Single-operation deracemization of 3H-indolines and tetrahydroquinolines enabled by phase separation

Synthesis and photodynamic activity of new 5-[(E)-2-(3-alkoxy-1-phenyl-1H-pyrazol-4-yl)ethenyl]-2-phenyl-3H-indoles

A series of new indole-pyrazole hybrids 8a-m were synthesized through the palladium-catalyzed ligandless Heck coupling reaction from easily accessible unsubstituted, methoxy- or fluoro-substituted 4-ethenyl-1H-pyrazoles and 5-bromo-3H-indoles. These compounds exerted cytotoxicity to melanoma G361 cells when irradiated with blue light (414 nm) and no cytotoxicity in the dark at concentrations up to 10 µM, prompting us to explore their photodynamic effects. The photodynamic properties of the example compound 8d were further investigated in breast cancer MCF-7 cells. Evaluation revealed comparable anticancer activities of 8d in both breast and melanoma cancer cell lines within the submicromolar range. The treatment induced a massive generation of reactive oxygen species, leading to different types of cell death depending on the compound concentration and the irradiation intensity.

The sugar cube: Network control and emergence in stereoediting reactions

Stereochemical editing strategies have recently enabled the transformation of readily accessible substrates into rare and valuable products. Typically, site selectivity is achieved by minimizing kinetic complexity by using protecting groups to suppress reactivity at undesired sites (substrate control) or by using catalysts with tailored shapes to drive reactivity at the desired site (catalyst control). We propose "network control," a contrasting paradigm that exploits hidden interactions between rate constants to greatly amplify modest intrinsic biases and enable precise multisite editing. When network control is applied to the photochemical isomerization of hexoses, six of the eight possible diastereomers can be selectively obtained. The amplification effect can be viewed as a mesoscale phenomenon between the limiting regimes of kinetic control in simple chemical systems and metabolic regulation in complex biological systems.

Molecular Ratchets and Kinetic Asymmetry: Giving Chemistry Direction

Over the last two decades ratchet mechanisms have transformed the understanding and design of stochastic molecular systems-biological, chemical and physical-in a move away from the mechanical macroscopic analogies that dominated thinking regarding molecular dynamics in the 1990s and early 2000s (e.g. pistons, springs, etc), to the more scale-relevant concepts that underpin out-of-equilibrium research in the molecular sciences today. Ratcheting has established molecular nanotechnology as a research frontier for energy transduction and metabolism, and has enabled the reverse engineering of biomolecular machinery, delivering insights into how molecules 'walk' and track-based synthesisers operate, how the acceleration of chemical reactions enables energy to be transduced by catalysts (both motor proteins and synthetic catalysts), and how dynamic systems can be driven away from equilibrium through catalysis. The recognition of molecular ratchet mechanisms in biology, and their invention in synthetic systems, is proving significant in areas as diverse as supramolecular chemistry, systems chemistry, dynamic covalent chemistry, DNA nanotechnology, polymer and materials science, molecular biology, heterogeneous catalysis, endergonic synthesis, the origin of life, and many other branches of chemical science. Put simply, ratchet mechanisms give chemistry direction. Kinetic asymmetry, the key feature of ratcheting, is the dynamic counterpart of structural asymmetry (i.e. chirality). Given the ubiquity of ratchet mechanisms in endergonic chemical processes in biology, and their significance for behaviour and function from systems to synthesis, it is surely just as fundamentally important. This Review charts the recognition, invention and development of molecular ratchets, focussing particularly on the role for which they were originally envisaged in chemistry, as design elements for molecular machinery. Different kinetically asymmetric systems are compared, and the consequences of their dynamic behaviour discussed. These archetypal examples demonstrate how chemical systems can be driven inexorably away from equilibrium, rather than relax towards it.

Chiral phosphoric acid-catalyzed transfer hydrogenation of 3,3-difluoro-3H-indoles

A convenient and efficient method for the synthesis of optically active difluoro-substituted indoline derivatives starting from the corresponding 3H-indoles by chiral phosphoric acid-catalyzed transfer hydrogenation was developed. Using Hantzsch ester as the hydrogen source under mild reaction conditions, the target products can be obtained with excellent yield and enantioselectivity.

