- Palladium-Catalyzed Ligand-Free C-N Coupling Reactions: Selective Diheteroarylation of Amines with 2-Halobenzimidazoles
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2-Aminobenzimidazoles are widely present in a number of bioactive molecules. Generally, the preparation of these molecules could be realized by the mono-substitution of 2-halobenzimidazoles with amines. However, rare examples were reported for the di-subs
- Sang, Wei,Gavi, Ayao Jean,Yu, Bao-Yi,Cheng, Hua,Yuan, Ye,Wu, Yuan,Lommens, Petra,Chen, Cheng,Verpoort, Francis
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- Proton transfer from imidazole, benzimidazole, and their 1-alkyl derivatives. FMO analysis of the effect of methyl and benzo substitution
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The rate-pH profile for detritiation from the C-2 position of 1-methylimidazole has been determined in aqueous solution at 85 deg C.The profile is consistent with a mechanism involving attack by hydroxide ion on the conjugate acid of the substrate to give an ylid intermediate in the rate-determining step.At higher pH, hydroxide-catalyzed exchange of the neutral species becomes increasingly important.Comparison of the second-order rate constants derived from the rate-pH profiles of imidazole, 1-methylimidazole, benzimidazole, and 1-methylbenzimidazole showed that methyl substitution caused the rate to increase by 2- to 3-fold while benzo annelation increased the rate by 10- to 20-fold.Frontier molecular orbital (FMO) analysis of the reaction scheme for proton transfer from imidazole, benzimidazole, and their 1-alkyl derivatives has been used to explain the rate-accelerating effect of methyl substitution and benzo annelation in these processes.
- Buncel, Erwin,Joly, Helen A.,Jones, John R.
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- Self-Assembly of Benzimidazole-Derived Tris-NHC Ligands and AgI-Ions to Hexanuclear Organometallic Cages and Their Unusual Transmetalation Chemistry
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Multi-ligand self-assembly to attain the AgI-N-heterocyclic carbene (NHC)-built hexanuclear organometallic cages of composition [Ag6(3 a,b)4](PF6)6 from the reaction of benzimidazole-derived tris(azolium) salts [H3-3 a,b](PF6)3 with Ag2O was achieved. The molecular structures of the cages were established by X-ray diffraction studies along with NMR and MS analyses. The existence of a single assembly in solution was supported by diffusion-ordered spectroscopy (DOSY) 1H NMR spectra. Further, transmetalation reactions of these self-assembled complexes, [Ag6(3 a,b)4](PF6)6, with CuI/AuI-ions provided various coinage metal-NHC complexes having diverse molecular compositions, which included the first example of a hexanuclear CuI-dodecacarbene complex, [Cu6(3 b)4](PF6)6.
- Nishad, Rajeev C.,Rit, Arnab
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- A general method for the preparation of N-heterocyclic carbene-silver(I) complexes in water
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A new synthetic method leading to N-heterocyclic carbene-silver(I) complexes [(R2-NHC)2Ag]+ [AgX2] - is developed by using benzimidazolium compounds, NaOH (as a base), silver salts and water (as the reaction medium). Single-crystal X-ray structure revealed that compound 1 comprises a linear [Ag-(Et2-Bimy) 2]+ cation and a linear [AgBr2]- anion. These two ions are linked through an AgI-AgI association and staggered at an angle of 90.3.
- Saif, Muhammad Jawwad,Flower, Kevin R.
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- Walther reaction in the benzazoles series and preparation of their 2-deutero derivatives
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Reactions of 2-hydrazino-substituted 1-methylbenzimidazole, benzothiazole, and benzoxazole with azobenzene at 160-180°C resulted in hydrazino group elimination and formation of the corresponding 2-H-benzazoles. Under similar conditions the 2-deuterohydrazinobenzazoles prepared from 2-hydrazinobenzazoles and heavy water were converted into 2-deuterobenzazoles. Pleiades Publishing, Inc. 2006.
- Lomov,Yutilov,Smolyar
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- N-heterocyclic carbenes: VIII. Benzimidazolium diterpene salts with an oxo group in substituent
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Benzimidazolium salts with an oxo group in the substituent are synthesized from a diterpene ketone.
- Denisov,Usatykh,Gorbunov,Maiorova,Glushkov
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- Cleavages of 1-Methyl-2-trimethylsilylbenzimidazole and 2-Trimethylsilylbenzothiazole in Methanol and Related Media
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First order rate constants k at 25 deg C have been determined for the cleavage of 1-methyl-2-trimethylsilylbenzimidazole (I) and 2-trimethylsilylbenzothiazole (II) in MeOH, alone or containing NaOMe, and in 5:2 v/v MeOH-H2O containing HClO4.Compound (I) is cleaved rapidly by neutral methanol (1E3 k 51 s-1) (and also by H2O, 1E3 k 110 s-1 or EtOH, 1E3 k 3.0 s-1); very small amounts of NaOMe do not affect the rate (which thus refers to a spontaneous process), but larger amounts induce a base-catalysed process (1E2 k 63 l mol-1s-1).The data for the neutral cleavage of (I), including a rate isotope effect, r.i.e. , of 3.3, can be interpreted either in terms of the cyclic mechanism involving a solvent molecule previously proposed for cleavage of 2-trimethylsilylpyridine or one in which MeO(1-) attacks the protonated substrate.In base cleavage (I) gives an r.i.e. of 1.1, and this is interpreted in terms of proton transfer to the N of the N=C bond synchronous with breaking of the C-SiMe3 bond, but (II) gives an r.i.e. of 0.46, suggesting that there is little if any such electrophilic assistance.The low product isotope effects (the product ratio RH/RD on cleavage in 1:1 MeOH-MeOD) of 1.2-1.3 for neutral cleavage of (I) and the base cleavages of (I) and (II) are attributed to the fact that the isotopic composition of the product is determined in a step involving transfer of hydrogen to a localized carbanion.Addition of acid greatly raises the rate of cleavage of (II) in 5:2 MeOH-H2O, but reduces it for (I), for which the rate levels off at a value thought to refer to the fully protonated species.The acid-catalysed processes may involve attack of a solvent molecule at silicon in the protonated species.
- Seconi, Giancarlo,Eaborn, Colin
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- Menschutkin Reactions of N-Methylimidazole and of N-Methylbenzimidazole with Methyl Iodide in Acetonitrile-Methanol. Family-dependent and Family-independent Properties
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Rate constants and activation parameters have been determined for the reactions of the aromatic amines N-methylimidazole and N-methylbenzimidazole with methyl iodide in acetonitrile-methanol.The enthalpies of solution have also been determined for the relevant species in the same solvent mixtures.Activation enthalpies in acetonitrile and specific interaction enthalpies between the amine and methanol show a linear correlation with pKa values determined in water only over a narrowly defined type of structure.However, transition-state indices for the two reactions defined in terms of physical interaction energy, αphys and βphys, show the behaviour anticipated by analogy with reactions of pyridine derivatives. (i.e., family-independent character).
