Convenient generation of 1,3-dipolar nitrilimines and [3 + 2] cycloaddition for the synthesis of spiro compounds.

[Display omitted] In the presence of 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) as an oxidizer, the domino [3 + 2] cycloaddition reaction of aldohydrazones with 2-arylidene-1,3-indnaediones or 5-arylidene-1,3-dimethylbarbituric acids in acetonitrile at 80 °C afforded functionalized spiro[indene-2,4′-pyrazoles]-1,3-diones or 2,3,7,9-tetraazaspiro[4.5]dec-1-ene-6,8,10-triones in satisfactory yields. This reaction was believed to proceed with in situ generation of reactive 1,3-dipolar nitrilimine and its sequential 1,3-dipolar cycloaddition reaction with cyclic dipolarophiles. Thus, a new convenient synthetic method for the active dipolar nitrilimine was successfully developed. [ABSTRACT FROM AUTHOR]