- Nickel-Catalyzed Direct Cross-Coupling of Aryl Sulfonium Salt with Aryl Bromide
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The direct cross-couplings of aryl sulfonium salts with aryl halides could be achieved by using nickel as a reaction catalyst. The reactions proceeded efficiently via C-S bond activation in the presence of magnesium turnings and lithium chloride in THF at ambient temperature to afford the corresponding biaryls in moderate to good yields, potentially serving as an attractive alternative to conventional cross-coupling reactions employing preprepared organometallic reagents.
- Ma, Na-Na,Ren, Jing-Ao,Liu, Xiang,Chu, Xue-Qiang,Rao, Weidong,Shen, Zhi-Liang
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p. 1953 - 1957
(2022/03/27)
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- Sterically enhanced 2-iminopyridylpalladium chlorides as recyclable ppm-palladium catalyst for Suzuki–Miyaura coupling in aqueous solution
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Sterically hindered 2-iminopyridine derivatives and their palladium chlorides complexes are designed and prepared, which efficiently promote the Suzuki–Miyaura coupling (SMC) reaction in aqueous solution. Besides the good to excellent yields and broad substrate scope, these catalysts can be reused for at least four new batches of the substrates. Spontaneous separation of coupling products in the aqueous reaction medium is the additional striking feature of this catalytic process. Furthermore, catalytic performance of palladium complexes bearing the azo-bridged phenyl groups was greatly influenced by the UV irradiation due to the cis/trans photoisomerization of azo unit of the catalysts. In conclusion, titled palladium complexes provide a green, sustainable, cost-effective, and convenient process to synthesize SMC products at multi-gram-scale reaction.
- Lin, Wenhua,Zhang, Liping,Ma, Yanping,Liang, Tongling,Sun, Wen-Hua
-
-
- Photocatalytic Reductive C-O Bond Cleavage of Alkyl Aryl Ethers by Using Carbazole Catalysts with Cesium Carbonate
-
Methods to activate the relatively stable ether C-O bonds and convert them to other functional groups are desirable. One-electron reduction of ethers is a potentially promising route to cleave the C-O bond. However, owing to the highly negative redox potential of alkyl aryl ethers (Ered -2.6 V vs SCE), this mode of ether C-O bond activation is challenging. Herein, we report the visible-light-induced photocatalytic cleavage of the alkyl aryl ether C-O bond using a carbazole-based organic photocatalyst (PC). Both benzylic and non-benzylic aryl ethers underwent C-O bond cleavage to form the corresponding phenol products. Addition of Cs2CO3 was beneficial, especially in reactions using a N-H carbazole PC. The reaction was proposed to occur via single-electron transfer (SET) from the excited-state carbazole to the substrate ether. Interaction of the N-H carbazole PC with Cs2CO3 via hydrogen bonding exists, which enables a deprotonation-assisted electron-transfer mechanism to operate. In addition, the Lewis acidic Cs cation interacts with the substrate alkyl aryl ether to activate it as an electron acceptor. The high reducing ability of the carbazole combined with the beneficial effects of Cs2CO3 made this otherwise formidable SET event possible.
- Yabuta, Tatsushi,Hayashi, Masahiko,Matsubara, Ryosuke
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p. 2545 - 2555
(2021/02/01)
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- Selective C-O Bond Reduction and Borylation of Aryl Ethers Catalyzed by a Rhodium-Aluminum Heterobimetallic Complex
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We report the catalytic reduction of a C-O bond and the borylation by a rhodium complex bearing an X-Type PAlP pincer ligand. We have revealed the reaction mechanism based on the characterization of the reaction intermediate and deuterium-labeling experiments. Notably, this novel catalytic system shows steric-hindrance-dependent chemoselectivity that is distinct from conventional Ni-based catalysts and suggests a new strategy for selective C-O bond activation by heterobimetallic catalysis.
