C C Bond Research Articles

Ene-Reductase-Catalyzed Aromatization of Simple Cyclohexanones to Phenols.

Direct aromatization of cyclohexanones to synthesize substituted phenols represents a significant challenge in modern synthetic chemistry. Herein, we describe a novel ene-reductase (TsER) catalytic system that converts substituted cyclohexanones into the corresponding phenols. This process involves the successive dehydrogenation of two saturated carbon-carbon bonds within the six-membered ring of cyclohexanones and utilizes molecular oxygen to drive the reaction cycle. It demonstrates a versatile and efficient approach for the synthesis of substituted phenols, providing a valuable complement to existing chemical methodologies.

Phosphate modified nanoarchitectonics for promoted photocatalytic singlet oxygen generation and carbamazepine degradation of (0 1 0) facet-exposed BiOCl

1O2 generation over (001) or (010) facet exposed BiOCl (B001 or B010) with/without phosphate modification were studied from the aspects of excitons involved energy transfer route, the O2− oxidation based charge transfer route and the H2O2 oxidation by HClO. Phosphate modification not only enhance charge separation thus result in H2O2 oxidation by HClO to release 1O2 but also weaken excitonic effect in the confined layer of BiOCl accordingly affect 1O2 generation via energy transfer. Considering [001] orientation favors the formation of excitons than that of [010] direction over BiOCl, excitons loss was hardly compensated by the H2O2 oxidation by HClO for 1O2 generation over phosphate modified B001. Nevertheless, limited excitonic effect makes the O2− oxidation by h+ via charge transfer as dominant route for 1O2 yielding over B010, the extra H2O2 oxidation with HClO after phosphate modification significantly enhance 1O2 generation over B010 followed with 2.2 times higher carbamazepine photodegradation activity. The initial attack of CC bond via 1O2 to form epoxide played important roles on carbamazepine degradation. This study demonstrated that the facet-specific phosphate modification of photocatalysts can finely tune reactive 1O2 species for superior pharmaceuticals degradations.

Characterization of a cytochrome P450 that catalyzes the O-demethylation of lignin-derived benzoates

Cytochromes P450 (P450s) are a superfamily of heme-containing enzymes possessing a broad range of monooxygenase activities. One such activity is O-demethylation, an essential and rate-determining step in emerging strategies to valorize lignin that employ carbon-carbon bond cleavage. We recently identified PbdA, a P450 from Rhodococcus jostii RHA1, and PbdB, its cognate reductase, which catalyze the O-demethylation of para-methoxylated benzoates (p-MBAs) to initiate growth of RHA1 on these compounds. PbdA had the highest affinity (Kd = 3.8 ± 0.6 μM) and apparent specificity (kcat/KM = 20 000 ± 3 000 M-1 s-1) for p-MBA. The enzyme also O-demethylated two related lignin-derived aromatic compounds with remarkable efficiency: veratrate and isovanillate. PbdA also catalyzed the hydroxylation and dehydrogenation of p-EB even though RHA1 did not grow on this compound. Atomic-resolution structures of PbdA in complex with p-MBA, p-EB and veratrate revealed a cluster of three residues that form hydrogen bonds with the substrates’ carboxylate: Ser87, Ser237 and Arg84. Substitution of these residues resulted in lower affinity and O-demethylation activity on p-MBA as well as increased affinity for the acetyl analogue, p-methoxyacetophenone. The S87A and S237A variants of PbdA also catalyzed the O-demethylation of an aldehyde analogue of p-MBA, p-methoxy-benzaldehyde, while the R84M variant did not, despite binding this compound with high affinity. These results suggest that Ser87, Ser237 and Arg84 are not only important determinants of specificity but also help to orientate that substrate correctly in the active site. This study facilitates the design of biocatalysts for lignin valorization.

Syntheses of Phosphonylated Pyrido-Dihydrofurans by Regioselective 5-Exo-dig Addition to Carbon-Carbon Triple Bond Catalyzed by AgNO3.

