Study of the Formation and Thermal Decomposition of an Azo‐Bridged Tricyclic Ring System

Abstract 1‐Amino‐2‐methyl‐1,3‐pentadienes were treated with dimethyl 1,2,4,5‐tetrazine‐3,6‐dicarboxylate to give diazatricyclo[2.2.2.0]octenes and dimethyl 4‐methylpyridazine‐3,6‐dicarboxylate, the product distribution being largely dependent on the nature of the amino substituent. Under similar conditions the analogous 1‐morpholino‐1,3‐butadiene afforded dimethyl pyridazine‐3,6‐dicarboxylate as the major product. The tricyclic products underwent selective thermal decomposition to give dimethyl 4‐methylpyridazine‐3,6‐dicarboxylate in excellent yield. The proposed mechanism of the formation as well as of the decomposition was supported by quantum chemical calculations and experimental evidence. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)