Alkylation, aldol, and related reactions of O-alkanoyl- and 2-alkenoylTEMPOs (2,2,6,6-tetramethylpiperidine-N-oxyl): insight into the reactivity of their anionic species in comparison with esters and amides

The lithium anionic species generated from O-alkanoylTEMPOs upon treatment with LDA were first employed as a nucleophile for alkylation, Michael addition, direct aldol reaction, and others. The alkylation occurred smoothly at the methylene carbon, and no alkylation was found in the isobutyryl analogue, while silylation was scarcely attainable. Substitutions of the heteroatom were achieved by reaction with PhSSPh and DEAD. The reactivity of these anionic species is successfully extended to aldol reactions in which moderate anti or syn selectivity was executed with propionyl derivatives. Tandem Michael addition of lithium amide followed by aldol reaction was performed on the O-crotonoylTEMPOs.