Carbon Substituents Research Articles

Some Terminally Alkenyl-substituted Porphyrins: Synthesis and Attempts of Heck Reaction Leading to Porphyrin–Azulene Dyads

: The synthesis of meso-tetraphenylporphyrin derivatives, double functionalized in one of the phenyl rings (with a nitro group and carbon substituents), is described. 5-(4- Nitroaryl)-10,15,20-triarylporphyrinates react, in the presence of a base (t-BuOK), with carbanions containing a leaving group at the carbanionic center to give products of substitution of hydrogen at ortho-position to the nitro group via vicarious nucleophilic substitution scheme. Their alkylation with allyl bromide or 4-bromobut-1-en (t-BuOK/DMF, at 0-5°C) leads to porphyrins bearing side alkyl chain with a terminal double bond in yields of up to 82%. The above-mentioned double-substituted intermediates are very convenient substrates for Heck cross-coupling reaction. In this study, the synthesis of porphyrin–azulene dyads is reported. In some cases, the formation of highly conjugated systems is observed, with moderate yield. Their structures are interesting from both the porphyrin and azulene point of view.

Protection-Free, Two-step Synthesis of C5-C Functionalized Pyrimidine Nucleosides.

A simple, reliable, and efficient method for the gram-scale chemical synthesis of pyrimidine nucleosides functionalized with C5-carboxyl, nitrile, ester, amide, or amidine, starting from unprotected uridine and cytidine, is described. The protocol involves the synthesis of 5-trifluoromethyluridine and 5-trifluoromethylcytidine with Langlois reagent (CF3 SO2 Na) in the presence of tert-butyl hydroperoxide and subsequent transformation of the CF3 group to the C5-C 'carbon substituents' under alkaline conditions. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Synthesis and characterization of 5-trifluoromethyluridine (5-CF3 U) and 5-trifluoromethylcytidine (5-CF3 C) Basic Protocol 2: Conversion of 5-CF3 U and 5-CF3 C to several C5-substituted ribonucleosides.

Vinylidene rearrangements of internal borylalkynes via 1,2-boryl migration.

Vinylidene rearrangement of alkynes is a well-established and powerful method for alkyne transformations, while use of borylalkynes has remained largely unexplored. This paper describes vinylidene rearrangements of internal borylalkynes using a cationic ruthenium complex. This rearrangement is applicable to alkynes with both tri-(B(pin), B(dan)) and tetracoordinate (B(mida)) boryl groups, and the reaction rate is dramatically affected by the Lewis acidity of the boryl group. Mechanistic study revealed that the rearrangement proceeds via 1,2-boryl migration regardless of the coordination number of the boron center. The migration mode was elucidated by theoretical calculations to indicate that the migration of the tricoordinate boryl groups is an electrophilic process in contrast to the previous vinylidene rearrangements of internal alkynes with two carbon substituents.

Practical Asymmetric Synthesis of Sulfoximines and Sulfimides from Sulfinamides

AbstractChiral sulfoximines and sulfimides are an interesting class of compounds in various areas. However, methodologies for preparing these chiral sulfur compounds in a stereoselective manner have been underdeveloped. Herein, we briefly summarize our recent studies on asymmetric synthesis of sulfoximines and sulfimides from readily available enantioenriched sulfinamides. In these studies, optically pure sulfoximines and sulfimides having various carbon substituents on their sulfur atom could be obtained.1 Introduction2 Asymmetric Synthesis of Chiral Sulfoximines3 Asymmetric Synthesis of Chiral Sulfimides4 Conclusion

Target and nontarget analysis of per- and polyfluoroalkyl substances in surface water, groundwater and sediments of three typical fluorochemical industrial parks in China