- Hara, Naofumi,Nakao, Yoshiaki,Saito, Teruhiko,Seki, Rin
-
supporting information
p. 6388 - 6394
(2021/05/31)
-
- Biaryl compound as well as preparation method and application thereof
-
The invention discloses a biaryl compound as well as a preparation method and application thereof. The preparation method comprises the following steps: reacting magnesium chips and lithium chloride in a schlenk sealed tube to obtain a reactant 1, adding ultra-dry tetrahydrofuran into the sealed tube, extracting nitrogen from the sealed tube, then adding aryl quaternary ammonium salt, a 5mol% catalyst, aryl bromide and N, N, N' N'-tetramethyldisiloxane, stirring and reacting at 25-60 DEG C for 6-12 hours to obtain a reactant 2, and finally, sequentially carrying out extracting, washing, drying, extract liquor removing and purifying on the reactant 2 to obtain the biaryl compound which can be used for preparing a compound containing a biaryl structure. The preparation method is wide in substrate range, convenient to operate, mild in reaction condition, low in pollution and high in economic benefit, and the obtained biaryl compound has good functional group tolerance and substrate universality.
- -
-
Paragraph 0047-0055; 0057
(2021/09/21)
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- Confirmation of Suzuki-Miyaura Cross-Coupling Reaction Mechanism through Synthetic Architecture of Nanocatalysts
-
Despite widespread use of heterogeneous Pd catalysts in Suzuki-Miyaura coupling reactions, detailed roles of Pd, especially the nature of its active species, are still a topic of controversial debate. While some studies showed an active surface of Pd nanoparticles or nanoclusters acting heterogeneously, others claimed soluble Pd species leached from the metallic Pd to be active species which are homogeneous in nature. Besides, within the homogeneous mechanism, how the Pd leaches and promotes the cross-coupling reaction is then another question that needs to be addressed. It could be envisioned that if the soluble Pd species and solid-phase Pd are physically separated, the mechanism of Suzuki-Miyaura coupling could then be confirmed through examining the catalytic activity in different reaction regions. Herein we use microporous St?ber silica as a membrane to separate the soluble Pd species from solid Pd and conduct size-selective reactions which allow the passage of leaching Pd species, but not of reactants or products larger than the membrane aperture. With this strategy, we have been able to differentiate the surface reaction from the solution cross-coupling. We find that the leached Pd species are the only genuine catalytic intermediate in the cross-coupling reactions. We also confirm that oxidative addition of aryl halides to the solid Pd leads to leaching of the soluble Pd species which is necessary to promote Suzuki-Miyaura reactions.
- Sun, Bo,Ning, Lulu,Zeng, Hua Chun
-
supporting information
p. 13823 - 13832
(2020/09/21)
-
- Suzuki-Miyaura Cross-Coupling of Sulfoxides
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The utilization of diphenyl sulfoxides as versatile electrophilic coupling partners for the Suzuki-Miyaura reaction via C-S bond cleavage was successfully developed under palladium-N-heterocyclic carbene catalysis. The reactions showed good functional group compatibility, proceeded well under mild conditions, and provided biaryls in yields of up to 96%. A wide range of useful functional groups, such as fluoro, chloro, ether, hydroxyl, amide, cyano, keto, trimethylsilyl (TMS), and ester were tolerated under the reaction conditions; however, the use of phenylboronic anhydride and arylboronic acid pinacol esters generally would lead low yields. Good regioselectivity for the electron-poor phenyl group was achieved when unsymmetrical diphenyl sulfoxides were used. The protocol is applicable at the gram scale even with half the amount of catalyst. Density functional theory calculations were performed to investigate the reaction mechanism, indicating that the reaction occurred through oxidative addition, transmetalation, and reductive elimination to provide the final coupling product.
