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The present article presents a personal account on the synthesis of heterocycles by the combination of regioselective Pd-catalyzed cross-coupling reactions of polyhalogenated heterocycles, i.e., Suzuki–Miyaura and Sonogashira reactions, with alkyne-carbonyl-metathesis (ACM) reactions. The products, which show interesting optical, electronic or medicinal properties, are not readily available by other methods. [ABSTRACT FROM AUTHOR]

The carbonyl‐alkyne metathesis reaction is a powerful method for the synthesis of α,β‐unsaturated carbonyls. We now report on the development of a halogen‐bond catalyzed protocol for both the intra‐ and intermolecular reaction. Our studies revealed that methanol is a highly efficient solvent and that a very broad range of functional groups are tolerated under the reaction conditions. Mechanistic studies support the proposed halogen‐bond interaction. Furthermore, the halogen‐bond protocol is compared with other available catalytic systems for these reactions. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) offer vast structural and chemical diversity enabling a wide and growing range of applications. While COFs are well-established as heterogeneous catalysts, so far, their high and ordered porosity has scarcely been utilized to its full potential when it comes to spatially confined reactions in COF pores to alter the outcome of reactions. Here, we present a highly porous and crystalline, large-pore COF as catalytic support in α,ω-diene ring-closing metathesis reactions, leading to increased macrocyclization selectivity. COF pore-wall modification by immobilization of a Grubbs-Hoveyda-type catalyst via a mild silylation reaction provides a molecularly precise heterogeneous olefin metathesis catalyst. An increased macro(mono)cyclization (MMC) selectivity over oligomerization (O) for the heterogeneous COF-catalyst (MMC:O=1.35) of up to 51 % compared to the homogeneous catalyst (MMC:O=0.90) was observed along with a substrate-size dependency in selectivity, pointing to diffusion limitations induced by the pore confinement.

A facile and efficient synthesis of 3‐spiro cycloalkene fused 7‐aza‐2‐indalones from 3,3′‐di‐ or N,3,3′‐tri‐ allyl/homoallyl/pentenyl 7‐aza‐2‐indalones via ring‐closing metathesis (RCM) using Grubbs‐II catalyst has been achieved. The scope of the reaction has been demonstrated by synthesizing spiro products of various ring sizes (n=5, 7, and 18), utilizing 2‐indalone/7‐azaindalone and various alkenylation agents such as allyl/homoallyl/pentenyl bromides as substrates. In addition to usual RCM products, a cross metathesis (CM) product was observed when the substrate was N,3,3′‐triallylated derivative from 2‐indalone. Notably, a macrocyclic, 18‐membered bis‐spirodiene of N‐methyl‐7‐azaindalone was observed by means of intermolecular ring‐closing metathesis (RCM‐RCM). Also, Structures of a few representative spiro‐annulated products were evidenced with single crystal XRD analysis. Furthermore, a plausible mechanism for the products is discussed. [ABSTRACT FROM AUTHOR]

Light alkenes are among the main petrochemical intermediate products, the consumption of which is steadily growing. Using ethylene as an example, the possibilities of using polyfunctional heterogeneous catalysts for carrying out practically important reactions of its oligomerization, alkylation, and metathesis were considered. Particular attention was paid to catalysts for the conversion of ethylene to propylene. [ABSTRACT FROM AUTHOR]

This review highlights transborylation (controlled boron-boron exchange) and its applications as a turnover strategy in boron-catalysed methodologies. Catalytic applications of B –C, B –O, B –N, B –F, B –S, and B –Se transborylations are discussed in the context of transborylation-enabled catalysis, across a wide range of organic transformations including hydroboration, C–C bond formation, C–H borylation, chemoselective reduction, and asymmetric reduction. 1 Introduction 2 B –C Transborylation 3 B –O Transborylation 4 B –N Transborylation 5 B –F Transborylation 6 B –S Transborylation 7 Conclusion [ABSTRACT FROM AUTHOR]

