Asymmetric counteranion-directed photoredox catalysis

Abstract

Photoredox catalysis enables unique and broadly applicable chemical reactions but controlling their selectivity has proven to be difficult. The pursuit of enantioselectivity is a particularly daunting challenge, arguably due to the high energy of the activated radical (ion) intermediates, and previous approaches have invariably required pairing of the photoredox catalytic cycle with an additional activation mode for asymmetric induction. A potential solution for photoredox reactions proceeding via radical ions would be catalytic pairing with enantiopure counterions. However, while attempts toward this approach have been described, high selectivity has not yet been accomplished. Here we report a potentially general solution to radical cation-based asymmetric photoredox catalysis. We describe organic salts, featuring confined IDPi counteranions that catalyze highly enantioselective [2+2]-cross cycloadditions of styrenes.

Counteranion-Directed Catalysis for Asymmetric Radical Cation Transformations

“…近日, 德国马克斯普朗克煤炭研究所 List 教授团队 将手性抗衡阴离子催化不对称催化反应的"不对称抗衡 阴离子导向催化(ACDC)"策略应用于光氧化还原催化, 以单一催化循环实现了高对映选择性的不对称光氧化 还原催化. 如 Scheme 2A 所示, 在光以及含有空间受阻 [7] , 高对映选择性地合成了一 系列环丁烷产物. 该反应具有广泛的底物普适性.…”

Solar overall water-splitting by a spin-hybrid all-organic semiconductor

“…Besides the two-band excitation to make the full use of the visible-to-NIR solar spectrum, breaking through the HER bottleneck with even a much lower S 1 state level on the D-Q hybrid than that either on :PDI 2− or PDI 2− monomer chromophore is another important issue. A radical-mediated electron transfer (ET) pathway is reported to hold much lower reaction overpotentials, allowing reactions that are impossible under the non-radical pathway to occur 33,34 . In our system, the interfacial ET of HER occurs on the ordered :PDI 2− /PDI 2− surface with plenty of diradical unpaired electrons, which makes the H + →H 2 reduction easier along the favorable diradical-mediated pathway.…”

Ag3PO4 Nanoparticles Enable the Generation of Long-lived Radical Cations for Visible Light-Driven [2+2] and [4+2] Pericyclic Reactions

“…51 This is likely why the 1a→2a cycloaddition stopped nearly instantly upon light-off in homogeneous systems. 21,52 To probe the lifetime of 1a •+ in neat HFIP, we used a 266-nm laser pulse to excite a 1a/HFIP solution. However, the system produced signals from unknown species and the absorption peaks of 1a •+ at ca.…”

“…In this case, the electrostatic interaction between 1a •+ and (Ag 3 PO 4 ) n− NP surfaces is analogous to the interactions in homogeneous solutions described by Yoon et al for 1a •+ with a tetraarylborate anion, 17 Ishihara et al for 1a •+ with FeCl 4 − , 18-20 and List et al for 1a •+ with an imidodiphosphorimidate counteranion. 21 The adsorbed 1a •+ is stabilized by electrostatic interaction with the (Ag 3 PO 4 ) n− surfaces. The low possibility recombination between 1a •+ and e CB − shared by multiple Ag + cations, (Ag δ+ ) m − , is evidenced by the observation of AgNP formation.…”

“…[5][6][7][8][9][10][11][12][13][14][15] However, the PCs utilised for generating radical cations are primarily homogeneous organic compounds, particularly transition metal-coordination complexes [8][9][10][11] and πconjugated molecules. [12][13][14][15] Meanwhile, the scope of the approaches is constrained by the short lifetime of radical cations (on a μs scale [16][17][18][19][20][21][22] ). In contrast, inorganic semiconductor PCs (isPCs), such as TiO 2 , CdS, Bi 2 MoO 6 , and Ag 3 PO 4 , have been widely employed for solar light harvesting applications including water splitting, organic pollutant degradation, and photoelectric conversion.…”