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Vinyl thianthrenium salt is a compound with interesting electrophilic properties capable of reacting with two distinct nucleophiles. By using β‐keto esters as one of the reaction partners, it is possible to insert a chain of two carbon atoms with a further functionalization under mild conditions. We have studied this new methodology which involves the stepwise formation of a C−C and a C−X bond (with X=N, O, etc.) in one step without the use of metals. Depending on the reaction conditions and the starting ketoester, a varied reactivity has been observed and described. [ABSTRACT FROM AUTHOR]

Dual photoredox catalysis has revolutionized the field of cross‐coupling reactions, enabling the discovery of numerous highly efficient reactions. This breakthrough is attributed to the exceptional combination of nickel catalysis with photoredox catalysis. Nickel exhibits both oxidative addition and reductive elimination processes, and a wide range of oxidation states (ranging from I to IV) accessible within a single catalytic cycle. Furthermore, nickel complexes are capable of catalyzing various processes through radical mechanisms. The latest feature has proven to be incredibly potent in facilitating the formation of new C−C and C−X bonds (X=H, O, S, N). The powerful combination of photoredox and nickel catalysis reveals an expansive domain of unexplored possibilities. It offers unparalleled opportunities for improving reactions and exploring innovative pathways. Under photoredox conditions, it is possible to form nucleophilic reactive organometallic intermediates, useful in reaction with electrophiles. We have devoted a research program towards the rediscovery and use of organometallic reagents, introduced by Corey, Hegedus, and Semmelack many years ago. The results unveiled the extraordinary capabilities of photoredox catalysis, enabling the creation and efficient utilization of potent nucleophilic organometallic reagents under mild conditions, free from the need for strong bases or stoichiometric metal reductants. [ABSTRACT FROM AUTHOR]

Donor–acceptor dyads based on BODIPYs have been recently employed to enhance the formation of triplet excited states with the process of spin–orbit charge transfer intersystem crossing (SOCT-ISC) which does not require introduction of transition metals or other heavy atoms into the molecule. In this work we compare two donor–acceptor dyads based on meso-naphthalenyl BODIPY by combining experimental and computational investigations. The photophysical and electrochemical characterization reveals a significant effect of alkylation of the BODIPY core, disfavoring the SOCT-ISC mechanism for the ethylated BODIPY dyad. This is complemented with a computational investigation carried out to rationalize the influence of ethyl substituents and solvent effects on the electronic structure and efficiency of triplet state population via charge recombination (CR) from the photoinduced electron transfer (PeT) generated charge-transfer (CT) state. Time dependent-density functional theory (TD-DFT) calculations including solvent effects and spin–orbit coupling (SOC) calculations uncover the combined role played by solvent and alkyl substitution on the lateral positions of BODIPY. [ABSTRACT FROM AUTHOR]

Dual photoredox catalysis is modifying the approach to sustainable metal catalysis based on metals in low oxidation state, as the use of stoichiometric metal as reductants are avoided. In this study, we showcase the potential use of vanadium in a dual photoredox process, allowing us to effectively control the formation of V(II) and its corresponding chemical reactions. A diastereoselective pinacol coupling with aromatic aldehydes is described. The process shows broad scope, and interestingly, unprotected salicylic aldehydes are compatible with the reaction protocol. Additionally, among all the ligands investigated we found that inexpensive bipyridines control the diastereoselection of the reaction favoring the d,l chiral compound (dr>20:1 for most of the aldehydes investigated). To promote the reaction and avoid an unproductive and not stereoselective radical coupling of the generated ketyl radical, the use of [DMQA]+, a stable organic dye, was found crucial. Furthermore, this dye possesses the remarkable capability of efficiently capturing light in the red segment of the visible spectrum, effectively raising efficiency of the protocol. The utilization of red light carries notable advantages in terms of penetration and safety, making it particularly significant. Moreover, careful photophysical investigations were able to give indications about the mechanism of the reaction. [ABSTRACT FROM AUTHOR]

