Cyclopalladated ferrocenylimine: a highly effective catalyst for the borylation/suzuki coupling reaction

By extending the Winstein cyclization method to the steroid system, we developed a simple and efficient method for highly stereoselective construction of 6β,7β-methylene unit. This method involves an initial Grignard reaction with the 7-carbonyl group of 3β,17β-bis(tert-butyldimethylsilyloxy)androst-5-en-7-one (8) and then stereoselective reduction of the tertiary alcohol followed by a tandem oxidation/cyclopropanation reaction. The excellent yield, high stereoselectivity, and relatively mild reaction conditions should make this an attractive method for the preparation of 6β,7β-methylene derivatives in steroid.