Use of phosphite amides in the synthesis of polyamides

The preparation of polyamides by the phosphite amide procedure was investigated. The yield of amidation was determined in the reaction of diethyl- or o-phenylenephosphite derivatives of piperidine, piperazine, or trans-2,5-dimethylpiperazine with either mono- or dicarboxylic acids. Higher yields were obtained by using diethyl phosphite derivatives; however, for both types of derivatives the yields were never greater than 90%. Only low molecular weight polymers could be obtained under optimum reaction conditions. In the polycondensation of (+)-trans-1,3-cyclohexanedicarboxylic acid or (+)-trans-1,2-cyclohexanedicarboxylic acid with phosphite derivatives of either piperazine or trans-2,5-dimethylpiperazine, the optical rotation of the polymers was lower than the rotation of the corresponding polyamides prepared by the interfacial condensation procedure with dicarboxylic acid chlorides. It was shown that an intermediate mixed anhydride was formed during the amidation reaction. This may account for the observed racemization.