Electron deficient heteroaromatic ammonioamidates—XVI: The synthesis and photochemistry of ethyl N-(2-methyl-4-methylene-6,7-methylenedioxy- 3,4-dihydro-3-quinazolinyl)-N-phenylcarbamate

Irradiation through Pyrex of the N-(dihydroquinazolinyl)carbamate 3c in ethanol furnishes mixtures (Scheme 1) of two photoisomers (2c and 4a), two dimeric products: the 1,2-bis(4-quinazolinyl)ethane 5 and the (p-phenylene)dicarbamate 6, and of ethyl N-phenylcarbamate. The latter, as well as compounds 4a and 5 are formed also on irradiation of compound 2c. The radicals 9 and 10, formed by homolysis of the N-N bond of 3c as well as of the CH₂-N bond of 2c are considered to be the primary photoproducts of both reactions, and to lead, by various recombination processes, to compounds 2c, 4a, 5 and 6, and to ethyl N-phenylcarbamate by hydrogen abstraction. It is not clear at present whether concerted photochemical 1,3] shifts contribute to the formation of 2c and 4a.