Magnesium Coordination-Directed N-Selective Stereospecific Alkylation of 2-Pyridones, Carbamates, and Amides Using α-Halocarboxylic Acids

A general inversion-stereospecific, N-selective alkylation of substituted 2-pyridones (and analogues), amides, and carbamates using chiral alpha-chloro- or bromocarboxylic acids in the presence of KOt-Bu (or KHMDS) and Mg(Ot-Bu)(2) is reported. The resulting a-chiral carboxylic acid products were isolated by crystallization in good chemical yields and in high ee (>90% ee). Mechanistic evidence suggests that the reaction proceeds through 2-pyridone O-coordinated Mg carboxylate intermediates, which afford the product through an intramolecular S(N)2 alkylation.