Influence of Lewis acids on the Diels–Alder reaction. Part I. An improved synthesis of 7-azanorbornadiene, 3-azaquadricyclane, and azepine derivatives

Abstract

Depending on the experimental conditions the AlCl3-promoted reaction of 1-carbomethoxypyrrole and dimethyl acetylenedicarboxylate yields 2,3,7-tricarbomethoxy-7-azanorbornadiene, either in almost quantitative yield or together with dimethyl 1-carbomethoxy-2-pyrrolyl maleate and fumarate. The azanorbornadiene has been quantitatively converted to 1,4,5-tricarbomethoxyazepine via the corresponding 3-azaquadricyclane. The proton magnetic resonance spectra were analyzed with the aid of the Laocoon II program.