Syntheses of pyrimidine and purine analogs derived from 1,2,6‐thiadiazine 1,1‐dioxide

5‐Amino‐3‐oxo‐2 H , 4 H ‐1,2,6‐thiadiazine 1,1‐dioxide and the monopotassium salt of 3,5‐dioxo‐2 H , 4 H ,6 H ‐1,2,6‐thiadiazine 1,1‐dioxide was obtained by condensation of sulfamide and ethyl cyanacetate and diethyl malonate, respectively. 7‐Oxo‐1 H ,4 H ,6 H ‐imidazo[2,3‐ c ]‐1,2,6‐thia‐diazine 5,5‐dioxide was prepared by a multi‐step reaction sequence from 5‐amino‐3‐oxo‐2 H , 4 H ‐1,2,6‐thiadiazine 1,1‐dioxide.