Ultrasound-promoted regioselective and stereoselective synthesis of novel spiroindanedionepyrrolizidines by multicomponent 1,3-dipolar cycloaddition of azomethine ylides

A series of novel spiroindanedionepyrrolizidines have been synthesized by multicomponent 1,3-dipolar cycloaddition of a variety of (E)-3-aryl-1-(thiophen-2-yl)prop-2-en-1-ones with unstabilized azomethine ylides generated from ninhydrin and l-proline. The reactions were highly regioselective and stereoselective and were conducted with both conventional heating and ultrasonic irradiation conditions. In general, milder conditions, and moderate improvement in rates, reaction times, and yields were observed when the reactions were performed under ultrasonic conditions. The regioselective and stereoselective nature of the products was established by use of single-crystal X-ray structure and spectroscopic techniques.     

Suberic Acid Acts as a Dissolving Agent as Well as a Crosslinker for Natural Polymers (Carbohydrate and Protein): A Detailed Discussion on the Chemistry Behind the Interaction

The natural polysaccharide chitosan and the natural protein collagen are widely used for the preparation of biopolymer materials in the presence of suitable crosslinkers. In this study, crosslinking feasibility of a dicarboxylic acid, namely suberic acid was tested using chitosan and collagen and in addition, thermal and mechanical properties were also tested for the resulting biopolymers. A 3D scaffold biopolymer material was prepared using chitosan at 1.0% (w/v) in the presence of suberic acid at 0.2% (w/v), similarly collagen 0.5% (w/v) in the presence of suberic acid 0.2% (w/v). Upon interaction, both the biopolymers displayed appreciable mechanical and thermal properties which add value to the biopolymers for biomedical applications. Molecular docking studies suggests the non-covalent interactions between the natural polymers and suberic acid is the reason behind the improved properties.     

Regioselective synthesis of 3,4,6,7-tetrahydro-3,3-dimethyl-9-phenyl-2H-xanthene-1,8(5H,9H)-diones through ascorbic acid catalyzed three-component domino reaction

An efficient, three-component domino reaction of dimedone 1, aromatic aldehydes (2a–o), and 1,3-cyclohexanedione 1a in the regio-selective synthesis of 3,3-dimethyl-9-phenyl-2H-xanthene-1,8(5H,9H)-diones (3a–o) is reported. The desired product, 3 is efficiently promoted by ascorbic acid as an organo catalyst.     

Chemoselective N‐Alkylation of Indoles in Aqueous Microdroplets

Many reactions show much faster kinetics in microdroplets than in the bulk phase. Most reported reactions in microdroplets mirror the products found in bulk reactions. However, the unique environment of microdroplets allows different chemistry to occur. In this work, we present the first chemoselective N‐alkylation of indoles in aqueous microdroplets via a three‐component Mannich‐type reaction without using any catalyst. In sharp contrast, bulk reactions using the same reagents with a catalyst yield exclusively C‐alkylation products. The N‐alkylation yield is moderate in microdroplets, up to 53 %. We extended the scope of the microdroplet reaction and obtained a series of new functionalized indole aminals, which are likely to have biological activities. This work clearly indicates that microdroplet reactions can show reactivity quite different from that of bulk‐phase reactions, which holds great potential for developing novel reactivities in microdroplets.     

Highly fluorescent mono‐substituted poly(arylacetylene)s containing tolane chromophores

A new class of highly fluorescent mono‐substituted polyarylacetylenes ( P1–P3 ) has been successfully prepared with good yields and high molecular weights from a series of phenylethynylene‐substituted arylacetylenes ( M1–M3 ), using W‐based catalyst. These polymers are readily soluble in common organic solvents (e.g., THF, toluene, and chloroform) and thermally stable up to ～350 °C. Both ¹H NMR and IR studies confirmed that all the monomers were selectively polymerized at the terminal triple bond. The ¹H NMR results showed that both P1 and P2 have essentially trans‐polyene backbone structures, while P3 contains significant amounts of both cis‐ and trans‐structures. Coincidently, the photoluminescence (PL) intensity of P3 is also much lower than both P1 and P2 . Nevertheless, the PL intensity of P1–P3 are all much higher than that of PPA , suggesting that the introduction of phenylethynylene group to the phenyl rings of PPA s have made the in general nonemissive PPA s to become highly photoluminescent. Most interestingly, although P1 did not contain any substituent group on its tolane pendant group, it is already highly soluble in common organic solvent and emitting blue fluorescence (416 nm) with a reasonably good quantum yield (0.36). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5483–5498, 2008     

A rapid and highly sensitive method for the determination of glimepiride in human plasma by liquid chromatography-electrospray ionization tandem mass spectrometry: application to a pre-clinical pharmacokinetic study

A sensitive and specific liquid chromatography-positive electrospray ionization-tandem mass spectrometry method has been developed and validated for the determination of glimepiride (GPD) in human plasma. GPD and the internal standard (IS, glibenclamide) were extracted from a small aliquot of human plasma (200 microL) by a simple liquid-liquid extraction technique using ethyl acetate as extraction solvent. The compounds were separated on a YMC Propack, C18, 4.6x50 mm column using a mixture of ammonium acetate buffer, acetonitrile and methanol (30:60:10, v/v) as mobile phase at 0.5 mL/min on an API 4000 Sciex mass spectrometer connected to an Agilent HPLC system. Method validation and pre-clinical sample analysis was performed as per FDA guidelines and the results met the acceptance criteria. GPD and IS were detected without any interference from human plasma matrix. The method was proved to be accurate and precise at linearity range of 0.02-100.00 ng/mL with a correlation coefficient of 0.999. The method was robust with a lower limit of quantitation of 0.02 ng/mL. Intra- and inter-day accuracies for GPD were 88.60-113.50 and 96.82-103.93%, respectively. The inter-day precision was better than 12.21%. This method enabled faster and reliable determination of GPD in a pre-clinical study.     

