Neodymium Catalyst for the Polymerization of Dienes and Polar Vinyl Monomers

Ziegler–Natta catalysts have played a major role in industry for the polymerization of dienes and vinyl monomers. However, due to the deactivation of the catalyst, this system fails to polymerize polar vinyl monomers such as vinyl acetate, methyl methacrylate, and methyl acrylate. Herein, a catalytic system composed of NdCl₃⋅3TEP/TIBA is reported, which promotes a quasi‐living polymerization of dienes and is also active for the homopolymerization of polar vinyl monomers. Additionally, this catalytic system generates polymyrcene‐b‐polyisoprene and poly(myrcene)‐b‐poly(methyl methacrylate) diblock copolymers by sequential monomer addition. To encourage the replacement of petroleum‐based polymers by environmentally benign biobased polymers, polymerization of β‐myrcene is demonstrated with a catalytic activity of ≈106 kg polymer mol Nd⁻¹ h⁻¹.     

Cu(OTf)2/Et3N-promoted cyclocondensation of activated α-methylene alkenes and nitroolefins: a novel one-pot synthesis of polysubstituted benzenes

A simple and efficient one-pot synthesis of polyfunctionalized benzenes has been developed via cyclocondensation of activated α-methylene alkenes such as vinyl malononitriles and ethyl vinyl cyanoacetates with nitroolefins using Cu(OTf)₂/Et₃N as a novel catalytic system.     

Synthesis of α-methyl-β-(3-methylpyrazol-1-yl)-and α-methyl-β-(5-methylpyrazol-1-yl)propionic acids and their esterification with vinyl acetate

α-Methyl-β-(3-methylpyrazol-1-yl)-and α-methyl-β-(5-methylpyrazol-1-yl)propionic acids were synthesized by reaction of 3(5)-methylpyrazole with methyl methacrylate, followed by separation of the resulting isomeric esters and their hydrolysis. Esterification of the title acids was performed via vinyl exchange reaction with vinyl acetate in the catalytic system mercury acetate-trifluoroacetic acid.     

An improved total synthesis of (+)-macroline and alstonerine as well as the formal total synthesis of (-)-talcarpine and (-)-anhydromacrosalhine-methine

An intramolecular Pd-catalyzed alpha-vinylation process is described. This cyclization has been employed for the enantiospecific total synthesis of gram quantities of both (+)-macroline 3 and the macroline equivalent 4. This sequence is compared to the enolate-driven cross-coupling process. The intermediate 4 was also converted into (-)-alstonerine 1 via modification of an intramolecular Tsuji-Wacker oxidation. This sequence resulted in an improved total synthesis of (-)-talcarpine 5 and (-)-anhydromacrosalhine-methine 6 as well.     

Catalytic enantioselective 1,3-dipolar cycloaddition of azomethine ylides with vinyl sulfones

[reaction: see text] A general protocol for the enantioselective catalytic 1,3-dipolar cycloaddition of azomethine ylides with aryl vinyl sulfones is described. Nearly complete exo selectivity and enantioselectivities up to 85% ee are attained with Cu(CH(3)CN)(4)ClO(4)/Taniaphos as the catalyst system. The resulting enantioenriched 3-sulfonyl cycloadducts are versatile intermediates in the synthesis of 2,5-disubstituted pyrrolidines.     

Nucleophilic addition to acetylenes in superbasic catalytic systems: XVII. Vinyl ethers with furyl and cycloacetal fragments: Synthesis and structure

4-Hydroxymethyl-2-(2-furyl)-1,3-dioxolane and 5-hydroxy-2-(2-furyl)-1,3-dioxane consisting of mixtures of cis- and trans-isomers react with acetylene in the superbasic catalytic system KOHH-DMSO at the atmospheric or higher pressure (80–85°C, 2–3 h) giving the corresponding vinyl ethers in 88–90% yield. The ratio of the structural and configurational isomers in vinyl ethers remains the same as in the initial compounds.     

双-(β-酮萘胺)镍(II)/B(C6F5)3/AlEt3体系催化醋酸降冰片烯酯聚合及结构表征

采用双-(β-酮萘胺)镍(II)/B(C6F5)3/AlEt3体系在甲苯溶剂中进行了降冰片烯衍生物醋酸降冰片烯酯的聚合,研究了聚合温度和聚合时间对聚合的影响。通过1H NMR、13C NMR、FT-IR、DSC及WAXD技术对聚合物的结构和性能进行了研究。证明双-(β-酮萘胺)镍(II)/B(C6F5)3/AlEt3体系催化醋酸降冰片烯酯按乙烯基加成聚合方式进行的,聚合物分子量中等和分子量分布较窄。所得聚合产物为非晶态,具有短程有序长程无序的特征,热稳定性较好,并能够溶解在大部分普通有机溶剂中。     

Optimized Synthesis of Vinyl Ether Sugars and Vinyl Glycosides through Transfer Vinylation Catalyzed by (4,7‐Ph2‐phen)Pd(OOCCF3)2

Sugar vinyl ethers and vinyl glycosides are conveniently synthesized by catalytic transfer vinylation with butyl vinyl ether, which serves as both the solvent and source of vinyl. The air‐stable catalyst (4,7‐diphenyl‐1,10‐phenanthroline)Pd(OOCCF₃)₂ is prepared in situ from commercially available components.     