For the first time, a dual photoredox‐ and titanocene‐catalyzed methodology for the regioselective access to α‐vinyl‐β‐hydroxy esters towards aldehyde allylation with 4‐bromobut‐2‐enoate is reported. The protocol is based on the Barbier‐type properties of the inexpensive and available Cp2TiCl2 in catalytic amount (5 mol%). The developed mild reaction conditions gave access to a library of differently functionalized α‐vinyl‐β‐hydroxy esters in moderate diastereoselectivity, employing the commercially available ethyl 4‐bromobut‐2‐enoate and both aromatic and aliphatic aldehydes. The reaction was realized under visible light irradiation, in the presence of an organophotocatalyst (3DPAFIPN, 2 mol%) combined with Hantzsch's ester as the sacrificial reductant. In contrast to other Barbier‐type reactions employing ethyl 4‐bromobut‐2‐enoate, the photoredox system ensures a better regioselectivity. Moreover, the use of preformed organometallic nucleophilic species (e. g. dienolborinates), and the need of metal reductants or stoichiometric amount of transition metals in low oxidation state for Barbier‐type reactions, is avoided. To support the experimental evidence, a detailed photophysical study shed light on the mechanism of the reaction. [ABSTRACT FROM AUTHOR]

A new meso‐naphthalenyl BODIPY was designed for the efficient generation of long‐lived triplet excited state under irradiation with green light. The new, heavy atom‐free organic chromophore was employed in a benchmark example of dual palladium and photoredox catalysis, highlighting the applications of BODIPY dyes as photoredox catalysts. [ABSTRACT FROM AUTHOR]

A regioselective vinylation of aromatic and aliphatic aldehydes promoted by the merging of photoredox and nickel catalysis is here reported. A comprehensive investigation on the reaction conditions allowed the disclosure of a valid and reproducible protocol based on a nickel‐mediated reductive coupling approach under visible light irradiation. The employment of 3CzClIPN (2,4,6‐tris(carbazol‐9‐yl)‐5‐chloro‐isophthalonitrile) as the photocatalyst and Hantzsch's ester as the sacrificial organic reductant replace the use of boron‐, silicon‐ or zinc‐based reducing agents, making this method a worthy alternative to the already known protocols. The developed mild reaction conditions allow the access to a wide range of substituents decorating both the aldehyde and the alkyne. Moreover, careful photophysical investigations shed light on the mechanism of the reaction. [ABSTRACT FROM AUTHOR]

Organochromium(III) species are multipurpose nucleophiles used in the synthesis of complex organic molecules due to their high functional group tolerance and extraordinary chemoselectivity for aldehydes. The preparation of organochromium(III) species starting from organic halides requires the use of a stoichiometric amount of chromium(II) salts or a catalytic amount of chromium(III) salts in the presence of stoichiometric reductants (such as Mn(0)). Recently, radicals formation from readily available alkenes, followed by their trapping with stoichiometric or catalytic amount of chromium(II) salts were reported in photoredox conditions for the generation of Cr(III) organometallic species. In this paper we disclose a real Nozaki‐Hiyama reaction (NH) in which photoredox conditions enable the preparation of Cr(III) allyl reagents starting from available allyl halides and stable Cr(III) salts. [ABSTRACT FROM AUTHOR]

Irradiation with red light is able to improve yields and shorten the reaction time in enzymatic reactions. A commercially available laccase from Trametes versicolor, used in conjunction with a catalytic amount of TEMPO (20 mol%), was irradiated under red light (630 nm) for the clean oxidation of benzylic alcohols and amines in a faster reaction compared to the one conducted in the dark, affording the desired product in excellent yields (up to 99%) using air as the terminal oxidant. The observed acceleration is due to the strongest oxidation ability of laccase, in its excited state, towards TEMPO. [ABSTRACT FROM AUTHOR]

A new BODIPY derivative (o-I–BDP) containing an iodine atom in the ortho position of the meso-linked phenyl group was prepared. Photophysical and electrochemical properties of the molecule were compared to previously reported iodo BODIPY derivatives, as well as to the non-iodinated analog. While in the case of derivatives featuring iodine substituents in the BODIPY core, efficient population of the triplet state is accompanied by a substantial positive shift of the reduction potential compared to pristine BODIPY, o-I–BDP displays phosphorescence and simultaneously maintains the electrochemical properties of unsubstituted BODIPYs. A theoretical investigation was settled to analyze results and rationalize the influence of iodine position on electronic and photophysical properties, with the purpose of preparing a fully organic phosphorescent BODIPY derivative. TD-DFT and spin–orbit coupling calculations shed light on the subtle effects played by the introduction of iodine atom in different positions of BODIPY. [ABSTRACT FROM AUTHOR]

