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Synthesis of Polyamides by Direct Polycondensation with Diphenyl 2,3-Dihydro-2-oxo-3-benzothiazolyl Phosphate as a New Activating Agent

A new activating agent for amide condensations, diphenyl 2,3-dihydro-2-oxo-3-benzothiazolyl phosphate, was prepared by the reaction of 2(3H)-benzothiazolone with diphenyl phosphorochloridate in the presence of triethylamine in acetonitrile at room temperature. The new activating agent was found to be useful for the preparation of amides from carboxylic acids and amines. The direct polycondensation of dicarboxylic acids with aromatic diamines using the activating agent in the presence of triethylamine proceeded at room temperature to produce polyamides with inherent viscosities up to 1.1 dl g−1. Furthermore, the activating agent was used for the synthesis of polyamides from bis(oxo carboxylic acid)s or 2,6-pyridinedicarboxylic acid and 4,4′-oxydianiline.