Aromatic‐Amide‐Derived Olefins as a Springboard: Isomerization‐Initiated Palladium‐Catalyzed Hydrogenation of Olefins and Reductive Decarbonylation of Acyl Chlorides with Hydrosilane

A highly efficient catalytic protocol for the isomerization of substituted amide‐derived olefins is presented that successfully uses a hydride palladium catalyst system generated from [PdCl₂(PPh₃)₂] and HSi(OEt)₃. The Z to E isomerization was carried out smoothly and resulted in geometrically pure substituted olefins. Apart from the cis–trans isomerization of double bonds, the selective reduction of terminal olefins and activated alkenes was performed with excellent functional group tolerance in the presence of an amide‐derived olefin ligand, and the products were obtained in high isolated yields (up to >99 %). Furthermore, the palladium/hydrosilane system was able to promote the reductive decarbonylation of benzoyl chloride when a (Z)‐olefin with an aromatic amide moiety was used as a ligand.     

C3‐Symmetric Trisimidazoline‐Catalyzed Enantioselective Bromolactonization of Internal Alkenoic Acids

A method for conducting enantioselective bromolactonization reactions of trisubstituted alkenoic acids, using the C₃‐symmetric trisimidazoline 1 and 1,3‐dibromo‐5,5‐dimethyl hydantoin as a bromine source, has been developed. The process generates chiral δ‐lactones that contain a quaternary carbon. The results of studies probing geometrically different olefins show that (Z)‐olefins rather than (E)‐olefins are favorable substrates for the process. The method is not only applicable to acyclic olefin reactants but can also be employed to transform cyclic trisubstituted olefins into chiral spirocyclic lactones. Finally, the synthetic utility of the newly developed process is demonstrated by its application to a concise synthesis of tanikolide, an antifungal marine natural product.     

A Rapid and Simple Method for Quantitative Aziridination from Aminobrominated Derivatives of Olefins under Solvent‐free and Mild Conditions

The urea‐catalyzed aziridination of 1,2‐vicinal haloamines derived from aminohalogenation of olefins has been developed. This rapid and simple method was carried out by simply grinding the solid mixture of the substrate, K₂CO₃ and catalytic amount of urea at room temperature in air. The reaction provides a protocol for quantitative preparation of aziridines in a large scope of aminohalogenated derivatives of olefins including α,β‐unsaturated ketones, α,β‐unsaturated esters and simple olefins. The possible mechanism involving an H‐bond promoting deprotonation has been suggested for this reaction.     

Tuning the Crystal Phase to Form MnGaOx-Spinel for Highly Efficient Syngas to Light Olefins

The oxide–zeolite (OXZEO) catalyst design concept has been demonstrated in an increasing number of studies as an alternative avenue for direct syngas conversion to light olefins. We report that face-centered cubic (FCC) MnGaO_x-Spinel gives 40 % CO conversion, 81 % light olefins selectivity, and a 0.17 g g_cat⁻¹ h⁻¹ space-time yield of light olefins in combination with SAPO-18. In comparison, solid solution MnGaO_x (characterized by Mn-doped hexagonal close-packed (HCP) Ga₂O₃) with a similar chemical composition gives a much inferior activity, i.e., the specific surface activity is one order of magnitude lower than the spinel oxide. Photoluminescence (PL), in situ Fourier-transform infrared (FT-IR), and density functional theory (DFT) calculations indicate that the superior activity of MnGaO_x-Spinel can be attributed to its higher reducibility (higher concentration of oxygen vacancies) and the presence of coordinatively unsaturated Ga³⁺ sites, which facilitates the dissociation of the C−O bond via a more efficient ketene–acetate pathway to light olefins.     

Regiospecific Intermolecular Aminohydroxylation of Olefins by Photoredox Catalysis

A simple and regiospecific aminohydroxylation of olefins by photoredox catalysis has been developed. N‐protected 1‐aminopyridinium salts are the key compounds and serve as amidyl radical precursors by the action of Ir photocatalysts, fac‐[Ir(ppy)₃] and [Ir(ppy)₂(dtbbpy)](PF₆) (ppy=2‐pyridylphenyl, dtbbpy=4,4′‐di‐tert‐butyl‐2,2′‐bipyridine). The present photocatalytic system allows for synthesis of vicinal aminoalcohol derivatives from olefins with various functional groups under mild reaction conditions with easy handling.     