- Kondo, Yasuhiko,Izawa, Shingo,Kusabayashi, Shigekazu
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- Kinetic analysis of the complete mechanochemical synthesis of a palladium(II) carbene complex
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Benzimidazoline-2-ylidene complexes of palladium(II) were synthesized mechanochemically in a vibratory ball mill. Complete syntheses began with preparation of benzimidiazolium halides from commercially available starting materials. These “greener chemistr
- Allenbaugh, Rachel J.,Zachary, Jonathon R.,Underwood, A. Nicole,Bryson, J. Dillion,Williams, Joseph R.,Shaw, Angela
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- Solid-phase synthesis of 1,2-benzophenazine and some fused imidazole derivatives
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The solid-phase synthesis of 1,2-benzophenazine and various N-methylbenzimidazoles using o-diaminoarenes is very promising and permits the synthesis of 1-methyl-4,5-[b]naphtho-1H-imidazole, which could not be obtained by the condensation of o-diaminoarenes with paraformaldehyde using the standard liquid-phase method. 1996 Plenum Publishing Corporation.
- Zefirov,Sereda,Volkov,Tkachenko,Zyk
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- Synthesis of benzimidazoles from o-phenylenediamines and DMF derivatives in the presence of PhSiH3
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A simple approach to preparation of benzimidazoles from o-phenylenediamines and DMF derivatives, only employing PhSiH3 as promoter without any other additives, was reported. This route provided moderate to high yields with a broad substrate scope. A plausible mechanism for the reaction is proposed based on the spectroscopic characterization (e.g., HRMS and 1H NMR) of the reaction mixture.
- Zhu, Jianhua,Zhang, Zhenbei,Miao, Chengxia,Liu, Wei,Sun, Wei
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- An interchangeable homogeneous ? heterogeneous catalyst system for furfural upgrading
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Intercalation of benzimidazolium cations [BI]+ into the nanogalleries of Na+/montmorillonite (MMT) clay leads to generation of recyclable supported precatalysts [BI]+/MMT, which, upon treatment with a base, catalyze furfural self-condensation coupling reaction into furoin in almost constant yields of >96% over the three cycles investigated. This catalyst system combines the best features of both homogeneous and heterogeneous catalyst systems, as it performs the homogeneous molecular catalysis by the discharged N-heterocyclic carbene catalyst in solution and then recovers the catalyst through in situ heterogenization after the reaction via re-intercalation of the charged precatalyst. The [12,12BI]+/MMT catalyst system carrying two long-chain C12 dodecyl substituents on the [BI] nitrogen atoms is particularly effective for achieving both high product yield and catalyst recyclability.
- Wang, Lu,Chen, Eugene Y.-X.
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- The reaction of 1-ethoxycarbonyl-3-methylbenzimidazolium salts with electrogenerated and potassium superoxide
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1-Ethoxycarbonyl-3-methylbenzimidazolium salts, which have two possible reactive sites toward superoxide, were allowed to react with KO2 and electrogenerated superoxide to give the ring-opened products and 1- methylbenzimidazoles. The former compounds were specific products for superoxide, and the product distributions were revealed to depend on the counter cation of superoxide.
- Itoh,Nagata,Okada,Ohsawa
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- ACYLATION OF BENZIMIDAZOLE BY THE REGEL-BUECHEL METHOD. 2. DEACYLATION AND DISSOCIATION OF 1-METHYL-3-ACYL-2-(1'-METHYL-2'-BENZIMIDAZOLYL)-4-BENZIMIDAZOLINES
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With excess acyl halide 1-methyl-3-acyl-2-(1'-methyl-2'-benzimidazolyl)-4-benzimidazoline is converted to an unstable 1-methyl-3-acyl-2-(1'-methyl-3-acyl-4'-benzimidazolin-2'-yl)benzimidazolium chloride, which undergoes intramolecular redox cleavage with the formation of 1,1'-dimethyl-2,2'-dibenzimidazolyl and an aldehyde and dissociates at the C-C bond that connects the benzimidazolium and benzimidazoline fragments into a carbene yield and a 1-methyl-3-acylbenzimidazolium chloride.
- Khristich, B. I.,Bondarenko, E. V.
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- Interplay of the intermolecular and intramolecular interactions in stabilizing the thione-based copper(I) complexes and their significance in protecting the biomolecules against metal-mediated oxidative damage
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The synthesis, characterization, and X-ray structure of a series of mono, tri, and polynuclear copper complexes of benzimidazole-based N-substituted thiones, BzMeSH (10) and BzOHSH (11), and N,N'-disubstituted, BzMeSMe (12) and BzOHSMe (13) are reported here. The X-ray structure analyses of the copper-thione complexes have revealed that the coordination behaviour and the geometry of the central metal ion in these complexes are significantly dependent on the type of the counter anion used in the reaction. For instance, the reactions of benzimidazole-based thiones with CuCl2 afforded mononuclear trigonal planar Cu(I) complexes 14, 15, 18, and 19. On contrast, upon reaction with CuSO4, 10 afforded the trinuclear copper complex 16, in which thione 10 acts as a bridging as well as terminal ligand, leading to the formation of a six-membered Cu3S3 cluster. The chair-form of six-membered Cu3S3 ring is further stabilized by six intramolecular H-bonding interactions, with overall stabilization energy of 19.28 kcal.mol?1, between the free NH group of 10 and O atom of the counter anion SO42–. Whereas, when thione 10 was reacted with CuI, a 1D-polymeric chain-like copper complex 17 was obtained as a thermodynamically stable product, in which both 10 and iodine act as bridging ligand. The 3D network of complexes has revealed that these copper-thione compounds are stabilized by the presence of various types of intermolecular and intramolecular H-bonding and π ? π stacking interactions in the solid state. NBO analysis of the crystal geometries revealed that the strength of these interactions ranging from 0.14 to 5.67 kcal.mol?1. We have also demonstrated that the N-substituted thiones have excellent reactive oxygen species (ROS) scavenging property and, thus, protect biomolecules including DNA and protein against Cu(I)-mediated oxidative damage.
- Chalana, Ashish,Karri, Ramesh,Kumar Jha, Kunal,Kumar Rai, Rakesh,Kumar, Binayak,Roy, Gouriprasanna
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supporting information
(2022/01/26)
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- Methanol as the C1source: Redox coupling of nitrobenzenes and alcohols for the synthesis of benzimidazoles
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We present an operationally simple redox coupling for the synthesis of N-1 substituted benzimidazoles using feedstock building block 2-nitroaniline derivatives as the precursors and methanol as the C1 source. Higher atom, step, and redox economies and exc
- An, Jie,Lai, Zemin,Li, Hengzhao,Peng, Mengqi,Sun, Yanhao,Yan, Zihan,Yang, Ruoyan,Zhang, Yuntong
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supporting information
p. 748 - 753
(2022/02/02)
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- Using Methanol as a Formaldehyde Surrogate for Sustainable Synthesis of N-Heterocycles via Manganese-Catalyzed Dehydrogenative Cyclization
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The development of an efficient and sustainable synthetic route for formaldehyde production from renewable feedstock, especially in combination with a subsequent transformation to straightforwardly construct valuable chemicals, is highly desirable. Herein, we report a novel manganese-catalyzed dehydrogenative cyclization of methanol as a formaldehyde surrogate with a variety of dinucleophiles for facile synthesis of N-heterocycles. The in situ generated formaldehyde via catalytic methanol dehydrogenation can be selectively trapped by diverse dinucleophiles to avoid several possible side reactions. The utility of this transformation is further highlighted by its successful application to the synthesis of 13C-labeled N-heterocycles using 13CH3OH as a readily accessible 13C-isotope reagent.
