- Bismuth(III) chloride-catalyzed direct deoxygenative allylation of substituted benzylic alcohols with allyltrimethylsilane
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A highly effective protocol for allylation of sec-benzyl alcohols with allyltrimethylsilane in the presence of a catalytic amount of bismuth(III) chloride has been developed.
- De, Surya K.,Gibbs, Richard A.
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Read Online
- Indium-silicon combined Lewis acid catalyst for direct allylation of alcohols with allyltrimethylsilane in non-halogenated solvent
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A direct allylation of alcohols is effectively catalyzed by a combined Lewis acid system of InCl3 and Me3SiBr. This system allows use of non-halogenated solvents such as hexane and application to a wide range of alcohols. Georg Thieme Verlag Stuttgart.
- Saito, Takahiro,Yasuda, Makoto,Baba, Akio
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Read Online
- Palladium-Catalyzed Electrochemical Allylic Alkylation between Alkyl and Allylic Halides in Aqueous Solution
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A new route for the direct cross-coupling of alkyl and allylic halides using electrochemical technique has been developed in aqueous media under air. Catalyzed by Pd(OAc)2, the Zn-mediated allylic alkylations proceed smoothly between a full range of alkyl halides (primary, secondary, and tertiary) and substituted allylic halides. Protection-deprotection of acidic hydrogen in the substrates is avoided.
- Lai, Yin-Long,Huang, Jing-Mei
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Read Online
- Silylated cyclopentadienes as competent silicon Lewis acid catalysts
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The synthesis and characterization of silicon Lewis acid complexes that incorporate highly electron-deficient cyclopentadienes is reported. Several pentacarboxycyclopentadienyl and monocarboxytetracyanocyclopentadienyl complexes were prepared. A comparison of their reactivities for catalysis of the allylation of an electron-deficient benzaldehyde was established. The use of a monocarboxytetracyano silylium donor was shown to be effective for the allylation or arylation of a variety of electrophiles via an anion abstraction pathway.
- Radtke, M. Alex,Lambert, Tristan H.
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- CROSS-COUPLING REACTION OF SECONDARY ALKYL GRIGNARD REAGENTS WITH ALLYLIC ALCOHOLS CATALYZED BY DICHLOROPALLADIUM(II)
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Dichloropalladium(II) was found to catalyze the reaction of allylic alcohols with 2-octylmagnesium chloride and 1-phenylethylmagnesium chloride to give the corresponding cross-coupling products in high yields.
- Hayashi, Tamio,Konishi, Mitsuo,Kumada, Makoto
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Read Online
- Efficient and mild iron-catalyzed direct allylation of benzyl alcohols and benzyl halides with allyltrimethylsilane
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An efficient and mild iron-catalyzed direct allylation of benzyl alcohols and benzyl halides with allyltrimethylsilane has been developed. The present reaction would provide an excellent alternative to published methods because of its excellent yields, sustainable catalyst, and mild conditions. Copyright Taylor & Francis Group, LLC.
- Han, Jie,Cui, Zili,Wang, Jianguo,Liu, Zhongquan
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Read Online
- Designed electron-deficient gold nanoparticles for a room-temperature Csp3-Csp3coupling reaction
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Stille cross-coupling reactions catalysed by an ideal catalyst combining the high activity of homogeneous catalysts and the reusability of heterogeneous catalysts are of great interest for C-C bond formation, which is a widely used reaction in fine chemistry. Despite great effort to increase the utilization ratio of surface metal atoms, the activity of heterogeneous catalysts under mild conditions remains unsatisfactory. Herein, we design a proof-of-concept strategy to trigger the room-temperature activity of heterogeneous Au catalysts by decreasing the electron density at the interface of a rationally designed Schottky heterojunction of Au metals and boron-doped carbons. The electron-deficient Au nanoparticles formed as a result of the rectifying contact with boron-doped carbons facilitate the autocleavage of C-Br bonds for highly efficient C-C coupling reactions of alkylbromides and allylstannanes with a TOF value of 5199 h-1 at room temperature, surpassing that of the state-of-the-art homogeneous catalyst. This journal is
- Yu, Qiu-Ying,Su, Hui,Zhai, Guang-Yao,Zhang, Shi-Nan,Sun, Lu-Han,Chen, Jie-Sheng,Li, Xin-Hao
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supporting information
p. 741 - 744
(2021/02/06)
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- Visible-Light Controlled Divergent Catalysis Using a Bench-Stable Cobalt(I) Hydride Complex
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While the use of visible light in conjunction with transition metal catalysis offers powerful opportunities to switch between on/-off states of catalytic activity, the next frontier would be the ability to switch the actual function of the catalyst and resulting products. Here we report such an example of multi-dimensional catalysis. Featuring an easily prepared, bench-stable cobalt(I) hydride complex in conjunction with pinacolborane, we can switch the reaction outcome between two widely employed transformations, olefin migration and hydroboration, with visible light as the trigger.
