Latest ArticlesDipyrrolyldiketone difluoroboron complexes (BONEPYs) were synthesized by condensation of the corresponding pyrroles and malonyl chloride followed by treatment with BF3·OEt2. The aryl-substituted pyrrole is introduced to form a cyclic system in order to investigate anion binding studies. In BONEPYs 1-3 the o-H of the aryl group forms hydrogen bonding with F- to give a more table complex. In contrast, the intramolecular hydrogen-bonded BONEPYendo-4 is more stable than its exo isomer. While adding F-, the hydrogen bonds must be broken first to give 4·(3)F-. Owing to the electron-rich group (-OMe), the o-H of the phenyl group can hardly interact with F- via hydrogen bonding to give the less stable complex 4·(5)F-. The energy differences between the different conformations were calculated using DFT methods, which is consistent to the experimental observations.
The three-component reaction of triphenylphosphine, dimethyl hex-2-en-4-ynedioate and arylidene N, N'-dimethylbarbituric acids in dry methylene dichloride at room temperature afforded trans-1, 3-disubstituted 7, 9-diazaspiro[4.5]dec-1-enes in good yields and with high diastereoselectivity. However, the similar three-component reaction with arylidene Meldrum acids resulted in a mixtures of cis/trans-1, 2-disubstituted 7, 9-dioxaspiro[4.5]dec-1-enes. Additionally, the three-component reaction of triphenylphosphine, dimethyl but-2-ynedioate and arylidene Meldrum acids gave polysubstituted 5-(triphenyl-λ5-phosphanylidene)cyclopenta-1, 3-dienes. A plausible reaction mechanism was proposed for the formation of various products with different regioselectivity and diastereoselectivity.
An efficient gold-catalyzed anti-Markovnikov cycloisomerization-initiated tandem reaction of Bocprotected indole tethered homopropargyl amides has been achieved. This method delivers a wide range of valuable bridged aza-[n.2.1] skeletons (n=3-7) at room temperature with high diastereoselectivity and enantioselectivity by a chirality-transfer strategy. Moreover, the gold-catalyzed tandem reaction of homopropargyl alcohol is also achieved to produce the bridged oxa-[3.2.1] skeleton.
Direct C(sp3)-H functionalization of N-unprotected aliphatic amines represents one of the most efficient and straightforward strategies for amine synthesis. Despite some recent progress in this field, the NH2-directed γ-C(sp3)-H arylation of primary aliphatic amines except α-amino esters remained an unmet challenge. In this report, we established a simple and efficient method for site-selective C(sp3)-H arylation of primary aliphatic amines by aryl iodides. In the presence of only 5 mol% Pd(OAc)2, a wide range of aliphatic amines including O-benzyl and O-silyl amino alcohols were arylated at γ-or δ-positions by aryl iodides containing a broad scope of functional groups. The synthetic application of this method had also been demonstrated by large-scale synthesis, the synthesis of a fingolimod analogue, and the conjugation with natural D-menthol and fluorescent 1, 8-naphthalimide.
We reveal here a visible-light promoted phosphorylation of 2-isocyanoaryl thioethers for the first time with concomitant C(sp3)-S bond cleavage and imidoyl C-S formation. Additionally, this method features the use of 3 mol% organic dye Rose Bengal as the photocatalyst without external transition-metal or peroxide oxidants, and provides a novel and environmentally friendly approach for the preparation of a variety of 2-phosphoryl benzothiazoles in moderate to good yields.
