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Imine-linked covalent organic frameworks (COFs) are highly ordered polymer networks that are more chemically stable compared to their boron-linked counterparts making them more attractive for a variety of applications, including as energy storage devices, proton-conductive membranes, and catalytic supports. Furthermore, these imines linked COFs may be synthesized using a diverse spectrum of monomers, providing tremendous design freedom and versatility. We report a general method for synthesizing Imine linked COFs based on the Schiff-base condensation reaction of anilines. The synthesis of 4,4′,4′′-(benzene-1,3,5-triyltris(ethyne-2,1-diyl) trianiline, 4,4′-dicarbaldehyde, 4,4′-(ethyne-1,2-diyl) dibenzaldehyde (BPDA), and terephthalaldehyde (PDA) monomers produced by multistep coupling processes. [ABSTRACT FROM AUTHOR]

The asymmetric catalytic synthesis of 1,2-diamines has received considerable interest, especially in the last ten years, due to their presence in biologically active compounds and their applications for the development of synthetic building blocks, chiral ligands and organocatalysts. Synthetic strategies based on C–N bond-forming reactions involve mainly (a) ring opening of aziridines and azabenzonorbornadienes, (b) hydroamination of allylic amines, (c) hydroamination of enamines and (d) diamination of olefins. In the case of C–C bond-forming reactions are included (a) the aza-Mannich reaction of imino esters, imino nitriles, azlactones, isocyano acetates, and isothiocyanates with imines, (b) the aza-Henry reaction of nitroalkanes with imines, (c) imine–imine coupling reactions, and (d) reductive coupling of enamines with imines, and (e) [3+2] cycloaddition with imines. C–H bond forming reactions include hydrogenation of C＝N bonds and C–H amination reactions. Other catalytic methods include desymmetrization reactions of meso-diamines. [ABSTRACT FROM AUTHOR]

A catalytic asymmetric vinylogous aldol reaction between β,γ-unsaturated amides and isatins has been developed. In the presence of 10 mol% of tertiary amine-thiourea C7, the vinylogous reaction has been achieved in up to 98% yield and up to 99% ee (26 examples). This methodology provides an efficient approach to construct chiral multifunctional 3-hydroxy-2-oxindoles. Moreover, the transformations of the chiral products, including the esterification of amides, the hydrogenation of the C–C double bond and further conversion to spirolactones, have been investigated. [ABSTRACT FROM AUTHOR]

The document is the contents list for an issue of the journal Chemical Communications. It includes the titles and authors of various articles and features that will be included in the issue. Some of the topics covered include silk-based intelligent fibers and textiles, advances in molecular engineering of perovskite heterostructures, and metal-organic framework based self-powered devices for human body energy harvesting. The journal is published by The Royal Society of Chemistry, a leading chemistry community. [Extracted from the article]

A highly efficient asymmetric [3+2] and [4+2]-annulation of cyclic N-sulfonyl ketimines with γ- or δ-hydroxy-α,β-unsaturated ketones has been developed. This innovative reaction employs an organocatalytic approach, utilizing a hydrogen-bonding bifunctional squaramide-based catalyst. The process enables precise synthesis of chiral polyheterotricyclic oxazolidines and 1,3-oxazinane derivatives, revealing intricate structures with incorporated chiral quaternary centers. Remarkably, this method delivers high yields and exceptional enantioselectivities and diastereoselectivities, achieving up to 99% yield, >20 : 1 dr, and >99% ee. [ABSTRACT FROM AUTHOR]

A palladium/chiral N,N'-disulfonyl bisimidazoline (Bim)-catalyzed asymmetric addition of arylboronic acids to isoquinoline-1,3,4-trione-derived ketimines is reported, leading to the generation of a series of functionalized isoquinoline-1,3(2H,4H)-diones bearing one quaternary carbon-amino functionality in good to excellent yields with ≥95% ee in most cases. The reaction has remarkable compatibility with both substrate scopes, providing a highly enantioselective entry to chiral heterocyclic a-tertiary amines. [ABSTRACT FROM AUTHOR]

Isatin-derived Schiff bases are the subject of many studies, finding wide application areas in polymer technology, pharmaceutical industry, and medicine. In this study, a series of new Schiff bases were prepared from monothiocarbohydrazones based on isatins with different substituents (5-F, 5-Br, 5-I, and 5-MeO). The chemical structures of the synthesized compounds were determined using 1H NMR, 13C NMR, FTIR spectroscopic techniques, and elemental analysis. Antioxidant activity determinations of 23 compounds were performed using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical quenching method. The highest percent inhibition value at 10 µM concentration was shown by compound number 22, 5-bromoisatin Schiff base containing 3-methoxy-4-hydroxy group. Compound 17, a 5-iodoisatin Schiff base containing 3-methoxy-4-hydroxy group, showed the highest antioxidant activity with an IC50 value of 9.76 ± 0.03 µM. In addition to the theoretical analysis of the compounds, both their spectroscopic and antioxidant properties were investigated. The ground-state geometries and some chemical reactivity parameters of the compounds were calculated using the B3LYP/6-311 + + G(2d,2p) approach. Besides intramolecular interactions, substituent effects, and some QTAIM parameters, the calculations were also performed to study the electronic properties of reactive N/O–H bonds and were used to interpret the experimental results. The effects of the electronic parameters and intramolecular interactions of reactive N/O–H bonds on the antioxidant properties of the compounds were investigated. Additionally, the relationships of DPPH reactions with delocalization indices of N/O-H bonds and the pattern of SET/HAT mechanisms with electronic variables were analyzed. Examination of electron and hydrogen atom transfer mechanisms has shown the dominance of electron transfer, supported by the correlation coefficients between IC50 values and SET reaction energies. [ABSTRACT FROM AUTHOR]

