Dimethyl 2-(aryloxy)fumarates and dimethyl 2-(alkyl- or arylthio)fumarates are shown
to be efficient dipolarophiles in 1,3-dipolar cycloaddition reaction with azomethine
ylides, which are generated by the reaction of isatin with the secondary amino acids
proline or sarcosine. In these reactions, dimethyl 2-(alkyl- or arylthio)fumarates
afforded spirooxindolopyrrolizidines or -pyrrolidines in high yields with excellent
regioselectivities, while dimethyl 2-(aryloxy)fumarates produced mixtures of regioisomers.
DFT calculations at the B3LYP/6-31G(d,p) level were consistent with the observed results.
Tri- and tetracyclic compounds were obtained through regio- and stereoselective intramolecular
cycloaddition of O-vinylic salicylaldehyde with secondary amino acids.
Key words
2-(aryloxy)fumarates - 2-(alkyl- or arylthio)fumarates - azomethine ylides - spiro
compounds - pyrrolizidines - pyrrolidines - DFT calculations