Palladium N-heterocyclic carbene catalyzed regioselective thiolation of 1-aryl-3-methyl-1H-pyrazol-5(4H)-ones using aryl thiols.

A palladium N -heterocyclic carbene [Pd(NHC)Cl 2 ] complex of Vitamin B 1 developed earlier in our lab was also found to be an effective catalyst for regioselective thiolation via C–H bond activation of 1-aryl-3-methyl-1 H -pyrazol-5(4 H )-ones 1a – c using aryl thiols 2a – e . The protocol was found to be simple, efficient and highly regioselective to afford the target products 3a – o in good to excellent yields. [ABSTRACT FROM AUTHOR]