Synthesis and conformational analysis of some spiropyrazoline isomers

Article abstract of DOI:10.1016/S0040-4020(01)80329-X

A series of spiropyrazolines has been synthesized by 1,3-dipolar cycloaddition of E- and Z-3-arylidene-chromanones, -1-thiochromanones, -flavanones, -1-thioflavanones as well as 2-benzylidene-1-indanone, -1-benzosuberone with diazomethane. It has been found that this cycloaddition is regio- and stereoselective affording trans- and cis- spiro-1-pyrazolines. Spiro-1-pyrazolines were converted into spiro-2-pyrazolines on acid-catalysed isomerization. Conformation and relative configuration of compounds prepared has been elucidated by various one- and two-dimensional n.m.r. methods.