- Cascade Reductive Friedel-Crafts Alkylation Catalyzed by Robust Iridium(III) Hydride Complexes Containing a Protic Triazolylidene Ligand
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The synthesis of complex molecules like active pharmaceutical ingredients typically requires multiple single-step reactions, in series or in a modular fashion, with laborious purification and potentially unstable intermediates. Cascade processes offer attractive synthetic remediation as they reduce time, energy, and waste associated with multistep syntheses. For example, triarylmethanes are traditionally prepared via several synthetic steps, and only a handful of cascade routes are known with limitations due to high catalyst loadings. Here, we present an expedient catalytic cascade process to produce triarylmethanes. For this purpose, we have developed a bifunctional iridium system as the efficient catalyst to build heterotriaryl synthons via reductive Friedel-Crafts alkylation from ketones, arenes, and hydrogen. The catalytically active species were generated in situ from a robust triazolyl iridium(III) hydride complex and acid and is composed of a metal-bound hydride and a proximal ligand-bound proton for reversible dihydrogen release. These complexes catalyze the direct hydrogenation of ketones at slow rates followed by dehydration. Appropriate adjustment of the conditions successfully intercepts this dehydration and leads instead to efficient C-C coupling and Friedel-Crafts alkylation. The scope of this cascade process includes a variety of carbonyl substrates such as aldehydes, (alkyl)(aryl)ketones, and diaryl ketones as precursor electrophiles with arenes and heteroarenes for Friedel-Crafts coupling. The reported method has been validated in a swift one-step synthesis of the core structure of a potent antibacterial agent. Excellent yields and exquisite selectivities were achieved for this cascade process with unprecedentedly low iridium loadings (0.02 mol %). Moreover, the catalytic activity of the protic system is significantly higher than that of an N-methylated analogue, confirming the benefit of the Ir-H/N-H hydride-proton system for high catalytic performance.
- Albrecht, Martin,Alshakova, Iryna D.
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p. 8999 - 9007
(2021/07/31)
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- Reductive activation and hydrofunctionalization of olefins by multiphoton tandem photoredox catalysis
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The conversion of olefin feedstocks to architecturally complex alkanes represents an important strategy in the expedient generation of valuable molecules for the chemical and life sciences. Synthetic approaches are reliant on the electrophilic activation of unactivated olefins, necessitating functionalization with nucleophiles. However, the reductive functionalization of unactivated and less activated olefins with electrophiles remains an ongoing challenge in synthetic chemistry. Here, we report the nucleophilic activation of inert styrenes through a photoinduced direct single electron reduction to the corresponding nucleophilic radical anion. Central to this approach is the multiphoton tandem photoredox cycle of the iridium photocatalyst [Ir(ppy)2(dtbbpy)] PF6, which triggers in situ formation of a high-energy photoreductant that selectively reduces styrene olefinic π bonds to radical anions without stoichiometric reductants or dissolving metals. This mild strategy enables the chemoselective reduction and hydrofunctionalization of styrenes to furnish valuable alkane and tertiary alcohol derivatives. Mechanistic studies support the formation of a styrene olefinic radical anion intermediate and a Birch-type reduction involving two sequential single electron transfers. Overall, this complementary mode of olefin activation achieves the hydrofunctionalization of less activated alkenes with electrophiles, adding value to abundant olefins as valuable building blocks in modern synthetic protocols.
- Czyz, Milena L.,Taylor, Mitchell S.,Horngren, Tyra H.,Polyzos, Anastasios
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p. 5472 - 5480
(2021/06/01)
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- Nickel-Catalyzed Electrochemical Reductive Relay Cross-Coupling of Alkyl Halides to Aryl Halides
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A highly regioselective Ni-catalyzed electrochemical reductive relay cross-coupling between an aryl halide and an alkyl halide has been developed in an undivided cell. Various functional groups are tolerated under these mild reaction conditions, which pro
- Fang, Ping,Jiao, Ke-Jin,Liu, Dong,Ma, Hong-Xing,Mei, Tian-Sheng,Qiu, Hui
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supporting information
p. 6520 - 6524
(2020/01/24)
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- Bisoxazoline-pincer ligated cobalt-catalyzed hydrogenation of alkenes
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The efficient and atom economical hydrogenation of alkenes using a novel bisoxazoline ligated cobalt complex has been developed. The hydrogenation of a variety of alkenes containing electron neutral and electron-donating groups proceeds in high yield, whi
- Ritz, Mikhaila D.,Parsons, Astrid M.,Palermo, Philip N.,Jones, William D.
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- Iron-catalysed enantioconvergent Suzuki-Miyaura cross-coupling to afford enantioenriched 1,1-diarylalkanes
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The first stereoconvergent Suzuki-Miyaura cross-coupling reaction was developed to afford enantioenriched 1,1-diarylalkanes. An iron-based complex containing a chiral cyanobis(oxazoline) ligand framework was best to obtain enantioenriched 1,1-diarylalkanes from cross-coupling reactions between unactivated aryl boronic esters and benzylic chlorides. Enhanced yields were obtained when 1,3,5-trimethoxybenzene was used as an additive, which is hypothesized to extend the lifetime of the iron-based catalyst. Exceptional enantioselectivities were obtained with challenging ortho-substituted benzylic chlorides. This journal is
- Tyrol, Chet C.,Yone, Nang S.,Gallin, Connor F.,Byers, Jeffery A.
