Correction: A photoexcited halogen-bonded EDA complex of the thiophenolate anion with iodobenzene for C(sp3)–H activation and thiolation
TL;DR: In this paper, a direct photochemical thiolation of C(sp3)-H bond-containing etheric, allylic, and benzylic substrates with thiophenol was developed.
Abstract: Thiophenol was discovered to form an EDA complex with iodobenzene through halogen bonding interactions upon treatment with KOH. A direct photochemical thiolation of C(sp3)–H bond-containing etheric, allylic, and benzylic substrates with thiophenol was developed. The reaction proceeded on the basis of the in situ generation of a thiyl radical and aryl radical through single electron transfer between the photoexcited thiophenolate anion and aryl iodide EDA complex. Then a C(sp3) centred-radical was formed by aryl radical-mediated hydrogen atom transfer and the thiolation products were delivered via a radical–radical cross-coupling with the thiyl radical.
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TL;DR: In this paper , photoactivation of electron donor-acceptor (EDA) complexes between arylsulfonium salts and 1,4-diazabicyclo[2.2] octane with visible light or natural sunlight was discovered.
Abstract: General photoactivation of electron donor–acceptor (EDA) complexes between arylsulfonium salts and 1,4-diazabicyclo[2.2.2]octane with visible light or natural sunlight was discovered. This practical and efficient mode enables the production of aryl radicals under mild conditions, providing an unrealized opportunity for two-step para-selective C–H functionalization of complex arenes. The novel mode for generating aryl radicals via an EDA complex was well supported by UV-vis absorbance measurements, nuclear magnetic resonance titration experiments, and density functional theory (DFT) calculations. The method was applied to the regio- and stereo-selective arylation of various N-heterocycles under mild conditions, yielding an assembly of challengingly linked heteroaryl–(hetero)aryl products. Remarkably, the meaningful couplings of bioactive molecules with structurally complex drugs or agricultural pharmaceuticals were achieved to display favorable in vitro antitumor activities, which will be of great value in academia or industry.
36 citations
TL;DR: In this article , a mild light-driven protocol for direct alkylation of phenols is reported, driven by the photochemical activity of a halogen-bonded complex formed upon complexation of the in situ generated electron-rich phenolate anion with the α-iodosulfone.
16 citations
TL;DR: In this article , an electronically tuned thiophosphoric acid, 7,7'-OMe-TPA, was assembled with substrate or co-catalyst N-heteroaromatics through hydrogen bonding and π-π interactions to form electron donor-acceptor (EDA) complexes.
Abstract: We developed organocatalyst systems to promote the cleavage of stable C-H bonds, such as formyl, α-hydroxy, and benzylic C-H bonds, through a hydrogen atom transfer (HAT) process without the use of exogenous photosensitizers. An electronically tuned thiophosphoric acid, 7,7'-OMe-TPA, was assembled with substrate or co-catalyst N-heteroaromatics through hydrogen bonding and π-π interactions to form electron donor-acceptor (EDA) complexes. Photoirradiation of the EDA complex induced stepwise, sequential single-electron transfer (SET) processes to generate a HAT-active thiyl radical. The first SET was from the electron-rich naphthyl group of 7,7'-OMe-TPA to the protonated N-heteroaromatics and the second proton-coupled SET (PCET) from the thiophosphoric acid moiety of 7,7'-OMe-TPA to the resulting naphthyl radical cation. Spectroscopic studies and theoretical calculations characterized the stepwise SET process mediated by short-lived intermediates. This organocatalytic HAT system was applied to four different carbon-hydrogen (C-H) functionalization reactions, hydroxyalkylation and alkylation of N-heteroaromatics, acceptorless dehydrogenation of alcohols, and benzylation of imines, with high functional group tolerance.
15 citations
TL;DR: In this paper , a visible-light-promoted, electron donor−acceptor (EDA) complex enabled hydroxysulfenylation of styrenes has been developed with eco-friendly air (O2) as the oxygen source and green ethanol as the sole solvent.
15 citations
TL;DR: A review of photocatalytic late-stage C-H functionalization strategies for small molecule drugs, agrochemicals, and natural products can be found in this article .