Catalytic cracking of C<Subscript>5</Subscript> raffinate to light olefins over NaOH-treated ZSM-5

A series of ZSM-5 catalysts (ZSM-5 (X)) treated with different NaOH concentration (X = 0, 0.05, 0.1, and 0.2 M) were prepared for use in the production of light olefins (ethylene and propylene) through catalytic cracking of C₅ raffinate. The effect of NaOH concentration on their physicochemical properties and catalytic activity was investigated. It was found that textural and physicochemical properties of ZSM-5 (X) catalysts were strongly influenced by the NaOH concentration. Mesopore volume of ZSM-5 (X) catalysts increased with increasing NaOH concentration, while acidity of the catalysts decreased with increasing NaOH concentration. Conversion of C₅ raffinate and yield for light olefins (ethylene and propylene) showed the volcano-shaped curves with respect to NaOH concentration (X). This implies that NaOH treatment of ZSM-5 was an efficient method to produce light olefins through catalytic cracking C₅ raffinate, and that optimal NaOH concentration was required for maximum production of light olefins. Among the catalysts tested, ZSM-5 (0.05) catalyst showed the best catalytic performance due to its favorable porosity and acidity.     

Ethylene Oligomerization Catalyzed by MCl2(PPh3)2 Complex‐es/Ethylaluminoxane

The catalytic properties of MCl₂ (PPh₃)₂ (M = Fe, A; Co, B; Ni, C) in combination with ethylaluminoxane (EAO) as cocatalyst for ethylene oligomerization have been investigated. Treatment of the MCl₂ (PPh₃)₂ complexes with EAO in toluene generated active catalysts in situ that are capable of oligomerizating ethylene to low‐carbon olefins. The catalytic activity and product distribution were affected by reaction condition, such as reaction temperature, the ratios of Al/M and the reaction time. The activity of 1.70 × 10⁵ g oligomers/ (mol Co. h) for the catalytic system of CoCl₂(PPh₃)₂ with EAO at 200°C was observed, with the selectivity of 91.1% to C_4–10 olefins and 70.7% to C_4–10 linear α‐olefins.     

Kinetics of Oxidative Cracking of n-Hexane to Light Olefins using Lattice Oxygen of a VOx/SrO-γAl2O3 Catalyst

The kinetics of oxidative cracking of n-hexane to light olefins using the lattice oxygen of VO_x/SrO-γAl₂O₃ catalysts has been investigated. Kinetic experiments were conducted in a CREC Riser Simulator (CERC: Chemical Reactor Engineering Center), which mimics fluidized bed reactors. The catalyst's performance is partly attributed to the moderate interaction between active VO_x species and the SrO-γAl₂O₃ support. This moderate interaction serves to control the release of lattice oxygen to curtail deep oxidation. The incorporation of basic SrO component in the support also helped to moderate the catalyst's acidity to checkmate excessive cracking. Langmuir-Hinshelwood model was applied to formulate the rate equations. The intrinsic kinetic parameters were obtained by fitting the experimental data to the kinetic model using a nonlinear regression algorithm at a 95% confidence interval, implemented in MATLAB. n-Hexane transforms to olefins at a specific reaction rate of 1.33 mol/gcat.s and activation energy of 119.2 kJ/mol. These values when compared with other duplets (i. e., ki° and E_A) for paraffins to olefins, show that indeed olefins are stable products of the oxidative conversion of n-hexane over VO_x/SrO-γAl₂O₃ under a fluidized bed condition. Values of activation energy for all CO_x formation routes indicate that intermediate paraffins are likely to be cracked to form CH₄ than to be converted directly to CO_x. On the other hand, olefins may transform partly, and directly to CO_x (E₉=9.65 kJ/mol) than to form CH₄ (E₈=89.1 kJ/mol) in the presence of excess lattice oxygen. Overall, olefins appear to be stable to deep oxidation due to the role of SrO in controlling the amount of lattice oxygen of the catalyst at the reaction temperature.     

Regio- and stereoselective co-iodination of olefins using NH4I and Oxone

A simple, efficient, and environmentally benign protocol for the synthesis of vicinal iodohydrins and iodoesters from olefins using NH₄I and Oxone in CH₃CN/H₂O (1:1) and dimethylformamide (DMF) / dimethylacetamide (DMA), respectively, without employing a catalyst at room temperature is described. Regio- and stereoselective iodohydroxylation and iodoesterification of various olefins with anti fashion, following Markonikov’s rule, was achieved and the corresponding products were obtained in good to excellent yields. In addition, 1,2-disubstituted olefins afforded excellent diastereoselectivity.     

