Dual copper catalysis, involving two different reactions, click (alkyne-azide) and carbon-oxygen bond formation (aryl iodide-secondary alcohol) in a single step, is reported. Synthesis of novel ...benzodioxines (benzodioxanes), benzoxazines, benzoxathiines and benzodioxepines, which feature benzo-condensed six or seven membered rings containing two hetero-atoms attached to a 1,2,3-triazole, is described. As an extension, such compounds were also synthesised by ring opening of epoxide and cyclisation using Cu(I). All the key products have been characterized by single crystal X-ray crystallography.
A sequential copper‐catalyzed, one‐pot, click reaction–intramolecular direct arylation, which involves two mechanistically distinct reactions (atom‐economical click reaction and direct arylation of ...1,2,3‐triazole), to generate 6,6‐, 6,7‐, 6,8‐, and 6,9ring‐fused triazoles is reported. Furthermore, a unique divergence of reactivity between the fused triazoles prepared from 2‐bromobenzyl azide and 2‐bromophenylazide that leads to a fused pentacyclic heterocycle for the former and a C–C‐coupled, biphenyl‐fused, tricyclic product for the latter is observed under Pd catalysis. All of the key products have been characterized by single‐crystal X‐ray crystallography.
The sequential copper‐catalyzed synthesis of heterocycles with 6,6, 6,7, 6,8, and 6,9ring‐fused triazoles and the palladium‐catalyzed synthesis of pentacyclic derivatives are explored.
Abstract
The RGO-Y
2
O
3
and RGO-Y
2
O
3
: Cr
3+
(5 mol %) nanocomposite (NC) synthesized by hydrothermal technique. The structure and morphology of the synthesized NCs were characterized by X-ray ...diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Y
2
O
3
:Cr
3+
displays spherical-shaped particles. Conversely, the surface of the RGO displays a wrinkly texture connecting with the existence of flexible and ultrathin graphene sheets. The photoluminescence (PL) emission spectra showed series of sharp peaks at 490, 591, and 687 nm which corresponding to
4
F
9/2
→
6
H
15/2
,
4
F
9/2
→
6
H
13/2,
and
4
F
9/2
→
6
H
11/2
transitions and lies in the blue, orange, and red region. The prepared NCs were used for the preparation of modified carbon paste electrodes (MCPE) in the electrochemical detection of dopamine (DA) at pH 7.4. Both modified electrodes provide a good current response towards voltammetric detection of DA. Doping is an effective method to improve the conductivity of Y
2
O
3
:Cr
3+
and developed a method for the sensor used in analytical applications.
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•Electropolymerization of direct yellow 11 was achieved.•Surface characterised by TEM and FESEM for modified electrode.•Simultaneous determination of catechol and hydroquinone in ...presence of resorcinol.•Good sensitivity, selectivity and low detection limits.•Analytical application of poly (direct yellow 11)/MPGE was determined.
Present study describes the fabrication of new electrochemical sensor by electropolymerization of direct yellow 11 on the surface of pencil graphite electrode (PGE) for the investigation of catechol (CC) and hydroquinone (HQ) in the presence of resorcinol (RS). The modified electrode surface was further characterized by Transmission electron microscopy (TEM) and Field Emission Scanning Electron Microscope (FESEM). After the modification of PGE, it exhibits an excellent electrochemical response for the analytes using cyclic voltammetry (CV) and differential pulse voltammetric (DPV) technique. Specific parameters including varying concentration of analytes, sweep rate and pH solution were optimized to the electrode. The kinetic property of a modified electrode was got to be both adsorption and diffusion controlled and it give lower detection limit for CC (0.11 µM) and HQ (0.16 µM) respectively. In the simultaneous electroanalysis, bare PGE was failed to depict the oxidation peaks, whereas modified electrode gives well separated three anodic peaks for CC, HQ and RS with superior enhancement in peak current. The proposed modified electrode was applied for the quantification of CC, HQ and RS in a tap water and obtained a consistent recovery in-between 96 and 100 %. The proposed sensor can be fabricated using a simple method with a low cost.
A new route for 2,5-dimethylenetetrahydrofurans, 2-substituted furans and a β,ω-diketophosphonate has been uncovered by a Zn(OTf)2 catalyzed reaction of allenylphosphine oxides/allenylphosphonate ...with propargyl acohol.
