Visible-Light-Mediated Regioselective Chlorosulfonylation of Alkenes and Alkynes: Introducing the Cu(II) Complex [Cu(dap)Cl₂] to Photochemical ATRA Reactions

Abstract

A visible-light-mediated photocatalyzed protocol utilizing copper−phenanthroline-based catalysts has been developed that can convert a large number of olefins into their chlorosulfonylated products. Besides the Cu(I) complex [Cu(dap) 2 ]Cl, now well-established in photo-ATRA processes, the corresponding Cu(II) complex [Cu(dap)Cl 2 ] proved to be often even more efficient in the title reaction, being advantageous from an economic point of view but also opening up new avenues for photoredox catalysis. Moreover, the copper complexes outperformed commonly used ruthenium, iridium, or organic dye based photocatalysts, owing to their ability to stabilize or interact with transient radicals by inner sphere mechanisms. The use of stoichiometric Na 2 CO 3 in combination with the copper photocatalysts was found to be essential to convert unactivated olefins to the desired products, in contrast to activated olefins for which no additive was required. As suggested by appropriate control experiments, the role of Na 2 CO 3 is attributed to prevention of poisoning of the catalyst.

Making Copper Photocatalysis Even More Robust and Economic: Photoredox Catalysis with [CuII(dmp)2Cl]Cl

“…Remarkably, both spectra converged and, henceforth, show a high similarity regarding the absorption pattern, being characteristic for the Cu I species. These results indicate that both catalysts go through the same catalytic cycle, most likely having a Cu I complex as the photocatalytically active species, which then can undergo photoinduced SET to the substrate, following our previous reported mechanistic proposal for [Cu II (dap)Cl 2 ] and [Cu I (dap) 2 ]Cl . Control UV/Vis experiment with catalyst combined with product molecule ruled out potential interaction influencing the spectra (see SI).…”

“…Compound 3m: Following general procedure ( GP‐B ) using irradiation with blue LED (λ max = 455 nm) for 48 h yielded 11.5 mg (35 µmol, 7 %) of 3m as colorless oil after flash column purification (hexanes/EtOAc, 9:1 to 4:1). R f (hexanes/EtOAc, 4:1) = 0.41, Staining: UV, KMnO 4 ; 1 H‐NMR (400 MHz, CDCl 3 ): δ = 7.81 (d, J = 8.3 Hz, 2H), 7.34 (d, J = 7.6 Hz, 2H), 7.31–7.25 (m, 2H), 7.08–6.92 (m, 1H), 6.85 (dd, J = 8.8, 1.1 Hz, 2H), 4.60 (ddd, J = 11.3, 6.6, 5.5 Hz, 1H), 4.25 (dd, J = 10.3, 4.8 Hz, 1H), 4.19 (dd, J = 10.3, 5.4 Hz, 1H), 3.88 (dd, J = 14.8, 6.0 Hz, 1H), 3.58 (dd, J = 14.8, 6.7 Hz, 1H), 2.43 (s, 3H); 13 C‐NMR (101 MHz, CDCl 3 ): δ = 157.8, 145.5, 136.4, 130.2, 129.7, 128.3, 121.9, 114.9, 70.2, 60.1, 51.3, 21.8.…”

“…Compound 3n: Following general procedure ( GP‐B ) using irradiation with blue LED (λ max = 455 nm) for 48 h yielded 22.9 mg (76 µmol, 15 %) of 3n as colorless oil after flash column purification (hexanes/EtOAc, 9:1 to 4:1). R f (hexanes/EtOAc, 4:1) = 0.68, Staining: UV, KMnO 4 ; 1 H‐NMR (400 MHz, CDCl 3 ): δ = 7.80 (d, J = 8.3 Hz, 2H), 7.37 (d, J = 8.0 Hz, 2H), 4.30 (dtd, J = 8.9, 6.3, 3.8 Hz, 1H), 3.56 (dd, J = 14.6, 6.2 Hz, 1H), 3.45 (dd, J = 14.6, 6.5 Hz, 1H), 2.46 (s, 3H), 1.97 (dddd, J = 14.1, 9.9, 5.8, 3.9 Hz, 1H), 1.81–1.69 (m, 1H), 1.54–1.36 (m, 2H), 1.34–1.22 (m, 6H), 0.92–0.84 (m, 3H).…”

“…. Spectral data are in accordance to literature.Compound 3m: [12] Following general procedure (GP-B) using irradiation with blue LED (λ max = 455 nm) for 48 h yielded 11.5 mg (35 μmol, 7 %) of 3m as colorless oil after flash column purification (hexanes/EtOAc, 9:1 to 4:1). R f (hexanes/EtOAc, 4:1) = 0.41, Staining: UV, KMnO 4 ; 1 H-NMR (400 MHz, CDCl 3 ): δ = 7.81 (d, J = 8.3 Hz, 2H), 7.34 (d, J = 7.6 Hz, 2H), 7.31-7.25 (m, 2H), 7.08-6.92 (m, 1H), 6.85 (dd, .…”

“…R f (hexanes/EtOAc, 4:1) = 0.41, Staining: UV, KMnO 4 ; 1 H-NMR (400 MHz, CDCl 3 ): δ = 7.81 (d, J = 8.3 Hz, 2H), 7.34 (d, J = 7.6 Hz, 2H), 7.31-7.25 (m, 2H), 7.08-6.92 (m, 1H), 6.85 (dd, . Spectral data are in accordance to literature.Compound 3n: [12] Following general procedure (GP-B) using irradiation with blue LED (λ max = 455 nm) for 48 h yielded 22.9 mg (76 μmol, 15 %) of 3n as colorless oil after flash column purification (hexanes/EtOAc, 9:1 to 4:1). R f (hexanes/EtOAc, 4:1) = 0.68, Staining: UV, KMnO 4 ; 1 H-NMR (400 MHz, CDCl 3 ): δ = 7.80 (d, J = 8.3 Hz, 2H), 7.37 (d, J = 8.0 Hz, 2H), 4.30 (dtd, J = 8.9, 6.3, 3.8 Hz, 1H), 3.56 (dd, .2.…”