Selective para metalation of unprotected 3-methoxy and 3,5-dimethoxy benzoic acids with n-butyl lithium–potassium tert-butoxide (LIC–KOR): synthesis of 3,5-dimethoxy-4-methyl benzoic acid

The potassium salt of 3-methoxy and 3,5-dimethoxy benzoic acids undergoes deprotonation at the position para to the carboxylate group selectively when treated with LIC–KOR in THF at −78°C and it has been extended to the synthesis of 3,5-dimethoxy-4-methyl benzoic acid.