Ene Reaction Research Articles

Versatile stereoselective oxidative alkoxycarbonylation of styrenes at room-temperature

Carbonylation reactions carried out at room temperature and at atmospheric pressure of carbon monoxide are highly attractive and extremely rare at the same time. Here, the oxidative alkoxycarbonylation of styrenes to industrially relevant cinnamates has been developed under such a mild conditions (rt, 1 atm of CO) in the presence of a palladium(II) complex bearing a bis(aryl)acenaphthenequinonediimine ligand, benzoquinone and p-toluenesulfonic acid. Remarkably, variously substituted styrene derivatives have been efficiently carbonylated using a nearly stoichiometric amount of alcohols, with a dramatic reduction of waste. Even reluctant internal alkenes have shown to be compatible under these carbonylative conditions. In consideration of experimental results and DFT calculations a mechanistic rationale has been proposed. Based on this study, the benzoquinone has been found to promote the final palladium reoxidation, and to boost the reaction under such unprecedent mild conditions. The present methodology has been successfully exploited for the synthesis of high value-added cinnamoyl glycerols and cinnamic acid sugar esters, including the 6-O-p-coumaroyl-D-glucose natural product.

Selective removal of acid sites in mordenite with the assistance of tetraethylammonium bromide for high performing dimethyl ether carbonylation reaction

The distribution of acid sites in Mordenite (MOR) is crucial for its carbonylation performance. In this paper, MOR was subjected to acid treatment to selectively remove acid sites in 12 member-ring (MR) with the assistance of tetraethylammonium bromide (TEABr) used during synthesis process. The impact of acid treatment on structure, morphology, framework atoms and acidity were systematically studied. The characterization results indicated that the structure of the samples was only slightly impacted while the mesopore volume slightly increased. Due to the excessive removal of acid sites, the sample treated by nitric acid (0.1 mol/L) exhibited lower carbonylation activity whether with or without the protection of templates. However, the acid sites in the 12 MR were selectively removed in the citric acid treatment process by two different ways: the etching effect of H+ and the complexation of citric ions. The protection effect of templates for the acid sites in 8 MR was remarkable. Therefore, selective removal of acid sites in 12 MR was successful realized with assistance of template, leading to considerable improvements in activity for DME carbonylation reaction.

Unveiling the Catalytic Role of Zeolite P1 in Carbonylation Reaction

Unveiling the Catalytic Role of Zeolite P1 in Carbonylation Reaction

Reactivity of Enyne-Allenes Generated via an Alder-Ene Reaction.

Tandem transformations of 1,3-diynyl propiolate derivatives are described. The Alder-ene reaction generates an enyne-allene, which undergoes a formal 1,7-H shift or a Diels-Alder reaction, depending on the substituent on the alkyne. A terminal or aryl-substituted alkyne promotes a 1,7-H shift to generate a new enyne-allene, which undergoes a Myers-Saito cycloaromatization followed by a 1,5-H transfer-mediated cyclization to form highly functionalized benzo-fused 6-membered cycles. The reactivity of the preformed enyne-allene shows comparable reactivity profiles.

Solid-state NMR study of the stability of MOR framework aluminum

MOR zeolite has been effectively utilized for dimethyl ether (DME) carbonylation reaction due to its unique pore structure and acidity. During industrial production, the transformation of ammonium type MOR zeolite (NH4-MOR) into proton type MOR zeolite (H-MOR) causes inevitable dealumination. Therefore, understanding the influencing factors and dynamic evolution mechanism of zeolite dealumination is crucial. In this work, the stability of framework aluminum was studied by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, 29Si, 27Al, 1H magic angle spinning nuclear magnetic resonance (MAS NMR), and DME carbonylation performance evaluation. These results indicate that extra-framework cation Na+ and NH4+ could better preserve the aluminum structure of the MOR zeolite framework compared to H+, primarily due to the different ‘attraction’ of the framework to water. Furthermore, the impact of water on the zeolite framework aluminum at high temperature was studied by manipulating the humidity of the calcination atmosphere, revealing the formation of extra-framework six-coordinated aluminum (Al(VI)-EF) and the mechanism of water influence on the zeolite framework aluminum.