Ratcheting synthesis

Synthetic chemistry has traditionally relied on reactions between reactants of high chemical potential and transformations that proceed energetically downhill to either a global or local minimum (thermodynamic or kinetic control). Catalysts can be used to manipulate kinetic control, lowering activation energies to influence reaction outcomes. However, such chemistry is still constrained by the shape of one-dimensional reaction coordinates. Coupling synthesis to an orthogonal energy input can allow ratcheting of chemical reaction outcomes, reminiscent of the ways that molecular machines ratchet random thermal motion to bias conformational dynamics. This fundamentally distinct approach to synthesis allows multi-dimensional potential energy surfaces to be navigated, enabling reaction outcomes that cannot be achieved under conventional kinetic or thermodynamic control. In this Review, we discuss how ratcheted synthesis is ubiquitous throughout biology and consider how chemists might harness ratchet mechanisms to accelerate catalysis, drive chemical reactions uphill and programme complex reaction sequences.

Catalytic Photochemical Deracemization via Short-Lived Intermediates

Upon irradiation in the presence of a suitable chiral catalyst, racemic compound mixtures can be converted into enantiomerically pure compounds with the same constitution. The process is called photochemical deracemization and involves the formation of short-lived intermediates. By opening different reaction channels for the forward reaction to the intermediate and for the re-constitution of the chiral molecule, the entropically disfavored process becomes feasible. Since the discovery of the first photochemical deracemization in 2018, the field has been growing rapidly. This review comprehensively covers the research performed in the area and discusses current developments. It is subdivided according to the mode of action and the respective substrate classes. The focus of this review is on the scope of the individual reactions and on a discussion of the mechanistic details underlying the presented reaction.

Recent advancements in the use of Bobbitt's salt and 4-acetamidoTEMPO

Recent advances in synthetic methodologies for selective, oxidative transformations using Bobbitt's salt (4-acetamido-2,2,6,6-tetramethyl-1-oxopiperidinium tetrafluoroborate, 1) and its stable organic nitroxide counterpart ACT (4-acetamidoTEMPO, 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxyl, 2) have led to increased applications across a broad array of disciplines. Current applications and mechanistic understanding of these metal-free, environmentally benign, and easily accessible organic oxidants now span well-beyond the seminal use of 1 and 2 in selective alcohol oxidations. New synthetic methodologies for the oxidation of alcohols, ethers, amines, thiols, C-H bonds and other functional groups with 1 and 2 along with the field's current mechanistic understandings of these processes are presented alongside our contributions in this area. Exciting new areas harnessing the unique properties of these oxidants include: applications to drug discovery and natural product total synthesis, the development of new electrocatalytic methods for depolymerization of lignin and modification of other biopolymers, in vitro and in vivo nucleoside modifications, applications in supramolecular catalysis, the synthesis of new polymers and materials, enhancements in the design of organic redox flow batteries, uses in organic fuel cells, applications and advancements in energy storage, the development of electrochemical sensors, and the production of renewable fuels.

Multiplicative enhancement of stereoenrichment by a single catalyst for deracemization of alcohols

Stereochemical enrichment of a racemic mixture by deracemization must overcome unfavorable entropic effects as well as the principle of microscopic reversibility; recently, photochemical reaction pathways unveiled by the energetic input of light have led to innovations toward this end, most often by ablation of a stereogenic C(sp3)-H bond. We report a photochemically driven deracemization protocol in which a single chiral catalyst effects two mechanistically different steps, C-C bond cleavage and C-C bond formation, to achieve multiplicative enhancement of stereoinduction, which leads to high levels of stereoselectivity. Ligand-to-metal charge transfer excitation of a titanium catalyst coordinated by a chiral phosphoric acid or bisoxazoline efficiently enriches racemic alcohols that feature adjacent and fully substituted stereogenic centers to enantiomeric ratios up to 99:1. Mechanistic investigations support a pathway of sequential radical-mediated bond scission and bond formation through a common prochiral intermediate and reveal that, although the overall stereoenrichment is high, the selectivity in each individual step is moderate.

Interconverting mirror-image molecules

A light-driven multitasking catalyst enhances chirality in molecular mixtures.

