Fused Heterocycles. Part 3. Synthesis and Stereochemistry of Benzopyrano- and Benzothiapyrano-Pyrazoles
Several tricyclic benzopyranopyrazole derivatives have been studied by 1H and 13C n.m.r. spectroscopy.They were prepared by treating 3-benzylidene-chromanones and -1-thiochromanones with semicarbazide or thiosemicarbazide: reactions which give only the cis-3-H,3a-H stereoisomers.