Search

The present paper employs supported ruthenium nanoparticles alongside catalytic quantities of the radical initiator, which are proven to be capable of cyclooctene oxidation with green conditions, in the absence of solvent, with air as the main oxidant and without sacrificial reductant. The paper examines the effects of a range of radical initiators and how the products are distributed over time. Furthermore, the paper addresses the reaction pathways to the epoxides and allylic alcohol, the latter being the primary by-product, whilst also analysing the impact of the technique of synthesis, reaction time, and various supports. Catalyst activity can be markedly improved by adopting a sol-immobilization technique to synthesise the catalysts, with retention of selectivity to the epoxide.

The acid-catalyzed dehydration of regioisomeric methylcyclohexanols is a classic organic chemistry experiment featured in a variety of laboratory textbooks and literature. The mechanistic details of this reaction have received an inconsistent and occasionally inaccurate treatment, wherein the reaction has been described as a mix of E1, E2-like, acid-catalyzed E2, and base-catalyzed E2 processes. We provide an overview of how this reaction has been represented in the chemistry education literature and describe a model for its mechanistic interpretation as an E1 reaction that is typically analyzed before thermodynamic equilibrium is established. This model is supported by new experimental data and computational explorations of the reactive intermediates and cycloalkene products. We provide clear recommendations for how this reaction should be presented to students.

The synthesis of new cycloalkene annelated benzoxazocinones from N-tosyl- or N-mesyl-N-[2-(1-cycloalken-1-yl)phenyl]glycines was reported. Upon stirring of these glycines with bromine at room temperature, regardless of the size of the carbocyclic ring, benzo[e]cycloalk[g][1,4]oxazocinones were formed, in which an olefin moiety is induced between the C1=C11b or C1=C12b carbon atoms. The use of iodine for this purpose in the case of a cyclopentenyl derivative leads to a similar cyclization, while upon reaction of this halogen with a cyclohexenyl homologue forms a spiro-fused 2′-iodo[benzoxazepine-5,1′-cyclohexane].

This Account gives an insight into the selective functionalization of some readily available commercial cyclodienes across simple chemical transformations into functionalized small-molecular scaffolds. The syntheses involved selective cycloadditions, followed by ring-opening metathesis (ROM) of the resulting azetidin-2-one derivatives or isoxazoline frameworks and selective cross metathesis (CM) by discrimination of the C=C bonds on the alkenylated heterocycles. The CM protocols have been described when investigated under various conditions with the purpose on exploring chemodifferentiation of the olefin bonds and a study on the access of the corresponding functionalized β-lactam or isoxazoline derivatives is presented. Due to the expanding importance of organofluorine chemistry in drug research as well as of the high biological potential of β-lactam derivatives several illustrative examples to the access of some fluorine-containing molecular entities is also presented in this synopsis.1 Introduction2 Ring C=C Bond Functionalization of Some Cycloalkene β-Amino Acid Derivatives across Chlorosulfonyl Isocyanate Cycloaddition3 Ring C=C Bond Functionalization of Some Cycloalkene β-Amino Acid Derivatives across Nitrile Oxide Cycloaddition4 Ring C=C Bond Functionalization of Some Cycloalkene β-Amino Acid Derivatives across Metathesis5 Functionalization of sSome Cyclodienes across Nitrile Oxide Cycloaddition6 Selective Synthesis of Functionalized Alicycles across Ring-Opening Metathesis7 Selective Synthesis of Functionalized Alicycles through Cross Metathesis8 Summary and Outlook9 List of Abbreviations

Titanosilicates with extra-large pores or cages are expected to effectively release the diffusion constraints suffered by the bulky substrates in the hydrogen peroxide-involved liquid-phase selecti...

Derivatives of the new ring system benzo[f]pyrimido[1,2-d][1,2,3]triazolo[1,5-a][1,4]diazepinone and its cycloalkane and cycloalkene condensed analogues have been conveniently synthesized through a three-step reaction sequence. An atom-economical, one-pot, three-step cascade process engaging five reactive centers (amide, amine, carbonyl, azide, and alkyne) has been performed for the synthesis of alicyclic derivatives of quinazolinotriazolobenzodiazepine using cyclohexane, cyclohexene, and norbornene β-amino amides. The stereochemistry and relative configurations of the synthesized compounds were determined by 1D and 2D NMR spectroscopy and X-ray crystallography. The reaction was also performed using enantiomeric starting materials leading to enantiomeric quinazolinotriazolobenzodiazepine with an ee of 95%. The synthesis of 9H-benzo[f]pyrimido[1,2-d][1,2,3]triazolo[1,5-a][1,4]diazepinone, a new heterocyclic system, was achieved in a good yield using a retro Diels–Alder (RDA) procedure. Some compounds were tested for antiproliferative activities against five human cancer cell lines of gynecological.

