Efficient One-Pot Synthesis of 2-Carbonyl- 1-indanols by Palladium-Catalyzed Tandem Heck–Aldol Reaction

2-Carbonyl-1-indanols were synthesized in moderate to good yields by the reaction of orthohalogenated aryl aldehyde with Morita–Baylis–Hillman adducts via a one-pot, palladium-catalyzed tandem Heck–aldol reaction. Various Morita–Baylis–Hillman adducts were examined to find the scope and limitations of this process.     

Direct Umpolung Morita–Baylis–Hillman like α-Functionalization of Enones via Enolonium Species

Herein we report on the umpolung of Morita–Baylis–Hillman type intermediates and application to the α-functionalization of enone C−H bonds. This reaction gives direct access to α-chloro-enones, 1,2-diketones and α-tosyloxy-enones. The latter are important intermediates for cross-coupling reaction and, to the best of our knowledge, cannot be made in a single step from enones in any other way. The proposed mechanism is supported by spectroscopic studies. The key initial step involves conjugate attack of an amine (DABCO or pyridine), likely assisted by hypervalent iodine acting as a Lewis acid leading to formation of an electrophilic β-ammonium-enolonium species. Nucleophilic attack by acetate, tosylate, or chloride anion is followed by base induced elimination of the ammonium species to give the noted products. Hydrolysis of α-acetoxy-enones lead to formation of 1,2-diketones. The α-tosyl-enones participate in Negishi coupling reactions under standard conditions.     

Esterification reaction kinetics of acetic acid and n-pentanol catalyzed by sulfated zirconia

This study reports experimental data and kinetic modeling of acetic acid esterification with n-pentanol using sulfated zirconia as a catalyst. Reactions were carried out in an isothermal well-mixed batch reactor at different temperatures (50-80°C), n-pentanol to acid molar ratios (1:1-3:1), and catalyst loadings (5-10 wt% in relation to the total amount of acetic acid). The reaction mechanism regarding the heterogeneous catalysis was evaluated considering pseudo-homogeneous, Eley–Rideal, and Langmuir–Hinshelwood model approaches. The reaction mixture was considered a nonideal solution and the UNIQUAC thermodynamic model was used to take into account the nonidealities in the liquid phase. The results obtained indicated that increases in the temperature and catalyst loading increased the product formation, while changes in the n-pentanol to acetic acid molar ratio showed no significant effect. The estimated enthalpy of the reaction was −8.49 kJ mol⁻¹, suggesting a slightly exothermic reaction. The Eley–Rideal model, with acetic acid adsorbed on the catalyst as the limiting step, was found to be the most significant reaction mechanism.     

Palladium–N-heterocyclic carbene complexes for the Mizoroki–Heck reaction: An appraisal

This article presents a review of the most significant developments with N-heterocyclic carbene (NHC)–palladium catalytic systems used for the Heck reaction. For more than the past two decades, a large number of new NHC–Pd complexes have been synthesized and characterized. These studies focused on NHCs as a phosphine analogue, but the current review highlights the differences with particular ligands so as to attain a suitable balance between the electronic and bulky environments around the metal. NHCs have gained wide recognition as these ligands act as excellent σ-donors that form stable metal–NHCs with strong metal–carbon bonds. For this reason, metal–NHCs are commonly used as they are highly reactive and can selectively serve as catalysts for various chemical transformations. The objective of our article is to highlight significant recent progress in NHC–Pd(II) complexes and provide an overview of their extensive interaction in the Mizoroki–Heck reaction.     

Allylsilane Reagent-Controlled Divergent Asymmetric Catalytic Reactions of 2-Naphthoquinone-1-methide

Herein, the first allylsilane reagent-controlled divergent asymmetric Hosomi–Sakurai conjugate allylation and hetero-Diels–Alder (HDA) with 2-naphthoquinone-1-methide (2-Nap-Q-1-M) under the catalysis of Sc^III/Feng ligand complex is reported. With these methods, a variety of uniquely substituted chiral allyl-functionalized diaryl compounds and naphthopyran products were obtained in a straightforward and highly stereoselective (up to 96.5:3.5 e.r.) manner under mild conditions. Moreover, it is demonstrated that 2-Nap-Q-1-M can serve as an efficient diene for a side asymmetric Diels–Alder (D-A) reaction. This principle can provide a straightforward access to hydrophenalene in an optically active form, which represents a structural core of various natural products and bioactive molecules.     

