A direct and mild conversion of tertiary aryl amides to methyl esters using trimethyloxonium tetrafluoroborate: A very useful complement to directed metalation reactions

The scope and generality of a direct process for the conversion of tertiary amides directly to methyl esters has been investigated. The process involv es a two-step, one pot procedure in which a tertiary amide is first treated with trimethyloxonium tetrafluoroborate to generate an imidate intermediat e which is then hydrolyzed, generally by the addition of saturated aqueous sodium bicarbonate solution. Although this process fails for aliphatic amid es, very good yields are realized for a variety of amides derived from arom atic carboxylic acids. Steric hindrance at the N-alkyl group is well tolera ted; thus N,N-dimethyl, -diethyl, and -diisopropyl amides can all be utiliz ed successfully (C) 2000 Elsevier Science Ltd. All rights reserved.