Here we report a practical, highly enantioselective photoredox allylation of aldehydes mediated by chiral nickel complexes with commercially available allyl acetate as the allylating agent. The methodology allows the clean stereoselective allylation of aldehydes in good to excellent yields and up to 93 % e.e. using a catalytic amount of NiCl2(glyme) in the presence of the chiral aminoindanol‐derived bis(oxazoline) as the chiral ligand. The photoredox system is constituted by the organic dye 3DPAFIPN and a Hantzsch's ester as the sacrificial reductant. The reaction proceeds under visible‐light irradiation (blue LEDs, 456 nm) at 8–12 °C. Compared to other published procedures, no metal reductants (such as Zn or Mn), additives (e.g. CuI) or air‐sensitive Ni(COD)2 are necessary for this reaction. Accurate DFT calculations and photophysical experiments have clarified the mechanistic picture of this stereoselective allylation reaction. [ABSTRACT FROM AUTHOR]

Here we report a practical, highly enantioselective photoredox allylation of aldehydes mediated by chiral nickel complexes with commercially available allyl acetate as the allylating agent. The methodology allows the clean stereoselective allylation of aldehydes in good to excellent yields and up to 93 % e.e. using a catalytic amount of NiCl2(glyme) in the presence of the chiral aminoindanol‐derived bis(oxazoline) as the chiral ligand. The photoredox system is constituted by the organic dye 3DPAFIPN and a Hantzsch's ester as the sacrificial reductant. The reaction proceeds under visible‐light irradiation (blue LEDs, 456 nm) at 8–12 °C. Compared to other published procedures, no metal reductants (such as Zn or Mn), additives (e.g. CuI) or air‐sensitive Ni(COD)2 are necessary for this reaction. Accurate DFT calculations and photophysical experiments have clarified the mechanistic picture of this stereoselective allylation reaction. [ABSTRACT FROM AUTHOR]

Calix[4]pyrroles can be obtained from the efficient preprogrammed condensation between acetone and pyrrole. This reaction forms the attractive macrocycle resembling in its constitution, but not in its oxidation state, to the porphyrin structure, prominently present in the vital "pigments of life". Calix[2]pyrrolidine[2]pyrrole and calix[4]pyrrolidine, the partially and totally reduced version of the macrocycle, became accessible through the hydrogenation of calix[4]pyrrole, but only under strenuous reaction conditions. The only known hydrogenation, which could give clues for improving the process, was the reduction of the calix[4]furan. To shed light on the process, mixed calix[n]furan[4‐n]pyrroles were prepared, and their hydrogenation was studied. After a laborious optimization process, the best conditions were discovered improving the yield of the hydrogenation process from the level of a formation to the level of a complete conversion. The calix[4]pyrrolidine is now accessible in two high yielding synthetic steps. The efforts to understand and to optimize the factors involved in the hydrogenation process of this perazamacrocycle are here reviewed. [ABSTRACT FROM AUTHOR]

Photoredox reactions involving allyl and vinyl nucleophiles in the presence of nickel enable precise control over diastereoselectivity and enantioselectivity, without the need for noble metals or costly and highly reactive stoichiometric reductants. More information can be found in the review article by P. G. Cozzi and co‐workers...By Andrea Gualandi; Francesco Calogero; Dario Corbisiero; Emanuele Pinosa and Pier Giorgio CozziReported by Author; Author; Author; Author; Author [Extracted from the article]

Organometallic allylic reagents are widely used in the construction of C−C bonds by Barbier‐type reactions. In this communication, we have described a photoredox Barbier allylation of aldehydes mediated by bismuth, in absence of other metals as co‐reductants. Mild reaction conditions, tolerance of oxygen, and use of aqueous solvent make this photoredox methodology attractive for green and sustainable synthesis of homoallylic alcohols. [ABSTRACT FROM AUTHOR]

The preparation of homoallylic alcohols by addition of organometallic allyl compounds to carbonyls is an important strategy in organic chemistry. Allylating organometallic cobalt species can be generated employing stoichiometric quantities of Zn acting as reductant. To avoid the employment of stoichiometric amount of Zn, we have developed an allylation reaction of aromatic and aliphatic aldehydes promoted by photoredox catalysis in the presence of a cobalt complex, and we present herein a full account of our research. In the presence of the abundant CoBr2 (10 mol %), 4,4′‐di‐tert‐butyl‐2,2′‐dipyridyl (dtbbpy, 10 mol %), allyl acetate (3 equiv.), [Ir(dtbbpy)(ppy)2]PF6 (ppy=2‐phenylpyridine, 2 mol %), and N,N‐diisopropylethylamine (4 equiv.), an allylation of aldehydes is taking place, in moderate to good yields. Substrates scope, limitations, and photophysical investigations of this new process are reported. [ABSTRACT FROM AUTHOR]

