High-Throughput Synthesis and Characterization of Aryl Silicones by Using the Piers–Rubinsztajn Reaction

Arylsilicones are widely exploited for their thermal and optical properties. The creation of phenylsilicone elastomers with specific physical properties is typically done by a “one-off” formulation and test process. Herein, it is demonstrated that high-throughput synthesis methods can be used to rapidly prepare a series of arylsilicone elastomers and then the relative impact of different aryl groups on their physical properties is assessed. Aromatic groups were incorporated into polydimethylsiloxane (PDMS) elastomers by exploiting the relative reactivity of different functional groups in the Piers–Rubinsztajn reaction. To analyze trends in the silicone mechanical properties as a function of increasing aryl concentration—structure/property relationships—libraries of elastomers were both quickly synthesized and characterized by using high-throughput suites starting from low viscosity silicone oils/monomers in 96-well plates. Liquid handling parameters were optimized to effectively work with the silicones. Incorporating aryl instead of alkyl crosslinkers into the PDMS backbone increased the silicone elastomer modulus by approximately 50 % (at a crosslink density of 6 %); elastomers prepared with an aromatic crosslinker with three contact points led to much higher moduli compared with those with one contact point at the same crosslink density. When located at precise rather than random points on the silicone chains, diphenylsilicones had lower moduli than analogous monophenylsilicones.     

Synthesis of Rigid-Flexible Polyetherketone–Based Copolymers

Syntheses of symmetrical etherketone rigid blocks containing from four to ten aromatic rings were performed by a succession of Williamson synthesis steps, followed by deprotection by BBr₃. Solubility decreased upon an increase in number of aromatic rings. Bis-(p-oxy-(p-hydroxyphenyl))benzophenone, a four-ring block, was soluble in the usual solvents (dichloromethane and chloroform), while 6 and 8-ring blocks were only soluble in dichloromethane to which trifluoroacetic acid was added. Rigid-flexible copolyetherketones with very short flexible segments were synthesized by reacting the 8-ring block with dibromo-terminated short alkane chains of 4 to 10 CH₂ units in the presence of sodium hydride. Molar masses were estimated by MALDI-TOF, which was also used to verify the incorporation of the flexible spacers in a regular way. Copolymers are of moderate molecular weights (M_w values from 1240 to 2610 g mol^?1), and of low polydispersity (from 1.02 to 1.17). Rigid blocks and rigid-flexible copolymers show high crystallinity and low solubility, in spite of the presence of the aliphatic spacers along the chain backbone, showing that incorporation of regularly spaced flexible segments does not decrease crystallization significantly. These flexible chains however decrease thermal stability of the copolymers.     

Single-Pot Synthesis of Spiroannulated Dihydrofurans by Iodine–Ammonium Acetate–Mediated Reaction of Dimedone with Aldehydes

Iodine–ammonium acetate–mediated annealation of dimedone with aldehydes led to facile formation of spirodihydrofuran in good yields through tandem Knoevenagel–Michael iodonation and cyclodehydroiodonation reactions in a single pot.     

Synthesis of 1,2-Diazepines by the Bischler–Napieralski Reaction

A new strategy has been proposed for the synthesis of 5H-[1]benzofuro[2,3-d][1,2]diazepines containing two aryl substituents in the diazepine fragment. The key stage of the synthesis is intramolecular cyclization of the corresponding hydrazides under the Bischler–Napieralski reaction conditions.     

Synthesis of Lanthanide Coordination Polymers with Benzophenone-4,4-dicarboxylate: Effect of Lanthanide Contraction on Structures

Introduction Recently, the coordination polymers based on dicar-boxylic acid have been studied extensively for their importance as promising materials.1-7 So the rational design and synthesis of novel coordination polymers with useful functions attract considerable attention. As well known, the design of extended structure with po-tential applications can be realized by starting with connecting ligands capable of binding metal centers strongly and predictably to afford the structures with expe…     

Solid–Gas Phase Synthesis of Coordination Networks by Using Redox-Active Ligands and Elucidation of Their Oxidation Reaction

Formation of coordination networks is a complex process affected by a multitude of factors. Many synthetic strategies have been developed that attempt to control these factors and direct the structure of the final product. Coordination bond formation and structural assembly processes, however, typically take place either in the solution or solid states. In comparison, gas-phase network synthesis remains largely unexplored. Herein, two new two-dimensional coordination networks are obtained from the solid–gas phase reaction between ZnX₂ (X=I, Br) and the redox-active 2,5,8-tri(4-pyridyl)1,3-diazaphenalene (HTPDAP) ligand. Their structures were solved by ab initio powder X-ray diffraction analysis and feature a novel Zn halide trimeric cluster. This strategy is contrasted with a conventional solvothermal synthesis, which led to a one-dimensional coordination polymer instead. The intrinsic electroactive properties of these materials were probed by solid-state cyclic voltammetry measurements, which revealed the presence of HTPDAP and halide-based processes. Chemical oxidation of the two-dimensional networks by using NOPF₆ agent, unexpectedly, led to the formation of a nitrated analog of HTPDAP, the PF₆⁻ salt of diprotonated 4,6,7,9-tetranitro-2,5,8-tris(4-pyridyl)diazaphenalene cation (denoted N-TPDAP), which was isolated and characterized. These results provide deeper insights into the oxidation process of HTPDAP-containing networks and uncover unique redox-induced chemical transformations.     

Synthesis of Liquid Crystalline Polymers with Side Chains

The present paper covers the synthesis and characterization of several intermediate products, monomer, and polymers. 3-{ 2-[ 4-( 4-Nitrophenylazo ) phenoxy] ethyloxycarbonyl} propanoyloxy (2-hydroxy) propyl acrylate (4) was prepared by the ring-opening reaction of glycidyl acrylate with the monoester of succinic acid (3). The polymers (5) with different molecular weights were prepared by the free-radical polymerization. The polymers (5) had liquid crystalline behavior without decomposition as revealed by DSC, optical microscope.     

