Synthesis of Mannich bases from electrochemically generated iminium salts in the presence of silyl enol ethers

The formation of Mannich bases from the reaction of silyl enol ethers with N-methyl-N-mesitylmethyleniminium salt, generated by the electrochemical oxidation of N,N-dimethylmesidine, was studied. Important factors influencing the reaction are: (a) the silyl enol ether must be nucleophilic enough to react with the iminium salt and, at the same time, must be more difficult to oxidize than the tertiary amine, (b) the product of the reaction must not be oxidized at the operating potential. Examples are presented in this paper illustrating the successes and limitations of this reaction.