Neutral Organic Super Electron Donors Made Catalytic

Abstract

Neutral organic super electron donors (SEDs) display impressive reducing power but, until now, it has not been possible to use them catalytically in radical chain reactions. This is because, following electron transfer, these donors form persistent radical cations that trap substrate‐derived radicals. This paper unlocks a conceptually new approach to super electron donors that overcomes this issue, leading to the first catalytic neutral organic super electron donor.

Aromaticity and sterics control whether a cationic olefin radical is resistant to disproportionation

“…Electron-rich olens are an exciting class of organic redox systems with potentially three stable redox states [1][2][3] and are popular reductants in organic synthesis. [4][5][6][7][8][9] Exciting applications are in particular associated with the open-shell redox state with one unpaired electron, which allows for intriguing conductive and photochemical properties. The arguably most relevant derivative, tetrathiafulvalene (TTF 1, Fig.…”

“…[16][17][18][19][20] The aza-analogues of TTF, i.e. tetraaminoethylenes or enetetramines, originate from the formal dimerization of unsaturated-(NHC, 8), saturated-(saNHC, 9) or benzannulated-(benzNHC, 10) N-heterocyclic carbenes (NHCs). Other examples comprise thiazolin-2-ylidenes (11, 12, 13, Fig.…”

Aryl dechlorination and defluorination with an organic super-photoreductant

“…Many organic super electron donors fulfill that requirement, 60 but until very recently they could not be used catalytically. 61 Therefore the compound tetrakis(dimethylamino)ethylene (TDAE) struck our attention, because it is commercially avail-able. Whilst the photochemistry of TDAE has received some prior attention, [62][63][64] reductive dehalogenations were not considered and its potential as an excited-state reductant has never been assessed quantitatively.…”

Tailored Coumarin Dyes for Photoredox Catalysis: Calculation, Synthesis, and Electronic Properties

“…Murphy described powerful organic reductants able to promote radical coupling and other reactions of substrates with reduction potentials <−1.8 V (vs a saturated calomel electrode, SCE) [17] . Unfortunately, these organic reductants are rather unstable and difficult to generate, although an interesting catalytic variant was recently reported [18] . Miyake has developed and studied UV light‐absorbing N‐ aryl phenoxazines as strongly reducing metal‐free photoredox catalyst for Atom Transfer Radical Polymerization (ATRP), [19] that can access a highly reducing excited state and operate via an oxidative quenching pathway, analogous to the one previously reported for iridium‐catalyzed reactions in ATRA reactions [20] .…”