journal
https://read.qxmd.com/read/34108738/flow-photochemical-syntheses-of-trans-cyclooctenes-and-trans-cycloheptenes-driven-by-metal-complexation
#21
JOURNAL ARTICLE
Jessica E Pigga, Joseph M Fox
trans -Cyclooctenes and trans -cycloheptenes have long been the subject of physical organic study, but the broader application had been limited by synthetic accessibility. This account describes the development of a general, flow photochemical method for the preparative synthesis of trans -cycloalkene derivatives. Here, photoisom erization takes place in a closed-loop flow reactor where the reaction mixture is continuously cycled through Ag(I) on silica gel. Selective complexation of the trans -isomer by Ag(I) during flow drives an otherwise unfavorable isomeric ratio toward the trans -isomer...
March 2020: Israel Journal of Chemistry
https://read.qxmd.com/read/34045772/an-expedient-route-to-9-arylmethylanthracene-derivatives-via-tandem-ni-catalyzed-alkene-dicarbofunctionalization-and-acid-promoted-cyclization-aromatization
#22
JOURNAL ARTICLE
Doleshwar Niroula, Rishi R Sapkota, Roshan K Dhungana, Bijay Shrestha, Ramesh Giri
We report a nickel-catalyzed one pot synthesis of 9-arylmethylanthracene motifs, which find applications in medicinal and material chemistry. In this synthesis, we apply three component alkene dicarbofunctionalization of 2-vinylaldimines with aryl iodides and arylzinc reagent to generate a 1,1,2-diarylethyl scaffold, which then undergoes an acidpromoted cyclization followed by aromatization to furnish 9-arylmethylanthracene cores. With the new method, a number of differently-substituted 9-arylmethylanthracene derivatives can be synthesized in good yields...
March 2020: Israel Journal of Chemistry
https://read.qxmd.com/read/33986554/photoredox-mediated-net-neutral-radical-polar-crossover-reactions
#23
JOURNAL ARTICLE
Rebecca J Wiles, Gary A Molander
Radical/Polar Crossover (RPC) chemistry is a rapidly growing subset of photoredox catalysis that is characterized by transformations featuring both radical and ionic modes of reactivity. Net-neutral RPC is particularly interesting in that both the single-electron oxidation and reduction steps occur through interaction with the photocatalyst, thus precluding the need for exogenous oxidants or reductants. As such, these transformations facilitate rapid incorporation of molecular complexity while maintaining mild reaction conditions...
March 2020: Israel Journal of Chemistry
https://read.qxmd.com/read/33859442/regioselective-arylboration-of-1-3-butadiene
#24
JOURNAL ARTICLE
Allison M Bergmann, Stephen R Sardini, Kevin B Smith, M Kevin Brown
A method for the regioselective 1,2-arylboration of 1,3-butadiene, a feedstock chemical, is reported. The reactions result in the formation of products that can be easily elaborated to other structures. The mechanistic details of this process are also discussed.
March 2020: Israel Journal of Chemistry
https://read.qxmd.com/read/33785969/transition-metal-catalyzed-1-2-carboboration-of-alkenes-strategies-mechanisms-and-stereocontrol
#25
JOURNAL ARTICLE
Zhen Liu, Yang Gao, Tian Zeng, Keary M Engle
During the past decade, many research groups have described catalytic methods for 1,2-carboboration, allowing access to structurally complex organoboronates from alkenes. Various transition metals, especially copper, palladium, and nickel, have been widely used in these reactions. This review summarizes advances in this field, with a special focus on the catalytic cycles involved in different metal-catalyzed carboboration reactions, as well as the regio- and stereochemical consequences of the underlying mechanisms...
