Reaction Of Bromide Research Articles

A fluorine and chlorine substituted 2D lead bromide perovskite with high phase transition temperature

Two-dimensional (2D) organic-inorganic hybrid perovskite (OIHP) has the advantages of excellent material stability, structural diversity and ease of manufacturability. It is worth noting that the fluorination strategy has been recognized as a convenient molecular design method that can effectively customize and optimize physical and chemical properties in 2D OIHP materials. However, selection the fluorine-chlorine double substituted organic amine to construct lead halide OIHP molecules was not reported. Here, for the first time, we successfully obtained a 2D metal halide perovskite compound [4-Cl-2-FBA]2PbBr4 (1) by reactions of lead bromide with two equivalents of 4-chloro-2-fluorobenzylamine [4-Cl-2-FBA] in concentrated HBr aqueous solution. Its crystal structure and purity were confirmed by X-ray single crystal diffraction and powder X-ray diffraction (PXRD). Differential scanning calorimetry (DSC) and dielectric measurement analyses showed the phase transition (PT) temperature of 1 is 380.1 ​K which is higher than that of [2-FBA]2PbBr4, (2-FBA ​= ​2-fluorobenzylammonium, 364 ​K), but lower than those of (benzylammonium)2PbBr4 (405 ​K) and [PFBA]2PbBr4 (PFBA ​= ​perfluorobenzylammonium, 440 ​K).

Supported Palladium-Catalyzed Carbonylative Synthesis of Diaryl Ketones from Aryl Bromides and Arylboronic Acids.

A palladium supported on graphitic carbon nitride (Pd/g-C3 N4 ) catalyzed carbonylative reaction of aryl bromides and arylboronic acids by has been developed for the construction of diaryl ketones. Using benzene-1,3,5-triyl triformate (TFBen) as the CO source, the reaction proceeded well to give various diaryl ketones in moderate to good yields.

DFT Mechanistic Study of IrIII/NiII-Metallaphotoredox-Catalyzed Difluoromethylation of Aryl Bromides.

The work by MacMillan et al. ( Angew. Chem., Int. Ed. 2018, 57, 12543-12548) developed an IrIII/NiII-metallaphotoredox-catalyzed difluoromethylation strategy of aryl bromides using CHF2Br as the CHF2 reagent in the presence of tris(trimethylsilyl)silane. Here, we present a density functional theory (DFT)-based computational study to understand special dual catalysis promoting the C(sp2)-C(sp3) coupling. The calculated results show that the energetically more favorable pathway involves the reductive quenching of a photocatalyst (IrIII/*IrIII/IrII/IrIII) and a Ni0-initiated catalytic cycle (Ni0/NiI/NiIII/NiI/Ni0 or Ni0/NiII/NiIII/NiI/Ni0). The calculations reveal not only the mechanistic details delivering the difluoromethylarene product but also the molecular-level picture of the generation of Ni0 species from the NiII precatalyst. Moreover, the calculations also rationalize the observed stoichiometric effect of CHF2Br in the reactions of aryl bromides with different substituted groups.

Fabricating efficient and stable quasi-3D and 3D/2D perovskite solar cells with 2D-sheets connected by inorganic type ionic-bond

In this work, we report a novel two-dimensional (2D) (SrBr)2PbI4 perovskite layered architecture, which were formed by the reaction of strontium bromide (SrBr2), strontium iodide (SrI2) and lead iodide (PbI2). Formation of 2D (SrBr)2PbI4 was verified by small angle XRD peak at 6.4°, which corresponds to the layer distance of 13.78 Å. The best one of solar cells fabricated with Quasi-3D perovskite, (SrBr)2FA59Pb60I181 (n = 60), showed a power conversion efficiency (PCE) of 18.46% and retained 95% of the initial PCE at 1000 h in the dry air. Further, the 2D (SrBr)2PbI4 as the surface passivation layer on the 3D FAPbI3 perovskite greatly reduced the defects at the perovskite/Spiro-OMeTAD interface, and the corresponding solar cells with FAPbI3/(SrBr)2PbI4 3D/2D structure achieved a PCE of 22.14% and over 90% retention of the original PCE at 1000 h. In short, this work provides an example of inorganic complex cations that can form 2D perovskites and achieve perovskite solar cells with high PCE and stabilization at the same time.

