Ruthenium-Catalyzed Oppenauer-Type Oxidation of 3β-Hydroxy Steroids. A Highly Efficient Entry into the Steroidal Hormones with 4-En-3-one Functionality

Abstract
Oxidation of 5-unsaturated 3β-hydroxy steroids 1 to the corresponding 4-en-3-one derivatives 2 can be performed efficiently by acetone at reflux in the presence of a catalytic system consisting of either (PPh3)3RuCl2 (3) and K2CO3 or [(C4Ph4COHOCC4Ph4)(μ-H)][(CO)4Ru2] (4). The reaction proceeds via a ruthenium-catalyzed dehydrogenation of 1 and subsequent hydrogen transfer to acetone with concomitant double bond migration.