The tandem nucleophilic addition-cyclization reaction of o-alkynylpyridinecarbaldehyde 1 with dialkyl phosphites 2 took place very smoothly in the presence of AgNO3 under base conditions in DCE at 50 °C. In all cases, the reaction proceeded in a regioselective manner leading to the 5-exo-dig phosphonylated pyrido-dihydrofurans 3 in moderate to good yields.

The Progress of Reductive Coupling Reaction by Iron Catalysis.

The transition metal catalyzed coupling reaction has revolutionized the strategies for forging the carbon-carbon bonds. In contrast to traditional cross-coupling methods using pre-prepared nucleophilic organometallic reagents, reductive coupling reactions for the C-C bonds formation provide some advantages. Because both coupling partners are reduced in the final products using a stoichiometric amount of a reductant, this approach not only avoids the need to use sensitive organometallic species, but also provides an orthogonal and complementary access to classical coupling reaction. Notably, the reductive coupling reactions feature readily available fragments, promote good step economy, exhibit high functional group tolerance and unique chemoselectivity, which have propelled their increasingly popular in the organic synthesis. In recent years, due to the low price, minimal toxicity, and environmentally benign character, iron-catalyzed carbon-carbon coupling reactions have garnered significant attention from the organic synthetic chemists and pharmacologists, especially the iron-catalyzed reductive coupling. This review aims to provide an insightful overview of recent advances in iron-catalyzed reductive coupling reactions, and to illustrate their possible reaction mechanisms.

Multiscale study on fatigue healing performance and molecular healing behavior of self-healing SBS modified bitumen

Self-healing polymer modified bitumen based on dynamic chemical bonds is a potential approach to improve the durability of bitumen pavement and save fossil energy. Herein, a novel self-healing SBS modified bitumen on the basis of dynamic disulfide bonds and hydrogen bonds was prepared. Firstly, an aliphatic disulfide (A-ALD) with disulfide bonds and hydrogen bonds was synthesized. Then A-ALD/SBS modified bitumen (A-ALD/SMB) was prepared by blending A-ALD and SBS modified bitumen. The chemical structure and microstructure of A-ALD/SMB were evaluated. In addition, the self-healing performance of A-ALD/SMB at the macroscopic scale and the self-healing behavior at the molecular scale were investigated by a combination of fatigue healing test and molecular dynamics (MD) simulation. The chemical structure analysis showed the formation of disulfide bonds and hydrogen bonds in A-ALD, and A-ALD was successfully attached to the CC bonds in SBS. Fluorescent images revealed that a better network structure appeared in A-ALD/SMB and formed a two-phase continuous morphology. The optimal dosage of A-ALD in SBS modified bitumen was 0.6 %. The fatigue healing test results indicated that A-ALD markedly enhanced the self-healing ability of SBS modified bitumen, and prolonging resting time and raising healing temperature can increase the self-healing performance of A-ALD/SMB. When the damage degree, healing temperature, and resting time were 30 %, 30 °C, and 60 min, respectively, the healing rate of A-ALD/SMB was 98.5 %, which was 30.2 % higher than SMB. The MD simulation results showed that the A-ALD enhanced the molecular diffusion capacity of SBS modified bitumen, and crack healing time of A-ALD/SMB was earlier than that of SMB under the same conditions. When the healing temperature was 40 °C, the time for the A-ALD/SMB and SMB molecular chain segments to start contacting and healing was 27 ps and 49 ps, respectively, which was improved by 44.9 % for A-ALD/SMB compared to SMB. Furthermore, the self-healing behavior of A-ALD/SMB at the molecular scale was consistent with the self-healing performance at the macroscopic scale under different healing temperatures and damage degrees. This study provided a theoretical basis for exploring the self-healing mechanism of SBS modified bitumen.

