Visible-Light-Induced Decarboxylative Cyclization of 2-Alkenylarylisocyanides with α-Oxocarboxylic Acids: Access to 2-Acylindoles

Abstract

An efficient and practical protocol for visible-light-induced decarboxylative cyclization of 2-alkenylarylisocyanides with α-oxocarboxylic acids has been developed, which afforded a broad range of 2-acylindoles in moderate to good yields. The reaction proceeds through a cascade of acyl radical addition/cyclization reactions under irradiation of an Ir3+ photoredox catalyst without external oxidants and features simple operation, scalability, a broad substrate scope, and good functional group tolerance.

Recent Advances on Photoinduced Cascade Strategies for the Synthesis of N‐Heterocycles

“…This work was followed by a contribution by Reiser, which reported a photoredox cascade arylation of brominated 2‐alkenyl‐aryl‐isocyanates using diazonium salts [25e] . Thereafter, Yao reported the the acylation of the same system reported by Yang, to afford a family of 2‐acylate‐indoles (Scheme 2b) [25f] Moreover, redox or energy‐transfer photocatalytic intramolecular radical cyclizations and multicomponent reactions have also been reported [26]…”

Radical Carbonylative Synthesis of Heterocycles by Visible Light Photoredox Catalysis

“…Using (NH4)2S2O8 as an oxidant, Hu, Huo and Su et al developed an eosin B-catalyzed decarboxylative cyclization of N-methacryloylbenzamides, providing a wide range of acylated isoquinolines derivatives [96]. A similar concept was applied for the formation of 2-acylindoles via a practical decarboxylative cyclization of 2-alkenylarylisocyanides with α-keto acids (Scheme 26a) [97]. Very recently, Prabhu et al developed a decarboxylative acylation of electron-deficient heteroarenes in the presence of Na2S2O8 (Scheme 26b) [98].…”

Photophysical properties and electron transfer photochemical reactivity of substituted phthalimides

“…33 Photoinduced decarboxylation is also important in the context of different photocatalytic processes. [34][35][36][37][38][39][40][41] We have become interested in photodecarboxylation reactions initiated by phthalimide chromophore [42][43][44] and applied them in cyclizations with memory of chirality 45 and diastereoselective peptide cyclizations. 46 Furthermore, the photodecarboxylation efficiency was investigated in a series of phthalimide derivatives of adamantane amino acids, where we modified the distance between the electron donor (carboxylate) and the acceptor (phthalimide).…”