REACTIONS OF 2-PYRIDONE AND N-METHYL-2-PYRIDONES WITH N-SUBSTITUTED MALEIMIDES

The thermal reactions of 2-pyridone with several N-substituted maleimides gave the 1 : 2 Michael and Diels-Alder(MDA) reaction products in addition to the 1 : 1 Michael (M) reaction products and the Diels-Alder(DA) adducts. A large variety of DA adducts were obtained and charactarized for N-methyl-2-pyridones. The MDA products were found to be formed by the M reactions followed by the DA reactions. The kinetic analyses gave the following information. The electron-withdrawing N-substitue-nts of the maleimides accelerate the M reactions more than the DA reactions, and give larger product ratio, exo/endo. The activation energies for the DA reactions are 24~31 kcal-mol-1 which are close to those obtained for retro-DA reactions and become large when polar solvents or acetic acid are used. These abnormal phenomena are attributed to the unique dipole-interac-tions in these reactions. © 1979, The Chemical Society of Japan. All rights reserved.