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PubMed Journal Database | The Journal of organic chemistry RSS

08:00 EDT 26th May 2019 | BioPortfolio

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Showing PubMed Articles 1–25 of 1,700+ from The Journal of organic chemistry

Correction to Intrinsically Safe and Shelf-Stable Diazo-Transfer Reagent for Fast Synthesis of Diazo Compounds.

Palladium catalyzed template directed C-5 selective olefination of thiazoles.

An efficient method has been developed to afford highly C-5 selective olefination of thiazole derivatives utilizing bifunctional template in an intermolecular fashion. Coordinative interaction between substrates and metal chelated template backbone plays crucial role for high selectivity. Excellent selectivity for C-5 position was observed while mono substituted (2- or 4-) or even more challenging unsubstituted thiazole were employed.

Sustainable Alkylation of Nitriles with Alcohols by Manganese Catalysis.

A general and chemoselective catalytic alkylation of nitriles using a homogenous non-precious manganese catalyst is presented. This alkylation reaction uses naturally abundant alcohols and readily available nitriles as coupling partners. The reaction tolerates a wide range of functional groups and heterocyclic moieties, efficiently providing useful cyanoalkylated products with water as the only side product. Importantly, methanol can be used as a C1 source and the chemoselective C-methylation of nitriles is...

A Biomimetic Phosphate Catalyzed Pictet-Spengler Reaction for the Synthesis of 1,1'-Disubstituted and Spiro-Tetrahydroisoquinoline Alkaloids.

Tetrahydroisoquinoline alkaloids are an important group of compounds that exhibit a range of bioactivities. Here, a phosphate buffer catalyzed Pictet-Spengler reaction (PSR) using unreactive ketone substrates is described. A variety of 1,1'-disubstituted and spiro-tetrahydroisoquinoline alkaloids were readily prepared in one-step and high yields, highlighting the general applicability of this approach. This study features the role of phosphate in the aqueous-based PSR and provides an atom-efficient, sustain...

Photorearrangement of Quinoline-Protected Dialkylanilines and the Photorelease of Aniline-Containing Biological Effectors.

The direct release of dialkylanilines was achieved by controlling the outcome of a photorearrangement reaction promoted by the (8-cyano-7-hydroxyquinolin-2-yl)methyl (CyHQ) photoremovable protecting group (PPG). The substrate scope was investigated to obtain structure-activity relationships and to propose a reaction mechanism. Introducing a methyl substituent at the 2-methyl position of the CyHQ core enabled the bypass of the photorearrangement and significantly improved the aniline release efficiency. We s...

A Photoredox/Cobalt-Catalyzed Phosphinyloxy Radical addition/Cyclization Cascade: Synthesis of Phosphaisocoumarins.

A novel visible-light photoredox catalyzed phosphinyloxy radical addition/cyclization cascade of arylphosphinic acids or arylphosphonic acid monoesters with alkynes has been developed, which provides an efficient and practical access to various phosphaisocoumarins by using a dual catalytic system containing an acridinium photosensitizer and a cobaloxime proton-reducing catalyst, [Co(dmgH)2]PyCl at ambient temperature. This method has advantages of broad substrate scope, mild condition as well as without any...

Deciphering the origin of enantioselectivity on the cis-cyclopropanation of styrene with enantiopure dichloro,di-gold(I)-SEGPHOS carbenoids generated from propargylic esters.

The stereoselective synthesis of cis-disubstituted cyclopropanes by the Au(I)/PPh3-catalyzed cycloaddition of propargylic esters and styrene has been studied using density functional theory calculations. The computed mechanistic scheme involves the rate-limiting 1,2-rearrangement of the propargylic ester with the π-coordinated gold complex, followed by the (2+1)-cheletropic reaction of styrene with the alkenyl-Au(I) carbene intermediate to afford the cis-disubstituted cyclopropane derivative in a high cis/...

Substrate Self-Assisted Secondary Bond Activation of Allylic Alcohol in Tsuji-Trost Reaction Revealed by NMR Methods.

The first experimental evidences for palladium-catalyzed secondary bond activation of allylic alcohols in Tsuji-Trost reaction were provided by NMR methods, such as variable-temperature 1H NMR, Diffusion-Ordered SpectroscopY (DOSY), Job's method, 1H NMR titration, and Nuclear Overhauser Enhancement SpectroscopY (NOESY). The experimental results revealed that the substrate self-assisted activation of allylic alcohols is probably performed via a 1:1 binding six-membered-ring complex, which are formed by the f...

Organocatalytic Synthesis of Benzazetidines by Trapping Hemiaminals with Protecting Groups.

