Phenyl Formate Research Articles

Development of Controllable Hetero-Pauson-Khand Polymerization to Functional Stimuli-Responsive Poly(γ-lactam)s.

Polymers containing lactam structures play a crucial role in both natural biological systems and human life, and their synthesis, functions and applications are of utmost importance for biomimetics and the creation of new materials. In this study, we developed an efficient heterogeneous Pauson-Khand polymerization (h-PKP) method for the controlled synthesis of main-chain poly(γ-lactam)s containing α, β-unsaturated γ-lactam functionalities using readily available internal alkynes and imines. The molecular weights of the resulting poly(N-Ts/γ-lactam)s can be precisely controlled by adjusting the ratio of phenyl formate and nickel. These polymers exhibit high solid-state luminescence and demonstrate rapid and sensitive dual responsiveness to light and acid stimuli. They further demonstrate strong reactive oxygen species (ROS) generation capability. The unique dual-emission peaks observed in poly(N-H/γ-lactam)s obtained through post-treatment under acidic conditions demonstrate a mechanism of aggregation-induced intermolecular excited-state proton transfer specific to lactam structures. The efficient one-pot synthetic method for poly(γ-lactam) provides a novel strategy for constructing polymers with γ-lactam structures in the main chain and the simple and efficient post-modification method offer a versatile toolbox for functionalizing poly(γ-lactam)s to expand their potential applications.

Development of Controllable Hetero‐Pauson‐Khand Polymerization to Functional Stimuli‐Responsive Poly(γ‐lactam)s

Polymers containing lactam structures play a crucial role in both natural biological systems and human life, and their synthesis, functions and applications are of utmost importance for biomimetics and the creation of new materials. In this study, we developed an efficient heterogeneous Pauson‐Khand polymerization (h‐PKP) method for the controlled synthesis of main‐chain poly(γ‐lactam)s containing α, β‐unsaturated γ‐lactam functionalities using readily available internal alkynes and imines. The molecular weights of the resulting poly(N‐Ts/γ‐lactam)s can be precisely controlled by adjusting the ratio of phenyl formate and nickel. These polymers exhibit high solid‐state luminescence and demonstrate rapid and sensitive dual responsiveness to light and acid stimuli. They further demonstrate strong reactive oxygen species (ROS) generation capability. The unique dual‐emission peaks observed in poly(N‐H/γ‐lactam)s obtained through post‐treatment under acidic conditions demonstrate a mechanism of aggregation‐induced intermolecular excited‐state proton transfer specific to lactam structures. The efficient one‐pot synthetic method for poly(γ‐lactam) provides a novel strategy for constructing polymers with γ‐lactam structures in the main chain and the simple and efficient post‐modification method offer a versatile toolbox for functionalizing poly(γ‐lactam)s to expand their potential applications.

A study on the surface responses and degradation mechanisms of epoxy-amine coating subjected to UV accelerated weathering and hygrothermal ageing using ToF-SIMS and FTIR analysis

Epoxy amine coatings were subjected to hygrothermal ageing and accelerated weathering conditions that is comprised of neutral salt spray test and UV accelerated degradation condition. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and Fourier Transform Infrared Spectroscopy (FTIR) were employed to study the surface responses and spectral variation of epoxy amine coatings subjected to different ageing conditions. As a result, principal component analysis (PCA) of ToF-SIMS positive ion spectra illustrated that principal component 1 (PC1) has collected information on a variation of surface responses caused by accelerated weathering and hygrothermal ageing conditions as compared to fresh epoxy amine coatings. On the other hand, principal component 2 (PC2) has distinguished the different surface responses generated on epoxy amine coatings that were subjected to UV accelerated degradation conditions and those that were not. FTIR analysis has demonstrated the hydrolysis and photooxidation of epoxy amine coatings from the growth of two absorption bands at 1709 cm−1 and 1650 cm−1, indicating the formation of carbonyl-containing groups such as ketones, aldehydes, phenyl formates, imine or tertiary amides. This comprehensive analysis provides significant insights into the degradation mechanisms of epoxy amine coatings subjected to corrosion under insulation (CUI) and/or artificial weathering (AW) environment. Understanding these mechanisms is pivotal for industries reliant on epoxy coatings, such as oil and gas, ensuring enhanced performance and extended lifespan of their products under varying environmental conditions. The findings also contribute to the broader field of materials science by offering methodologies and analytical approaches that can be applied to other polymeric coatings and materials.

Nickel/Photoredox-Catalyzed Carbonylative Cross-Electrophile Coupling of Organohalides and Carboxylic Acid Esters with Phenyl Formate.

