Isomerization of Substituted Tricyclic 4,5-Dihydropyrazoles

Article abstract of DOI:10.1007/BF00807038

The acid and base catalyzed isomerization of some tricyclic 2-pyrazolines with N-Carbamoyl-, N-thiocarbamoyl- and N-phenyl substituents was investigated. Starting from cis or trans 3-H, 3a-H diastereomers, equilibrium mixtures of cis and trans diastereomers were prepared which were separated and subsequently studied by ¹H NMR and ¹³C NMR spectroscopy. A mechanism for the isomerization of the pyrazolines is suggested, supported by a deuterium exchange at C-3a.