Synthesis of Large Pore Molecular Sieve VPI-5 by Using Various Organic Amines

The molecular sieve VPI-5 was synthesized by using various organic amines (DEA, Di-PA, DBA, DPenA, TBA, DEOA and TEOA) as the structure-directing agent. The use of DPA enlarged the range of the crystallization temperature from 110℃ to 190℃ in the synthesis of VPI-5, while the use of TEOA changed the composition of the reactants in a broad variety. Diamines are the typical amines in the synthesis of VPI-5. Among them DBA and DPA are the most favorite structure-directing agents for the synthesis of VPI-5 molecular sieve.     

Synthesis of Lanthanide Coordination Polymers with Benzophenone-4,4′-dicarboxylate： Effect of Lanthanide Contraction on Structures

Four lanthanide coordination polymers with benzophenone‐4,4′‐dicarboxylic acid (H₂bpndc) and 1,10‐phenanthroline (phen), [Ln₂(bpndc)₃(phen)] (Ln=La (1), Pr (2) and Tb (3)), [Yb(bpndc)₁₅(phen)].05H₂O (4) were obtained through solvothermal synthesis. The crystallographic data show that 1, 2, and 3 are isostructural, the Ln(III) ions in 1, 2 and 3 are all eight‐ and ten‐coordinated, respectively, and thus the Ln(III) ions are connected by bpndc ligands, resulting in an interpenetrating 3D structure. While in 4, the Yb(III) ions are eight‐coordinated and connected by bpndc ligands into a 3D structure with 1D rhombic channels, which result from the effect of lanthanide contraction from La(III) to Yb(III) ions, and the bpndc ligands in 1, 2, 3, and 4 display three types of coordination modes.     

Synthesis of 1,3-Diketones by Reaction of α-Haloketones with Acyl Cyanides Promoted by Samarium Diiodide

α-Haloketones reacted with acyl cyanides to form 1,3-diketones in the presence of samarium diiodide. The reaction was assumed to proceed via a mechanism involving samarium enolates formed in situ from α-haloketones.     

Stereoselective Synthesis of C-Glycosides by Suzuki Cross-coupling Reaction

Carbohydrates and their conjugates have been recognized to play a wide variety of metabolic roles in numerous biological processes.[1] Various modified sugars and analogues have been recently synthesized for further investigation of glycosidase reactions and for the development of specific glycosidase inhibitors.[2] As one of the most important carbohydrate mimics, C-glycosides have attracted great attention due to their stability to chemical or enzymatic hydrolysis of the glycosidic linkage. A number of methodologies for the preparation of C-glycosides have been extensively investigated.[3] We have recently reported the syntheses of novel C-glycosyl amino acids and amino-C-disaccharides possessing a ketose form via the stereoselective 1,3-dipolar cycloaddition of exo-methylenesugars (1) and nitrones.[4,5] As a continuation of our research on the synthesis of C-glycosides using exo-methylenesugar as the precursor, we wish to describe here a stereoselective synthesis of C-glycosides by Suzuki cross-coupling reaction.     

Synthesis of Functionalized Δ3 Phosphabenzenes by Means of Diels Alder Reaction with Phosphaalkenes

Abstract

Diels Alder reaction provides an easy and general access to functionalized Δ³ phosphabenzenes after aromatization with the possibilities of introducing the functional group either with the diene or the phosphaalkene.     

Facile Synthesis of β‐Azidocyclopropanecarboxylates by MIRC Reaction

Abstract

Two β‐azidocyclopropanecarboxylates are readily synthesized from β‐bromoalkyliden malonates via a Michael–initiated ring closure (MIRC) reaction in moderate yields, which are regarded as precursors of β‐aminocyclopropanecarboxylic acids.     

Anionic Synthesis of Primary and Secondary Amine-Functionalized Polymers Using Imine Chemistry

There has been growing interest and research on new synthetic methods for thepreparation of well-defined polymers with chain-end functional groups[1～ 7] . Thesefunctional groups in polymers can participate in reversible ionic association;chainextension,branching,or crosslinking reactions with polyfunctional reagents;couplingand linking with reactive groups in other oligomer or polymer chains;and initiation ofpolymerization of other monomers[4～ 6] . The methodology of living anionic polyme-ri…     

Synthesis of Dendritic-Linear Block Copolymers by Atom Transfer Radical Polymerization

Polymers and copolymers with complex, yet well-defined architectures are drawing significant attentions in the search for materials with excellent properties. Of these macromolecular structures, dendritic-linear block copolymers consisting of covalently bound linear and dendritic segments have shown interesting solution, solid-state, and interfacial properties. As a novel polymerization approach, atom transfer radical polymerization (ATRP) has been attracting increasing interest recently, sin…     

Reaction of Azalactone with Hydroxylamine Synthesis of β -Aminophenylalanine

Treatment of azlactones^1–5 with hydroxylamine under different experimental conditions yields hydroxamic acids (2), disubstituted hydroxamic acids (3), β -hydroxylamino-hydroxamic acids (10) and several other compounds. The acid (10a) upon Catalytic hydrogenation gives M-benzoylamino-β aminophenylalanine amide (15) which gave β -aminophenylalanine (16) on hydrolysis.     

Synthesis of α,β-Unsaturated Nitriles by Reaction of Haloacetonitrile with Carbonyl Compounds Mediated by Tri-n-butylstibine

α,β-Unsaturated nitriles were synthesized by the reaction of haloacetonitriles with carbonyl compounds mediated by tri-n-butylstibine in excellent yields.