Reduction of a conjugated en-yne compound

摘要

A conjugated en-yne compound is reduced to a diene by treating with a reducing agent comprising chromous hydroxide in suspension in a liquid medium containing a compound having a hydroxyl group, e.g. water or alcohol, the reducing reagent having a pH of at least 7. The medium is made alkaline with a hydroxide of an alkali metal or an alkaline earth metal. The chromous hydroxide utilized may be prepared in situ, e.g. by the addition of chromous chloride, chromous sulphate or chromous acetate to a solution of alkali. Examples describe the reduction of compounds of the formula:- wherein R represents a 2,6,6-trimethyl-D 1-cyclohexeny radical and R1 a 2,6,6-trimethyl-D 2-cyclohexenylidine radical. Compound I is obtained by condensing 1-methoxy - 3 - methyl - 3 - hexene - 5 - yne with b -ionone. Compound II is obtained by rearranging and dehydrating the compound R-CH=CH-C. (OH).(CH3)-C­C-CH2-C.(OH).(CH3)-CH =CH2. Compound III is obtained by rearranging and dehydrating 1-hexynyl-b -ionol. Compound V is obtained by rearranging and dehydrating the compound R-CH=CH-C. (OH).(CH3)-C­C-CH.(CH3)=CH-CH3.