Facile Synthesis of DendriMac Polymers via the Combination of Living Anionic Polymerization and Highly Efficient Coupling Reactions

Two DendriMac polymers (Dendri‐hydr and Dendri‐click) are efficiently and conveniently synthesized via the combination of living anionic polymerization (LAP) and hydrosilylation/click chemistry. Based on the end‐capping of DPE derivatives (DPE‐SiH and DPE‐DA) toward polymeric anions, the polymeric core and arms are effectively synthesized, and the base polymers can be regarded as polymeric bricks. Hydrosilylation and click chemistry are used as coupling reactions to construct the DendriMac polymers with high efficiency and convenience. The numbers of branched arms are calculated by SEC as 5.84 and 6.08 for Dendri‐hydr and Dendri‐click, respectively, which indicate that the DendriMac architectures exhibit high structural integrity. Because of its independence, high efficiency, and convenience, the whole construction can be regarded as the “building of polymeric bricks.”

     

Pd@sPS-NMe_2/AC纳米催化剂制备及在偶联反应中的应用

用胺基功能化间规聚苯乙烯(sPS-NMe_2)与活性炭(AC)分别利用混合沉降法(MP)、混合挥发法(MV)及直接聚合法(DP)制备了sPS-NMe_2/AC复合载体.sPS-NMe_2/AC吸附还原PdCl_2后获得Pd@sPS-NMe_2/AC催化剂.采用扫描电镜和透射电镜对sPS-NMe_2/AC和Pd@sPS-NMe_2/AC形貌进行了分析,考察了sPS-NMe_2/AC复合方法、用量对其形貌、负载Pd金属的影响,发现MV法获得的sPS-NMe_2/AC在其质量比大于1/3时sPS-NMe_2可均匀覆盖AC, Pd纳米粒子为3 nm左右,均匀稳定分散.该催化剂在"借氢"、 Suzuki-Miyaura、 Heck和Sonogashira偶联反应中表现出了优异的催化性能.     

通过不对称多组分反应高效构建手性磺酰胺类化合物

手性磺酰胺类化合物在新型药物方面研究中占据越来越重要的地位.我们成功地实现了磺酰胺、芳基重氮乙酸酯以及亚胺的不对称三组分反应.此反应给出了高达85%产率,以及优异的非对映选择性（d.r.>20：1）和对映选择性（最高可达99%ee）,为高效构建具有两个手性碳的光学纯磺酰胺类化合物提供了一种快速合成方法.我们将反应放大到了克级规模,并对三组分产物进一步衍生得到一种具有三个手性中心的光学纯含亚砜亚胺骨架的五元环化合物.反应的选择性通过过渡金属与手性磷酸协同催化控制.     

Facile and Cost-Efficient Synthesis of Photovoltaic Polymers via Direct Arylation Coupling

As the high calibre candidate of lightweight and flexible solar cells, polymer solar cells(PSCs) have made tremendous progress in recent years. However, the active photovoltaic materials in PSCs are mainly synthesized by metal-mediated coupling reaction requiring harsh reaction conditions, multiple-step synthesis, and cumbersome purification, which is not cost-efficient and may bring toxicity concerns. It is not favorable to the production of photovoltaic polymers and PSC devices on a large scal...     

Enantioselective Synthesis of Bicyclo[3.2.1]octadienes via Palladium-Catalyzed Intramolecular Alkene-Alkyne Coupling Reaction

Bicyclo[3.2.1]octadiene compounds and derivatives exist in a number of natural products and bioactive compounds. Nevertheless, catalytic enantioselective protocols for the synthesis of these skeletons have not been disclosed. Herein we reported a palladium-catalyzed asymmetric intramolecular alkene-alkyne coupling of alkyne-tethered cyclopentenes, affording a library of enantionenriched bicyclo[3.2.1]octadienes in excellent yields and enantioselectivities (mostly >99 % ee). Moreover, the products could undergo an unusual iodination-induced 1,2-acyl migration, forming iodinated bicyclo[3.2.1]octadienes with three vicinal stereocenters. The enone and isolated olefin motifs embedded in the products provide useful handles for downstream elaboration.     

Ethenolate Transfer Reactions: A Facile Synthesis of Vinyl Esters

A simple and efficient metal‐free ethenolate transfer reaction has been elaborated in moderate‐to‐high yields from vinyl acetate. This reaction was accomplished by generation of potassium ethenolate, which was then reacted with homo and mixed anhydrides of aliphatic, aryl and heteroaryl acids, to yield the corresponding vinyl esters. The utility of thus generated vinyl esters was then probed by carrying out intramolecular Heck reactions to give isobenzofuran‐1(3H)‐one derivatives in excellent yields.     

钛酸酯偶联剂的合成及应用

本文叙述了单烷氧型、磷酸酯型和螯合型钛酸酯偶联剂的合成,以及它们在高分子材料中的作用和应用范围.     

