Selective mono-benzylation of methylene active compounds with dibenzyl carbonate: benzylation of phenol

Abstract

Dibenzyl carbonate (DBzlC) has been used to benzylate phenylacetonitrile, benzyl phenylacetate and phenol. In refluxing N,N-dimethylformamide (DMF) as solvent, and in the presence of K₂CO₃ phenol yielded benzyl phenyl ether and phenylacetonitrile the monobenzylated compound 2,3-diphenylpropionitrile. Likewise, in refluxing N,N-diethylformamide (DEF), benzyl phenyl acetate gave the benzyl 2,3-diphenylpropionate. Selectivity in mono-C-benzyl derivatives was 98–99% at a conversion up to 90%. Such unusually high selectivity is explained in terms of a mechanism involving, initially, carboxybenzylation followed by benzylation, rather than direct benzylation.