Preparation of Calix[4]arene Alkylamine Derivatives by Mannich Reaction and use as Phase-Transfer Catalysts for Esterification Reaction

In this study, 5,11,17,23-tetrakis(N-ethylpiperazine)methyl]-25,26,27,28-tetrahydroxycalix4]arene (3) and 5,11,17,23-tetrakis(4-carboethoxy-N-piperidino) methyl]-25,26,27,28-tetrahydroxycalix4]arene (4) were synthesized in one step according to the Mannich reaction by the treatment of calix4]arene with a secondary amine (N-ethylpiperazine, ethyl-4-piperidincarboxylate) and formaldehyde. The calix4]arene derivatives (3, 4) were characterized by a combination of FTIR, ¹H NMR and elemental analyses. The synthesized compounds were used in an esterification reaction as the phase transfer catalyst. The catalytic efficiency of the calix4]arenes 3 and 4 was evaluated by carrying out the ester-forming reaction of alkali metal carboxylates (sodium butyrate or sodium caprylate) with p-nitrobenzyl bromide. It was observed that the ester-forming reaction of alkali metal carboxylates with p-nitrobenzyl bromide, using calix4]arene-based catalyst 3 as a phase-transfer catalyst in dichloromethan, provided the best yields.