Visible-light-induced C(sp 3 )-H thiocyanation of pyrazolin-5-ones: a practical synthesis of 4-thiocyanated 5-hydroxy-1 H -pyrazoles.

A direct, aerobic and visible light photocatalytic approach to synthesize 4-thiocyanated 5-hydroxy-1 H -pyrazoles via cross-coupling of pyrazolin-5-ones with ammonium thiocyanate is described. Under redox-neutral and metal-free conditions, a series of 4-thiocyanated 5-hydroxy-1 H -pyrazoles could be easily and efficiently obtained in good to high yields by using low-toxicity and inexpensive ammonium thiocyanate as the thiocyanate source.