DIELS-ALDER REACTION OF 2-PYRIDONES HAVING AN ACYL OR A SULFONYL GROUP ON NITROGEN

Diels-Alder (DA) reaction of 5-methoxycarbonyl-2-pyridone, which has an electron-withdrawing acyl group at nitrogen, with 1,3-diene afforded 2-quinolone derivatives in modest yields. Further, DA reaction of 5,4-dimethoxycarbonyl-1-sulfonyl-2-pyridone gave 2-quinolone and 1-isoquinolone (1:1). DA reaction of 2-sulfonyl-1-isoquinolone afforded a functionalized phenanthridone. The site-selectivity was well correlated with the corresponding activation energies calculated using an ab initio molecular orbital method.