- Abduhulam, Hayrul,Cao, Changsheng,Chen, Qianwei,Dang, Yanfeng,Li, Chengxi,Shi, Yanhui,Wu, Shufeng,Yan, Shuqin
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p. 8168 - 8176
(2020/09/18)
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- Transition-Metal-Free C-C, C-O, and C-N Cross-Couplings Enabled by Light
-
Transition-metal-catalyzed cross-couplings to construct C-C, C-O, and C-N bonds have revolutionized chemical science. Despite great achievements, these metal catalysts also raise certain issues including their high cost, requirement of specialized ligands, sensitivity to air and moisture, and so-called "transition-metal-residue issue". Complementary strategy, which does not rely on the well-established oxidative addition, transmetalation, and reductive elimination mechanistic paradigm, would potentially eliminate all of these metal-related issues. Herein, we show that aryl triflates can be coupled with potassium aryl trifluoroborates, aliphatic alcohols, and nitriles without the assistance of metal catalysts empowered by photoenergy. Control experiments reveal that among all common aryl electrophiles only aryl triflates are competent in these couplings whereas aryl iodides and bromides cannot serve as the coupling partners. DFT calculation reveals that once converted to the aryl radical cation, aryl triflate would be more favorable to ipso substitution. Fluorescence spectroscopy and cyclic voltammetry investigations suggest that the interaction between excited acetone and aryl triflate is essential to these couplings. The results in this report are anticipated to provide new opportunities to perform cross-couplings.
- Liu, Wenbo,Li, Jianbin,Querard, Pierre,Li, Chao-Jun
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p. 6755 - 6764
(2019/05/06)
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- Cross-Coupling of Chloro(hetero)arenes with Thiolates Employing a Ni(0)-Precatalyst
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A general and efficient Ni-catalyzed coupling of challenging aryl chlorides and in situ generated aliphatic and aromatic thiolates is described. The employed on-cycle, air-stable defined Ni precatalysts allow for transformation of a broad scope of substrates. A variety of functional groups and heterocyclic motifs as well as structurally varied thiols are tolerated at unprecedented moderate catalyst loadings and reaction temperatures. Depending on reaction conditions, aryl thiols can selectively undergo C-S or C-C couplings.
- Gehrtz, Paul H.,Geiger, Valentin,Schmidt, Tanno,Sr?an, Laura,Fleischer, Ivana
-
supporting information
p. 50 - 55
(2019/01/11)
-
- Palladium-catalyzed cross-coupling of aryl chlorides with O, N-chelate stabilized diarylborinates
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A series of O, N-chelated diarylborinates have been prepared and tested as arylboron counterpart alternative to oxygen-labile diarylborinic acids in palladium catalyzed Suzuki coupling of aryl chlorides. 3-Dimethylaminopropyl diarylborinates (B-5a), featuring a six-membered O, N-chelated boron ring that was confirmed by single crystal X-ray diffraction, displayed a delicately balanced stability and reactivity. Their cross-coupling with structurally various aryl chlorides could be effected as efficiently as that of the parent diarylborinic acids by using 0.1~1mol% Pd(OAc)2/IPr/P(OPh)3 as catalyst system, to provide the corresponding biaryls in good to excellent yields.
- Zhang, Nan,Wang, Chen,Zou, Gang,Tang, Jie
-
supporting information
p. 54 - 58
(2017/05/15)
-
- Exploring the Reactivity of α-Lithiated Aryl Benzyl Ethers: Inhibition of the [1,2]-Wittig Rearrangement and the Mechanistic Proposal Revisited
-
By carefully controlling the reaction temperature, treatment of aryl benzyl ethers with tBuLi selectively leads to α-lithiation, generating stable organolithiums that can be directly trapped with a variety of selected electrophiles, before they can undergo the expected [1,2]-Wittig rearrangement. This rearrangement has been deeply studied, both experimentally and computationally, with aryl α-lithiated benzyl ethers bearing different substituents at the aryl ring. The obtained results support the competence of a concerted anionic intramolecular addition/elimination sequence and a radical dissociation/recombination sequence for explaining the tendency of migration for aryl groups. The more favored rearrangements are found for substrates with electron-poor aryl groups that favor the anionic pathway.
