Mechanistic Studies on the Synthesis of Pyrrolidines and Piperidines via Copper-Catalyzed Intramolecular C-H Amination.

We have recently developed a method for the synthesis of pyrrolidines and piperidines via intramolecular C-H amination of N -fluoride amides using [Tp x CuL] complexes as precatalysts [Tp x = tris(pyrazolyl)borate ligand and L = THF or CH 3 CN]. Herein, we report mechanistic studies on this transformation, which includes the isolation and structural characterization of a fluorinated copper(II) complex, [(Tp iPr2 OH)CuF] [Tp iPr = hydrotris(3,5-diisopropylpyrazolyl)borate], pertinent to the mechanistic pathway. The effects of the nature of the Tp x ligand in the copper catalyst as well as of the halide in the N-X amides employed as reactants have been investigated both from experimental and computational perspectives.