Presence Of Aryl Research Articles

Palladium-Catalyzed Thiocarbonylation of Aryl Iodides Using CO2.

The first example of catalytic thiocarbonylation of aryl iodides using CO2 has been achieved employing a combination of PdCl2 and carbazole-derived phosphine ligands. Under mild conditions, a broad scope of aryl iodides were converted to the desired thioester products in the presence of aryl or alkyl thiols (33 examples, up to 96% yields). The choice of metal, ligands, and reductant were crucial for high efficiency and chemoselectivity. Moreover, this strategy provided an effective method for the late-stage functionalization of biorelevant molecules.

Photoredox Catalyzed Trifluoromethyl Radical‐Triggered Trifunctionalization of 5‐HexenenitrilesviaCyano Migration

AbstractA photoredox catalyzed trifluoromethyl radical‐triggered trifunctionalization of 5‐hexenenitrilesviacyano group migration is reported. The cyano group migration is of high chemo‐selectivity even in the presence of aryl or heteroaryl groups as competitors. This protocol provides a facile access to a broad scope of CF3‐containing compounds with high molecular complexity and functional group diversity. The success of gram‐scale reaction and the versatility of products in derivative synthesis illustrate the potential value of this transformation in synthetic chemistry.magnified image

Synthesis of amphiphilic asymmetrical dithienylethenes with aryl groups at the reactive carbons

A synthetic route for the preparation of amphiphilic asymmetrical dithienylethenes that incorporate methyl groups at the 4- and 4′-positions and an aryl group at one of the reactive carbons has been developed. The presence of a bulky aryl substituent ensures a relatively large change in molecular geometry upon photoisomerization, whereas the presence of methyl groups provide enhanced photostability. Notably, a substituent effect was systematically revealed en route to the preparation of the dithienylethene precursors. In particular, this formal substitution reaction was significantly inhibited due to steric hindrance, stemming from the presence of aryl and methyl groups at the alpha positions of the preformed thienyl carbanionic carbon, and an aryl group on the monosubstituted perfluorocyclopentene derivative.

Effect of Trichoderma spp. on the Propagation of Maytenus ilicifolia Mart. ex Reissek

The interest in using biotechnology tools that contribute to reducing the need for chemical inputs in agroforestry production has increased in recent years, aiming at higher quality for the environment and for society. This interest is also applied to medicine species consumed in natura. The objective of this study was to evaluate the effect of Trichoderma spp. on germination and initial growth of Maytenus ilicifolia seedlings. Laboratory and greenhouse tests were carried out using Trichoderma spp. isolates obtained from three different strains identified as Trichoderma asperelloides (T1 & T2 strains) and Trichoderma virens (T10 strain). In laboratory, M. ilicifolia seeds without aryl were inoculated in solutions containing fungal spores and distributed in substrate paper in four replicates of 25 seeds/treatment. The first germination count, accumulated germination, percentages of accumulated dead seeds and firm seeds were evaluated at 7, 14, 21 and 28 days of incubation. The same isolates were used to evaluate the effect on the initial growth of seedling in a greenhouse through a completely randomized design with 40 replicates, considering a seedling as each replicate. Trichoderma spp. isolates were inoculated on the substrate used as the basis for seeding. Seeds of M. ilicifolia were used from the same batch of the laboratory test, but without removing the aryl. The variables of total height, diameter at root collar and number of leaves were evaluated at 90, 120, 150 and 180 days after seeding. A positive effect of Trichoderma inoculation on seed germination and vigor was observed in the laboratory, with emphasis on the T2 isolate. Growth promoting effects on the M. ilicifolia seedlings were not observed in greenhouse. We suggest to better investigate the interaction between the tested Trichoderma isolates and M. ilicifolia seeds in the presence of aryl.

Editorial

Editorial

Synthesis of N‐alkyl‐N′‐aryl or Alkenylpiperazines: A Copper‐Catalyzed C–N Cross‐Coupling in the Presence of Aryl and Alkenyl Triflates and DABCO

Unsymmetrical piperazines are key constituents of many pharmaceuticals. Given that the selective introduction of an aryl and alkyl motif onto the piperazine is not always straightforward, direct arylation and alkenylation of 1,4‐diaza‐bicyclo[2.2.2]octane would obviate the inefficiencies associated with the preparation of these target molecules. We have utilized alkyl halides, aryl or alkenyl triflates, and 1,4‐diaza‐bicyclo[2.2.2]octane for the synthesis of N‐alkyl‐N′‐aryl or alkenylpiperazines. The optimum conditions are developed using CuCl, t‐BuOLi in NMP. Alkenyl triflates requires N,N′‐dimethylethylenediamine and higher temperature to afford the desired cross‐coupled product. Substrates bearing electron‐deficient and electron‐rich groups were successfully coupled under the optimum reaction conditions.