Transition-metal-free nucleophilic allylic substitutions of Morita–Baylis–Hillman bromides with aliphatic and aromatic amines

A simple protocol for the preparation of functionalized allylic amines under mild, transition-metal-free conditions from the reaction of Morita–Baylis–Hillman (MBH) bromides with amines is described herein. The treatment of the MBH bromides with various amines in the presence of NaI and Et₃N in aqueous acetone solution and at room temperature affords the corresponding functionalized allyl amines in moderate to good yields (45–87%). The reaction is rapid and carried out at room temperature.     

N‐Methylpiperidine—A Useful Base Catalyst in the Morita–Baylis–Hillman Reaction

N‐methylpiperidine, a commercially available mild base, has effectively been utilized as a catalyst in the Morita–Baylis–Hillman reaction. Moderate to excellent yields (34–95%) and significant rate enhancement have been observed.     

Multidimensional thermochemical cycles – Exploring three dimensions: Designer tool for estimation of the thermodynamics of reactions under varying conditions and for estimating elusive thermodynamic data

Born–Haber–Fajans (BHF) thermochemical cycles describe links among different aspects of a chemical reaction at a common temperature and pressure, independent of the actual process of the reaction, and so provide methods for evaluation of otherwise missing information. We show that the standard two-dimensional BHF cycle can be extended to allow for consideration of temperature and pressure variation, using temperature changes for the reaction between HCl and Na as our illustrative example. Such extension provides possibilities of multiple interrelationships among contemplated states of the process of the reaction, so enhancing the related thermodynamic information.Although thermodynamics and kinetics do not necessarily coincide, it may be possible, utilizing such insights, to circumvent kinetically-disallowed steps in a chemical synthesis by choosing an alternative but thermodynamically favored route.     

Progress and prospect of the zinc–iodine battery

The zinc–iodine battery has the advantages of high energy density and low cost owing to the flexible multivalence changes of iodine and natural abundance of zinc resources. Compared with the flow battery, it has simpler components and more convenient installation, yet it still faces challenges in practical applications. How to select suitable materials as the cathode and electrolyte to control the process of energy storage reaction and inhibit the self-transformation of by-products, together with the corrosion resistance of metallic zinc are crucial factors. Herein, the principles of the zinc–iodine flow battery and zinc–iodine battery are described, and the unprecedented progresses are highlighted. This mini review is anticipated to provide valuable guidance for the further development of the zinc–iodine battery.     

Photocatalytic Reductive Radical-Polar Crossover for a Base-Free Corey–Seebach Reaction

A metal-free generation of carbanion nucleophiles is of prime importance in organic synthesis. Herein we report a photocatalytic approach to the Corey–Seebach reaction. The presented method operates under mild redox-neutral and base-free conditions giving the desired product with high functional group tolerance. The reaction is enabled by the combination of photo- and hydrogen atom transfer (HAT) catalysis. This catalytic merger allows a C−H to carbanion activation by the abstraction of a hydrogen atom followed by radical reduction. The generated nucleophilic intermediate is then capable of adding to carbonyl electrophiles. The obtained dithiane can be easily converted to the valuable α-hydroxy carbonyl in a subsequent step. The proposed reaction mechanism is supported by emission quenching, radical–radical homocoupling and deuterium labeling studies as well as by calculated redox-potentials and bond strengths.     

Controlling Regioselectivity in Palladium-Catalyzed C−H Activation/Aryl–Aryl Coupling of 4-Phenylamino[2.2]paracyclophane

Selective activation/functionalization of C−H bonds has emerged as an atom- and step-economical process at the forefront of modern synthetic chemistry. This work reports palladium-catalyzed exclusively para-selective C−H activation/aryl–aryl bond formation with a preference over N-arylation under the Buchwald–Hartwig amination reaction of 4-phenylamino[2.2]paracyclophane. This innovative synthetic strategy allows a facile preparation of [2.2]paracyclophane derivatives featuring disparate para-substitutions at C-4 and C-7 positions in a highly selective manner, gives access to a series of potential candidates for [2.2]paracyclophane-derived new planar chiral ligands. The unprecedented behavior in reactivity and preferential selectivity of C−C coupling over C−N bond formation via C−H activation is unique to the [2.2]paracyclophane scaffold compared to the non-cyclophane analogue under the same reaction conditions. Selective C−H activation/aryl–aryl bond formation and sequential C−N coupling product formation is evidenced unambiguously by X-ray crystallography.     