The objectives of this study were to identify both legacy and emerging per- and polyfluoroalkyl substances (PFAS) from three typical fluoridated industrial parks (FIPs) in China, and to assess their environmental occurrence and fate. Complementary suspect target and nontarget screening were implemented, and a total of 111 emerging PFAS were identified. Based on the multi-mass scale analysis, 25 emerging PFAS were identified for the first time, including 24 per- and polyfluoroalkyl ether carboxylic acids (PFECAs) and 1 ultra-short chlorinated perfluoroalkyl carboxylic acids (Cl-PFCAs, C2), with a maximum percentage of 48.2 % in nontarget PFAS (exclude target PFAS). The composition of PFAS identified in different media was influenced by functional groups, carbon chain length, substituents and ether bond insertion, with poly-hydrogen substituted being preferably in water and a more diverse pattern of PFECAs in sediments. The patterns of PFAS homologs revealed distinct differences among the three typical FIPs in the shift of PFAS production patterns. The C4-PFAS and short-chain carboxylic acids (≤C6) were the main PFAS in the Fuxin and Changshu, respectively. In contrast, perfluorooctanoic acid (PFOA, C8) remained dominant in Zibo, and the highest point concentrations in water and sediment were up to 706 µg/L and 553 µg/g, respectively.

Asymmetric Catalytic Friedel-Crafts Reactions of Unactivated Arenes.

Since its discovery more than a century ago, the Friedel-Crafts reaction has manifested itself as a powerful method for the introduction of carbon substituents to arenes. Despite its potential generality, the scope of the reaction is intrinsically limited by the arene's nucleophilicity, which has previously restrained the applicability of asymmetric variants to activated substrates. To overcome this fundamental limitation, we report herein an asymmetric Friedel-Crafts reaction of unactivated, purely hydrocarbon arenes, alkoxybenzenes, and heteroarenes with N,O-acetals to give enantioenriched arylglycine esters. Highly regio- and stereoselective C-C bond formation was achieved using strong and confined Brønsted acid organocatalysts, enabling the first asymmetric catalytic Friedel-Crafts reaction of simple alkylbenzenes.

Catalytic enantioselective nucleophilic desymmetrization of phosphonate esters

Molecules that contain a stereogenic phosphorus atom are crucial to medicine, agrochemistry and catalysis. While methods are available for the selective construction of various chiral organophosphorus compounds, catalytic enantioselective approaches for their synthesis are far less common. Given the vastness of possible substituent combinations around a phosphorus atom, protocols for their preparation should also be divergent, providing facile access not only to one but to many classes of phosphorus compounds. Here we introduce a catalytic and enantioselective strategy for the preparation of an enantioenriched phosphorus(V) centre that can be diversified enantiospecifically to a wide range of biologically relevant phosphorus(V) compounds. The process, which involves an enantioselective nucleophilic substitution catalysed by a superbasic bifunctional iminophosphorane catalyst, can accommodate a wide range of carbon substituents at phosphorus. The resulting stable, yet versatile, synthetic intermediates can be combined with a multitude of medicinally relevant O-, N- and S-based nucleophiles.

Sydnone Methides: Intermediates between Mesoionic Compounds and Mesoionic N‐Heterocyclic Olefins

AbstractSydnone methides represent an almost unknown class of mesoionic compounds which possess exocyclic carbon substituents instead of oxygen (sydnones) or nitrogen (sydnone imines) in the 5‐position of a 1,2,3‐oxadiazolium ring. Unsubstituted 4‐positions give rise to the generation of anionic N‐heterocyclic carbenes by deprotonation. Preparations of new sydnone methides are described here. They can be represented by mesomeric structures with either exocyclic carbanionic groups like −C(CN)2−, −C(CN)(COOMe)−, −C(CN)(CONH2)−, and −C(CN)(SO2Me)−, or with the corresponding exocyclic C=C double bonds as a common feature with mesoionic N‐heterocyclic olefins. An X‐ray single structure analysis revealed a length of 140.7(3) pm of the exocyclic bond in the solid state. From the coalescence temperature (55 °C) determined by a series of 13C NMR experiments (150 MHz) at various temperatures, an energy of rotation of 18.5 Kcal/mol was calculated for this bond. The 13C NMR signals of the anionic N‐heterocyclic carbenes, from which the 2‐mesityl‐substituted anionic NHC proved to be stable up to 10 °C, are highly shifted upfield (δcarbene=157.9 ppm−160.5 ppm). The carbenes can be reacted in situ with elemental selenium and chlorophosphanes to yield sydnone methide selenoethers after methylation and 4‐phosphanylsydnone methides in good to excellent yields, respectively.

