Mannich-like three-component synthesis of α-branched amines involving organozinc compounds: ReactIR monitoring and mechanistic aspects

The infra-red spectroscopic in situ examination of the Mannich-like three-component reaction between organozinc reagents, amines and aldehydes is described, revealing that two distinct pathways are favored, depending on the nature of the starting amine. While reactions involving primary amines proceed via in situ-formed imines, reactions involving secondary amines rather imply a hemiaminal as the key intermediate species.