Pd-catalyzed cross-coupling reactions of halogenated 1-phenylpyrazol-3-ols and related triflates

1-Phenyl-1H-pyrazol-3-ol was used as a versatile synthon for the preparation of various 1-phenyl-1H-pyrazole derivatives substituted at C-3 and C-4 of the pyrazole nucleus and at the phenyl ring para-position. Treatment of 1-phenyl-1H-pyrazol-3-ol with triflic anhydride in the presence of base gave 3-trifloyloxy pyrazole, while bromination and iodination yielded the corresponding halogenated derivatives. The obtained scaffolds were used in carbon-carbon bond forming Pd-catalyzed cross-coupling reactions to yield (het)aryl- and carbo-functionally substituted 1-phenyl-1H-pyrazoles. (C) 2009 Elsevier Ltd. All rights reserved.