Synthesis and dehydrogenation of spinaceamine and spinacine 4-hetaryl derivatives

The reaction of histamine and histidine with various hetarylaldehydes under the conditions of the base-catalyzed Pictet-Spengler process affords 4-hetaryl-substituted derivatives of spinaceamine and spinacine. The dehydrogenation of the 4-hetaryl-substituted spinaceamine derivatives using elemental sulfur in DMF at 120–130°C led to the formation of 4-hetaryl derivatives of imidazo[4,5-c]-pyridine. Under similar conditions the 4-hetaryl-substituted spinacine derivatives suffered both the dehydrogenation and oxidative decarboxylation resulting in the products identical to the compounds obtained by the dehydrogenation of 4-hetaryl-substituted spinaceamine.