Copper-Catalyzed Hydroamination: Enantioselective Addition of Pyrazoles to Cyclopropenes.

Chiral N -cyclopropyl pyrazoles and structurally related heterocycles are prepared using an earth-abundant copper catalyst under mild reaction conditions with high regio-, diastereo-, and enantiocontrol. The observed N 2 :N 1 regioselectivity favors the more hindered nitrogen of the pyrazole. Experimental and DFT studies support a unique mechanism that features a five-centered aminocupration.