Novel insertion, rearrangement and addition products from dihalogenocarbene reactions with 5(10)-unsaturated steroids

Abstract

Novel insertion, rearrangement and addition products from dibromocarbene and dichlorocarbene reactions with 5(10)-unsaturated steroids have been identified. The dihalogenocarbenes were prepared under phase-transfer conditions (CHBr₃– or CHCl₃–NaOH), and from CHBr₃–KOBu^t–Et₂O, phenyl(trichloromethyl)mercury and sodium trichloroacetate. Evidence that the major products arise from an initial dihalogenocarbene reaction on the α face of the molecule is reported. The major products obtained from addition of CBr₂ to 3,17-disubstituted estr-5(10)-enes, after ketal hydrolysis, were 19(S)-bromo-9α,19-cyclo-10α-androst-4-en-3-one and 3,′3′,19(S)-tribromo-3′H-9α,19-cyclocyclopropa[5,6]-5β, 10α-androstan-3-one derivatives together with the 19,19-dibromo-5α,19-cyclo-10α-steroid adduct. No products from addition of CBr₂ to the β face of the double bond, as previously reported, were identified. Reactions of CCl₂ gave, besides rearrangement products analogous to those obtained from CBr₂, a 5α-hydroxy-9α,19α-cycloandrostane derivative, the 9α-CHCl₂ insertion derivative and both α- and β-face addition products to the double bond. Structures were established by homonuclear and heteronuclear correlation and nuclear Overhauser effect NMR measurements and X-ray crystallography.