Asymmetric Total Synthesis of Pedrolide.

The asymmetric total synthesis of pedrolide (>200 mg) with an unprecedented [5-5-5-6-6-3] hexacyclic core (pedrolane) was achieved. Its unique bicyclo[2.2.1]heptane ring system was efficiently constructed via an enantioselective ene reaction of cyclopentadiene followed by a Wittig reaction, isomerization, and a diastereoselective intramolecular Diels-Alder reaction cascade. The highly oxygenated carane [6-3] ring system was synthesized via a ring-closing metathesis reaction followed by an unusual free carbene cyclopropanation. Furthermore, the 12 contiguous stereocenters of pedrolide were installed diastereoselectively.

A Sustainable and Versatile Cellulose-based CO Surrogate for Carbonylative Reactions.

The highly toxic and flammable nature of CO lead to high handling demand for its use and storage, undoubtedly constricting its further academic exploration for carbonylative reactions in laboratory. Although many CO surrogates have been developed and applied in carbonylative reactions instead of CO gas, exploration of more versatile CO surrogates for diverse carbonylations is still highly desirable. Here we report a cellulose-based CO surrogate (cellulose-CO), which prepared from cheap and abundant cellulose through a simple and green process. The very mild and efficient CO release makes this reagent a highly competitive candidate for providing CO in carbonylation. This surrogate is compatible with a wide variety of functional groups in various carbonylative reactions due to the excellent compatibility of cellulose-CO. Moreover, the cellulose-CO exhibits excellent chemical stability which can be stored exposed to air for 12 months, making this CO surrogate a robust and general reagent in CO chemistry.

Generation and transformation of α-oxy carbene intermediates enabled by copper-catalyzed carbonylation

Since the Fischer-Tropsch reaction was discovered by Otto Roelen in 1938, transition metal-catalyzed carbonylation reactions come in as one of the most important methods for preparing carbonyl-containing and carbon chain-increased compounds. As a result, the field of carbonylation research has received considerable attention over the past decades and continues to increase. With the continuous development of carbonylation and the in-depth study of the mechanism, more mechanistic details and variations have been revealed, which provide more possibilities for organic synthesis. Recently, copper catalysis has been introduced to the carbonylative functionalization of alkenes, thus enabling the rapid assembly of functionalized carbonyl compounds from simple starting materials. In this Account, we summarize the new findings in the Cu-catalyzed borocarbonylation of alkenes based on the generation and transformation of α-oxy carbene intermediates. We believe that the results presented in this Account will further inspire the design of new carbonylation reactions.

A new aspect of metabolic disorders in obesity: carbonyl stress

The literature review examines the problem of obesity in modern society. It has been shown that obesity aggravates concomitant diseases, increases the probability of developing metabolic disorders and related pathologies, increases the risk of complications and mortality. The secretory function of adipose tissue, its participation in the regulation of biological processes is considered in detail. The concept of carbonyl stress and its components is revealed, the role of carbonyl compounds in the body is described, the metabolic pathways leading to the formation of carbonyl reaction products are shown, the participation of free radicals in these metabolic pathways is noted. The mechanisms of pathogenesis associated with the development of carbonyl stress in obesity are discussed; the greatest contribution to the development of car bonyl pathology in obesity is made by two types of processes: lipid peroxidation reactions resulting in the formation of carbonyl products of lipoperoxidation and the processes activated by hyperglycemia (glycolysis, polyol and hexоzamine pathways) leading to the formation of glyoxal, methylglyoxal, and active carbonyl forms of glucose. The question of the contribution of advanced glycation end products (AGEs) and advanced oxidation protein products (AOРР) to the development of carbonyl pathology in obesity remains controversial. It is assumed that AGEs and AOРР levels depend on the severity of obesity and the development of metabolic syndrome.