- Beltran, Frédéric,Bergamaschi, Enrico,Teskey, Christopher J.
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supporting information
p. 5180 - 5184
(2020/04/22)
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- In Situ Generated Gold Nanoparticles on Active Carbon as Reusable Highly Efficient Catalysts for a Csp3 ?Csp3 Stille Coupling
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Gold nanoparticle catalysts are important in many industrial production processes. Nevertheless, for traditional Csp2-Csp2 cross-coupling reactions they have been rarely used and Pd catalysts usually give a superior performance. Herein we report that in situ formed gold metal nanoparticles are highly active catalysts for the cross coupling of allylstannanes and activated alkylbromides to form Csp3-Csp3 bonds. Turnover numbers up to 29 000 could be achieved in the presence of active carbon as solid support, which allowed for convenient catalyst recovery and reuse. The present study is a rare case where a gold metal catalyst is superior to Pd catalysts in a cross-coupling reaction of an organic halide and an organometallic reagent.
- Holz, Julia,Pfeffer, Camilla,Zuo, Hualiang,Beierlein, Dennis,Richter, Gunther,Klemm, Elias,Peters, René
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supporting information
p. 10330 - 10334
(2019/06/27)
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- (CDC)-Rhodium-catalyzed hydroallylation of vinylarenes and 1,3-dienes with allyltrifluoroborates
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Catalytic site-selective hydroallylation of vinyl arenes and 1,3-dienes is reported. Transformations are promoted by a readily accessible bidentate carbodicarbene-rhodium complex and involve commercially available allyltrifluoroborates and an alcohol. The reaction is applicable to vinyl arenes and aryl-or alkyl-substituted 1,3-dienes (30 examples). Allyl addition products are generated in 40-78% yield and in up to >98:2 site selectivity. Reaction outcomes are consistent with the intermediacy of a Rh(III)-hydride generated by protonation of Rh(I) by an acid. A number of key mechanistic details of the reaction are presented: (1) Deuterium scrambling into the product and starting alkene indicates reversible Rh(III)-H migratory insertion. (2) A large primary kinetic isotope effect is observed. (3) With substituted allyltrifluoroborates (e.g., crotyl-BF3K) mixtures of site isomers are generated as a result of transmetalation followed by Rh-(allyl) complex equilibration, consequently disproving outer-sphere addition of the allyl nucleophile to Rh(III)-(η3-allyl). (4) Stereochemical analysis of a cyclohexadiene allyl addition product supports a syn Rh(III)-hydride addition. (5) A Hammett plot shows a negative slope. Finally, utility is highlighted by a iodocyclization and cross metathesis.
- Marcum, Justin S.,Cervarich, Tia N.,Manan, Rajith S.,Roberts, Courtney C.,Meek, Simon J.
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p. 5881 - 5889
(2019/08/15)
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- Rhenium complex-catalyzed carbon-carbon formation of alcohols and organosilicon compounds
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The coupling reactions of allylic and benzylic alcohols and allyltrimethylsilane are efficiently catalyzed by a rhenium complex to give the corresponding 1,5-dienes and alkenes in moderate to good yields. Similarly, alcohols were coupled with ketene silyl acetals to form the corresponding esters.
- Umeda, Rui,Jikyo, Toshifumi,Toda, Kazuki,Osaka, Issey,Nishiyama, Yutaka
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supporting information
p. 1121 - 1124
(2018/02/21)
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- Umpolung of Carbonyl Groups as Alkyl Organometallic Reagent Surrogates for Palladium-Catalyzed Allylic Alkylation
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Palladium-catalyzed allylic alkylation of nonstabilized carbon nucleophiles is difficult and remains a major challenge. Reported here is a highly chemo- and regioselective direct palladium-catalyzed C-allylation of hydrazones, generated from carbonyls, as a source of umpolung unstabilized alkyl carbanions and surrogates of alkyl organometallic reagents. Contrary to classical allylation techniques, this umpolung reaction utilizes hydrazones prepared not only from aryl aldehydes but also from alkyl aldehydes and ketones as renewable feedstocks. This strategy complements the palladium-catalyzed coupling of unstabilized nucleophiles with allylic electrophiles by providing an efficient and selective catalytic alternative to the traditional use of highly reactive alkyl organometallic reagents.
