Subsequent Metathesis Reaction Research Articles

Reaction path search for propane dehydrogenation and metathesis on titanium hydride

Abstract The reaction mechanisms of C3H8 dehydrogenation and subsequent metathesis on a TiH2 surface were investigated using an automated reaction path search method. The predicted pathway suggests that dehydrogenation could occur at the H vacancies present on the TiH2 surface. The propylidene species formed by the initial dehydrogenation reaction are crucial intermediates in butane formation; this compound is in turn required by the subsequent metathesis reaction on the surface of the metal hydrides.

A Green Route to Benzyl Phenyl Sulfide from Thioanisole and Benzyl Alcohol over Dual Functional Ionic Liquids.

Benzyl phenyl sulfide is a kind of important chemicals with wide usage, which is mainly prepared through a nucleophilic reaction of thiophenol with benzyl chlorides or benzyl alcohols, suffering from inherent drawbacks, such as low efficiency, requirements for equivalent acid or base catalysts and formation of harmful byproducts and waste. Herein, we report a green route to access various benzyl phenyl sulfide derivatives in good to excellent yields under mild conditions via the reaction of thioanisoles with benzyl alcohols over ionic liquid 1-propylsulfonate-3-methylimidazolium trifluoromethanesulfonate ([SO3 HPrMIm][OTf]). Mechanism investigation indicates that the synergic effect of cation and anion of [SO3 HPrMIm][OTf] activates thioanisoles and benzyl alcohols via hydrogen bonding, thus catalyzes the dehydration of benzyl alcohol to dibenzyl ether and the subsequent metathesis reaction between dibenzyl ether and benzyl phenyl sulfide, finally generating benzyl phenyl sulfide derivatives. This is a simple, highly efficient, and green approach to produce benzyl phenyl sulfide derivatives, which has promising application potentials.

A Modular Approach to the Antifungal Sphingofungin Family: Concise Total Synthesis of Sphingofungin A and C.

Sphingofungins are fungal natural products known to inhibit the biosynthesis of sphingolipids which play pivotal roles in various cell functions. Here, we report a short and flexible synthetic approach towards the sphingofungin family. Key step of the synthesis was a decarboxylative cross‐coupling reaction of chiral sulfinyl imines with a functionalized tartaric acid derivative, which yielded the core motif of sphingofungins carrying four consecutive stereocenters and a terminal double bond. Subsequent metathesis reaction allowed for the introduction of different side chains of choice resulting in a total of eight sphingofungins, including for the first time sphingofungin C (eight steps from commercially available protected tartaric acid with an overall yield of 6 %) and sphingofungin A (ten steps). All newly synthesized derivatives were tested for their antifungal, cell‐proliferative and antiparasitic activity unraveling their structure–activity relations.

A Modular Approach to the Antifungal Sphingofungin Family: Concise Total Synthesis of Sphingofungin A and C

AbstractSphingofungins are fungal natural products known to inhibit the biosynthesis of sphingolipids which play pivotal roles in various cell functions. Here, we report a short and flexible synthetic approach towards the sphingofungin family. Key step of the synthesis was a decarboxylative cross‐coupling reaction of chiral sulfinyl imines with a functionalized tartaric acid derivative, which yielded the core motif of sphingofungins carrying four consecutive stereocenters and a terminal double bond. Subsequent metathesis reaction allowed for the introduction of different side chains of choice resulting in a total of eight sphingofungins, including for the first time sphingofungin C (eight steps from commercially available protected tartaric acid with an overall yield of 6 %) and sphingofungin A (ten steps). All newly synthesized derivatives were tested for their antifungal, cell‐proliferative and antiparasitic activity unraveling their structure–activity relations.

1,3,4,5-Tetraamino-1,2,4-triazolium Cation: An Energetic Moiety.

The amination of 3,4,5-triamino-1,2,4-triazole with O-tosylhydroxylamine yielded the nitrogen-rich 1,3,4,5-tetraamino-1,2,4-triazolium cation as its tosylate salt. Subsequent metathesis reactions produced energetic salts with various energetic anions, including perchlorate, nitrate, nitrotetrazolate, and bistetrazolate diolate. All energetic salts possess relatively high heats of formation, thermal sensitivities, and detonation velocities and pressures. The prepared energetic salts were characterized chemically using single-crystal X-ray crystallography, elemental analysis, and 1H NMR, 13C NMR, and IR spectroscopy and energetically by measuring their thermal, impact, and friction sensitivities. 15N NMR was carried out on the tosylate salt. Energetic performances were determined by a combined experimental-computational method using calculated heats of formation and experimental crystal densities.

