Benzo[c]cinnoline N-oxides as 1,3-dipoles
Abstract
Benzocinnoline N-oxides give azomethine ylides with dimethyl acetylenedicarboxylate at elevated temperatures, most probably by 1,3-dipolar cycloaddition which is unprecedented for azoxy compounds, followed by electrocyclic ring opening; this mechanism is confirmed for the same reactions of the closely related N-iminobenzocinnolinium ylides.