Azaindoles. Part I. The syntheses of 5-aza- and 5,7-diazaindoles by the non-catalytic thermal indolization of 4-pyridyl- and 4-pyrimidylhydrazones respectively

The thermal indolization of a series of 4-pyridyl- and 4-pyrimidylhydrazones has been investigated. Under these conditions, isobutyraldehyde and 2-methylbutyraldehyde 4-pyridylhydrazones afford only 5-aza-2,3-dimethylindole and 5-aza-2-ethyl-3-methylindole respectively, and both ethyl methyl ketone and isobutyraldehyde 4-pyrimidylhydrazones afford only 5,7-diaza-2,3-dimethylindole. Several attempts to effect a Chichibabin amination on 5-aza-2,3-dimethyl- and 5-aza-1,2,3-trimethylindole led only to the recovery of starting material.