Lewis acid mediated diastereoselective and enantioselective cyclopropanation of Michael acceptors with sulfur ylides

The reaction of N-enoyloxazolidinones with diphenylsulfonium isoproylide in the presence of Lewis acids is explored. The diastereoselectivity of the reaction of N-enoyloxazolidinones 1a and 1b with diphenylsulfonium isopropylide could be mediated by the addition of some Lewis acids. The reaction of N-enoyloxazolidinone 4 with diphenylsulfonium isoproylide was also explored with chiral Lewis acids. When this reaction was run with bis(oxazoline) ligand 6 and a number of Lewis acids, product was obtained in as high as 95% ee. A loss of stereoselectivity was observed with less than stoichiometric amounts of Lewis acid.