A practical and sustainable two-component Minisci alkylation via photo-induced EDA-complex activation

Abstract

An operationally simple, open-air, and efficient light-mediated Minisci C–H alkylation method is described, based on the formation of an electron donor–acceptor (EDA) complex between nitrogen-containing heterocycles and redox-active esters.

Desulfinative Alkylation of Heteroarenes via an Electrostatic Electron Donor–Acceptor Complex

“…26−28 Rarer are situations where, after complexation, radical fragmentation of the donor and recombination occurs. 25,26,29,30 Alkyl sulfinate salts are an additional precursor known to produce alkyl radicals. 31−38 Interestingly, for the few photocatalytic or EDA-mediated sulfinate-based additions, the resulting radical remains S-centered and results in Saddition of the sulfinate.…”

“…Electron donor–acceptor (EDA)-mediated Minisci reactions, on the other hand, provide alkylated heteroarenes under visible light in the absence of a terminal oxidant or photocatalyst. − These protocols represent an efficient method for radical generation by enabling synergistic ionic interactions between an electron-rich donor and an electron-deficient acceptor (Figure a) resulting in SET, radical fragmentation of acceptor, and radical recombination. − Rarer are situations where, after complexation, radical fragmentation of the donor and recombination occurs. ,,, …”

Phototriggered Self-Catalyzed Three-Component Minisci Reaction: A Route to β-C(sp3) Heteroarylated Alcohols/Ethers

“…The alkene 2a ( E p/2 = +1.81 V) is then oxidized by SO 4 •– ( E p/2 = +2.5 – 3.0 V) to deliver a highly electrophilic radical cation II , which could react with H 2 O or alcohols to generate radical intermediate III by elimination of a proton. The radical intermediate III would be sufficiently nucleophilic to undergo a radical recombination with the electrophilic aromatic radical cation I , followed by deprotonation to afford the target product 3 or 5 (Path A). In addition, the so-formed radical species III could undergo addition on the protonated heteroarene 1-H + in a Minisci-type pathway to afford the amine radical cation IV , which was oxidized by SO4 •– to give the desired product 3-H + or 5-H + (Path B).…”

Visible light-promoted, photocatalyst-free decarboxylative alkylation of 2H-indazoles via electron donor–acceptor complex activation

“…The EDA complex strategy has attracted considerable attention in recent years owing to the concomitant circumvention of the requirement of a photocatalyst and stoichiometric oxidant. [24][25][26][27][28][29][30][31][32][33][34][35] The electron-rich donor and the electron-deficient acceptor form a molecular aggregate through non-covalent interaction, which generates valuable radicals through visible light-mediated single electron transfer (SET). In 2019, the elegant works of Shang, Fu, and co-workers revealed that triphenylphosphine (PPh 3 ) and sodium iodide (NaI) systems could be used for photocatalytic alkylation.…”