Reactions of diethyl dicyanofumarate with β-keto nitriles and β-keto esters: synthesis of polyfunctional 4H-pyrans

Diethyl dicyanofumarate reacts with β-keto nitriles under catalyst-free thermal conditions via formal [3 + 3] annulation involving Michael addition followed by intramolecular cyclization to afford 6-substituted diethyl 2-amino-4,5-dicyano-4H-pyran-3,4-dicarboxylates. With β-keto esters, the initially formed 2-aminopyran would cause aminolysis in the second equivalent of β-keto ester to deliver triethyl 4-cyano-2-(1,3-dioxoalkylamino)-4H-pyran-3,4,5-tricarboxylates.