Synthesis of Novel [1,2,4]Triazolo[1,5-a]Pyridines via concerted reactions between 2‾-cinnamoyl-2-cyanoacetohydrazide and α-cyanocinamonitriles
journal of kerbala university,
2010, Volume 6, Issue 3, Pages 161-181
AbstractA novel one step synthesis of derivatives [1,2,4]triazolo[1,5-a]pyridines (6) from 2′-cinnamoyl-2-cyanoacetohydrazide (3) and α-cyanocinnamonitriles (2) is described. The reaction takes place by 6-exo-dig cyclization followed by an 5-exo-trig process to afford salts 6. Compound 7 were isolated from the reaction mixture as the corresponding piperidinium salts due to the high stability of the heterocyclic anion. Acidification with dilute hydrochloric acid yielded the neutral [1,2,4]triazolo[1,5-a]pyridines. Now, an alternative 7-endo trig cyclization can take place and, in addition to the [1,2,4]triazolo[1,5-a] pyridines 6, the novel heterocyclic compound of seven membered ring are obtained.
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