Photocatalytic decarboxylative alkylations mediated by triphenylphosphine and sodium iodide

Abstract

Most photoredox catalysts in current use are precious metal complexes or synthetically elaborate organic dyes, the cost of which can impede their application for large-scale industrial processes. We found that a combination of triphenylphosphine and sodium iodide under 456-nanometer irradiation by blue light–emitting diodes can catalyze the alkylation of silyl enol ethers by decarboxylative coupling with redox-active esters in the absence of transition metals. Deaminative alkylation using Katritzky’s N-alkylpyridinium salts and trifluoromethylation using Togni’s reagent are also demonstrated. Moreover, the phosphine/iodide-based photoredox system catalyzes Minisci-type alkylation of N-heterocycles and can operate in tandem with chiral phosphoric acids to achieve high enantioselectivity in this reaction.

Catalyst‐free Decarboxylation and Decarboxylative Giese Additions of Alkyl Carboxylates through Photoactivation of Electron Donor‐Acceptor Complex

“…[9] Recent studies revealed that RAEs could be efficiently activated through formation of electron-donor-acceptor complex with an electron donor species under irradiation. [10] The electron-donor-acceptor complex can be a transient encounter complex, which is formed in equilibrium in solution through weak non-covalent interactions, [11] such as Coulombic interaction, hydrogen bonding, and π-π stacking, which are heavily affected by solvation. With our interest in development of inexpensive methodologies to use aliphatic carboxylic acids in organic synthesis, [12] we conceived that decarboxylative conjugated addition with Michael acceptors and hydrodecarboxylation could be performed with a electron donor substrate such as Hantzsch ester (HE) under mild irradiation condition using blue LEDs.…”

Aromatic Chemistry in the Excited State: Facilitating Metal‐Free Substitutions and Cross‐Couplings

“…[28] Recently,Fu, Shang, and their co-workers have discovered that in cooperation with triphenylphosphine,N aI can initiate aw ide range of radical reactions promoted by blue light. [29] Scheme 5. Photo-promoted couplings of aryl triflates with type-III nucleophiles.…”

Construction of C(sp2)−C(sp3) Bond between Quinoxalin‐2(1H)‐ones and N‐Hydroxyphthalimide Esters via Photocatalytic Decarboxylative Coupling

“…[8] In recent years, alkyl N-hydroxyphthalimide (NHP) esters was emerged as an efficient decarboxylation alkylation reagent because it could be reduced by photocatalyst,g enerating av ariety of alkyl radicals via elimination of CO 2 and phthalimide. [9] For example, the regioselectivea lkylation of N-heteroarenes with alkyl NHP esters under irradiation of blue LEDs was achieved by Shang and Fu. [10] We supposed that this process also could be applied for the synthesisof3-alkylated quinoxalin-2(1H)-ones.W ith our ongoing interesto n developing green and efficient methods for direct CÀHf unctionalization, [11] herein, we report am etal and oxidant free Minisci type reactiono fq uinoxalin-2(1 H)one with alkyl NHP esters via ap hotocatalytic system promoted by visible light, leading to the synthesis of av ariety of 3-alkylated quinoxaline-2(1H)ones in moderate to excellent yields.…”