The limited knowledge on low-coordinate zero-valent transition-metal species has intrigued great synthetic efforts in developing ligand sets for their stabilization. While the combined ligand set of N-heterocyclic carbene (NHC) with vinylsilanes was the only known ligand system amenable to the stabilization of three-coordinate formal zero-valent cobalt, iron, and manganese complexes, the exploration on other ligands has proved that the ligand set of NHCs with styrene is equally effective in stabilizing three-coordinate formal zero-valent metal complexes in the form of (NHC)M(η2-CH2CHPh)2 (NHC=IPr, IMes; M=Co, Fe, Mn). These styrene complexes can be prepared by the one-pot reactions of MCl2 with styrene, NHC and KC8, and have been characterized by various spectroscopic methods. Preliminary reactivity study indicated that the interaction of[(IMes)Fe(η2-CH2CHPh)2] with DippN3 produces the iron(Ⅳ) bisimido complex[(IMes)Fe(NDipp)2] and styrene, which hints at the utility of these zero-valent metal styene complexes as synthons of the mono-coordinate species (NHC)M(0).
Palladium-catalyzed highly meta-selective C -H iodination of phenylacetic acid, benzylphosphonate and benzylsulfonate scaffolds with molecular I2 is developed using a pyridine-type template. The practical ester linkages enable the directing template easily installed and readily removed. The substrate scope is broad, and alkyl, methoxyl, trifluomethyl, and halo substituents are compatible with this reaction. Further transformations of ibuprofen iodide intermediates by Pd-catalyzed C -C and C-heteroatom bond formation illustrate the broad utility of this method.
The effective valuation of catalyst supports in the catalytic oxidation makes the contribution to understand the support effect of great interest. Here, the role of active substrate in the performance and stability of Cu-Fe-Co ternary oxides was studied towards the complete catalytic oxidation of CO. The Cu-Fe-Co oxide thin films were deposited on copper grid mesh (CUGM)using one-step pulsed-spray evaporation chemical vapor deposition method. Crystalline structure and morphology analyses revealed nano-crystallite sizes and dome-top-like morphology. Synergistic effects between Cu, Fe and Co, which affect the surface Cu2+, Fe3+, Co3+ and chemisorbed oxygen species (O2- and OH-) of thin films over the active support and thus result in better reducibility. The thin film catalysts supported on CUGM exhibited attractive catalytic activity compared to the ternary oxides supported on inert grid mesh at a high gas hourly space velocity. Moreover, the stability in time-on-stream of the ternary oxides on CUGM was evaluated in the CO oxidation for 30 h. The adopted deposition strategy of ternary oxides on CUGM presents an excessive amount of adsorbed active oxygen species that play an important role in the complete CO oxidation. The catalysts supported on CUGM showed better catalytic conversion than that on inert grid mesh and some literature-reported noble metal oxides as well as transition metal oxides counterparts, revealing the beneficial effect of the CUGM support in the improvement of the catalytic performance.
In this study, two-dimensional V2CTx MXene has been prepared by selectively etching Al layers from V2AlC MAX phase by NaF+HCl etching at 90 ℃ for 72 h and its performance as supercapacitor (SC) electrode were tested using simulating seawater as electrolyte. V2CTx MXene-based electrodes shows a good capacitance of 181.1 F/g, which is in accordance with the volumetric specific capacitance of 317.8 F/cm3, and with 89.1% capacitance retention even after 5000 cycle. Compared with other MXenes, V2CTx have better electrochemical performance as SC electrode. This work provides an innovative strategy to apply V2CTx MXene as SC electrode in safety and effective seawater electrolyte.
MXenes have emerged as versatile 2D materials that are already gaining paramount attention in the areas of energy, catalyst, electromagnetic shielding, and sensors. The unique surface chemistry, graphene-like morphology, high hydrophilicity, metal-like conductivity with redox capability identifies MXenes, as an ideal material for surface-related applications. This short review summarizes the most recent reports that discuss the potential application of MXenes and their hybrids as a transducer material for advanced sensors. Based on the nature of transducing signals, the discussion is categorized into three sections, which include electrochemical (bio) sensors, gas sensors, and finally, electro-chemiluminescence & fluorescent sensors. The review provides a concise summary of all the analytical merits obtained subsequent to the use of MXenes, followed by endeavors that have been made to accentuate the future perspective of MXenes in sensor devices.
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