Continuing our investigation of catalytic oxo/imido heterometathesis as novel water‐free method for C=N bond construction, we report here the application of classical transition metal oxides dispersed on silica (MOx/SiO2, M=V, Mo, W) as cheap, robust and readily available alternative to the catalysts prepared via Surface Organometallic Chemistry (SOMC). The oxide materials demonstrated activity in heterometathetical imidation of ketones, WO3/SiO2 being the most efficient. We also describe a new well‐defined supported W imido complex (≡SiO)W(=NMes)2(Me2Pyr) (Mes=2,4,6‐Me3C6H2, Me2Pyr=2,5‐dimethylpyrrolyl) and characterize it with SOMC protocols, which allowed us to identify the position of W on the oxo/imido heterometathesis activity scale (Mo

We have revisited the imine-anion-mediated Smiles rearrangement for the synthesis of ortho -hydroxyphenyl arylketimines. Detailed examinations revealed that migration of various aromatic groups, previously considered to be unsuited to SN Ar-type reactions, such as electron-rich or sterically hindered aromatic groups, can be accomplished by introducing bulky 9-anthryllithium as a nucleophile. Among the aromatic groups examined, naphthyl groups (1- and 2-naphthyl groups) exhibited an excellent performance, and their migration ability was well illustrated by the reaction with less bulky nucleophiles. [ABSTRACT FROM AUTHOR]

We reported palladium-catalyzed regioselective [3+2] cycloadditions of α,β-unsaturated imines with vinylethylene carbonates, providing the desired oxazolidines in moderate-to-high yields. This reaction provides a facile route for the highly regioselective synthesis of functional oxazolidines. The synthetic utility of the current method was also demonstrated by a gram-scale reaction. [ABSTRACT FROM AUTHOR]

A new and efficient strategy for the stereoselective synthesis of tetrahydropyridino- and deazepanopyrrolo[1,2- c ]imidazolidines has been developed. Annulation of acylethynylpyrroles with six- and seven-membered cyclic imines (MeCN/THF, 20–25 °C, 24–72 h) leads to tetrahydropyrrolo[1′,2′:3,4]imidazo[1,2- a ]pyridines and hexahydropyrrolo[1′,2′:3,4]imidazo[1,2- a ]azepines with (E)-acylethenyl moiety in 28–96% yields. [ABSTRACT FROM AUTHOR]

Given the tremendous success of (p‐cymene)RuII‐catalyzed C−H activation over the past 20 years, the community has long been aware that the development of chiral η6‐benzene (Ben) ligands should be a potent strategy for achieving the attractive but incredibly underdeveloped ruthenium(II)‐catalyzed asymmetric C−H activation. However, it has rarely been achieved due to the severe difficulty in developing proper chiral Ben ligands. In particular, designing chiral Ben ligands by connecting a benzene fragment to a chiral framework including benzene rings remained an unsolved challenge until this effort. Here we present a novel class of axially chiral Ben ligands derived from readily available (S)‐5,5′,6,6′,7,7′,8,8′‐octahydro‐1,1′‐bi‐2‐naphthol ((S)‐H8‐BINOL) in 4–8 steps. Notably, when coordinated with ruthenium, such chiral Ben ligand containing three benzene rings only forms one of the three possible isomeric BenRuII complexes. The related chiral BenRuII catalysts could effectively catalyze the asymmetric C−H activation of N‐sulfonyl ketimines with alkynes, affording a range of chiral spirocyclic sultams in up to 99 % yield with up to >99 % ee. These catalysts are expected to find broad applications in future. [ABSTRACT FROM AUTHOR]

A regio‐ and stereoselective stepwise (4+2) annulation of N‐propargylamides and α,β‐unsaturated imines/ketones has been accomplished with synergetic catalysis by a combination of a gold‐complex and a chiral quinine‐derived squaramide (QN‐SQA), leading to highly functionalized chiral tetrahydropyridines/dihydropyrans in good to high yields with generally excellent enantioselectivity. Mechanistic studies and DFT calculations indicate that the in situ formed alkylgold species is the key intermediate in this transformation, and the amide group served as a traceless directing group in this highly selective transformation. This method complements the enantioselective (4+2) annulation of allene reagents, providing the formal internal C−C π‐bond cycloaddition products, which is challenging and remains elusive. [ABSTRACT FROM AUTHOR]