Synthesis and characterization of fluorescent carbon dots obtained from citrus x sinensis by an eco-friendly method

The synthesis and characterization of fluorescent carbon dots (CDs) obtained by an environmentally friendly method through carbonization, fragmentation and centrifugation of orange peel (citrus x sinensis) are reported. By thermogravimetry, 4 degradation regions associated with hemicellulose, lignin and organic matter were found. The SEM micrograph shows a rough surface morphology with flakes and granulation due to the carbonization process. X-ray diffraction (XRD) shows a hexagonal crystalline structure associated with graphitic carbon, which was confirmed by Raman scatterings, Raman spectroscopy that presented two main vibrational bands, D and G, associated with active defects in the graphitic carbon crystalline structure. The Transmission electron microscopy (TEM) micrograph showed CDs of size 33.65 ± 0.68n, and with High-Resolution TEM (HRTEM) an interplanar distance of 0.213 nm in the direction of the crystal planes (100) of graphitic carbon was obtained, which were confirmed by XRD and Raman spectroscopy. X-ray photoelectron spectroscopy revealed the relative atomic composition and identified the strongest photoelectron transitions of carbon, sp2 (286 eV) and sp3 (285 eV), in graphitic carbon. Ultraviolet–visible (UV–Vis) spectroscopy of the CDs obtained from fragmentation graphitic carbon showed a band at 205 nm associated with CC bonds π-π* of CC and n-π*, as well as two bands at 276 and 328 nm associated with bond transitions. The Fourier Transform Infrared (FTIR) spectrum showed bands associated with CHs bonds as well as CC, CN bonds of the CDs. Fluorescence spectroscopy showed three emission bands at 2.43, 2.54 and 2.87 eV. The CDs showed the emission of the characteristic blue colour.

A novel dual-site fluorescent probe for the one-step detection of Cys and SO2 in living cells

BackgroundCysteine (Cys) is the major intracellular thiol and plays a key role in human pathology. Furthermore, endogenous sulfur dioxide (SO2) is produced in mammals. Abnormal levels of SO2 are commonly associated with a variety of respiratory, cardiovascular, and neurological diseases. Therefore, given their important role in life activities, it is significant to construct a fluorescent probe that can detection between Cys and SO2. ResultsWe have designed and synthesized a two-site fluorescent probe CUM with coumarin derivative and benzaldehyde molecules, which can detect and differentiate between Cys and SO2 through dual excitation wavelengths. Its carbon-carbon double bond reacts with Cys and undergoes a nucleophilic reaction, emitting green fluorescence at 520 nm, while SO32− reacts with benzaldehyde molecules in the probe CUM and undergoes a blue fluorescence at 460 nm. SO32− reacts with the benzaldehyde molecule of probe CUM and fluoresces blue at 460 nm. Thus, the probe CUM with two reaction sites can distinguish between Cys and SO2 and shows good selectivity and fast reaction speed. In addition, we successfully utilized probe CUM to image Cys and SO2 in human breast cancer cells (MDA-MB-231). SignificanceThis work provides an effective method for the molecular design of coumarin-based fluorescent probes. Probe CUM as a promising and reliable tool for the meticulous discrimination and quantification of Cys and SO2 in diverse biological matrices, thereby opening up new avenues for various biological systems.

Mesoporous Vinylene-Linked Covalent Organic Frameworks with Heteroatom-Tuned Crystallinity and Photocatalytic Behaviors.

Owing to its prominent π-delocalization and stability, vinylene linkage holds great merits in the construction of covalent organic frameworks (COFs) with promising semiconducting properties. However, carbon-carbon double bond formation reaction always exhibits relatively low reversibility, unfavorable for the formation of high crystalline frameworks through self-error correction and assembling processes. In this work, we report a heteroatom-tuned strategy to build up a series of two-dimensional (2D) vinylene-linked COFs by Knoevenagel condensation of an electron-deficient methylthiazolyl-based monomer with different triformyl substituted (hetero-)aromatic derivatives. The resulting COFs show high-quality periodic mesoporous structures with high surface areas. Embedding heteroatoms into the backbones enables significantly improving their crystallinity, and finely tailoring their semiconducting structures. Upon visible light stimulation, one of the as-prepared COFs with donor-π-acceptor structure could deliver a nearly seven-fold increase in the catalytic activity of hydrogen generation as compared with the other two. Meanwhile, in combination with high crystallinity and the matched conduction band energy level, such kind of COFs can be able to selectively generate singlet oxygen and superoxide radicals in a high ratio of up to 30 : 1, allowing for catalyzing aerobic thioanisole oxidation in distinctly tunable activities through the substituent electronic effect of the substrates.