Enantioselective Total Syntheses of Manginoids A and C and Guignardones A and C

AbstractAn enantioselective synthetic approach for preparing manginoids and guignardones, two types of biogenetically related meroterpenoids, is reported. This bioinspired and divergent synthesis employs an oxidative 1,3‐dicarbonyl radical‐initiated cyclization and cyclodehydration of the common precursor to forge the central ring of the manginoids and guignardones, respectively, at a late stage. Key synthetic steps include silica‐gel‐promoted semipinacol rearrangement to form the 6‐oxabicyclo[3.2.1]octane skeleton and the Suzuki–Miyaura reaction of vinyl bromide to achieve fragment coupling. This synthesis protocol enables the asymmetric syntheses of four fungal meroterpenoids from commercially available materials.

Enantioselective Total Syntheses of Manginoids A and C and Guignardones A and C.

An enantioselective synthetic approach for preparing manginoids and guignardones, two types of biogenetically related meroterpenoids, is reported. This bioinspired and divergent synthesis employs an oxidative 1,3-dicarbonyl radical-initiated cyclization and cyclodehydration of the common precursor to forge the central ring of the manginoids and guignardones, respectively, at a late stage. Key synthetic steps include silica-gel-promoted semipinacol rearrangement to form the 6-oxabicyclo[3.2.1]octane skeleton and the Suzuki-Miyaura reaction of vinyl bromide to achieve fragment coupling. This synthesis protocol enables the asymmetric syntheses of four fungal meroterpenoids from commercially available materials.

Visible-Light-Driven, Palladium-Catalyzed Heck Reaction of Internal Vinyl Bromides with Styrenes.

Functionalized 1,3-dienes were efficiently accessed from visible-light-driven, palladium-catalyzed Heck reaction of S,S-functionalized internal vinyl bromides with styrenes under mild conditions. This Heck reaction showcased tolerance of a wide array of functional groups, afforded the target products in moderate to excellent yields through a radical reaction pathway. The resultant diene products could be further transformed to highly functionalized trisubstituted furan derivatives.

Half-sandwich complexes of group 9 metals with N,Nʹ-ligands for CF3-carbenoid alkylation of N-(pyrimidin-2-yl)indole

The complexes [CpM(N,Nʹ-ligand)Br]PF6 (M = Rh, Ir; N,Nʹ-ligand = 2,2′-bipyridyl, 1,10-phenanthroline) were synthesized by reactions of bromides [CpMBr2]n with 2,2′-bipyridyl or 1,10-phenanthroline followed by a counterion exchange. The replacement of cyclooctadiene in [CpIr(cod)I]I3 with N,Nʹ-ligands leads to complexes [CpIr(N,Nʹ-ligand)I]I3 (N,Nʹ-ligand = 2,2′-bipyridyl, 1,10-phenanthroline). The structures of [CpRh(2,2′-bipyridyl)Br]PF6, [CpIr(2,2′-bipyridyl)I]I3, and [CpIr(1,10-phenanthroline)Br]PF6 were determined by X-ray diffraction. The compounds prepared as well as the related the tris(pyrazolyl)borate derivatives [CpCoTp]PF6 and [Cp*MTp]PF6 (M = Rh, Ir) efficiently catalyze the alkylation of N-(pyrimidin-2-yl)indole with methyl 3,3,3-trifluoro-2-diazopropionate to selectively introduce the CF3 and carboxylate functions at the C3 position of the indole moiety. In contrast, the tris(pyrazolyl)borate cobalt complex [Cp*CoTp]PF6 predominantly provides the alkylation at the C2 position.

