Spiropyrazolines have been synthesized by 1,3-dipolar cycloaddition of an 2-arylidene-1-tetralone, 3-arylidene-chromanones, -1-thiochromanones, and -flavanones with diazomethane. The relative configuration and stereochemistry of the products have been determined by means of one-dimensional difference N.O.E. measurements. It is shown that ring-closure reaction is regioselective, yielding stereohomogeneous
The thermaldecomposition of spiro-1-pyrazolines 2 obtained by the cycloaddition of exocyclic α,β-unsaturated ketones with diazomethane gives spirocyclopropanes 4 with high selectivity and the new β-methyl-3-benzylidene derivatives 3. The configuration and conformation of the thermolysis products 3 and 4 were elucidated by different n.m.r. methods.