- Velasco, Rocío,Silva López, Carlos,Nieto Faza, Olalla,Sanz, Roberto
-
supporting information
p. 15058 - 15068
(2016/10/11)
-
- Mesolysis Processes with Benzylic Carbon?Oxygen Bond Cleavage in Radical Anions of Aryl Benzyl Ethers Studied by Electron Pulse Radiolysis in DMF
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Based on transient absorption measurements obtained upon electron-pulse radiolysis of aromatic ethers in N,N-dimethylformamide (DMF), mesolysis processes of the radical anions were investigated. We observed transient absorption spectral change due to the
- Yamaji, Minoru,Tojo, Sachiko,Fujitsuka, Mamoru,Sugimoto, Akira,Majima, Tetsuro
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p. 798 - 803
(2016/08/02)
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- Pd-catalyzed Suzuki–Miyaura cross-coupling of [Ph2SR][OTf] with arylboronic acids
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The Pd-catalyzed Suzuki–Miyaura cross-coupling of alkyl- and fluoroalkyl(diphenyl)sulfonium triflates with arylboronic acids was compared. The fluorine substitution on the alkyl groups of [Ph2SR][OTf] had a big influence on the reaction. Perfluoroalkyl(diphenyl)sulfonium triflates (2b–d) were unsuccessful participants in the Pd-catalyzed phenylation of arylboronic acid under the standard conditions because of the strong electronegativity of the long-chain perfluoroalkyl groups, which underwent S[sbnd]Rfnbond cleavage instead. Polyfluoroalkyl(diphenyl)sulfonium triflates (2f–h) reacted with arylboronic acid to afford the phenylation product in very low yields due to the tendency of deprotonation and β-F elimination of the sulfonium salts. Eventually, (2,2,2-trifluoroethyl)diphenylsulfonium triflate (2e), methyl- or ethyl(diphenyl)sulfonium triflate (2i or 2j), and triphenylsulfonium triflate (2m) were found to be more effective reagents than other tested phenylsulfounium salts for Pd-catalyzed phenylation, which provided much higher yields of the desired products under mild conditions.
- Wang, Xiao-Yan,Song, Hai-Xia,Wang, Shi-Meng,Yang, Jing,Qin, Hua-Li,Jiang, Xin,Zhang, Cheng-Pan
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p. 7606 - 7612
(2016/11/11)
-
- In situ generated and stabilized Pd nanoparticles by N2,N4,N6-tridodecyl-1,3,5-triazine-2,4,6-triamine (TDTAT) as a reactive and efficient catalyst for the Suzuki-Miyaura reaction in water
-
In situ generated Pd nanoparticles in the presence of N2,N4,N6-tridodecyl-1,3,5-triazine-2,4,6-triamine (TDTAT) were found to be an efficient catalyst for the Suzuki-Miyaura coupling reaction in water. It seems that TDTAT not only acts as a ligand for stabilization of the produced nanoparticles, but also as a surfactant to facilate the reaction in water, and reduces Pd(ii) to Pd(0). The TEM analysis of the reaction mixture showed that Pd nanoparticles with an average size of ~5 nm are produced, which act as an efficient catalyst in the Suzuki-Miyaura coupling reaction.
- Iranpoor, Nasser,Rahimi, Sajjad,Panahi, Farhad
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p. 3084 - 3090
(2016/01/16)
-
- A green approach for the decoration of Pd nanoparticles on graphene nanosheets: An in situ process for the reduction of C-C double bonds and a reusable catalyst for the Suzuki cross-coupling reaction
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A new strategy for in situ synthesis of palladium nanoparticles (Pd NPs) decorated on reduced graphene oxide (rGO) nanosheets with controlled size and shape is reported. This strategy was designed as three processes in one pot, namely, (a) reduction of graphene oxide, (b) formation of Pd NPs on the rGO nanosheets and (c) simultaneous reduction of olefin. In this synthesis process, a hydrogen atmosphere was used to develop the Pd NPs-rGO nanocatalyst, which is reusable and easily separable. The influence of the size and morphology of the Pd-rGO-H2 catalyst on the catalytic activity in the Suzuki cross-coupling reaction was investigated by comparing with other catalysts, Pd-rGO-As and Pd-rGO-Gl, and they were synthesized by different reducing agents, ascorbic acid and glucose, respectively. The catalysts were characterized by electron microscopy (HRTEM, SEM), FT-IR, XRD and XPS. The Pd-rGO-H2 catalyst was found to possess excellent catalytic activity and recyclability in the Suzuki cross-coupling reaction under mild reaction conditions.