Abstract: The emergence of modern photocatalysis, characterized by mildness and selectivity, has significantly spurred innovative late-stage C-H functionalization approaches that make use of low energy photons as a controllable energy source. Compared to traditional late-stage functionalization strategies, photocatalysis paves the way toward complementary and/or previously unattainable regio- and chemoselectivities. Merging the compelling benefits of photocatalysis with the late-stage functionalization workflow offers a potentially unmatched arsenal to tackle drug development campaigns and beyond. This Review highlights the photocatalytic late-stage C-H functionalization strategies of small-molecule drugs, agrochemicals, and natural products, classified according to the targeted C-H bond and the newly formed one. Emphasis is devoted to identifying, describing, and comparing the main mechanistic scenarios. The Review draws a critical comparison between established ionic chemistry and photocatalyzed radical-based manifolds. The Review aims to establish the current state-of-the-art and illustrate the key unsolved challenges to be addressed in the future. The authors aim to introduce the general readership to the main approaches toward photocatalytic late-stage C-H functionalization, and specialist practitioners to the critical evaluation of the current methodologies, potential for improvement, and future uncharted directions.
11 citations
References
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TL;DR: Five practical examples involving a wide variety of systems and analysis methods are given to illustrate the usefulness of Multiwfn, a multifunctional program for wavefunction analysis.
Abstract: Multiwfn is a multifunctional program for wavefunction analysis. Its main functions are: (1) Calculating and visualizing real space function, such as electrostatic potential and electron localization function at point, in a line, in a plane or in a spatial scope. (2) Population analysis. (3) Bond order analysis. (4) Orbital composition analysis. (5) Plot density-of-states and spectrum. (6) Topology analysis for electron density. Some other useful utilities involved in quantum chemistry studies are also provided. The built-in graph module enables the results of wavefunction analysis to be plotted directly or exported to high-quality graphic file. The program interface is very user-friendly and suitable for both research and teaching purpose. The code of Multiwfn is substantially optimized and parallelized. Its efficiency is demonstrated to be significantly higher than related programs with the same functions. Five practical examples involving a wide variety of systems and analysis methods are given to illustrate the usefulness of Multiwfn. The program is free of charge and open-source. Its precompiled file and source codes are available from http://multiwfn.codeplex.com.
17,273 citations
TL;DR: The conversion of these bench stable, benign catalysts to redox-active species upon irradiation with simple household lightbulbs represents a remarkably chemoselective trigger to induce unique and valuable catalytic processes.
Abstract: A fundamental aim in the field of catalysis is the development of new modes of small molecule activation. One approach toward the catalytic activation of organic molecules that has received much attention recently is visible light photoredox catalysis. In a general sense, this approach relies on the ability of metal complexes and organic dyes to engage in single-electron-transfer (SET) processes with organic substrates upon photoexcitation with visible light.
Many of the most commonly employed visible light photocatalysts are polypyridyl complexes of ruthenium and iridium, and are typified by the complex tris(2,2′-bipyridine) ruthenium(II), or Ru(bpy)32+ (Figure 1). These complexes absorb light in the visible region of the electromagnetic spectrum to give stable, long-lived photoexcited states.1,2 The lifetime of the excited species is sufficiently long (1100 ns for Ru(bpy)32+) that it may engage in bimolecular electron-transfer reactions in competition with deactivation pathways.3 Although these species are poor single-electron oxidants and reductants in the ground state, excitation of an electron affords excited states that are very potent single-electron-transfer reagents. Importantly, the conversion of these bench stable, benign catalysts to redox-active species upon irradiation with simple household lightbulbs represents a remarkably chemoselective trigger to induce unique and valuable catalytic processes.
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Figure 1
Ruthenium polypyridyl complexes: versatile visible light photocatalysts.
6,252 citations
TL;DR: In this paper, a geometrical analysis of π-π stacking in metal complexes with aromatic nitrogen-containing ligands was performed based on a Cambridge Structural Database search and on X-ray data of examples.