(+)‐Tartaric Acid‐Catalyzed High Regio‐ and Stereoselective Aminobromination of Olefins

(+)‐Tartaric acid‐catalyzed aminobromination of α,β‐unsaturated ketones, α,β‐unsaturated esters and simple olefins utilizing TsNH₂/NBS as the nitrogen/halogen sources at room temperature without protection of inert gases achieved good yields (up to 92% yield) of vicinal haloamino products with excellent regio‐ and stereoselectivity, even just 10% of (+)‐tartaric acid was used as catalyst. The regio‐ and stereochemistry was unambiguously confirmed by X‐ray structural analysis of products 2b and 12c . The electron‐rich and deficient olefins show significant differences in activity to the aminobromination reaction and give the opposite regioselectivities. The 21 cases have been investigated which indicated that our protocol has the advantage of a large scope of olefins. Additionally, tartaric acid as catalyst has the advantage of avoiding any hazardous metals retained in products.     

Selective Palladium‐Catalyzed Aminocarbonylation of Olefins to Branched Amides

A general and efficient protocol for iso‐selective aminocarbonylation of olefins with aliphatic amines has been developed for the first time. Key to the success for this process is the use of a specific 2‐phosphino‐substituted pyrrole ligand in the presence of PdX₂ (X=halide) as a pre‐catalyst. Bulk industrial and functionalized olefins react with various aliphatic amines, including amino‐acid derivatives, to give the corresponding branched amides generally in good yields (up to 99 %) and regioselectivities (b/l up to 99:1).     

Catalytic Asymmetric Bromination of Unfunctionalized Olefins with H2O as a Nucleophile

The dimeric cinchona alkaloid (DHQD)₂PHAL is used to catalyze an effective asymmetric bromohydroxylation of unfunctionalized olefins with H₂O as nucleophile an N‐bromobenzamide as a bromine source. A variety of optically active bromohydrins are formed with up to 88 % ee.     

Efficient Conjugate Addition of 1H‐Indoles to Electron‐Deficient Olefins Catalyzed by Silica‐Supported Sodium Hydrogen Sulfate (NaHSO4 ⋅ SiO2)

A simple, mild, rapid, and highly efficient method for the conjugate addition of 1H‐indoles to electron‐deficient olefins has been developed using NaHSO₄ ? SiO₂ as heterogeneous catalyst. The conversion proceeds at room temperature, and the corresponding Michael adducts are formed in good‐to‐excellent yields.     

Dinuclear Ru–Aqua Complexes for Selective Epoxidation Catalysis Based on Supramolecular Substrate Orientation Effects

Ru–aqua complex {[Ru^II(trpy)(H₂O)]₂(μ‐pyr‐dc)}⁺ is a powerful epoxidation catalyst for a wide range of linear and cyclic alkenes. High turnover numbers (TNs), up to 17000, and turnover frequencies (TOF), up to 24120 h^?1 (6.7 s^?1), have been obtained using PhIO as oxidant. This species presents an outstanding stereospecificity for both cis and trans olefins towards the formation of their corresponding cis and trans epoxides. In addition, it shows different reactivity to cis and trans olefins due to a substrate orientation supramolecular effect transmitted by its ligand scaffold. This effect together with the impressive reaction rates are rationalized using electrochemical techniques and DFT calculations.     

A simple method to prepare single isomer tetrasubstituted olefins by successive Suzuki–Miyaura cross-couplings of E-β-chloro-α-iodo-α,β-unsaturated esters

A convenient method of synthesizing tetrasubstituted olefins as single isomers is described. E-β-Chloro-α-iodo-α,β-unsaturated esters are first converted into the corresponding E-β-chloro-α,β-unsaturated esters using Suzuki–Miyaura coupling reactions with arylboronic acids and alkenylboronic acids. These transformations gave complete selectivity, and proceeded with substitution at the more activated α-iodide position. These compounds, isolated as single isomers, were then transformed into tetrasubstituted olefins by Suzuki–Miyaura couplings with arylboronic acids, alkenylboronic acids, and alkyl boranes to afford the corresponding tetrasubstituted olefins as single isomers. During this coupling process, it was discovered that the use of small ligands, such as PMe₃ or PEt₃, was critical for efficient coupling. The stereochemistry and regiochemistry of the products were unequivocally established using NMR methods.     

Alternating copolymer of butadiene and propylene. III

Alternating copolymerizations of butadiene with propylene and other olefins were investigated by using VO(acac)₂–Et₃Al–Et₂AlCl system as catalyst. Butadiene–propylene copolymer with high degree of alternation was prepared with a monomer feed ratio (propylene/butadiene) of 4. Alternating copolymers of butadiene and other terminal olefins such as butene-1, pentene-1, dodecene-1, and octadiene-1,7 were also obtained. However, the butadiene–butene-2 copolymerization did not yield an alternating copolymer but a trans-1,4-polybutadiene.     

