Aerobic α,β-C(sp3)–H Bond Difunctionalization and C–N Bond Cleavage of Triethylamine: Difunctional Ammonium Iodide Enabling the Regioselective Synthesis of 4-Arylpyrimido[1,2-b]indazoles

A novel method for the regioselective synthesis of 4-arylpyrimido[1,2- b ]indazoles has been developed via the dual C(sp 3 )–H bond functionalization and C–N bond cleavage of triethylamine. The elusive acyclic enamine intermediates are effectively in situ generated and captured by aromatic aldehydes to form a wide array of tricyclic products from 3-aminoindazoles under the NH 4 I-mediated aerobic oxidative conditions. This reaction features easily available feedstock, green and economic conditions, and valuable products.