Diels-Alder reactions of nitro-2(1H)-pyridones with 2,3-dimethyl-1,3-butadiene

Diels-Alder (DA) reactions of 3- or 5-nitro-2(1H)-pyridones and nitro-2(1H) -pvridones containing a methoxycarbonyl group with 2,3-dimethyl-1,3-butadie ne were examined. The DA reactions of 3-nitro-2(1H)-pyridones in this paper represent, to the best of our knowledge, the first report of DA reactions of 3-substituted 2(1H)-pyridones and consequent production of isoquinolones . Performing the same reactions with 5-nitro-2(1H)pyridones yielded quinolo nes. DA reactions of 2(1H)-pyridones with nitro and methoxycarbonyl groups produced isoquinolones, quinolones and phenanthridones (the double DA adduc ts), aromatized or hydrogenated. The substituent effect was evaluated by ca lculating the activation energy, using the ab initio MO method.