1,3-Dipolar cycloaddition of nitrilimines to a variety of 2-arylmethylidene
-1-indanones 1 or 2-arylmethylidene-1,3-indandiones 5 gave the correspondin
g spiro[2H-indene-2,3'-[3H]pyrazol]-1(3H)-one 3 and their 1,3-dione derivat
ives 6 in high regioselectivity. The stereo-configuration of 3 (3'R, 4'S or
its enantiomeric form) was established by nOe-difference technique as well
as single crystal X-ray diffraction analysis.