A photoinduced nickel-catalyzed reductive carbonylative coupling from organohalides and N-(acyloxy)phthalimide esters with phenyl formate as the carbonyl source has been developed. This reaction could perform smoothly under mild conditions, and a series of aryl-alkyl and alkyl-alkyl unsymmetrical ketones were produced without the need of stoichiometric metal reductants. Mechanistic studies indicate that this reaction was initiated from radical capture by Ni(I)-carbonyl species and subsequent rapid carbonyl insertion.

Synthesis and anticancer screening of substituted (phenyl)-1-((naphthalen-5-yl)methylene)thiosemicarbazide against PC3 prostate cancer cells

Multicomponent reaction among substituted isothiocyanate, hydrazine hydrate, and naphthalene-1-carbaldehyde in the presence of the phase transfer reagent Triton-B and subsequently heating lead to the formation of (Phenyl)-1-((naphthalen-5-yl)methylenethiosemicarbazide. Anticancer screening of the synthesized compound against prostate cancer cells PC3 showed that compound 2 ((Z)-4-(2-fluorophenyl)-1-((naphthalen-5-yl)methylene)thiosemicarbazide), 4 ((Z)-4-(2-chlorophenyl)-1-((naphthalen-5-yl)methylene)thiosemicarbazide) and 12 exhibited appreciable inhibitions on the PC3 cells. Next step evaluation of compounds on flow cytometry for apoptotic behavior revealed significant apoptosis of cancer cells by compound 12 i.e. (Z)-4-(4-chlorophenyl)-1-((naphthalen-5-yl)methylene)thiosemicarbazide which necessitates its further exploration.

Cyclometalated half‐sandwich iridium complexes: Synthesis, characterization, and catalytic activity in preparation of esters from halides by using formate as both CO source and coupling partner

A highly efficient carbonylation of aryl halides using half‐sandwich iridium catalysis was developed, providing a new avenue for synthesizing carboxylic ester derivatives and yielding consistently impressive results. These iridium complexes demonstrated remarkable catalytic performance in the coupling reaction using phenyl formate derivatives as the source of CO, phenol, and aryl halides as the starting material in the presence of air and possessed good air and moisture stability properties. Ester products with different substituents were synthesized at low reaction temperatures without the need for an inert atmosphere, leading to high yields. The broad substrate scope, impressive catalytic activity, and mild reaction conditions suggest promising industrial applications for this catalytic system. The desired metal complexes 1–4 have been well proven by attenuated total reflectance‐Fourier transform infrared (ATR‐FTIR), nuclear magnetic resonance (NMR), and elemental analysis (EA). The molecular structure of the cyclometalated iridium complexes 2 and 3 was proven through X‐ray crystallography. Additionally, the possible mechanism of this Ir‐catalyzed process is further supported by the density functional theory (DFT) study.

A Review of Synthetic Application of Homogeneous, Heterogenised‐Homogeneous, and Microwave‐Assisted Catalytic Carbonylation of Selected Substrates

AbstractCatalytic carbonylation has gained a lot of interest over the past 20 years. It produced various pharmaceuticals, agrochemicals, and intermediates that can made through this process. The carbonylation process is the most straightforward method to insert CO into any organic substrate using a simple carbonyl source, i. e., CO gas. Apart from gaseous CO, many techniques have devised for producing CO in situ using surrogates such as HCOOH, DMF, Formic acid, Phenyl Formate, Oxalic acid, and Chloroform. Several carbonylation methods, such as aminocarbonylation, alkoxycarbonylation, double carbonylation, and oxidative carbonylation, provide viable and appealing substitutes for conventional synthetic methods on a commercial or laboratory scale. Many recent studies focus on catalyst‐product separation, catalyst recoverability, and reusability in these reactions. Therefore, advancements in using different approaches, such as supported liquid phase catalysis and biphasic catalysis, to anchor homogeneous catalysts are becoming increasingly important. These carbonylation methods are easy to use, cost‐effective, and do not require ligands. They also produce excellent yields of the products necessary. Using phosphine ligands has drawbacks, including high work‐up costs, laborious work‐up techniques, and sensitivity to air and moisture. Several phosphine‐free carbonylation pathways offer affordable and straightforward ways to accomplish these changes without phosphine ligands. This review summarizes the synthetic application of homogeneous and immobilized catalysts in producing carboxylic acid derivatives and heterocycles that have medicinal properties.