- Li, Yibiao,Liu, Qiang,Shao, Zhihui,Yuan, Shanshan
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supporting information
(2022/02/23)
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- Cu-Catalyzed C-H Allylation of Benzimidazoles with Allenes
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CuH-catalyzed intramolecular cyclization and intermolecular allylation of benzimidazoles with allenes have been described. The reaction proceeded smoothly with the catalytic system of Cu(OAc)2/Xantphos and catalytic amount of (MeO)2MeSiH. This protocol features mild reaction conditions and a good tolerance of substrates bearing electron-withdrawing, electron-donating, or electron-neutral groups. A new catalytic mechanism was proposed for this copper hydride catalytic system.
- Dong, Yaxi,Breit, Bernhard
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supporting information
p. 6765 - 6769
(2021/09/11)
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- Benzimidazole- And Imidazole-Fused Selenazolium and Selenazinium Selenocyanates: Ionic Organoselenium Compounds with Efficient Peroxide Scavenging Activities
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Three new classes of ionic organoselenium compounds containing cationic benzimidazolium and imidazolium ring systems with selenocyanates as counterions are described. The cyclization of N,N′-disubstituted benzimidazolium and imidazolium bromides having N-(CH2)2-Br and N-(CH2)3-Br groups in the presence of potassium selenocyanate (KSeCN) led to formation of the corresponding selenazolium selenocyanates (21a, 21b, 22a, and 22b) and selenazinium selenocyanates (21c, 21d, 22c, and 22d). However, the open-chain selenocyanates with additional selenocyanate counterions (21e, 21f, 22e, and 22f) were formed from the N,N′-disubstituted benzimidazolium and imidazolium bromides having N-(CH2)6-Br groups. Mechanistic studies were carried out to understand the feasibility of such cyclization processes in the presence of KSeCN. The compounds were studied further for their potencies to catalytically reduce H2O2 in the presence of thiols. Interestingly, the cyclic selenazolium (21a, 21b, 22a, and 22b) and selenazinium compounds (21c, 21d, 22c, and 22d) exhibited significantly higher antioxidant activities than the corresponding acyclic selenocyanates (21f, 22e, and 22f). Selected compounds (22d and 22e) were further evaluated for their potencies in modulating the intracellular level of reactive oxygen species (ROS) in a representative macrophage cell line (RAW 264.7). Owing to the cationic nature of compounds, they may target and scavenge mitochondrial ROS in the cellular medium.
- Banerjee, Kaustav,Bhattacherjee, Debojit,Mahato, Sulendar K.,Sufian, Abu,Bhabak, Krishna Pada
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p. 12984 - 12999
(2021/08/30)
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- Iodine(I) and Silver(I) Complexes of Benzoimidazole and Pyridylcarbazole Derivatives
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The synthesis of iodine(I) complexes with either benzoimidazole or carbazole-derived sp2 N-containing Lewis bases is described, as well as their corresponding silver(I) complexes. The addition of elemental iodine to the linear two-coordinate Ag
- Rissanen, Kari,Siepmann, Marcel,Taipale, Essi,Truong, Khai-Nghi
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supporting information
p. 17412 - 17419
(2021/10/19)
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- Slow 3MLCT Formation Prior to Isomerization in Ruthenium Carbene Sulfoxide Complexes
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A series of photochromic complexes with general formulas of [Ru(bpy)2(NHC-SR)]2+ and [Ru(bpy)2(NHC-S(O)R)]2+ were prepared and investigated by X-ray crystallography, electrochemistry, and ultrafast transient absorption spectroscopy {where bpy is 2,2′-bipyridine and NHC-SR and NHC-S(O)R are chelating thioether (-SR) and chelating sulfoxide [-S(O)R] N-heterocyclic carbene (NHC) ligands}. The only differences between these complexes are the nature of the R group on the sulfur (Me vs Ph), the identity of the carbene (imidazole vs benzimidazole), and the number of linker atoms in the chelate (CH2 vs C2H4). A total of 13 structures are presented {four [Ru(bpy)2(NHC-SR)]2+ complexes, four [Ru(bpy)2(NHC-S(O)R)]2+ complexes, and five uncomplexed ligands}, and these reveal the expected coordination geometry as predicted from other spectroscopy data. The data do not provide insight into the photochemical reactivity of these compounds. These carbene ligands do impart stability with respect to ground state and excited state ligand substitution reactions. Bulk photolysis reveals that these complexes undergo efficient S → O isomerization, with quantum yields ranging from 0.24 to 0.87. The excited state reaction occurs with a time constant ranging from 570 ps to 1.9 ns. Electrochemical studies reveal an electron transfer-triggered isomerization, and voltammograms are consistent with an ECEC (electrochemical-chemical electrochemical-chemical) reaction mechanism. The carbene facilitates an unusually slow S → O isomerization and an unusally fast O → S isomerization. Temperature studies reveal a small and negative entropy of activation for the O → S isomerization, suggesting an associative transition state in which the sulfoxide simply slides along the S-O bond during isomerization. Ultrafast studies provide evidence of an active role of the carbene in the excited state dynamics of these complexes.
- Breen, Douglas J.,Rack, Jeffrey J.,Schrage, Briana R.,Thapa Magar, Rajani,Ziegler, Christopher J.
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p. 16120 - 16127
(2021/11/13)
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- Highly Efficient and Catalyst-Free Synthesis of Benzimidazoles in Aqueous Media
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Abstract: A convenient and highly efficient, catalysts-free synthesis of benzimidazoles in an aqueous medium has been developed. The conditions of the synthesis were optimized, and its scope was successfully extended to various substrates with good to excellent yields. The experimental procedure is simple, and the products can be isolated by filtration followed by recrystallization from water.
- Huang, W.-H.,Jin, Y.-J.,Ma, L.-F.,Wu, Y.,Zhou, L.-H.
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p. 825 - 830
(2021/06/12)
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- Simple RuCl3-catalyzed N-Methylation of Amines and Transfer Hydrogenation of Nitroarenes using Methanol
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Methanol is a potential hydrogen source and C1 synthon, which finds interesting applications in both chemical synthesis and energy technologies. The effective utilization of this simple alcohol in organic synthesis is of central importance and attracts scientific interest. Herein, we report a clean and cost-competitive method with the use of methanol as both C1 synthon and H2 source for selective N-methylation of amines by employing relatively cheap RuCl3.xH2O as a ligand-free catalyst. This readily available catalyst tolerates various amines comprising electron-deficient and electron-donating groups and allows them to transform into corresponding N-methylated products in moderate to excellent yields. In addition, few marketed pharmaceutical agents (e. g., venlafaxine and imipramine) were also successfully synthesized via late-stage functionalization from readily available feedstock chemicals, highlighting synthetic value of this advanced N-methylation reaction. Using this platform, we also attempted tandem reactions with selected nitroarenes to convert them into corresponding N-methylated amines using MeOH under H2-free conditions including transfer hydrogenation of nitroarenes-to-anilines and prepared drug molecules (e. g., benzocaine and butamben) as well as key pharmaceutical intermediates. We further enable one-shot selective and green syntheses of 1-methylbenzimidazole using ortho-phenylenediamine (OPDA) and methanol as coupling partners.
