Diels-Alder reaction of (S)-2-p-tolylsulfinyl-2-cyclopentenone with Dane's diene: an efficient approach to the enantioselective preparation of perhydro-cyclopenta[a]phenanthrenes

Abstract The reactions of (S)-2- p -tolylsulfinyl-2-cyclopentenone with Dane's diene catalyzed by EtAlCl 2 yields adducts easily desulfinylated into optically pure perhydro-cyclopenta[a]phenanthrenes. The endo - (controlled by CO group) and regio- (controlled by the substituent at C-2 of diene) selectivities of the asymmetric Diels-Alder reaction are complete. The π—facial selectivity is also very high and dependent on both the sulfinyl configuration and the amount of EtAlCl 2 used.