Proposal of an Amide-Directed Carbocupration Mechanism for Copper-Catalyzed meta-Selective C-H Arylation of Acetanilides by Diaryliodonium Salts
- Received Date: 2011-07-26
- C-H bond activation, Carbocupration, Copper catalysis, Density functional theory, Selectivity
Abstract: We examined the puzzling mechanism for Cu-catalyzed meta-C-H arylation reaction of anilides by diaryliodonium salts through systematic theoretical analysis. The previously proposed anti-oxy-cupration mechanism featuring anti-1,2- or anti-1,4-addition of cuprate and oxygen to the phenyl ring generating a meta-cuprated intermediate was excluded due to the large activation barriers. Alternatively, a new amide-directed carbocupration mechanism was proposed which involves a critical rate- and regio-determining step of amide-directed addition of the Cu(III)-aryl bond across the phenyl C2=C3 double bond to form an ortho-cuprated, meta-arylated intermediate. This mechanism is kinetically the most favored among several possible mechanisms such as ortho- or para-cupration/migration mechanism, direct meta C-H bond cleavage mediated by Cu(III) or Cu(I), and Cu(III)-catalyzed ortho-directed C-H bond activation mechanism. Furthermore, the predicted regioselectivity based on this mechanism has been shown to favor the meta-arylation that is consistent with the experimental observations.
|Citation:||Song-lin Zhang, Yu-qiang Ding. Proposal of an Amide-Directed Carbocupration Mechanism for Copper-Catalyzed meta-Selective C-H Arylation of Acetanilides by Diaryliodonium Salts[J]. Chinese Journal of Chemical Physics , 2011, 24(6): 711-723. doi: 10.1088/1674-0068/24/06/711-723|