- Sarki, Naina,Goyal, Vishakha,Tyagi, Nitin Kumar,Puttaswamy,Narani, Anand,Ray, Anjan,Natte, Kishore
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p. 1722 - 1729
(2021/04/19)
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- Highly efficient one pot synthesis of benzimidazoles from 2-nitroaniline and PhSiH3 as reducing agent catalyzed by Pd/C as a heterogeneous catalyst
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This work reports an efficient route for the synthesis of benzimidazole from o-nitroaniline in the presence of carbon dioxide atmosphere, PhSiH3 as a reducing agent catalyzed by Pd/C as a catalyst. Benzimidazoles have become the focus of organic chemists, as benzimidazole is an important intermediate in medicinal chemistry. We have developed more efficient route for the synthesis benzimidazole and various substituted benzimidazoles have been synthesized in good to excellent yield. The TBD (1,5,7-Triazabicyclo [4.4.0] dec-5-ene) is selected as a base as it promotes the CO2 insertion. Benzimidazoles were synthesized through reduction of nitro group followed by cyclization of amine using CO2 as a carbon source. Moreover, the Pd/C catalyst can be recycled up to five recycle run without significant changes in the yield of the product.
- Phatake, Vishal V.,Bhanage, Bhalchandra M.
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- Reductive cyclization of o-phenylenediamine with CO2 and BH3NH3 to synthesize 1H-benzoimidazole derivatives
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A simple and green protocol was developed for the reductive cyclization of o-phenylenediamine with CO2 and BH3NH3 to yield 1H-benzimidazole. The desired 1H-benzimidazole derivatives were produced under mild conditions. Mechanism investigation indicated that the coordination of o-phenylenediamine with the boron atom of BH3NH3 promoted the transfer of the formyl group to form a stable intermediate, which facilitated the intramolecular nucleophilic addition-elimination for the formation of target product. In this process, BH3NH3 served multifunctional roles, acting as a reducing agent and a formylation catalyst.
- Li, Xiao,Zhang, Junhua,Yang, Yue,Hong, Hailong,Han, Limin,Zhu, Ning
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supporting information
(2021/09/28)
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- N-Heterocyclic Carbene (NHC)-Stabilized Ru0 Nanoparticles: In Situ Generation of an Efficient Transfer Hydrogenation Catalyst
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Tethered and untethered ruthenium half-sandwich complexes were synthesized and characterized spectroscopically. X-ray crystallographic analysis of three untethered and two tethered Ru N-heterocyclic carbene (NHC) complexes were also carried out. These RuNHC complexes catalyze transfer hydrogenation of aromatic ketones in 2-propanol under reflux, optimally in the presence of (25 mol %) KOH. Under these conditions, the formation of 2–3 nm-sized Ru0 nanoparticles was detected by TEM measurements. A solid-state NMR investigation of the nanoparticles suggested that the NHC ligands were bound to the surface of the Ru nanoparticles (NPs). This base-promoted route to NHC-stabilized ruthenium nanoparticles directly from arene-tethered ruthenium–NHC complexes and from untethered ruthenium–NHC complexes is more convenient than previously known routes to NHC-stabilized Ru nanocatalysts. Similar catalytically active RuNPs were also generated from the reaction of a mixture of [RuCl2(p-cymene)]2 and the NHC precursor with KOH in isopropanol under reflux. The transfer hydrogenation catalyzed by these NHC-stabilized RuNPs possess a high turnover number. The catalytic efficiency was significantly reduced if nanoparticles were exposed to air or allowed to aggregate and precipitate by cooling the reaction mixtures during the reaction.
- Kathuria, Lakshay,Din Reshi, Noor U.,Samuelson, Ashoka G.
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supporting information
p. 7622 - 7630
(2020/05/29)
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- Visible-light-induced aerobic oxidative desulfurization of 2-mercaptobenzimidazolesviaa sulfinyl radical
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A mild transition-metal-free non-toxic aerobic photoredox system was found to enable highly efficient desulfurization of 2-mercaptobenzimidazoles. This viable catalytic system includes Rose Bengal in a low catalyst loading as a photosensitizer and cheap, non-toxic NaCl in a catalytic amount as an additive, combined with an oxygen atmosphere. This protocol provides an important alternative access to a broad range of benzimidazole and deuterated benzimidazole products in generally high yields with good tolerance of various synthetically and pharmaceutically useful functionalities. The mechanistic studies reveal that both single electron transfer and energy transfer probably occur in the initial step and a sulfinyl radical intermediate is involved in the key desulfurization process.
- Deng, Guo-Jun,Fu, Mei,Huang, Huawen,Ji, Xiaochen,Li, Yongtong
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supporting information
p. 5594 - 5598
(2020/09/21)
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- Facile access to: N-formyl imide as an N-formylating agent for the direct synthesis of N-formamides, benzimidazoles and quinazolinones
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N-Formamide synthesis using N-formyl imide with primary and secondary amines with catalytic amounts of p-toluenesulfonic acid monohydrate (TsOH·H2O) is described. This reaction is performed in water without the use of surfactants. Moreover, N-formyl imide is efficiently synthesized using acylamidines with TsOH·H2O in water. In addition, N-formyl imide was successfully used as a carbonyl source in the synthesis of benzimidazole and quinazolinone derivatives. Notable features of N-formylation of amines by using N-formyl imide include operational simplicity, oxidant- A nd metal-free conditions, structurally diverse products, and easy applicability to gram-scale operation.
- Huang, Hsin-Yi,Liang, Chien-Fu,Lin, Xiu-Yi,Yen, Shih-Yao
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supporting information
p. 5726 - 5733
(2020/08/21)
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- Endogenous X-C=O species enable catalyst-free formylation prerequisite for CO2reductive upgrading
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CO2, the main component of greenhouse gas, is currently developed as a promising surrogate of carbon feedstock. Among various conversion routes, CO2undergoing catalytic reduction can furnish hydrogen/energy carriers and value-added chemicals, while specific metal-containing catalysts or organocatalysts are often prerequisite for smooth proceeding of the involved reaction processes. In this work, both formic acid and N-containing benzoheterocyclic compounds (including various benzimidazoles, benzothiazole, and benzoxazole) along with silanols could be synthesized with high yields (>90%) from catalyst-free reductive upgrading of CO2under mild conditions (50 °C). The endogenous X-CO species, derived from the N-methyl-substituted amide-based solvent [Me2N-C(O)-R], especially PolarClean, and O-formyl group [O-C(O)-H] of in situ formed silyl formate, were found to play a prominent promotional role in the activation of the used hydrosilane for reductive CO2insertion, as demonstrated by density functional theory (DFT) calculations and isotopic labeling experiments. Moreover, reaction mechanisms and condition-based sensitivity assessment were also delineated.
- Dai, Wenshuai,Li, Hu,Saravanamurugan, Shunmugavel,Wu, Hongguo,Yang, Song
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p. 5822 - 5832
(2020/10/21)
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- C-C Bond Cleavage of Unactivated 2-Acylimidazoles
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2-Acylimidazoles are widely used as post-Transformable carboxylic acid equivalents in chemoselective and enantioselective reactions. Their transformations, however, require pretreatment with highly reactive, toxic methylating reagents to facilitate C-C bond cleavage. Here, we demonstrate that such pretreatment can be avoided and the C-C bond cleaved under neutral conditions without the use of additional reagents or catalysts. The scope of the reaction, including the use of products reported in the literature as substrates, and some mechanistic insights are described.