- Zhu, Dianhu,Lv, Leiyang,Li, Chen-Chen,Ung, Sosthene,Gao, Jian,Li, Chao-Jun
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supporting information
p. 16520 - 16524
(2018/11/23)
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- Testing the veracity of claims of Lewis acid catalysis
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Are reactions employing Lewis acids really catalysed by those Lewis acids, or by “hidden Br?nsted acids”, i.e. Br?nsted acids generated in situ by hydrolysis? Testing of a series of reactions using Sc(III), Fe(III), In(III) and Y(III) by addition of 2,6-di-t-butyl-4-methylpyridine reveal that all are likely to follow the latter pathway. A reaction claimed to be catalysed by CBr4 through halogen bonding is also likely to be Br?nsted acid catalysed.
- ?oli?, Ivan,Lin, Hong Xuan,Bates, Roderick W.
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supporting information
p. 4434 - 4436
(2018/11/23)
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- Cobalt-Catalyzed Benzylic Borylation: Enabling Polyborylation and Functionalization of Remote, Unactivated C(sp3)-H Bonds
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Cobalt dialkyl and bis(carboxylate) complexes bearing α-diimine ligands have been synthesized and demonstrated as active for the C(sp3)-H borylation of a range of substituted alkyl arenes using B2Pin2 (Pin = pinacolate) as the boron source. At longer reaction times, rare examples of polyborylation were observed, and in the case of toluene, all three benzylic C-H positions were functionalized. Coupling benzylic C-H activation with alkyl isomerization enabled a base-metal-catalyzed method for the borylation of remote, unactivated C(sp3)-H bonds.
- Palmer, W. Neil,Obligacion, Jennifer V.,Pappas, Iraklis,Chirik, Paul J.
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supporting information
p. 766 - 769
(2016/02/05)
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- Methyltriphenylphosphonium Methylcarbonate, an All-In-One Wittig Vinylation Reagent
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The methyltriphenylphosphonium methylcarbonate salt [Ph3PCH3][CH3OCO2], obtained directly by quaternarization of triphenylphosphine with dimethylcarbonate, is a latent ylide that promotes Wittig vinylation of aldehydes and ketones. Alkenes are obtained simply by mixing [Ph3PCH3][CH3OCO2] and the carbonyl and heating in a solvent (no base, no halides, and no inorganic byproducts). Deuterium exchange experiments and the particularly short anion-cation distance measured by XRD in [Ph3PCH3][CH3OCO2] allowed to explain the nature and reactivity of this species. Green chemistry metrics (atom economy, mass index, environmental factor) indicate that this vinylation procedure is more efficient than comparable ones. Deuterated [Ph3PCD3][CH3OCO2] promoted the synthesis of deuterated olefins. Add carbonyl and go! The Wittig reaction is widely applied, despite having shortcomings such as low atom economy (AE), the necessity to use solvents, and stoichiometric amounts of waste from generating the ylide. [Ph3PCH3][CH3OCO2] is a latent phosphorous ylide that promotes Wittig vinylation of aldehydes and ketones by simply heating with the carbonyl. No external base and no halides involved, and the protocol offers good AE, environmental factor, and mass index.
- Cattelan, Lisa,Noè, Marco,Selva, Maurizio,Demitri, Nicola,Perosa, Alvise
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p. 3963 - 3966
(2015/12/17)
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- Copper-Catalyzed Cross-Coupling Reaction of Allyl Boron Ester with 1°/2°/3°-Halogenated Alkanes
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The cross-coupling reaction of allyl boron ester with 1°/2°/3°-halogenated alkanes in the presence of copper has been developed for the first time, which provides a mild and efficient method for the construction of saturated C(sp3)-C(sp3) bonds. This protocol shows excellent compatibility with the nonactivated primary, secondary, and even tertiary halogenated alkanes under mild conditions.
