One-pot three-component synthesis of pyrazoles through a tandem coupling-cyclocondensation sequence

An efficient and general one-pot procedure for the synthesis of pyrazoles from chlorides, terminal alkynes and hydrazines was described via a coupling and cyclocondensation sequence. Acid chlorides coupled with terminal alkynes to give α,β-unsaturated ynones, and in situ converted into pyrazoles by the cycloaddition of hydrazine. The desired pyrazoles were obtained with 15-85% isolated yields.