反应详情

On the other hand dimedone is a cheap and readily available starting material for a multi-step synthesis of green ketone. In U.S. Pat. No. 4,147,672 the reduction of dimedone in 52% yield in a two-step reaction sequence to the α,β-unsaturated mono-ketone via the monotosylhydrazone (G. A. Hiegel et al., J. Org. Chem. 38, 3637 (1973)) is described. The catalytic hydrogenation of the ketone in the presence of palladium on charcoal gave 3,3-dimethylcyclohexan-1-one (no yield given) and subsequent ethynylation with ethyne in basic medium gave 1-ethynyl-1-hydroxy-3,3-dimethylcyclohexane in about 50% yield. Reaction with CuCl and allyl chloride in basic medium gave 1-(1-hydroxy-3,3-dimethylcyclohexyl)-pent-4-en-1-yne after distillation in 50% yield. Treatment with boric acid yielded (70%) a 2:3 mixture of 1-(3,3-dimethyl-cyclohex-1-ene-1-yl)- and -6-en-1-yl)-pent-4-en-1-ine which was transformed into a 2:3 mixture of the corresponding -pent-4-en-1-ones by treatment with 80% formic acid at 90° C.