The further processing of coconut shell pyrolysis into liquid smoke has been developed in recent years. However, the common technology by directly condensing the smoke has many impurity compounds which decreases the yield of liquid smoke produced. Hence, in this study the cyclone separator was applied to increase the quality of physicochemical content in coconut shell-liquid smoke (CS-LS) grade C. The physical parameters analyzed were yield, pH, density and color. The chemical parameters was analyzed by GC-MS. The result showed that CS-LS processing with cyclone separator was able to increase the total yield into 3.33%, with better color, pH and density compared to the CS-LS produced using common method (direct condensation). The application of cyclone separator was also able to increase the phenolic compounds (97%), alcoholic compounds (92%), cycloalkene compounds (91%) and also decreased the benzoic acid, carbonyl and ester up to 100% compared with common method for CS-LS grade C production.

Aliphatic polycarbonate (APC) macromolecular chain-transfer agents (macro-CTAs) with an allyl end group were successfully synthesized by cobalt-catalyzed epoxide/carbon dioxide copolymerization in the presence of allyl alcohol as a chain-transfer agent. The ring-opening metathesis polymerization of cycloalkene monomers using the obtained APC macro-CTAs yielded the corresponding APC-block-polycycloalkene copolymers. Thermal degradation temperatures of the APC blocks were found to be slightly higher (≈20 oC) than those of the block copolymers containing APC and vinyl-polymer blocks we have previously reported. Aliphatic polycarbonate (APC) macromolecular chain-transfer agents (macro-CTAs) with an allyl end group were successfully synthesized by cobalt-catalyzed epoxide/carbon dioxide copolymerization in the presence of allyl alcohol as a chain-transfer agent. The ring-opening metathesis polymerization of cycloalkene monomers using the obtained APC macro-CTAs yielded the corresponding APC-block-polycycloalkene copolymers.

The polymerization of commercial strained cycloalkene, 5-ethylidene-2-norbornene, in the presence of Pd–N-heterocyclic carbene complexes (two of which are synthesized for the first time) containing phosphine or pyridine ligands is studied. Upon activation with borate Na+[B(3,5-(CF3)2C6H3)4)]–, the studied Pd complexes catalyze the polymerization of 5-ethylidene-2-norbornene according to the addition scheme. Polymerization proceeds selectively and involves only the endocyclic (norbornene) double bond of the monomer, while the exocyclic (ethylidene) double bond remains unaffected. Pd–N-heterocyclic carbene complexes with phosphine ligands are inactive in polymerization, while similar complexes with 3-chloropyridine ligands show a higher activity. Two new Pd complexes are synthesized.

Scaffolds of thiophene and benzothiophene are the important class of bioactive compounds found abundant in nature. The Diels-Alder reactions of 2-(1'-cycloalkenyl)thiophenes and 2-(1'-cycloalkenyl)benzo[b]thiophenes having the alkene groups present in five-, six-, seven-, eight-, and twelve-membered rings with substituted N-phenylmaleimides are characterized. The size of the cycloalkene rings plays a critical role in dictating the product distributions of expected and isomerized Diels-Alder adducts. 2D NMR studies indicate that the isolated isomers for 2-(1'-cycloalkenyl)thiophenes having five-, six-, and seven-membered rings are aromatized benzothiophene products, whereas eight- and twelve-membered rings are un-rearranged adducts. In addition, the product of subsequent ene-reaction with the N-phenylmaleimide is isolated for the five- and six-membered ring cases. Interestingly, in the 2-(1'-cycloalkenyl)benzo[b]thiophene having five-, six-, seven-, eight-, and twelve-membered rings, the un-rearranged dibenzothiophene Diels-Alder adduct is isolated in every instance. Molecular mechanics and density functional theory (M06-2X and PBE0-D3) calculations are performed to understand the differential reactivity of the various dienes for both the initial Diels-Alder reaction and a possible, subsequent ene reaction.