Visible-light photocatalysed synthesis of coumarin derivatives

A straightforward, environmentally friendly, and highly efficient, metal-free, visible light mediated organophotocatalysed method has been devised for synthesizing potentially biologically active substituted coumarin scaffolds. This method involves the reaction between substituted ethynylbenzene and substituted phenyl formate under visible light photoredox catalysed conditions at room temperature using acridinium as photocatalyst. The distinctive characteristics of the current methodology include mild reaction conditions, yielding good to excellent outcomes, promoting high atom-economy, environmentally friendly practices, clean reaction profiles, and suitability for large-scale synthesis.

What a difference a chlorine makes: The remarkable unimolecular ion chemistry of phenyl formate and phenyl chloroformate.

Imaging photoelectron photoion coincidence (iPEPICO) spectroscopy and tandem mass spectrometry were employed to explore the ionisation and dissociative ionisation of phenyl formate (PF) and phenyl chloroformate (PCF). The threshold photoelectron spectra of both compounds are featureless and lack a definitive origin transition, owing to the internal rotation of the formate functional group relative to the benzene ring, active upon ionisation. CBS-QB3 calculations yield ionisation energies of 8.88 and 9.03 eV for PF and PCF, respectively. Ionised PF dissociates by the loss of CO via a transition state composed of a phenoxy cation and HCO moieties. The dissociation of PCF ions involves the competing losses of CO (m/z 128/130), Cl (m/z 121) and CO2 (m/z 112/114), with Cl loss also shown to occur from the second excited state in a non-statistical process. The primary CO- and Cl-loss fragment ions undergo sequential reactions leading to fragment ions at m/z 98 and 77. The mass-analysed ion kinetic energy (MIKE) spectrum of PCF+ showed that the loss of CO2 occurs with a large reverse energy barrier, which is consistent with the computationally derived minimum energy reaction pathway.

Enhancing photocatalytic destruction of lignin via cellulose derived carbon quantum dots/g-C3N4 heterojunctions

Lignocellulosic biomass exhibits a promising potential for production of carbon materials. Nitrogen and phosphorus co-doped carbon quantum dots (N,P-CQDs) were fabricated via (NH4)2HPO4 assisted hydrothermal treatment of cellulose pulp fibers. The as-prepared N,P-CQDs were characterized by HRTEM, FTIR, fluorescence and UV–vis, and then incorporated into g-C3N4 (CN) through sonication and liquid deposition, forming N,P-CQDs/sonication treated g-C3N4 (C-SCN) composites, which were then explored as photocatalysts. The photocatalytic ability of C-SCN towards model lignin was further analyzed. The results showed that, the fluorescence intensity and photoluminescence performance of N,P-CQDs were much higher than that of CQDs; the heterojunction was successfully constructed between the composites of N,P-CQDs and SCN; the incorporation of N,P-CQDs enhanced the visible light absorption, but reduced the band gap of the composite heterojunction; the resultant photocatalysts exhibited a good photocatalytic ability of model lignin via catalyze the fracture of β–O–4′ ether bond and CC bond, i.e., the photocatalytic degradation ratio reached up to 95.5 %; and the photocatalytic reaction generated some valuable organics such as phenyl formate, benzaldehyde, and benzoic acid. This study would promote the high value-added utilization of lignocellulosic resources especially in the transformation of lignin, conforming the concept of sustainable development.

Cyclometalated Half-Sandwich Ruthenium Complexes: Preparation, Structure, and Catalytic Synthesis of Phenolic Esters from Aryl Halides without Using External CO under Air.

A series of cyclometalated C,N-chelate half-sandwich ruthenium complexes based on N-heterocyclic ligands were prepared through a simple route with good yields. These air- and moisture-stable cyclometalated ruthenium complexes showed excellent catalytic efficiency in phenoxy carbonylation of aryl halides with phenyl formate derivatives as a CO source and phenol as a coupling partner under air. Ester products were obtained with high yields at room temperature and without the need for an inert atmosphere. The excellent catalytic activity, broad substrate range, and mild reaction conditions made this catalytic system potential for industrial production. In addition, DFT study has been carried out to elaborate the possible mechanism of this Ru-catalyzed reaction.

Photoinduced organocatalytic lignin C–C bond cleavage in mixed binary solvents

Lignin presents a renewable alternative of fossil feedstock to produce value-added aromatic chemicals. Oxidative cleavage of C−C bonds in lignin is of great importance, but obtaining aromatic monomers in high selectivity under mild conditions is challenging. Herein, we report a novel strategy of photoinduced oxidative C–C cleavage of lignin β–O–4 derivatives using photoredox organocatalysts, among which Mes-10-phenyl-Acr+-BF4– exhibited high yields of aromatic aldehydes and phenyl formate. Besides, mixed binary organic solvents were demonstrated to promote bond cleavage and inhibit over-oxidation side reactions. The absorbance, excitation, and interaction with the lignin model of the photocatalyst in different solvents were investigated by UV-Vis, PL, and CV tests. Furthermore, through mechanism studies, a C-centered radical intermediate was captured, providing evidence for the direct Cα−Cβ bond cleavage mechanism during the reaction. This work presents a new photocatalytic strategy and provides deep insights into the bond cleavage mechanism for lignin valorization.