A carbonyl‐assisted asymmetric 1,2‐migratory allylation through in situ generation of vicinal tetrasubstituted stereocenters is reported to access enantiopure α‐amino ketones and amino alcohols with excellent yields and diastereoselectivities. In a remarkable divergence, despite higher steric hindrance, the allylation exclusively occurs on ketones over imines in the first step, followed by a face‐selective 1,2‐allyl transfer, thus highlighting an exciting interplay between two distinct electrophiles. The methodology distinguishes itself through its adaptability to gram‐scale synthesis, showcasing broad functional‐group tolerance and stereodivergence. Density functional theory (DFT) analysis led to a deeper understanding of its selectivity and mechanistic framework. Highlighting its transformative potential, the method was applied to the total synthesis of hapalindole alkaloids. [ABSTRACT FROM AUTHOR]

We report an efficient [3+2] cycloaddition protocol for the synthesis of pyrazolo[1,2‐a]pyrazolones from Morita‐Baylis‐Hillman adducts and N,N'‐cyclic azomethine imines. The R‐BINOL chiral phosphoric acid was identified as the suitable catalyst for the reported cycloaddition protocol. Almost all MBH adducts regioselectively delivered 7‐oxo‐pyrazolo[1,2‐a]pyrazoles at an efficient yield of 69–91 %. With exception, the MBH adducts derived from acrylonitrile deliver 5‐oxo‐pyrazolo[1,2‐a]pyrazoles comparatively at a higher yield than the 7‐oxo‐pyrazolo[1,2‐a]pyrazoles. The density functional theory (DFT) studies demonstrate that the reaction is thermodynamically more feasible in the presence of R‐BINOL chiral phosphoric acid. [ABSTRACT FROM AUTHOR]

Epoxy thermosets are indispensable in various industrial applications due to their exceptional material properties. However, their limited recyclability poses a significant challenge for sustainability. To address this issue, integrating recyclable imine moieties into epoxy systems has emerged as a promising strategy. Despite recent advancements, challenges persist concerning the hydrolytic stability of imine‐based epoxy thermosets and the formation of irregular oligomeric structures upon depolymerization. In this study, these shortcomings are solved by designing a liquid imine monomer with secondary amine functionalities, which is subsequently reacted with commercially available epoxy monomers to produce high‐performance epoxy thermosets. Remarkably, the developed imine‐based epoxy system shows no sign of hydrolysis even under high‐temperature aqueous conditions, underscoring its potential for various industrial applications. Only the treatment with aqueous HCl results in the selective formation of exclusively well‐defined molecules, in high isolated yields after depolymerization. Crosslinking these building blocks once again yields recycled polymers with properties identical to pristine material. Moreover, it is discovered that, despite the crosslinked nature of the epoxy thermoset, the complete dissolution of the intact polymer in dichloromethane allowed for simple solvent‐based recycling. Through design on the molecular level, the recycling of imine‐based epoxy polymers is achieved via chemical and solvent‐based techniques. [ABSTRACT FROM AUTHOR]

With phenacyl chlorides as simple nucleophilic species, the asymmetric Darzens reaction of isatins using Ni(acac)2 as the Lewis acid and imidazolidine‐pyrroloimidazolone pyridine as the ligand is reported. In the presence of 1 mol% of the catalyst, diverse spiro‐epoxyoxindoles with two new contiguous stereocenters were afforded in 82–99% yields, >20:1 dr, with 91–99% ee. Chiral spiro‐epoxyoxindoles could undergo ring‐opening reactions in further transformations. The developed method was applied to the derivatization of complex molecules including indomethacin, gemfibrozil, and febuxostat‐derived α‐chloroketones. A strong positive nonlinear effect was observed, which was caused by the precipitation of a less‐soluble racemic catalyst complex. [ABSTRACT FROM AUTHOR]

Catalyst-free annulations of 2-(4H-benzo[d][1,3]oxazin-4-yl)acrylates have been successfully achieved under mild conditions. Specifically, the reaction of 2-(4H-benzo[d][1,3]oxazin-4-yl)acrylates with sulfur ylides furnished various 1,2-dihydroquinolines in generally high yields. Furthermore, [3+2]-annulations of 2-(4H-benzo[d][1,3]oxazin-4-yl)acrylates with α,β-unsaturated imines afforded a broad scope of polysubstituted 2,3-dihydropyrroles with high efficiency. [ABSTRACT FROM AUTHOR]

In the presence of ethanol solvent and glacial acetic acids, triazole reacted with different aromatic aldehydes such as 4-methoxybenzaldehyde, 4-hydroxybenzaldehyde, and benzaldehyde to form the imines group known as Schiff bases. Triazole Schiff bases are triazole hydrazone and their derivatives, VA, VB, and VC. The structures of these synthetic triazole hydrazone derivatives were characterized by means of FT-IR and mass spectrometry. The purities and quality of the compounds were evaluated using TLC. It was established, that the active ingredient in the synthesised triazole hydrazone was more effective against the infections than cefuroxime. [ABSTRACT FROM AUTHOR]

