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Visible‐light photocatalysis has advanced as a versatile tool in organic synthesis. However, attaining precise stereocontrol in photocatalytic reactions has been a longstanding challenge due to undesired photochemical background reactions and the involvement of highly reactive radicals or radical ion intermediates generated under photocatalytic conditions. To address this problem and expand the synthetic utility of photocatalytic reactions, a number of innovative strategies, including mono‐ and dual‐catalytic approaches, have recently emerged. Of these, exploiting chiral organocatalysis, such as enamine catalysis, iminium‐ion catalysis, Brønsted acid/base catalysis, and N‐heterocyclic carbene catalysis, to induce chirality transfer of photocatalytic reactions has been widely explored. This Review aims to provide a current, comprehensive overview of asymmetric photocatalytic reactions enabled by chiral organocatalysts published through June 2021. The substrate scope, advantages, limitations, and proposed reaction mechanisms of each reaction are discussed. This review should serve as a reference for the development of visible‐light‐induced asymmetric photocatalysis and promote the improvement of the chemical reactivity and stereoselectivity of these reactions. [ABSTRACT FROM AUTHOR]

The synergistic combination of three catalytic processes – photoredox, enamine and hydrogen atom transfer (HAT) catalysis – enabled the β‐isomerization of 2‐decalones towards the thermodynamically most stable trans‐isomers. A library of iridium (III) complexes and organic dyes were screened in combination with cyclic amines and thiols which after optimization gave the desired trans‐2‐decalones with high trans/cis ratios of 60 : 40 up to 98 : 2. [ABSTRACT FROM AUTHOR]

Photomediated Giese reactions are at the forefront of radical chemistry, much like the classical tin‐mediated Giese reactions were nearly forty years ago. With the global recognition of organometallic photocatalysts for the mild and tunable generation of carbon‐centered radicals, chemists have developed a torrent of strategies to form previously inaccessible radical intermediates that are capable of engaging in intermolecular conjugate addition reactions. This Review summarizes advances in photoredox‐mediated Giese reactions since 2013, with a focus on the breadth of methods that provide access to crucial carbon‐centered radical intermediates that can engage in radical conjugate addition processes. [ABSTRACT FROM AUTHOR]

Photomediated Giese reactions are at the forefront of radical chemistry, much like the classical tin‐mediated Giese reactions were nearly forty years ago. With the global recognition of organometallic photocatalysts for the mild and tunable generation of carbon‐centered radicals, chemists have developed a torrent of strategies to form previously inaccessible radical intermediates that are capable of engaging in intermolecular conjugate addition reactions. This Review summarizes advances in photoredox‐mediated Giese reactions since 2013, with a focus on the breadth of methods that provide access to crucial carbon‐centered radical intermediates that can engage in radical conjugate addition processes. [ABSTRACT FROM AUTHOR]

Intermediary radical cations, generated through single‐electron oxidation of enol silyl ethers by excited Ir‐based photocatalysts, can be exploited as Brønsted acids for the activation of heteroarylcyanides. This strategy enables the direct allylic C−H heteroarylation of enol silyl ethers under visible‐light irradiation. [ABSTRACT FROM AUTHOR]

Herein, we report a general iminium ion‐based catalytic method for the enantioselective conjugate addition of carbon‐centered radicals to aliphatic and aromatic enals. The process uses an organic photoredox catalyst, which absorbs blue light to generate radicals from stable precursors, in combination with a chiral amine catalyst, which secures a consistently high level of stereoselectivity. The generality of this catalytic platform is demonstrated by the stereoselective interception of a wide variety of radicals, including non‐stabilized primary ones which are generally difficult to engage in asymmetric processes. The system also served to develop organocatalytic cascade reactions that combine an iminium‐ion‐based radical trap with an enamine‐mediated step, affording stereochemically dense chiral products in one‐step. [ABSTRACT FROM AUTHOR]

Herein, we report a general iminium ion‐based catalytic method for the enantioselective conjugate addition of carbon‐centered radicals to aliphatic and aromatic enals. The process uses an organic photoredox catalyst, which absorbs blue light to generate radicals from stable precursors, in combination with a chiral amine catalyst, which secures a consistently high level of stereoselectivity. The generality of this catalytic platform is demonstrated by the stereoselective interception of a wide variety of radicals, including non‐stabilized primary ones which are generally difficult to engage in asymmetric processes. The system also served to develop organocatalytic cascade reactions that combine an iminium‐ion‐based radical trap with an enamine‐mediated step, affording stereochemically dense chiral products in one‐step. [ABSTRACT FROM AUTHOR]

