Circular dichroism and optical rotatory dispersion of steroid 3-ethylenedithio-4-ketones and related compounds

Abstract

Optical rotatory dispersion (o.r.d.), circular dichroism (c.d.), and i.r. data for a series of 3-ethylene acetal, monothioacetal and dithioacetal derivatives of 4-oxo-steroids are discussed. In these systems, an axial sulphur substituent α to the carbonyl group greatly enhances the carbonyl Cotton effect, in the same way as an axial halogen substituent does. Cotton effects at shorter wavelengths (260–220 mµ) are ascribed to the n→σ* transitions of the sulphur atoms. The c.d. band at ca. 220 mµ is intense for dithioacetals and those monothioacetals which carry an axial sulphur atom adjacent to carbonyl. This grouping may therefore be considered as a dissymmetric chromophore.

The c.d. and o.r.d. curves of related sulphones and 4β-hydroxy-3-thioacetals, and of some steroid 3,4-hydroxyketones and their acetates, have also been measured.