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p. 14661 - 14664
(2020/12/02)
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- Teaching an old carbocation new tricks: Intermolecular C-H insertion reactions of vinyl cations
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Vinyl carbocations have been the subject of extensive experimental and theoretical studies over the past five decades. Despite this long history in chemistry, the utility of vinyl cations in chemical synthesis has been limited, with most reactivity studies focusing on solvolysis reactions or intramolecular processes. Here we report synthetic and mechanistic studies of vinyl cations generated through silylium-weakly coordinating anion catalysis. We find that these reactive intermediates undergo mild intermolecular carbon-carbon bond-forming reactions, including carbon-hydrogen (C-H) insertion into unactivated sp3 C-H bonds and reductive Friedel-Crafts reactions with arenes. Moreover, we conducted computational studies of these alkane C-H functionalization reactions and discovered that they proceed through nonclassical, ambimodal transition structures. This reaction manifold provides a framework for the catalytic functionalization of hydrocarbons using simple ketone derivatives.
- Popov, Stasik,Shao, Brian,Bagdasarian, Alex L.,Benton, Tyler R.,Zou, Luyi,Yang, Zhongyue,Houk,Nelson, Hosea M.
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p. 381 - 387
(2018/08/07)
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- Synthesis of 1,1′-diarylethanes and related systems by displacement of trichloroacetimidates with trimethylaluminum
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Benzylic trichloroacetimidates are readily displaced by trimethylaluminum under Lewis acid promoted conditions to provide the corresponding methyl substitution product. This method is a convenient way to access 1,1′-diarylethanes and related systems, which play a significant role in medicinal chemistry, with a number of systems owing their biological activity to this functionality. Most benzylic substrates undergo ready displacement, with electron deficient systems being the exception. The use of an enantiopure imidate showed significant racemization, implicating the formation of a cationic intermediate.
- Mahajani, Nivedita S.,Chisholm, John D.
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p. 4131 - 4139
(2018/04/14)
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- Nickel(0)-Catalyzed Hydroarylation of Styrenes and 1,3-Dienes with Organoboron Compounds
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A Ni-catalyzed hydroarylation of styrenes and 1,3-dienes with organoboron compounds has been developed. The reaction offers a highly selective approach to diarylalkanes and allylarenes under redox-neutral conditions. In this hydroarylation reaction, a new strategy that uses the proton of methanol to generate the active catalyst species Ni?H was developed. The Ni-catalyzed hydroarylation, combined with a Ir-catalyzed C?H borylation, affords a very efficient and straightforward access to a retinoic acid receptor agonist.
- Xiao, Li-Jun,Cheng, Lei,Feng, Wei-Min,Li, Mao-Lin,Xie, Jian-Hua,Zhou, Qi-Lin
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supporting information
p. 461 - 464
(2018/02/21)
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- Feedstocks to Pharmacophores: Cu-Catalyzed Oxidative Arylation of Inexpensive Alkylarenes Enabling Direct Access to Diarylalkanes
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A Cu-catalyzed method has been identified for selective oxidative arylation of benzylic C-H bonds with arylboronic esters. The resulting 1,1-diarylalkanes are accessed directly from inexpensive alkylarenes containing primary and secondary benzylic C-H bonds, such as toluene or ethylbenzene. All catalyst components are commercially available at low cost, and the arylboronic esters are either commercially available or easily accessible from the commercially available boronic acids. The potential utility of these methods in medicinal chemistry applications is highlighted.
- Vasilopoulos, Aristidis,Zultanski, Susan L.,Stahl, Shannon S.
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p. 7705 - 7708
(2017/06/20)
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- Synthesis and catalytic reactivity of mononuclear substituted tetramethylcyclopentadienyl molybdenum carbonyl complexes
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The reactions of five dinuclear carbonyl complexes [(η 5-C5Me4R)Mo(CO)3]2 [R = allyl, n Bu, t Bu, Ph, Bz] with I2 in chloroform solution gave the corresponding mononuclear substituted tetramethylcyclopentadienyl molybdenum carbonyl complexes [(η 5-C5Me4R)MoI(CO)3] [R = allyl (1), n Bu (2), t Bu (3), Ph (4), Bz (5)]. The molecular structures of complexes 2, 3 and 5 were determined by X-ray diffraction analysis. The results show that the substituent in the ring can directly affect the Mo-I bond distances; the more sterically hindered the substituent, the longer the Mo-I bond. Friedel-Crafts reactions of aromatic compounds with a variety of alkylation reagents catalyzed by the complexes showed that all of these mononuclear molybdenum carbonyl complexes have catalytic activity in Friedel-Crafts alkylation reactions. Indeed, compared with traditional catalysts, these mononuclear metal carbonyl complexes have obvious advantages such as higher activities, mild reaction conditions, high selectivity, simple post-processing, and environmentally friendly chemistry.
