ChemInform Abstract: Transition Metal-Catalyzed Carbon-Carbon Bond Formation Suzuki, Heck, and Sonogashira Reactions Using Microwave and Microtechnology (original) (raw)

Ninhydrin in synthesis of heterocyclic compounds

Arkivoc, 2015

Ninhydrin has been utilized in many heterocyclic preparations and considered as an important building block in organic synthesis. There is a wide range of reactions that include ninhydrin in the synthesis of heterocyclic compounds. This review highlights the advances in the use of ninhydrin as starting material in the synthesis of various organic compounds and drugs in a fully comprehensive way, from its first isolation in 1910 to the end of 2013. There is also a diversity of multi-component reactions of ninhydrin and we highlight the recent reports in this review.

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

Beilstein Journal of Organic Chemistry, 2015

The present review summarizes primary publications on the cross-dehydrogenative C-O coupling, with special emphasis on the studies published after 2000. The starting compound, which donates a carbon atom for the formation of a new C-O bond, is called the CH-reagent or the C-reagent, and the compound, an oxygen atom of which is involved in the new bond, is called the OH-reagent or the O-reagent. Alcohols and carboxylic acids are most commonly used as O-reagents; hydroxylamine derivatives, hydroperoxides, and sulfonic acids are employed less often. The cross-dehydrogenative C-O coupling reactions are carried out using different C-reagents, such as compounds containing directing functional groups (amide, heteroaromatic, oxime, and so on) and compounds with activated C-H bonds (aldehydes, alcohols, ketones, ethers, amines, amides, compounds containing the benzyl, allyl, or propargyl moiety). An analysis of the published data showed that the principles at the basis of a particular cross-dehydrogenative C-O coupling reaction are dictated mainly by the nature of the C-reagent. Hence, in the present review the data are classified according to the structures of C-reagents, and, in the second place, according to the type of oxidative systems. Besides the typical cross-dehydrogenative coupling reactions of CH-and OH-reagents, closely related C-H activation processes involving intermolecular C-O bond formation are discussed: acyloxylation reactions with ArI(O 2 CR) 2 reagents and generation of O-reagents in situ from C-reagents (methylarenes, aldehydes, etc.).

Soft Self-Healing Nanocomposites

Frontiers in Materials, 2019

This review article provides an overview of the research and applications of soft self-healing polymers and their nanocomposites. A number of concepts based on physical and chemical interactions have been explored to create dynamic and reversible gel and elastomer networks, each strategy presenting its own advantages and drawbacks. Physical interactions include supramolecular interactions, ionic bonding, hydrophobic interactions, and multiple intermolecular interactions. Such networks do not require external stimulus and are capable of multiple self-healing cycles. They are generally characterized by a rapid but limited healing efficiency. The addition of nanofillers enhances the mechanical strength of the soft networks as in conventional gels and elastomers, and do not compromise the network healing dynamics. In certain cases, nanofillers moreover trigger the healing process through e.g., multi-complexation processes between each component. Chemical interactions include Diels-Alder reactions and disulphide, imine, boronate ester, or acylhydrazones bonding, and are usually triggered with an external stimulus. The resulting healing is efficient, leading to good mechanical properties, but is generally slow at ambient temperatures, and dynamic chemical interactions are only reversible at higher temperatures. Conductive nanofillers were reported to speed up the healing process in such systems owing to their energy absorption properties. The challenges with nanofillers remain their functionalization and dispersion within the self-healing formulations. Soft self-healing gels and nanocomposites find applications in engineering such as coatings, sensors, actuators and soft robotics, and in the bio-medical field, including drug delivery, adhesives, tissue engineering and wound healing.

Asymmetric Brominative Dearomatization of Naphthols Catalyzed by Chiral Copper Complexes

Advanced Synthesis & Catalysis, 2018

A fast and highly enantioselective brominative dearomatization of naphthols catalyzed by diphenylaminelinked bis(oxazoline)-Cu(OTf)2 complexes has been developed. The corresponding products of chiral naphthalenones bearing a Br-containing tetrasubstituted stereogenic center could be obtained with good to excellent enantioselectivities (up to 95% ee) in excellent yields (up to 97% yield) within short reaction times.

