Rapid Synthesis of Luotonin A Derivatives via Synergistic Visible-Light Photoredox and Acid Catalysis.

The merging of visible-light photoredox and acid catalysis allowed for an intramolecular Povarov cycloaddition reaction using eosin Y as the photocatalyst and TsOH·H2O as the co-catalyst. A visible-light-promoted dehydrogenative cyclization protocol enabled the construction of Luotonin A derivatives with up to 97% yield.

Photocatalytic Radical Ortho-Dearomative Cyclization: Access to Spiro[4.5]deca-1,7,9-trien-6-ones.

A highly efficient ortho-dearomative cyclization reaction between alkynes and 2-bromo-2-(2-methoxybenzyl)malonate via visible light-induced photoredox catalysis has been reported. In the presence of 1 mol % fac-Ir(ppy)3, a variety of spiro[4.5]deca-1,7,9-trien-6-ones were obtained in moderate to excellent yields under mild conditions. Under the optimized reaction conditions, a sample reaction of 3 mmol scale proceeded smoothly to give the desired products in 84% yield with a low catalyst loading of 0.1 mol %.

Visible-Light-Induced Intermolecular Dearomative Cyclization of Furans: Synthesis of 1-Oxaspiro[4.4]nona-3,6-dien-2-one.

A fac-Ir(ppy)3-catalyzed intermolecular dearomative cyclization of 2-bromo-2-((5-bromofuran-2-yl)methyl)malonate and alkynes affording substituted spirolactones in yields of 19-91% via a 5- exo-dig radical cyclization under visible light is presented. This method provides a new access to the synthesis of spirocycle skeletons applying water as an external oxygen source under mild reaction conditions.

Visible-Light-Induced Radical Cascade Cyclization: Synthesis of the ABCD Ring Cores of Camptothecins.

A new strategy for constructing indolizino[1,2-b]quinolin-9(11H)-ones (ring cores of camptothecins) from readily available isocyanoarenes and N-(alkyl-2-yn-1-yl)pyridin-2(1H)-ones has been developed through a visible-light-induced radical cascade cyclization process. The reaction proceeds under mild conditions with fair to excellent yields. The easy introduction of substituents for both reactants and the broad functional group tolerance of the reaction make it a straightforward route to the cores of the marketed camptothecins and their derivatives.

Visible Light-Induced Radical Rearrangement to Construct C-C Bonds via an Intramolecular Aryl Migration/Desulfonylation Process.

A highly efficient intramolecular selective aryl migration/desulfonylation of 2-bromo-N-aryl-N-(arenesulfonyl)amide via visible light-induced photoredox catalysis has been accomplished. This approach allows for the construction of a variety of multisubstituted N,2-diarylacetamide under mild reaction conditions.

Visible-Light-Induced Photocatalytic Aerobic Oxidation/Povarov Cyclization Reaction: Synthesis of Substituted Quinoline-Fused Lactones.

A one-step construction of quinoline-fused lactones was achieved by visible-light-induced photocatalytic aerobic oxidation/Povarov cyclization reaction. This method provides a new access to the synthesis of important fused heterocycles under mild reaction conditions.

Visible-Light-Driven Dearomatization Reaction toward the Formation of Spiro[4.5]deca-1,6,9-trien-8-ones.

A visible-light-driven regioselective dearomative cyclization between 2-benzyl-2-bromomalonate and alkynes under mild conditions leading to the formation of spiro[4,5]decanes has been developed. In the presence of H2O, a variety of 2-benzyl-2-bromomalonates smoothly undergo 5-exo-dig radical dearomative cyclization with alkynes to afford the corresponding spiro[4,5]decanes in moderate to good yield in a step-economical manner under oxidant-free conditions.

Sodium Sulfite-Involved Photocatalytic Radical Cascade Cyclization of 2-Isocyanoaryl Thioethers: Access to 2-CF2/CF3-Containing Benzothiazoles.