- Ma, Zhi-Hong,Lv, Lin-Qian,Wang, Hong,Han, Zhan-Gang,Zheng, Xue-Zhong,Lin, Jin
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p. 225 - 233
(2016/02/20)
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- Benzylic Phosphates in Friedel-Crafts Reactions with Activated and Unactivated Arenes: Access to Polyarylated Alkanes
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Easily reachable electron-poor/rich primary and secondary benzylic phosphates are suitably used as substrates for Friedel-Crafts benzylation reactions with only 1.2 equiv activated/deactivated arenes (no additional solvent) to access structurally and electronically diverse polyarylated alkanes with excellent yields and selectivities at room temperature. Specifically, diversely substituted di/triarylmethanes are generated within 2-30 min using this approach. A wide number of electron-poor polyarylated alkanes are easily accomplished through this route by just tuning the phosphates.
- Pallikonda, Gangaram,Chakravarty, Manab
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p. 2135 - 2142
(2016/03/15)
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- A surprising substituent effect provides a superior boronic acid catalyst for mild and metal-free direct Friedel-Crafts alkylations and prenylations of neutral arenes
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The development of more general and efficient catalytic processes for Friedel-Crafts alkylations is an important objective of interest toward the production of pharmaceuticals and commodity chemicals. Herein, 2,3,4,5-tetrafluorophenylboronic acid was identified as a potent air- and moisture-tolerant metal-free catalyst that significantly improves the scope of direct Friedel-Crafts alkylations of a variety of slightly activated and neutral arenes, including polyarenes, with allylic and benzylic alcohols. This method also provides a simple alternative for the direct installation of prenyl units commonly found in naturally occurring arenes. Alkylations with benzylic alcohols occur under exceptionally mild conditions.
- Ricardo, Carolynne L.,Mo, Xiaobin,McCubbin, J. Adam,Hall, Dennis G.
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supporting information
p. 4218 - 4223
(2015/03/14)
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- Benzylation of arenes with benzyl halides synergistically promoted by in situ generated superacid boron trifluoride monohydrate and tetrahaloboric acid
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To examine the assembly methodology of diarylmethanes, a benzylation of (hetero)arenes with benzyl halides has been developed and various diarylmethanes were furnished with yields of up to 98% and regioselectivities of up to >99%. The complexation of the by-product halogen hydride with BF3·OEt2 generated the Bronsted acid BF3·HX (HBF3X, X=Cl or Br) in situ to synergistically promote the benzylation.
- Huang, Ruofeng,Zhang, Xiaohui,Pan, Jing,Li, Jiaqiang,Shen, Hang,Ling, Xuege,Xiong, Yan
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supporting information
p. 1540 - 1546
(2015/03/04)
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- Superacid BF3-H2O promoted benzylation of arenes with benzyl alcohols and acetates initiated by trace water
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A convenient procedure employing simple starting materials benzyl alcohols and acetates as the benzyl donors to assemble a series of diarylalkanes through benzylation of arenes using in situ prepared superacid BF3-H 2O as an efficient promoter has been developed. The beneficial role of water in the reaction has been clarified with combination of control experiments and 11B NMR analysis. This reaction is a self-promoted model, which is triggered by the trace of water and continuously promoted by self released by-product water (or carboxylic acid). A wide range of substrates are investigated and the moderate to excellent yields and the good regioselectivities for secondary benzyl alcohols as well as arenes bearing electron-withdrawing groups have been achieved. As a result, moisture in the reaction system has been utilized as an efficient initiator in all benzylation cases.
- Zhang, Shuting,Zhang, Xiaohui,Ling, Xuege,He, Chao,Huang, Ruofeng,Pan, Jing,Li, Jiaqiang,Xiong, Yan
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p. 30768 - 30774
(2014/08/05)
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- Iron-catalyzed arylation of aromatic ketones and aldehydes mediated by organosilanes
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A simple and efficient iron-catalyzed method for arylation of aromatic carbonyl compounds is reported. The use of 4-% FeCl3 or Fe(acac) 3 as the catalyst, in combination with a slight excess of chlorotrimethylsilane and triethylsilane, chlorination of benzylic ketones and aldehydes with subsequent Friedel-Crafts alkylation of arenes is achieved. Although the method is limited by the general constraints associated with Friedel-Crafts alkylation reactions, robust applications for the synthesis of pharmaceutical intermediates and so on can be envisioned. A robust one-pot, iron-catalyzed chlorination Friedel-Crafts alkylation reaction of benzylic carbonyl compounds, mediated by chlorotrimethylsilane and triethylsilane, has been developed to yield substituted diaryl and triaryl building blocks. Copyright
- Savela, Risto,Majewski, Marcin,Leino, Reko
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p. 4137 - 4147
(2014/07/08)
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- Iron-catalyzed friedel-crafts benzylation with benzyl TMS ethers at room temperature
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Friedel-Crafts benzylations between unactivated arenes and benzyl alcohol derivatives are clean and straightforward processes to construct biologically useful di- and triarylmethanes. We have established an efficient iron-catalyzed Friedel-Crafts benzylation method at room temperature that uses benzyl TMS ethers as substrates, which are poorly reactive under common nucleophilic substitution conditions. The reaction seems to progress through iron-catalyzed self-condensation of the benzyl TMS ether to the corresponding dibenzylic ether. The use of excess arene relative to benzyl TMS ether produced mono-benzylated arene (diand tri-arylmethane products), whereas the use of excess benzyl TMS ether versus arene provided bis-benzylated arene (polyarylated products) in high yields and regioselectivities. In previous methods, the latter double Friedel-Crafts benzylations hardly proceed.