Well-Defined Scandacyclopropenes: Synthesis, Structure, and Reactivity.

Although transition metallacyclopropenes have been extensively explored for more than 40 years, their analogues of rare-earth metals have remained elusive. Herein, we report the synthesis of three isolable scandacyclopropenes, thus representing the first well-defined rare-earth metallacyclopropenes. Structural characterization and DFT calculations revealed a delocalized three-center two-electron (3c-2e) aromatic system. When scandacyclopropenes were treated with phenylacetylene or TMSN3, the scandium complex of bis-phenylacetylide or bis-azide was obtained, respectively. The reaction of scandacyclopropene with phenazine could provide the binuclear ring-opening scandium complex via 1,4-insertion of phenazine into one Sc-C bond and subsequent metathesis reaction. However, insertion of TMSNCO or N2O into one Sc-C bond of scandacyclopropenes gave a five- or six-membered scandacycle. In addition, scandacyclopropenes can serve as a two-electron reductive agent for PhSSPh and PhNNPh. These results show that scandacyclopropenes exhibit diversified and unique reactivity toward small molecules because of the strongly nucleophilic alkenediyl dianion and highly strained three-membered ring.

Surface-initiated ring-opening metathesis polymerization (SI-ROMP) to attach a tethered organic corona onto CdSe/ZnS core/shell quantum dots.

Core-shell CdSe/ZnS quantum dots (QDs) are useful as tunable photostable fluorophores for multiple applications in industry, biology, and medicine. However, to achieve the optimum optical properties, the surface of the QDs must be passivated to remove charged sites that might bind extraneous substances and allow aggregation. Here we describe a method of growing an organic polymer corona onto the QD surface using the bottom-up approach of surface-initiated ring-opening metathesis polymerization (SI-ROMP) with Grubbs catalyst. CdSe/ZnS QDs were first coated with mercaptopropionic acid by displacing the original trioctylphosphine oxide layer, and then reacted with 7-octenyl dimethyl chlorosilane. The resulting octenyl double bonds allowed the attachment of ruthenium alkylidene groups as a catalyst. A subsequent metathesis reaction with strained bicyclic monomers (norbornene-dicarbonyl chloride (NDC), and a mixture of NDC and norbornenylethylisobutyl-polyhedral oligomeric silsesquioxane (norbornoPOSS)) allowed the construction of tethered organic homo-polymer or co-polymer layers onto the QD. Compounds were characterized by FT-IR, 1H-NMR, X-ray photoelectron spectroscopy, differential scanning calorimetry, and transmission electron microscopy. Atomic force microscopy showed that the coated QDs were separate and non-aggregated with a range of diameter of 48-53 nm.

A route to stereochemically pure benzyllithium reagents by stereocontrolled epimerisation.

Alkyllithium compounds are not generally stable at room temperature, therefore strategies were established to overcome this limitation. We present a systematic approach to obtain a stereochemically enriched benzyllithium compound, starting with the simple addition of a chiral auxiliary and ending by incorporation of the auxiliary in the substrate. Thereby, a very unusual dimer of a lithiated benzylsilane was obtained, which could be split into stereochemically enriched monomers by the addition of Lewis bases. Furthermore, we were able to understand the factors responsible for this stereochemical enrichment by using quantum chemical calculations and clarify the configuration of the lithiated compound and the corresponding trapping product by crystallisation. This enabled us to determine the stereochemical course of the deprotonation and the subsequent metathesis reaction.