Catalytic Deracemization Reactions

Deracemization, which converts a racemate into its single enantiomer without separation of the intermediate, has gained renewed interest in asymmetric synthesis with its inherent atomic economy and high efficiency. However, this ideal process requires selective energy input and delicate reaction design to surmount the thermodynamical and kinetical constraints. With the rapid development of asymmetric catalysis, many catalytic strategies in concert with exogenous energy input have been exploited to facilitate this nonspontaneous enantioenrichment. In this perspective, we will discuss the basic ideas to accomplish catalytic deracemization, categorized by the three major exogenous energy sources including chemical (redox)-, photo- and mechanical energy from attrition. Emphasis will be given to the catalytic features and the underlying deracemization mechanism together with perspectives on future development.

Light-driven redox deracemization of indolines and tetrahydroquinolines using a photocatalyst coupled with chiral phosphoric acid

The integration of oxidation and enantioselective reduction enables a redox deracemization to directly access enantioenriched products from their corresponding racemates. However, the solution of the kinetically microscopic reversibility of substrates used in this oxidation/reduction unidirectional event is a great challenge. To address this issue, we have developed a light-driven strategy to enable an efficient redox deracemization of cyclamines. The method combines a photocatalyst and a chiral phosphoric acid in a toluene/aqueous cyclodextrin emulsion biphasic co-solvent system to drive the cascade out-of-equilibrium. Systemic optimizations achieve a feasible oxidation/reduction cascade sequence, and mechanistic investigations demonstrate a unidirectional process. This single-operation cascade route, which involves initial photocatalyzed oxidation of achiral cyclamines to cyclimines and subsequent chiral phosphoric acid-catalyzed enantioselective reduction of cyclimines to chiral cyclamines, is suitable for constructing optically pure indolines and tetrahydroquinolines.

Hydride-Abstraction-Initiated Catalytic Stereoselective Intermolecular Bond-Forming Processes

The stereoselective intermolecular bond-forming reactions through the direct manipulation of ubiquitous yet inert C(sp³)-H bonds represent an important and long-standing goal in chemistry. In particular, developing such a stereoselective bimolecular transformation involving carbocation intermediates generated via site-selective hydride abstraction or formal hydride abstraction by organic oxidants would avoid the preinstallation of directing groups and is therefore attractive. Hydride-abstraction-initiated bimolecular transformations have received considerable attention, but existing examples lack stereoselective studies. Prevalent stereoselective studies typically suffer from the narrow substrate scope of specific and highly reactive N-aryl amines and diarylmethanes together with limited synthetic utility. This Account describes our recent advances in the development and synthetic application of hydride-abstraction-initiated stereoselective intermolecular C-C and C-H bond-forming processes with significantly expanded scopes involving structurally diverse N-acyl amines and ethers together with nitriles, esters, and perfluoroalkyl moieties.We first explored hydride-abstraction-initiated stereoselective intermolecular C-C bond-forming processes. Utilizing triarylmethyl cations or oxoammonium ions as hydride abstractors, we accomplished the diastereoselective oxidative C-H functionalization of structurally diverse N-acyl amines and ethers with a range of organoboranes and C-H components, efficiently installing a series of alkyl, alkenyl, aryl, and alkynyl species into the α-position of heteroatoms with good levels of diastereocontrol. Subsequently, we developed an "acetal pool" strategy as the toolbox to regulate the stability of cationic intermediates and the compatibility of organic oxidants with a delicate asymmetric catalysis system. Utilizing this strategy, we achieved the catalytic enantioselective oxidative C-H alkenylation, arylation, alkynylation, and alkylation of diverse N-acyl heterocycles with a range of boronates and C-H components. Simultaneously, we extended this strategy to the asymmetric oxidative C-H alkylation of ethers. Notably, the method allows solvents that are used daily, such as tetrahydrofuran, tetrahydropyran, and diethyl ether, to be facilely transformed to high-value-added optically pure bioactive molecules. We further expanded the scope of this challenging area from the C(sp³)-H bond adjacent to electron-donating heteroatoms to valuable electron-withdrawing functional groups including nitriles, esters, and perfluoroalkyl moieties for the stereoselective construction of single and vicinal quaternary carbon stereocenters, respectively.We studied hydride-abstraction-initiated catalytic asymmetric intermolecular C-H bond-forming processes, known as redox deracemization. Utilizing the acetal pool strategy, we reported the first redox deracemization of cyclic benzylic ethers. Later, we disclosed an aerobic one-pot deracemization of diverse α-amino acid derivatives with excellent functional group compatibility. We further achieved the deracemization of the tertiary stereogenic center adjacent to electron-withdrawing groups including perfluoroalkyl, cyano, and ester moieties, which are otherwise difficult to construct.

