Rearrangements of steroids

The reactions of 4α-acetoxy-5α- hydroxyl- and acetoxy- cholestanes and 4β-acetoxy-5β- hydroxyl- and acetoxy- cholestances with H₂SO₄-Ac₂O-AcOH and BF₃. Et₂O-Ac₂O respectively have been investigated. The course of the reactions has been found to be dependent on the orientation of the C(4) and C(5) substituents. A study of the rearrangements of 3β, 6β-diacetoxy-5α-cholestan-5-ol (5b) and 4β-acetoxy-5βcholestan-5-ol (26b) with D₂SO₄-DOAcAc₂O gave rearranged products which contain no deuterium. This contrasts with previous suggestions that olefins and cyclopropanes are intermediated in backbone rearrangements. The effects of electron withdrawing substituents in rings A, B, and D have been investigated in the reactions of 5α- hydroxyl- and acetoxy- cholestanes with H₂SO₄-Ac₂O-AcOH and BF₃.etherate-Ac₂O. An unsuccessful attempt to synthesis 9β-cholest-5,7-dienes (85) and 3β-acetoxy- and benzoyloxy- 10α-cholest-5,7-dienes (83) with tetracycanoethylene (TCNE), maleic anhydride and 4-phenyl-1,2,4-triazoline-3,5-dione have been investigated. A 5α, 8α-cycloadduct has been formed between TCNE and 3β-benzoyl-10α-cholest-5,7-diene the only known example of such a ring B cycloadduct