Telechelic polynorbornenes with hydrogen bonding moieties by direct end capping of living chains

We present two novel symmetric olefins bearing hydrogen bonding moieties for the direct capping of living ring opening metathesis polymerization‐chains using Grubbs catalyst 1st‐ and 3rd‐generation. The symmetric olefins are generated via homo metathesis of the corresponding α‐olefins under aid of microwave irradiation and are used to prepare polynorbornene‐chains (M_n = 4,000–10,000 g/mol, M_w/M_n = 1.1–1.4) bearing barbiturate and thymine‐moieties. A qualitative and quantitative analysis of the generated polymers is done via MALDI‐TOF MS proving the introduction of hydrogen‐bonding moieties into the polymer chain and revealing the strong dependence of the desorption on the chemical structure of the different polymer species and high efficiencies for the end group introduction (90–99%). The efficiency of this process depends strongly on the reaction time and the equivalents of terminating agent with respect to the living end. The best results for the end group introduction are achieved by reacting the living chains with an excess of the terminating agent (5–20 equiv) for 100 h. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Increasing Olefin Metathesis Activity of Silica-Supported Molybdenum Imido Adamantylidene Complexes through E Ligand σ-Donation

Molybdenum imido adamantylidene complexes with different substituents on the imido ligand (dipp=2,6-diisopropylphenyl, Ar_F5=C₆F₅, and ^tBu) having distinct electron donating abilities were investigated for the metathesis of internal and terminal olefins, for both molecular and silica-supported species using standardized protocols. Here we show that surface immobilization of these compounds results in dramatically increased activity compared to their molecular counterparts. Additionally, we show that electron withdrawing imido groups increase the activity of the compound towards terminal olefins while they simultaneously decrease the ability to metathesize internal olefins. Furthermore, these systems also show high stability when used as initiators in olefin metathesis, although the species that display higher initial activity deactivate faster than those that show more a more moderate reaction rate at first. Our catalytic studies, augmented by DFT calculations, show that all investigated compounds have a remarkably small energy difference between the trigonal bipyramidal (TBP) and square planar (SP) configurations of the metallacyclobutane intermediates, which has previously been linked to high activity.     

Rhodium/Phosphine catalysed selective hydroformylation of biorenewable olefins

This work reports rhodium catalyzed selective hydroformylation of natural olefins like eugenol, estragole, anethole, prenol and isoprenol using biphenyl based Buchwald phosphine ligands (S‐Phos ( L ₁ ), t‐Bu XPhos ( L ₂ ), Ru‐Phos ( L ₃ ), Johnphos ( L ₄ ) and DavePhos ( L ₅ ). Ru‐Phos ( L ₃ ) ligand exhibited high impact on the hydroformylation of eugenol providing high selectivity (90%) of linear aldehyde as major product. In addition, internal natural olefins like anethole and prenol provided moderate to high selectivity (65% and 85% respectively) of branched aldehydes as a major products. The various reaction parameters such as influence of ligands, P/Rh ratio, syngas pressure, temperature, time and solvents have been studied. A high activity and selectivity gained on the way to the linear aldehydes it may be due to the bulky, steric cyclohexyl and isopropoxy groups present in L ₃ phosphine ligand. Moreover, this catalytic system was smoothly converting natural olefins into corresponding linear and branched aldehydes with higher selectivity under the mild reaction conditions.     

Convenient and Mild Epoxidation of Alkenes Using Heterogeneous Cobalt Oxide Catalysts

A general epoxidation of aromatic and aliphatic olefins has been developed under mild conditions using heterogeneous Co_xO_y–N/C (x=1,3; y=1,4) catalysts and tert‐butyl hydroperoxide as the terminal oxidant. Various stilbenes and aliphatic alkenes, including renewable olefins, and vitamin and cholesterol derivatives, were successfully transformed into the corresponding epoxides with high selectivity and often good yields. The cobalt oxide catalyst can be recycled up to five times without significant loss of activity or change in structure. Characterization of the catalyst by XRD, TEM, XPS, and EPR analysis revealed the formation of cobalt oxide nanoparticles with varying size (Co₃O₄ with some CoO) and very few large particles with a metallic Co core and an oxidic shell. During the pyrolysis process the nitrogen ligand forms graphene‐type layers, in which selected carbon atoms are substituted by nitrogen.