Visible light photoredox catalysis: generation and addition of N-aryltetrahydroisoquinoline-derived α-amino radicals to Michael acceptors

Synthetic applications of photoredox catalysis with visible light

In the past five years, visible-light mediated photoredox catalysis has been emerging as one of the fastest growing fields in organic chemistry because of its low cost, easy availability and environmental benignness. This review intends to summarize recent research progress in novel methodology development and application in organic synthesis, and is organized in terms of key reactive intermediates.

A visible-light-mediated oxidative C-N bond formation/aromatization cascade: photocatalytic preparation of N-arylindoles

Indoles: A joint effort of light and air We have developed a mild aerobic oxidation protocol using visible light photocatalysis to synthesize structurally diverse N -arylindoles. The procedure employs 4 mol% [Ru(bpz)3](PF6)2, 18W LED light, and is performed open to the atmosphere. Readily prepared o -stryryl anilines are converted to a variety of indoles via a cascade sequence composed of oxidation of anilines, C-N bond formation, and aromatization. A 1,2-carbon shift can be also incorporated into this cascade event to further extend the substrate scope of the method. bpz = 2, 2′-Bipyrazine

A Photo Touch on Amines: New Synthetic Adventures of Nitrogen Radical Cations

Amines have been used as sacrificial electron donors to reduce photoexcited Ru(II) or Ir(III) complexes, during which they are oxidized to nitrogen radical cations. Recently, the synthetic potential of these nitrogen radical cations have caught synthetic organic chemists' attention. They have been exploited in various transformations yielding a number of elegant methods for amine synthesis. This article highlights recent developments on nitrogen radical cation chemistry under visible-light photocatalysis.

Reactivity insight into reductive coupling and aldol cyclization of chalcones by visible light photocatalysis

The reductive coupling and cyclization of chalcones to generate cyclopentanol derivatives in up to 84% yield by visible light photoredox catalysis is described. This reaction involves radical anion homocoupling, monoprotonation, and intramolecular cyclization cascade.

Visible-light-mediated addition of α-aminoalkyl radicals generated from α-silylamines to α,β-unsaturated carbonyl compounds

Visible-light-mediated addition of α-aminoalkyl radicals generated from α-silylamines to α,β-unsaturated carbonyl compounds using a photoredox catalyst is developed. We also succeeded in the isolation of a silyl enol ether as a primary product of the photochemical reaction.

Application of microflow conditions to visible light photoredox catalysis

Applications of microflow conditions for visible light photoredox catalysis have successfully been developed. Operationally simple microreactor and FEP (fluorinated ethylene propylene copolymer) tube reactor systems enable significant improvement of several photoredox reactions using different photocatalysts such as [Ru(bpy)(3)](2+) and Eosin Y. Apart from rate acceleration, this approach facilitates previously challenging transformations of nonstabilized intermediates. Additionally, the productivity of the synergistic, catalytic enantioselective photoredox α-alkylation of aldehydes was demonstrated to be increased by 2 orders of magnitude.