Phase-Transfer-Catalysis of Direct Mannich Reaction of Malonates with N-Carbamoylimines

Significance

The authors present a phase-transfer-catalyzed direct Mannich reaction of malo­nates with N-carbamoyl (Boc and Cbz) imines generated in situ from the corresponding α-amido sulfones (1). As imine precursors α-amido sulfones derived from variously substituted aromatic, as well as from enolizable aliphatic aldehydes can be used. Applying this strategy, a broad scope of Mannich products of the general type 2 are obtained in mostly high yields and moderate to- when Cbz groups were used - high enantiose­lectivities. Furthermore, these Mannich products are shown to be direct precursors of enantio­enriched β-substituted N-carbamoyl-protected β-amino acids via a transesterification-decarboxylation sequence.