March 2020: Israel Journal of Chemistry
https://read.qxmd.com/read/33664525/pd-catalyzed-c-c-c-n-and-c-o-bond-forming-difunctionalization-reactions-of-alkenes-bearing-tethered-aryl-alkenyl-triflates
#26
JOURNAL ARTICLE
Derick R White, Evan C Bornowski, John P Wolfe
Over the past few years our group has described a new type of alkene difunctionalization reaction in which aryl or alkenyl triflates bearing tethered alkenes are coupled with various nucleophiles to afford carbocyclic products. The products are formed in moderate to good chemical yield, with generally high levels of stereoselectivity. Our progress to date in this area, which includes reactions of amine, alcohol, enolate, and indole nucleophiles, is described in this review.
March 2020: Israel Journal of Chemistry
https://read.qxmd.com/read/33446940/enantioselective-synthesis-of-alkyl-allyl-ethers-via-palladium-catalyzed-redox-relay-heck-alkenylation-of-o-alkyl-enol-ethers
#27
JOURNAL ARTICLE
Matthew B Prater, Matthew S Sigman
Herein we report a transformation that generates an array of enantiomerically enriched, alkyl allyl ethers. Cyclic, acyclic, and heteroatom-bearing alkenyl triflates undergo an enantioselective, palladium-catalyzed C-C bond formation with diverse acyclic O -alkyl enol ethers in good yields and excellent enantioselectivities.
March 2020: Israel Journal of Chemistry
https://read.qxmd.com/read/33442068/stereospecific-cross-coupling-reactions-provide-conformationally-biased-arylalkanes-with-anti-leukemia-activity
#28
JOURNAL ARTICLE
Amberly B Sanford, Emily J Tollefson, Elizabeth R Jarvo
A focused small library of carbamates and alcohols was prepared employing stereospecific Kumada-ring opening reactions of tetrahydropyrans. The core framework of the library members is acyclic and incorporates 1,3-substituents, to provide a conformational bias in avoiding syn-pentane interactions. A new compound with micromolar activity against MOLT-4, CCRF-CEM, and HL-60(TB) leukemia cell lines was identified from this series.
March 2020: Israel Journal of Chemistry
https://read.qxmd.com/read/33132416/enantioselective-catalysis-of-an-anionic-oxy-cope-rearrangement-enabled-by-synergistic-ion-binding
#29
JOURNAL ARTICLE
C Rose Kennedy, Bo Young Choi, Mary-Grace R Reeves, Eric N Jacobsen
Charge-accelerated rearrangements present interesting challenges to enantioselective catalysis, due in large part to the competing requirements for maximizing reactivity (ion-pair separation) and stereochemical communication. Herein, we describe application of a synergistic ion-binding strategy to catalyze the anionic oxy-Cope rearrangement of a symmetric bis -styrenyl allyl alcohol in up to 75:25 e.r. Structure-reactivity-selectivity relationship studies, including linear free-energy-relationship analyses, with bifunctional urea catalysts indicate that H-bonding and cation-binding interactions act cooperatively to promote the chemo- and enantioselective [3,3]-rearrangement...
March 2020: Israel Journal of Chemistry
https://read.qxmd.com/read/33071305/solvent-effects-on-the-selectivity-of-palladium-catalyzed-suzuki-miyaura-couplings
#30
JOURNAL ARTICLE
Emily K Reeves, Olivia R Bauman, Gunner B Mitchem, Sharon R Neufeldt
The use of polar solvents MeCN or dimethylformamide (DMF) was previously shown to induce a selectivity switch in the Pd/P t Bu3 -catalyzed Suzuki-Miyaura coupling of chloroaryl triflates. This phenomenon was attributed to the ability of polar solvents to stabilize anionic transition states for oxidative addition. However, we demonstrate that selectivity in this reaction does not trend with solvent dielectic constant. Unlike MeCN and DMF, water, alcohols, and several polar aprotic solvents such as MeNO2 , acetone, and propylene carbonate provide the same selectivity as nonpolar solvents...
