Synthesis of 3-Aminoazaindazoles via Cu-Catalyzed Cross Coupling of Isocyanides

Nitrogen-containing heterocycles are commonly encountered in drug discovery, but the synthesis of such ring structures is not always efficient. Fused heterocyclic rings, in particular, can be challenging to synthesize. Herein, we report a highly convergent synthesis of 3-aminoazaindazoles via a Cu-catalyzed reaction between isocyanides and 3-halo-2-hydrazineylpyridines (and analogues). Reaction optimization through high-throughput experimentation (HTE) identified a novel set of exogenous ligand-free Cu conditions utilizing a cheap and readily available catalyst. The reaction displays high functional group tolerance and has the potential to be highly enabling for medicinal chemistry efforts. A putative mechanism is described as well as preliminary mechanistic experiments.