A magnetically retrievable mixed-valent Fe3O4@SiO2/Pd0/PdII nanocomposite exhibiting facile tandem Suzuki coupling/transfer hydrogenation reaction

Herein, we report a magnetically retrievable mixed-valent Fe3O4@SiO2/Pd0/PdIINP (5) nanocomposite system for tandem Suzuki coupling/transfer hydrogenation reaction. The nanocomposite 5 was prepared first by making a layer of hbox {SiO}_{2} on hbox {Fe}_{3}hbox {O}_{4}hbox {NP} followed by deposition of hbox {Pd}^{0} and sorption of hbox {Pd}^{mathrm{II}} ions successively onto the surface of Fe3O4@SiO2NP. The nanocomposite was characterized by powder XRD, electron microscopy (SEM-EDS and TEM-EDS) and XPS spectroscopy techniques. The mixed-valent hbox {Pd}^{0}/hbox {Pd}^{mathrm{II}} present onto the surface of nanocomposite 5 was confirmed by XPS technique. Interestingly, the mixed-valent nanocomposite Fe3O4@SiO2/Pd0/PdIINP (5) exhibited tandem Suzuki coupling/transfer hydrogenation reaction during the reaction of aryl bromide with aryl boronic acid (90% of C). The nanocomposite 5 displayed much better reactivity as compared to the monovalent Fe3O4@SiO2/Pd0NP (3) (25% of C) and Fe3O4@SiO2/PdIINP (4) (15% of C) nanocomposites. Further, because of the presence of magnetic hbox {Fe}_{3}hbox {O}_{4}, the nanocomposite displayed its facile separation from the reaction mixture and reused at least for five catalytic cycles.

Nickel(II) complexes with N,O‐donor thiopseudourea ligands: Syntheses, structures, and catalytic applications in Kumada–Corriu cross‐coupling reactions

Synthesis, characterization, and physical properties of benzyl‐N′‐(4‐R‐benzoyl)‐N‐(2,6‐diisopropylphenyl)carbamimidothioates, HL1 (R = H) and HL2 (R = Cl), and their nickel(II) complexes having the general molecular formula [Ni(L1/2)2] (1 and 2) have been reported. Elemental analysis, magnetic susceptibility, solution electrical conductivity, and various spectroscopic (IR, UV–Vis, and 1H NMR) measurements were used to characterize HL1, HL2, and the two complexes (1 and 2). The molecular structures of all four compounds were determined by single‐crystal X‐ray crystallographic studies. The structures of HL1 and HL2 showed the imino‐ketone form of both compounds. In each of 1 and 2, the six‐membered chelate ring forming iminolate‐O and azomethine‐N donor two (L1/2)− ligands form a square‐planar trans‐N2O2 coordination environment around the metal center. The spectroscopic characteristics of HL1, HL2, 1, and 2 are consistent with their molecular structures. Both complexes were successfully employed as efficient catalysts in Kumada–Corriu CC cross‐coupling reactions of aryl bromides with phenylmagnesium bromide. The reactions provided biaryl products in good to excellent yields with a good substrate scope.

Synthesis, characterization and catalytic activity of N-heterocyclic carbene ligated Schiff base palladacycles

A series of N-heterocyclic carbene (NHC) ligated Schiff base palladacycles were synthesized by the reaction of μ-acetato-bridged Schiff base palladacycles (PdL1-2) with imidazolium salts (a-c). The new NHC ligated palladacycles were fully characterized using 1H NMR, 13C NMR, infrared spectroscopy, MS analysis, and single-crystal X-ray diffraction for one complex (PdL1). Further exploration of the catalytic application of the palladacycles for Suzuki-Miyaura cross-coupling reactions of aryl bromides with phenylboronic acid was carried out. It was determined that the new dimeric imine-palladacycle (PdL2) exhibits the highest catalytic activity among the coupling compounds in this study.