Abstract: A geometrical analysis has been performed on π–π stacking in metal complexes with aromatic nitrogen-containing ligands based on a Cambridge Structural Database search and on X-ray data of examples in the recent literature. It is evident that a face-to-face π–π alignment where most of the ring-plane area overlaps is a rare phenomenon. The usual π interaction is an offset or slipped stacking, i.e. the rings are parallel displaced. The ring normal and the vector between the ring centroids form an angle of about 20° up to centroid–centroid distances of 3.8 A. Such a parallel-displaced structure also has a contribution from π–σ attraction, the more so with increasing offset. Only a limited number of structures with a near to perfect facial alignment exists. The term π–π stacking is occasionally used even when there is no substantial overlap of the π-ring planes. There is a number of metal–ligand complexes where only the edges of the rings interact in what would be better described a C–H⋯π attraction.
3,881 citations
TL;DR: An overview of the basic photophysics and electron transfer theory is presented in order to provide a comprehensive guide for employing this class of catalysts in photoredox manifolds.
Abstract: In this review, we highlight the use of organic photoredox catalysts in a myriad of synthetic transformations with a range of applications. This overview is arranged by catalyst class where the photophysics and electrochemical characteristics of each is discussed to underscore the differences and advantages to each type of single electron redox agent. We highlight both net reductive and oxidative as well as redox neutral transformations that can be accomplished using purely organic photoredox-active catalysts. An overview of the basic photophysics and electron transfer theory is presented in order to provide a comprehensive guide for employing this class of catalysts in photoredox manifolds.
3,550 citations
TL;DR: In this paper, a set of criteria are proposed based on the theory of "atoms in molecules" to establish hydrogen bonding, even for multiple interactions involving C-H-O hydrogen bonds.
Abstract: It is shown that the total charge density is a valid source to confirm hydrogen bonding without invoking a reference charge density. A set of criteria are proposed based on the theory of “atoms in molecules” to establish hydrogen bonding, even for multiple interactions involving C-H-O hydrogen bonds. These criteria are applied to several van der Waals complexes. Finally a bifurcated intramolecular C-H-O hydrogen bond is predicted in the anti-AIDS drug AZT, which may highlight a crucial feature of the biological activity of a whole class of anti-AIDS drugs. Almost all the methods of physical chemistry, spectroscopy, and diffraction can be used to recognize and study hydrogen bonding.] Each technique focuses on specific properties in order to detect and characterize this phenomenon in its own way. This work is concerned with the manifestation of hydrogen bonding in the charge density obtained from ab initio calculations. Whereas crystallographers have concluded upon hydrogen bonding via purely geometrical criteria, recent deformation density2 studies allow one to observe hydrogen bonding beyond mere ge~metry.~ However, it is not necessary to subtract an arbitrary (promolecular) charge density from the total density to reveal hydrogen bonding, not even in the interpretation of X-ray experiment^.^ Boyd and Choi have shown in two important contribution^^^^ that the theory of “atoms in molecules’’ (AIM)7,8 can be used to characterize hydrogen bonding solely from the (total) charge density for a large set of acceptor molecules, involving HF and HC1 as donors. In a next stage Carroll and Bader performed a more extended analysis on a large set of BASE-HF comple~es.~ This theory has not only provided new insights in conventional intermolecular hydrogenI0.’ ] bonding but has also been successful in intramolecularI33l4 and x-type hydrogen bonds.I5 Drawing from earlier ob~ervations~~~~ ~.’~~~~ and the present work, we formulate eight concerted effects occurring in the charge density which are indicative of hydrogen bonding. All of these effects can be viewed as necessary criteria to conclude that hydrogen bonding is present. By observation one of these conditions has proven to be sufficient as well. This case study on C-H-O interactions shows that this less common type of hydrogen bonding obeys all of the proposed criteria. Moreover, the multiple interactions appearing in the present five examples do not impair the consistency of the global phenomenon of hydrogen bonding as it expresses itself in the charge density. In spite of an early affirmative infrared review,I6 the old controversy on whether C-H-O hydrogen bonds really exist continued for another decade,” but now the dust has settled’* (for an entertaining account of this controversy, see ref 19). The importance of these bonds has been recognized in crystal engineering’9,20 since C-H-O contacts have a determining influence on packing motifs.21
2,654 citations