- Hussain, Najrul,Borah, Ashwini,Darabdhara, Gitashree,Gogoi, Pranjal,Azhagan, Vedi Kuyil,Shelke, Manjusha V.,Das, Manash R.
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p. 6631 - 6641
(2015/08/06)
-
- Nickel-catalyzed cross-coupling of diarylborinic acids with aryl chlorides
-
A highly efficient nickel/triarylphosphine catalyst system, Ni[P(4-MeOPh)3]2Cl2/2P(4-MeOPh)3, has been developed for cross-coupling of diarylborinic acids with a wide range of aryl chlorides. A variety of unsymmetrical biaryl and heterobiaryl compounds with various functional groups and steric hindrance could be obtained in good to excellent yields using 0.5-2 mol % catalyst loadings in the presence of K 3PO4·3H2O in toluene. The high atom economy of diarylborinic acids and cost-effectiveness of the nickel/phosphine catalyst system make the cross-coupling truly practical in the production of biaryl fine chemicals. Usefulness of the nickel/phosphine catalyzed cross-coupling of diarylborinic acids with aryl chlorides has been demonstrated in the development of a scalable and economical process for synthesis of 4′-methyl-2-cyanobiphenyl, Sartan biphenyl.
- Chen, Xiaofeng,Ke, Haihua,Zou, Gang
-
p. 379 - 385
(2014/03/21)
-
- Tandem C-H activation/arylation catalyzed by low-valent iron complexes with bisiminopyridine ligands
-
Tandem C-H activation/arylation between unactivated arenes and aryl halides catalyzed by iron complexes that bear redox-active non-innocent bisiminopyridine ligands is reported. Similar reactions catalyzed by first-row transition metals have been shown to involve substrate-based aryl radicals, whereas our catalytic system likely involves ligand-centered radicals. Preliminary mechanistic investigations based on spectroscopic and reactivity studies, in conjunction with DFT calculations, led us to propose that the reaction could proceed through an inner-sphere C-H activation pathway, which is rarely observed in the case of iron complexes. This bielectronic noble-metal-like behavior could be sustained by the redox-active non-innocent bisiminopyridine ligands. A radical choice! A low-valent iron complex with non-innocent bisiminopyridine ligands performs C-H activation/arylation of unactivated aryl compounds (see figure). The reaction likely involves ligand-based radicals, whereas previously reported iron-based systems imply substrate-based radicals.
- Salanouve, Elise,Bouzemame, Ghania,Blanchard, Sebastien,Derat, Etienne,Desage-El Murr, Marine,Fensterbank, Louis
-
supporting information
p. 4754 - 4761
(2014/05/06)
-
- N-heterocyclic carbene-assisted, Bis(phosphine)nickel-catalyzed cross-couplings of diarylborinic acids with aryl chlorides, tosylates, and sulfamates
-
Efficient bis(phosphine)nickel-catalyzed cross-couplings of diarylborinic acids with aryl chlorides, tosylates, and sulfamates have been effected with an assistance of N-heterocyclic carbene (NHC) generated in situ from N,N′-dialkylimidazoliums, e.g., N-butyl-N′-methylimidazolium bromide ([Bmim]Br), in toluene using K3PO4·3H2O as base. In contrast to bis(NHC)nickel-catalyzed conventional Suzuki coupling of arylboronic acids, mono(NHC)bis(phosphine)nickel species generated in situ from Ni(PPh3)2Cl2/[Bmim]Br displayed high catalytic activities in the cross-couplings of diarylborinic acids. The structural influences from diarylborinic acids were found to be rather small, while electronic factors from aryl chlorides, tosylates, and sulfamates affected the couplings remarkably. The couplings of electronically activated aryl chlorides, tosylates, and sulfamates could be efficiently effected with 1.5 mol % NiCl2(PPh3)2/[Bmim]Br as catalyst precursor to give the biaryl products in excellent yields, while 3-5 mol % loadings had to be used for the couplings of non- and deactivated ones. A small ortho-substitutent on the aromatic ring of aryl chlorides, tosylates, and sulfamates was tolerable. Applicability of the nickel-catalyzed cross-couplings in practical synthesis of fine chemicals has been demonstrated in process development for a third-generation topical retinoid, Adapalene.
