Efficient C-N coupling in electrocatalytic urea generation on copper carbonate hydroxide electrocatalysts

Urea generation through electrochemical CO_(2) and NO_(3)~-co-reduction reaction(CO_(2)NO_(3)RR)is still limited by either the low selectivity or yield rate of urea.Herein,we report copper carbonate hydroxide(Cu_2(OH)_2CO_(3))as an efficient CO_(2)NO_(3)RR electrocatalyst with an impressive urea Faradaic efficiency of45.2%±2.1%and a high yield rate of 1564.5±145.2μg h~(-1)mg_(cat)~(-1).More importantly,H_(2) evolution is fully inhibited on this electrocatalyst over a wide potential range between-0.3 and-0.8 V versus reversible hydrogen electrode.Our thermodynamic simulation reveals that the first C-N coupling follows a unique pathway on Cu_2(OH)_2CO_(3) by combining the two intermediates,~*COOH and~*NHO.This work demonstrates that high selectivity and yield rate of urea can be simultaneously achieved on simple Cu-based electrocatalysts in CO_(2)NO_(3)RR,and provide guidance for rational design of more advanced catalysts.

A review on electrocatalytic CO_(2) conversion via C-C and C-N coupling

Electrochemical C-C and C-N coupling reactions with the conversion of abundant and inexpensive small molecules,such as CO_(2) and nitrogencontaining species,are considered a promising route for increasing the value of CO_(2) reduction products.The development of high-performance catalysts is the key to the both electrocatalytic reactions.In this review,we present a systematic summary of the reaction systems for electrocatalytic CO_(2) reduction,along with the coupling mechanisms of C-C and C-N bonds over outstanding electrocatalytic materials recently developed.The key intermediate species and reaction pathways related to the coupling as well as the catalyst-structure relationship will be also discussed,aiming to provide insights and guidance for designing efficient CO_(2) reduction systems.

不对称C-N交叉偶联反应的研究进展

在过去几十年中,C-N交叉偶联反应构建手性胺类化合物在药物、材料和催化领域发挥了着重要作用。然而,由于C-N键具有更高的键解离能,利用不对称C-N交叉偶联方法在构建中心手性、平面手性、轴手性和螺环手性化合物存在一些局限性。本文重点介绍了目前成熟的构建不对称C-N键的方法,如过渡金属Pd与Cu催化、手性有机小分子催化,并简要概括其化学实用性。

Optimization of cross-coupling reaction for synthesis of antitumor drug vismodegib

In order to improve the yield and reduce the cost in the synthesis of antitumor drug vismodegib the key intermediates are prepared and the Negishi reaction step is examined.The effects of different molar ratios of reactants dosages of catalyst and time for refluxing are investigated by using single factor tests.The results demonstrate that when the molar ratios of 2-bromopyridine 2-chloro-N-4-chloro-3-iodophenyl -4-methylsulfonyl benzamide zinc chloride n-butyllithium and tetrakis triphenyl phosphine palladium are changed to 1.0∶0.5∶1.5∶1.1∶0.05 and the mixture is refluxed for 24 h the production yield is improved to 72%.This reaction condition significantly enhances the synthetic efficiency avoids consuming excessive raw materials/catalysts and meanwhile prevents a prolonged reaction time.The optimization of the proportion of reactants and the heating time is proved to be important for the efficiency and economy in cross-coupling reaction to synthesize vismodegib.

Cu(OAc)_2 catalyzed Sonogashira cross-coupling reaction in amines

A simple Cu（OAc）2 catalyzed Sonogashira coupling protocol is presented. It was found that the couplings of a variety of aryl halides with terminal alkynes were conducted smoothly to afford the corresponding desired products in moderate to excellent yields, using Cu（OAc）2 as the catalyst and Et3N as the solvent.

Synthesis of Enamines via the Cross-coupling of Thioamides and Diarylketones Promoted by the Sm/SmI_(2)Mixed Reagent

Enamines, promoted by the samarium/samarium diiodide mixed reagent, were synthesized via the cross-coupling of thioamides and diarylketones in good yields.

Microwave-assisted Palladium Catalyzed Cross-coupling Reaction of Sodium Tetraphenylborate with Carboxylic Anhydrides

A rapid and efficient method for synthesis of unsymmetrical ketones under microwave irradiation is reported.

