Synthesis of 7-dehydrocholesterol through hexacarbonyl molybdenum catalyzed elimination reaction

The efficiency of hexacarbonyl molybdenum catalyzed elimination reaction of the allylic acetates has been improved by the presence of O,N-bis(trimethylsilyl) acetamide in the reaction medium. The methodology is particularly well employed for the elimination of 7-acetoxycholesterol-3-acetate(cholestrol-3,7-diacetate) for which the resulting product obtained was exclusively 5,7-homoannular diene(7-dehydrocholesterol-3-acetate). Good yield is achieved (up to 70 %) while decreasing the side products formation and reducing the costs as compared to the previously used procedures. Hexacarbonyl molybdenum elimination reaction is greatly influenced by the reaction temperature, at low as well as at high temperature low yield of the homoannular diene product is separated while at moderate conditions of temperature high products formation is observed. KEY WORDS: Hexacarbonyl molybdenum, Elimination, Deacetoxylation, 7-Dehydrocholesterol, BSA Bull. Chem. Soc. Ethiop. 2011, 25(2), 247-254.