- Ke, Haihua,Chen, Xiaofeng,Zou, Gang
-
p. 7132 - 7140
(2014/08/18)
-
- Vasicine catalyzed direct C-H arylation of unactivated arenes: Organocatalytic application of an abundant alkaloid
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Vasicine, a quinazoline alkaloid isolated from Adhatoda vasica, has been employed as an organocatalyst for direct C-H arylation of unactivated arenes with aryl iodides/bromides without the assistance of any transition metal catalyst. A number of sensitive functional groups such as methyl, methoxy, O-benzyl, acetyl, and amino were well tolerated under present reaction conditions. Mechanistic investigation supported the involvement of radical intermediates.
- Sharma, Sushila,Kumar, Manoranjan,Kumar, Vishal,Kumar, Neeraj
-
supporting information
p. 4868 - 4871
(2013/08/28)
-
- PVC-supported palladium nanoparticles: An efficient catalyst for suzuki cross-coupling reactions at room temperature
-
A simple and efficient protocol is described for a Suzuki reaction catalyzed by poly(vinyl chloride)-supported nanoparticles of metallic palladium at room temperature. Aryl iodides, bromides, and chlorides underwent smooth Suzuki reactions in aqueous ethanol, an environmentally friendly solvent, under ligand-free conditions to give good yields of the desired biaryl products. The heterogeneous catalyst could be used up to four times with no detectable metal leaching or loss of catalytic efficiency. Georg Thieme Verlag Stuttgart.New York.
- Samarasimhareddy, Mamidi,Prabhu, Girish,Vishwanatha, Thimmalapura M.,Sureshbabu, Vommina V.
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p. 1201 - 1206
(2013/06/05)
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- A novel acid-catalyzed O-benzylating reagent with the smallest unit of imidate structure
-
Formal trimerization of the smallest unit of benzyl imidate leads to 2,4,6-tris(benzyloxy)-1,3,5-triazine (TriBOT), which can be used as an acid-catalyzed O-benzylating reagent. The reaction of various functionalized alcohols with 0.4 equiv of TriBOT in the presence of trifluoromethanesulfonic acid afforded the benzyl ethers in good yields. TriBOT is an inexpensive stable crystalline solid with high atom economy.
- Yamada, Kohei,Fujita, Hikaru,Kunishima, Munetaka
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p. 5026 - 5029,4
(2012/12/12)
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- A novel acid-catalyzed O-benzylating reagent with the smallest unit of imidate structure
-
Formal trimerization of the smallest unit of benzyl imidate leads to 2,4,6-tris(benzyloxy)-1,3,5-triazine (TriBOT), which can be used as an acid-catalyzed O-benzylating reagent. The reaction of various functionalized alcohols with 0.4 equiv of TriBOT in the presence of trifluoromethanesulfonic acid afforded the benzyl ethers in good yields. TriBOT is an inexpensive stable crystalline solid with high atom economy.