- Xin, Hai-Long,Pang, Bo,Choi, Jeesoo,Akkad, Walaa,Morimoto, Hiroyuki,Ohshima, Takashi
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p. 11592 - 11606
(2020/10/23)
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- Metal-Free Synthesis of Benzimidazoles via Oxidative Cyclization of d -Glucose with o-Phenylenediamines in Water
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d-Glucose has been identified as an efficient C1 synthon in the synthesis of benzimidazoles from o-phenylenediamines via an oxidative cyclization strategy. Isotopic studies with 13C6-d-glucose and D2O unambiguously confirmed the source of methine. The notable features of this method include the following: broad functional group tolerance, a biorenewable methine source, excellent reaction yields, a short reaction time, water as an environmentally benign solvent, and the synthesis of vitamin B12 component on the gram scale.
- Raja, Dineshkumar,Philips, Abigail,Palani, Pushbaraj,Lin, Wei-Yu,Devikala, Sundaramurthy,Senadi, Gopal Chandru
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p. 11531 - 11540
(2020/10/12)
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- Transition-metal and oxidant-free approach for the synthesis of diverse N-heterocycles by TMSCl activation of isocyanides
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A highly efficient TMSCl-mediated addition of N-nucleophiles to isocyanides has been achieved. This transition-metal and oxidant-free strategy has been applied to the construction of various N-heterocyles such as quinazolinone, benzimidazole and benzothiazole derivatives by the use of distinct amino-based binucleophiles. The notable feature of this protocol includes its mild reaction condition, broad functional group tolerance and excellent yield. This journal is
- Chen, Fen-Er,Dong, Lin,Li, Hongyan,Liu, Jinxin,Luo, Liangliang,Xiao, You-Cai,Zhou, Yuan
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p. 29257 - 29262
(2020/10/02)
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- K2S as Sulfur Source and DMSO as Carbon Source for the Synthesis of 2-Unsubstituted Benzothiazoles
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We describe a three-component reaction of o-iodoanilines with K2S and DMSO that provides 2-unsubstituted benzothiazoles in moderate to good isolated yields with good functional group tolerance. Electron-rich aromatic amines and o-phenylenediamines instead of o-iodoanilines provided 2-unsubstituted benzothiazoles and 2-unsubstituted benzimidazoles with and without K2S under similar conditions. Notably, DMSO plays three vital roles: carbon source, solvent, and oxidant.
- Deng, Guobo,Kuang, Daizhi,Liang, Yun,Yang, Yuan,Yu, Jiangxi,Zhang, Fuxing,Zhu, Xiaoming
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supporting information
p. 3789 - 3793
(2020/06/04)
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- Synthesis method of ammonium acetate mediated benzimidazole compound
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The invention discloses a synthesis method of a benzimidazole compound mediated by ammonium acetate. The synthesis method comprises the following steps: adding an o-phenylenediamine compound, dimethylsulfoxide, an additive 1 and an additive 2 into a reaction tube, carrying out a stirring reaction at 130-150 DEG C, cooling the reaction product to room temperature after the reaction is finished, and carrying out separation and purification on the product to obtain the benzimidazole compound. The invention develops a method for synthesizing a benzimidazole compound under the mediation of ammonium acetate by taking DMSO as a carbon source and an oxidant and an o-phenylenediamine compound as a substrate under the condition of no metal catalyst. The synthesis method does not need a metal catalyst, and the required carbon source and oxidant have the characteristics of low toxicity, low price, easiness in obtaining, stable performance and the like. The method has the advantages of easiness inoperation, few steps, mild reaction conditions, better functional group tolerance and the like, and provides a new valuable way for synthesizing benzimidazole compounds.
- -
-
Paragraph 0069-0071
(2020/11/23)
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- Selective Methylation of Amides, N-Heterocycles, Thiols, and Alcohols with Tetramethylammonium Fluoride
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We herein disclose the use of tetramethylammonium fluoride (TMAF) as a direct and selective methylating agent of a variety of amides, indoles, pyrroles, imidazoles, alcohols, and thiols. The method is characterized by operational simplicity, wide scope, and ease of purification. Our computational studies suggest a concerted methylation-deprotonation as the preferred reaction pathway.
- Cheng, Hong-Gang,Pu, Maoping,Kundu, Gourab,Schoenebeck, Franziska
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supporting information
p. 331 - 334
(2019/12/30)
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- METHODS FOR PREPARING FORMALDEHYDE FROM CARBON DIOXIDE
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The present disclosure provides, inter alia, methods for preparing formaldehyde from carbon dioxide using bis(silyl)acetals, methods for incorporating carbon derived from carbon dioxide into a complex organic molecule derived from formaldehyde using bis(silyl)acetals, and methods for generating an isotopologue of a complex organic molecule derived from formaldehyde using bis(silyl)acetals.
- -
-
Paragraph 0017
(2020/11/27)
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- Carbonylative Acetylation of Heterocycles
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Herein, a new procedure for the carbonylative acetylation of heterocycles has been developed. In this process, organic peroxide acts as the methyl source. Various heterocycles were transformed into the corresponding methyl heterocyclic ketones in moderate to good yields.
- Zhang, Youcan,Yin, Zhiping,Wu, Xiao-Feng
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supporting information
p. 213 - 216
(2020/01/22)
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- Benzimidazolium salts prevent and disrupt methicillin-resistant: Staphylococcus aureus biofilms
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Emergence of resistant bacteria encourages us to develop new antibiotics and strategies to compensate for the different mechanisms of resistance they acquire. One of the defense mechanisms of resistant bacteria is the formation of biofilms. Herein we show
- Schmitzer, Andreea R.,Tessier, Jérémie
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p. 9420 - 9430
(2020/03/19)
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- Tetracoordinate borates as catalysts for reductive formylation of amines with carbon dioxide
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We report sodium trihydroxyaryl borates as the first robust tetracoordinate organoboron catalysts for reductive functionalization of CO2. These catalysts, easily synthesized from condensing boronic acids with metal hydroxides, activate main group element-hydrogen (E-H) bonds efficiently. In contrast to BX3 type boranes, boronic acids and metal-BAr4 salts, under transition metal-free conditions, sodium trihydroxyaryl borates exhibit high reactivity of reductive N-formylation toward a variety of amines (106 examples), including those with functional groups such as ester, olefin, hydroxyl, cyano, nitro, halogen, MeS-, ether groups, etc. The over-performance to catalyze formylation of challenging pyridyl amines affords a promising alternative method to the use of traditional formylation reagents. Mechanistic investigation supports electrostatic interactions as the key for Si/B-H activation, enabling alkali metal borates as versatile catalysts for hydroborylation, hydrosilylation, and reductive formylation/methylation of CO2.
- Du, Chen-Xia,Huang, Zijun,Jiang, Xiaolin,Li, Yuehui,Makha, Mohamed,Wang, Fang,Zhao, Dongmei
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supporting information
p. 5317 - 5324
(2020/09/17)
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- Cytotoxic effects of coumarin substituted benzimidazolium salts against human prostate and ovarian cancer cells
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Abstract: Coumarin and benzimidazole derivatives have individual biological activities including anticancer. In this study, we aimed to synthesize coumarin-benzimidazole hybrids in order to investigate their anticancer properties. For this purpose, six 6-substituted-4-chloromethylene coumarin derivatives were synthesized. Sixteen coumarin substituted benzimidazolium chlorides were synthesized by the reaction of 4-chloromethylene coumarin and N-benzylbenzimidazole derivatives. All of the synthesized compounds were characterized by 1H and 13C NMR, IR spectroscopic techniques and elemental analyses. Cytotoxicities of all compounds were tested by [3-(4,5-dimethylthiazole)-2-yl]-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay against human prostate (PC-3) and ovarian (A2780) cancer cells. All compounds performed significant cytotoxicities at 100μM against both cancer cell lines. Moreover, some compounds performed significant activities at 1μM against both cancer cell lines and the obtained results suggest that this type of compounds are promising candidates for the treatment of human prostate and ovarian cancers. Graphic abstract: Six 4-chloromethylenecoumarin derivatives and sixteen coumarin substituted benzimidazolium chlorides were synthesized and characterized. Cytotoxic properties of all compounds were tested against human prostate and ovarian cancer cell lines.[Figure not available: see fulltext.].
