3-Alkylsulfanyl-2-arylazo-3-(pyrrolidin-1-yl)-acrylonitriles as masked 1,3-dipoles

Reaction of 3-alkylsulfanyl-2-arylazo-3-(pyrrolidin-1-yl)acrylonitriles with maleimides, dimethyl maleate and dimethylacetylene dicarboxylate were carried out to give octahydro-pyrrolo[3,4-a]pyrrolizin-4-ylidenes, hexahydro-pyrrolizines and 6,7-dihydro-5H-pyrrolizines. The formation of the synthesized compounds is explained by a 1,3-dipolar cycloaddition of an in situ generated azomethine ylide. The mechanisms of the formation of these active intermediates were discussed with the aid of density functional theory methods with the B3LYP functional 6-31G+ calculations using the STQN method and chemical experiments.