A well‐behaved dynamic library composed of two imines and corresponding amines was subjected to the action of an activated carboxylic acid (ACA), whose decarboxylation is known to be base promoted, in different solvents, namely CD2Cl2, CD3CN, and mixtures of them. Two non‐equilibrium systems are consequently obtained: i) a dissipative (CD2Cl2) and ii) an out‐of‐equilibrium (CD3CN) dynamic library whose composition goes back to equilibrium after a given time. In the former case, the library is fully coupled with the decarboxylation of the ACA, while in the latter, an energy ratchet operates. In the mixed solvents, the library exhibits a mediated behavior. Interestingly, in the presence of an excess of added ACA, the different behavior of the imine library in the two solvents is expected to manifest only when the excess acid is consumed. [ABSTRACT FROM AUTHOR]

Syntheses of (partially) aromatic nitrogen heterocycles increasingly rely on transition‐metal catalyzed C−C‐ and C−N‐cross‐coupling reactions. Here we describe a different approach to the synthesis of indolines by a domino C(sp3)−H activation, 1,2‐addition, and defluorinative SNAr‐cyclization sequence to provide the target 1,2‐diarylindolines (1,2‐diaryl‐2,3‐dihydroindoles) from ortho‐fluorinated methyl‐arenes and N‐aryl imines (benzylidene anilines) in a cyclocondensation that is mediated by potassium hexamethyldisilazide (KHMDS) as base exclusively. This transition‐metal‐free process via C−H and C−F bond activation provides a one‐step entry into a wide array of indoline scaffolds (43 examples, up to 96 % yield). This privileged substructure is common in natural products and pharmaceuticals alike, and cannot be accessed by traditional condensation reactions. [ABSTRACT FROM AUTHOR]

Herein, an environmentally friendly and efficient amidation method of imines by Oxone and CuO has been developed. This facile method shows excellent selectivity without affecting other functional groups such as phenyls, halogens, cyans, esters or heterocycles. This method features a broad substrate scope, mild conditions and high yields (≤90 %), and the yield in the gram scale experiment also reaches up to 81 %. Flonicamid, moclobemide and bupivacaine are also successfully synthesized to demonstrate its potential utilities. [ABSTRACT FROM AUTHOR]

A general and useful palladium‐catalyzed [4 + 2] cycloaddition of sulfamate‐derived cyclic imines with γ‐methylidene‐δ‐valerolactones (or 2‐methylidenetrimethylene carbonate) is described. The developed strategy generated diverse sulfamate‐fused piperidine derivatives (or sulfamate‐fused 1,3‐oxazinane rings) in good yields. [ABSTRACT FROM AUTHOR]

The present personalized account summarizes various cyclization reactions, including multicomponent and domino processes, which are directed towards the synthesis of complex heterocyclic products. Domino Knoevenagel/hetero‐Diels‐Alder reactions provide a synthesis of annulated quinol‐2‐ones. The combination of Knoevenagel reactions with [3+2] cycloadditions of nitrogen ylides afford complex spiroheteriocyclic products. Domino Knoevenagel/enamine cyclization reactions result in the formation of condensed purine analogues. Formal [3+3] cyclizations of pyridinium salts allow for a rapid assembly of bridged heterocyclic systems and include the employment of thioxindoles and cyclohexane‐1,3‐diones as dinucleophilic building blocks. The formal [3+3] cyclization of thioxindoles with fluoroaroyl chlorides, such as 2‐fluorobenzoyl chlorides and 2‐chloropyridine‐3‐carboxylic chloride, give rise to the synthesis of condensed benzothiophenes. The cyclization of heterocyclic enamines with diimines and triazines afford various purine analogues by domino [4+2]/retro [4+2] reactions. The formal [3+3] cyclization of 2,4,6‐tris(trifluoromethyl)‐1,3,5‐triazine with 1,3‐bis(silyloxy)‐1,3‐butadienes afford, depending on the conditions, 2,6‐bis(trifluoromethy)pyrid‐4‐ones or triazaadamantanone derivatives. Heating of 2‐ethynylpyridines with electron‐rich dienes afforded 2‐(2‐methoxyphenyl)pyridines by a domino [4+2]/retro [4+2] process. The reaction of 2‐ethynylpyridines with enones afforded indolizines by a formal [3+3] cyclization. The reaction of trifluoromethyl‐substituted 1,3‐diketones with lithiated alkynes afforded 3‐hydroxy‐pent‐4‐yn‐1‐ones. Formal [5+1] cyclization of the latter with urea afforded trifluoromethyl‐substituted pyridines. The Pd catalyzed formal [3+2] cyclizations of 2,3‐dihalopyridines with imines afforded a series of regioisomeric 4‐ and 7‐azaindoles. [ABSTRACT FROM AUTHOR]