- Karata?, Mert Olgun,Tekin, Suat,Alici, Bülent,Sandal, Süleyman
-
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- Reductive dehalogenation and dehalogenative sulfonation of phenols and heteroaromatics with sodium sulfite in an aqueous medium
-
Prototropic tautomerism was used as a tool for the reductive dehalogenation of (hetero)aryl bromides and iodides, or dehalogenative sulfonation of (hetero)aryl chlorides and fluorides, using sodium sulfite as the sole reagent in an aqueous medium. This protocol does not require a metal or phase transfer catalyst and avoids using organic solvent as the reaction medium. This method is especially suitable for substrates that readily tautomerize (such as 2-or 4-halogenated aminophenols and 4-halogenated resorcinols), for which dehalogenation or sulfonation proceeds under mild reaction conditions (≤60 °C). As sodium sulfite is an inexpensive, safe, and environmentally less hazardous reagent, this method has at least three potential applications: (i) in the deprotection of halogens as protecting groups, using sodium sulfite as a reducing agent; (ii) in the sulfonation of aromatic halides under mild reaction conditions avoiding hazardous and corrosive reagents/solvents; and (iii) in the transformation of toxic halogenated aromatics into less harmful compounds.
- Tomanová, Monika,Jedinák, Luká?,Canka?, Petr
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supporting information
p. 2621 - 2628
(2019/06/03)
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- Synthesis of Some Benzimidazole-based Heterocycles and their Application as Copper Corrosion Inhibitors
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A series of new substituted benzimidazoles embedded with a variety of function groups has been synthesized from N-methyl-2-bromoacetylbenzimidazole. The synthesized compounds were fully characterized, and their structures were elucidated based on elemental analysis, spectral data, and alternative synthetic pathways, whenever possible. Some of benzimidazole derivatives were tested as corrosion inhibitors.
- Eldebss, Taha M. A.,Farag, Ahmad M.,Shamy, Adel Y. M.
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p. 371 - 390
(2019/01/08)
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- Selective Conversion of Carbon Dioxide to Formaldehyde via a Bis(silyl)acetal: Incorporation of Isotopically Labeled C1 Moieties Derived from Carbon Dioxide into Organic Molecules
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The conversion of carbon dioxide to formaldehyde is a transformation that is of considerable significance in view of the fact that formaldehyde is a widely used chemical, but this conversion is challenging because CO2 is resistant to chemical transformations. Therefore, we report here that formaldehyde can be readily obtained from CO2 at room temperature via the bis(silyl)acetal, H2C(OSiPh3)2. Specifically, formaldehyde is released from H2C(OSiPh3)2 upon treatment with CsF at room temperature. H2C(OSiPh3)2 thus serves as a formaldehyde surrogate and provides a means to incorporate CHx (x = 1 or 2) moieties into organic molecules. Isotopologues of H2C(OSiPh3)2 may also be synthesized, thereby providing a convenient means to use CO2 as a source of isotopic labels in organic molecules.
- Rauch, Michael,Strater, Zack,Parkin, Gerard
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supporting information
p. 17754 - 17762
(2019/11/05)
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- Method for methylation reaction
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The invention relates to a method for a methylation reaction. The method is characterized in that a reaction substrate is reacted in an organic solvent in the presence of an alkali with methyl trifluoroacetate as a methylation reagent to obtain a corresponding methylated product. The method is a new methylation method, and has the advantages of cheapness, easiness in operation, mild reaction conditions, wide application range of the substrate, avoiding of dimethyl sulfate, iodomethane and other highly toxic methylation reagents, and obtaining of the methylated product with a high yield.
- -
-
Paragraph 0013
(2019/01/21)
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- Commercial Pd/C-Catalyzed N-Methylation of Nitroarenes and Amines Using Methanol as Both C1 and H2 Source
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Herein, we report commercially available carbon-supported-palladium (Pd/C)-catalyzed N-methylation of nitroarenes and amines using MeOH as both a C1 and a H2 source. This transformation proceeds with high atom-economy and in an environmentally friendly way via borrowing hydrogen mechanism. A total of >30 structurally diverse N-methylamines, including bioactive compounds, were selectively synthesized with isolated yields of up to 95%. Furthermore, selective N-methylation and deuteration of nimesulide, a nonsteroidal anti-inflammatory drug, were realized through the late-stage functionalization.
- Goyal, Vishakha,Gahtori, Jyoti,Narani, Anand,Gupta, Piyush,Bordoloi, Ankur,Natte, Kishore
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p. 15389 - 15398
(2019/12/04)
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- Cu@U-g-C3N4 Catalyzed Cyclization of o-Phenylenediamines for the Synthesis of Benzimidazoles by Using CO2 and Dimethylamine Borane as a Hydrogen Source
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Abstract: This work reports a green and sustainable route for the synthesis of benzimidazoles via C–N bond formation using carbon dioxide (CO2) as a C1 carbon source. In this work, Cu@U-g-C3N4 catalyst was prepared from urea derived porous graphitic carbon?nitride (U-g-C3N4) and CuCl2 and characterized by FT-IR, XRD, XPS, SEM, TPD etc. The Cu@U-g-C3N4 as a heterogeneous recyclable catalyst has been employed first time for the cyclization of o-phenylenediamines (OPD) with CO2 to benzimidazoles using dimethylamine borane (DMAB). The proposed protocol becomes sustainable and efficient due to the use of propylene carbonate/water as a suitable biodegradable, economical and environmentally benign solvent system. The proposed catalytic system showed a wide range of substrate scope for the synthesis of benzimidazoles in good to excellent yields. Graphical Abstract: [Figure not available: see fulltext.]
- Phatake, Vishal V.,Bhanage, Bhalchandra M.
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p. 347 - 359
(2018/11/23)
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- In Situ Formation of Frustrated Lewis Pairs in a Water-Tolerant Metal-Organic Framework for the Transformation of CO2
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Frustrated Lewis pairs (FLPs) consist of sterically hindered Lewis acids and Lewis bases, which provide high catalytic activity towards non-metal-mediated activation of “inert” small molecules, including CO2 among others. One critical issue of homogeneous FLPs, however, is their instability upon recycling, leading to catalytic deactivation. Herein, we provide a solution to this issue by incorporating a bulky Lewis acid-functionalized ligand into a water-tolerant metal-organic framework (MOF), named SION-105, and employing Lewis basic diamine substrates for the in situ formation of FLPs within the MOF. Using CO2 as a C1-feedstock, this combination allows for the efficient transformation of a variety of diamine substrates into benzimidazoles. SION-105 can be easily recycled by washing with MeOH and reused multiple times without losing its identity and catalytic activity, highlighting the advantage of the MOF approach in FLP chemistry.
