Abstract
The photo-irradiation of thiobarbiturates (1) with an N-phenylalkyl group gives bicyclic fused pyrimidine derivatives (2) through a Norrish type II reaction. The crystal structures of dihydro-1,5,5-trimethyl-3-(3-phenylpropyl)-2-thioxo-4,6(1H,5H)-pyrimidinedione (1a) and the photocyclization product (2b) of dihydro-1,5,5-trimethyl-3-(3-phenylbutyl)-2-thioxo-4,6(1H,5H)-pyrimidinedione (1b) were elucidated by X-ray crystallographic analysis. The photocyclization product (2b) was determined to be 1,6,7,8-tetrahydro-1,3,3-trimethyl-9-phenyl-2H-pyrido[1,2-a]pyrimidine-2,4(3H)-dione.