Efficient synthesis of fluoroalkylated 1,4,2-oxathiazoles via regioselective [3 + 2]-cycloaddition of fluorinated nitrile oxides with thioketones

Fluorinated acetonitrile oxides, generated from the corresponding hydroximoyl bromides in the presence of aryl, hetaryl, ferrocenyl, and cycloaliphatic thioketones, undergo efficient [3+2]-cycloadditions to give 3-fluoroalkylated 1,4,2-oxathiazoles in good to excellent yields. The reactions proceed regioselectively with no competitive formation of furoxans as dimers of the intermediate 1,3-dipoles.

Ring Expansion/Homologation−Aldehyde Condensation Cascade Using tert-Trihalomethylcarbinols

Treatment of cyclic tert-trihalomethylcarbinols with CrCl(2) in THF/HMPA in the presence of aryl or aliphatic aldehydes initiates a cascade sequence of one carbon ring expansion-olefination affording conjugated exocyclic ketones. Acyclic tert-trihalomethylcarbinols undergo a comparable cascade of one carbon homologation-olefination.

A Simple and Useful Synthetic Protocol for Selective Deprotection of tert‐Butyldimethylsilyl (TBS) Ethers

AbstractA wide variety of tert‐butyldimethylsilyl ethers 1 can be easily cleaved to the corresponding parent hydroxyl compound 2 in the presence of 5 mol % of acetonyltriphenylphosphonium bromide (ATPB) at room temperature. In addition, tert‐butyldiphenylsilyl ethers can also be cleaved by using 20 mol % of the same catalyst. Alkyl tert‐butyldimethylsilyl ethers can be deprotected to the hydroxyl compounds chemoselectively in the presence of aryl tert‐butyldimethylsilyl ethers. Some of the major advantages are mild reaction conditions, no aqueous workup, high efficiency and chemoselectivity and compatibility with other protecting groups; no brominations occur in the aromatic ring under these experimental conditions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Palladium(0)-catalyzed Ring Expansion Reactions of Hydroxy Methoxyallenylisoindolinones via Inter- and Intramolecular Carbopalladation Using Aryl and Vinyl Halides

Palladium(0)-catalyzed one-atom ring expansion of various hydroxy methoxyallenylisoindolinones 2 proceeded in the presence of aryl and vinyl halides to give the corresponding isoquinolinediones 3 in various yields. Tandem intramolecular carbopalladation-heterocyclic ring expansion reaction of compound 5 was also achieved to give a tetracyclic compound 6.

Crystal engineering of neutral N-arylpyrimidinones and their HCl and HNO3 adducts with a C–H⋯O supramolecular synthon. Implications for non-linear optics

In a previous crystallographic study of some N-arylpyrimidinones 1, we noted that: (1) C–H⋯O hydrogen bonds connect molecules in a linear array; (2) the charge transfer axis of the chromophore is aligned with the main symmetry operator of point groups 2 or m at ca. 57°, a value that is close to the ideal angle of 54.74°; (3) the methyl and chloro derivatives are isostructural. In this paper, we report the characterisation of chloride and nitrate salt adducts of 1 by X-ray diffraction and the analysis of their packing motifs. Recurrence of the same C–H⋯O supramolecular synthon in three neutral and five HCl and HNO3 adducts of 1 signifies the robustness of this weak hydrogen bond. The occurrence of a mirror plane m in a family of eight crystal structures (four Pnma, two P21/m, one Pbcm, and one Pmn21) is unusual because this symmetry operation is generally avoided due to close packing considerations. Ab initio calculations show that the bisected phenyl conformation present in these crystal structures is the most stable conformation of the pyrimidinone molecule. The presence of aryl and pyrimidinone chromophores in 1, the correct alignment of the aromatic ring in the crystal and the occurrence of 2D polar layers in some crystal structures are favourable factors for non-linear optical applications. However, a strategy for the crystallisation of these achiral molecules in non-centrosymmetric space groups is yet to be achieved. This crystal engineering study simplifies the challenge of complete 3D structural control into a modular 2D+1D problem.

1,2,3,4-Tetrahydro-1-naphthyl ester as a selective protecting group for carboxylic acids

The carboxylic acid functionality can be protected as the 1,2,3,4-tetrahydro-1-naphthyl ester, which can be selectively cleaved in the presence of aryl and alkyl esters using chlorotrimethylsilane and sodium iodide in acetonitrile. This protecting group allows room temperature deprotection under essentially neutral conditions throughout the cleavage reaction.

