Modular Access to 2-(Trifluoromethyl)pyrazolo[1,5-]pyridines and Their Benzo Analogues through a Copper(I)-Catalyzed Radical Annulation.

A mechanistically distinctive copper-catalyzed radical annulation to valuable 2-(trifluoromethyl)pyrazolo[1,5-]pyridines and their benzo analogues has been described for the first time. Notably, the newly developed complementary process allows the synthesis of 4- or 6-substituted target molecular entities as a single product, which was previously challenging to access by existing methods. The utility of this process is further demonstrated by the facile construction of four different ring systems, a gram-scale synthesis, and the late-stage functionalization of bioactive molecules.