A convenient method for the conversion of hindered carboxylic acids to N-methoxy-N-methyl (Weinreb) amides

The conversion of sterically hindered carboxylic acids to N-methoxy-N-methyl amides can be efficiently carried out with 1.1 equiv of methanesulfonyl chloride, 3 equiv of triethylamine, and 1.1 equiv of N-methoxy-N-methylamine. N-methoxy-N-methylmethanesulfonamide, the major byproduct for these reactions, can be removed by placing the product mixture under vacuum for 14-24 hours.