Asymmetric Synthesis of Chiral Sulfimides through the O-Alkylation of Enantioenriched Sulfinamides and Addition of Carbon Nucleophiles.

Chiral sulfimides, the aza-analogues of sulfoxides, are valuable compounds in organic synthesis and medicinal chemistry. Herein, we report an efficient method for preparing chiral sulfimides from easily available enantioenriched sulfinamides. The key step of this method is a stereospecific oxygen-selective alkylation of enantioenriched sulfinamides, which is accomplished by using isopropyl iodide, K2 CO3 , and DMPU. The resulting chiral sulfinimidate esters are transformed to chiral sulfimides by the nucleophilic addition of the Grignard reagents under simple conditions. This transformation enables access to the enantioenriched diaryl or dialkyl sulfimides bearing two similar carbon substituents, which are difficult to synthesize by previous methods.

Asymmetric Synthesis of Chiral Sulfimides through the O‐Alkylation of Enantioenriched Sulfinamides and Addition of Carbon Nucleophiles

AbstractChiral sulfimides, the aza‐analogues of sulfoxides, are valuable compounds in organic synthesis and medicinal chemistry. Herein, we report an efficient method for preparing chiral sulfimides from easily available enantioenriched sulfinamides. The key step of this method is a stereospecific oxygen‐selective alkylation of enantioenriched sulfinamides, which is accomplished by using isopropyl iodide, K2CO3, and DMPU. The resulting chiral sulfinimidate esters are transformed to chiral sulfimides by the nucleophilic addition of the Grignard reagents under simple conditions. This transformation enables access to the enantioenriched diaryl or dialkyl sulfimides bearing two similar carbon substituents, which are difficult to synthesize by previous methods.

Small Electron Polaron in Carbon-Doped Cubic Boron Nitride

Controllable and reliable doping of cubic boron nitride (cBN) is a critical challenge in its widespread application in power electronics. Recently, progress was made in this regard when an experiment reported successful n-doping of cBN with carbon, reaching carbon concentrations as high as 5%, which is beyond the thermodynamic solubility limit. However, the nature of carbon-based defects introduced within the cBN matrix remains unknown thus far. Here, we explore the electronic structure of carbon-doped cBN under nitrogen-rich conditions, which are conducive to the formation of donor-type defects (such as carbon substituents replacing boron), and predict several possible arrangements of carbon in clusters at experimentally relevant concentrations of 1.5–7.8%. Our theoretical calculations show that carbon dopants prefer to aggregate into small clusters with local ordering rather than distributing randomly in the bulk. Along with defects that result in easily ionizable defect states, we also report a distribution of carbon dopants, where the structure exhibits a defect-bound small electron polaron. The polaron can be identified via a split-off localized dopant band near the valence band edge. These findings not only shed light on identities of possible carbon-based defects but also predict additional carriers─defect-bound small polarons.

Iridium-catalyzed regioselective B(3,6)-dialkenylation or B(4)-alkenylation of o-carboranes via B-H activation and 1,2-carbon migration of alkynes.

An efficient Ir-catalyzed cage boron alkenylation of 1-(2'-picolyl)-o-carboranes with diarylacetylenes has been developed, leading to a wide variety of B-H geminal addition products via 1,2-carbon migration of alkynes. The steric effect of cage carbon substituents has a great impact on the regioselectivity of such alkenylation reactions.

Naturally Occurring Partially Reduced Perylenequinones from Fungi.

