DIELS-ALDER ADDUCTS OF A SPIROCYCLOPENTENOTRIAZOLOAZODIENOPHILE - ASSIGNMENT OF THEIR H-1 AND C-13 NMR-SPECTRA

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