A combined computational and experimental approach allowed us to develop overall the most selective catalyst for the direct hydrogenation of N‐methyl, N‐alkyl and N‐aryl imines described to date. Iridium catalysts with a cyclometallated cyclic imide group provide selectivity of up to 99 % enantiomeric excess. Computational studies show that the selectivity results from the combined effect of H‐bonding of the imide C=O with the substrate iminium ion and a stabilizing π–π interaction with the cyclometallated ligand. The cyclometallated ligand thus exhibits a unique mode of action, serving as a template for the H‐bond directed approach of the substrate which results in enhanced selectivity. The catalyst (2) has been synthesized and isolated as a crystalline air‐stable solid. X‐ray analysis of 2 confirmed the structure of the catalyst and the correct position of the imide C=O groups to engage in an H‐bond with the substrate. 19F NMR real‐time monitoring showed the hydrogenation of N‐methyl imines catalyzed by 2 is very fast, with a TOF of approx. 3500 h−1. [ABSTRACT FROM AUTHOR]

Herein, we disclose an eco-efficient redox-neutral iron-catalyzed decarboxylative radical addition to chiral azomethine imines upon visible light (427 nm) giving cyclic hydrazine derivatives with dr ranging from 82 : 18 to >96 : 4. This earth-abundant metal promoted sequence proceeds efficiently under ligand-free conditions based on a LMCT process and opens a route to new chiral heterocycles. [ABSTRACT FROM AUTHOR]

We present herein the synthesis, characterization and complexation of ferrocenyl‐substituted MIIs (mesoionic imines) and their metal complexes. In the free MIIs, strong hydrogen bonding interactions are observed between the imine‐N and the C−H bonds of the ferrocenyl substituents both in the solid state and in solution. The influence of this hydrogen bonding is so strong that complexation of the MIIs with [IrCp*Cl2]2 yields unique six‐membered iridacycles via C−H‐activation of the corresponding C−H‐site at the Fc‐substituent and not the Ph‐substituent. This result is in contrast to previous reports in which always a preferential C−H activation at the phenyl substituent is observed in competitive reactions in the presence of ferrocenyl substituents. The corresponding Ir complexes formed after in‐situ halide exchange reaction exist in either [Ir−I] contact or as [Ir]+I− solvent separated ion‐pairs depending on the solvent polarity. The iodide coordinated and solvent separated ion‐pairs display drastically different physical properties. The TEP (Tolman‐electronic‐parameter) of these ligands was determined and lines up with previously reported MII‐ligands. The redox properties were investigated by a combination of electrochemical and spectroelectrochemical methods. We show here how non‐covalent interactions can have a drastic influence on the physical and chemical properties of these new class of compounds. [ABSTRACT FROM AUTHOR]

An iron‐catalyzed protocol for the synthesis of 3‐amino‐3‐aminomethyl‐2‐oxindole heterocyclic structures is disclosed employing isatins and non‐nucleophilic N‐methoxybenzamides. This reaction class is associated with broad scope and tolerates numerous functionalities, such as fluoro, chloro, bromo, iodo, trifluoromethyl, nitrile, ester, ether, and alkenyl, including heteroaryl – thiophene, benzothiophene, carbazolyl, indolyl, eugenol, and polycyclic cholesterol moieties. Detailed mechanistic investigations reveal that the reaction proceeds via iron‐catalyzed N−O bond cleavage in N‐methoxybenzamides, generating formaldehyde and benzamide, and through the intermediacy of isatin‐ketimines and N‐(hydroxymethyl)benzamides. Overall, this amidation reaction involves one C−C and two C−N bond‐forming tandem processes, providing a range of β‐amino‐aminomethyl‐oxindoles (45 examples) in up to 88% yields. [ABSTRACT FROM AUTHOR]

Arylation of ketimines is the most straightforward strategy for constructing chiral α‐tertiary amines, important structural motifs found in natural products and biologically active compounds. This comprehensive review highlights the achievements in the transition metal‐catalyzed and organocatalyzed asymmetric arylations of ketimines from the seminal report published in 2010 till November 2023. The review is divided into three chapters: (1) Arylation of diaryl ketimines, (2) Arylation of aryl‐alkyl and aryl‐acyl ketimines, and (3) Arylation of acyl‐alkyl and dialkyl ketimines. Each chapter is further divided into transition metal‐catalyzed reactions (grouped by individual metals) and organocatalyzed reactions. The covered literature includes emphasis on the advantages of the reported methodology, its scope and limitations, and the description of the transition state (where applicable). [ABSTRACT FROM AUTHOR]

Selective synthesis of primary amines from nitriles is challenging in synthetic chemistry due to the possible en‐route generation of various amines and imines. Herein, we report a practical and operationally simple MOtBu‐mediated (M=Na, K) transfer hydrogenation of nitriles to the corresponding primary amines with a relatively unexplored sacrificial hydrogen source (dimethylamine borane). The strategy encompasses a broad substrate scope under transition metal‐free conditions and does not require any solvent. The mechanistic investigation was performed with the aid of control experiments and spectroscopic studies. The GC analysis of the reaction mixture exhibited the evolution of the H2 gas. Additionally, detailed computational calculations were undertaken to shed light on the possible intermediates and transition states involved during the present protocol. [ABSTRACT FROM AUTHOR]