Alkene metathesis catalyzed by enantiopure metal alkylidene complexes enables exceptionally versatile strategies to products with configurationally‐defined stereocenters. Desymmetrization processes thereby provide reliable stereoselective routes to aliphatic structures, while the differentiation of aromatic stereogenic units remained an outstanding challenge. Herein, we describe the feasibility of alkene metathesis to catalytically control stereogenic axes by traceless arene formation. Stereodynamic trienes are selectively converted into corresponding binaphthalene atropisomers upon exposure to a chiral molybdenum catalyst. Remarkably, stereoselective arene‐forming metathesis allows enantioselectivities of up to 98 : 2 e.r. and excellent yields. As the disconnection of each bond of an aromatic target is retrosynthetically conceivable, it is anticipated that forging arenes by means of stereoselective metathesis will enable versatile approaches for the synthesis of a broad range of molecular topologies with precisely defined configuration. [ABSTRACT FROM AUTHOR]

A new approach to access 1,3‐diene derived quinolinone compounds has been realized using a mild reaction protocol employing a metal free catalyst (1,2,3,5‐tetrakis(carbazol‐9‐yl)‐4,6‐dicyanobenzene) (4CzIPN), blue LED as activation source, and benefits from a sustainable solvent dimethylcarbonate (DMC). The mechanism is postulated as an amide‐tethered enyne intramolecular [2+2]‐photocatalyzed cycloaddition‐retrocycloaddition sequence, proceeding via a cyclobutene intermediate species. The methodology offers an efficient route towards decorated 1,3‐diene products. [ABSTRACT FROM AUTHOR]

A general modular enantioselective synthetic approach to the C(7)–C(18) and the C(7)–C(20) fragment belonging to E‐492, actinofuranone A, and JBIR‐108 was developed. The crucial synthetic step relies on highly enantioselective crotylboration of aldehydes catalyzed by a chiral TRIP PA giving rise to highly enantioenriched terminal alkenes (86 and 88 % ee on the preparative scale). The alkenes were subsequently converted into the title products. Further important synthetic steps included Ru‐catalyzed alkene cross‐metathesis and Suzuki coupling reactions. The approach consists of five synthetic steps starting from easily available aldehydes and other reaction partners. [ABSTRACT FROM AUTHOR]

A series of olefin metathesis catalysts bearing cyclic (alkyl)(amino)carbene (CAAC) ligands of varying size and steric demand has been synthesized and evaluated in ring‐closing‐, self‐, and cross‐metathesis reactions at room temperature. The catalysts were also probed for potential applications in dynamic covalent chemistry. The majority of the catalysts showed high stability, and remained active in the reaction mixtures for several days, including in methanol‐based solutions. Higher temperatures could be used to control the reactivity towards sterically challenging substrates, enabling formation of tetrasubstituted olefins. The CAAC complexes exhibited remarkable functional group tolerance towards heteroaromatic and nucleophilic additives, making them potentially useful in the screening of biologically active compounds. [ABSTRACT FROM AUTHOR]

Although the olefin metathesis reaction is a well‐known and powerful strategy to get alkenes, this reaction remained highly challenging with fluororalkenes, especially the Cross‐Metathesis (CM) process. Our thought was to find an easy accessible, convenient, reactive and post‐functionalizable source of fluoroalkene, that we found as the methyl 2‐fluoroacrylate. We reported herein the efficient ruthenium‐catalyzed CM reaction of various terminal and internal alkenes with methyl 2‐fluoroacrylate giving access, for the first time, to trisubstituted fluoroalkenes stereoselectively. Unprecedent TON for CM involving fluoroalkene, up to 175, have been obtained and the reaction proved to be tolerant and effective with a large range of olefin partners giving fair to high yields in metathesis products. [ABSTRACT FROM AUTHOR]

A synthetic protocol involving sequential use of three atom‐economic processes viz. Claisen rearrangement, ring‐closing metathesis and cross metathesis has been developed to access 7‐substituted benzo[b]azepine and benzo[b]oxepine derivatives starting from appropriate aniline or phenol in good overall yield. A one‐pot RCM‐CM protocol has also been developed for the synthesis of benzazepine and benzoxepine derivatives. [ABSTRACT FROM AUTHOR]

