Diastereoselective hydroformylation of Δ4-steroids with rhodium-phosphite catalysts

The hydroformylation of two steroidal substrates, namely 17 beta -acetoxyandrost-4-ene 1 and 3 beta, 17 beta -diacetoxyandrost-4-ene 2, with a rhodium tris(O-tert-butylphenyl)phosphite catalyst was investigated. In both cases, the major reaction product was 4 beta -formyl-17 beta -acetoxy-5 beta -androstane 3, which was isolated and characterized by X-ray diffraction and NMR techniques. This reaction is the first example of catalytic carbonylation to the beta face of a steroid backbone. The effect of reaction temperature, the pressure at which the reaction was completed and the ligand:Rh ratio on the regio- and stereoselectivity of the reaction is also discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.