Transformations of 3,3,4-tricyano-3,4-dihydro-2H-pyran-4-carboxamides. Synthesis of pyrano[3,4-c]pyrrole derivatives

A procedure has been developed for the synthesis of polyfunctional pyrano[3,4- c ]pyrrole derivatives via intramolecular cyclization involving vicinal cyano and carboxamide groups on a pyran ring. 3-Amino-1-oxo-1,3a,4,7a-tetrahydropyrano[3,4- c ]pyrrole-3a,7a-dicarbonitrile thus obtained react with organic amines to give stable ammonium salts and undergo hydrolysis to 1,3-dioxo-1,2,3,3a,4,7a-hexahydropyrano[3,4- c ]pyrrole-3a,7a-dicarbonitriles in the presence of sulfuric acid.