The recently synthesized 9-borataphenanthrene anion (1) shows a reactivity in its central ring that resembles both a cycloalkene and an aromatic ring. Computational studies using the magnetic approach support these results. However, due to the limitations that the use of a single criterion can offer, a complete analysis was performed using multiple aromaticity criteria including magnetic, geometric, electron delocalization, reactivity and orbital localization in order to elucidate the nature of the six-membered rings in 1. Our results show that the outer rings in 1 exhibit an aromatic character similar to benzene, while the central ring is better described as an (cyclo)alkene. Additionally, it is shown that assessments using various criteria allow a complete understanding of aromaticity in polycyclic systems.

Haliranium ions are intermediates often involved in complex cyclisations, where their structure allows for control over stereospecific outcomes. Extending previous studies into their structure and reactivity in the gas phase, this work focuses on the bimolecular reactivity of ethyl bromiranium and iodiranium ions with cyclic alkenes. The products observed via mass spectrometry were broadly attributed to either addition by cyclohexene at the iranium carbon or attack at the heteroatom to undergo associative π-ligand exchange. The model proposed was supported by both kinetic experiments and DFT calculations, where the rate of parent ion consumption proceeded at the collision rate (Br: k2 = 1.25 × 10-9 and I: k2 = 1.28 × 10-9 cm3 molecule-1 s-1) with the subsequent partitioning dependent on the relative stability of the initial intermediates and the relatively large barriers present in the addition pathway. Exploration of the effect of cycloalkene ring strain on the iodiranium ion reactivity was conducted with a series of crossover experiments with 50 : 50 mixtures of either cyclohexene or cis-cyclooctene and styrene, where the outcomes were dependent on the competing ring strain relief gained by reaction with each neutral. The nature of the exchange transition state was determined to be pseudocoarctate following both natural bond orbital (NBO) and anisotropy of the induced current density (ACID) analysis.

The intermolecular interactions in cycloalkene-water adducts were computationally characterized, thus demonstrating that the primary O-H...pi(C=C) hydrogen bond is dominated by the electrostatic interaction. A deeper investigation by means of a joint rotational spectroscopy/state-of-the-art quantum chemistry approach also led to the determination of an accurate semi-experimental equilibrium structure for the cyclopentene adduct.

Tandem metathesis polymerization of terminal alkynes with a small functional ring-size cycloalkene remains a challenge. A series of 1-propargyl-1′-carboxylate ester monomers M1-M4 derived from 3-cyclopentene initiated by ruthenium-alkylidene complexes have been investigated via tandem polymerization. Detailed DFT calculations and end-group analysis using 1H NMR experiments provided us with a deeper insight into the proposed polymerization mechanism. The energy profile obtained from DFT analysis provides two pathways for the polymerization of monomers having both cycloalkene and alkyne functionalities. The most stable coordination of M was found to be via a π-coordination to the triple bond, which is oriented perpendicularly to the ruthenium-alkylidene bond. Both cycloalkene- and alkyne-initiated polymerizations were found to be feasible pathways. However, the alkyne-initiated polymerization mechanism was found to be the preferred pathway due to the higher stability of the alkyne coordination to the monomer and the slightly lower rate-determining step barrier. In addition, the synthesis of the model MC compound supported our proposed polymerization mechanism as well as the position of the styrene end-group on the polymer chain.

An efficient synthetic method of seven- and six-membered cycloalkenes through the generation of strained cycloalkynes and following carbomagnesiation is described. Further bond formations of the resulting cycloalkenylmagnesium intermediates with a wide variety of electrophiles enabled us to prepare diverse cycloalkene derivatives including benzoxepine analogs having a fully substituted alkene structure.

We previously reported that cyclohexene and bicyclo[4.2.0]oct-1(8)-ene-8-carboxamides undergo efficient ruthenium-catalyzed alternating ring-opening metathesis polymerization (AROMP). Here, we demonstrate that cyclodecene and cyclododecene also function as cycloalkene monomers in the bicyclo[4.2.0]oct-1(8)-ene-8-carboxamide AROMP system, thus enabling the synthesis of linear alternating copolymers with spacers of different lengths, as demonstrated by means of NMR spectroscopy and gel permeation chromatography. The glass transition temperature and hydrophilicity of the alternating copolymers decrease as the length of the spacers increases, as determined by differential scanning calorimetry and water contact angle measurements.

The reaction mechanism of the hydroxycarbonylation of cyclohexene with formic acid to form cyclohexanecarboxylic acid using organorhodium complexes was investigated both experimentally and computationally. It was found that excess CH3I and PPh3 promote this reaction. The active catalyst species was determined to be a five-coordinated rhodium hydride 16-electron complex derived from a mononuclear rhodium 16-electron complex (Vaska-type complex). PPh3 and CH3I played the following roles: i) to promote the formation of the Vaska-type Rh complex from Rh2Cl2(CO)4 (1), ii) to aid the elimination of the PPh3 ligand from the Vaska-type complex by stabilizing the free energy of formation of a mononuclear three-coordinated rhodium 14-electron complex through the formation of phosphonium iodide ([Ph3P(CH3)]I), and iii) to generate the active rhodium hydride species.