Ultrasound-Assisted Synthesis, Antioxidant Activity and Computational Study of 1,3,4-Oxadiazol-2-amines

Development of synthetic procedures for the preparation of 1,3,4-oxadiazole derivatives has always been in the interest of researchers as a result of their widespread biological activities. In this study, an ultrasound-assisted procedure was proposed for the synthesis of 1,3,4-oxadiazol-2-amines form the reaction of hydrazides and cyanogen bromide. They were efficiently produced in 81-93% yields in the presence of ethanol and potassium bicarbonate as the reaction media and the base, respectively. Their antioxidant properties were determined via DPPH free radical scavenging method as one of the most basic steps in identifying other related biological effects. IC50 values were in the range of from 0.237 to 0.863 mM. The synthesized 1,3,4-oxadiazoles are protective agents against oxidative stress, and can be used in the treatment of cancer, candidiasis, diabetes, neurodegenerative and inflammatory diseases. Furthermore, bond dissociation energies (BDEs) and electron densities based NCI (non-covalent interactions) were calculated using density-functional theory (DFT) to understand the observed reactivities. It was found that reversible dipole-dipole forces play a key role in most interactions.

Synthesis, Spectroscopic Characterization, and Biological Activities of New Binuclear Co(II), Ni(II), Cu(II), and Zn(II) Diimine Complexes

Metal-ligand complexes have attracted major interest due to their potential medical applications as anticancer agents. The work described in the current article aimed to synthesize, spectroscopic, thermal, and biological studies of some metal-diimine complexes. A diimine ligand, namely 2-{[2-(4-chlorophenyl)-2-hydroxyvinyl]-hydrazonomethyl}phenol (diim) was prepared via the reaction of p-chlorophenacyl bromide with hydrazine hydrate in ethanol, then condensation was completed with 2-hydroxybenzaldehyde in acetic acid. The Co(II), Ni(II), Cu(II), and Zn(II) complexes were prepared with a metal:ligand stoichiometric ratio of (2:1). 1H-NMR, UV-Vis, FTIR spectroscopic data, molar conductivity measurements, and microanalytical data (carbon, hydrogen, nitrogen, and halogen) were used for characterization of the formed ligand and its metal complexes. It was found that the diimine ligand act as tetradentate fashion. The non-electrolytic character for all the complexes was proved by molar conductivity. The first metal atom of the synthesized binuclear diimine complexes coordinates with the nitrogen of hydrazine group and oxygen of OH group. While, the second metal atom coordinates with the other nitrogen atom of the hydrazine group and oxygen of phenolic group. All the synthesized metal complexes have a six-coordinated except for Zn(II) has four-coordinated. Thermogravimetric analysis and its differential analysis were done to discuss the thermal degradation of the free ligand and its metal complexes. Molecular docking calculation showed that the diimine ligand is a good inhibitor for breast cancer 3hb5 and 4o1v kidney cancer proteins. Additionally, these compounds were evaluated as antibacterial and antifungal agents.

A new PEPPSI type N-heterocyclic carbene palladium(II) complexes and its efficiency as a catalyst for Mizoroki-Heck cross-coupling reactions in water : Synthesis, Characterization and their antimicrobial and Cytotoxic activities

A series of novel benzimidazolium salts 2 and their new air and moisture stable PEPPSI type N-heterocyclic carbene palladium(II) complexes (PEPPSI: pyridine-enhanced pre-catalyst preparation, stabilisation, and initiation), were synthesized and characterized by means of 1H and 13C{1H} NMR, FTIR spectroscopic methods and elemental analysis was employed to catalyze the Mizoroki-Heck cross-coupling reactions of aryl bromides with styrene in water. To the best of our knowledge, this is the first report where a Pd-PEPPSI catalyst was successfully employed in aqueous-phase Mizoroki-Heck reaction. Good to excellent yields of cross-coupling products were obtained with a range of representative aryl bromides under relatively mild conditions. Moreever the antimicrobial activity of the PEPPSI type N-heterocyclic carbene palladium(II) complexes 3a-e varies with the nature of the ligands. Also, the IC50 values of both, complexes (3a-e) have been determined. In addition, the new PEPPSI type N-heterocyclic carbene palladium(II) complexes were screened for their cytotoxic activities. Complex 3b exhibited the highest antitumor effect with IC50 values 0.63 μg/mL and against MCF-7.

