PYROLYSIS OF AMINONITRILES, CYANOHYDRAZONES, AND CYANOACETAMIDES .1. ELIMINATION-REACTION OF DIHYDRO-4,6-DIMETHYL-2-OXOPYRIDINE-3-CARBONITRILES AND SUBSTITUTED BENZALDEHYDE CYANOACETYLHYDRAZONES

Pyrolysis of the Schiff bases of dihydro-4,6-dimethyl-2-oxopyridine-3- carbonitriles (1-5) has been studied. These compounds eliminate via a six-membered transition state to produce substituted benzonitriles and 2-hydroxy-4,6-dimethylpyridine-3-carbonitrile. These eliminations are unimolecular First-order reactions. The kinetic data gave a good corr elation with sigma(0) values of the substituents on the aryl group wit h rho = 0.83 at 520 K. Utilization of the pyrolytic reaction in synthe sis of various benzonitriles is considered, and mechanistic informatio n has been obtained by comparing the kinetic data and product analysis of the Schiff bases with their open-chain substituted benzaldehyde cy anoacetylhydrazones (6-9) analogues. (C) 1996 John Wiley & Sons, Inc.