Utilization of cleavage of the [1]benzofuro[2,3‐ e ][1,2,4]triazine ring for the synthesis of oxygen, nitrogen and sulfur derivatives of [1,2,4]triazine

A series of 6‐azacytosines 4a‐4k and 5a‐5c were prepared by nucleophilic cleavage of furan ring of [1]benzofuro[2,3‐ e ][1,2,4]triazine derivative 1 . Some of them were used for the preparation of derivatives of [1,2,4]triazolo[4,3‐ d ][1,2,4]triazine ( 6a‐6d ) and tetrazolo[1,5‐ d ][1,2,4]triazine (7). The reaction of 1 with hydrogen sulfide afforded the corresponding 6‐(2‐hydroxyphenyl)‐2‐phenyl‐5‐thioxo‐4,5‐dihydro‐1,2,4‐tri‐azin‐3(2 H )‐one ( 8 ), while with hydrogen selenide 6‐(2‐hydroxyphenyl)‐2‐phenyl‐4,5‐dihydro‐1,2,4‐triazin‐3(2 H )‐one ( 9 ) was formed. The prepared compounds were tested for biological activity.