Characterization of polyethylene synthesized by zirconium single site catalysts

New non-metallocene, bridged-zirconium center catalysts were prepared by Schiff base condensations reaction of two equivalents of appropriate 2-hydroxybenzaldehyde with one equivalent of 4,4′-methylene bis(2-methylcyclohexylamine), and subsequent metathesis reaction with ZrCl4(THF)2, and tested for ethylene polymerization reaction at different conditions. Catalyst productivities were found to be high, in the range of 29.5 × 103 kg/mole·Zr·h to 2.3 × 103 kg/mole·Zr·h, dependents on the polymerization condition. The molecular weight of the product, i.e. polyethylene, varied from 397,000 to 988,000. 13C NMR study of the polymers indicate that fraction of branches and end groups percentage range from 0.01 to 0.55. X-ray diffraction analysis showed that polyethylene samples had highly crystalline structure within the orthorhombic space group (Pnam) and carbon–carbon interatomic distance of 0.154061 nm and the C–C–C angle of 112.192°.

Distinct new catalysts for utilization of ethylene gas to polymer and oligomer

Bi-nickel-center catalysts were prepared by Schiff-base condensation of 2,3-butanedione with 2,6-di-isopropylaniline; 2-5-butylaniline, 2-isopropylaniline and 1,4-phenylene diamine(I). More Schiff-base ligands were prepared by condensation of 2,3-butandione with 2,6-diisopropylaniline; 2,4-6-trimethyl aniline and 4,4-diaminophenyl (benzidine)(II), and subsequent metathesis reaction with (DME)NiBr2. Bis(alpha diimine)nickel(II)dibromide complexes are suitable catalysts and are precursors for the polymerization of ethylene after activation with methylaluminoxane (MAO). In comparison with these complex analogs, mono-nickel-center catalysts, the new catalysts have much bigger molecules, illustrated by the distance between every two active centers (II and III). For bi-nickel-center catalysts, the catalyst’s structural credibility had profound influence on the catalytic activity. When the substituent was diisopropyl; t-butyl or methyl, the catalysts demonstrated much higher catalytic activity than the corresponding mono-nickel-center catalysts. Catalyst (II) with phenyl bridge showed high activity compared with catalyst (III) with diphenyl bridge. The catalytic properties of these complexes and the character of the obtained polymers depend on the ligand structure of the used catalysts. Substituents on the arene moiety and/or the backbone of the ligand influence the polymerization reaction. Small aryl substituents result in the formation of low molecular weight oligomers, whereas bulky aryl substituents gave high molecular weight polyethylene. Catalysts are cheap and can be prepared easily with available starting material and stable in air. The effect of Al/Ni ratio, of reaction time, variation of ethylene pressure, and the effect of temperature on catalyst performance will be discussed.

Bulky Formamidinate-Supported Lanthanoid Halides and Alkyls, Including a Rare Terminal La–Me Species

The oxidation of [Sm(DippForm)2(thf)2] (1; DippFormH = N,N′-bis(2,6-diisopropylphenyl)formamidine) by tert-butyl chloride, 1,2-dibromoethane, and iodine, respectively, at ambient temperature led to the isolation of the light yellow crystalline samarium(III) halide complexes [Sm(DippForm)2X(thf)] (2, X = Cl; 3, X = Br; 4, X = I) in good yield. The subsequent metathesis reaction of [Ln(DippForm)2X(thf)] (2, Ln = Sm, X = Cl; Ln = La, X = F) with LiMe and LiCH2SiMe3 generated the samarium alkyl complexes [Sm(DippForm)2R(thf)] (5, R = Me; 6, R = CH2SiMe3) and the rare terminal La–Me complex [La(DippForm)2Me(thf)] (7). The attempted ligand exchange reaction of 7 with 1,2,3,4-tetraphenylcyclopentadiene gave, unexpectedly, the homoleptic tris(formamidinato)lanthanum complex [La(DippForm)3] (8) in very low yield. The redox transmetalation/protolysis (RTP) reaction from samarium metal with bis(2-bromo-3,4,5,6-tetrafluorophenyl)mercury and DippFormH in thf yielded the mono(formamidinato)samarium(III) complex [Sm(DippForm)Br2(thf)3] (9) as a coproduct with the bis(formamidinate) 3. Redox reaction of the divalent samarium complex [Sm(DippForm)2(thf)2] (1) with diphenylmercury resulted in the ethenolate complex [Sm(DippForm)2(OCH═CH2)(thf)] (10) instead of the target Sm–Ph complex, the product resulting from the decomposition of Lewis base thf molecules.

1-Meth-oxy-3-(pyridin-2-yl)indolizin-2-yl](pyridin-2-yl)methanone.