This study presents the synthesis of a novel series of imine derivatives derived from imidazo[1,2‐a]pyridine as potential therapeutic agents. The imines were obtained by condensing 2‐(4‐bromophenyl)‐6‐chloroimidazo[1,2‐a]pyridine‐3‐carbaldehyde with primary amines, leading to high‐purity products that were characterized using various spectroscopic techniques. The compounds demonstrated promising in vitro antimicrobial activity against various bacteria, including Staphylococcus aureus and Escherichia coli, as well as fungi, such as Candida albicans, Saccharomyces cerevisiae, and Aspergillus brasiliensis. Furthermore, the antioxidant properties of the imine derivatives were evaluated using DPPH and ABTS techniques, and the IC50 values measured revealed their ability to scavenge free radicals. Overall, this study provides a valuable contribution to the field of pharmacology by synthesizing a new series of imine derivatives with significant potential as new therapeutic agents, exhibiting both antimicrobial and antioxidant properties. [ABSTRACT FROM AUTHOR]

Quinone imines are important derivatives of quinones with a wide range of applications in organic synthesis and the pharmaceutical industry. The attack of nucleophilic reagents on quinone imines tends to lead to aromatization of the quinone skeleton, resulting in both the high reactivity and the unique reactivity of quinone imines. The extreme value of quinone imines in the construction of nitrogen- or oxygen-containing heterocycles has attracted widespread attention, and remarkable advances have been reported recently. This review provides an overview of the application of quinone imines in the synthesis of cyclic compounds via the domino annulation reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • The WO 3 decorated with Cu was developed to efficiently regulate O 2 active species. • Under irradiation of wavelength < 475 nm, O 2 tends to produce 1O 2 and •O. • Under irradiation with a long wavelength source (>475 nm), 1O 2 is mainly ROS. • Cu@CuO x /WO 3 with photo-regulated ROS generation exhibits excellent performance. Photocatalysts can absorb light and activate molecular O 2 under mild conditions, but the generation of unsuitable reactive oxygen species often limits their use in synthesizing fine chemicals. To address this issue, we disperse 1 wt% copper on tungsten trioxide (WO 3) support to create an efficient catalyst for selective oxidative coupling of aromatic amines to imines under sunlight irradiation at room temperature. Copper consists of a metallic copper core and an oxide shell. Experimental and density functional theory calculations have confirmed that Cu 2 O is the primary activation site. Under λ < 475 nm, the light excites electrons of the valence bands in Cu 2 O and WO 3 , which activate O 2 to superoxide radical •O 2 −. Then rapidly transforms into oxygen adatoms (•O) and oxygen anion radicals (•O−) species on the surface of Cu 2 O. Simultaneously, it is captured by holes in the WO 3 valence band to generate singlet oxygen (1O 2). •O bind to 1O 2 promoting the coupling reaction of amines. When λ > 475 nm, intense light absorption due to the localized surface plasmon resonance excites numerous electrons in Cu to promote the oxidative coupling with the adsorbed O 2. This study presents a promising approach towards the design of high-performance photocatalysts for solar energy conversion and environmentally-friendly oxidative organic synthesis. [ABSTRACT FROM AUTHOR]

Imines are certainly important constituents of many biomolecules, pharmaceuticals, agrochemicals, and fine chemicals. This review article highlights the standard protocols reported so far for the selective synthesis of imines via catalyzed and non-catalyzed (i) oxidative coupling of primary amines and (ii) oxidation of secondary amines in the presence of some competent/resourceful oxidants other than molecular O2 such as tert-butyl hydroperoxide (TBHP), H2O2, hypervalent iodines, persulfate, hypochlorite, electroactive species and graphene oxide. Indeed, the use of such oxidants offers a cost-effective experimental set-up, operational simplicity and also minimization of by-products. The cooperativity between catalyst, amine substrate, and oxidant is discussed in this review to understand the proposed mechanisms. Three consolidated data tables (Table 1, 2 & 3) are prepared to provide the summary of optimized reaction conditions (type of catalyst, type of oxidant, choice of solvent, amine-to-oxidant ratio, reaction time/temperature, conversion of amine, yield/selectivity of imine) of each article published to have a comparison. [ABSTRACT FROM AUTHOR]

Chiral carboxylic acid production from renewable biomass by chemocatalysis is vitally important for reducing our carbon footprint, but remains underdeveloped. We herein establish a strategy that make use of a stereogenic center of biomass to achieve a rare example of D‐glyceric acid production with the highest yield (86.8 %) reported to date as well as an excellent ee value (>99 %). Unlike traditional asymmetric catalysis, chiral catalysts/additives are not required. Ample experiments combined with quantum chemical calculations established the origins of the stereogenic center and catalyst performance. The chirality at C4 in D‐xylose was proved to be retained and successfully delivered to C2 in D‐glyceric acid during C−C cleavage. The remarkable cooperative‐roles of Ag+ and Ag0 in the constructed Ag/γ‐Al2O3 catalyst are disclosed as the crucial contributors. Ag+ was responsible for low‐temperature activation of D‐xylose, while Ag0 facilitated the generation of active O* from O2. Ag+ and active O* cooperatively promoted the precise cleavage of the C2−C3 bond, and more importantly O* allowed the immediate fast oxidization of the D‐glyceraldehyde intermediate to stabilize D‐glyceric acid, thereby inhibiting the side reaction that induced racemization. This strategy makes a significant breakthrough in overcoming the limitation of poor enantioselectivity in current chemocatalytic conversion of biomass. [ABSTRACT FROM AUTHOR]

