Palladium-Catalyzed Synthesis of β-Lactams by Carbonylation of Vinyl Aziridines

Abstract

The synthesis of trans-β-lactams 3 by the palladium-catalyzed carbonylation of vinyl aziridines 1 or 2 is reported. The same products were obtained in each case from either the pure trans- or cis-substrate, or from a racemic mixture. Both electron-rich and electron-deficient aromatic groups were equally tolerated. Alkyl-substituted vinyl aziridine 4 required higher pressures of CO for the reaction to take place and, in contrast to the cinnamyl derivatives, gave the Z-stereoisomer. Intriguingly, silyl-substituted substrate 6 showed a preference for formation of the δ-lactam 7 at low pressures of CO. Increasing the pressure however, and hence slowing the equilibration between palladium acyl species, led predominantly to β-lactam 8 as a mixture of diastereomers.