Borane Catalyzed Selective Diazo Cross‐Coupling Towards Pyrazoles

Decomposition of donor-acceptor diazo compounds leads to the formation reactive carbene intermediates. These can undergo a wide variety transfer reactions yield synthetically useful products. Herein, we report selective borane catalyzed cyclization reaction from combination two different afford N-substituted pyrazoles. The decomposition more α-aryl α-diazoester and subsequent with vinyl diazoacetate produces N-alkylated pyrazoles in regioselective manner. Catalytic amounts tris(pentafluorophenyl)borane (10 mol%) were employed pyrazole products (36 examples) yields 59 80%. Extensive DFT studies have been undertaken interpret mechanism for this which was found go through tandem catalytic cycles, both by B(C6F5)3.