A bromo-capped metal-metal bonded diruthenium(i,i) complex Ru2(CO)4(PIN)2Br2 (1) (PIN = 1-isopropyl-3-(5,7-dimethyl-1,8-naphthyrid-2-yl)imidazol-2-ylidene) generates bromine with N-bromosuccinimide (NBS) at room temperature. Cycloalkene and stilbene are readily brominated by stoichiometric reactions with 1 and NBS. An analysis of the dibrominated products suggests the formation of cyclic bromonium intermediates indicating in situ Br2 generation. Complex 2, an iodide analogue of 1, is also synthesized. The reaction of 2 with N-iodosuccinimide releases I2, which is confirmed by the starch-iodine test. The catalytic utility of 1 is examined for the bromination of phenol. Catalyst 1, in combination with NBS and base, exhibits regioselectivity towards monobrominated products. Furthermore, efficient olefin aziridination is demonstrated utilizing catalyst 1 in the presence of NBS, K2CO3 and TsNH2.

From tryptamine and secologanine, nature generates monoterpene indole alkaloids with an unprecedented level of skeletal diversity through a 'couple-divert' sequence. Intrigued by this biosynthetic machinery, new strategies and tactics to access skeletally distinct natural products are continuously emerging. In this Tutorial Review, we'll present a simplified view of nature's logic for biosynthesis and the representative strategies and tactics developed for the divergent total synthesis of monoterpene indole alkaloids. Our group has been developing a 'couple-divert' approach with the strategic use of cycloalkene as a pluripotent motif in the synthetic design and has developed an integrated oxidation/reduction/cyclization (iORC) sequence for transforming functionalized cycloalkenes, easily available by a variety of cross-coupling reactions, to skeletally diverse natural products. The integration of controlled regio-, chemo- and stereo-selective cyclization and heteroannulation reactions into these domino sequences will be highlighted.

Titanium-containing zeolitic catalysts show high activity and selectivity in numerous environmentally-friendly oxidation reactions. However, the small micropores show severe restrictions for the oxidation of large organic reactants. Here, Ti-SFN zeolite with 14-ring extra-large-pores (6.2 × 8.5 A) was firstly synthesized by a chemical vapor deposition method and proved to have superior catalytic performance for bulker molecular oxidation using hydrogen peroxide as an oxidant compared to 10-ring TS-1 and 14-ring Ti-CIT-5 zeolites.

Tosylhydrazide was shown to be an effective reductant in protic solvents for the peroxide ozonolysis products of ∆3-carene, (–)-α-pinene, and (S)-limonene. Either α,ω-ditosylhydrazones or α,ω-ketotosylhydrazonoacids were formed depending on the nature of the trisubstituted cycloalkene.

Intramolecular photocycloaddition reactions of cycloalkene linked naphthalenes lead to formation of pentacyclic compounds in a high yielding and stereoselective manner. Intramolecular [2 + 2] cycloadducts are formed initially in photoreactions of cycloalkene linked 1-cyanonaphthalenes. The initially formed intramolecular [2 + 2] cycloadducts absorb light at wavelengths used to promote the photochemical reactions and, as a result, they undergo efficient photocycloreversion to regenerate the starting substrates. In a less efficient competing process, the cycloalkene linked 1-cyanonaphthalenes react to form [3 + 2] intramolecular photoadducts, which do not absorb incident light under the conditions used. Consequently, these photoadducts become the major products in these processes. The relative configuration of the major diastereomers of the pentacyclic products formed from photoreactions of cyclopentene linked naphthalenes ( cis - cis ) differ from those ( cis - trans ) arising from the cyclooctene linked substrates. The results of theoretical calculations, which show that steric factors govern the preferred facial mode of intramolecular addition, are in good agreement with the stereochemical course of these photoreactions.