低价钛诱导的芳香邻二酮及α-羟基酮的还原偶联反应

Treatment of aromatic 1 , 2-diketones or aromatic a-hydroxy ketones with an activated low-valent titanium reagent, prepared by reduction of TiCl3·1/3AlCl3 with a Zn-Cu reagent, gave an intermolecular coupling reaction leading to the (Z)-1, 2.3.4-tetraaryl-2-butenes. Apossible coupling reaction process was proposed for the aromatic a-hydroxy ketones.     

Facile Synthesis of Amidines via Intermolecular Reductive Coupling of Nitriles with Azobenzene Promoted by Samarium Diiodide

SinceintroducedbyKaganandhisgroups',Sml,hasbeenextensivelyinvestigatedasamild,neutral,selectiveandversatilesingIeelectrontransferreductantinsyntheticchemistry=.Suchas,Barbierreactions,Reformatskyreactions,pinacolcouplingandketone-oIefinreductivehavebeenreportedusingSmI,asreagent.Thereactivitiesofvariousnitrogenfunctionalgroups(imine,oxime,nitro,azo,cyano)towardsSmI,havealsobeenexamined.Recently,ourgrouphasreportedtheintermolecularreductivecouplingofnitrogroupswithcyanogroupsinducedbySml='.…     

Facile Synthesis of 5-Aryl-N-(pyrazin-2-yl)thiophene-2-carboxamides via Suzuki Cross-Coupling Reactions,Their Electronic and Nonlinear Optical Properties through DFT Calculations

Synthesis of 5-aryl-N-(pyrazin-2-yl)thiophene-2-carboxamides (4a–4n) by a Suzuki cross-coupling reaction of 5-bromo-N-(pyrazin-2-yl)thiophene-2-carboxamide (3) with various aryl/heteroaryl boronic acids/pinacol esters was observed in this article. The intermediate compound 3 was prepared by condensation of pyrazin-2-amine (1) with 5-bromothiophene-2-carboxylic acid (2) mediated by TiCl₄. The target pyrazine analogs (4a–4n) were confirmed by NMR and mass spectrometry. In DFT calculation of target molecules, several reactivity parameters like FMOs (E_HOMO, E_LUMO), HOMO–LUMO energy gap, electron affinity (A), ionization energy (I), electrophilicity index (ω), chemical softness (σ) and chemical hardness (η) were considered and discussed. Effect of various substituents was observed on values of the HOMO–LUMO energy gap and hyperpolarizability. The p-electronic delocalization extended over pyrazine, benzene and thiophene was examined in studying the NLO behavior. The chemical shifts of ¹H NMR of all the synthesized compounds 4a–4n were calculated and compared with the experimental values.     

Selective Reductive Coupling of Vinyl Azaarenes and Alkynes via Photoredox Cobalt Dual Catalysis

A visible light-induced Co-catalyzed highly regio- and stereoselective reductive coupling of vinyl azaarenes and alkynes has been developed. Notably, Hünig's base together with simple ethanol has been successfully applied as the hydrogen sources instead of commonly used Hantzsch esters in this catalytic photoredox reaction. This approach has considerable advantages for the straightforward synthesis of stereodefined multiple substituted alkenes bearing an azaarene motif, such as excellent regioselectivity (>20 : 1 for >30 examples) and stereoselectivity (>20 : 1 E/Z), broad substrate scope and good functional group compatibility under mild reaction conditions, which has been utilized in the concise synthesis of natural product monomorine I. A reasonable catalytic reaction pathway involving protolysis of the cobaltacyclopentene intermediate has been proposed based on the mechanistic studies.     

CO2-Enabled Cyanohydrin Synthesis and Facile Iterative Homologation Reactions**

Thermodynamic and kinetic control of a chemical process is the key to access desired products and states. Changes are made when a desired product is not accessible; one may manipulate the reaction with additional reagents, catalysts and/or protecting groups. Here we report the use of carbon dioxide to accelerate cyanohydrin synthesis under neutral conditions with an insoluble cyanide source (KCN) without generating toxic HCN. Under inert atmosphere, the reaction is essentially not operative due to the unfavored equilibrium. The utility of CO₂-mediated selective cyanohydrin synthesis was further showcased by broadening Kiliani–Fischer synthesis under neutral conditions. This protocol offers an easy access to a variety of polyols, cyanohydrins, linear alkylnitriles, by simply starting from alkyl- and arylaldehydes, KCN and an atmospheric pressure of CO₂.     