Methyl­ation of [1-hy­droxy-3-(pyridin-2-yl)indolizin-2-yl](pyridin-2-yl)methanone was performed via metalation with potassium tert-butano­late in toluene and a subsequent metathesis reaction with methyl iodide yielded the yellow title compound, C20H15N3O2. The substituents at the indolizine unit are twisted [the indolizine ring system makes dihedral angles of 34.67 (7) and 77.49 (5)°, respectively, with the pyridyl and pyridinoyl rings] with single bonds between the central unit and the attached pyridine ring [1.459 (3) Å] and the pyridinoyl group [1.483 (3) Å]. There are no classical hydrogen bonds in the crystal structure.

Characterization of Polyethylene Synthesized by Bi-Nickel Catalysts

New non-metallocene, bi-nickel center catalysts were prepared by Schiff base condensation of 2,3-butanedione with 2,6-di-isopropylaniline and subsequent metathesis reaction with (DME)NiBr2, and tested for ethylene polymerization reaction at different conditions. Catalyst productivities were found to be high, 45 × 103 kg/mmol Ni per h. The molecular weight of the product, i.e., polyethylene, varied from 4831 (a paste-like material) to 968 754. The polydispersity (M w /M n) of the synthesized polyethylene varied from 2.16 to 8.06. Structurally, the results indicated that, when the end-group density decreased, M w increased with broadening of M w distribution and crystallinity of PE samples increased when the end-group density decreased.

Synthetic, Structural, and Theoretical Investigation of Guanidinate Complexes Containing Planar Cu6 Cores

The addition of diethylcyanamide to a tetrahydrofuran solution of lithium dialkylamide LiN(CH(3))(2) or Li NCH(2)CH(2)CH(2) CH(2), Li(PYR), results in the corresponding lithium 1,1,3,3-tetraalkylguanidinate, Li(TAG). The subsequent metathesis reaction of Li(TAG) with CuCl generates hexanuclear copper(I) complexes with the general formula [Cu(mu-TAG)](6), where TAG = DEDMG (1) and DEPYRG (2).

A New Strategy for Synthesis of Novel Classes of Room-Temperature Ionic Liquids Based on Complexation Reaction of Cations

A novel series of ionic liquids have been synthesized with a new methodology. The essence of this methodology is to form the cations of ionic liquids through the complexation reactions of neutral organic ligands with metal ions, followed by the subsequent metathesis reactions of the resulting salts with anion donors. We chose -lithiotrifluoromethanesulfonimide as a candidate for anion donors because anions have high thermal stabilities and weakly coordinating properties, which are crucial to the generation of less viscous and more hydrophobic ionic liquids. The transition-metal ions chosen in our investigation are and . The uses of these ionic liquids as the new electrolytes for electrodeposition have been demonstrated.

Synthesis of 2,2′‐Biimidazolium‐Based Ionic Liquids: Use as a New Reaction Medium and Ligand for Palladium‐Catalyzed Suzuki Cross‐Coupling Reactions.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of 2,2‘-Biimidazolium-Based Ionic Liquids: Use as a New Reaction Medium and Ligand for Palladium-Catalyzed Suzuki Cross-Coupling Reactions

Neat reactions of 2,2'-biimidazole with an excess of alkyl or polyfluoroalkyl iodides at 140 degrees C, followed by anion exchange with LiN(SO(2)CF(3))(2) or KPF(6), gave the diquaternary salts 3a-k in >80% yields. However, by controlling the reaction stoichiometry, 2,2'-biimidazole can also be monoquaternized with the same electrophiles at 100 degrees C under similar conditions. Subsequent metathesis reactions with LiN(SO(2)CF(3))(2) or KPF(6) resulted in the ionic liquids 4a-m in high yields. Thermal properties were determined with a differential scanning calorimeter (DSC) and a thermogravimetric analyzer (TGA). Most of the monoquaternary salts are room-temperature ionic liquids. 1,3,1'-Tributyl-2,2'-biimidazolium hexafluorophosphate was demonstrated to be an excellent solvent and ligand for palladium-catalyzed Suzuki cross-coupling reactions. The catalytic ionic liquid system may be recycled at least 14 times without a significant decrease in catalytic performance.