A direct catalytic stereoselective synthesis of C4' functionalized furanoside and nucleoside derivatives with a tetrasubstituted stereocenter is disclosed. The amine‐catalyzed stereoselective α‐aminomethylation reactions on furanoside‐derived aldehyde derivatives gave the corresponding C4' functionalized D‐ or L‐ribose derivatives in good to excellent yields (67−94%) with up to >20:1 dr. [ABSTRACT FROM AUTHOR]

Bond activation and catalysis using s‐block metals are of great significance. Herein, a series of calcium pincer complexes with deprotonated side arms have been prepared using pyridine‐based PNP and PNN ligands. The complexes were characterized by NMR and X‐ray crystal diffraction. Utilizing the obtained calcium complexes, unprecedented N2O activation by metal‐ligand cooperation (MLC) involving dearomatization‐aromatization of the pyridine ligand was achieved, generating aromatized calcium diazotate complexes as products. Additionally, the dearomatized calcium complexes were able to activate the N−H bond as well as reversibly activate H2, offering an opportunity for the catalytic hydrogenation of various unsaturated molecules. DFT calculations were applied to analyze the electronic structures of the synthesized complexes and explore possible reaction mechanisms. This study is an important complement to the area of MLC and main‐group metal chemistry. [ABSTRACT FROM AUTHOR]

The dehydrogenation adjacent to an electron-withdrawing group provides an efficient access to α,β-unsaturated compounds that serving as versatile synthons in organic chemistry. However, the α,β-desaturation of aliphatic imines has hitherto proven to be challenging due to easy hydrolysis and preferential dimerization. Herein, by employing a pre-fluorination and palladium-catalyzed dehydrogenation reaction sequence, the abundant simple aliphatic amides are amendable to the rapid construction of complex molecular architectures to produce α,β-unsaturated imines. Mechanistic investigations reveal a Pd(0)/Pd(II) catalytic cycle involving oxidative H–F elimination of N-fluoroamide followed by a smooth α,β-desaturation of the in-situ generated aliphatic imine intermediate. This protocol exhibits excellent functional group tolerance, and even the carbonyl groups are compatible without any competing dehydrogenation, allowing for late-stage functionalization of complex bioactive molecules. The synthetic utility of this transformation has been further demonstrated by a diversity-oriented derivatization and a concise formal synthesis of (±)-alloyohimbane. α,β-unsaturated compounds serve as versatile synthons in organic chemistry, but the α,β-desaturation of aliphatic imines is challenging due to easy hydrolysis and preferential dimerization. Herein, the authors report the synthesis of α,β-unsaturated imines by employing a pre-fluorination and palladium-catalyzed dehydrogenation reaction sequence. [ABSTRACT FROM AUTHOR]

New chiral ligands could be obtained by introducing proline moieties and imidazoline moieties to binaphthyl skeletons. The chiral ligands exhibited balanced rigidity and flexibility which could allow the change of the conformations during the reactions on one hand, and could provide sufficient asymmetric induction on the other. The proline moiety could act as a linker connecting the binaphthyl skeletons and the imidazoline moieties as well as a coordinating group for the central metal, and the electronic and steric properties of the imidazoline groups could be carefully fine‐tuned by the use of different substituents. In the presence of Cu(II) catalyst bearing such chiral ligands, aza‐Friedel–Crafts reaction of 1‐naphthols and electron‐rich phenols with isatin‐derived ketimines provided the desired products with good to excellent yields and up to 99 % ee. The reactions showed good scalability, and excellent ee could still be obtained when the reaction was carried out in gram‐scale. [ABSTRACT FROM AUTHOR]

Thioglycoside bond formation via an asymmetric sulfa-Michael/aldol reaction of (E)-β-nucleobase acrylketones and 1,4-dithiane-2,5-diol has been achieved with a cinchona alkaloid-derived bifunctional squaramide chiral catalyst. Diverse purine, benzimidazole, and imidazole substrates are well tolerated and generate 40-thionucleoside derivatives containing three contiguous stereogenic centers with excellent results (30 examples, up to 97% yield, 420: 1 dr and up to 99% ee). Moreover, the novel strategy provides an efficient and convenient synthetic route to construct chiral 40-thionucleosides. [ABSTRACT FROM AUTHOR]

A sequential rhodium(III)-catalyzed spiroannulation and lactonization strategy has been developed for the synthesis of a highly rigid spirobenzosultam lactones in good yields with high regioselectivity by means of aromatic ortho-C–H bond activation/functionalization of 3-aryl N-sulfonyl ketimines with 4-hydroxy-2-alkynoates. The reaction proceeds through a cascade of C–H activation followed by spiroannulation and lactonization. In this approach, two C–C and C–O bonds are formed in a single step. This is the first report on the spiroannulation of cyclic N-sulfonyl ketimines with hydroxyalkynoates. [ABSTRACT FROM AUTHOR]