Light-empowered contra-thermodynamic stereochemical editing

Creating, conserving and modifying the stereochemistry of organic compounds has been the subject of significant research efforts in synthetic chemistry. Most synthetic routes are designed according to the stereoselectivity-determining step. Stereochemical editing is an alternative strategy, wherein the chiral-defining or geometry-defining steps are independent of the construction of the major scaffold or complexity. It enables late-stage alterations of stereochemistry and can generate isomers from a single compound. However, in many instances, stereochemical editing processes are contra-thermodynamic, meaning the transformation is unfavourable. To overcome this barrier, photocatalysis uses photogenerated radical species and introduces thermochemical biases. A range of synthetically valuable contra-thermodynamic stereochemical editing processes have been invented, including deracemization of chiral molecules, positional alkene isomerization and dynamic epimerization of sugars and diols. In this Review, we highlight the fundamental mechanisms of visible-light photocatalysis and the general reactivity modes of the photogenerated radical intermediates towards contra-thermodynamic stereochemical editing processes.

Manganese-Catalyzed Asymmetric Hydrogenation of 3H-Indoles

The asymmetric hydrogenation (AH) of 3H-indoles represents an ideal approach to the synthesis of useful chiral indoline scaffolds. However, very few catalytic systems based on precious metals have been developed to realize this challenging reaction. Herein, we report a Mn-catalyzed AH of 3H-indoles with excellent yields and enantioselectivities. The kinetic resolution of racemic 3H-indoles by AH was also achieved with high s-factors to construct quaternary stereocenters. Many acid-sensitive functional groups, which cannot be tolerated when using a state-of-the-art ruthenium catalyst, were compatible with manganese catalysis. This new process expands the scope of this transformation and highlights the uniqueness of earth-abundant metal catalysis. The reaction could proceed with catalyst loadings at the parts per million (ppm) level with an exceptional turnover number of 72 350. This is the highest value yet reported for an earth-abundant metal-catalyzed AH reaction.

Redox deracemization of phosphonate-substituted dihydropyrimidines

An efficient redox deracemization of the phosphonic ester substituted 3,4-dihydropyrimidin-2-one (DHPM) derivatives is described. The one-pot deracemization strategy consisted of the oxidization to destroy the stereocenter center and the following asymmetric transfer hydrogenation to regenerate the chiral carbon center with the vicinal phosphonic ester group, providing a series of optically active phosphonate substituted DHPMs with up to 96% ee.

Visible-Light-Driven Catalytic Deracemization of Secondary Alcohols

Deracemization of racemic chiral compounds is an attractive approach in asymmetric synthesis, but its development has been hindered by energetic and kinetic challenges. Here we describe a catalytic deracemization method for secondary benzylic alcohols which are important synthetic intermediates and end products for many industries. Driven by visible light only, this method is based on sequential photochemical dehydrogenation followed by enantioselective thermal hydrogenation. The combination of a heterogeneous dehydrogenation photocatalyst and a chiral molecular hydrogenation catalyst is essential to ensure two distinct pathways for the forward and reverse reactions. These reactions convert a large number of racemic aryl alkyl alcohols into their enantiomerically enriched forms in good yields and enantioselectivities.

Novel (S)-Selective Hydrolase from Arthrobacter sp. K5 for Kinetic Resolution of Cyclic Amines

Chiral 2-methylpiperidine (2-MPI) is an important building block that has potential for applications in pharmaceuticals and pesticides. In this study, we observed that the hydrolase in Arthrobacter sp. K5 exhibits high (S)-selectivity toward rac-N-pivaloyl-2-MPI to yield (S)-2-MPI with 80.2% enantiomeric excess (ee) in a 38.2% conversion. The hydrolase, which was identified by analyses of partial amino acid sequences of the purified enzyme and genome sequence of Arthrobacter sp. K5, exhibited moderate homology with amidohydrolases up to 67% (molinate hydrolase from Gulosibacter molinativorax). The hydrolase gene was overexpressed in Rhodococcus erythropolis. The recombinant cells produced (S)-2-MPI with 83.5% ee in a 48.4% conversion (E = 26.3) from 100 mM rac-N-pivaloyl-2-MPI. These results suggest the possibility of an efficient preparation of chiral 2-MPI in kinetic resolution.

