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).