Enhancing photocatalytic cleavage of C[sbnd]C bonds in lignin model substrates by ternary nanocomposite of g-C3N4/rGO/CdS using rGO as electronic mediators

Depolymerizing lignin into aromatic monomers with high yield and selectivity via photocatalysis remains a challenging task. Herein, we introduced reduced graphene oxide (rGO) nanosheets as solid electronic mediators and successfully synthesized g-C3N4/rGO/CdS ternary nanocomposites using a simple multi-step assembly strategy. The photocatalysts can efficiently break the CC bond of lignin under simulated sunlight conditions. The characterization results demonstrate that the loading of CdS effectively enhances the light absorption range and accelerates the transfer of photogenerated charge carriers. Simultaneously, the introduction of rGO inhibits the recombination of electron-hole pairs. When using the β-O-4 model substrate, a 95% conversion rate could be achieved with yields of 71% benzaldehyde and 69% phenyl formate, which are 3.09 times and 3.63 times higher than that of pure g-C3N4, respectively. Our research highlights the importance of energy band structure engineering and electronic mediator design in developing efficient photocatalysts for breaking CC bonds of lignin.

Liquid Organic Hydrogen Carriers: Model Catalytic Studies on the Thermal Dehydrogenation of 1-Cyclohexylethanol on Pt(111)

The molecule pair of 1-cyclohexylethanol and acetophenone represents an interesting system for a chemical hydrogen storage cycle as it combines two different classes of so-called liquid organic hydrogen carriers (LOHCs), namely hydrogenated, formerly aromatic cyclic hydrocarbons and alcohols, i.e., hydrogenated carbonyls. In particular, the latter have recently attracted much attention due to their favorable dehydrogenation temperatures and the possibility to convert them directly into electricity in specially designed direct-LOHC fuel cells. Herein, we investigate the temperature-triggered dehydrogenation reaction of 1-cyclohexylethanol to acetophenone on a Pt(111) model catalyst using synchrotron-based temperature-programed X-ray photoelectron spectroscopy. To obtain a complete picture of the reaction mechanism, we consider not only the individual surface reactions of 1-cyclohexylethanol and acetophenone but also those of two potential dehydrogenation intermediates, namely, the partially dehydrogenated 1-cyclohexylethanone and 1-phenylethanol. We find a stepwise dehydrogenation of 1-cyclohexylethanol: the first step around ∼210 K at the alcohol moiety yields the ketone 1-cyclohexylethanone. The second step above ∼260 K at the cyclohexyl group is accompanied by the loss of an H-atom at the molecule’s methyl group and leads to the formation of an acetophenone-like phenyl–C(O)–CH2 species at ∼340 K. The same species are also identified in the surface reactions of acetophenone, 1-phenylethanol, and 1-cyclohexylethanone in this temperature range. Overall, the system shows good thermal robustness: a complete dehydrogenation of the hydrogen-rich carrier occurs without damage to the carbon framework.

On the Gas-Phase Interactions of Alkyl and Phenyl Formates with Water: Ion-Molecule Reactions with Proton-Bound Water Clusters.

Ion-molecule reactions between the neutral ethyl- (EF), isopropyl- (IF), t-butyl- (TF) and phenyl formate (PF) and proton-bound water clusters W2H+ and W3H+ (W = H2O) showed that the major reaction product is water loss from the initial encounter complex, followed ultimately by the formation of the protonated formate. Collision-induced dissociation breakdown curves of the formate-water complexes were obtained as a function of collision energy and modeled to extract relative activation energies for the observed channels. Density functional theory calculations (B3LYP/6-311+G(d,p)) of the water loss reactions were consistent with reactions having no reverse energy barrier in each case. Overall, the results indicate that the interaction of formates with atmospheric water can form stable encounter complexes that will dissociate by sequential water loss to form protonated formates.

