Modified aza-claisen rearrangement: Generation and isomerization of allyl enammonium salts

Base-promoted reaction of ketones and diethyl (diazomethyl)phosphonate in the presence of allylic amines affords allylic enamines in good yields. These enamines undergo 3,3]-sigmatropic rearrangement upon alkylation and heating at 80°C to iminium salts which can be hydrolysed to aldehydes. The procedure allows generation of quaternary carbon centers under mild reaction conditions.