Electron deficient heteroaromatic ammonioamidates. Part 26. N-(quinazolin-3-io)amidates. Part 13. Phototransformations of an N-(quinazolin-3-io)thioamidate and of a 10bH-1,3,4-thiadiazolo[3,2-c]quinazoline, the ring isomer of an N-(quinazolin-3-io)thioamidate, and the photochemical formation of some 4,4′-biquinazolinyls

Irradiation of the N-(quinazolin-3-io)thioamidate (10a) in ethanol and butylamine solution furnished, in addition to several other compounds, the 4,4′-biquinazolinyl (12a), the quinazolinyl alcohol (13a) and the quinazolinyl ketone (13b), respectively, the mesoionic triazoloquinazolinylium thiolate (18a)and the corresponding olate (18b) as novel type photolysis products. In contrast irradiation of the 10bH-1,3,4-thiadiazolo[3,2-c]quinazoline (11b), the ring isomer of the N-(quinazolin-3-io)thiomidate (10b) furnishes, with cleavage of either the quinazoline or the thiadiazole ring, a mixture of the thiadiazoles (21a,b), and the quinazoline derivatives (14a), (22a,b)in addition to 3,4-dimethoxybenzonitrile.Irradiation of various sulphur-containing quinazoline derivatives, including the quinazolinethiones (14a,e), the methylthioquinazoline (13f) and the diquinazolinyl disulphide (24a), leads to the formation of 4,4′-biquinazolinyls (12a) and (12b), respectively. Irradiation of the quinazoline (13c), which carries no sulphur-containing substituent, does not lead to the formation of the biquinazolinyl (12a); irradiation of a mixture of quinazoline (13e) and quinazolinethione (14a) gives rise to the formation of a mixture of biquinazolinyls (12a–c) with incorporation of the ring of the sulphur-free starting quinazoline (13e) into the products (12a) and (12b).