International audience; Dicarboxylic acids constitute one of the most important oxygenated intermediates in the chemical industry providing a wide range of daily products: fibers, pharmaceuticals, cosmetics, lubricants, pesticides and plasticizers. A major part of their large-scale production relies on the oxidative cleavage processes of unsaturated acids and cyclic olefins but suffers from severe drawbacks such as the use of harmful compounds, the need of specific set-ups to produce oxidants, expensive catalysts and energy-consuming conditions. In the context of the development of sustainable oxidation reactions, hydrogen peroxide has attracted growing interest thanks to its multiple benefits to replace conventional oxidants: low toxicity, no need of energetic conditions to perform catalytic oxidation and generation of benign H2O as a by-product. The present review aims at bringing a critical view on the development of catalytic systems for the H2O2-mediated oxidative cleavage of cycloalkenes toward green chemistry criteria. Different transition metal-based catalysts investigated for the reaction will be discussed with a special emphasis on tungsten. Next, the performance of different heterogeneous and homogeneous W-based systems on the oxidative cleavage of various cycloolefins will be presented. More specifically, their relevance towards sustainable oxidation will be assessed by studying key reaction features: solvent, H2O2 amount, reaction time and catalyst synthesis, recoverability and activity. The main challenges regarding the oxidative cleavage of medium-sized cycloalkenes with W–H2O2 systems will also be exposed. Finally, the potential of ultrasound as an unconventional activation method will be pointed out to overcome the limits encountered with the conventional thermal heating leading to even more environmentally-friendly cycloalkene oxidative cleavage.

Iron(III)-catalyzed carbonyl-olefin ring-closing metathesis employs reactivity not typically observed in Lewis acid-catalyzed reactions. In converting a ketone with a pendant olefin into a cycloalkene and a simple carbonyl byproduct, the reaction requires the Lewis acid catalyst to differentiate between the carbonyl of the substrate and that of the byproduct. It is necessary to determine how this solution interaction imparts the desired reactivity to best employ this method. Herein, we report detailed kinetic, spectroscopic, and colligative measurements applied toward the identification of the solution structures of the active Fe(III) and Ga(III) carbonyl-olefin metathesis catalysts. These data are consistent with formation of Lewis acid-carbonyl pairs for both metal systems under stoichiometric conditions. However, they diverge in the presence of higher equivalents of carbonyl, with Fe(III) forming highly ligated complexes, and no observed change for Ga(III). These findings are consistent with the resting state identity of the Fe(III) metathesis catalyst changing over the course of the reaction.

Development of a novel synthetic method for medium-sized trans-cycloalkenes (TCAs) is described. Functionalized TCAs are readily prepared from simple cycloalkanones in a few steps, namely, enol silyl ether formation, [2+2] cycloaddition, and domino 4π electrocyclic ring opening/alkylation (conjugate addition). The first example of central-to-planar chirality transfer from enantiomerically enriched cyclobutenes to TCAs is also described.

This communication describes a novel series of linear and crosslinked polyurethanes (PUs) and their selective depolymerization under mild conditions. Two unique polyols are synthesized bearing unsaturated units in a configuration designed to favor ring-closing metathesis (RCM) to five- and six-membered cycloalkenes. These polyols are co-polymerized with toluene diisocyanate to generate linear PUs and trifunctional hexamethylene- and diphenylmethane-based isocyanates to generate crosslinked PUs. The polyol design is such that the RCM reaction cleaves the backbone of the polymer chain. Upon exposure to dilute solutions of Grubbs' catalyst under ambient conditions, the PUs are rapidly depolymerized to low molecular weight, soluble products bearing vinyl and cycloalkene functionalities. These functionalities enable further re-polymerization by traditional strategies for polymerization of double bonds. It is anticipated that this general approach can be expanded to develop a range of chemically recyclable condensation polymers that are readily depolymerized by orthogonal metathesis chemistry.

Bi-functional zeolite catalyst, incorporated with both organic groups and transition metal ions, has been firstly one-step synthesized by dry gel conversion method, which is characterized by powder XRD, solid-state 27Al, 29Si, 13C MAS NMR, FT-IR, Raman, UV–vis, X-ray photoelectron spectroscopy, and so on. Notably, the SiO/SiI ratio in the synthesis gel has important influence on the coordination state and distribution of cobalt species in the hybrid zeolite. Low SiO/SiI ratio has accelerated the formation of hybrid zeolite with tetrahedral framework cobalt while high SiO/SiI ratio has accelerated the additional assembly of hybrid zeolite with octahedral extra-framework cobalt. In the catalytic epoxidation of bulky cycloalkenes with air, hybrid zeolite with both tetrahedral framework cobalt and octahedral extra-framework cobalt shows the most excellent catalytic performance and TON value, compared with pure inorganic zeolite, hybrid zeolites with only tetrahedral framework cobalt species, and hybrid zeolites with Co species introduced by ion-exchange or wet impregnation methods, which is ascribed to the synergistic roles of organic groups and cobalt species. On one hand, the highly exposed octahedral extra-framework cobalt species act as an efficient supplement of tetrahedral framework cobalt, and the interactions of accessible catalytic active sites with bulky cycloalkene molecules have been strengthened greatly. On the other hand, mercaptopropyl groups are beneficial for the formation of stable heterogeneous catalyst with lipophilic surface through anchoring the extra-framework cobalt species and modifying the surface of the zeolite, which accelerate the epoxidation reaction efficiently.

