Synthesis of 7 H ‐tetrazolo[1,5‐ c ]pyrrolo[3,2‐ e ]pyrimidines and their reductive ring cleavage to 4‐aminopyrrolo[2,3‐ d ]pyrimidines

Some new 7,9‐disubstituted 7 H ‐1,2,3,4‐tetrazolo[1,5‐ c ]pyrrolo[3,2‐ e ]pyrimidines 5 have been synthesized either by diazotization of 4‐hydrazino‐5,7‐disubstituted‐7 H ‐pyrrolo[2,3‐ d ]pyrimidines 4 obtained by hydrazinolysis of 4‐chloro‐5,7‐disubstituted‐7 H ‐pyrrolo[2,3‐ d ]pyrimidines 3 or via a substitution reaction between 3 and sodium azide. 5,7‐Disubstituted‐7 H ‐pyrrolo[2,3‐ d ]pyrimidin‐4(3 H )‐ones 2 were obtained by cyclocondensation of 2‐amino‐3‐cyano‐1,4‐disubstituted pyrroles 1 with formic acid which on chlorination using phosphorus oxychloride afforded 3 . A novel route for the synthesis of 4‐amino‐5,7‐disubstituted‐7 H ‐pyrrolo[2,3‐ d ]pyrimidines 6 by the reductive ring cleavage of 5 has been reported.