A New Family of Nucleophiles for Photoinduced, Copper-Catalyzed Cross-Couplings via Single-Electron Transfer: Reactions of Thiols with Aryl Halides Under Mild Conditions (O °C)

Abstract

Building on the known photophysical properties of well-defined copper-carbazolide complexes, we have recently described photoinduced, copper-catalyzed N-arylations and N-alkylations of carbazoles. Until now, there have been no examples of the use of other families of heteroatom nucleophiles in such photoinduced processes. Herein, we report a versatile photoinduced, copper-catalyzed method for coupling aryl thiols with aryl halides, wherein a single set of reaction conditions, using inexpensive CuI as a precatalyst without the need for an added ligand, is effective for a wide range of coupling partners. As far as we are aware, copper-catalyzed C-S cross-couplings at 0 °C have not previously been achieved, which renders our observation of efficient reaction of an unactivated aryl iodide at -40 °C especially striking. Mechanistic investigations are consistent with these photoinduced C-S cross-couplings following a SET/radical pathway for C-X bond cleavage (via a Cu(I)-thiolate), which contrasts with nonphotoinduced, copper-catalyzed processes wherein a concerted mechanism is believed to occur.

Thermal and Photoinduced Copper-Promoted C–Se Bond Formation: Synthesis of 2-Alkyl-1,2-benzisoselenazol-3(2H)-ones and Evaluation against Mycobacterium tuberculosis

“…45 Therefore, we explored this possibility with KSeCN and aryl halides ( 4a – c ) to form ebselen ( 1a ). Table 3 shows our results using aryl bromide ( 4b ) which affords 1a in 89% using thermal conditions (entry 1).…”

“…40–43 The cross-coupling reactions reported to-date for C–Se bond formation require temperatures of greater than 100 °C. 36,43,44 However, we took note of the work of Fu and Peters who reported photoinduced Cu-catalyzed cross-couplings to form C–S 45 and C–N 46,47 bonds at temperatures as low as 0 °C in seminal work which expanded the scope of Ullmann-type chemistry to thermally sensitive compounds.…”

Effective Laboratory-Scale Preparation of Axitinib by Two CuI-Catalyzed Coupling Reactions

“…In particular, CuI has been extensively researched for use in the reaction because of its low price, low toxicity and stability to air. [31][32][33][34][35][36] Because there are many successful examples of Cu-catalyzed C-S coupling reactions, CuI has been applied firstly to replace palladium as the C-S coupling reaction catalyst in this work.…”

Diaryl and Heteroaryl Sulfides: Synthesis via Sulfenyl Chlorides and Evaluation as Selective Anti-Breast-Cancer Agents

“…For example, the Fu and Peters laboratories disclosed a copper-catalyzed, photoinduced synthesis of diaryl sulfides that proceeds at 0 °C. 10 …”