High level time‐dependent density functional theory (TD‐DFT) computational modeling of coumarin dyes has been exploited for guiding the design of effective photocatalysts (PCs). A library of coumarins were investigated from the theoretical point of view and photophysical/electrochemical properties (absorption and emission spectra, E00, oxidation and reduction potentials) were evaluated. Comparison with literature values reported for a few candidates has been used for assessing the level of theory. On the basis of the results obtained, new strongly reducing PCs [Eox(PC.+/PC*)=−2.1 – −2.0 V vs SCE] were discovered. Through the computational study of structure‐properties relationships, a number of coumarins derivatives have been synthesized and evaluated in the pinacol coupling of aldehydes as the model reaction. The new organic photoredox catalysts show experimental photophysical and electrochemical data in accordance with the ones predicted by calculation, with excited state reduction potentials surpassing those of highly reducing transition metal‐based PCs. A careful investigation of their behavior as PC has revealed crucial issues that need to be taken into consideration in the general photoredox catalysis, shedding light on the use of these PC in the pinacol, as well as, in other photoredox reactions. [ABSTRACT FROM AUTHOR]

This work aims at using two borane derivatives, namely Borane A: B(C6F5)3 and Borate B: C32H12BF24Na as additives for the cationic polymerization of epoxy silicones under visible light, in the presence of coumarins as photosensitizers and 4‐isopropyl‐4′‐methyldiphenyl iodonium tetrakis(pentafluorophenyl)borate (SC939). The effect of boron compounds on the absorption and the emission spectra of a coumarin is particularly outlined. These two boron compounds can improve both the polymerization rate and the final monomer conversion. Moreover, the effect of adding water on the reactivity of the system is studied. It should be noted that the studied boron additives are able to enhance in an interesting way the polymerization rate when light irradiation is switched off through a dark polymerization (DP) mechanism. This latter behavior is highly desired for practical applications. Finally, the very high photoreactivity of boron compounds is employed for the development of new cationic 3D printing resins upon exposure to a light emitting diode (LED) projector at 405 nm, as well as for direct laser write experiments, by means of a laser diode at 405 nm. The 3D polymerization occurs through a cationic process which can be quite useful in order to reduce the shrinkage usually observed in radical polymerization. [ABSTRACT FROM AUTHOR]

Titanium is one of the most abundant and environmentally innocuous metals. Ti‐based organometallic compounds have long been used as versatile homogeneous catalysts in synthetic chemistry and still remain highly attractive for the development of sustainable transformations. With the emerging role of photoredox catalysis, the selectivity of the radical initiation in electron transfer‐mediated reactions has been shown to be fundamental in terms of synthesis efficiency. Recent examples have displayed the effectiveness of inorganic and organic chromophores at the excited state in triggering the redox chemistry of TiIV/III complexes. In this minireview, we will illustrate the underlying principles and practicability of these – still uncommon – metallaphotoredox catalytic reactions. [ABSTRACT FROM AUTHOR]

Phenylmethanimine is an aromatic imine with a twofold relevance in chemistry: organic synthesis and astrochemistry. To tackle both aspects, a multidisciplinary strategy has been exploited and a new, easily accessible synthetic approach to generate stable imine‐intermediates in the gas phase and in solution has been introduced. The combination of this formation pathway, based on the thermal decomposition of hydrobenzamide, with a state‐of‐the‐art computational characterization of phenylmethanimine laid the foundation for its first laboratory observation by means of rotational electric resonance spectroscopy. Both E and Z isomers have been accurately characterized, thus providing a reliable basis to guide future astronomical observations. A further characterization has been carried out by nuclear magnetic resonance spectroscopy, showing the feasibility of this synthetic approach in solution. The temperature dependence as well as possible mechanisms of the thermolysis process have been examined. [ABSTRACT FROM AUTHOR]