Benzazetidines are highly strained and inherently unstable heterocycles. There are only few methodologies for assembling these compounds. Here, a protocol is presented to trap an elusive cyclic, 4-membered hemiaminal structure. This method affords several benzazetidine in moderate to good yields (up to 81%), it uses inexpensive materials and does not require catalysts based on transition metals. The high ring strain energy of these benzazetidine systems was estimated by DFT calculations to be about 32 kcal ...

Cp*Rh(III)-Catalyzed C-H bond Difluorovinylation of indoles with α,α-difluorovinyl tosylate.

An unprecedented Rh(III)-Catalyzed C-H bond difluorovinylation of indoles has been successfully developed and this method provided an example of direct difluorovinylation reaction through C-H bond activation which was rarely reported. In this context, N-ethoxycarbamoyl was serving as the directing group and 2,2-difluorovinyl tosylates was used for the construction of difluorovinyl substituted indoles. This method provided a practical strategy for difluorovinylation of indoles with moderate to good yields an...

Meso-bis(ethynyl) vs Meso-bis(aryl) Calix4pyrroles: Dimensionally Well-Modulated Receptors that can Regulate the Anion Binding Domains.

Meso-substituted calix[4]pyrroles 2-6 containing direct meso-ethynyl linker displayed high binding affinities and unique conformational features on halide anion binding. A general conformational bias for the equatorial alignments of the meso-(aryl)ethynyl groups were observed in the host-halide complexes which was attributed to the repulsive anion-alkyne interactions and released steric strain. Such conformational features of host-halide complexes persisted even in case of calix[4]pyrrole 6 bearing cationic...

Palladium-Catalyzed Cascade Intramolecular Cyclization and Allylation of Enynoates with Allylic Alcohols.

A Pd(II)-catalyzed mild and highly regioselective 6-endo cyclization/allylation reactions of enynoates with simple allylic alcohols has been developed. Under mild reaction conditions, the vinyl palladium species generated in situ after cyclization could insert C-C double bond of allylic alcohol through cross-coupling reaction and lead to the formation of allyl pyrone via β-OH elimination. This cascade cross coupling reaction represents a direct and atom economic methodology for the con-struction of novel a...

Total Synthesis of Berkeleylactone A.

The first total synthesis of the potent antibiotic Berkeleylactone A is described in 10 steps with an overall yield of 9.5%. A key step of our concise route is a late stage, highly diastereoselective, sulfa-Michael addition. The 16-membered macrocyclic lactone was formed via RCM and subsequent chemoselective reduction. The absolute stereochemical configuration was confirmed by single crystal X-ray analysis. Synthetic berkeleylactone A was tested against several MRSA strains and its potent antibacterial acti...

Chemo- and Regioselective Asymmetric Synthesis of Cyclic Enamides Through the Catalytic Umpolung Organocascade Reaction of α-Imino Amides.

The efficient chemo- and regioselective catalytic asymmetric syntheses of enamides, which are important core structures of bioactive natural products, have been achieved through the first umpolung organocascade reaction of α-imino amides. A variety of enamides have been synthesized enantioselectively in high yields with up to 99% ee. Notably, both enantiomers of the products can be selectively prepared by the simple pretreatment of the substrate. Mechanistic studies reveal that E/Z-geometry information fro...

Diastereoselective α-Amination of N- tert-Butanesulfinyl Imidates Using N-Aryl- N-diphenylphosphinyldiazenes.

Diastereoselective α-amination of N- tert-butanesulfinyl imidates has been developed using N-aryl (or N- tert-butyl) N-diphenylphosphinyldiazenes as nitrogen sources. The chiral 1-azaenolates derived from imidates undergo nucleophilic addition with diazenes to give α-hydrazino imidates in good yields.

Synthesis of Sterically Hindered β-Diketones via Condensation of Acid Chlorides with Enolates.

Bulky β-diketones have rarely exceeded dipivaloylmethane (DPM) in steric demand, largely due to synthetic limitations of the Claisen condensation. This work demonstrates hindered acid chlorides to be selective electrophiles in non-coordinating solvents for condensations with enolates. An improved synthesis of DPM is described (90% yield), and crowded β-diketones featuring bulky o-biphenyl or m-terphenyl fragments were prepared in good to excellent yields. These compounds are anticipated to have a steric p...

Catalyst-Free Synthesis of 2-Anilinoquinolines and 3-Hydroxyquinolines via Three-Component Reaction of Quinoline N-oxides, Aryldiazonium salts and Acetonitrile.

