Synthesis of 4-functionalized pyrazoles via oxidative thio- or selenocyanation mediated by PhICl₂ and NH₄SCN/KSeCN

A series of 4-thio/seleno-cyanated pyrazoles was conveniently synthesized from 4-unsubstituted pyrazoles using NH 4 SCN/KSeCN as thio/selenocyanogen sources and PhICl 2 as the hypervalent iodine oxidant. This metal-free approach was postulated to involve the in situ generation of reactive thio/selenocyanogen chloride (Cl–SCN/SeCN) from the reaction of PhICl 2 and NH 4 SCN/KSeCN, followed by an electrophilic thio/selenocyanation of the pyrazole skeleton.