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In the presence of DIPEA (diisopropylethylamine), a formal [3+2] cycloaddition reaction between diazooxindoles and oxazol-5-(4H)-ones takes place easily to give new 3-(1H-1,2,4-triazol-1-yl)indolin-2-ones in 61-98% yield. The structure of the target molecules was confirmed by single-crystal X-ray structure analysis. [ABSTRACT FROM AUTHOR]

In the presence of Na2CO3, the [3+2] cycloaddition of azaoxyallyl cations, in situ formed from α-halohydroxamates by reaction with isothiocyanides, proceeded smoothly and furnished ( Z)-2-iminothiazolidin-4-ones in 25-99 % chemical yields. The chemical structure of the title compounds was confirmed by X-ray single-crystal structure analysis. [ABSTRACT FROM AUTHOR]

Catalyzed by 10 mol-% PhCO2H, the [3+2] cycloaddition between 3-isothiocyanato oxindoles and nitroso compounds proceeded readily to deliver 1,2,4-oxadiazolidine-3-thione-fused spirooxindoles in 40-82 % yield. The structures of the title compounds were firmly confirmed by X-ray single-crystal structure analysis. [ABSTRACT FROM AUTHOR]