Regioselective Synthesis of Mono- and Dispiropyrazoline Derivatives via 1,3-dipolar Cycloaddition with Nitrilimines

The 1,3-dipolar cycloaddition reaction of (E,E)-1,3-bis(arylidene)indan-2-one with diarylnitrilimines, generated in situ via dehydrohalogenation of the corresponding hydrazonoyl chlorides , affords predominantly monospiropyrazolines and as a mixture of diastereoisomers. Also dispiropyrazolines are formed in moderate yields. The structure and stereochemistry of cycloadducts were confirmed by 1H and 13C-NMR spectroscopy, elemental analyses data, and single-crystal X-ray diffraction studies of and .