Palladium-Catalyzed Potassium Enoxyborate Alkylation of Enantiopure Hajos−Parrish Indenone To Construct Rearranged Steroid Ring Systems

Here we report the stereo- and regiospecific C-6 alkylation of a trans-inden-5-one (from optically pure Hajos−Parrish ketone) with allylic electrophiles. Use of this alkylation procedure has led to an improved synthesis of the benz[f]indene ring system and the first enantiospecific total syntheses of the cyclopenta[b]anthracene and cyclopenta[b]phenanthrene ring systems (two synthetic routes).