- Yamada, Kohei,Fujita, Hikaru,Kunishima, Munetaka
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p. 5026 - 5029
(2013/01/15)
-
- Cross-coupling of diarylborinic acids and anhydrides with arylhalides catalyzed by a phosphite/N-heterocyclic carbene co-supported palladium catalyst system
-
A highly efficient cross-coupling of diarylborinic acids and anhydrides with aryl chlorides and bromides has been effected by using a palladium catalyst system co-supported by a strong σ-donor N-heterocyclic carbene (NHC), N,N′-bis(2,6-diisopropylphenyl) imidazol-2-ylidene, and a strong π-acceptor phosphite, triphenylphosphite, in tert-BuOH in the present of K3PO4·3H2O. Unsymmetrical biaryls with a variety of functional groups could be obtained in good to excellent yields using as low as 0.01, 0.2-0.5, and 1 mol % palladium loadings for aryl bromides and activated and deactivated aryl chlorides, respectively, under mild conditions. A ligand synergy between the σ-donor NHC and the π-acceptor phosphite in the Pd/NHC/P(OPh)3 catalytic system has been proposed to be responsible for the high efficacy to arylchlorides in the cross-coupling. A scalable and economical process has therefore been developed for synthesis of Sartan biphenyl from the Pd/NHC/P(OPh)3 catalyzed cross-coupling of di(4-methylphenyl)borinic acid with 2-chlorobenzonitrile.
- Chen, Xiaofeng,Ke, Haihua,Chen, Yao,Guan, Changwei,Zou, Gang
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p. 7572 - 7578
(2012/10/29)
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- Microwave-assisted benzyl-transfer reactions of commercially available 2-benzyloxy-1-methylpyridinium triflate
-
Benzylation of alcohols and other substrates under thermal conditions translates smoothly from conventional heating into MW-assisted organic synthesis (MAOS). Reactions times are decreased from hours to minutes while good to excellent yields are maintained. MW heating should be considered for benzylation of high-value substrates using the title reagent.
- Wang, Teng-Wei,Intaranukulkit, Tanit,Rosana, Michael R.,Slegeris, Rimantas,Simon, Janet,Dudley, Gregory B.
-
supporting information; experimental part
p. 248 - 250
(2012/02/04)
-
- New reagents for the synthesis of arylmethyl ethers and esters
-
This Account chronicles efforts leading up to the development of new arylmethyl transfer (benzylation) reagents for protecting oxygen functional groups under relatively mild and neutral conditions. It begins with an investigation of organosiletanes as surrogate hydroxyl groups, which inspired siletane-functionalized benzyl ethers and forced us to confront the difficulties associated with the synthesis of benzyl ethers. The end result is a new series of neutral oxypyridinium salts for the benzylation of various nucleophilic functional groups under mild conditions. 1 Introduction 2 Tamao-type Oxidation of Strained Organosiletanes 3 p-Siletanylbenzyl (PSB) Protecting Groups 4 2-Benzyloxy-1-methylpyridinium Triflate 5 Friedel-Crafts Reactions and Mechanistic Insights 6 Benzyl Ester Formation 7 Substituted Benzyl Transfer Reagents 8 Conclusions and Outlook. Georg Thieme Verlag Stuttgart New York.
- Albiniak, Philip A.,Dudley, Gregory B.
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scheme or table
p. 841 - 851
(2010/07/10)
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- Compounds and methods of arylmethylation (benzylation) as protection for alcohol groups during chemical synthesis
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A process for benzylating an alcohol includes mixing 2-benzyloxy-1-methylpyridinium triflate in an aromatic hydrocarbon solvent having a predetermined boiling point; adding an acid scavenger to the mixture; combining the alcohol to be benzylated with the mixture; reacting the alcohol with the 2-benzyloxy-1-methylpyridinium triflate by heating above ambient temperature to generate the benzylated alcohol; and separating the benzylated alcohol from the mixture.
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-
Page/Page column 15; 16
(2010/07/14)
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- Facile cleavage of ethers in ionic liquid
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Various alkyl ethers were efficiently cleaved by treating them with pyridinium halides in ionic liquid, and the desired products were obtained in excellent yields.