Organic photocatalysts are emerging as viable and more sustainable tools than metal complexes. Recently, the field of organo‐photocatalysis has experienced an explosion in terms of applications, redesign of well‐established systems, and identification of novel scaffolds. A rational approach to the structural modification of the different photocatalysts is key to accessing unprecedented reactivity, while improving their catalytic performances. We herein discuss the concepts underpinning the scaffold modification of some of the most recently used photocatalysts and analyze how specific structural changes alter their physicochemical and redox properties. [ABSTRACT FROM AUTHOR]

Organic photocatalysts are emerging as viable and more sustainable tools than metal complexes. Recently, the field of organo‐photocatalysis has experienced an explosion in terms of applications, redesign of well‐established systems, and identification of novel scaffolds. A rational approach to the structural modification of the different photocatalysts is key to accessing unprecedented reactivity, while improving their catalytic performances. We herein discuss the concepts underpinning the scaffold modification of some of the most recently used photocatalysts and analyze how specific structural changes alter their physicochemical and redox properties. [ABSTRACT FROM AUTHOR]

Photoredox catalysis (PRC) and synthetic organic electrochemistry (SOE) are often considered competing technologies in organic synthesis. Their fusion has been largely overlooked. We review state‐of‐the‐art synthetic organic photoelectrochemistry, grouping examples into three categories: 1) electrochemically mediated photoredox catalysis (e‐PRC), 2) decoupled photoelectrochemistry (dPEC), and 3) interfacial photoelectrochemistry (iPEC). Such synergies prove beneficial not only for synthetic "greenness" and chemical selectivity, but also in the accumulation of energy for accessing super‐oxidizing or ‐reducing single electron transfer (SET) agents. Opportunities and challenges in this emerging and exciting field are discussed. [ABSTRACT FROM AUTHOR]

Cooperativity has become a mainstay in the context of multicatalytic reaction design. The combination of two or more catalysts that possess mechanistically distinct activation principles within a single chemical setting can enable bond constructions that would be impossible for any of the catalysts alone. An emerging subdomain within the field of multicatalysis is characterized by single‐electron transfer processes that are sustained by the synergistic merger of sulfur or selenium organocatalysis with photoredox catalysis. From a synthetic viewpoint, such processes have tremendous value, as they can offer new and economic pathways for the concise assembly of complex molecular architectures. Thus, the aim of this Review is to highlight recent methodological progress made in this area and to contextualize representative transformations with the mechanistic underpinnings that enable these reactions. [ABSTRACT FROM AUTHOR]

This review aims to report recent advances on decarboxylative reactions of amino acids catalyzed by transition metals or non‐metals and the growing opportunities they present in the construction of complex chemical scaffolds for applications encompassing natural product synthesis, synthetic methodology development, and functional materials. Different decarboxylative reactions have been highlighted such as radical, photoredox and metal and metal‐free coupling reactions. etc. The review is divided into two main sections: one deals with reactions via radical pathways and the other via azomethine ylide pathways. The reactions have been discussed in more detail with particular emphasis on their useful applications and mechanistic illustrations. Abbreviations: 1,3‐DCB: 1,3‐dicyanobenzene; 1,4‐DCB: 1,4‐dicyanobenzene; Acr: acridinium; BI: benziodoxolone; Boc: tert‐butoxycarbonyl; CB: conduction band; CBX: cyanobenziodoxolone; CFL: compact fluorescent lamp; DBU: 1,8‐diazabicyclo[5.4.0]undec‐7‐ene; DCA: 9,10‐dicyanoanthracene; DCB: 1,2‐dichlorobenzene; DCE: 1,2‐dichloroethane; DDDS: bis(4‐chlorophenyl) disulfide; DIPEA: diisopropylethylamine; DMA: N,N‐dimethylacetamide; DMF: N,N‐dimethylformamide; DMSO: dimethyl sulfoxide; DNA: deoxyribonucleic acid; dtbbpy: 4,4′‐di‐tert‐butyl‐2,2'‐bipyridine; DTBP: di‐tert‐butyl peroxide; equiv.: equivalent; ET: electron transfer; h: hour; HE: Hantzsch ester; LED: light‐emitting diode; min: minutes; mL: millilitre; MS: molecular sieves; MW: microwave; nm: nanometer; NS: nanosphere; Nu: nucleophile; ODCB: o‐dichlorobenzene; PA‐1: (±)‐1,1′‐binaphthyl‐2,2′‐diyl hydrogen phosphate; PC: photocatalyst; PET: photoinduced electron transfer; PEG: polyethylene glycol; PG: protecting group; Phen: phenanthrene; PTA: phosphotungstic acid 44‐hydrate; RNA: ribonucleic acid; r.t.: room temperature; SET: single‐electron transfer; TBAI: tetrabutylammonium iodide; TBHP: tert‐butyl hydroperoxide; TFA: trifluoroacetic acid; THF: tetrahydrofuran; TMEDA: N,N,N′,N′‐tetramethylethylenediamine; TS: transition state; UV: ultraviolet; VB: valence band; W: watt. [ABSTRACT FROM AUTHOR]

