Novel pyridine-catalyzed reaction of dimethyl acetylenedicarboxylate with aldehydes and N-tosylimines:: Efficient synthesis of 2-benzoylfumarates and 1-azadienes

A novel reaction of 1,4-dipolar intermediate 3, generated from pyridine and dimethyl acetylenedicarboxylate, with aromatic aldehydes, resulted in the facile synthesis of 2-benzoylfumarates via the elimination of pyridine, whereas with N-tosylimines as dipolarophiles the reaction afforded highly substituted 1-azadienes. The reaction of pyridine and dimethyl acetylenedicarboxylate with N-substituted isatins, resulted in a novel three component condensation, affording spiropyrido[2,1-b][1,3]oxazino derivatives in high yields via 1,4-dipolar cycloaddition.