This Review provides a critical analysis of the literature covering the naturally occurring partially reduced perylenequinones (PQs) from fungi without carbon substituents (which can be named class A perylenequinones) and discusses their structures, stereochemistry, biosynthesis, and biological activities as appropriate. Perylenequinones are natural pigments with a perylene skeleton produced by certain fungi, aphids, some plants, and animal species. These compounds display several biological activities, e.g., antimicrobial, anti-HIV, photosensitizers, cytotoxic, and phytotoxic. It describes 36 fungal PQs and cites 81 references, covering from 1956 to August 2022.

Recognition and quantitative analysis for six phthalate esters (PAEs) through functionalized ZIF-67@Ag nanowires as surface-enhanced Raman scattering substrate

A novel surface enhanced Raman scattering (SERS) method was developed based on Ag nanowires embedded into functionalized metal–organic framework ZIF-67 (ZIF-67@Ag NWs) composite as substrate, which was applied for rapid recognition and sensitive detection of six PAEs. The Raman signals for PAEs detection were gained at ZIF-67@Ag NWs substrate mainly due to the “sharp tip effect” of rough Ag nanowires and excellent absorptive capacity of ZIF-67 to capture targeted molecules into the electromagnetic field. Different structural PAEs, including carbon chain lengths, isomers, and substituents, were evaluated for SERS performance and characteristic peaks under the optimal conditions. The SERS spectra proved that different PAEs exhibited some typically characteristic peaks in favor of recognizing and distinguishing them. The ZIF-67@Ag NWs as SERS substrate was successfully applied to detect six PAEs and exhibited wide linear ranges, low detection limit (LOD), excellent repeatability and stability (such as dibutyl phthalate DBP: linear range of 10−2 ∼ 10−12 mol/L, LOD 3 × 10−13 mol/L). The ZIF-67@Ag NWs substrate by SERS was implemented to determine trace DBP in plastics with satisfactory recoveries of 82.5 % ∼ 108.3 %. The proposed ZIF-67@Ag NWs substrate may provide an effective and promising SERS platform for recognition and quantitative determination of different structural PAEs in environment.

Mechanism-based ligand design for copper-catalysed enantioconvergent C(sp3)-C(sp) cross-coupling of tertiary electrophiles with alkynes.

In contrast with the well-established enantioconvergent radical C(sp3)-C cross-coupling of racemic secondary alkyl electrophiles, the corresponding coupling of tertiary electrophiles to forge all-carbon quaternary stereocentres remains underexplored. The major challenge arises from the steric hindrance and the difficult enantio-differentiation of three distinct carbon substituents of prochiral tertiary radicals. Here we demonstrate a general copper-catalysed enantioconvergent C(sp3)-C(sp) cross-coupling of diverse racemic tertiary alkyl halides with terminal alkynes (87 examples). Key to the success is the rational design of chiral anionic N,N,N-ligands tailor-made for the computationally predicted outer-sphere radical group transfer pathway. This protocol provides a practical platform for the construction of chiral C(sp3)-C(sp/sp2/sp3) bonds, allowing for expedient access to an array of synthetically challenging quaternary carbon building blocks of interest in organic synthesis and related areas.

Copper‐Catalyzed Chan‐Lam Coupling of NH‐Diaryl Sulfondiimines

AbstractSulfondiimines, which contain a tetrasubstituted sulfur centre bearing two nitrogens and two carbon substituents, are a class of underexplored scaffolds in organic chemistry. Fascinated by some unique yet intriguing properties, sulfondiimines appear as leads in discovery industry, but the lack of efficient synthetic approaches holds back their further uptake by medicinal chemistry. Herein, a general and practical copper‐catalyzed Chan‐Lam coupling of NH‐diaryl sulfondiimines with arylboronic acids is presented. A simple copper catalyst efficiently facilitated the highly chemoselective construction of C−N bond, allowing the preparation of a variety of N‐arylated diaryl sulfondiimines in good yields under mild and environmentally benign conditions. An array of protecting groups on imine moieties were well tolerated, offering diversified accesses to NH,NAr‐diaryl sulfondiimines, a class of versatile building blocks. Moreover, an aza‐analogue of an EphB4 inhibitor featuring a sulfondiimine‐based pharmacophore was generated employing our Chan‐Lam coupling as the key step.magnified image

