Arene Binuclear Ru(II)-Promoted Sustainable Synthesis of Substituted Pyrazoles from Alcohols via Acceptorless Dehydrogenative Annulation

We report a selective and sustainable synthesis of substitutedpyrazoles via an eco-friendly acceptorless dehydrogenative annulation(ADA) of greener alcohols, malononitrile, and various aromatic hydrazidesby newly synthesized binuclear Ru-(II) p-cymene complexes.A discrete set of binuclear Ru-(II) complexes are fabricated and structurallycharacterized by analytical, spectral, and single-crystal X-ray diffractionmethods. Further, the catalytic effectiveness of the complexes isexplored for the construction of 5-amino-4-cyano-N-aroylpyrazoles (34 examples) under mild conditions and producesH(2)O/H-2 as the only byproduct. A sequence ofpolysubstituted pyrazoles has been constructed in 62-95% yieldusing 1 mol % catalyst loading. Probable intermediates detected inthe catalytic reaction have been isolated and confirmed by nuclearmagnetic resonance and electrospray ionization mass spectrometry studies.Expediently, a therapeutically significant gout medicine allopurinolanalogue has been derived successfully from the synthesized 5-amino-4-cyano-N-aroylpyrazoles.

Automated summary

A sustainable synthesis of substituted pyrazoles is achieved via an eco-friendly dehydrogenative annulation reaction using newly synthesized binuclear Ru-(II) p-cymene complexes. The reaction proceeds under mild conditions, producing H(2)O/H-2 as the only byproduct, and yields a range of polysubstituted pyrazoles and a therapeutic gout medicine analogue successfully.