Azide Ring-Opening-Ring-Closure Reactions and Tele-substitutions in Vicinal Azidopyrazole-, Pyrrole- and Indolecarboxaldehydes

Article abstract of DOI:10.1021/jo00033a039

5-Chloro-1-methylpyrazole-4-carboxaldehydes 1 react with excess sodium azide in dimethyl sulfoxide to produce a mixture of 1-azidomethyl-4-cyanopyrazoles 2 and 4-cyano-5-hydroxy-1-methylpyrazoles 3.Application of this reaction to the corresponding 5-chloro-1-phenylpyrazole-4-carboxaldehydes 5 gave 4-cyano-5-hydroxy-1-phenyl-pyrazoles 7 as the sole products in high yields.Likewise, 2-aryl-5-chloro-1-methylpyrrole-3,4-dicarboxaldehydes 9 rearranged to 2-aryl-4-cyano-5-hydroxy-1-methylpyrrole-3-carboxaldehydes 10 in high yields.In the indole series, treatment of 1-aryl-2-chloroindole-3-carboxaldehydes 11 with NaN3 yielded a mixture of 1-aryl-3-cyano-2(3H)-indolones 13 and 1-aryl-5-azido-3-cyanoindoles 12, both products resulting from a ring-opening-ring-closure reaction with concomitant nucleophilic tele-substitution at the 5-position of the indole ring.