Synthesis and X-ray crystal structure determination of 1,3-bridged β-lactams: Novel, anti-Bredt β-lactams

Article abstract of DOI:10.1021/ja00185a043

The first successful syntheses of several anti-Bredt β-lactams from alkyl acetoacetate in 11-14 steps are described. The key cyclization reaction involves the Rh(II)-catalyzed carbene insertion of the diazo derivatives 12, 23, and 31 into the N-H bond of the β-lactams. These (±)-1,3-bridged β-lactams have IR absorptions of 1780-1795 cm^-1 for the β-lactam carbonyls. The structure of 32d has been determined by X-ray crystallography; this derivative exhibits a C-N (amide) bond length of 1.414 (4) A and a β-lactam pyramid with the nitrogen atom 0.51 A above the basal plane of three carbon atoms.