Cholesteryl ester transfer protein (CETP) is a potential target for cardiovascular disease therapy as inhibition of CETP leads to increased HDL-C in humans. Based on the structure of Merck's biphenyl CETP inhibitor, we designed novel N,N-substituted-cycloalkenyl-methylamine scaffold derivatives by utilizing core replacement and conformational restriction strategies. Consequently, twenty-eight compounds were synthesized and evaluated for their inhibitory activity against CETP. Their preliminary structure-activity relationships (SARs) studies indicate that polar substituents were tolerated in moiety A and hydrophobic alkyl groups at the 5-position of cyclohexene were critical for potency. Among them, compound 17a, bearing an N-(5-pyrazolyl-pyrimidin-2-yl)-cycloalkenyl- methylamine scaffold, exhibited excellent CETP inhibitory activity (IC50 = 0.07 μM) in vitro. Furthermore, it showed an acceptable pharmacokinetic profile in S-D rats and efficient HDL-C increase in high-fat fed hamsters.

Nazarov cyclization is an important and versatile method for the synthesis of five-membered carbocycles, and extensive studies have been conducted to optimize the reaction. Among recent studies, several trends are recognized. One is the combination of different reactions with Nazarov cyclization in a one-pot reaction system which enables the preparation of unique cyclization products. The second is the use of a transition-metal catalyst, though Lewis or Brønsted acids have generally been used for the reaction. The third is the realization of the asymmetric Nazarov cyclization. The fourth is the base-catalyzed Nazarov cyclization. Furthermore, several useful protocols for realizing Nazarov cyclization have also been developed. The recent progress on Nazarov cyclizations is summarized in Section 2. Section 3 is our chronicle in this field. We focused on the use of iron as the catalyst in Nazarov cyclizations and ionic liquids as solvents: Nazarov cyclization of thiophene derivatives using FeCl3 as the catalyst was accomplished and we succeeded in demonstrating the first example of an iron-catalyzed asymmetric Nazarov reaction. We next established Nazarov cyclization of pyrrole or indole derivatives using Fe(ClO4 )3 ·Al2 O3 as the catalyst with high trans selectivities in excellent yields. Since the cyclized product was reacted with a vinyl ketone in the presence of the same iron salt, the system allowed realization of the sequential type of Nazarov/Michael reaction of pyrrole derivatives. Furthermore, we demonstrated the recyclable use of the iron catalyst and obtained the desired Nazarov/Michael reaction products in good yields for five repetitions of the reactions without any addition of the catalyst using an ionic liquid, [bmim][NTf2 ], as the solvent. We expect that the iron-catalyzed Nazarov cyclization, in particular, in an ionic liquid solvent might become a useful method to synthesize functional molecules that include cycloalkene moieties.

Gold-catalyzed imination/Mannich reaction cascades on readily available 3-en-1-ynamides enable the diastereoselective synthesis of 1,5-iminoamino compounds in a one-pot operation. The reactions work well with diversified 3-en-1-ynamides, aldehydes and anilines with good to excellent diastereoselectivities. Our control experiments indicate gold-catalyzed aminations of 3-en-1-ynamides to yield α-imino allylgold intermediates that react subsequently with iminiums to implement the Mannich reactions stereoselectively. The reactions proceed with anti-selectivity for those 3-en-1-ynamides bearing acyclic alkenes whereas syn-selectivity is seen for their cycloalkene-based analogues. An open-transition state can satisfactorily rationalize these observed stereoselectivities based on an antiperiplanar conformation.