Recent Advance in the Reductive Heck Cyclization for the Formation of Five to Nine Member Rings

Abstract: Palladium-catalyzed reactions are widely used for creating carbon-carbon and carbon-heteroatom bonds, with the Heck reaction being particularly valuable for forming rings of various sizes, including mediumsized rings. Recent reports have shown the synthetic potential of intramolecular Heck reactions for assembling rings of seven or more members. While the regioselectivity of this cyclization is often unpredictable in the absence of directing groups, the reductive Heck cyclization strategy can help minimize this issue. Nickel catalysts are also valuable due to their abundance and environmentally friendly nature, playing a pivotal role in producing biologically significant carbocycles and heterocycles. The use of both Pd(0) and Ni(0) catalysts, with or without chiral ligands, has been successful in forming five to nine-member ring heterocycles and carbocycles in a simple, cost-effective manner. This review provides a comprehensive survey of the literature from the past decade on the use of reductive Heck cyclization methodology, including mechanistic details as needed.

Radical-triggered translocation of C-C double bond and functional group.

Multi-site functionalization of molecules provides a potent approach to accessing intricate compounds. However, simultaneous functionalization of the reactive site and the inert remote C(sp3)-H poses a formidable challenge, as chemical reactions conventionally occur at the most active site. In addition, achieving precise control over site selectivity for remote C(sp3)-H activation presents an additional hurdle. Here we report an alternative modular method for alkene difunctionalization, encompassing radical-triggered translocation of functional groups and remote C(sp3)-H desaturation via photo/cobalt dual catalysis. By systematically combining radical addition, functional group migration and cobalt-promoted hydrogen atom transfer, we successfully effectuate the translocation of the carbon-carbon double bond and another functional group with precise site selectivity and remarkable E/Z selectivity. This redox-neutral approach shows good compatibility with diverse fluoroalkyl and sulfonyl radical precursors, enabling the migration of benzoyloxy, acetoxy, formyl, cyano and heteroaryl groups. This protocol offers a resolution for the simultaneous transformation of manifold sites.

Electro-photochemical Functionalization of C(sp3)-H bonds: Synthesis toward Sustainability.

Over the past several decades, there has been a surge of interest in harnessing the functionalization of C(sp3)-H bonds due to their promising applications across various domains. Yet, traditional methodologies have heavily leaned on stoichiometric quantities of costly and often environmentally harmful metal oxidants, posing sustainability challenges for C-H activation chemistry at large. In stark contrast, the emergence of electro-photocatalytic-driven C(sp3)-H bond activation presents a transformative alternative. This approach offers a viable route for forging carbon-carbon and carbon-heteroatom bonds. It stands out by directly engaging inert C(sp3)-H bonds, prevalent in organic compounds, without the necessity for prefunctionalization or harsh reaction conditions. Such methodology simplifies the synthesis of intricate organic compounds and facilitates the creation of novel chemical architectures with remarkable efficiency and precision. This review aims to shed light on the notable strides achieved in recent years in the realm of C(sp3)-H bond functionalization through organic electro-photochemistry.

Density functional theory studies on combustion oxidative decomposition mechanism of 3,3,3-trifluoropropene

The environmentally friendly refrigerant 3,3,3-trifluoropropene (HFO-1243zf) suitable for refrigeration and heat pump systems has flammability. Based on density functional theory, the oxidation decomposition mechanism of 3,3,3-trifluoropropene was studied, including the main initial oxidation decomposition and subsequent reactions. The results indicate that among the initial thermal decomposition reactions, the reaction with the lowest energy barrier is simultaneous elimination of HF, followed by CC bond breaking to form ∙CF3. In the H abstraction reaction, the reaction energy barrier of H atom capture by ∙F is the lowest. In F abstraction reaction, the ∙H is the most active. In the addition reaction, the reaction energy barrier of ∙F is the lowest. The energy barriers of reactions involving different free radicals, from high to low, are: thermal decomposition, F abstraction, H abstraction and addition reaction. The subsequent reactions mainly involve the generation pathways of ∙CF3 and the formation of stable products.