The construction of a hybrid metal-organo-photoredox catalyst based on the conjugation of an imidazolidinone organocatalyst and Ir(ppy)2(bipy) (ppy = 2-phenylpyridine, bipy = bipyridine) is described. The introduction of the desired organocatalyst into the bipyridine moiety is quite modular, allowing the preparation of different hybrid photocatalysts, and is realized though a simple click reaction. The hybrid photocatalysts obtained were employed in the benchmark photoredox alkylation of aldehydes. Remarkably, the conjugation of a first-generation MacMillan catalyst produces an active and stereoselective hybrid photoredox catalyst. [ABSTRACT FROM AUTHOR]

Metallosalen are privileged complexes that have found important applications in catalysis. In addition, their luminescent properties have also been studied and used for sensing and biological applications. Salen metal complexes can be efficient photosensitizers, but they can also participate to electron transfer processes. Indeed, we have found that commercially available [Al(Salen)Cl] is an efficient photoredox catalyst for the synergistic stereoselective reaction of alkyl aldehydes with different bromo ketones and malonates to give the corresponding enantioenriched α‐alkylated derivatives. The reaction was performed in the presence of a MacMillan catalyst. [Al(Salen)Cl] is able to replace ruthenium complexes, showing that also aluminum complexes can be used in promoting photoredox catalytic reactions. [ABSTRACT FROM AUTHOR]

Organocatalysis—the branch of catalysis featuring small organic molecules as the catalysts—has, in the last decade, become of central importance in the field of asymmetric catalysis, so much that it is now comparable to metal catalysis and biocatalysis. Organocatalysis is rationalized and classified by a number of so-called activation modes, based on the formation of a covalent or not-covalent intermediate between the organocatalyst and the organic substrate. Among all the organocatalytic activation modes, enamine and iminium catalysis are widely used for the practical preparation of valuable products and intermediates, both in academic and industrial contexts. In both cases, chiral amines are employed as catalysts. Enamine activation mode is generally employed in the reaction with electrophiles, while nucleophiles require the iminium activation mode. Commonly, in both modes, the reaction occurs through well-organized transitions states. A large variety of partners can react with enamines and iminium ions, due to their sufficient nucleophilicity and electrophilicity, respectively. However, despite the success, organocatalysis still suffers from narrow scopes and applications. Multicatalysis is a possible solution for these drawbacks because the two different catalysts can synergistically activate the substrates, with a simultaneous activation of the two different reaction partners. In particular, in this review we will summarize the reported processes featuring Lewis acid catalysis and organocatalytic activation modes synergically acting and not interfering with each other. We will focus our attention on the description of processes in which good results cannot be achieved independently by organocatalysis or Lewis acid catalysis. In these examples of cooperative dual catalysis, a number of new organic transformations have been developed. The review will focus on the possible strategies, the choice of the Lewis acid and the catalytic cycles involved in the effective reported combination. Additionally, some important key points regarding the rationale for the effective combinations will be also included. π-Activation of organic substrates by Lewis acids, via formation of electrophilic intermediates, and their reaction with enamines will be also discussed in this review. [ABSTRACT FROM AUTHOR]

Here we report the application of dual nickel/photoredox catalysis to the allylation of aliphatic, aromatic and heteroaromatic aldehydes by using commercially available reagents. The process utilizes the combination of a Ni(ii) complex, [Ru(bpy)3]2+ as a photoredox catalyst, and allylacetate under blue LED irradiation, and allows the synthesis of a large variety of homoallylic alcohols. [ABSTRACT FROM AUTHOR]

We describe a novel efficient photochemical procedure for the direct iodoperfluoroalkylation of terminal olefins. The process uses a simple and inexpensive perylenediimide (PDI) in an extremely low catalytic loading and occurs with visible light irradiation. The reported methodology is highly viable from a synthetic point of view, since it proceeds under mild reaction conditions with a significant rate of production. Preliminary mechanistic investigations are also reported. A little goes a long way! A novel efficient photochemical procedure for the direct iodoperfluoroalkylation of terminal olefins was reported. The process uses a simple and inexpensive perylenediimide (PDI) in an extremely low catalytic loading (500 ppm) and occurs with visible‐light irradiation [ABSTRACT FROM AUTHOR]

The Front Cover celebrates the combination of photoredox catalysis with titanium catalysis and all the exciting and stimulating transformations that can be achieved without the use of metal reductants. In the present report, the combination of an organophotocatalyst with a catalytic amount of titanocene dichloride gave access to a library of differently functionalized α‐vinyl‐β‐hydroxy esters through an α‐selective vinylogous Reformatsky approach emploiyng the Hantzsch’ ester as stoichiometric organic reductant. More information can be found in the Research Article by P. G. Cozzi, F. Calogero et al. [ABSTRACT FROM AUTHOR]

