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(sp3)–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 NH4I-mediated aerobic oxidative conditions. This reaction features easily available feedstock, green and economic conditions, and valuable products.