Carbonylation of Boranes – A Computational Study

AbstractThe classical simple picture of stepwise B‐to‐C migratory insertion of all three alkyl groups in the carbonylation reaction of trialkyl boranes with CO was shown not to be correct, except for the first alkyl group shift affording an acyl borane. The second and third direct alkyl shifts turned out to be kinetically hampered due to the non‐activated character of the B−C bond in electron‐poor B atoms. The latter can only be achieved by either the autocatalytic action of the final alkyl boron oxide or by formation of dimeric species with weakened B‐alkyl bonds at borate centres. Both thermodynamic and several NICS‐related parameters pointed to scarce, even “negative”, aromatic character for boroxines, the final cyclotrimerization products of alkyl‐boron oxides.

Copper-Catalyzed Carbonylation Reactions: A Personal Account

AbstractCarbonylation reactions have been widely used to construct carbonyl-containing molecules or carbon enhancement reactions, which are mostly catalyzed by noble metals (Pd, Rh, Ru, Ir). In this review, we introduce the copper-catalyzed carbonylation reactions that have been developed in our group. Diverse reactions have been developed using various substrates, including the carbonylation of C–H activated alkanes, the difunctionalization of unsaturated C–C bonds, and the carbonylation of alkyl halides via the radical pathway.1 Introduction2 Cu-Catalyzed Carbonylation of C(sp 3)–H Bonds3 Cu-Catalyzed Carbonylative Difunctionalization of Unsaturated Bonds4 Cu–X (H or B) Mediated Acylation of Unsaturated Bonds with Electrophiles5 Cu–X (H or B) Mediated Carbonylation of Unsaturated Bonds6 Cu-Catalyzed Carbonylation of Alkyl Halides7 Other Types of Copper-Catalyzed Carbonylation Reactions8 Conclusion and Outlook

Domino dehydration/intermolecular (enantioselective) ketone-ene reactions catalysed by a simple solid in batch and in flow.

The intermolecular carbonyl-ene reaction of ketones is still considered a challenge in organic chemistry, particularly with reusable solid catalysts, and implemented in a domino reaction. Herein, we show that the extremely cheap and non-toxic solid salt MgCl2 catalyzes the reaction of trifluoromethyl pyruvates not only during the conventional carbonyl-ene reaction with various aromatic and alkyl alkenes (in very high yields, up to >99%) but also in a domino reaction with the corresponding alcohols (precursors to the alkenes) in similar good yields. The solid can be reused in both cases without any erosion of the catalytic activity and can be employed in an in-flow process to maximize the reaction throughput. Besides, the reaction can be performed under solventless reaction conditions. Addition of a catalytic amount of chiral binaphthyl hydrogen phosphate allows carrying out the reaction with a reasonable enantiomeric excess (up to >70%) and in flow, in a rare example of enantioselective solid-catalyzed domino carbonyl-ene reaction using a cheap, simple, readily available and physically mixed catalytic solid. The MgCl2-catalytic system is also active in the industrially relevant citronellal-to-isopulegol carbonyl-ene reaction. These results pave the way to design sustainable domino carbonyl-ene reactions with extremely cheap solid catalysts.

Nitroso-azomethine(ene) reaction enabled annulations of nitrosoarenes, azomethines and alkenes.

An unprecedented example of a nitroso-azomethine(ene) reaction is reported. Nitroso-azomethine(ene) reaction-mediated unprecedented annulation of nitrosoarenes, azomethines, and alkenes to furnish arylquinolines via arene functionalization of nitrosoarene has been developed. DFT studies provided mechanistic insights into the newly developed nitroso-azomethine(ene) reaction.

Palladium-catalyzed desulfonylative carbonylation reaction of benylsulfonyl chlorides with anthranils for the synthesis of 3-arylquinoin-2(1H)-ones

A direct and efficient palladium-catalyzed desulfonylative carbonylation reaction for the synthesis of 3-arylquinoin-2(1H)-ones has been disclosed. The reaction proceeds with a rapid elimination of SO2 process by employing benzylsulfonyl chlorides as effective C(sp3) electrophiles, with anthranils as the N-source, a variety of 3-arylquinoin-2(1H)-ones were obtained in moderate to high yields. This protocol provides a good supplement for applying benzylsulfonyl chlorides as C(sp3) electrophiles in carbonylation reactions.

