Enantioselective Synthesis of Polycyclic Ketones by Desymmetrisation of Bis(phenylsulfonyl)alkenes with Chiral Alcoholates. Control of the Absolute Configuration by Simple Modification of the Chiral Auxiliary

Treatment of polycyclic bis(phenylsulfonyl)alkenes with chiral alcoholates, followed by acidic work-up, affords enantioselectively alfa-phenylsulfonyl ketones. The enantioselectivity is total with monomethylated hydrobenzoin and of opposite configuration with respect to that obtained with hydrobenzoin itself. Thus, starting from a bis(phenylsulfonyl)alkene, it is possible to obtain either the R or S polycyclic ketone by the use of the same chiral auxiliary (hydrobenzoin) and a simple modification (methylation of one of the hydroxy functions).