Selective activation of primary carboxylic acids by electron-rich triarylbismuthanes. Application to amide and ester synthesis under neutral conditions

Abstract

On being heated in benzene in the presence of tris(methoxyphenyl)bismuthanes 1b–1e, primary carboxylic acids are selectively activated to couple with amines and alcohols to produce the corresponding amides and esters in satisfactoy yields, while secondary, tertiary and aromatic carboxylic acids remain unaffected. 2-Benzylmalonic acid is similarly converted into its corresponding diamides and diesters, but 2,2-dibenzylmalonic acid suffers extensive decarboxylation and, in the presence of aromatic olefins, it undergoes a novel [3 + 2]-type cycloaddition reaction to form 4-substituted 2,2-dibenzyl-4butanolides in low to fair yields.