Characterization of Catalysts for Glycerol Ester Production with Various Acetylating Agents

The use of raw materials from renewable sources by industries is essential to the sustainable development of modern society. The biodiesel produced by the transesterification of vegetable oils is a less polluting diesel fuel, but large amounts of glycerol (10% of total weight of product) are generated during the production process. The scientific community and industries of the sector know that, in the future, the amount of glycerol generated can cause a serious ecologic problem. Thus, it is essential to find alternatives for the consumption of this co-product, in its crude form and/or as high value-added derivatives. This work studied obtaining triacetate from the glycerol esterification reaction that was determined by electrospray ionization–mass spectrometry and gas chromatography–mass spectrometry. The reactions were carried out with sulfuric acid, phosphotungstic acid and in the absence of catalyst, using different acetylating agents (acetic acid and acetic anhydride). The phosphotungstic acid showed satisfactory performance in the catalytic esterification of glycerol when acetic acid and acid anhydride were used. The use of acetic anhydride as the acetylating agent favors the esterification reaction, decreasing the reaction time required for obtaining glycerol triacetate.     

In Situ Construction of Pt–Ni NF@Ni-MOF-74 for Selective Hydrogenation of p-Nitrostyrene by Ammonia Borane

Pt–Ni nanoframes (Pt–Ni NFs) exhibit outstanding catalytic properties for several reactions owing to the large numbers of exposed surface active sites, but its stability and selectivity need to be improved. Herein, an in situ method for construction of a core–shell structured Pt-Ni NF@Ni-MOF-74 is reported using Pt–Ni rhombic dodecahedral as self-sacrificial template. The obtained sample exhibits not only 100 % conversion for the selective hydrogenation of p-nitrostyrene to p-aminostyrene conducted at room temperature, but also good selectivity (92 %) and high stability (no activity loss after fifteen runs) during the reaction. This is attributed to the Ni-MOF-74 shell in situ formed in the preparation process, which can stabilize the evolved Pt–Ni NF and donate electrons to the Pt metals that facilitate the preferential adsorption of electrophilic NO₂ group. This study opens up new vistas for the design of highly active, selective, and stable noble-metal-containing materials for selective hydrogenation reactions.     

Recent topics of the natural product synthesis by Horner–Wadsworth–Emmons reaction

The Horner–Wadsworth–Emmons (HWE) reaction has become well established among existing methodologies for the highly stereoselective olefination of carbonyl compounds. The reliability of this reaction in terms of its robustness, high stereoselectivity, and broad substrate scope permit retrosynthetic disconnection of the olefin bond in α,β-unsaturated carbonyl intermediates in natural product synthesis. This review discusses recent applications of the HWE reaction in natural product synthesis, highlighting its use for carbon chain elongation, coupling reactions of synthetic segments, ring-closing reactions, tandem reactions including HWE olefination, and asymmetric reactions.     

The Dowd–Beckwith Reaction: History,Strategies, and Synthetic Potential

Ring-expansion strategies are valuable synthetic tools that take benefit of existing ring structures and evade the unfavorable enthalpic-and entropic effects that arise with end-to-end cyclizations. One potentially important class of such reactions is the Dowd–Beckwith reaction, the ring-expansion of ketones via alkoxy radicals. The exciting advancement in this research area is starting to show its potential, as demonstrated by applying this methodology in strategy-level bond formation to synthesize complex natural products. This Review aims to provide the first comprehensive survey of the development of the Dowd–Beckwith reaction spanning three decades from the initial report to the present day, thus providing the readers with great detail about the contributions of this reaction to organic synthesis. We hope that this review will further disclose the salient features of the Dowd–Beckwith reaction for synthetic applications and encourage the development of new, more advanced applications.     