March 2020: Israel Journal of Chemistry
https://read.qxmd.com/read/32669731/base-assisted-c-h-bond-cleavage-in-cross-coupling-recent-insights-into-mechanism-speciation-and-cooperativity
#31
JOURNAL ARTICLE
Brad P Carrow, Jessica Sampson, Long Wang
This review analyzes recent mechanistic studies that have provided new insights into how the structure of a metal complex influences the rate and selectivity of base-assisted C-H cleavage. Partitioning a broader mechanistic continuum into classes delimited by the polarization between catalyst and substrate during C-H cleavage is postulated as a method to identify catalysts favoring electrophilic or nucleophilic reactivity patterns, which may be predictive based on structural features of the metal complex (i...
March 2020: Israel Journal of Chemistry
https://read.qxmd.com/read/32523163/recent-advances-in-transition-metal-catalyzed-functionalization-of-gem-difluoroalkenes
#32
JOURNAL ARTICLE
Suvajit Koley, Ryan A Altman
gem -Difluorinated alkenes are readily accessible building blocks that can undergo functionalization to provide a broad spectrum of fluorinated and non-fluorinated products. Herein, we review recent (since 2017) transition metal-catalyzed transformations of these specialized alkenes and summarize general reactivity patterns of these reactions. Many transition metal-catalyzed reactions undergo net C-F bond functionalization reactions to deliver monofluorinated products. These reactions typically proceed through β -fluoro alkylmetal intermediates that readily eliminate a β -fluoride to deliver monofluoroalkene products...
March 2020: Israel Journal of Chemistry
https://read.qxmd.com/read/34168383/disulfide-containing-macromolecules-for-therapeutic-delivery
#33
JOURNAL ARTICLE
Ziwen Jiang, S Thayumanavan
Development of macromolecules provides applicable platforms for the delivery of therapeutics. In this general overview, we focus on the design principles of synthetic polymers, with disulfide bonds located in either the polymer backbone or side chains. We also discuss the role of disulfide bonds, as well as the remaining questions to better understand their applications in therapeutic delivery systems.
January 2020: Israel Journal of Chemistry
https://read.qxmd.com/read/34045771/protein-interactions-with-nanoparticle-surfaces-highlighting-solution-nmr-techniques
#34
JOURNAL ARTICLE
Y Randika Perera, Rebecca A Hill, Nicholas C Fitzkee
In the last decade, nanoparticles (NPs) have become a key tool in medicine and biotechnology as drug delivery systems, biosensors and diagnostic devices. The composition and surface chemistry of NPs vary based on the materials used: typically organic polymers, inorganic materials, or lipids. Nanoparticle classes can be further divided into sub-categories depending on the surface modification and functionalization. These surface properties matter when NPs are introduced into a physiological environment, as they will influence how nucleic acids, lipids, and proteins will interact with the NP surface...
November 2019: Israel Journal of Chemistry
https://read.qxmd.com/read/31680702/cysteine-rich-antifungal-proteins-from-filamentous-fungi-are-promising-bioactive-natural-compounds-in-anti-candida-therapy
#35
REVIEW
László Galgóczy, Annie Yap, Florentine Marx
The emerging number of life-threatening invasive fungal infections caused by drug-resistant Candida strains urges the need for the development and application of fundamentally new and safe antifungal strategies in the clinical treatment. Recent studies demonstrated that the extracellular cysteine-rich and cationic antifungal proteins (crAFPs) originating from filamentous fungi, and de novo designed synthetic peptide derivatives of these crAFPs provide a feasible basis for this approach. This mini-review focuses on the global challenges of the anti- Canidia therapy and on the crAFPs as potential drug candidates to overcome existing problems...