- Shyshkanov, Serhii,Nguyen, Tu N.,Ebrahim, Fatmah Mish,Stylianou, Kyriakos C.,Dyson, Paul J.
-
supporting information
p. 5371 - 5375
(2019/03/17)
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- Alkylation method for nitrogen-hydrogen containing compounds and application thereof
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The invention discloses an alkylation method for nitrogen-hydrogen containing compounds and an application thereof, belonging to the technical field of synthesis of organic compounds. The invention provides a series of methods for a nitrogen alkylation reaction of N-H containing heterocyclic compounds (II) with N,N-dimethylformamide dialkyl acetal as an alkyl source under the condition of no participation of metals, and a product with a hydrogen atom on a nitrogen atom substituted by R1 is obtained. The method provided by the invention has the advantages of highly-efficient reaction, high yield, simple treatment after the reaction, simple and convenient operation, mild reaction conditions, no participation of the metals, high tolerance of functional groups of a reaction substrate, wide range and easy preparation of the substrate, high reaction efficiency after amplification of the reaction, and applicability to large-scale industrial production.
- -
-
Paragraph 0039-0041; 0059; 0060
(2018/10/04)
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- Efficient N-Heterocyclic Carbene/Ruthenium Catalytic Systems for the Alcohol Amidation with Amines: Involvement of Poly-Carbene Complexes?
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The atom-economic direct amidation of alcohols with amines has been recently highlighted as an attractive and promising transformation. Among the versatile reported catalytic systems, in situ generated N-heterocyclic carbene (NHC)/ruthenium (Ru) catalytic systems have demonstrated their advantages such as easy operation and use of commercial Ru compounds. However, the existing catalyst loadings are relatively high, and additional insights for the in situ catalyst generation are still not well-documented. In this work, a variety of benzimidazole-based NHC precursors were initially synthesized. Through the screening of various NHC precursors and other reaction conditions, active in situ catalytic systems were discovered for the efficient amide synthesis. Notably, the catalyst loading is as low as 0.5 mol %. Furthermore, additional experiments were performed to validate the rationale for the superiority of the current catalytic systems over our previous system. It was observed that the ligand structure is one of the reasons for the higher activity. In addition, the higher ratio of the NHC precursor/[Ru] is another important factor for the improvement. Further HR-MS analysis identified the formation of two mono-NHC-Ru species as major species and two Ru species bearing multiple NHC ligands as minor species. Hopefully, the efficient and readily-accessible catalytic systems reported herein could demonstrate great potential for further practical applications.
- Cheng, Hua,Xiong, Mao-Qian,Zhang, Ni,Wang, Hua-Jing,Miao, Yang,Su, Wei,Yuan, Ye,Chen, Cheng,Verpoort, Francis
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p. 4338 - 4345
(2018/09/06)
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- Deciphering the anthelmintic activity of benzimidazolium salts by experimental and in-silico studies
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Inspired from the facts that majority of the drug administrated in the form of salts and “poison is in the dose”; herein, we have synthesized and characterized 1-methyl-3-alkylbenzimidazolium and 1-methyl-3-alkylimidazolium derived ionic salts with varying N-alkyl chains and different anions. These ionic salts were evaluated for their vermicidal activity (VA) and cell viability test against the Pheretima posthuma and A549 cell lines (human alveolar basal epithelial cells), respectively. The morphological changes in the test organism were visualized by the Scanning Electron Spectroscopy (SEM) to get the mechanistic insight. Furthermore, results were compared with VA of 1-methyl-3-alkylimidazolium derivatives to establish their structure-activity-relationship (SAR) of the fused benzene ring in 1-methyl-3-alkylimidazolium. The current findings suggested that the activity of these salts depends on the nature of N-alkyl side-chain, anionic moieties, varying partial charge on quaternary nitrogen (due to different anions) lipophilicity and types of cationic core fused with imidazolium ring. These findings were complemented by the quantitative-structure-activity-relationship (QSAR), molecular docking approaches to unfold the features accountable for their activities and binding patterns of the ligand-receptor complex respectively. ADME/T assessment of the ionic salts shows that twelve compounds qualified the ADMET profiling test & encompasses the drug-likeness features.
- Ranjan, Prabodh,Athar, Mohd,Vijayakrishna, Kari,Meena, Lalit K.,Vasita, Rajesh,Jha, Prakash C.
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p. 156 - 168
(2018/07/25)
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- Ru@PsIL-Catalyzed Synthesis of N-Formamides and Benzimidazole by using Carbon Dioxide and Dimethylamine Borane
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This work reports the synthesis and characterization of ruthenium nanoparticles (Ru NPs) supported on polymeric ionic liquids (PILs). This catalyst shows high catalytic activity towards the N-formylation of amines and synthesis of benzimidazoles from 1,2-diamines and carbon dioxide (CO2) by reductive dehydrogenation of dimethylamine borane. This methodology shows excellent functional group tolerance with broad substrate scope towards the synthesis of N-formamides and benzimidazoles. Interestingly, this protocol also provides the tandem reduction of 2-nitroamines and CO2 to synthesize benzimidazoles. It was proposed that the ionic liquid phase of the polymer plays pivotal roles such as assisting the stabilization of nanoparticles electrostatically, providing an ionic environment, and controlling the easy access of the substrates/reagents to the active sites. The developed methodology utilizes CO2 as a C1 source and water/ethanol as a green solvent system. Additionally, the catalyst was found to be recyclable in nature and shows five consecutive recycling runs without significant loss in its activity.
- Saptal, Vitthal B.,Sasaki, Takehiko,Bhanage, Bhalchandra M.
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p. 2593 - 2600
(2018/04/30)
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- A method for refining of the oil prepared benzo imidazoline corrosion inhibitor
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The invention relates to the technical field of metal corrosion inhibition and particularly discloses a benzimidazoline corrosion inhibitor prepared from refined swill-cooked dirty oil, of which the chemical formula is as shown in the description, wherein R=C(16-20) saturated alkyl or unsaturated alkyl; and R1=H, CH3 and C6H5. The corrosion inhibitor is obtained in the way that saturated alkyl and unsaturated alkyl or phenyl, of different chain lengths, are added into benzimidazole molecules, so that the hydrophobicity of a protective film is improved while the density of pi electron cloud, capable of being coordinated with metals, in the molecules is increased, accordingly, the metal corrosion rate is greatly reduced, and the metal anticorrosiveness is increased. The corrosion inhibitor is an oil-soluble product, can be used for corrosion protection of oil field pipelines and industrial pickling, can form a compact and firm adsorption film on a metal surface, reduces the metal corrosion rate and achieves the purpose of metal corrosion protection.
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-
Paragraph 0031; 0032
(2018/05/24)
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- B(C6F5)3: a robust catalyst for the activation of CO2 and dimethylamine borane for the N-formylation reactions
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In this work, B(C6F5)3 is utilized as an organocatalyst for the transition-metal-free N-formylation of amines using carbon dioxide (CO2) as a C1 source and dimethylamine borane (Me2NH·BH3) as a green hydrogen transfer source at 80 °C. Most reported works utilize silane and hydrogen for the N-formylation reactions using CO2 which have thus far been limited by low atom economy, high cost or the use of harsh reaction conditions. This catalytic protocol affords a broad range of formylated products in moderate to excellent yields under mild reaction conditions with a high TON and TOF. The bulky boron (B(C6F5)3) catalyst reacts with amines and forms a Frustrated Lewis Pair (FLP) and activates CO2 and Me2NH·BH3 molecules. Additionally, this boron catalyst shows high catalytic activity for the cyclization of o-phenylenediamines using CO2 and Me2NH·BH3 to synthesize benzimidazoles.