Metal-Free,Photoredox-Catalyzed Synthesis of Quinazolin-4(3H)-ones and Benzo[4,5]imidazo[1,2-c]quinazolines Using Trialkylamines as Alkyl Synthon

Highly functionalized quinazolin-4(3H)-ones were synthesized from reactions of N-aryl-2-aminobenzamides with trialkylamines under photocatalytic conditions by using eosin Y (EY) as a catalyst. The reaction proceeds under mild conditions in aqueous acetonitrile and has a broad substrate scope. Mechanistic studies disclosed the electron-donor nature of the intermediate 2,3-dihydroquinazolin-4(1H)-one ( 3’ ) in the photocatalytic cycle to afford the 2,3-disubstituted-quinazolin-4(3H)-ones ( 3 ). This methodology has been extended to synthesize benzo [4,5] imidazole[1,2-c] quinazolines and 3 aa on a large scale. Furthermore, the synthesis of potent central nervous system depressant (CNS) drug molecules such as methaqualone ( 3 la ) and mecloqualone ( 3 pa ) was also achieved successfully.     

Thermal Stability and Outgassing Behaviors of High-nickel Cathodes in Lithium-ion Batteries

LiNiO₂-based high-nickel layered oxide cathodes are regarded as promising cathode materials for high-energy-density automotive lithium batteries. Most of the attention thus far has been paid towards addressing their surface and structural instability issues brought by the increase of Ni content (>90 %) with an aim to enhance the cycle stability. However, the poor safety performance remains an intractable problem for their commercialization in the market, yet it has not received appropriate attention. In this review, we focus on the gas generation and thermal degradation behaviors of high-Ni cathodes, which are critical factors in determining their overall safety performance. A comprehensive overview of the mechanisms of outgassing and thermal runaway reactions is presented and analyzed from a chemistry perspective. Finally, we discuss the challenges and the insights into developing robust, safe high-Ni cathodes.     

A convergent approach to the synthesis of multimetallic dithiolene complexes

Controlled base hydrolysis of one or both of the protected 1,2-dithiolene chelates of 1,3,5,7-tetrathia- s-indacene-2,6-dione (OCS 2C 6H 2S 2CO) enables the stepwise synthesis of di- and trimetallic complexes with 1,2,4,5-benzenetetrathiolate as the connector. Treatment of OCS 2C 6H 2S 2CO with MeO (-), followed by [NiBr 2(dcpe)] [dcpe = 1,2-bis(dicyclohexylphosphino)ethane], yields [(dcpe)Ni(S 2C 6H 2S 2CO)] ( 4). The reaction of 4 with EtO (-), followed by [MX 2(dcpe)] (X = halide), yields [(dcpe)Ni(S 2C 6H 2S 2)M(dcpe)] [M = Ni ( 5a), Pd ( 5b)]. Deprotection of the 1,3-dithiol-2-one group of 4, followed by introduction of (1)/ 2 equiv of MX 2 and then I 2, yields the neutral trimetallic compounds [(dcpe)Ni(S 2C 6H 2S 2)] 2M [M = Ni ( 6a), Pt ( 6b)]. Tetrahedralization at nickel is observed in 5a, which density functional theory calculations attribute to second-order Jahn-Teller effects, while 6a and 6b display an end-to-end folding of approximately 46 degrees . A color darkening is observed in moving from 4 to compounds 6 due to the increasing size of the conjugated metal-organic pi system. Intense, broad absorptions in the near-IR are observed for 6a and 6b.     

Carbon nanotubes reinforced with natural/synthetic polymers to mimic the extracellular matrices of bone – a review

The persistent failure of conventional materials used in manufacturing orthopedic implants was due to the deficiency or poor integrations of implant materials to the juxtaposed bone and stress-strain imbalances between the interfaces of tissues and implant materials. Therefore, the fabrication of a suitable bioactive scaffold for bone tissue engineering is considered a vital requisite to mimic the extracellular bone matrix. Numerous researches were reported concerning the fabrication of a suitable bioactive scaffold to improve cell adhesion, proliferation, and differentiation so far. However, for the past two decades, the research on carbon nanotubes (CNTs)-reinforced composites employed in the biomedical field is increasing day-by-day because of its outstanding properties. Moreover, it is essential to choose a biocompatible polymer with greater affinity to act as an extracellular matrix as well as to attract CNTs and in facilitating the homogeneous distribution of CNTs in aqueous and organic solvents. The development of CNTs-based composites in bone tissue engineering is presented in this review based on the last 10 years of research. The detailed information about the structural-functions and defects of bone, and the importance of CNTs-functionalized natural and synthetic polymers, and their potential activity in bone regenerations and bone replacements have been reviewed.