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Brønsted Acid Cocatalysis in Copper(I)-Photocatalyzed α‑Amino C–H Bond Functionalization

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posted on 04.01.2016, 00:00 by Thomas P. Nicholls, Grace E. Constable, Johnathon C. Robertson, Michael G. Gardiner, Alex C. Bissember
We have exploited a bis­(1,10-phenanthroline)­copper­(I) visible light photocatalyst (VLP), [Cu­(dap)2]+, to effect the direct α-C–H functionalization of amines. To our knowledge, this represents the first example of the oxidation of amines that are ultimately incorporated into synthetic targets by a copper­(I) VLP. We have utilized this approach to rapidly prepare unprecedented octahydroisoquinolino­[2,1-a]­pyrrolo­[3,4-c]­quinoline frameworks and exploited this process to synthesize a novel aglycone analogue of the natural product incargranine B. Most significantly, our studies suggest that the presence of trifluoroacetic acid (TFA) is crucial in mediating the aerobic oxidative quenching of a putative photoexcited copper­(I) species involved in the catalytic cycle.