A visible-light-induced radical cascade cyclization of 2-isocyanoaryl thioethers for the synthesis of 2-CF2/CF3-containing benzothiazoles has been developed. Sodium sulfite can participate in the photocatalytic cycle as a reductant that efficiently transforms Ir4+ into Ir3+ to promote the fluoroalkylation under mild reaction conditions.

Visible-light-induced radical cascade cyclization of oxime esters and aryl isonitriles: synthesis of cyclopenta[b]quinoxalines.

A visible-light-induced radical cascade cyclization of aryl isonitriles and cyclobutanone oxime esters for the synthesis of cyclopenta[b]quinoxalines has been accomplished for the first time. The key to the success of this process was the integration of the in situ-formed nitrile radical followed by the cascade radical isonitrile/nitrile insertion-cyclization. The easy introduction of substituents for both substrates and the high functional group tolerance of the reaction make it an efficient strategy to give various quinoxaline derivatives in moderate to good yields.

Combining Visible-Light-Photoredox and Lewis Acid Catalysis for the Synthesis of Indolizino[1,2-b]quinolin-9(11H)-ones and Irinotecan Precursor.

One-step construction of substituted indolizino[1,2-b]quinolin-9(11H)-ones was achieved by combining visible-light-photoredox and Lewis acid catalysis for an intramolecular Povarov cycloaddition reaction under mild conditions. In this catalytic process, the visible-light-promoted dehydrogenation protocol of tetrahydroquinolines constitutes the key procedure. Moreover, this method can be applied to the formal synthesis of the precursor of irinotecan, which exhibited good anticancer activities.

Visible-Light-Induced Intermolecular Dearomative Cyclization of 2-Bromo-1,3-dicarbonyl Compounds and Alkynes: Synthesis of Spiro[4.5]deca-1,6,9-trien-8-ones.

A visible-light-induced photocatalytic intermolecular dearomative cyclization of 2-bromo-1,3-dicarbonyl compounds and alkynes afforded biologically important spirocarbocycle structures in moderate to good yields via a 5-exo-dig radical cyclization under mild reaction conditions. A 5.0 mmol scale dearomatization reaction proceeded smoothly with 95% yield even when the catalyst loading was reduced to 0.1 mol %, suggesting that this method was suitable for large-scale synthesis.

Synthesis of 3-CF2-Containing Chromones via a Visible-Light-Induced Radical Cascade Reaction of o-Hydroxyaryl Enaminones.

A general and efficient visible-light-induced CF2 radical-based cascade reaction of o-hydroxyaryl enaminones has been described. This protocol afforded the corresponding functionalized 3-CF2-containing chromones in generally good yields under mild reaction conditions. The use of NaHSO3, which has both basicity and reducibility, efficiently suppressed the formation of two byproducts, 4H-chromen-4-one and 3-bromo-4H-chromen-4-one.

Visible light-induced intramolecular dearomative cyclization of α-bromo-N-benzyl-alkylamides: efficient construction of 2-azaspiro[4.5]decanes.

An efficient intramolecular dearomative cyclization via visible light-induced photoredox catalysis allows for a highly regioselective dearomative cyclization of α-bromo-N-benzyl-alkylamides to construct 2-azaspiro[4.5]decanes in the presence of an iridium catalyst.

Visible light induced radical cyclization of o-iodophenylacrylamides: a concise synthesis of indolin-2-one.

A [Ir(ppy)2(dtb-bpy)]PF6-catalyzed intramolecular radical cyclization of o-iodophenylacrylamides affording indolin-2-ones in moderate to excellent yields via 5-exo-trig radical cyclization under visible light is presented. This method provides new access to the synthesis of indolin-2-ones under mild reaction conditions.

Visible light-induced intermolecular radical addition: facile access to γ-ketoesters from alkyl-bromocarboxylates and enamines.

A highly efficient addition of alkyl α-bromocarboxylates to enamines by visible light-induced photoredox catalysis is reported. Compared with traditional methods, the reaction described here provided an alternative route for the construction of valuable γ-ketoesters in generally good yields.