Substituent-oriented C-N bond formation via N-H insertion or Wolff rearrangement of 5-aryl-1H-pyrazoles and diazo compounds.

A facile and efficient synthetic strategy for the chemoselective synthesis of N-substituted 3-aryl-1H-pyrazole derivatives has been developed, and it was oriented by different 2-diazo compounds. Both N-H insertion and Wolff-rearrangement products can be obtained selectively by the opportune choice of diazo compounds. N-Cyclohexenone 3-aryl-1H-pyrazoles were formed using cyclic 2-diazo-1,3-diketones via N-H insertion in the presence of a copper catalyst, and α-carbonyl 3-aryl-1H-pyrazoles could be synthesized through a Wolff-rearrangement process without any catalyst under thermal conditions. Moreover, both reactions could be carried out in moderate to excellent yields (58-93%) and showed good functional group tolerance.