A novel synthesis of 2,5-dimethylenetetrahydrofurans, 2-substituted furans and a β,ω-diketophosphonate in good to excellent yields has been achieved by the reaction of allenylphosphine oxides/allenylphosphonate with propargyl alcohol using zinc triflate/triethylamine combination.
In the present work, exfoliated graphite oxide (E-GO) was prepared by sonicating graphite oxide (GO) (prepared by modified Hummer's and Offemam methods). Prepared GO and E-GO were characterized using ...infrared absorption spectroscopy, X-ray diffraction, and scanning electron microscopy. The electrocatalytic properties of GO and E-GO towards detection of dopamine (DA), uric acid (UA), and folic acid (FA) were investigated using cyclic voltammetry and differential pulse voltammetry. Our results revealed that E-GO has a slighter advantage over the GO as an electrode modifier for detection DA, UA, and FA, which might be ascribed to the good conductivity of E-GO when compared to the GO.
Abstract
In this present study, coomassie brilliant blue G-250 (CBBG) modified electrode was fabricated for the specific and simultaneous detection of three dihydroxybenzene isomers such as ...resorcinol (RS), catechol (CC) and hydroquinone (HQ). The fabrication of the modified electrode was carried out by electrochemical polymerization of CBBG on the surface of unmodified electrode. The surface structures of bare and fabricated electrode were studied by scanning electron microscope (SEM). The established electrode portrays the very fine interface with these isomers and displayed the sufficient sensitivity and selectivity. The specific parameters of pH solution, scan rate and varying the concentration of analytes were optimized at the modified electrode. The sensor process was originated to be adsorption-controlled activity and the low limit of detection (LOD) for RS and CC was attained at 0.24 and 0.21 µM respectively. In the simultaneous study, designed sensor clearly implies the three well separated anodic peaks for RS, HQ and CC nevertheless in unmodified electrode it failed. Also, the constructed electrode was applied for the real sample analysis in tap water and obtained results are agreeable and it consistent in-between 92.80–99.48%.
An effective, recoverable, dinuclear palladium(I) catalyst (OCH2CMe2CH2O)PSPd(PPh3)2 has been explored and compared with other traditional palladium catalysts (e.g., Pd(PPh3)4) in the ...phosphonylation/phosphanylation ofallenes (OCH2CMe2CH2O)P(O)CH=C=CH2 (1), Ph2P(O)CH=C=CH2 (2), (EtO)2P(O)CH=C=CH2 (3) (OCH2CMe2CH2O)P(O)CH=C=CMe2 (4), Ph2P(O)CH=C=CMe2 (5), (OCH2CMe2CH2O)P(O)C(Ph)=C=CH2 (6) and Ph2P(O)C(Ph)=C=CH2 (7). The phosphonylation/phosphanylation, in general, occurred at the carbon β to the phosphorus atom, but the concomitant proton addition took place at the α or γ positions leading to either allyl‐ or vinyl‐phosphonates. The use of P(nBu)3 as catalyst led to geminal and bis‐phosphonylation/phosphanylation with less substituted =CH2 terminal allenes 1 and 2. In conjunction with the use of the corresponding isomeric alkynes 8 and 9, as many as five different types of phosphonylated products have been synthesized. The reactions with the more substituted allenes 4–7 gave single products in most cases. Several examples of catalyst‐free, solvent‐free phosphanylation reactions are also described. The reactivity of the phosphonylating/phosphanylating agents was found to be (OCH2CMe2CH2O)P(O)H (10) < (OCH2CMe2CH2O)P(S)H (11) < Ph2P(O)H (12) ≈ Ph2P(S)H (13). The catalytic activity of the recoverable dinuclear palladium(I) complex (OCH2CMe2CH2O)PSPd(PPh3)2 (14), which poses interesting questions about the mechanistic pathway, is briefly highlighted. Structures of the dinuclear palladium(I) catalyst 14 and the key products were determined by X‐ray crystallography.
The addition of P(X)–H (X = O, S) to allenes and alkynes has been achieved under palladium‐catalysed, phosphane‐catalysed and non‐catalytic conditions depending upon the phosphonylating/phosphanylating agent.
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