Metal‐Free Site‐Selective Direct Oxidative Phosphorylation of Pyrazolones

A substrate-controlled site-selective phosphorylation of pyrazolin-5-ones has been established under metal-free direct oxidative coupling processes. A reaction between pyrazolones and secondary phosphonates in the presence of TBAI/TBHP combination could result in the N-P bond formation at N2 position. Meanwhile, the C-P bond coupling at C3 position could be obtained from a reaction of N2-substituted pyrazolone substrates with secondary phosphine oxides using Selectfluor. These chemo- and regioselective metal-free approaches proceed in fair to high yields under mild reaction conditions with good functional group compatibility.