The Alkylation of Ambident Anions. IV. The Alkali Metal and Silver Salts of Formanilides

Abstract

Systematic studies of the alkylation of a number of ambident or ambifunctional anions have been reported. For the vast majority of the anions examined reaction involved competition between carbon and a heteroatom and few competition between two heteroatoms. A study of the factors influencing the site of alkylation of the ambident anion of mono-N-substituted amides, where competition is between oxygen and nitrogen, has been undertaken. With the alkali metal and tetraalkylammonium salts of formanilide anions, the alkylation product is invariably the corresponding N-alkylformanilide. No detectable O-alkylation is observed as the solvent is varied from nonpolar through polar aprotic solvents, the alkylating agent through the various benzyl halides and para-substituted benzyl halides and the para-substituent on the formanilide from strongly electron donating (—OCH 3 ) through strongly electron withdrawing (—NO 2 ) groups. In contrast, with the silver formanilide salts, O-alkylation predominates but here the O:N alkylation ratio varies with the parameters examined. A rationale based on thermodynamic υs. kinetic control and reaction of dissociated υs. undissociated anion is presented to predict the site of reaction in these and other ambident systems.