Late-Stage Heteroarylation of Hetero(aryl)sulfonium Salts Activated by α-Amino Alkyl Radicals

We report a late‐stage heteroarylation of aryl sulfonium salts through activation with α‐amino alkyl radicals in a mechanistically distinct approach from previously reported halogen‐atom transfer (XAT). The new mode of activation of aryl sulfonium salts proceeds in the absence of light and photoredox catalysts, engaging a wide range of hetarenes. Furthermore, we demonstrate the applicability of this methodology in synthetically useful cross‐coupling transformations.

Kinetic resolution of indolines by asymmetric hydroxylamine formation

Catalytic kinetic resolution of amines represents a longstanding challenge in chemical synthesis. Here, we described a kinetic resolution of secondary amines through oxygenation to produce enantiopure hydroxylamines involving N–O bond formation. The economic and practical titanium-catalyzed asymmetric oxygenation with environmentally benign hydrogen peroxide as oxidant is applicable to a range of racemic indolines with multiple stereocenters and diverse substituent patterns in high efficiency with efficient chemoselectivity and enantio-discrimination. Late-stage asymmetric oxygenation of bioactive molecules that are otherwise difficult to synthesize was also explored.

Catalytic kinetic resolution of amines is a longstanding challenge in chemical synthesis. Here, the authors report on titanium‐catalysed asymmetric oxygenation with hydrogen peroxide for kinetic resolution of secondary amines through oxygenation to produce enantiopure hydroxylamines involving N–O bond formation.

Asymmetric Catalysis Mediated by Synthetic Peptides, Version 2.0: Expansion of Scope and Mechanisms

Low molecular weight synthetic peptides have been demonstrated to be effective catalysts for an increasingly wide array of asymmetric transformations. In many cases, these peptide-based catalysts have enabled novel multifunctional substrate activation modes and unprecedented selectivity manifolds. These features, along with their ease of preparation, modular and tunable structures, and often biomimetic attributes make peptides well-suited as chiral catalysts and of broad interest. Many examples of peptide-catalyzed asymmetric reactions have appeared in the literature since the last survey of this broad field in Chemical Reviews (Chem. Rev. 2007, 107, 5759-5812). The overarching goal of this new Review is to provide a comprehensive account of the numerous advances in the field. As a corollary to this goal, we survey the many different types of catalytic reactions, ranging from acylation to C-C bond formation, in which peptides have been successfully employed. In so doing, we devote significant discussion to the structural and mechanistic aspects of these reactions that are perhaps specific to peptide-based catalysts and their interactions with substrates and/or reagents.

Redox deracemization of β,γ-alkynyl α-amino esters

The first non-enzymatic redox deracemization method using molecular oxygen as the terminal oxidant has been described. The one-pot deracemization of β,γ-alkynyl α-amino esters consisted of a copper-catalyzed aerobic oxidation and chiral phosphoric acid-catalyzed asymmetric transfer hydrogenation with excellent functional group compatibility. By using benzothiazoline as the reducing reagent, an exclusive chemoselectivity at the C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> N bond over the C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C bond was achieved, allowing for efficient deracemization of a series of α-amino esters bearing diverse α-alkynyl substituent patterns. The origins of chemo- and enantio-selectivities were elucidated by experimental and computational mechanistic investigation. The generality of the strategy is further demonstrated by efficient deracemization of β,γ-alkenyl α-amino esters.

A one-pot deracemization of β,γ-alkynyl α-amino esters consisting of an aerobic oxidation and chiral phosphoric acid-catalyzed asymmetric transfer hydrogenation has been described.

Lightdriven deracemization enabled by excitedstate electron transfer

Deracemization is an attractive strategy for asymmetric synthesis, but intrinsic energetic challenges have limited its development. Here, we report a deracemization method in which amine derivatives undergo spontaneous optical enrichment upon exposure to visible light in the presence of three distinct molecular catalysts. Initiated by an excited-state iridium chromophore, this reaction proceeds through a sequence of favorable electron, proton, and hydrogen-atom transfer steps that serve to break and reform a stereogenic C-H bond. The enantioselectivity in these reactions is jointly determined by two independent stereoselective steps that occur in sequence within the catalytic cycle, giving rise to a composite selectivity that is higher than that of either step individually. These reactions represent a distinct approach to creating out-of-equilibrium product distributions between substrate enantiomers using excited-state redox events.

