during treatment of the derived γ-aryl-γ-lactone with polyphosphoric acid to give 4-isopropyl-7-methyl-1-tetralone

Abstract

Oxidation of p, αββ-tetramethylstyrene (I) with manganese(III) acetate gave a lactone mixture in which the presence of 4-isopropyl-4-p-tolylbutane-4-olide (V) as the major component was infrarred from its n.m.r. spectrum. The formation of this lactone (V) is attributed to the addition of carboxymethyl radical [from manganese(III) acetate] to α-isopropyl-p-methylstyrene (II), arising from (I) by double-bond isomerisation. Treatment of the lactone mixture with polyphosphoric acid furnished in high yield 4-isopropyl-7-methyl-1-tetralone (VIII), identified by independent synthesis. This cyclization involves reduction by hydride transfer.