Overcoming Thermodynamically Driven Retro-Diels–Alder Reaction through a Cascade One-Pot Process Exemplified for a Bio-Based Platform Chemical

In this contribution, we describe a new approach to apply thermodynamically unfavored reactions in synthetic chemistry and to integrate them in cascade processes. By means of a new developed procedure for multi-step one-pot syntheses, we succeeded in nearly completely converting a thermodynamically labile Diels–Alder adduct, which strongly tends to react back, to the target product with high conversion of >99 % and in excellent yield by coupling with a rapid subsequent hydrogenation reaction. In detail, the process is based on the use of a rotating reaction vessel to form a thin product film of the thermodynamically labile Diels–Alder product from 2-methylfuran and maleic acid anhydride (as two bio-based raw materials), which then slowly dissolves into solution and is immediately converted by hydrogenation to the target product. Such a combination of Diels–Alder reaction and hydrogenation in a sequential one-pot process without by-product formation enables the efficient production of the product, which represents a valuable bio-based platform chemical. In addition, this process concept generally opens a perspective for the integration of thermodynamically unfavorable reaction steps in multi-step one-pot cascade processes while obtaining the desired target products in high yields.     

A DFT study on the possibility of using a single Cu atom incorporated nitrogen-doped graphene as a promising and highly active catalyst for oxidation of CO

Using dispersion-corrected density functional theory (DFT) calculations, a single Cu adatom incorporated nitrogen-doped graphene (CuN₃-Gr) is proposed as a new and highly active noble-metal-free catalyst for carbon monoxide (CO) oxidation reaction. According to our results, the Cu adatom can be stably anchored onto the monovavancy site of the nitrogen-doped graphene, and the resulting large diffusion barrier suggests that the metal clustering is avoided in CuN₃-Gr. Three possible reaction mechanisms for CO oxidation (ie, Eley–Rideal, Langmuir–Hinshelwood, and termolecular Eley–Rideal) are systematically studied. It is found that the activation energy for the rate-determining step of the termolecular Eley–Rideal mechanism is only 0.13 eV, which is much smaller than those of others. The results of this study may provide a useful guideline for the design of highly active and promising single-metal catalysts for the CO oxidation reaction based on graphene.     

A group additivity methodology for predicting the thermochemistry of oxygen-containing organosilanes

A combinatorial approach was applied to devise a set of reference Si–C–O–H species that is used to derive group-additivity values (GAVs) for this class of molecules. The reference species include 62 stable single-bonded, 19 cyclic, and nine double-bonded Si–C–O–H species. The thermochemistry of these reference species, that is, the standard enthalpy of formation, entropy, and heat capacities covering the temperature range from 298 to 2000 K was obtained from quantum chemical calculations using several composite methods, including G4, G4MP2, and CBSQB3, and the isodesmic reaction approach. To calculate the GAVs from the ab initio based thermochemistry of the compounds in the training set, a multivariable linear regression analysis is performed. The sensitivity of GAVs to the different composite methods is discussed, and thermodynamics properties calculated via group additivity are compared with available ab initio calculated values from the literature.     

Stereoselective Cross-Coupling of Baylis–Hillman Acetates with Diphenyl Disulfides and Diselenides Using Palladium Acetate

An efficient method is described for the stereoselective synthesis of diorganyl chalcogenides from a variety of Baylis–Hillman acetates and diaryl chalcogens using palladium catalyst. This reaction is a convenient new method to produce unsymmetrical sulfides and selenides in good yields.     

Analysis of protein phosphorylation combining capillary electrophoresis with ATP analog labeling technique

Protein phosphorylation is one of the most basic mechanisms for regulating and controlling protein biological activity and function, and it is also a very important posttranslational modification process. Protein phosphorylation participates in and regulates many life activities such as signal transduction, gene expression, cell cycle, and so on. In this paper, we propose a method for the determination of the protein phosphorylation combining capillary electrophoresis (CE) with ATP analog labeling technique. We synthesized two new ATP analogs (ATP-NB and ATP-TATD-NB) functionalized by norbornene. Using Abl kinase as a model, we established a method for the determination of the kinase activity in solution and lysate by CE with laser-induced fluorescence detection (CE-LIF). This method was used to evaluate the efficiencies of kinase inhibitors. The IC₅₀ values obtained are basically consistent with the reports. By D–A reaction (inverse electron demand Diels–Alder reaction) to label TZ-BODIPY fluorescence, we also realized the phosphorylation fluorescence detection of substrate peptide. Then, we used fluorescence confocal microscopy imaging technology to study the phosphorylation of proteins in vivo by the D–A reaction of ATP-NB and TZ-BODIPY. Our preliminary results documented that the combination of CE-LIF with analog ATP-NB labeling technique is an effective strategy for the determination of the protein phosphorylation and the kinase activity and for screening of kinase inhibitors. The D–A reaction of ATP-NB and TZ-BODIPY also laid the foundation for the subsequent in situ study of protein phosphorylation.