Directed lithiation of simple aromatics and heterocycles for synthesis of substituted derivatives

ARKIVOC: archive for organic chemistry

Directed lithiation of substituted aromatics and heterocycles containing a directing metalating group with alkyllithium in anhydrous tetrahydrofuran or diethyl ether at low temperature provides the corresponding lithium intermediates. Reaction of the lithium reagents obtained in situ with various electrophiles gives the corresponding substituted derivatives in high yields. The process has been applied for various derivatives and has proven to be a convenient method for modification of ring systems. This brief review highlights the importance of directing metalating groups in directed lithiation of simple aromatic compounds and some common heterocycles as a tool for regioselective substitution.

Adenovirus pyelonephritis in the late posttransplant period

Kidney international, 2017

Readily available ascorbic acid was discovered as an environmentally benign hydrogen bond donor (HBD) for the synthesis of cyclic organic carbonates from CO2 and epoxides in the presence of nucleophilic co-catalysts. The ascorbic acid/TBAI (TBAI: tetrabutylammonium iodide) binary system could be applied for the cycloaddition of CO2 to various epoxides under ambient or mild conditions. DFT calculations and catalysis experiments revealed an intriguing bifunctional mechanism in the step of CO2 insertion involving different hydroxyl moieties (enediol, ethyldiol) of the ascorbic acid scaffold.

Artificial bioconjugates with naturally occurring linkages: the use of phosphodiester

Beilstein Journal of Organic Chemistry, 2018

Artificial orthogonal bond formations such as the alkyne–azide cycloaddition have enabled selective bioconjugations under mild conditions, yet naturally occurring linkages between native functional groups would be more straightforward to elaborate bioconjugates. Herein, we describe the use of a phosphodiester bond as a versatile option to access various bioconjugates. An opposite activation strategy, involving 5’-phosphitylation of the supported oligonucleotides, has allowed several biomolecules that possess an unactivated alcohol to be directly conjugated. It should be noted that there is no need to pre-install artificial functional groups and undesired and unpredictable perturbations possibly caused by bioconjugation can be minimized.

Surprisingly facile CO 2 insertion into cobalt alkoxide bonds: A theoretical investigation

Beilstein Journal of Organic Chemistry, 2015

Exploiting carbon dioxide as co-monomer with epoxides in the production of polycarbonates is economically highly attractive. More effective catalysts for this reaction are intensively being sought. To promote better understanding of the catalytic pathways, this study uses density functional theory calculations to elucidate the reaction step of CO2 insertion into cobalt(III)–alkoxide bonds, which is also the central step of metal catalysed carboxylation reactions. It was found that CO2 insertion into the cobalt(III)–alkoxide bond of [(2-hydroxyethoxy)CoIII(salen)(L)] complexes (salen = N,N”-bis(salicyliden-1,6-diaminophenyl)) is exothermic, whereby the exothermicity depends on the trans-ligand L. The more electron-donating this ligand is, the more exothermic the insertion step is. Interestingly, we found that the activation barrier decreases with increasing exothermicity of the CO2 insertion. Hereby, a linear Brønsted–Evans–Polanyi relationship was found between the activation energy...

Recent Progress in Ethylene Polymerization Catalyzed by Ni and Pd Catalysts

European Journal of Inorganic Chemistry, 2018

Table of Contents Key Topic: Catalysis This review offers fresh guidelines for rational design of high-performance catalytic systems in the consideration of the structural effects of catalysts (including the effects from ligands and metals) as well as the reaction conditions and synthesis of polyethylene with unique microstructures and properties.

Molecular Networks in Dynamic Multilevel Systems

Chemistry - A European Journal

Multilevel dynamic systems based in Orthogonal Reactions Simultaneous one-pot setting Some pairs of orthogonal reversible reactions, which can be simultaneously activated, are disulfide and boronic ester 70 exchanges, [7] disulfide and hydrazone [8] or imine [9] exchanges, and imine exchange and olefin metathesis. [10] One recent example of a three dynamic covalent reaction system was reported by Anslyn and co-workers, who studied the reversibility and orthogonality of simultaneous hydrazone 75 exchange (compounds 1-8), thiol addition to conjugate acceptors (compounds 9-16) and boronic ester exchange (compounds 17-24, Figure 2). [11] Under appropriate conditions (3:1 CD3OD/HEPES, pH = 7.4), all the three reactions can proceed without chemical interference, giving place to a set of 80 three isolated subnetworks with identical network structures (Figure 2).