New bi-nuclear and multi-nuclear α-diimine/nickel catalysts for ethylene polymerization

Bi-nickel-centre catalysts {[2,6-diisopropyl-C 6H 3 N C(CH 3) (CH 3)C N 3,5-di-R C 6H 2 CH 2 3′,5′-di-R C 6H 2 N C(CH 3) (CH 3)C N 2,6-diisopropyl-C 6H 3][NiCl 2] 2; R, CH(CH 3) 2, CH 2CH 3, CH 3} were prepared by Schiff-base condensation of 2,3-butanedione with 2,6-diisopropylaniline and substituted bis-aniline, and subsequent metathesis reaction with (DME)NiCl 2. Multi-nickel-centre catalysts { [( N C(CH 3) (CH 3)C N 3,5-di-R C 6H 2 CH 2 3′,5′-di-R C 6H 2 ) NiCl 2] n ; R, CH(CH 3) 2, n = 4.0; R, CH 2CH 3, n = 4.0; R, CH 3, n = 2.5} were prepared by Schiff-base condensation of 2,3-butanedione with substituted bis-aniline, and subsequent metathesis reaction with (DME)NiCl 2. Comparing with mono-nickel-centre catalysts, the new catalysts have much bigger molecules, particularly the distance between every two active centres was controlled for bi-nickel-centre catalysts, and the distances among several active centres were controlled for multi-nickel-centre catalysts, resulting in the micro chemical environment of nickel centre being regulated. The catalytic evaluation clearly showed that this structural regulation had significant influence on catalytic activity. When the substitute was isopropyl or ethyl, the new catalysts demonstrated much higher catalytic activity than the corresponding mono-nickel-centre catalysts; but when the substitute was methyl, the new catalysts demonstrated lower catalytic activity than the corresponding mono-nickel-centre catalysts. The most efficient new catalyst was multi-nickel-centre catalyst with ethyl as substitute, which catalytic activity was high up to 3220 gPE/(gNi h) at 25 °C with Al(MAO)/Ni ratio at 500.

Cage Compounds of Heterotrimetallic Mixed Phosphanediide/Silanolate Aggregates with an Alkaline Earth Metal-Centered Phosphorus Octahedron

The lithiation of potassium triisopropylsilylphosphanide yields the corresponding phosphanediide. The subsequent metathesis reaction with SrI(2) and BaI(2) in the presence of hexamethyldisiloxane gives hexalithium hexapotassium strontium hexakis(triisopropylsilylphosphanediide)bis(trimethylsilanolate) (1) and the corresponding barium derivative (2), respectively. The alkaline earth metal atoms are surrounded octahedrally by the phosphanediide ligands. Six P(3) faces of the octahedron are capped by the K atoms, and the P-P edges of two opposite P(3) faces are bridged by the lithium atoms. The Li cations are also bonded to the Me(3)SiO substituents giving a coordination number of three for the alkali metals.

The Metalation of (tert-Butyldimethylsilyl)(2-pyridylmethyl)amine with Dimethylzinc and Subsequent Zinc-Mediated Carbon−Carbon Coupling Reaction

The lithiation of 2-(aminomethyl)pyridine and the subsequent reaction with ClSiMe2tBu yields (tert-butyldimethylsilyl)(2-pyridylmethyl)amine (1). The metalation of 1 with dimethylzinc gives colorless dimeric methylzinc 2-pyridylmethyl(tert-butyldimethylsilyl)amide (2), which crystallizes in the triclinic space group P1¯. The solvent-free thermal decomposition of 2 at 150 °C leads to the evolution of methane, the precipitation of zinc metal and the formation of amine 1, bis(methylzinc)—1,2-dipyridyl-1,2-bis(tert-butyldimethylsilylamido)ethane (3), and bis[(tert-butyldimethylsilyl)(2-pyridylmethyl)amido]zinc (4). Compound 3 can be obtained in good yield by reacting 2 with dimethylzinc at elevated temperatures in toluene. During this reaction, zinc metal precipitates and methane is evolved. The C−C coupling product 3 crystallizes in the tetragonal space group I41cd. The lithiation of 1 and the subsequent metathesis reaction with anhydrous ZnCl2 yields complex 4 almost quantitatively.