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Synthesis of β-lactams and x-amino acids by photochemical reactions of chromium carbene complexes

The photochemical reaction of chromium carbene complexes with imines has been developed into an efficient process for the synthesis of β-lactams. A new route to aminocarbene complexes, involving the reaction of Na2Cr(CO)5 with amides and trimethylsilyl chloride has been developed. By using this procedure, chiral, optically active aminocarbene complexes have been prepared, and their photochemical reactions with imines developed. Chiral, optically active β-lactams have been prepared with more than 90% diastereoselectivity by this procedure. Chiral, optically active aminocarbene complexes containing pendent alcohol groups have also been prepared. Photolysis of these produces aminolactones, which can be cleaved to natural and unnatural α-amino acids.