Copper-catalysed asymmetric reductive cross-coupling of prochiral alkenes

Asymmetric construction of C(sp3)–C(sp3) bond with good stereocontrol of the two connecting carbon centres retaining all carbon or hydrogen substituents is a challenging target in transition metal catalysis. Transition metal-catalysed reductive coupling of unsaturated π-substrates is considered as a potent tool to expediently develop the molecular complexity with high atom efficiency. However, such an asymmetric and intermolecular process has yet to be developed fully. Herein, we report an efficient strategy to reductively couple two prochiral conjugate alkenes using a copper-catalysed tandem protocol in the presence of diboron. Notably, this transformation incorporates a wide range of terminal and internal enynes as coupling partners and facilitates highly diastereo- and enantioselective synthesis of organoboron derivatives with multiple adjacent stereocentres in a single operation.

The Coupling of Carbon and Nitrogen Substituents with Nitroarenes: Vicarious Nucleophilic Substitution of Hydrogen in Nitroarenes

Abstract: In recent years, nitroarenes have been extensively exploited as green, efficient electrophilic arylation reagents used in a variety of organic syntheses. Transition-metal-free cross-coupling reactions and vicarious nucleophilic substitution (VNS) have become practical and reliable synthetic methods to access momentous functionalized organic compounds. Thus, the introduction of various substituents into nitroarenes has attracted considerable attention as important synthetic approaches due to their simplicity and practicality. In this review, we comprehensively summarize the coupling of several carbon and nitrogen substituents with nitroarenes via nucleophilic substitution under mild conditions, followed by the application of these transversions in the construction of carbon and heterocyclic rings.

Nickel-Catalyzed Enantioselective C(sp 3 )–H Arylation of Ketones with Aryl Ethers via Selective C Ar –O Cleavage to Construct All-Carbon Quaternary Stereocenters

Nickel-Catalyzed Enantioselective C(sp ³ )–H Arylation of Ketones with Aryl Ethers via Selective C _Ar –O Cleavage to Construct All-Carbon Quaternary Stereocenters

Effect of amine properties on developing CO2 phase change absorbents by means of cosolvent effect

As China pledges that its carbon emissions will peak before 2030 and that it will be carbon neutral by 2060, the CO2 capture technology with high efficiency and low energy-consumption was expected in industry. CO2 phase change absorbents, CPCAs, had shown a potential to reduce energy consumption for CO2 capture. Although a lot of CPCAs were reported in the last decade, it still suffered from the lack of theoretical guidance for development. The effect of amine structure, which mainly affects cosolvent effect of amine and salting-out effect of formed salts, on developing CPCAs by means of cosolvent effect was clarified. For cosolvent effect of amine, 12 amines with various carbon chain lengths, isomers and substituents were determined by thermodynamical method and the log P of amine were proposed to characterize the cosolvent effect. The amine with long carbon chain and steric effect showed a high ability to act as a cosolvent to enhance the solubility of 1-butanol in H2O. The salting-out effect of formed salts by reacting amine and CO2 was related to pKa of amine. The absorbent comprising amine with low log P and high pKa was prefer to exhibit phase separation behavior, and benefit to develop CPCAs. Based on this guideline, all amines in this study could be developed as CPCAs by adjusting kinds of amine and diluent. Moreover, to explore the absorption-desorption performance of developed CPCAs, DEA/1-butanol/H2O was used as example, the volume ratio, species distributions and CO2 cyclic capacity were measured. When the absorption temperature was 303 K and desorption temperature was 373 K, The maximum CO2 cyclic capacity of CPCA was 2.03 mol CO2·kg−1, which was 34.4% higher than that of 30 wt% DEA/H2O.