- Saptal, Vitthal B.,Juneja, Gaurav,Bhanage, Bhalchandra M.
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supporting information
p. 15847 - 15851
(2018/10/04)
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- Protection of Endogenous Thiols against Methylmercury with Benzimidazole-Based Thione by Unusual Ligand-Exchange Reactions
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Organomercurials, such as methylmercury (MeHg+), are among the most toxic materials to humans. Apart from inhibiting proteins, MeHg+ exerts its cytotoxicity through strong binding with endogenous thiols cysteine (CysH) and glutathione (GSH) to form MeHgCys and MeHgSG complexes. Herein, it is reported that the N,N-disubstituted benzimidazole-based thione 1 containing a N?CH2CH2OH substituent converts MeHgCys and MeHgSG complexes to less toxic water-soluble HgS nanoparticles (NPs) and releases the corresponding free thiols CysH and GSH from MeHgCys and MeHgSG, respectively, in solution by unusual ligand-exchange reactions in phosphate buffer at 37 °C. However, the corresponding N-substituted benzimidazole-based thione 7 and N,N-disubstituted imidazole-based thione 3, in spite of containing a N?CH2CH2OH substituent, failed to convert MeHgX (X=Cys, and SG) to HgS NPs under identical reaction conditions, which suggests that not only the N?CH2CH2OH moiety but the benzimidazole ring and N,N-disubstitution in 1, which leads to the generation of a partial positive charge at the C2 atom of the benzimidazole ring in 1:1 MeHg-conjugated complex of 1, are crucial to convert MeHgX to HgS NPs under physiologically relevant conditions.
- Banerjee, Mainak,Karri, Ramesh,Chalana, Ashish,Das, Ranajit,Rai, Rakesh Kumar,Rawat, Kuber Singh,Pathak, Biswarup,Roy, Gouriprasanna
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supporting information
p. 5696 - 5707
(2017/04/28)
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- [P,N]-phosphinobenzimidazole ligands in palladium-catalyzed C-N cross-coupling reactions: The effect of the N-substituent of the benzimidazole scaffold on catalyst performance
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A series of [P,N]-phosphinobenzimidazole ligands is reported in which the charge (anionic vs. neutral) and size of the N-substituent of the benzimidazole scaffold has been varied. In order to evaluate the impact of the substituent's properties on the performance of the metal in catalytic reactions, each ligand was screened for its ability to promote the cross-coupling of aryl bromides with various primary aryl amines using palladium as the metal source. In general, the ligands formed active cross-coupling catalysts with palladium. Moreover, the ligand variants containing larger N-substituents boosted the efficiency of the cross-coupling reaction considerably, while their charge (either anionic or neutral) appeared to have no significant impact.
- Tassone, Joseph P.,Spivak, Gregory J.
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supporting information
p. 57 - 61
(2017/05/10)
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- Selective C-H trifluoromethylation of benzimidazoles through photoredox catalysis
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The protocol presented here is a new strategy for visible light induced C-H trifluoromethylation at C4 of benzimidazoles using Togni's reagent in the presence of fac-Ir(ppy)3. Its advantages are its operational simplicity, mild reaction conditions, low catalyst loading and wide substrate scope in which electron-withdrawing, electron-donating groups and different protecting groups are tolerated.
- Gao, Guo-Lin,Yang, Chao,Xia, Wujiong
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supporting information
p. 1041 - 1044
(2017/02/05)
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- Atmospheric CO2 promoted synthesis of N-containing heterocycles over B(C6F5)3 catalyst
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B(C6F5)3 combined with atmospheric CO2 was found to be highly effective for the cyclization of ortho-substituted aniline derivatives with N,N-dimethylformamide (DMF), and a series of N-containing heterocycles including benzothiazoles, benzimidazoles, quinazolinone and benzoxazole were obtained in good to excellent yields.
- Gao, Xiang,Yu, Bo,Mei, Qingqing,Yang, Zhenzhen,Zhao, Yanfei,Zhang, Hongye,Hao, Leiduan,Liu, Zhimin
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p. 8282 - 8287
(2016/10/11)
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- Catalytic Oxidative Coupling of Primary Amines under Air: A Flexible Route to Benzimidazole Derivatives
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Benzimidazoles are of fundamental importance in chemistry and biology, and the development of efficient, environmentally benign methods for their preparation remains a key challenge for organic chemists. In a biomimetic approach inspired by copper amine oxidases, we disclose herein the scope and factors influencing the success of the cooperative action of CuBr2 as electron-transfer mediator and a topaquinone-like substrate-selective catalyst in the oxidative cyclocondensation of primary amines with o-aminoanilines. This one-pot atom-economic multistep process, which works under green conditions with ambient air as the terminal oxidant, low loadings of catalyst, and equimolar amounts of commercially available amine substrates, is particularly suitable for the preparation of 1,2-disubstituted benzimidazoles. Furthermore, it allows the functionalization of nonactivated primary aliphatic amines, which are known to be challenging substrates for non-enzymatic catalytic aerobic systems.
- Nguyen, Khac Minh Huy,Largeron, Martine
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p. 1025 - 1032
(2016/03/01)
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- Synthetic method of nitrogenous heterocyclic compound
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The invention discloses a synthetic method of a nitrogenous heterocyclic compound, comprising: dissolving o-nitro aromatic hydrocarbon in triethylamine-methane acid mixture, adding Pd/c catalyst, irradiating with microwave at 130-180 DEG C for 5-10 min, and reacting to obtain a corresponding nitrogenous heterocyclic compound; the o-nitro aromatic hydrocarbon is o-nitro benzoyl amine or o-nitro aminobenzene.The o-nitro aromatic hydrocarbon is used as a starting material, the material is converted in the triethylamine-methane acid azeotropic mixture under microwave irradiation into a product by means of palladium catalytic transfer hydrogenation reduction and cyclic condensation, the method is efficient, environment-friendly and applicable to diversified substrates, and no side reaction occurs during the generation of the product.The reaction product is extracted with an organic reagent to remove the catalyst in the reaction system, and the nitrogenous heterocyclic compound pure product is obtained by rotary evaporation; separation and purification by column chromatography is not required.
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-
Paragraph 0041; 0042; 0043
(2016/10/27)
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- CO2 as a C1 Source: B(C6F5)3-Catalyzed Cyclization of o-Phenylene-diamines To Construct Benzimidazoles in the Presence of Hydrosilane
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The catalytic construction of benzimidazoles using CO2 as a carbon source represents a facile and sustainable approach to obtaining these valuable compounds. Herein, we describe the B(C6F5)3-catalyzed synthesis of benzimidazoles via cyclization of o-phenylenediamines with CO2 and PhSiH3. This metal-free catalytic route achieves the desired products in high yield under convenient reaction conditions and is applicable to a broad substrate scope. A plausible mechanism for the reaction involving a frustrated Lewis pair pathway is proposed based on spectroscopic characterization (e.g., 13C NMR) of the reaction intermediates.
- Zhang, Zhenbei,Sun, Qiangsheng,Xia, Chungu,Sun, Wei
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supporting information
p. 6316 - 6319
(2016/12/23)
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