Commercialized catalysts are often needed in multiton quantities for industrial deployment. Although scalable, manufacturing methods to produce catalysts at quantity often produce materials with an ensemble of physical and chemical characteristics. This work explores an aerosol reactor to synthesize homogeneous, uniform catalyst materials in order to develop correlations between key chemical and physical characteristics and their resulting catalytic performance. With these insights, we optimize reactor processing conditions to engineer particles with the desired physical and chemical characteristics to produce enhanced performance catalysts. Control over several process parameters, including reactor residence time, temperature, precursor type, and precursor composition, allows for the rational determination of key physical and chemical characteristics on the resulting catalyst materials and enables process optimization to engineer catalysts with enhanced performance. To demonstrate the methodology, the aerosol reactor was used to synthesize and optimize WOx catalyst materials for the isomerization and metathesis of a 2‐butene feed into propylene. [ABSTRACT FROM AUTHOR]

Many organic-rich rocks are major sources of oil and gas in sedimentary basins presumably through high-temperature thermal cracking. This view was brought into question with recent reports of marine shales generating catalytic gas in the laboratory at 50²C, 300²C below thermal-cracking temperatures. Gas forms under natural conditions without artificial stimulation. Compositions of methane, ethane and propane are near thermodynamic equilibrium (2C2H6 =CH4 + C3H8) mirroring those in natural deposits. It is significant because thermal cracking can neither generate hydrocarbons at equilibrium nor can it bring them to equilibrium over geological time. Thus, catalysis must be the source of equilibrium in natural gas habitats and in marine shales. There is experimental evidence for metathesis (2Cn↔Cn-1 + Cn+1) as the catalytic path to equilibrium. However, it is without example in contemporary catalysis, and therefore, calls for extraordinary empirical support. Here, we report independent and unequivocal evidence of natural catalytic activity in a marine shale linking metathesis and thermodynamic equilibrium. A Cretaceous Mowry shale catalysed the dimerization of propylene (C3H6) to methyl cyclopentane (MCP, C6H12) and n-hexane (n-C6, C6H14) at 50²C in greater than 99 per cent selectivity. Propylene increased the rate of n-C6 generation by a factor of 100 with 100 per cent selectivity to the straight-chain hexane (n-C6). Propylene also suppressed the generation of all hydrocarbons except cyclopentane, MCP and n-C6. The ratio MCP/n-C6, which swung chaotically between 1 and 25 before propylene addition, was rendered invariant with propylene addition (R² =0.99; MCP/n-C6 =1.20 ± 0.034 s.d.). These uniquely catalytic reactions confirm natural catalytic activity in this shale. It appears to be 'palaeoactivity' possibly conceived in early diagenesis and sustained over geological time. [ABSTRACT FROM AUTHOR]

Compatibility of selected, commercially available ruthenium olefin metathesis catalysts with ethyl lactate as solvent was evaluated using a range of substrates and conditions. In addition, the preparation of a metathesis catalyst in simplified manner by using the advantages of ethyl lactate was accomplished. The application of ethyl lactate facilitates product isolation (also allowing for lower ruthenium contamination in crude metathesis products) and improves the overall green angle of olefin metathesis. [ABSTRACT FROM AUTHOR]

The carbonyl–olefin metathesis reaction has become increasingly important in organic synthesis due to its versatility in functional group interconversion chemistry. Recent developments in the field have identified a number of transition-metal and organic Lewis acids as effective catalysts for this reaction. Herein, we report the use of simple organic compounds such as N -iodosuccinimide or iodine monochloride to catalyze the carbonyl–olefin metathesis process under mild reaction conditions. This work broadens the scope of this chemical transformation to include iodonium sources as simple and practical catalysts. [ABSTRACT FROM AUTHOR]

Isomerizing olefin metathesis is currently undergoing a transformation from laboratory curiosity to powerful synthetic concept at the heart of orthogonal tandem catalysis. In this process, an isomerization catalyst continuously moves double bonds along carbon chains, while a metathesis catalyst scrambles the residues at the C−C double bonds. This cooperative action of two catalysts can be used to access single, defined products from a complex mixture of compounds. Alternatively, it enables the transformation of uniform starting materials into complex product blends with defined, tunable properties. This concept article highlights recent developments and potential applications of this fascinating reaction concept. [ABSTRACT FROM AUTHOR]