- Sawama, Yoshinari,Shishido, Yuko,Kawajiri, Takahiro,Goto, Ryota,Monguchi, Yasunari,Sajiki, Hironao
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supporting information
p. 510 - 516
(2014/04/03)
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- Highly chemoselective and enantiospecific Suzuki-Miyaura cross-couplings of benzylic organoboronic esters
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The use of potassium carbonate in addition to silver oxide is shown to increase the enantiospecificity of the Suzuki-Miyaura cross-coupling reaction of chiral secondary benzylic boronic esters. From mechanistic studies, it is shown that the reaction is co
- Glasspoole, Ben W.,Oderinde, Martins S.,Moore, Brandon D.,Antoft-Finch, Aurora,Crudden, Cathleen M.
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p. 1759 - 1763
(2013/07/26)
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- Synthesis of diarylmethanes via a Friedel-Crafts benzylation using arenes and benzyl alcohols in the presence of triphenylphosphine ditriflate
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Triphenylphosphine ditriflate (TPPD) was found to be an efficient promoter for the Friedel-Crafts benzylation of arenes with benzyl alcohols in CH 2Cl2 at room temperature. The good yields, the 1:1 molar ratio of arene and benzyl alcohol, the benzylation of chlorobenzene as a nonactivated aromatic compound at room temperature, and no by-product formation are the main advantages of this procedure.
- Khodaei, Mohammad Mehdi,Nazari, Ehsan
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experimental part
p. 5131 - 5135
(2012/09/22)
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- NOVEL CATALYSTS
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The present invention provides novel compounds and ligands that are useful in transition metal catalyzed cross-coupling reactions. For example, the compounds and ligands of the present invention are useful in palladium or gold catalyzed cross-coupling reactions.
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Page/Page column 68-69
(2012/06/01)
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- Friedel-crafts benzylation of activated and deactivated arenes
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NO going back makes possible facile Friedel-Crafts benzylations with moderate reaction temperatures, simple reaction workups, and improved substrate scope for the formation of synthetically important diarylmethanes (see scheme). Upon complexation with BF3?OEt2, hydroxamates serve as reversible leaving groups that stabilize highly reactive carbocations. Even deactivated arenes and electron-deficient benzylhydroxamates react cleanly under these conditions.
- Schaefer, Gabriel,Bode, Jeffrey W.
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supporting information; experimental part
p. 10913 - 10916
(2012/01/02)
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- Iron(iii)-based ionic liquid-catalyzed regioselective benzylation of arenes and heteroarenes
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An easily prepared Fe(iii)-derived Lewis acid ionic liquid ([C 4mim][FeCl4]), being comprised of 1-butyl-3-methyl imidazolium cation and tetrachloroferrate anion, was found to be an efficient, recyclable catalyst for benzylation of various arenes/heteroarenes into the diarylmethanes derivatives under mild reaction conditions without utilization of additional organic solvent. Interestingly, the acidity of [C 4mim][FeCl4] could account for its catalytic activity in promoting the Lewis acid-catalyzed alkylation. Notably, this type of Fe(iii)-based ionic liquid (IL) shows excellent stability, and could be easily recovered, and reused for five times without significant loss of its catalytic activity.
- Gao, Jian,Wang, Jin-Quan,Song, Qing-Wen,He, Liang-Nian
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p. 1182 - 1186
(2011/06/25)
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- A simple catalyst for the efficient benzylation of arenes by using alcohols, ethers, styrenes, aldehydes, or ketones
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The compound [IrCp* (OTf)2(InBu)] (I nBu = 1,3-di-n-butyl-imidazolylidene) is an effective catalyst in the benzylation of arenes with different benzylating agents, such as alcohols, ethers and styrenes, representing an unprecedented highly versatile catalyst for this type of process. The same compound also catalyses a remarkable tandem process that allows the use of aldehydes and ketones as benzylating agents, through the base-free hydrogenation of C=O bonds with iPrOH and further use of the resulting primary or secondary alcohols as benzylating agents.