Aldehydes, photoredox, titanium catalysis, vinylogous aldol reaction, -Vinyl- -Hydroxy Esters Front Cover: A Dual Photoredox- and Cp2TiCl2-Catalyzed Approach for the Direct Access to -Vinyl- -hydroxy Esters (Eur. J. Org. Keywords: aldehydes; photoredox; titanium catalysis; vinylogous aldol reaction; -Vinyl- -Hydroxy Esters EN aldehydes photoredox titanium catalysis vinylogous aldol reaction -Vinyl- -Hydroxy Esters 1 1 1 10/12/23 20231009 NES 231009 B The Front Cover b celebrates the combination of photoredox catalysis with titanium catalysis and all the exciting and stimulating transformations that can be achieved without the use of metal reductants. [Extracted from the article]

A gas‐phase nitrogen–nitrogen noncovalent interaction has been unveiled in the nitroethane–trimethylamine complex in an environment free from solvent and matrix effects using rotational spectroscopy in supersonic expansion. Different quantum chemical models (NOCV/CD and NBO) agree in indicating that this interaction largely prevails over the C−H⋅⋅⋅O and C−H⋅⋅⋅N hydrogen bonds. Furthermore, a SAPT analysis shows that electrostatic and dispersion interactions play a comparable role in stabilizing the complex. The conformational landscape exploration and stationary points characterization have been performed using state‐of‐the‐art quantum‐chemical computations providing significant insights on structure determination. A gas‐phase nitrogen–nitrogen noncovalent interaction has been unveiled in an environment free from solvent and matrix effects using rotational spectroscopy in supersonic expansion. This interaction largely prevails over the C−H⋅⋅⋅O and C−H⋅⋅⋅N hydrogen bonds as pointed out by different models for energy/charge partitioning. A SAPT analysis shows that electrostatic and dispersion interactions play a comparable role in stabilizing the complex. [ABSTRACT FROM AUTHOR]

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In recent years, the field of organocatalysis has extensively explored the use of carbenium ions for practical C−C bond forming reactions. In order to control the formation of new stereocenters, the generation of carbenium ions was investigated by exploring asymmetric Brønsted acid catalysis. Oxocarbenium ions, iminium ions, and other carbenium ions stabilized by heteroatoms could also be generated by Brønsted acid catalysis, through the departure of suitable leaving groups. The aforementioned reactivity has recently been exploited leading to remarkable achievements. The application of chiral Brønsted acids in the generation of heteroatom stabilized carbenium ions has recently been investigated, with the demonstration of important results. Although diverse architectural arrays of Brønsted acid catalysts were conceived, BINOL‐derived phosphoric acids have played a dominant role in this area of research. Their low pKa values combined with the possibility to alter their architecture, and their ability to assemble ordered transition states was exploited in different SN1‐type reactions allowing the formation of a variety of products with high enantiomeric excesses. In addition, the generation of highly stabilized chiral counter anions allowed the exploitation of counterion asymmetric catalysis with various nucleophiles. Go fish! Carbenium ions generated under Brønsted acids conditions are suitable activated precursors for C−C and C−X (X=O, N, S) bond‐formation reactions. Through cooperativity, control of pKa, and by secondary interactions it is possible to control the stereoselective formations of new bonds to a remarkable level, by using chiral Brønsted acids. [ABSTRACT FROM AUTHOR]

Here we report the application of readily prepared and available coumarin dyes for photoredox catalysis, which are able to mimic powerful reductant [Ir(iii)] complexes. Coumarin derivatives 9 and 10 were employed as photoreductants in pinacol coupling and in other reactions, in the presence of Et3N as a sacrificial reducing agent. As the electronic, photophysical, and steric properties of coumarins could be varied, a wide applicability to several classes of photoredox reactions is predicted. [ABSTRACT FROM AUTHOR]

