Substituent effects in the catalytic hydrogenation of steroidal Δ4- and Δ5-3,3-ethyleneketals

Abstract

A number of isomeric Δ4- and Δ5-3,3-ethylenedioxy steroids were prepared to study the substituent effects on the relative amounts of 5α and 5β ketals formed during catalytic hydrogenation. Hydrogenation of Δ5-3,3-ethylenedioxy steroids with palladium on charcoal as catalyst yielded 5α steroids exclusively. The Δ4-3,3-ethylenedioxy compounds yielded mixtures of 5α and 5β ketals in which slightly more 5β product was formed than was obtained by catalytic hydrogenation of the equivalent Δ4-3-oxo steroid. Substituents in the C-11 position of the Δ4 ketals diminish the amount of 5β steroid formed during hydrogenation.