To produce aromatic hydrocarbons from biomass, a novel route is reported for one-pot selective hydrodeoxygenation of a lignin derived aryl ether mixture to C6–C9 aromatic hydrocarbons over Ru/sulfate zirconia in the aqueous phase. The cascade steps undergo the initial precise cleavage of the Caliphatic–O bond of phenolic dimers or Caromatic–OCH3 of phenolic monomers, as well as the full blockage of benzene-ring and cyclic-alkene hydrogenation to realize nearly quantitative aromatic hydrocarbon formation at 240 °C in the presence of low pressurized H2 (2–8 bar). With a Ru catalyst, the primary and competitive steps in hydrogenolysis of the C–O bond and hydrogenation of the benzene ring are shown to be sensitive to temperature and hydrogen pressure, which can subtly modify the concentration and spatial distribution of the surface adsorbed H˙. A high temperature and a low hydrogen pressure are found to be essential for hydrogenolysis, since the H˙ species nearby the oxygen atom are more strongly adsorbed under such conditions and thus preferred to be retained on the Ru surface. Herein it is defined as the “atom-induced H sorption effect”, probably resulting from the analogous hydrogen-bond force between the adsorbed H˙ and the adjacent oxygen atom on the metal surface. Besides the initial step, another key point for aromatic hydrocarbon formation is to optimize the target route of cycloalkene dehydrogenation, but suppress the parallel hydrogenation pathway to saturated cycloalkanes. It is found that the produced phenol intermediate serves as a suitable H-acceptor for the selected catalytic system during the whole conversion, via fast consumption of the in situ produced H˙ from cyclohexene dehydrogenation. Such an interesting phenomenon of internal hydrogen transfer not only promotes the dehydrogenation and hydrogenation equilibrium of cyclohexene but also lowers the in situ H˙ concentration on the Ru surface, both of which would be beneficial for reaching a high benzene yield. This hypothesis for internal hydrogen transfer is further confirmed by separate experiments and density functional theory modelling results.

Sugar enol ethers undergo efficient coupling at C-2 with unactivated cycloalkenes under a low Pd loading affording allylic substitution products. High diastereoselectivity was observed at the allylic centre with sterically hindered substrates. Generation of a π-allyl complex by the Pd(II) catalyst via cleavage of the allylic C–H bond of the cycloalkene may be responsible for the formation of sp2–sp3 coupling products.

Renewable terpene biomass has attracting interest for producing high energy density fuel, particularly cycloalkane in the range of jet fuels. In this contribution, catalytic conversion of menthol to p-menthane was systematically investigated. Noble metals (Pt, Pd and Ru) supported on a Lewis-Bronsted acidic oxide (Nb2O5) were explored, considering the effects of reaction temperature and the balance between acid and metal sites. Catalysts kinetics were quite distinct, and Pd-based catalyst rendered the most active one. Yields of p-menthane of around 90% were determined over Pt and Pd catalysts, while it was only ~70% on Ru/Nb2O5, on which the formation of p-menthene was also observed. These results evidenced that the reaction proceeds as a cascade reaction at which acid-catalyzed menthol dehydration and metal-catalyzed cycloalkene hydrogenation lead to the aimed cycloalkane. Reaction temperature and the balance between acid and metal sites were shown to be the key aspects affecting catalyst performance.

Herein, we study the influence of ring size and number of carbon-carbon double bonds of cycloalkene on structure property relation of inverse vulcanized sulfur copolymers. Reaction kinetics was monitored by XRD and the copolymer structure was confirmed by 1H NMR and FTIR spectroscopy. DSC and TGA indicate the significant increase in Tg and thermal stability of the copolymer with increase in ring size and number of double bonds density; respectively. Thermal conductivity of the copolymers (0.083 W/mK at 50 °C) was also considerably reduced compared to the pristine sulfur, which make these copolymer suitable for thermal insulation applications. Moreover, these sulfur-rich copolymers can also be used as potential cathode materials in lithium-sulfur batteries.

Transition metal-mediated catalysis routinely enables substrates of multiple π-systems to be efficiently coupled with various carbon nucleophiles along with simultaneous ring formation. This transformation, however, remains unexplored in connection with pericyclic processes. Reported here is a protocol for cycloalkene synthesis based on the merger of rhodium catalysis and a retro-ene reaction. The approach allows alkyne-tethered hydrazones and organoboronic acids to undergo a cascade of addition–cyclization–rearrangement reactions to provide cycloalkene products. The process is initiated by the rhodium-catalyzed addition–cyclization and completed with the allylic diazene rearrangement. The reaction can also be rendered asymmetric by using chiral diene ligands for the rhodium catalyst, whereby enantioselective addition to the C═N bond establishes the C—N stereocenter whose chirality is transferred to an allylic C—H center via suprafacial rearrangement.

