Regioselectivity of nitrilimines 1,3-dipolar cycloaddition: Novel synthesis of spiro[4,4]nona-2,8-dien-6-one derivatives

Regioselective 1,3-dipolar cycloaddition of nitrilimines (generated in situ from dehydrohalogenation of the corresponding hydrazonoyl halides by the action of triethylamine) with 4-arylidene-1-aryl-2-phenyl-1H-imidazol-5(4H)-one 3 afforded the corresponding spiro[4,4]nona-2,8-dien-6-one 4. The reaction was carried out in dry benzene under reflux temperature. Refluxing in acetic acid, 4a was converted to its respective N-phenylpyrazole-5-carboxamide 8. The structures of prepared compounds were established by elemental analyses and spectral data (IR, MS, 1H, and 13C NMR). © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:131–136, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20666