A study on the activation of carboxylic acids by means of 2-chloro-4,6-dimethoxy-1,3,5-triazine and 2-chloro-4,6-diphenoxy-1,3,5-triazine

Activation of carboxylic function by means of 2-chloro-4,6-disubstituted-1,3,5-triazines 1 and 2 leading to triazine esters was found to be a multistep process with participation of quarternary triazinylammonium salts 3-6 as the intermediates, with the rate of reaction strongly dependent on the structure of the tertiary amine. The studies on alkylation of tertiary amines with CDMT revealed the two-step process A(N) + D-N, and zwitterionic addition product 9 was identified by H-1 NMR spectroscopy. Semiempirical modeling of the reaction as well as measured nitrogen and chlorine isotope effects also support this mechanism.