Cyclization reactions of 1,3-dibromopropan-2-ol, 2,3-dibromopropan-1-ol and 1-bromomethyloxirane with 6-amino-2,3-dihydro-2-thioxo-4(1H)-pyrimidinone

The cyclization reactions, carried out in strongly- or weakly-basic media, are described. Sometimes, 7-amino-2,3-dihydro-3-hydroxymethyl-5H-thiazolo3,2-a]pyrimidin-5-one is separated out, together with 8-amino-3,4-dihydro-3-hydroxy-2H,6H-pyrimido2,1-b]1,3]thiazin-6-one, as the principal product. A mechanism of reaction, during which the cyclizating agents are changed into oxirane derivatives, is proposed. The results of single-crystal X-ray investigations on 8-amino-3,4-dihydro-3-hydroxy-7-nitroso-2H,6H-pyrimido2,1-b]1,3]thiazin-6-one (R = 0.035 for 1013 reflections), and on 7-hydroxymethyl-6,7-dihydrothiazolo3,2-a]1,2,3]triazolo4,5-d]pyrimidin-9(1H)-one (R = 0.027 for 1607 reflections) are reported.