Synthetic Approaches to 5:8-Fused Heterocyclic Systems. A Novel Rearrangement During the Synthesis of Imidazo[4,5-e][1,2,4]triazocine Ring System

Abstract

The attempted ring-closure of 4-amino-1-benzyl-5-[(N²-benzyl-N²-methoxy-carbonyl)hydrazinomethylenecarbonyl]imidazole (5b) in sodium hydride/dimethyl sulfoxide at 50–60 °C afforded 1,7-dibenzylxanthine (6) instead of the anticipated 5:8-fused heterocycle 4b. A tentative reaction pathway has been proposed for the observed transformation.