Highly active and stable supported Pd catalysts on ionic liquidfunctionalized SBA-15 for Suzuki–Miyaura cross-coupling and transfer hydrogenation reactions

Highly dispersed palladium nanoparticles were synthesized in the presence of immobilized ionic liquid on mesoporous silica SBA-15.PdNPs(2.4 nm)_me-Im@SBA-15 catalyst was prepared by the reduction using NaBH_4 as the reducing agent with controlled feed rate and has been investigated as ligand-free catalyst for Suzuki–Miyaura cross-coupling reaction at room temperature in aqueous solution under air.PdNPs catalyst was also prepared in situ from PdCl4_me-Im@SBA-15 during the reaction and demonstrated high activity and stability towards nitrobenzene hydrogenation at high temperature. Both catalysts were reusable at least for four recycle processes without significant loss in activity with simple procedure. The catalysts were characterized by TEM, EXAFS, FTIR and XPS.

Polybinaphthyls of (R)-3,3′-Diiodo-2,2′-binaphtho-20-crown-6 with p-Divinylbenzene via Heck Cross-coupling Reaction

The present paper deals with the polymerization of ( R ) 3,3′ diiodo 2,2′ binaphtho 20 crown 6 with \{ p divinylbenzene\} under Heck coupling reaction condition. Both the monomers and the polymer were analyzed by NMR, FTIR, UV, CD, fluorescent spectroscopy, polarimetry, GPC and elemental analysis. The polymer can emit a strong blue fluorescence and is expected to have the potential application in the polarized blue light emitting sensors. The chiral conjugated polymer exhibits a strong Cotton effect in its Circular Dichroism(CD ) spectrum, indicating the high rigidity of the polymer backbone.

Pd/Zn/C-N催化CO_(2)加氢合成甲醇性能研究

利用Zn2+和2-甲基咪唑自组装形成的ZIF-8, 800℃N2氮气气氛下焙烧得到Zn/C-N载体.采用NaBH4还原法将不同含量Pd负载于Zn/C-N上焙烧后得到Pd/Zn/C-N催化剂, ICP测得Pd实际负载量为0.02%、0.05%、0.1%、0.3%.负载Pd后,由于Pd氢溢流作用, ZnO表面还原温度降低,氧空穴增加,更有利于CO_(2)解离吸附,因此Pd负载量越高,催化剂CO_(2)转化率越高.甲醇选择性受Pd纳米颗粒大小显著影响,小颗粒Pd与ZnO相互作用更强,更有利于甲醇生成,其中0.02%Pd/Zn/C-N催化剂在275℃, 2 MPa反应条件下, Pd/g上甲醇时空收率最高, STYMeOH值为11.0 mol/(g Pd·h).

Cu-catalyzed cross-couplings under ligandless conditions

The possibility to carry out Cu-catalyzed cross-couplings under ligandless conditions was studied. It was found that by using K3PO4 as the base, the cross-coupling could proceed successfully between aryl iodides and several types of nucleophiles. Aryl bromides were completely inactive under the same reaction conditions.

Cross-Coupling Correction for LaCoste ＆ Romberg Airborne Gravimeter

Abstract The cross-coupling corrections for the LaCoste ＆ Romberg airborne gravimeter are computed as a linear combination of 5 so-called cross-coupling monitors. The weight factors （coefficients） determined from marine gravity data by the factory are obviously not optimal for airborne application. These coefficients are recalibrated by minimizing the difference between airborne data and upward continued surface data （external calibration） and by minimizing the errors at line crossings （internal calibration） respectively. An integrating method to recalibrate the above-mentioned coefficients and the beam scale factor simultaneously is also presented. Experimental results show that the systemic errors in the airborne gravity anomalies can be greatly reduced by using any of the recalibrated coefficients. For example, the systemic error is reduced from 4.8 mGal to 1.8 mGal in Datong test.

Stereoselective Synthesis of (E)-1,3-Enynyl Bromides via Pd/Cu-cata-lyzed Cross-coupling Reaction of (Z)-α-Bromovinylstannanes

Z)-á-Bromovinylstannanes undergo the cross-coupling reaction with alkynyl iodides in the presence of Pd(PPh3)4 and CuI in THF at room temperature to afford stereoselectively (E)-1, 3- enynyl bromides in good yields.

LOW-VALENT TITANIUM INDUCED REDUCTIVE CROSS-COUPLING REACTION OF ESTERS WITH DIARYL KETONES

The intermotecular coupling reaction of esters with diarvl ketones induced by titanium tetrachtoride and zinc powder was studied.

LOW-VALENT TITANIUM INDUCED REDUCTIVE CROSS-COUPLING REACTION OF ACYL CHLORIDES WITH DIARYL KETONES

Treatment of acyl chlorides and diaryl ketones with an activated Ti(o)reagent,prepared by reduction of TiCl_4 with Zn powder,effects an intermolecular reductive cross-coupling reaction leading to ketones.