A rapid microwave-assisted catalyst-free, three-component synthesis of various 2-anilinoquinolines from quinoline N-oxides and aryldiazonium salts in acetonitrile under microwave irradiation is reported. This reaction utilizes acetonitrile as a single nitrogen source and involves the formation of two new C-N bonds via formal [3+2] cycloaddition reaction. In the case of 2-substituted quinolines, 3-hydroxyquinoline was observed as the main product via 1,3 shift of oxygen atom from N-oxide to the C3 position o...

Enantiodivergent Approach to the Synthesis of cis-2,6-Disubstituted Piperidin-4-ones.

Enantiopure β-amino ketone derivatives were synthesized by decarboxylative Mannich reaction of chiral N-tert-butanesulfinyl imines with β-keto acids, and were subsequently transformed into cis-2,6-disubstituted piperidin-4-ones through an organocatalyzed condensation with aldehydes. Both enantiomers were accessible from the same precursors by inverting the order in the reaction sequence of the aldehydes involved in the imine formation and the intramolecular Mannich condensation. The synthesis of the piper...

Michael Addition of P-nucleophiles to Conjugated Nitrosoalkenes.

A general approach to various α-phosphorus-substituted oximes (β-oximinoalkyl-substituted phosphonates, phosphine oxides, phosphine-borane complexes and phosphonium salts) was developed. The strategy exploits hitherto unknown Michael addition of PH-containing compounds (diphenylphosphine oxide, diisopropyl phosphite, phosphine-borane complexes and triphenylphosphonium bromide) to unstable conjugated nitrosoalkenes, which are generated in situ from corresponding nitrosoacetals. The resulting α-phosphorus-...

Unravelling the Origins of Hydroboration Chemoselectivity Inversion Using an N,O-Chelated Ir(I) Complex: A Computational Study.

It has been widely reported that the transition metal catalysts can invert the chemoselectivity of hydroboration of multifunctional substrates, but the fundamental reasons for this inversion have rarely been studied. In this work, mechanistic details and chemoselectivity of the hydroboration of various E-C ( E = CH, CH, O, N, etc.) multiple bonds has been explored through density functional theory calculations, including reactions using free HBCy or captured HBCy by an N,O-chelated Ir(I) complex which inclu...

The photo-Fries rearrangement of some 3-acyl estrone in homogeneous media. Preparative and mechanistic studies.

Irradiation of a series of 3-acyl estrone under nitrogen atmosphere in cyclohexane, MeCN and MeOH was investigated under steady-state conditions. The molecules underwent the photo-Fries rearrangement, with concomitant homolytic fragmentation of the ester group and [1;3]-acyl migration. This pathway afforded the ortho-acyl estrone derivatives, the main photoproducts together with estrone. During the irradiation of 3-benzoyl estrone, epimerization of estrone through the Norrish Type I reaction occurred, provi...

Pd-Catalyzed C(sp2)-H Imidoylative Annulation: a General Approach to Construct Dibenzoox(di)azepines.

A general method to construct the scaffolds of dibenzooxazepine and dibenzodiazepine, through Pd-catalyzed isocyanide insertion and intramolecular C(sp2)-H activation, has been developed. This is the first example of seven-membered heterocycle formation by C-H imidoylative annulation.

Chemoselective Trifluoroethylation Reactions of Quinazolinones and Identification of Photostability.

Herein, we report chemoselective trifluoroethylation routes of unmasked 2-arylquinazolin-4(3 H)-ones using mesityl(2,2,2-trifluoroethyl)iodonium triflate at room temperature. Homologous C-, O-, and N-functionalized subclasses are accessed in a straightforward manner with a wide substrate scope. These chemoselective branching events are driven by Pd-catalyzed ortho-selective C-H activation at the pendant aryl ring and base-promoted reactivity modulation of the amide group, leveraging the intrinsic directing ...

Catalytic Staudinger Reduction at Room Temperature.

We report an efficient catalytic Staudinger reduction at room temperature that enables the preparation of a structurally diverse set of amines from azides in excellent yields. The reaction is based on the use of catalytic amounts of triphenylphosphine as a phosphine source, and diphenyldisiloxane as a reducing agent. Our catalytic Staudinger reduction exhibits a high chemoselectivity, as exemplified by reduction azides over other common functionalities, including nitriles, alkenes, alkynes, esters, and keto...

Halogen Bond-Assisted Electron-Catalyzed Atom Economic Iodination of Heteroarenes at Room Temperature.

A halogen bond-assisted electron-catalyzed iodination of heteroarenes has been developed for the first time under atom economic conditions at room temperature. The iodination is successful with just 0.55 equivalent of iodine and 0.50 equivalent of peroxide. The kinetic study indicates that the reaction is elusive in absence of halogen bond between the substrate and iodine. The formation of halogen bond, its importance in lowering the activation barrier for this reaction, the presence of radical intermediate...


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