- Prades, Amparo,Corberan, Rosa,Poyatos, Macarena,Peris, Eduardo
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experimental part
p. 4610 - 4613
(2009/12/26)
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- Simple and efficient metal-free hydroarylation and hydroalkylation using strongly acidic ion-exchange resin
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Higly efficient hydroarylation and hydroalkylation of styrenes with various arenes and 1,3-dicarbonyl compounds respectively have been developed using Amberlyst-15 as a heterogeneous catalyst. The excellent yields, short reaction times, and high selectivity are the advantages of this method. The C-H functionalization has been achieved here under metal-free conditions. Copyright
- Das, Biswanath,Krishnaiah, Martha,Laxminarayana, Keetha,Damodar, Kongara,Kumar, D. Nandan
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experimental part
p. 42 - 43
(2009/12/02)
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- Highly efficient gold(III)-catalyzed intermolecular hydroarylation of unactivated alkenes with arenes under mild conditions
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A simple and efficient method for functionalization of electron-rich arenes and heteroarenes with unactivated alkenes by Au(III)-catalyzed intermolecular hydroarylation under mild reaction conditions was developed. This method features a short reaction time (5 h) under mild conditions and has a broad substrate scope, including electron-rich arenes and heteroarenes, terminal and internal substituted aryl alkenes, and unactivated aliphatic alkenes.
- Xiao, Ya-Ping,Liu, Xin-Yuan,Che, Chi-Ming
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experimental part
p. 494 - 501
(2009/06/06)
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- Synthesis of functionalized diaryl alkancs from azines
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Substituted diaryl alkanes arc synthesized from bcnzalazines and acctophenone/propiophenone azines via Friedel Craft's reaction with substituted mono- and poly-nuclear aromatic hydrocarbons. Diaryl methanes/ethanes and propanes are obtained by reaction with benzalazine, N,N'-bis (I-phenyl) azine and N, N'-bis (I-propyl) azine, respectively.
- Manih, Rudolf M.,Myrboh, Bekington
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experimental part
p. 146 - 151
(2009/12/01)
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- A new approach to carbon-carbon bond formation: development of aerobic Pd-catalyzed reductive coupling reactions of organometallic reagents and styrenes
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Alkenes are attractive starting materials for organic synthesis and the development of new selective functionalization reactions is desired. Previously, our laboratory discovered a unique Pd-catalyzed hydroalkoxylation reaction of styrenes containing a phenol. Based upon deuterium labeling experiments, a mechanism involving an aerobic alcohol oxidation coupled to alkene functionalization was proposed. These results inspired the development of a new Pd-catalyzed reductive coupling reaction of alkenes and organometallic reagents that generates a new carbon-carbon bond. Optimization of the conditions for the coupling of both organostannanes and organoboronic esters is described and the initial scope of the transformation is presented. Additionally, several mechanistic experiments are outlined and support the rationale for the development of the reaction based upon coupling alcohol oxidation to alkene functionalization.
- Gligorich, Keith M.,Iwai, Yasumasa,Cummings, Sarah A.,Sigman, Matthew S.
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experimental part
p. 5074 - 5083
(2009/12/01)
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- Influence of lewis acid and solvent in the hydrosiylation of aldehydes and ketones with Et3SiH; Tris(pentafluorophenyl)borane B(C 6F5)3 versus Metal inflates [M(OTf) 3; M = Sc, Bi, Ga, and Al] - Mecha
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The scope of the B(C6F5)3-catalyzed hydrosilylation of (X)Ph- CH=O and (X)Ph-C(R)=O was expanded to include a large set of subslitulents (X =H, p-Me, o-Me, p-F, o-F, p-Cl, p-Br, p-NO2m, m-NO2, p-Et; R
- Bach, Peter,Albright, Andrea,Laali, Kenneth K.
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experimental part
p. 1961 - 1966
(2009/09/06)
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- Alkene Hydrofunctionalization Reactions
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A reductive cross coupling reaction process for functionalization of a nucleophilic alkene can be achieved. The nucleophilic alkene and a nucleophilic cross coupling partner compound can be reacted in the presence of an oxidizable alcohol and a suitable catalyst to form a reductive coupling product. Various additives can also be useful to refine the process such as by mitigating certain undesirable intermediates, facilitating specific site selectivity for various substitutions or reaction sites, etc. Chiral additives can be optionally used which act to provide asymmetric catalysis, e.g. allow for regioselective and stereoselective production of reductive coupling products. A reductive cross coupling pathway can include oxidizing the oxidizable alcohol to form a catalyst hydride. The nucleophilic alkene can be inserted into the catalyst hydride to form a catalyst-alkyl intermediate. Further, the catalyst-alkyl intermediate can be transmetallized with the nucleophilic cross coupling partner compound to form a transmetallated intermediate. The catalyst can be reductively eliminated to form the reductive coupling product and a reduced catalyst. Finally, the reduced catalyst can be oxidized under aerobic conditions, for example with oxygen, to form the oxidized catalyst and subsequent repetition through the cyclic pathway.
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Page/Page column 10-11
(2009/04/24)
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- A novel InCl3/SiO2-catalyzed hydroarylation of arenes with styrenes under solvent-free conditions
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A novel InCl3/SiO2-catalyzed hydroarylation of various styrenes with arenes has been developed. The reaction can be carried out under solvent-free conditions to afford a series of 1,1-diarylalkanes in high yields and with good regioselectivities. The catalyst can be reused six times without obvious loss of catalytic activity. Georg Thieme Verlag Stuttgart.
