A new method for C(sp 2 )-H sulfonylmethylation with glyoxylic acid and sodium sulfinates.

We herein describe a C4 sulfonylmethylation of pyrazol-5-amines with glyoxylic acid and sodium sulfinates. The reaction only needed water as a solvent, and it featured mild reaction conditions, simple operation, and high regioselectivity. Various C4 sulfonylmethylated pyrazol-5-amines were obtained in good to excellent yields. Moreover, this sulfonylmethylation method was applicable for C(sp 2 )-H sulfonylmethylation of other substrates such as enamines, indoles, and antipyrines by adding a catalyst and changing the solvent. Biological evaluation revealed that some products had antiproliferative activity against cancer cell lines.