Abstract: Salophens and Salens are Schiff bases generated through the condensation of two equivalents of salicylaldehyde with either 1,2‐phenylenediamines or aliphatic diamines, respectively. Both ligands have been extensively exploited as key building blocks in coordination chemistry and catalysis. In particular, their metal complexes have been widely used for various catalytical transformations with high yield and selectivity. Through the modification of the phenol unit it is possible to tune the steric hindrance and electronic properties of Salophen and Salen. The introduction of long aliphatic chains in salicylaldehydes can be used to promote their self‐assembly into ordered supramolecular structures on solid surfaces. Herein, we report a novel method towards the facile synthesis of robust and air‐stable [Al(Salophen)] derivatives capable of undergoing spontaneous self‐assembly at the graphite/solution interface forming highly‐ordered nanopatterns. The new synthetic approach relies on the use of [MeAlIII(Salophen)] as a building unit to introduce, via a simple acid/base reaction with functionalized acidic phenol derivatives, selected frameworks integrating multiple functions for efficient surface decoration. STM imaging at the solid/liquid interface made it possible to monitor the formation of ordered supramolecular structures. In addition, the redox properties of the Salophen derivatives functionalized with ferrocene units in solution and on surface were unraveled by cyclic voltammetry. The use of a five‐coordinate aluminum alkyl Salophen precursor enables the tailoring of new Salophen molecules capable of undergoing controlled self‐assembly on HOPG, and thereby it can be exploited to introduce multiple functionalities with subnanometer precision at surfaces, ultimately forming ordered functional patterns. [ABSTRACT FROM AUTHOR]

A mechanism based on the sequential absorption of two photons by the components of a redox couple has been recently proposed for catalysis of the energetically demanding reduction of aryl halides. Here, we analyze the suggested photochemical mechanism of this reaction, which employs perylenediimide (PDI) as a photocatalyst, on the basis of spectroscopic, electrochemical and electron paramagnetic resonance data. Our results indicate that the photoexcited PDI radical anion (*PDIṖ−) cannot play the role of a photosensitizer in the aforementioned process. Instead, the reduction of 4′-bromoacetophenone likely involves *PDIṖ− decomposition products. The extremely short lifetime of the photoexcited transient species, as *PDIṖ−, is a major general limitation for photocatalytic schemes based on sequential two-photon excitation. In order to better understand the potential of such schemes, we discuss them in the context of the Z-scheme in natural photosynthesis. [ABSTRACT FROM AUTHOR]

Catalysis based on precious metals has reached an incredible level of sophistication and has found widespread use and application, both in academia and in industry. However, owing to the environmental impact, cost, and low abundance, catalysis based on inexpensive, abundant, and environmentally benign first-row transition metals has become a valuable alternative to traditional reactions promoted by their less-abundant counterparts. From economic and ecological perspectives, iron salts and iron metal complexes are highly promising candidates to replace costly and toxic metals. In recent years, iron complexes have been used to promote the formation of radicals. Photoredox chemistry is a valuable method for the generation of radical species under mild conditions, but it often relies on rare-earth-metal complexes. The employment of iron complexes for the generation of radicals is attractive for the development of sustainable, simple, and effective procedures. In this Focus Review, we highlight and summarize recent radical reactions promoted by iron complexes and their application in organic reactions. [ABSTRACT FROM AUTHOR]

Stereoselective alkylation of enolates represents a valuable and important procedure for accessing carbon-carbon-bond frameworks in natural and nonnatural product synthesis. Usually, activated electrophilic partners that react through an SN2 mechanism are employed. To overcome the limitations due to reduced reactivity and steric hindrance, SN1-type reactions can be considered a valid and practical alternative. Accessible enolates can be used in stereoselective (diastereo- or enantioselective) reactions with electrophilic carbenium ions, either used as stable reagents or generated in situ from suitable precursors. The results achieved in this active field are summarized in this review. 1 Introduction 2 Alcohols in SN1-Type Reactions with Enolates 2.1 Enantioselective Reactions with Metal Complexes 2.2 Organocatalytic Enantioselective Reactions 3 Alcohols and Alcohol Derivatives in SN1-Type Reactions with Enolates: Enantioselective Reactions with Metal Enolates 4 Isolated Carbenium Ions in SN1-Type Reactions with Enolates: Enantioselective Reactions with Metal Enolates 5 Miscellaneous 6 Conclusion. [ABSTRACT FROM AUTHOR]

The octa-1,7-diene-4,5-diamine skeleton is usually prepared by the addition of allylic organometallic reagents to glyoxal diimines. The relative and absolute configurations of the C4 and C5 stereocenters are dependent on the nature of the (chiral) nitrogen substituents. These compounds are useful intermediates for the construction of NHC carbene complexes and nitrogen heterocycles, such as 2,2′-bipyrrolidines, 2,5-diazabicyclo[2.2.1]heptanes, amino- and hydroxy-substituted 7-azanorbornane, and diamino-substituted cyclohexanols and cyclohexanediols. [ABSTRACT FROM AUTHOR]

