Tricarbonyl(h6-arene)chromium(0) complexes as chiral auxiliaries. Homochiral b-lactams synthesis "via" [2 + 2] cycloaddition reaction

A highly enantioselective synthesis of b-lactams via a [2 + 2] cycloaddn., reaction of homochiral tricarbonyl [N-(2- methoxybenzylidene)aniline]chromium with ketenes is reported. Moreover the reaction of (+)-(1S)-tricarbonyl[4-methoxy- N-(2-methoxycinnamylidene)aniline]chromium with acetoxy ketene gives the corresponding 4-styryl-b-lactam, e.g. I, in good yield but with moderate stereoselection