The anti‐Markovnikov hydroazidation of alkenes has been accomplished under visible‐light irradiation by using [Ir(dF(CF3)ppy)2(dtbbpy)]PF6 as the photocatalyst and trimethylsilyl azide as the azidating agent. The reactions were greatly facilitated by water, the beneficial effect of which can be attributed to its participation in the reaction as the hydrogen donor, as indicated by deuterium isotope experiments. The reactions proceed under solvent free conditions in the presence of water. 4‐Dimethylaminopyridine also exhibited a beneficial effect on the reactions. The present method enabled hydroazidation of several types of unactivated alkenes with good yields and high regioselectivity. Water lends a helping hand: The anti‐Markovnikov hydroazidation of alkenes has been accomplished under visible‐light irradiation by using [Ir(dF(CF3)ppy)2(dtbbpy)]PF6 as the photocatalyst and trimethylsilyl azide as the azidating agent. The reactions were significantly facilitated by water, the beneficial effect of which can be attributed to its participation in the reaction as the hydrogen donor. [ABSTRACT FROM AUTHOR]

A novel visible-light-induced intramolecular chloroetherfication of electron-enriched styrenes is described. This approach provides a mild, alternative access to the synthesis of chlorinated tetrahydrofurans and tetrahydropyrans with high regio- and stereoselectivity. [ABSTRACT FROM AUTHOR]

Halofunctionalization of alkenes is a classical method for olefin difunctionalization. It gives rise to adducts which are found in many natural products and biologically active molecules, and offers a synthetic handle for further manipulation. Classically, this reaction is performed with an electrophilic halogen source and leads to regioselective formation of the halofunctionalized adducts. Herein, we demonstrate a reversal of the native regioselectivity for alkene halofunctionalization through the use of an acridinium photooxidant in conjunction with a copper cocatalyst. [ABSTRACT FROM AUTHOR]

Photooxidation of alkanes by dioxygen occurred under visible light irradiation of 2,3-dichloro-5,6-dicyano- p-benzoquinone (DDQ) which acts as a super photooxidant. Solvent-free hydroxylation of cyclohexane and alkanes is initiated by electron transfer from alkanes to the singlet and triplet excited states of DDQ to afford the corresponding radical cations and DDQ⋅−, as revealed by femtosecond laser-induced transient absorption measurements. Alkane radical cations readily deprotonate to produce alkyl radicals, which react with dioxygen to afford alkylperoxyl radicals. Alkylperoxyl radicals abstract hydrogen atoms from alkanes to yield alkyl hydroperoxides, accompanied by regeneration of alkyl radicals to constitute the radical chain reactions, so called autoxidation. The radical chain is terminated in the bimolecular reactions of alkylperoxyl radicals to yield the corresponding alcohols and ketones. DDQ⋅−, produced by the photoinduced electron transfer from alkanes to the excited state of DDQ, disproportionates with protons to yield DDQH2. [ABSTRACT FROM AUTHOR]

A visible light-induced photocatalytic intramolecular cyclization of styryl azides has been developed in the presence of the ruthenium complex Ru(bpy)3Cl2 (0.5 mol%) as photocatalyst at room temperature. The present photocatalytic strategy features operational simplicity as well as high functional group tolerance, and provides a facile access to various 2-substituted N-free indoles in good to excellent yields. Importantly, the present process can employ sunlight as the light source to afford the corresponding products without loss of reaction efficiency. [ABSTRACT FROM AUTHOR]

Light up my ring: The title reaction is catalyzed by an acridinium/phenylmalononitrile photoredox system. A variety of readily available olefins and unsaturated alcohols can be employed to furnish tetrahydrofuran adducts with complete regiocontrol and up to four contiguous stereogenic centers. [ABSTRACT FROM AUTHOR]