May 2019: Israel Journal of Chemistry
https://read.qxmd.com/read/31516159/tracking-co-release-in-cells-via-the-luminescence-of-donor-molecules-and-or-their-by-products
#36
JOURNAL ARTICLE
Tatiana Soboleva, Lisa M Berreau
Carbon monoxide (CO) is a bioactive signalling molecule that is produced endogenously via the breakdown of heme. Beneficial health effects associated with the delivery of CO gas have spurred the development of CO-releasing molecules (CORMs) that can be used to provide specific amounts of the gas. In addition to their potential use as therapeutics, CORMs are needed to provide insight into the biological targets of CO. In this regard, light-activated CO-releasing molecules (photoCORMs), are valuable for examining the effects of localized CO release...
May 2019: Israel Journal of Chemistry
https://read.qxmd.com/read/31244492/in-search-of-bioactivity-phyllobilins-an-unexplored-class-of-abundant-heterocyclic-plant-metabolites-from-breakdown-of-chlorophyll
#37
REVIEW
Simone Moser, Bernhard Kräutler
The fate of the green plant pigment chlorophyll (Chl) in de-greening leaves has long been a fascinating biological puzzle. In the course of the last three decades, various bilin-type products of Chl breakdown have been identified, named phyllobilins (PBs). Considered 'mere' leftovers of a controlled biological Chl detoxification originally, the quest for finding relevant bioactivities of the PBs has become a new paradigm. Indeed, the PBs are abundant in senescent leaves, in ripe fruit and in some vegetables, and they display an exciting array of diverse heterocyclic structures...
May 2019: Israel Journal of Chemistry
https://read.qxmd.com/read/33833470/multicomponent-porphyrin-based-tetragonal-prismatic-metallacages-and-their-photophysical-properties
#38
JOURNAL ARTICLE
Zhengqing Zhao, Zeyuan Zhang, Heng Wang, Xiaopeng Li, Mingming Zhang
Multicomponent coordination-driven self-assembly has proved to be a convenient approach to prepare advanced supramolecular coordination complexes (SCCs), especially for those with three-dimensional structures. Herein, we report the preparation of three tetragonal prismatic cages via the self-assembly of Pt(PEt3 )2 (OTf)2 , three different linear dipyridyl ligands and porphyrin-based sodium benzoate ligands. Due to the efficient charge separation in the coordination process of Pt(PEt3 )2 (OTf)2 with pyridine and carboxylic acid and the directionality of metal-coordination bonds, these cages were prepared in high isolated yields (more than 90%)...
March 2019: Israel Journal of Chemistry
https://read.qxmd.com/read/33833469/stepwise-self-assembly-and-dynamic-exchange-of-supramolecular-snowflakes
#39
JOURNAL ARTICLE
Zhe Zhang, Heng Wang, Junjuan Shi, Pingshan Wang, Changlin Liu, Ming Wang, Xiaopeng Li
Snowflake, a highly symmetrical hexagram figure, is challenging to be expressed by chemistry/supramolecular chemistry due to the complex structure. Herein, we have constructed super snowflake supramolecules using terpyridine (tpy)-based metal-organic building blocks with <tpy-Ru(II)-tpy> and <tpy-Zn(II)-tpy> connectivities through stepwise strategies in high yield. The structures were characterized by multi-dimensional mass spectrometry and multi-dimensional NMR spectrometry. In order to address the stability/tolerance of our designed super snowflake structures, ligand exchange behaviors between different supramolecules with various arm length were fully investigated by mass spectrometry...
March 2019: Israel Journal of Chemistry
https://read.qxmd.com/read/31762490/from-active-sites-to-machines-a-challenge-for-enzyme-chemists
#40
JOURNAL ARTICLE
Chaitan Khosla
As researchers who study enzyme chemistry embrace increasingly complex systems, especially biological machines, our attention is also shifting from steps involving covalent bond formation or cleavage to those that exclusively involve changes in non-covalent bonding. Assembly line polyketide synthases are an example of this growing challenge. By now, the chemical reactions underpinning polyketide biosynthesis can be unequivocally mapped to well-defined active sites and are, for the most part, readily explicable in the language of physical organic chemistry...
February 2019: Israel Journal of Chemistry
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