- Sun, Gaojun,Sun, Huayin,Wang, Zhiyong,Zhou, Ming-Ming
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experimental part
p. 1096 - 1100
(2009/04/04)
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- Selective one-pot synthesis of various phenols from diarylethanes
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Various substituted phenols were selectively synthesized by a one-pot reaction through the NHPI-catalyzed aerobic oxidation of 1,1-diarylethanes followed by treatment with dilute sulfuric acid. The Royal Society of Chemistry.
- Nakamura, Ryota,Obora, Yasushi,Ishii, Yasutaka
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supporting information; experimental part
p. 3417 - 3419
(2009/02/05)
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- Aerobic alcohol oxidation coupled to palladium-catalyzed alkene hydroarylation with boronic esters
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(Chemical Equation Presented) An oxidation exercise: An aerobic alcohol oxidation coupled with a regioselective palladium-catalyzed reductive functionalization of styrenes and arylboronic esters has been developed (see scheme). The mechanism is thought to proceed by initial oxidation of the solvent to generate a PdII-hydride species, which subsequently reacts with the alkene and arylboronic ester to ultimately generate a new C-C bond.
- Iwai, Yasumasa,Gligorich, Keith M.,Sigman, Matthew S.
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p. 3219 - 3222
(2008/12/23)
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- Templation of the excited-state chemistry of α-(n-alkyl) dibenzyl ketones: how guest packing within a nanoscale supramolecular capsule influences photochemistry
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Excited-state behavior of eight α-alkyl dibenzyl ketones (alkyl = CH3 through n-C8H17) that are capable of undergoing type II and/or type I photoreactions has been explored in isotropic solution and within a water-soluble capsule. The study consisted of two parts: photochemistry that explored the excited-state chemistry and an NMR analysis that revealed the packing of each guest within the capsule. The NMR data (COSY, NOESY, and TOCSY experiments) revealed that ternary complexes between α-alkyl dibenzyl ketones and the capsule formed by two cavitands are kinetically stable, and the guests fall into three packing motifs modulated by the length of the α-alkyl chain. In essence, the host is acting as an external template to promote the formation of distinct guest conformers. The major products from all eight guests upon irradiation either in hexane or in buffer solution resulted from the well-known Norrish type I reaction. However, within the capsule the excited-state chemistry of the eight ketones was dependent on the alkyl chain length. The first group consisted of α-hexyl, α-heptyl, and α-octyl dibenzyl ketones that yielded large amounts of Norrish type II products within the host, while in solution the major products were from Norrish type I reaction. The second group consists of α-butyl and α-pentyl dibenzyl ketones that yield equimolar amounts of two rearranged starting ketones within the capsule (combined yield of ca 60%), while in solution no such products were formed. The third group consisted of α-methyl, α-ethyl, and α-propyl dibenzyl ketones that within the capsule yielded only one (not two) rearranged starting ketone in larger amounts (21-35%) while in solution no rearrangement product was obtained. Variation in the photochemistry of the guest within the capsule, with respect to the α-alkyl chain length of the guest, highlights the importance of how a small variation in supramolecular structure can influence the selectivity within a confined nanoscale reactor.
- Gibb, Corinne L. D.,Sundaresan, Arun Kumar,Ramamurthy,Gibb, Bruce C.
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p. 4069 - 4080
(2008/12/20)
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- Secondary benzylation with benzyl alcohols catalyzed by a high-valent heterobimetallic Ir-Sn complex
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(Chemical Equation Presented) A highly efficient secondary benzylation procedure has been demonstrated using a high-valent heterobimetallic complex [Ir2(COD)2(SnCls)2(Cl)2(μ-Cl) 2] 1 as the catalyst in 1,2-dichloroethane to afford the corresponding benzylated products in moderate to excellent yields. The reaction was performed not only with carbon nucleophiles (arenes and heteroarenes) but also with oxygen (alcohol), nitrogen (amide and sulfonamide), and sulfur (thiol) nucleophiles. Mechanistic investigation showed the intermediacy of the ether in this reaction. An electrophilic mechanism is proposed from Hammett correlation.
- Podder, Susmita,Choudhury, Joyanta,Roy, Sujit
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p. 3129 - 3132
(2008/02/07)
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- Palladium-catalyzed reductive coupling of styrenes and organostannanes under aerobic conditions
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We report a highly regioselective PdII-catalyzed reductive coupling of an alkene with an organostannane using a tandem alcohol oxidation under aerobic conditions. Both aryl- and vinylstannanes are competent coupling partners with a variety of s
- Gligorich, Keith M.,Cummings, Sarah A.,Sigman, Matthew S.
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p. 14193 - 14195
(2008/09/18)
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- An effective bismuth-catalyzed benzylation of arenes and heteroarenes
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A highly efficient Bi(OTf)3-catalyzed benzylation of arenes and heteroarenes has been developed. The mild reaction conditions, high yields, operational simplicity and practicability, broad scope, and remarkably low catalyst loading render this environment friendly process an attractive approach to diarylmethane derivatives. The extension to an intramolecular variant of this procedure provides a valuable route to substituted fluorenes.