Molecular Editing of Toluene by Sequential meta-C-H/Benzylic C-N Deaminative Functionalizations.

An approach to synthesizing structurally diverse toluene derivatives via sequential meta-C-H and benzylic C-N deaminative functionalization was developed by using a recyclable bifunctional directing template. The functionalized Katritzky salt intermediates are shown to be engaged in a wide range of carbon-carbon and carbon-heteroatom bond formation reactions. The synthetic utility of the strategy was demonstrated by late-stage functionalization of toloxatone.

CYP3A-Mediated Carbon-Carbon Bond Cleavages in Drug Metabolism.

Cytochrome P450 enzymes (P450s) play a critical role in drug metabolism, with the CYP3A subfamily being responsible for the biotransformation of over 50% of marked drugs. While CYP3A enzymes are known for their extensive catalytic versatility, one intriguing and less understood function is the ability to mediate carbon-carbon (C-C) bond cleavage. These uncommon reactions can lead to unusual metabolites and potentially influence drug safety and efficacy. This review focuses on examining examples of C-C bond cleavage catalyzed by CYP3A, exploring the mechanisms, physiological significance, and implications for drug metabolism. Additionally, examples of CYP3A-mediated ring expansion via C-C bond cleavages are included in this review. This work will enhance our understanding of CYP3A-catalyzed C-C bond cleavages and their mechanisms by carefully examining and analyzing these case studies. It may also guide future research in drug metabolism and drug design, improving drug safety and efficacy in clinical practice.

Water-catalyzed iron-molybdenum carbyne formation in bimetallic acetylene transformation

Transition metal carbyne complexes are of fundamental importance in carbon-carbon bond formation, alkyne metathesis, and alkyne coupling reactions. Most reported iron carbyne complexes are stabilized by incorporating heteroatoms. Here we show the synthesis of bioinspired FeMo heterobimetallic carbyne complexes by the conversion of C2H2 through a diverse series of intermediates. Key reactions discovered include the reduction of a μ-η2:η2-C2H2 ligand with a hydride to produce a vinyl ligand (μ-η1:η2-CH = CH2), tautomerization of the vinyl ligand to a carbyne (μ-CCH3), and protonation of either the vinyl or the carbyne compound to form a hydrido carbyne heterobimetallic complex. Mechanistic studies unveil the pivotal role of H2O as a proton shuttle, facilitating the proton transfer that converts the vinyl group to a bridging carbyne.

Interface-rich porous Fe-doped hcp-PtBi/fcc-Pt heterostructured nanoplates enhanced the C[sbnd]C bond cleavage of C3 alcohols electrooxidation

Efficient CC bond cleavage and the complete oxidation of alcohols are key to improving the efficiency of renewable energy utilization. Herein, we successfully prepare porous Fe-doped hexagonal close-packed (hcp)-PtBi/face-centered cubic (fcc)-Pt heterostructured nanoplates with abundant grain/phase interfaces (h-PtBi/f-Pt@Fe1.7 PNPs) via a simple solvothermal method. The open porous structure, abundant grain/phase interface and stacking fault defects, and the synergistic effect between intermetallic hcp-PtBi and fcc-Pt make h-PtBi/f-Pt@Fe1.7 PNPs an effective electrocatalyst for the glycerol oxidation reaction (GOR) in direct glycerol fuel cells (DGFCs). Notably, the h-PtBi/f-Pt@Fe1.7 PNPs exhibit an excellent mass activity of 7.6 A mgPt−1 for GOR, 4.75-fold higher than that of commercial Pt black in an alkaline medium. Moreover, the h-PtBi/f-Pt@Fe1.7 PNPs achieve higher power density (125.8 mW cm−2) than commercial Pt/C (81.8 mW cm−2) in a single DGFC. The h-PtBi/f-Pt@Fe1.7 PNPs can also effectively catalyze the electrochemical oxidation of 1-propanol (17.1 A mgPt−1), 1,2-propanediol (7.2 A mgPt−1), and 1,3-propanediol (5.2 A mgPt−1). The in-situ Fourier-transform infrared spectra further reveal that the CC bond of glycerol, 1-propanol, 1,2-propanediol, and 1,3-propanediol was dissociated for the complete oxidation by the h-PtBi/f-Pt@Fe1.7 PNPs. This study provides a new class of porous Pt-based heterostructure nanoplates and insight into the intrinsic activity of different C3 alcohols.