- Cheng, Lili,Aw, Carlin,Ong, Siew Siang,Lu, Yixin
-
supporting information; experimental part
p. 2008 - 2010
(2009/08/14)
-
- Light-fluorous safety-catch arylgermanes - Exceptionally robust, photochemically activated precursors for biaryl synthesis by Pd(0) catalysed cross-coupling
-
A new class of arylgermane derivative that participate efficiently in Pd(0)-catalysed cross-coupling reactions with aryl bromides following photochemical activation is described. The Royal Society of Chemistry.
- Spivey, Alan C.,Tseng, Chih-Chung,Hannah, Joseph P.,Gripton, Christopher J. G.,De Fraine, Paul,Parr, Nigel J.,Scicinski, Jan J.
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p. 2926 - 2928
(2008/03/11)
-
- Mix-and-heat benzylation of alcohols using a bench-stable pyridinium salt
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2-Benzyloxy-1-methylpyridinium inflate (1) is a stable, neutral organic salt that converts alcohols into benzyl ethers upon warming. The synthesis and reactivity of 1 are described herein. Benzylation of a wide range of alcohols occurs in good to excellent yield.
- Poon, Kevin W. C.,Dudley, Gregory B.
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p. 3923 - 3927
(2007/10/03)
-
- A bench-stable organic salt for the benzylation of alcohols
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2-Benzyloxy-1-methylpyridinium inflate (Bn-OPT) effects the benzylation of alcohols in the absence of acidic or basic promoters. Solutions of Bn-OPT and primary, secondary, or tertiary alcohols give rise to the corresponding benzyl ethers upon mild heating. Acid scavengers are generally included in the reaction mixture. Bn-OPT is crystalline and bench-stable. Georg Thieme Verlag Stuttgart.
- Poon, Kevin W. C.,House, Sarah E.,Dudley, Gregory B.
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p. 3142 - 3144
(2007/10/03)
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- NiCl2(dppe)-Catalyzed Cross-Coupling of Aryl Mesylates, Arenesulfonates, and Halides with Arylboronic Acids
-
An investigation of the NiCl2(dppe)-, NiCl2(dppb)-, NiCl2(dppf)-, NiCl2(PCy3)2-, and NiCl2(PPh3)2- catalyzed cross-coupling of the previously unreported aryl mesylates, and of aryl arenesulfonates, chlorides, bromides, and iodides containing electron-withdrawing and electron-donating substituents with aryl boronic acids, in the absence of a reducing agent, is reported. NiCl2(dppe) was the only catalyst that exhibited high and solvent-independent activity in the two solvents investigated, toluene and dioxane. NiCl2(dppe) with an excess of dppe, NiCl 2(dppe)/dppe, was reactive in the cross-coupling of electron-poor aryl mesylates, tosylates, chlorides, bromides, and iodides. This catalyst was also efficient in the cross-coupling of aryl bromides and iodides containing electron-donating substituents. Most surprisingly, the replacement of the excess dppe from NiCl2(dppe)/dppe with excess PPh3 generated NiCl2(dppe)/PPh3, which was found to be reactive for the cross-coupling of both electron-rich and electron-poor aryl mesylates and chlorides. Therefore, the solvent-independent reactivity of NiCl2(dppe) provides an inexpensive and general nickel catalyst for the cross-coupling of aryl mesylates, tosylates, chlorides, bromides, and iodides with aryl boronic acids.
- Percec, Virgil,Golding, Geoffrey M.,Smidrkal, Jan,Weichold, Oliver
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p. 3447 - 3452
(2007/10/03)
-
- Improved Cs2CO3 promoted O-alkylation of phenols
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Cesium carbonate mediated O-alkylation of phenols was carried out under mild conditions to give the corresponding phenol ethers exclusively. The methodology is more efficient than previous methods since harsh conditions such as higher temperatures and lon
- Parrish, Jay P.,Sudaresan, Bhuvana,Jung, Kyung Woon
-
p. 4423 - 4431
(2007/10/03)
-