Cycloaddition of 2(1H)-pyridones having a methoxycarbonyl group to 1,3-butadiene derivatives

The cycloaddition of 4-methoxycarbonyl-2(1H)-pyridones to silyloxydienes gave isoquinolone derivatives in reasonable yields. Furthermore, the cycloaddition of 6-methoxycarbonyl-2(1H)-pyridones to 2,3-dimethyl-1,3-butadiene produced cycloadducts (isoquinolone and quinolone derivatives) and double cycloadducts (phenanthridone derivatives). The activation energies using Gaussian 98 with RHF/3-21G level of 4- and 6-methoxycarbonyl-2(1H)-pyridones coincided with the experimental facts.