Although alkyne metathesis has been known for 50 years, rapid progress in this field has mostly occurred during the last two decades. In this article, the development of several highly efficient and thoroughly studied alkyne metathesis catalysts is reviewed, which includes novel well‐defined, in situ formed and heterogeneous systems. Various alkyne metathesis methodologies, including alkyne cross‐metathesis (ACM), ring‐closing alkyne metathesis (RCAM), cyclooligomerization, acyclic diyne metathesis polymerization (ADIMET), and ring‐opening alkyne metathesis polymerization (ROAMP), are presented, and their application in natural product synthesis, materials science as well as supramolecular and polymer chemistry is discussed. Recent progress in the metathesis of diynes is also summarized, which gave rise to new methods such as ring‐closing diyne metathesis (RCDM) and diyne cross‐metathesis (DYCM). Making and breaking triple bonds: The development of highly active alkyne metathesis catalysts and their recent applications in organic and natural product synthesis as well as supramolecular and polymer chemistry are highlighted in this Minireview. [ABSTRACT FROM AUTHOR]

Abstract: Metal‐catalyzed borylative cyclization reactions of polyunsaturated compounds allow concomitant formation of C−C and C−B bonds to provide cyclic boronates, which constitute synthetically useful intermediates. Recent developments using first‐row transition metals as catalysts provide fully atom‐economical reactions that follow mechanisms involving σ‐bond metathesis. [ABSTRACT FROM AUTHOR]

A new method is proposed for the synthesis of octadiene-1,7 by co-metathesis of ethylene and cyclohexene (ethenolysis). The reaction is carried out in a flow setup at elevated pressures using an original NH 4 ReO 4 /Al 2 O 3 heterogeneous catalyst. At the first stage of the reaction, carbenes are formed as intermediates. The optimal conditions of the co-metathesis process were found. The catalyst developed provides the cyclohexene conversion about 25 wt. %, i.e. close to the thermodynamic limit, at the selectivity to octadiene-1,7 close to 100% (99.9%). The catalyst shows good stability in six cycles including 5-h catalytic runs with intermediate regenerative treatments. [ABSTRACT FROM AUTHOR]

Abstract: In this perspective article, we discuss catalytic isodesmic reactions, a group of chemical reactions that proceed through the redistribution of chemical bonds – i. e. all bonds present in the starting materials are reformed in the products. These reactions are usually reversible and provide a complementary approach to the kinetically controlled strategies traditionally employed in chemical synthesis. To emphasize the power of these reactions across the molecular sciences, we present selected applications of these reactions in organic synthesis, chemical biology, biomass valorization, waste treatment, and materials science. We finally speculate that the development of novel catalytic isodesmic reactions beyond the “classics” (alkene/alkyne metathesis and transfer hydrogenation) holds great promise to solve crucial challenges in synthetic chemistry in the years to come. [ABSTRACT FROM AUTHOR]

[Display omitted] • MgO enhances the reactant conversion in self-metathesis of 1-butene or propylene. • MgO does not increase the propylene yield obviously for 2-butene and ethylene. • WO 3 /SiO 2 is strong enough to maintain trans -2-butene/ cis -2-butene in equilibrium. • MgO is helpful to transform 2-butene with 1-butene in equilibrium. • There is little difference in the reactivity between trans -/ cis -2-butene. Different feedstocks were adopted to undergo reactions catalyzed by WO 3 /SiO 2 and WO 3 /SiO 2 -MgO catalysts to better understand the effect of MgO on the process. The results of 1-butene self-metathesis show that, although the isomerization of 1-butene was clearly enhanced by MgO, the propylene selectivity was not improved because of insufficient 1-butene or ethylene. The main route to produce propylene in this system is through cross-metathesis of 1-butene and 2-butene. When propylene was used as the feed, more 2-butene, which was produced from propylene self-metathesis, was transformed into 1-butene by the addition of MgO, resulting in an improved metathesis performance between 1-butene and propylene. The cross-metathesis of 2-butene and ethylene, however, did not show an significant enhancement by MgO. In addition, the analysis on n -butene isomers distribution reveals that the presence of MgO is helpful in keeping the isomers at their theoretical values, leading to the good stability of the reactions. Lastly, a further comparison for the reactions between trans -2-butene and cis -2-butene demonstrates that there is little difference in their metathesis reactivity. [ABSTRACT FROM AUTHOR]