Conformational transmission. Part II. The effect of a 7,8-double bond on the enol acetylation properties of 3-oxo-5β-steroids

Abstract

The enol acetylation of 5β-cholest-7-en-3-one with isopropenyl acetate–sulphuric acid (kinetic control) yields a mixture of 5β-cholesta-2,7-dien-3-ol acetate and 5β-cholesta-3,7-dien-3-ol acetate. Treatment with perchloric acid–acetic anhydride altered the proportions of this mixture to the equilibrium ratio of 90·5 : 9·5. Thus the conformational transmission effect of the 7,8-double bond reverses the usual direction of enolisation by a factor equivalent to 3·0 kcal./mole.