Selective Photocatalytic C–C Bond Cleavage of Lignin Models and Conversion to High-Value Chemical by Polyoxometalate Under a Mild Water-Based Environment

Selective bond cleavage using a photoredox reaction is a powerful technique in the chemical conversion of biomass such as lignin since it enables us to produce value-added aromatic compounds by controlling the activation of certain chemical bonds. Also, a water-based environment would be preferred for the sake of an eco-friendly reaction, additionally having the advantage of utilizing water-originated species such as •OH and H2O2. However, a direct cleavage of the C–C bond is still challenging due to the difficulties in tailoring redox potentials of catalysts relevant to covalent bond decoupling. Herein, we investigate a selective C–C bond cleavage of the β-O-4 lignin model compound using giant Keplerate polyoxometalates as photocatalysts. The redox potentials of photocatalysts are varied by changing metal compositions, and the correlation between redox potential and covalent bond decoupling is elucidated, probing each set of active radicals by HOMO and LUMOs. Especially, Mo132 shows a highly selective C–C bond cleavage with hydroxyl groups in the lignin model and produces phenyl formate─a effective CO surrogate for the synthesis of various organic compounds─as the main product (97.8% of product selectivity) in a water-based condition. Furthermore, Mo132 decomposes other aromatic polymer models, indicating the potential of photocatalytic C–C bond decoupling of polymers under a benign environment.

Shaping of Pd@UiO-66-biguanidine MOFs into composite beads with Cu-based CMC for synergistic catalysis towards CO-free carbonylative Sonogashira reaction

Integrating fine metal-organic framework (MOF) crystals within various materials to obtain configurable shapes with desired size and mechanical stability is an essential prerequisite for their potential applications on a large scale. In this work, a novel composite bead (Pd@UG/Cu@CMC), composed of Zr-based UiO-66-biguanidine-supported Pd MOFs (Pd@UG) embedded in the three-dimensional (3D) networks of Cu2+ crosslinked carboxymethylcellulose (Cu@CMC), has been successfully fabricated using a simple and straightforward metal ion crosslinking technology. The architecture of Pd@UG/Cu@CMC composite beads has been analyzed in detail using inductively coupled plasma atomic emission spectrometry (ICP-AES), Brunner−Emmet−Teller (BET) surface area analysis, Fourier transform infrared (FTIR) spectra, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), elemental mapping, thermogravimetric analysis (TGA), derivative thermogravimetric analysis (DTG) tools. To validate the catalytic aptitude, the as-obtained Pd@UG/Cu@CMC beads were subsequently applied to carbonylative Sonogashira reactions using phenyl formate as a CO surrogate. The results showed that the catalyst had excellent catalytic performance over a broad scope of substrates under mild conditions and produced the desired products in moderate to excellent yields. The presence of Pd and Cu elements in the composite beads is essential, and the Cu played a dual role as both a crosslinker and co-catalyst in these reactions. The synergetic effect between Pd and Cu was conclusively evidenced by comparing them with Pd@UG, Cu@CMC, and their mixture, respectively. The composite beads retained their structure after seven consecutive runs with approximately 11% loss of catalytic efficiency. This work offers a promising route to shaping MOFs and provides suggestive insights for developing novel reusable bimetallic catalysts for high-performance synergistic catalysis.

Palladium(II)-Catalyzed Regioselective Hydroesterification of 1,3-Conjugated Enynes with Aryl Formates

An effective Pd-catalyzed regioselective hydroesterification of 1,3-conjugated enynes with aryl formates was developed. Under the Pd-CyDPEphos catalytic system, the conjugated enynes reacted with phenyl formates and selectively provided the 2-ester-substituted 1,3-dienes in good yields with excellent regioselectivities.

Phenyl Formate as a CO Surrogate for the Reductive Cyclization of Organic Nitro Compounds to Yield Different N-Heterocycles: No Need for Autoclaves and Pressurized Carbon Monoxide

The reductive cyclization of different organic nitro compounds by carbon monoxide, catalyzed by transition metal complexes, is a very efficient and clean strategy for the synthesis of many N-heterocycles. However, its use requires the use of autoclaves and pressurized CO lines. In this perspective, the authors will present the results obtained in their laboratories on the use of phenyl formate as a convenient CO surrogate, able to liberate carbon monoxide under the reaction conditions and allowing the use of a cheap glass pressure tube as a reaction vessel. In most cases, yields were better than those previously reported by the use of pressurized CO, proving that the use of CO surrogates can be a viable alternative to the gaseous reagent.

Selective cleavage of Cα–Cβbonds in lignin models using a bifunctional pyridinium photocatalystviaa PCET process

A pyridinium-based photocatalyst possessing both redox-active and hydrogen acceptor sites has been developed for the conversion of lignin models to afford benzaldehyde and phenyl formate as the main products through selective cleavage of C–C bonds.