Autocatalytic photoredox Chan-Lam coupling of free diaryl sulfoximines with arylboronic acids.

Affiliation

Wang C(#)(1), Zhang H(#)(1), Wells LA(#)(2), Liu T(3), Meng T(1), Liu Q(3), Walsh PJ(2), Kozlowski MC(4), Jia T(5)(6)(7).
Author information:
(1)Shenzhen Grubbs Institute and Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong, China.
(2)Roy and Diana Vagelos Laboratories, Penn/Merck Laboratory for High-Throughput Experimentation, Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA.
(3)Department of Pharmaceutical Engineering, College of Chemical Engineering, Northwest University, Xi'an, Shanxi, China.
(4)Roy and Diana Vagelos Laboratories, Penn/Merck Laboratory for High-Throughput Experimentation, Department of Chemistry, University of Pennsylvania, Philadelphia, PA, USA. [Email]
(5)Shenzhen Grubbs Institute and Department of Chemistry, Southern University of Science and Technology, Shenzhen, Guangdong, China. [Email]
(6)State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, China. [Email]
(7)Guangdong Provincial Key Laboratory of Catalysis, Shenzhen, Guangdong, China. [Email]
(#)Contributed equally

Abstract

N-Arylation of NH-sulfoximines represents an appealing approach to access N-aryl sulfoximines, but has not been successfully applied to NH-diaryl sulfoximines. Herein, a copper-catalyzed photoredox dehydrogenative Chan-Lam coupling of free diaryl sulfoximines and arylboronic acids is described. This neutral and ligand-free coupling is initiated by ambient light-induced copper-catalyzed single-electron reduction of NH-sulfoximines. This electron transfer route circumvents the sacrificial oxidant employed in traditional Chan-Lam coupling reactions, increasing the environmental friendliness of this process. Instead, dihydrogen gas forms as a byproduct of this reaction. Mechanistic investigations also reveal a unique autocatalysis process. The C-N coupling products, N-arylated sulfoximines, serve as ligands along with NH-sulfoximine to bind to the copper species, generating the photocatalyst. DFT calculations reveal that both the NH-sulfoximine substrate and the N-aryl product can ligate the copper accounting for the observed autocatalysis. Two energetically viable stepwise pathways were located wherein the copper facilitates hydrogen atom abstraction from the NH-sulfoximine and the ethanol solvent to produce dihydrogen. The protocol described herein represents an appealing alternative strategy to the classic oxidative Chan-Lam reaction, allowing greater substrate generality as well as the elimination of byproduct formation from oxidants.