Stability investigations of alkyl 2,4-bisaryl-6-methyl-1,2,3,4-tetrahydropyrimidine-5-carboxylates

The tetrahydropyrimidines (THPM) with an 4-(2-nitrophenyl) substituent 14 r eact with UV-A-light to yield the pyrimido[1,6-b]indazoles 16 and the cycli c hydroxamic acid 20 as a by-product. Irradiation of the 2,4-bis(2-nitrophe nyl) THMP 2 do not give the 2,4-bis(2-nitrosophenyl)pyrimidine 26, but a mi xture of the pyrimido[1,6-b]- and -[1,2-b]indazoles 27 and 28. The products obtained by oxidation and reduction of the THPM are reported including the synthesis of pyrido[5,4-b]quinolines.