Deracemization Enabled by Visible-Light Photocatalysis

Deracemization is an ideal but challenging strategy for the conversion of a racemic mixture into a single enantiomer. Recent studies have demonstrated that visible-light photocatalysis could be utilized to promote selective deracemization of axially chiral allenes as well as cyclopropylquinolones and cyclic ureas with central chirality either through energy transfer or through a sequence of electron, proton, and hydrogen-atom transfer.

Enantioselective Kinetic Resolution/Desymmetrization of Para-Quinols: A Case Study in Boronic-Acid-Directed Phosphoric Acid Catalysis

A chiral phosphoric acid-catalyzed kinetic resolution and desymmetrization of para-quinols operating via oxa-Michael addition was developed and subsequently subjected to mechanistic study. Good to excellent s-factors/enantioselectivities were obtained over a broad range of substrates. Kinetic studies were performed, and DFT studies favor a hydrogen bonding activation mode. The mechanistic studies provide insights to previously reported chiral anion phase transfer reactions involving chiral phosphate catalysts in combination with boronic acids.

Redox deracemization of diarylmethyl alkynes

A highly effective one-pot redox deracemization of diarylmethyl alkynes has been disclosed.

Photocatalytic deracemization fixes the mix

Photocatalysis converts racemic mixtures of N -aryl cyclic ureas into single enantiomers

Progress in the Chemistry of Tetrahydroquinolines

Tetrahydroquinoline is one of the most important simple nitrogen heterocycles, being widespread in nature and present in a broad variety of pharmacologically active compounds. This Review summarizes the progress achieved in the chemistry of tetrahydroquinolines, with emphasis on their synthesis, during the period from mid-2010 to early 2018.

Iron-Catalyzed Aerobic Dehydrogenative Kinetic Resolution of Cyclic Secondary Amines

A nonenzymatic iron-catalyzed dehydrogenative kinetic resolution of cyclic secondary amines using air as an oxidant has been reported. The economical and practical method is applicable to a series of cyclic benzylic amines, including 5,6-dihydrophenanthridines and 1,2-dihydroquinolines, with diverse functional groups at the α position in high yields with excellent enantioselectivities. The direct dehydrogenative kinetic resolution of advanced intermediates of bioactive molecules that are difficult to access using existing catalytic asymmetric synthetic strategy was also demonstrated.

A Redox Strategy for Light-Driven, Out-of-Equilibrium Isomerizations and Application to Catalytic C-C Bond Cleavage Reactions

We report a general protocol for the light-driven isomerization of cyclic aliphatic alcohols to linear carbonyl compounds. These reactions proceed via proton-coupled electron-transfer activation of alcohol O-H bonds followed by subsequent C-C β-scission of the resulting alkoxy radical intermediates. In many cases, these redox-neutral isomerizations proceed in opposition to a significant energetic gradient, yielding products that are less thermodynamically stable than the starting materials. A mechanism is presented to rationalize this out-of-equilibrium behavior that may serve as a model for the design of other contrathermodynamic transformations driven by excited-state redox events.

Chemoenzymatic Deracemization of Chiral Sulfoxides

The highly enantioselective enzyme methionine sulfoxide reductase A was combined with an oxaziridine-type oxidant in a biphasic setup for the deracemization of chiral sulfoxides. Remarkably, high ee values were observed with a wide range of substrates, thus providing a practical route for the synthesis of enantiomerically pure sulfoxides.

Enantioselective synthesis of amines by combining photoredox and enzymatic catalysis in a cyclic reaction network

Visible light-driven reduction of imines to enantioenriched amines in aqueous solution is demonstrated for the first time. Excitation of a new water-soluble variant of the widely used [Ir(ppy)3] (ppy = 2-phenylpyridine) photosensitizer in the presence of a cyclic imine affords a highly reactive α-amino alkyl radical that is intercepted by hydrogen atom transfer (HAT) from ascorbate or thiol donors to afford the corresponding amine. The enzyme monoamine oxidase (MAO-N-9) selectively catalyzes the oxidation of one of the enantiomers to the corresponding imine. Upon combining the photoredox and biocatalytic processes under continuous photo-irradiation, enantioenriched amines are obtained in excellent yields. To the best of our knowledge, this is the first demonstration of a concurrent photoredox- and enzymatic catalysis leading to a light-driven asymmetric synthesis of amines.