CuI-catalyzed suzuki-miyaura and sonogashira cross-coupling reactions using DABCO as ligand

In the presence of TBAB, CuI-catalyzed Suzuki-Miyaura cross-coupling of vinyl halides and aryl halides with arylboronic acids was conducted smoothly to afford the corresponding diarylethenes and polyaryls in moderate to good yields using DABCO (1,4-diazabicyclo[2.2.2]octane) as the ligand. We also found that the inexpensive CuI/DABCO catalytic system was effective for Sonogashira cross-couplings of aryl halides and vinyl halides. A variety of aryl halides and vinyl halides including activated aryl chlorides underwent the coupling with terminal alkynes in moderate to excellent yields.     

Oxidative coupling of alkynes mediated by nitroxyl radicals under Sonogashira conditions and Pd-free catalytic approach to stable radicals of 3-imidazoline family with triple bonds

In the presence of Pd catalyst, 3-imidazoline nitroxyl radicals promote oxidative coupling (dimerization) of terminal alkynes even in the absence of Cu(II) additives. On the other hand, the Pd-free CuI-PPh₃-K₂CO₃-DMF catalytic system leads to the efficient cross-coupling of 1-hydroxy-4-[2-(p-iodophenyl)vinyl]-2,2,5,5-tetramethyl-3-imidazoline-3-oxide with terminal aryl- and hetarylacetylenes with the formation of 4-[2-(aryl/hetarylethynyl)phenyl)vinyl]-2,2,5,5-tetramethyl-3-imidazoline-3-oxide-1-oxyls in 70-75% yields.     

Optically Active Helical Poly[(S)‐3‐vinyl‐2,2′‐dihydroxy‐1,1′‐binaphthyl]: New Ligand for Asymmetric Addition of Diethylzinc to Aryl Aldehyde

Poly[(S)‐3‐vinyl‐2,2′‐dihydroxy‐1,1′‐binaphthyl] (L*) was obtained by taking off the protecting groups of poly[(S)‐3‐vinyl‐2,2′‐bis(methoxymethoxy)‐1,1′‐binaphthyl] (poly‐ 1 ). L* was proved to keep a stable helical conformation in solution. The application of helical L* in the asymmetric addition of diethylzinc to aldehydes has been studied. The catalytic system employing 10 mol% of L* and 150 mol% of Ti(OⁱPr)₄ was found to promote the addition of diethylzinc to a wide range of aromatic aldehydes, giving up to 99% enantiomeric excess (ee) and up to 93% yield of the corresponding secondary alcohol at 0°C. The chiral polymer can be easily recovered and reused without loss of catalytic activity as well as enantioselectivity.     

Development of a highly efficient catalytic method for synthesis of vinyl ethers

A new method for the preparation of alkyl vinyl ethers has been developed. Thus, various types of alkyl vinyl ethers were synthesized by the reaction of alcohols with vinyl acetate under the influence of a catalytic amount of [Ir(cod)Cl]2 combined with Na2CO3 in good to excellent yields.     

Catalysis by Platinum(II) Iodo Complexes of C(sp2)–C(sp2) Electrophile Coupling

Kinetics and Catalysis - The catalytic C(sp2)–C(sp2) coupling of vinyl iodide was performed to form 1,3-butadiene in the PtII–NaI–С2Н3I–acetone-D6 system at...     

Catalytic,asymmetric Mannich-type reactions of N-acylimino esters: reactivity,diastereo- and enantioselectivity,and application to synthesis of N-acylated amino acid derivatives

In the presence of a catalytic amount of Cu(OTf)(2)-chiral diamine 3e complex, N-acylimino esters reacted with silyl enol ethers to afford the corresponding Mannich-type adducts in high yields with high enantioselectivities. A wide variety of silyl enol ethers derived from ketones, as well as esters and thioesters, reacted smoothly. In the reactions of alpha-substituted silyl enol ethers (alpha-methyl or benzyloxy), the desired syn-adducts were obtained in high yields with high diastereo- and enantioselectivities. Several intermediates for the synthesis of biologically important compounds were prepared using this novel catalytic asymmetric Mannich-type reaction, and at the same time, absolute and relative stereochemical assignments were made. In addition, it has been revealed that alkyl vinyl ethers reacted with N-acylimino esters in the presence of a catalytic amount of the Cu(II) catalyst to give the corresponding Mannich-type adducts in high yields with high enantioselectivities. This is the first example of catalytic asymmetric Mannich-type reactions with alkyl vinyl ethers. The reaction mechanism, structure of chiral catalyst-electrophile complexes, and transition states of these catalytic asymmetric reactions were assumed based on X-ray crystallographic analysis of the Cu(II)-chiral amine complex, PM3 calculations, and FT-IR analyses, etc. Finally, (1R,3R)-N-(3-hydroxy-1-hydroxymethyl-3-phenylpropyl)dodecanamide (HPA-12, 1), a new inhibitor of ceramide trafficking from endoplasmic reticulum to the site of sphingomyerin (SM) synthesis, has been synthesized efficiently using the present Mannich-type reaction as a key step. The synthesis involved three steps (two-pot), and total yield was 82.9%.     

