Acid-Induced Ring Opening of α-(Bis(methylthio)methylene)alkyl Cyclopropyl Ketones: A Novel Route to Substituted Cyclopentanones Through Carbocationic Cyclizations.

α-[Bis(methylthio)methylene]alkyl2-styrylcyclopropyl ketones lOa-d,f and their higher enyl analogues 10e,g undergo acid-induced ring opening and carbocationic cyclizations to afford substituted cyclopentanone derivatives. The structures of these products depend on the reaction conditions and the nature of the substituent in the aryl ring. The methodology has been extended to the synthesis of 11-oxosteroid precursors 22 and 25.