Reinvestigation of tandem dimerization and 1,3-alkyl shift in 3-benzylbenzothiazolylidene carbene: Experimental and theoretical results

The reaction of 3-benzylbenzothiazolium bromide with triethylamine generates initially two products as revealed by the TLC. However, on purification, only one compound is obtained, which is the same compound as reported by Baldwin and co-worker. A theoretical investigation at the B3LYP/6–31+G(d) level could identify two possible routes involving successive dimerization and 1,3-benzyl shift of the N-heterocyclic carbene, namely 3-benzylbenzothiazolylidene leading to two isomeric products. The second step is found to be the rate-determining step. The activation free energy barriers of both steps for the isomer actually obtained are comparatively lower than for the other product. Furthermore, the two isomers are found to be atropisomers separated by a small activation free energy barrier which is insufficient to keep the identities of the two isomers intact, with the result that the less stable atropisomer changes into the more stable one. Thus it has been possible to rationalize the experimental results by the theoretical investigation.

Diastereoselective Construction of Eight-Membered Carbocycles through Palladium-Catalyzed C(sp3)-H Functionalization.

A palladium-catalyzed cross-coupling reaction of 2-alkylphenyl bromides with biphenylene has been developed. The reactions formed eight-membered carbocycles through C(sp3)-H activation and the formation of two C-C bonds, and the chiral products were obtained with excellent diastereoselectivity. The reaction provides a new strategy for the construction of eight-membered carbocycles, and the products represent a novel type of chiral scaffold.

Synthesis of β-keto-sulfones using alkyl/aryl sulphinates in ionic liquids [bmim-BF4] as an efficient and reusable reaction medium

Synthesis of β-keto-sulfones using alkyl/aryl sulphinates in ionic liquids [bmim-BF4] as an efficient and reusable reaction medium

Difluoromethylation of Alkyl Bromides and Iodides with TMSCF2H.

We describe, for the first time, two protocols for direct difluoromethylation of unactivated alkyl bromides and iodides. Reactions of alkyl iodides with TMSCF2H were mediated by a copper catalyst using CsF as the activator, while reactions of less reactive alkyl bromides required a combination of palladium and a stoichiometric amount of CuI as the catalysts. Preliminary mechanistic studies of the synergistic Pd/Cu-catalyzed difluoromethylation of alkyl bromides suggest that it proceeds likely via a Pd(I)/Pd(III) catalytic cycle.

Synthesis of hydrogen-substituted graphdiynes via dehalogenative homocoupling reactions.

A new method is introduced to prepare hydrogen-substituted graphdiynes (HsGDYs) via the dehalogenative homocoupling of terminal alkynyl bromides. Compared with previous synthetic strategies, the reaction conditions are moderate and the time is shortened. HsGDYs exhibit porous structures and hydrogen/oxygen evolution reaction (HER/OER) catalytic activity, endowing applications in electrochemical catalysis.

Mechanochemical synthesis of aromatic sulfonamides.

A three-component Pd-catalysed aminosulfonylation reaction of K2S2O5 and amine with aryl bromides or aromatic carboxylic acids was developed. This strategy was developed to utilise mechanical energy and accommodate primary as well as secondary aliphatic and aromatic amines to provide a new shortcut to a wide range of sulfonamides. Studies on the scope and limitations of the reaction indicated its tolerance of a vast range of functional groups and many structural patterns. The reactions were scaled up to gram quantities.