Stereoselective C-B and C-H Bonds Functionalization of PolyBorylated Alkenes.

Alkenes are fundamental functional groups which feature in various materials and bioactive molecules; however, efficient divergent strategies for their stereodefined synthesis are difficult. In this regard, numerous synthetic methodologies have been developed to construct carbon-carbon bonds with regio- and stereoselectivity, enabling the predictable and efficient synthesis of stereodefined alkenes. In fact, an appealing alternative approach for accessing challenging stereodefined alkene molecular frameworks could involve the sequential selective activation and cross-coupling of strong bonds instead of conventional C-C bond formation. In this study, we introduce a series of programmed site- and stereoselective strategies that capitalizes on the versatile reactivity of readily accessible polymetalloid alkenes (i.e. polyborylated alkenes), through a tandem cross-coupling reaction, which is catalyzed by an organometallic Rh-complex to produce complex molecular scaffolds. By merging selective C-B and remote C-H bond functionalization, we achieve the in situ generation of polyfunctional C(sp2)-nucleophilic intermediates. These species can be further modified by selective coupling reactions with various C-based electrophiles, enabling the formation of C(sp2)-C(sp3) bond for the generation of even more complex molecular architectures using the readily available starting polyborylated-alkenes. Mechanistic and computational studies provide insight into the origins of the stereoselectivities and C-H activation via a 1,4-Rh migration process.

Efficient catalytic removal of phenolic pollutants by laccase from Coriolopsis gallica: Binding interaction and polymerization mechanism

Laccase is a green catalyst that can efficiently catalyze phenolic pollutants, and its catalytic efficiency is closely related to the interaction between enzyme and substrates. To investigate the binding effects between enzyme and phenolic pollutants, phenol, p-chlorophenol, and bisphenol A were used as substrates in this study. We focused on the removal and catalytic mechanism of these pollutants in water using yellow laccase derived from Coriolopsis gallica. The enzymatic catalytic products were characterized using Ultraviolet-Visible Absorption Spectroscopy (UV–Vis), Fourier Transform Infrared Spectroscopy (FTIR), and High-Resolution Mass Spectrometry (HRMS), and the catalytic mechanism of laccase on phenolic pollutants was further explored by molecular docking. Based on the structural characterization and molecular docking results, the possible polymerization pathways of these phenolic compounds were speculated. Laccase catalyzed phenol to produce phenolic hydroxyl radicals, their para-radicals, and ortho-radicals, which polymerized to form oligomers linked by benzene‑oxygen-benzene and benzene-benzene. P-chlorophenol produced phenolic hydroxyl radicals and their ortho-radicals, polymerizing to form oligomers connected by benzene‑oxygen-benzene or benzene-benzene. The CC bond of the isopropyl group of bisphenol A broke to formed an intermediate product, which was further polymerized to formed a benzene‑oxygen-benzene linked oligomer.

Molecular geometry specific Monte Carlo simulation of the efficacy of diamond crystal formation from diamondoids

Diamondoids are a class of organic molecules with the carbon skeletons isostructural to nano-diamond, and have been shown to be promising precursors for diamond formation. In this work, the formation of diamond crystals from various diamondoid molecule building blocks was studied using our developed molecular geometry specific Monte Carlo method. We maintained the internal carbon skeletons of the diamondoid molecules, and investigated how the carbon-carbon bonds form between diamondoid molecules and how efficient the process is to form diamond crystals. The simulations show that higher diamondoid molecules can produce structures closer to a diamond crystal compared with lower diamondoid molecules. Specifically, using higher diamondoid molecules, larger bulk diamond crystals are formed with fewer vacancies. The higher propensity of certain diamondoids to form diamond crystals reveals insights into the microscopic processes of diamond formation under high-pressure high-temperature conditions.