Tandem synthesis of highly functionalized N-phosphorylated sulfonamido-pyrazolone derivatives

The reaction between ketenimine intermediates, generated from terminal alkynes and sulfonyl azides, diisopropyl azodicarboxylate, and trimethyl or triphenyl phosphite, in N,N-dimethylformamide at room temperature, affords highly functionalized N-phosphorylated sulfonamido-pyrazolone derivatives in moderate to good yields.