Tandem synthesis of highly functionalized pyrazole derivatives from terminal alkynes, sulfonyl azides, diethyl azadicarboxylate, and sodium arylsulfinates.

The reaction between ketenimine intermediates [generated from terminal alkynes and sulfonyl azides], diethyl azadicarboxylate, and sodium arylsulfinates in N, N-dimethylformamide at room temperature, affords ethyl 2,3-dihydro-3-oxo-4-phenyl-2-tosyl-5-(tosylamino)pyrazole-1-carboxylates in moderate-to-good yields. When diisopropyl azadicarboxylate was used as the ester component, diisopropyl 1-arylsulfonyl-2-{[aryl(alkyl)sulfonyl]-2-phenylethanimidoyl}-1,2-hydrazinedicarboxylates were obtained.