Regioselective Rapid Analogue Syntheses of 1-Methyl-3,5-diarylpyrazoles via Palladium-catalysed Coupling to 3(5)-Pyrazolyl Nonaflates

Regioselective rapid analogue syntheses of 1-methyl-3,5-diarylpyrazoles were developed, based on Pd-catalysed couplings to l-methyl-3(5)-arylpyrazole nonaflates, which offered an advantage in hydrolytic stability over thecorresponding triflates. The new bifunctional reagent 1-methyl-3-bromo-pyrazol-5-yl non-aflate underwent highly chemoselective Pd-catalysed couplings to the nonaflate, followed by Suzuki couplings to the bromide, allowing sequential, regioselective introduction of the two aryl substituents.