Steroidal sulphur compounds. Part I. Pyrolysis and absolute configuration of steroidal phenyl sulphoxides

Abstract

The chirality of the sulphur atom in eight steroidal sulphoxides has been shown to influence the direction of pyrolytic elimination to give olefins. Consideration of the product ratios and relative stabilities of the transition states lead to the assignment of absolute configuration to the sulphoxides, and provided evidence that the incipient double bonds are well developed in the transition states. Axial sulphoxides eliminate faster than equatorial sulphoxides. The ultraviolet and optical rotatory dispersion characteristics of the sulphoxides were recorded; the R- and S-sulphoxides displayed positive and negative Cotton effects, respectively, which were independent of the configuration of the steroidal residue.