Recently, our group successfully developed two new polymerization methodologies for monomers containing two cycloalkene moieties. These polymerization methods yielded well-defined polymers via a combination of ring-opening and ring-closing metathesis (cascade polymerization) or ring-opening, ring-closing, and cross-metathesis (multiple olefin metathesis polymerization (MOMP)) using a second monomer. However, cascade polymerization had some limitations such as low polymerization efficiency (maximum turnover number (TON) of 250) and narrow monomer scope. Furthermore, one-shot MOMP also showed a very narrow monomer scope because of certain undesired side reactions. To overcome these problems, we designed various new monomers containing cyclopentene and even more challenging ring-strain-free cyclohexene moieties, so that polymerization would produce a thermodynamically favored six-membered-ring backbone repeat unit. With this enhanced driving force for polymerization, these new monomers successfully underwent cascade polymerization with a high polymerization efficiency, leading to a maximum TON of 1940 and maximum number-average molecular weight ( M

This work first reports high-efficiency epoxidation of large cycloalkenes (carbon number ≥ 7) with tert-butyl hydroperoxide (TBHP) over single-/double-/multi-unit-cell nanosheet-constructed hierarchical zeolite, which is synthesized by one-step hydrothermal crystallization using piperidine as the structure-directing agent of the microporous structure. The excellent catalytic property of the material is ascribed to its unique structural characteristic. Plenty of surface titanols or silanols on the surface of MWW nanosheets are beneficial for the formation of transition-state intermediates; a large number of intercrystalline mesopores in the shell of the material not only facilitate the formation of the intermediate for TBHP but also have nearly no hindrance for the diffusion and mass transfer of bulky cycloalkene to the above intermediates; the 12-MR side cups penetrating into the crystals from the external surface are exposed as much as possible to the reaction system because of the single-/double-/multi-unit-cell MWW nanosheet, serving as the primary reaction space for the epoxidation of bulky cyclic alkene and oxidants and providing enough space for the transition state of Ti-OOtBu and bulky cycloalkane. Moreover, an efficient calcination-free catalytic reaction-regeneration method is developed to overcome the challenge for the recyclability of microporous Ti-zeolite in the catalytic epoxidation of bulky cycloalkenes.

Benzene cis-diol dehydrogenase and naphthalene cis-diol dehydrogenase enzymes, expressed in Pseudomonas putida wild-type and Escherichia coli recombinant strains, were used to investigate regioselectivity and stereoselectivity during dehydrogenations of arene, cyclic alkane and cyclic alkene vicinal cis-diols. The dehydrogenase-catalysed production of enantiopure cis-diols, α-ketols and catechols, using benzene cis-diol dehydrogenase and naphthalene cis-diol dehydrogenase, involved both kinetic resolution and asymmetric synthesis methods. The chemoenzymatic production and applications of catechol bioproducts in synthesis were investigated. Fil: Boyd, Derek R.. The Queens University of Belfast; Irlanda Fil: Sharma, Narain D.. The Queens University of Belfast; Irlanda Fil: Berberian, Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. The Queens University of Belfast; Irlanda Fil: Cleij, Marcel. The Queens University of Belfast; Irlanda Fil: Hardacre, Christopher. The Queens University of Belfast; Irlanda Fil: Ljubez, Vera. The Queens University of Belfast; Irlanda Fil: McConville, Gareth. The Queens University of Belfast; Irlanda Fil: Stevenson, Paul J.. The Queens University of Belfast; Irlanda Fil: Kulakov, Leonid A.. The Queens University of Belfast; Irlanda Fil: Allen, Christopher C. R.. The Queens University of Belfast; Irlanda

Carbon nitride nanosheets decorated with WO 3 nanorods (WO 3 /g-C 3 N 4 ) were fabricated via ultrasonic-assisted dispersion and conventional incipient wetness impregnation method. It is found that ultrasonic promoted the formation of g-C 3 N 4 nanosheets efficiently. The promotion effect in the structural evolution and catalytic performance for the rod-like structure of WO 3 caused by g-C 3 N 4 nanosheets were well studied. For the first time, the novel WO 3 /g-C 3 N 4 nanocomposites were used as efficient catalysts in the green process of dialdehydes from the selective oxidation of cycloalkene oxides using H 2 O 2 as a clean oxidant, owing to the high dispersion of active sites and the strong interaction between cycloalkene oxides and the NH or NH 2 groups on the surface of g-C 3 N 4 sheets. Here, C 3 N 4 nanosheets are considered as the catalyst support and co-catalyst as well. The novel nanocomposites are very stable and can be reused for five times without obvious loss of catalytic activity.