Polonovski- and Pummerer-type Reactions and the Nef Reaction

In 1927 the Polonovskis reported their discovery that treatment of a tertiary amine N-oxide with acetic anhydride or acetyl chloride results in a rearrangement in which one of the alkyl groups attached to nitrogen is cleaved and the N-acetyl derivative of the corresponding secondary amine and aldehyde are obtained (equation 1).1,2 Although originally considered to be a mild method for N-demethylation of tertiary amines, it is now recognized that the Polonovski reaction provides ready access to iminium ions, enamines, tertiary amides and/or secondary amines and aldehydes.3–6