Regio- and Stereoselective Synthesis of 1,3-Hydroxyl Amines via Palladium-Catalyzed Carbonate-Carbamate Transformation with Unique Stereoselectivity: Synthesis of 3-Amino-4-penten-1-ols

The transformation of cyclic carbonates 1,3-dioxan-2-one derivative (1) to cyclic carbamates 1,3-oxazin-2-one derivative (4) is achieved in the presence of aryl or sulfonyl isocyanate by the catalysis of Pd(0) in high yield and with high structure flexibility. The reaction shows unique stereoselectivity: 3,4-disubstituted carbonates (2), irrespecti- ve of the composition of their stereoisomers, provide trans-(5) carba- mate exclusively or predominantly over cis-5. Mixtures of cis- and trans -3,5-disubstituted carbonates (3) furnish either cis-(6) or trans-(6) carbamate in high selectivity depending on the reaction conditions (kinetic or thermodynamic control, respectively). 1 H NMR and X-ray structure analyses of (5) and (6) indicate that the stereochemical outcome is governed by an A 1,2 -strain between N-sulfonyl and C 5 -vinyl substituents

Branching beta 1-6N-acetylglucosaminetransferases and polylactosamine expression in mouse F9 teratocarcinoma cells and differentiated counterparts.

beta-All-trans-retinoic acid (RA)-induced endodermal differentiation of mouse F9 teratocarcinoma cells is accompanied by changes in glycoprotein glycosylation, including expression of i antigen (i.e. polylactosamine) and leukophytohemagglutinin-reactive oligosaccharides (i.e. -GlcNAc beta 1-6Man alpha 1-6-branched N-linked). We have used the F9 teratocarcinoma cells as a model to study developmental regulation of glycosyltransferase activities which are responsible for the biosynthesis of beta 1-6GlcNAc-branched N- and O-linked oligosaccharides and polylactosamine. Growth of F9 cells in the presence of 10(-6) M RA for 4 days increased core 2 GlcNAc transferase and GlcNAc transferase V activities by 13- and 6-fold, respectively, whereas the activities of GlcNAc transferase I, beta 1-3GlcNAc transferase (i), beta 1-4Gal transferase, and beta 1-3Gal transferase increased 2-4-fold. Induction of glycosyltransferase activities by RA was dose-dependent and showed a biphasic response with approximately half of the increase observed 3 days after RA treatment and the remainder occurred by day 4. PYS-2, a parietal endoderm cell line, showed levels of glycosyltransferase activities similar to those of RA-treated F9 cells. Glycosyltransferase activities in the RA-resistant F9 cell line (RA-3-10) were low and showed only a small induction by RA. These observations suggest that differentiation of F9 cells is closely associated with induction of multiple glycosyltransferase activities, with most pronounced increases in GlcNAc transferase V and 2',5'-tetradenylate (core 2) GlcNAc transferase. The increase in GlcNAc transferase V was also reflected by the 4-6-fold increase in the binding of 125I-leukophytohemagglutinin to several cellular glycoproteins, which occurred after 3 days of RA treatment. The endo-beta-galactosidase-sensitive polylactosamine content of membrane glycoproteins and, in particular, the LAMP-1 glycoprotein was markedly increased after RA treatment of F9 cells. Consistent with these observations, fucosylated polylactosamine (i.e. dimeric Lex) was also increased in RA-treated cells. Analysis of the aryl oligosaccharides produced by F9 cells cultured in the presence of aryl alpha-D-GalNAc showed that RA treatment enhanced the synthesis of disialyl core 2 O-linked oligosaccharides and increased the polylactosamine content of the aryl oligosaccharides by > 20-fold. The results suggest that differentiation of F9 cells into endoderm is closely associated with increased GlcNAc transferase V and core 2 GlcNAc transferase activities, enzymes which control the level of beta 1-6GlcNAc-branched N- and O-linked oligosaccharides, the preferred substrates for polylactosamine addition.

Reaction of 1,1-disubstituted hydrazines with bromine in the presence of aryl- and heteroarylnitroso compounds in acid media: A general method for the synthesis of 1-aryl(heteroaryl)-3,3-disubstituted triazene 1-oxides

We have worked out a method for the synthesis of 1,3,3-trisubstituted triazene 1-oxides based upon reaction of 1,1-disubstituted hydrazines with bromine in the presence of aryl- and heteroarylnitroso compounds in acid media. Obtained are a broad range of triazene 1-oxides, among which hitherto unknown compounds of the series of pyrazole and 3,3-dialkyltriazene 1-oxides that contain functional groups at the alkyl part of the molecule. We propose a reaction scheme which includes in situ formation of diazenium cations and reaction of them with nitroso compounds that are present in the system. By means of PMR,13C, and14N NMR spectroscopy, and mass spectroscopy, it has been shown that in all the prepared compounds the oxidated nitrogen atom is at the N1 position of the triazene N-oxide group.

Structural Analysis of Deuterated and Nondeuterated Frictional Polymers Using Fourier Transform Infrared Spectroscopy and Pyrolysis Gas Chromatography/Mass Spectroscopy

Frictional polymers were produced on oscillating mated Pd/Pd pairs exposed to static air-hydrocarbon vapor environments involving benzene, toluene, cyclohexane, pentane, D6-benzene, and D8-toluene. The structures of these polymer deposits have been examined using the techniques of Fourier transform infrared (IR) spectroscopy and pyrolysis gas chromatograph/mass spectrometer (GC/MS). All polymers were found to be extensively oxygenated, as evidenced by the presence of aryl and unsaturated ester linkages. The structural similarities exhibited by these materials are suggestive of a common mode of formation at the metal surfaces. Discussions of the techniques and results of this study are presented.