'Transient' C−H functionalization has emerged in recent years to describe the use of a dynamic linkage, often an imine, to direct cyclometallation and subsequent functionalization. As the field continues to grow in popularity, we consider the features that make an imine directing group transient. A transient imine should be i) formed dynamically in situ, ii) avoid discrete introduction or cleavage steps, and iii) offer the potential for catalysis in both the directing group and metal. This concept article contrasts transient imines with pioneering early studies of imines as directing groups for the formation of metallacycles and the use of preformed imines in C−H functionalization. Leading developments in the use of catalytic additives to form transient directing groups (as aldehyde or amine) are covered including selected highlights of the most recent examples of catalytic imine directed C−H functionalization with transition metals. [ABSTRACT FROM AUTHOR]

Data on the synthesis methods, chemical transformations, and biological activity of 4H-3,1-benzoxazines and their dihydro derivatives, including coordination compounds of the dihydro derivatives with transition metals, are systematized and analyzed. [ABSTRACT FROM AUTHOR]

Chiral cyclohexenylallenes are readily accessed from 1‐enynes, aldehydes and chiral secondary amines in good yields (up to 79 % yield) with excellent enantioselectivities (up to 99 % ee), through CuI catalyzed the formation of chiral propargylamine intermediates. Subsequent Yb(OTf)3 catalyzed [4+2] cycloaddition reaction of cyclohexylallenes with the dienophiles tetracyanoethylene and diethyl acetylenedicarboxylate afforded the corresponding bicyclic products in 69–75 % yield and 84–90 % ee. [ABSTRACT FROM AUTHOR]

Abstract: Herein, we report the first total synthesis of (±)-marilines B and C, as well as a failed approach to (±)-mariline A, by using our recently developed multicomponent reaction method, which involves the interception of ortho-quinone methides with various nitrogen nucleophiles to allow easy assembly of various benzylic amine cores with diverse substituents.

Abstract Schiff bases are a diverse group of organic compounds with great pharmaceutical importance due to the presence of carbon–nitrogen double bonds (–C=N–). These compounds are synthesized by the condensation reaction between a primary amine and an aldehyde or ketone in a suitable solvent such as methanol. These compounds have shown antibacterial, antifungal, antiviral, anti-inflammatory, and antioxidant activities, which have garnered the attention of organic chemists in synthesizing these compounds. Recent advances have been summarized in this review paper mainly including compounds with potential antibacterial, antifungal, and antiviral activities. Synthetic schemes are included to provide a better understanding of the Schiff base synthesis mechanism. This review paper will provide a way forward for the pharmaceutical chemist to synthesize new compounds with potential biological activities. Graphical abstract

[Display omitted] The alkylation of cyclic five-membered azomethine imines with carboxylic acids proceeds under irradiation with 400 nm light using a dual catalytic system consisting of 9-arylacridine and tetrabutylammonium decatungstate. Azomethine imines containing aromatic, heterocyclic and aliphatic groups are suitable for the process providing pyrazolidin-3-ones in 42–98% yields. [ABSTRACT FROM AUTHOR]

Geminal bis(boronates) are versatile synthetic building blocks in organic chemistry. The fact that they predominantly serve as nucleophiles in the previous reports, however, has restrained their synthetic potential. Herein we disclose the ambiphilic reactivity of α‐halogenated geminal bis(boronates), of which the first catalytic utilization was accomplished by merging a formal Heck cross‐coupling with a highly diastereoselective allylboration of aldehydes or imines, providing a new avenue for rapid assembly of polyfunctionalized boron‐containing compounds. We demonstrated that this cascade reaction is highly efficient and compatible with various functional groups, and a wide range of heterocycles. In contrast to a classical Pd(0/II) scenario, mechanistic experiments and DFT calculations have provided strong evidence for a catalytic cycle involving Pd(I)/diboryl carbon radical intermediates. [ABSTRACT FROM AUTHOR]

Herein we describe a sustainable and efficient photocatalytic method for the stereoselective radical alkylation of chiral sulfinyl imines. By employing readily available non‐prefunctionalized radical precursors and the cost‐effective TBADT as a direct HAT photocatalyst, we successfully obtain diverse chiral amines with high yields and excellent diastereoselectivity under mild conditions. This method provides an efficient approach for accessing a diverse array of medicinally relevant compounds, including both natural and synthetic α‐amino acids, aryl ethyl amines, and other structural motifs commonly found in approved pharmaceuticals and natural product. [ABSTRACT FROM AUTHOR]

Enantioselective access to polycyclic tetrahydroxanthone compounds was achieved through an organocatalyzed cascade reaction of alkene‐substituted 1,3‐diketones and alkenyloxindoles, using quinine‐derived squaramide as an efficient catalyst. It afforded a variety of optically active spirooxindole‐based tetrahydroxanthones with 18–94% yields, >19:1 dr, and 86–99% ee. [ABSTRACT FROM AUTHOR]