Studies in heterocyclic polymers, Pt VIII the preparation of o-cyanobenzoic acid and some derivatives

Abstract

In a study of the synthesis of polyiminoimides the preparation of 2-cyano-benzoic acid (VI) and some derivatives has been examined. Both the symmetrical (XII) and the asymmetrical (XIII) phthaloyl dichlorides were found to give good yields of (VI) upon ammonolysis with (XII) the more efficient precursor. Conversion of the acid (VI) to its acid chloride (IX) was readily effected with PCl5. A number of substituted 2-cyanobenzanilides were prepared from (IX) and their cyclisation to the related 2-substituted-3-iminoisoindolinones studied using DSC. The nature of the substituent appeared to have little influence upon the rate of cyclisation which occurred spontaneously upon melting the parent anilide. The synthesis of mixed dicyanodicarboxylic acids from pyromellitic dianhydride and from benzophenone — 3,3′,4,4-tetracarboxylic acid dianhydride was also studied but difficulties were encountered in resolving the products.