Rational Design and Synthesis of Hybrid Porous Polymers Derived from Polyhedral Oligomeric Silsesquioxanes via Heck Coupling Reactions

Heck coupling reactions are introduced as an efficient method to prepare porous polymers. Novel inorganic‐organic hybrid porous polymers (HPPs) were constructed via Heck coupling reactions from cubic functional polyhedral oligomeric silsesquioxanes (POSS), iodinated octaphenylsilsesquioxanes (OPS) and octavinylsilsesquioxanes (OVS) using Pd(OAc)₂/PPh₃ as the catalyst. Here, two iodinated OPS were used, IOPS and p‐I₈OPS. IOPS was a mixture with 90% octasubstituted OPS (I₈) and some nonasubstituted OPS (I₉), while p‐I₈OPS was a nearly pure compound with ≥99% I₈ and ≥93% para‐substitution. IOPS and p‐I₈OPS reacted with OVS to produce the porous materials HPP‐1 and HPP‐2, which exhibited comparable specific surface areas with S_BET of 418 ± 20 m² g⁻¹ and 382 ± 20 m² g⁻¹, respectively, with total pore volumes of 0.28 ± 0.01 cm³ g⁻¹ and 0.23 ± 0.01 cm³ g⁻¹, respectively. HPP‐1 showed a broader pore size distribution and possessed a more significant contribution from the mesopores, when compared with HPP‐2, thereby indicating that IOPS may induce more disorder because of the geometrical asymmetry. HPP‐1 and HPP‐2 possessed moderate carbon dioxide uptakes of 134 and 124 cm³ g⁻¹ at 1 bar at 195 K, making them promising candidates for CO₂ capture and storage. The synthesized porous polymers may be easily post‐functionalized using the retained ethenylene groups.

     

The First Cyclopentadienylalkylphosphane Nickel Chelates: Synthesis,Structures, and Reactions

The first cyclopentadienylalkylphosphane nickel chelate complexes are reported. The anionic ligand obtained by reaction of spiro[2.4]hepta‐4,6‐diene with lithium di‐tert‐butylphosphide was treated with NiCl₂ to yield [η⁵:κ¹‐(di‐tert‐butylphosphanylethyl)cyclopentadienyl]chloronickel(II). From this complex, some acetonitrile‐stabilized cationic complexes were obtained by reaction with the respective silver salts in acetonitrile. Methyl‐ and alkynylnickel chelates were prepared by reaction of the chloronickel complex with methyllithium and by copper‐mediated coupling with terminal alkynes, respectively. Some of the complexes prepared were investigated by X‐ray crystallography or cyclic voltammetry. The alkynylnickel chelates undergo cycloaddition reactions with ethoxycarbonylisothiocyanate or tetracyanoethylene, and the cyclobutenes obtained undergo ring opening to the corresponding dienes. The study includes an NMR spectroscopic investigation of the two conformers of one of these dienes.     

Synthesis of C-5 substituted nucleosides via palladium-catalyzed coupling of dienes and amines

The palladium-catalyzed coupling of C-5 iodopyrimidine nucleosides; 1,2-, 1,3-, or 1,ω-dienes; and amines provides a novel and efficient method for the preparation of a wide variety of C-5 aminoalkyl-substituted nucleosides. Adding certain Lewis acids, particularly zinc salts, improves the yields significantly. Secondary amines are the most effective amines for this process. Acyclic and cyclic dienes have been successfully employed. Protection of the 3′- and 5′-hydroxyl groups of iodouridine is required in order to obtain good yields when the coupling process is carried out on 1,3-dienes or long chain or branched non-conjugated dienes.     

低价钛诱导的芳香邻二酮及α－羟基酮的还原偶联反应

低价钛诱导的芳香邻二酮及α－羟基酮的还原偶联反应侯自杰，刘利军，张建华，李裕林（兰州大学有机化学研究所，兰州，７３００００）关键词低价钛，芳香邻二酮，芳香α－羟基酮，偶联羰基化合物在低价钛诱导下的还原偶联反应已有深入研究并在有机合成中得到广泛应用［１...     

Scalar Coupling Constants—Their Analysis and Their Application for the Elucidation of Structures

Since their discovery in the early fifties, scalar/coupling constants have been of great interest to the NMR spectroscopist. Their impact on structure determination by NMR spectroscopy is founded on the fact that the size of the coupling constant is directly related to molecular conformation. Today, for most chemical substances the parameters for the Karplus relationship, which relates the vicinial (3-bond) coupling constant to the dihedral angle, have been determined. In addition to proton–proton distances, the application of coupling constants in modern conformational analysis is indispensable. In the study of larger molecules which are of current interest, more and more involved experiments are necessary in order to overcome signal overlap and increasing line widths. A large number of experimental techniques for the determination of coupling constants has been developed; however, for this reason the choice of the most appropriate experiment to use has become more difficult. This decision must be made carefully to maximize instrument usage and obtain the largest number of couplings with the greatest accuracy possible. Many of the computer programs used in structure calculations can directly apply coupling constant restraints, similar to proton–proton distances developed from NOEs. Therefore, not only is the quality of the structure improved, but the molecular motions (internal dynamics) are better described. In this article, we review the techniques that exist today with particular attention paid to helping the non-expert to choose the appropriate experiment for the problem at hand. In addition, the use of coupling constants in computer simulations are discussed.