The Electrokinetic Cross-Coupling Coefficient: Two-Scale Homogenization Approach

By the two-scale homogenization approach we justify a two-scale model of ion transport through a layered membrane, with flows being driven by a pressure gradient and an external electrical field. By up-scaling, the electroosmotic flow equations in horizontal thin slits separated by thin solid layers are approximated by a homogenized system of macroscale equations in the form of the Poisson equation for induced vertical electrical field and Onsager's reciprocity relations between global fluxes (hydrodynamic and electric) and forces (horizontal pressure gradient and external electrical field). In addition, the two-scale approach provides macroscopic mobility coefficients in the Onsager relations. On this way, the cross-coupling kinetic coefficient is obtained in a form which does involves the &#950 -potential among the data provided the surface current is negligible.

Pd-Catalyzed Unprecedented Cross-Coupling of Mixed Phenols and Halides for the Synthesis of Aromatic Ethers

Phenolic compounds present in medicinal and edible plants such as flavonoids, chalcones, coumarins, quinones, and phenolic acids. The antioxidant potential of phenolic compounds shows potent activities for cancer prevention and its treatment. From a green chemistry point of view, cascade (tandem) reactions are ideal techniques in organic synthesis for building complex structures. Cascade techniques are sometimes observed in coupling reactions under mild conditions with a tolerance of multifunctional groups. It will be interesting to find a cascade type reaction to synthesize polyphenolic ethers. This research project achieves a new cross-coupling method for establishing polyphenolic ethers from mixed phenols and halides in the presence of palladium catalyst in moderate to good yields.

Evaluation of TlOH Effect for Pd⁰-Mediated Cross-Coupling of Methyl Iodide and Excess Boronic Acid Ester toward Fabrication of [¹¹C]CH₃-Incorporated PET Tracer

The use of thallium(I) hydroxide (TlOH) as a base is known to extremely accelerate the Suzuki-Miyaura cross-coupling reaction using organoboronic acid or organoboronic acid ester as a substrate. Here, we investigated the effects of TlOH by comparing with other conventional bases such as KOH, K2CO3, and CsF for Pd0-mediated rapid cross-coupling reactions between CH3I and organoborane reagents, such as phenyl-, (Z)-4-benzyloxy-2-butenyl-, and benzylboronic acid pinacol esters under the conditions CH3I/borane/Pd0/base (1:40:1:3) in THF/H2O or DMF/H2O for 5 min with an aim to fabricate a PET tracer efficiently. Consequently, however, the use of TlOH was much less efficient than the other bases for the acceleration of cross-coupling reactions. Thus, it was reconfirmed that the milder and non-toxic conditions using K2CO3 or CsF so far developed by our group were most appropriate for the rapid C-methylations.

THE SPIN DELOCALIZATION SUBSTITUENT PARAMETER σ 10. SYNTHESIS OF SUBSTITUTED α, β, β-TRIFLUOROSTYRENES BY THE Pd-CATALYZED CROSS-COUPLING OF TRIFLUOROVINYLZINC BROMIDE WITH ARYL HALIDES

Palladium-catalyzed coupling of trifluorovinylzinc reagent with substituted aryl halides Y-C_6H_4-X (Y=p-NO_2, p-and m-COOMe, p-COOH, p-CONH_2, p- and m-CN; X=Br, I, Cl) provides a synthetic method for α, β, β-trifluorostyrenes(Y-TFS's). A series of previously unavailable Y-TFS's were thus obtained.

A Parametric Study of Mechanical Cross-Coupling in Parallel-Kinematics Piezo-Flexural Nano-Positioning Systems

Piezo-electric nano-positioning stages are being widely used in applications in which precision and accuracy in the order of nano, and high scanning speeds are paramount. This paper presents a Finite Element Analysis (FEA) of the parallel piezo-flexural nano-positioning (PPNP) stages to investigate motion interference between their different axes. Cross-coupling is one of the significant contributors to undesirable runouts in the precision positioning of PPNP actuators. Using ABAQUS/CAE 2018 software, a 3D model of a PPNP stage was developed. The model consists of a central elastic body connected to a fixed frame through four flexural hinges. A cylindrical stack of multiple piezoelectric disks is placed between the moving central body and the fixed frame. Extensive simulations were carried out for three different friction coefficients in the piezoelectric disks’ contact surfaces, different frame materials, and different geometrical configurations of the stage and the hinges. As a result, it was observed that the primary root cause of the mechanical cross-coupling effect could be realized in the combination of the slip and rotation of the piezoelectric disks due to their frictional behavior with the stage moving in the tangential direction, concurrent with changes in the geometry of the stage.