Reactions of ethyl azepine-1-carboxylate with heterodienophiles

Abstract

4-Phenyl-1,2,4-triazoline-3,5-dione and 2,3-phthalazine-1,4-dione react with ethyl azepine-1-carboxylate (EAC) to give [_π4_s+_π2_s] cycloadducts. Diethyl azodiformate reacts with EAC to give a [4 + 2]π cycloadduct also, contrary to the original report. No evidence has been found for a transient [6 + 2]π cycloaddition product. Structural assignments have been confirmed by ¹³C n.m.r.