New heterocyclic structures. [1,2,5]thiadiazolo[3′,4′:4,5]pyrimido-[2,1-b][1,3]thiazine and thiazolo[3,2-a][1,2,5]thiadiazolo[3,4-d]pyrimidine

Derivatives of two new molecular structures, namely, 7,8-dihydro-6H,10H-[1,2,5]thiadiazolo[3′,4′:4,5]pyrim-ido[2,1-b][1,3]thiazin-10-one and 6,7-dihydro-9H-thiazolo[3,2-a][1,2,5]thiadiazolo[3,4-d]pyrimidin-9-one, and derivatives of N-substituted sulfamic acid, namely, (8-amino-3,4-dihydro 2H,6H-pyrimido[2,1-b][1,3]thiazin-6-on-7-yl)sulfamic acid and (7-amino-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidin-5-on-6-yl)sulfamic acid, were separated out as by-products in the reduction reaction of 8-amino-3,4-dihydro-7-nitroso-2H,6H-pyrimido[2,1-6][1,3]thiazin-6-one and 7-amino-2,3-dihydro-6-nitroso-5H thiazolo[3,2-a]pyrimidin-5-one derivatives, respectively, with sodium hydrosulfite. A mechanism of reaction, which hypothesizes the action of sodium hydrosulfite in an asymmetic form, is proposed. The results of single-crystal X-ray investigation on 7,8-dihydro-6H,10H[1,2,5]thiadiazolo[3′4′:4,5]pyrim-ido[2,1-6][1,3]thiazin-10-one (R = 0.032 for 863 reflections) and (8-amino-3,4-dihydro-2H,6H-pyrimido[2,1-b]-[1,3]thiazin-6-on-7-yl)sulfamic acid, sodium salt (R = 0.028 for 3507 reflections) are reported.