The effect of the DNA support on Pd/DNA catalyzed organic transformations

DNA-supported palladium catalysts (Pd/DNA) have been used in imination, hydrogenation, cross-coupling, and carbonylation reactions. In this mini review, the effectiveness of Pd/DNA catalysts and the impact of the DNA support on the reusability of palladium in recent years has been examined.

Synthesis of hierarchical mordenite by solvent-free method for dimethyl ether carbonylation reaction.

A series of hierarchical mordenite (MOR) catalysts were synthesized by adding soft templates via the solvent-free method. The influence of different kinds of soft templates on the structure, morphology and acid sites of mordenite were systematically characterized. The characterization results revealed that the addition of soft templates could successfully introduce hierarchical structure into the system while maintaining good crystallinity. The specific surface area and pore volume became larger. Surfactants could also affect the amount and distribution of acid sites, which in turn would affect the dimethyl ether carbonylation activity. Compared with cationic and nonionic surfactants, the addition of anionic surfactants such as sodium dodecyl benzene sulfonate could result in more Al species to preferentially enter into the 8 member ring, thus enhancing the amount of active sites for the carbonylation reaction while weakening the strength. Meanwhile, the addition of sodium dodecyl benzene sulfonate could also reduce the number of strong acid sites in the 12 member ring and obviously improve the carbonylation performance.

Crucial size effect on dicarbonylation of acetylene over Pd/CsHPMo heterogeneous catalysts

Structure-sensitive activity of Pd catalyst in carbonylation reaction is an urgent problem to be explored. Herein, Pd nanocrystals with uniform particle size (2.3 nm, 3.4 nm, 5.0 nm and 6.7...

Copper-catalyzed carbonylative multi-component borylamidation of alkenes for synthesizing γ-boryl amides with CO as both methylene and carbonyl sources.

A multi-component carbonylation reaction is an efficient strategy for the synthesis of valuable carbonyl compounds from simple and readily available substrates. However, there remain challenges in carbonylation reactions where two CO molecules are converted to different groups in the target product. Considering the merit of complex amides, we reported here a copper-catalyzed multi-component borylamidation for the synthesis of γ-boryl amides. This method provides access to a wide range of functional γ-boryl amides from alkenes, amines, B2pin2, and CO with good yields and excellent diastereomeric ratios. Notably, two CO molecules were converted to methylene and carbonyl groups in the target amides. A series of amines were successfully involved in the transformation, including arylamines, aliphatic amines, and hydrochloride salts of secondary aliphatic amines.

Pyridine-catalyzed ring-opening reaction of cyclopropenone with bromomethyl carbonyl compounds toward furan-2(5H)-ones.

We developed a pyridine-catalyzed annulation of diaryl cyclopropenone with bromomethyl carbonyl compounds leading to 5-carbonyl furan-2(5H)-ones. Pyridinium, derived from the reaction of bromomethyl carbonyl and pyridine, triggered the reaction by the inter-molecular Michael addition to cyclopropenone. This procedure was sensitive neither to air nor moisture and proceeded at room temperature with broad substrate scopes and good functional group tolerance in moderate-to-good yields. As such, it represents a facile and practical pathway leading to 5-carbonyl furan-2(5H)-one derivatives.

Nickel-catalysed highly regioselective synthesis of β-acyl naphthalenes under reductive conditions.

Over the past decade, significant progress has been made in the direct C-H acylation of naphthalenes, occurring at the α or β-positions to yield valuable ketones through Friedel-Crafts acylation or transition-metal-catalysed carbonylative coupling reactions. Nevertheless, highly regioselective acylation of naphthalenes remains a formidable challenge. Herein, we developed a nickel-catalysed reductive ring-opening reaction of 7-oxabenzonorbornadienes with acyl chlorides as the electrophilic coupling partner, providing a new method for the exclusive preparation of β-acyl naphthalenes.