Magnetic nanoparticles grafted <Emphasis Type="SmallCaps">l</Emphasis>-carnosine dipeptide: remarkable catalytic activity in water at room temperature

Modification of magnetic nanoparticle surface with l-carnosine dipeptide was developed using a simple chemical process. In order to synthesize this catalyst system, first, magnetic nanoparticles were modified with vinyl groups using trimethoxy(vinyl)silane. Next, the vinyl groups were oxidized with H₂O₂ to give the epoxy-functionalized MNPs. Reaction of l-carnosine with epoxide rings via amino group resulted in the functionalization of MNPs surface with l-carnosine, covalently. To explore high catalytic activity of this material, l-carnosine grafted on magnetic nanoparticles (Fe₃O₄@SiO₂@LCar; l-CarMNP) was used as a highly efficient heterogeneous nano-organocatalyst in a multicomponent reaction in aqueous medium at room temperature. It was reusable at least for eight times without a significant decrease in its catalytic activity. The catalytic activity of l-CarMNP was compared with other magnetic nano-organocatalyst, and results demonstrate that l-CarMNP has high catalytic activity related to others tested.     

Thermal properties and flammability performance of poly (vinyl alcohol)/α-zirconium phosphate nanocomposites

Nanocomposites of poly (vinyl alcohol) with ethylamine modified zirconium phosphate (ZrP-EA) were prepared by solution blending. Their morphologies were elucidated with X-ray diffraction and transmission electron microscopy, while the thermal stability and flammability performance were characterized by thermogravimetric analysis, Fourier transform infrared spectra and microscale combustion calorimetry. It was established that the morphology of the nanocomposites evolved as ZrP-EA content increased. In the nanocomposites, catalytic degradation of the acetate groups remaining in poly (vinyl alcohol) occurred and catalytic carbonization was observed. Microscale combustion calorimetry revealed that the flammability performance of poly (vinyl alcohol) was improved by the introduction of zirconium phosphate nanoplatelets.     

Synthesis of 1,1-disubstituted olefins via catalytic alkyne hydrothiolation/Kumada cross-coupling

Using recently developed methodology for the regioselective formation of branched alkyl vinyl sulfides, we report a convenient route to 1,1-disubstituted olefins. We demonstrate that n-propanethiol successfully undergoes catalytic alkyne hydrothiolation with both aryl and aliphatic alkynes using Tp*Rh(PPh3)2 as the catalyst. The resulting vinyl sulfides undergo Kumada cross-coupling to afford the desired disubstituted alkene. Both two-step and one-pot procedures are reported.     

Alkene Carboboration Enabled by Synergistic Catalysis

A synergistic Pd/Cu system for the coupling of alkenes, (Bpin)₂ (pin=pinacolate), and aryl/vinyl bromides is disclosed. This method allows for the catalytic generation of secondary Csp³?Cu nucleophiles in situ and subsequent Pd‐catalyzed cross‐coupling.     

VINYL POLYMERIZATION OF NORBORNENE CATALYZED BY [2-(2-BENZIMIDAZOLYL)-6-((1-ARYLIMINOETHYL)PYRIDYL)]NICKEL CHLORIDE/MAO SYSTEM

The catalytic system of[2-(2-benzimidazolyl)-6-((1-aryliminoethyl)pyridyl)]nickel chloride/MAO(methylalu- minoxane)was found to be good active for vinyl polymerization of norbornene and provided polymers with relative narrow molecular distributions.Various reaction parameters,such as the ratios of nickel precursor to MAO or monomer norbornene, and the nature of the ligands in complexes were carefully investigated to realize their effects on the catalytic activities, polymer molecular weight and molecular...     

Modification of poly(vinyl chloride) with sodium salts of triazoles

New copolymers containing reactive vinyltriazole units and polyvinylene blocks with conjugation system promising as materials with special electrical, physical, catalytic, and sorption properties have been prepared by the reaction of poly(vinyl chloride) with sodium salts of 1,2,4-triazole and 1,2,3-benzotriazole in a dimethylformamide medium.