- Rueping, Magnus,Nachtsheim, Boris J.,Ieawsuwan, Winai
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p. 1033 - 1037
(2007/10/03)
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- Efficient metal-catalyzed hydroarylation of styrenes
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A highly efficient metal-catalyzed hydroarylation of various styrenes has been developed. This new bismuth-catalyzed C-H functionalization provides straightforward access to a series of valuable 1,1-diarylalkane products.
- Rueping, Magnus,Nachtsheim, Boris J.,Scheidt, Thomas
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p. 3717 - 3719
(2007/10/03)
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- Gold-catalyzed benzylation of arenes and heteroarenes
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Friedel-Crafts type benzylation of arenes and heteroarenes with benzylic acetates, alcohols, and carbonates is effectively promoted under mild reaction conditions using catalytic amounts of gold salts. The resulting 1,1-diarylalkanes and 1-aryl-1-heteroarylalkanes are obtained in high yields and with high selectivity. The utility of the method is demonstrated by a short synthesis of beclobrate {ethyl 2-[4-(4-chlorobenzyl)-phenoxy]-2-methylbutyrate (3)}, a fibric acid derivative.
- Mertins, Kristin,Iovel, Irina,Kischel, Jette,Zapf, Alexander,Beller, Matthias
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p. 691 - 695
(2007/10/03)
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- Transition-metal-catalyzed benzylation of arenes and heteroarenes
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Friedel-Crafts-type benzylation of various aromatic and heteroaromatic compounds with benzylic acetates, alcohols, and carbonates was promoted under mild reaction conditions by a series of Rh, Ir, Pd, and Pt catalysts (see scheme; R1 = H, Me; R2 = H, Cl, MeO; R3 = H, Ac, CO2Me). The desired products were obtained in high yields and with high selectivities.
- Mertins, Kristin,Iovel, Irina,Kischel, Jette,Zapf, Alexander,Beller, Matthias
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p. 238 - 242
(2007/10/03)
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- An efficient and general iron-catalyzed arylation of benzyl alcohols and benzyl carboxylates
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(Chemical Equation Presented) Green grow the diarylmethanes: Substituted arenes and heteroarenes can be easily benzylated in the presence of inexpensive and relatively nontoxic metal salts such as FeCl3 (see scheme). This arylation method with benzyl alcohols is a state-of-the-art green route to diarylmethanes as water is the only by-product.
- Iovel, Irina,Mertins, Kristin,Kischel, Jette,Zapf, Alexander,Beller, Matthias
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p. 3913 - 3917
(2007/10/03)
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- Resolution of secondary alcohols using 2-acyl-3-phenyl-l-menthopyrazoles as enantioselective acylating agents
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The chelation of AlCl3 with N-acylpyrazoles leads to structural fixation of the acyl moiety and an acceleration in the rate of acylation of secondary alcohols. The chiral environment of the fixed acyl moiety of 2-acyl-3-phenyl-l-menthopyrazole 2 causes diastereofacial selectivity in the reaction with secondary alcohols, and thus 2 behaves as an enantioselective acylating agent. By the use of 2.4 molar equivalents of racemic 1-phenylethanol 3a, 2-acetyl-3-phenyl-l-menthopyrazole 2a afforded (S)-1-phenylethyl acetate (S)-4aa enantioselectively and unreacted 3a was recovered with (R)-configuration. Furthermore, the inverse configurational preferences were observed to give (R)-4aa and (S)-3a by the addition of strongly basic amines, which sometimes behaved as catalysts for enolate formation from 2 and AlCl3. These dramatic changes in stereoselective preference should be useful properties of 2-acyl-3-phenyl-l-menthopyrazole 2 as an enantioselective acylating agent.
- Kashima, Choji,Mizuhara, Saori,Miwa, Yohei,Yokoyama, Yukihiro
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p. 1713 - 1719
(2007/10/03)
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- Lithium tetrakis(pentafluorophenyl)borate-catalyzed Friedel-Crafts benzylation reactions
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Lithium tetrakis(pentafluorophenyl)borate [LiB(C6F5)4], a neutral salt, effectively catalyzed Friedel-Crafts benzylation reactions of aromatic compounds with benzyl chloride or mesylate and their substituted derivatives. The LiB(C6F5)4-catalyzed reactions proceeded more efficiently in the coexistence of magnesium oxide.
- Mukaiyama, Teruaki,Nakano, Masakazu,Kikuchi, Wataru,Matsuo, Jun-Ichi
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p. 1010 - 1011
(2007/10/03)
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- Novel reductive Friedel-Crafts alkylation of aromatics catalyzed by indium compounds: Chemoselective utilization of carbonyl moieties as alkylating reagents
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Reductive Friedel-Crafts alkylation of aromatics with ketones or aldehydes was characteristically catalyzed by indium compounds in preference to general catalysts like AlCl3 and BF3, where hydrosilanes would play an important role both as a hydride donor and as a co-catalyst. Chemoselective utilization of ketone moieties as alkylating reagents took place even in the presence of halogen, ester or ether moieties which are very susceptible under traditional Friedel-Crafts conditions. Discussion on a plausible intermediate was carried out by some controlled experiments.
