SYNTHESIS OF 5-AZAINDOLE DERIVATIVES VIA MESOIONIC OXAZOLIUM 5-OXIDES

A synthesis of 5‐azaindole derivatives is described. This synthetic approach involves the preparation of an appropriately substituted pyrrole derivative by a 1,3‐dipolar cycloaddition reaction of dimethyl acetylenedicarboxylate with a mesoionic oxazolium 5‐oxide. The pyrrole intermediate contains a protected β‐aminoethyl substituent, and subsequent removal of the phthalimido protecting group results in cyclization to yield the corresponding 5‐azaindole. This approach has been used for both acyclic and cyclic amino acid precursors of the 1,3‐dipole which is ultimately used in the sequence. Copyright © 1979 Journal of Heterocyclic Chemistry