Diels-Alder adducts of a spirocyclopentenotriazoloazodienophile. Assignment of their 1H and 13C NMR spectra

Article abstract of DOI:10.1002/jhet.5570330329

1-Phenyl-cyclopenteno[1,2-d]-1,2,3-triazolo-5-spiro-4′- [perhydropyrazolino-3′,5′-dione] (5) afforded in situ, by oxidation with lead tetraacetate, the corresponding cyclopentenotriazolo-spiropyrazolodione 6, which was trapped with dienes giving the hetero-Diels-Alder adducts 10-12 in good yields. The DielsAlder reactions were examined on the basis of AM1 MO calculations. Total assignment of the ¹H- and ¹³C-nmr chemical shifts as well as the relative configuration of these adducts was accomplished with the help of 2D (¹H-¹H COSY, ¹H-¹H NOESY, ¹H-¹³C XHCORR, ¹H-¹³C COLOC) and NOE difference spectroscopy. The structures of compounds 11a and 11b were also examined by molecular modeling.