A direct and simple activation of quinolines, without isolating unstable intermediates, or using isolated N,O-acetals in the presence of Lewis or Brønsted acids, is described. The procedure is quite straightforward and allows the addition in a stereoselective manner of different aldehydes to various differently substituted quinolines. The desired products were obtained in 28-76 % yields, with dr values up to 83:17 in favor of the syn isomer, and up to 99 % ee. Studies towards the use of acetaldehyde were also performed with different catalysts and the addition was promoted affording the desired product in 62 % yield with 46 % ee. Finally, deprotection and chemical transformations of the enantioenriched adducts were performed. [ABSTRACT FROM AUTHOR]

What do quantum cellular automata (QCA), 'on water' reactions, and SN1-type organocatalytic transformations have in common? The link between these distant arguments is the practical access to useful intermediates and key products through the use of stabilized carbenium ions. Over 10 years, starting with a carbenium ion bearing a ferrocenyl group, to the 1,3-benzodithiolylium carbenium ion, our group has exploited the use of these intermediates in useful and practical synthetic transformations. In particular, we have applied the use of carbenium ions to stereoselective organocatalytic alkylation reactions, showing a possible solution for the 'holy grail of organocatalysis'. Examples of the use of these quite stabilized intermediates are now also considered in organometallic chemistry. On the other hand, the stable carbenium ions are also applied to tailored molecules adapted to quantum cellular automata, a new possible paradigm for computation. Carbenium ions are not a problem, they can be a/the solution! [ABSTRACT FROM AUTHOR]

The first catalytic asymmetric addition of TosMIC to unactivated ketones is presented. A combination of Me2Zn and aminoalcohol catalyst promoted the aldol ad-dition/cyclization reaction to render oxazolines possessing a fully substituted stereocenter with excellent yields (up to 92%), high enantioselectivities (up to 96%), and complete diastereoselectivity. The chiral oxazolines were then used to give, after a straightforward acid hydrolysis, enan-tioenriched building blocks bearing tertiary alcohol motifs such as hydroxylaldehydes, hydroxylacids, and hydroxyles-ters without racemization. [ABSTRACT FROM AUTHOR]

Cover Feature: A Photoredox Nozaki-Hiyama Reaction Catalytic in Chromium (Eur. J. Org. Keywords: Aldehydes; Allylbromide; Blue LED; Nozaki-Hiyama Reaction Photoredox catalysis EN Aldehydes Allylbromide Blue LED Nozaki-Hiyama Reaction Photoredox catalysis 1 1 1 08/09/22 20220805 NES 220805 B The Cover Feature b celebrates Japanese chemists Prof. Hitosi Nozaki and Prof. Tamejiro Hiyama, who discovered the Cr-mediated allyl addition to aldehydes. This work reports a catalytic photoredox version of the Nozaki-Hiyama reaction, without any problem related to the use of stoichiometric Mn or Zn as reducing agents....Mondai arimasen!. [Extracted from the article]

The combination of a practical and highly enantioselective organocatalytic reaction, which allows the stereoselective introduction of a benzodithiol group, with a fluorination step, gives a new and effective strategy for the stereoselective synthesis of difluorinated building blocks. The benzodithiol group is a versatile and chameleonic group that can be further functionalized before fluorination, giving customized and tailored useful synthetic strategies. As an example of the application of this facile strategy, the effective enantioselective synthesis of difluoroarundic acid is described. [ABSTRACT FROM AUTHOR]

Stable diarylcarbenium salts, obtained by the direct coupling of indole or indole derivatives with aryl (or heteroaryl) aldehydes in the presence of a strong organic Brønsted acid, have been employed in the direct alkylation of aldehydes. Excellent enantiomeric excesses and good diastereomeric ratios were obtained with a number of aryl or heteroaryl(3-indolyl)carbenium ions as the highly stable o-benzenedisulfonimide (OBS) salts and with the reaction promoted by the Hayashi-Jørgensen catalyst. A one-pot, three-component, stereoselective alkylation of aldehydes affording the same compounds was also investigated with various aldehydes, indole derivatives, and organocatalysts. The results obtained with the isolated carbenium ions were superior in terms of yields and stereoselectivity. [ABSTRACT FROM AUTHOR]