- Miyai, Takashi,Onishi, Yoshiyuki,Baba, Akio
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p. 1017 - 1026
(2007/10/03)
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- Indium trichloride catalyzed reductive Friedel-Crafts alkylation of aromatics using carbonyl compounds
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Reductive Friedel-Crafts alkylation of aromatics with aldehydes or ketones using chlorodimethylsilane as a hydride source was effectively promoted by a catalytic amount of indium trichloride, whereas a popular type of Friedel-Crafts catalysts showed less effect.
- Miyai, Takashi,Onishi, Yoshiyuki,Baba, Akio
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p. 6291 - 6294
(2007/10/03)
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- Hafnium(IV)Trifluoromethanesulfonate, An Efficient Catalyst for the Friedel-Crafts Acylation and Alkylation Reactions
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Hafnium(IV) trifluoromethanesulfonate (hafnium(IV) triflate, Hf(OTf)4) was synthesized from hafnium tetrachloride and trifluoromethanesulfonic acid.The triflate thus prepared was found to be effective in the catalytic Friedel-Crafts acylation reactions of various substituted benzenes with acid anhydrides in lithium perchlorate-nitromethane (LiClO4-MeNO2).Lithium perchlorate-nitromethane is an excellent solvent system, and the catalytic activity of the Lewis acid was much improved in this medium.The product was obtained in up to 250000percent molar amounts baaed on the catalyst.Hafnium(IV) triflate was also found to be quite effective in the catalytic Friedel-Crafts alkylation reactions of aromatic compounds with alkyl chlorides.The reactions proceeded smoothly in the presence of 5percent molar amount of Hf(OTf)4 and 50percent molar amount of LiClO4 by using a slow addition procedure.
- Hachiya, Iwao,Moriwaki, Mitsuhiro,Kobayashi, Shu
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p. 2053 - 2060
(2007/10/02)
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- ACID-CATALYZED DIMERIZATION AND ARALKYLATION IN DIVINYLAROMATIC COMPOUND-AROMATIC SOLVENT SYSTEMS
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On heating styrene and bis(4-vinylphenyl) ether or a linear unsaturated aromatic oligomer with terminal vinyl groups in aromatic solvents, depending on the temperature and concentration of toluene-p-sulfonic acid, there are obtained predominantly dimers and linear oligomers, and/or products of the alkylation of the aromatic solvent by the unsaturated monomers, dimers, and oligomers.
- Zaitsev, B. A.,Kiseleva, R. F.,Denisov, V. M.,Kol'tsov, A. I.
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p. 2323 - 2330
(2007/10/02)
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- Lewis Acid-induced Nucleophilic Substitution Reactions of Aliphatic Nitro Compounds with Carbon Nucleophiles
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Tertiary, benzyl, and allylic nitro compounds undergo nucleophilic substitution reactions with carbon nucleophiles such as electron rich aromatic compounds, allylsilanes, or silyl enol ethers in the presence of SnCl4.
- Ono, Noboru,Yanai, Tetsuya,Kamimura, Akio,Kaji, Aritsune
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p. 1285 - 1287
(2007/10/02)
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- Selenium and Tellurium Tetrachlorides as Reagents for the Conversion of Alcohols to Alkyl Chlorides and Tellurium Tetrachloride as a Lewis Acid Catalyst for Aromatic Alkylation
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Selenium tetrachloride(SeCl4) reacts smoothly with alcohols in various nonpolar solvents to give the corresponding alkyl chlorides in 44-97percent yield.Similar reaction also proceeds with tellurium tetrachloride(TeCl4), while the treatement of benzyl, 1-phenylethyl, and t-butyl alcohols with TeCl4 in aromatic solvents results in a high yield formation of alkylated aromatics instead of alkyl chlorides.Such Friedel-Crafts aromatic alkylation hardly occurs in the SeCl4 case.The chlorination species is not chlorine which might be evolved by dissociation of SeCl4 or TeCl4, but the metal chloride itself.The conversion of optically active R-(+)-1- phenylethanol to 1-phenylethyl chloride proceeds with nearly complete racemisation.
- Yamauchi, Takayoshi,Hattori, Kaneaki,Mizutaki, Shoichi,Tamaki, Kentaro,Uemura, Sakae
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p. 3617 - 3620
(2007/10/02)
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- REACTION OF MONOSUBSTITUTED AROMATIC HYDROCARBONS WITH STYRENE
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1,1-Phenylarylethanes were obtained by the reaction of styrene with some monosubstituted aromatic hydrocarbons in the presence of titanium tetrachloride.It was established that electron-donating substituents have an effect on the yield of the arylalkylation products.
- Grushin, A. I.,Grigor'ev, V. V.,Prokof'ev, K. V.,Kozlova, N. M.
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p. 1991 - 1993
(2007/10/02)
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