- Wang, Guang-Zu,Jiang, Jian,Bu, Xiao-Song,Dai, Jian-Jun,Xu, Jun,Fu, Yao,Xu, Hua-Jian
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supporting information
p. 3682 - 3685
(2015/08/18)
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- Catalytic properties and acidity of 1,2-benzenedisulfonimide and some of its derivatives. An experimental and computational study
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1,2-Benzenedisulfonimide (1) has previously been found to be an excellent and, importantly, safe Br?nsted acid catalyst. In this work we present the results of a search for derivatives of 1 that are more acidic and effective. Instead of blindly synthesizing a series of analogues, we have carried out a screening process in which the pKa of 1 and a set of its derivatives were calculated. The calculated pKa values were confirmed experimentally by carrying out determination through potentiometric titrations of some of the compounds: 1, 4-methyl and 4-nitro derivatives of 1. The calculations indicated that the dinitro and 4-nitro derivatives are among the best candidates for the synthesis. The latter was obtained in good yields and tested as a catalyst. Results were excellent as the reactions took place more quickly and at lower temperatures in all cases, and in a number of cases it was even possible to reduce the amount of catalyst.
- Barbero, Margherita,Berto, Silvia,Cadamuro, Silvano,Daniele, Pier Giuseppe,Dughera, Stefano,Ghigo, Giovanni
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p. 3212 - 3217
(2013/04/24)
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- Indium(i)-catalyzed alkyl-allyl coupling between ethers and an allylborane
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An efficient method for alkyl-allyl cross-coupling between ethers and a 9-BBN-derived allylborane catalyzed by indium(i) triflate has been developed. The allylborane proved to be essential to obtain the desired products in high yields. The reaction displayed good substrate scope including high functional group tolerance. The Royal Society of Chemistry 2011.
- Dao, Hai Thanh,Schneider, Uwe,Kobayashi, Shu
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p. 692 - 694
(2011/03/22)
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- Calcium-catalyzed direct coupling of alcohols with organosilanes
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A calcium-catalyzed direct substitution of π-activated alcohols with different organosilanes under very mild reaction conditions is presented. The high reactivity of the calcium catalyst allows efficient conversion of secondary and tertiary allylic, secondary benzylic, and tertiary propargylic alcohols with allyltrimethylsilane at room temperature. Furthermore, the first direct substitution of an alcohol with (E)- as well as (Z)-alkenylsilanes was achieved under mild reaction conditions. Copyright
- Meyer, Vera J.,Niggemann, Meike
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supporting information; experimental part
p. 3671 - 3674
(2011/09/14)
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- "Design" of boron-based compounds as pro-nucleophiles and co-catalysts for indium(I)-catalyzed allyl transfer to various Csp 3-type electrophiles
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We have recently uncovered a general indium(I)-catalyzed method for allylations and propargylation of acetals and ketals with a water- and air-stable allyl boronate. By using a more reactive allyl borane, we have successfully extended this methodology to the more challenging C-C coupling with ethers. Herein, we report an improved methodology for the indium(I)-catalyzed allylation of acetals and ethers, through combination of the allyl boronate with a commercially available "hard" Lewis acid, B-methoxy-9-BBN (BBN=borabicyclo[3.3.1]nonane), as an effective co-catalyst. Significantly, our work highlights for the first time the correlation between the Lewis acidity of "electrophilic" boron-based compounds and their " nucleophilic" reactivity in Csp3-Csp3 couplings, catalyzed by a "soft" low-oxidation main group metal. In addition, we also report several applications of these methodologies to the selective synthesis of various carbohydrate derivatives. Copyright
- Dao, Hai Thanh,Schneider, Uwe,Kobayashi, Shu
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experimental part
p. 2522 - 2529
(2012/07/13)
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- Rhodium-catalyzed allylation of benzyl acetates with allylsilanes
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Benzyl acetate reacted with allyltrimethylsilane to give an allylation product in the presence of a catalytic amount of the (cyclooctadiene)rhodium(I) chloride dimer {[Rh(cod)Cl]2}, sodium tetrakis[3,5- bis(trifluoromethyl)phenyl]borate (NaBARF), and triphenyl phosphite [P(OPh) 3] in refluxing 1,2-dichloroethane. Primary, secondary and tertiary benzyl acetates could be used for the reaction. Moreover, allylation of gem-benzyl acetate was possible with [Rh(cod)Cl]2, NaBARF, and P(OPh)3. Monoallylation and diallylation of gem-benzyl acetate could be controlled by altering the reaction conditions. Cationic rhodium species generated in situ act as a Lewis acid catalyst to give a benzyl carbocation by elimination of the acetoxy group from the benzylic carbon. Copyright
- Onodera, Gen,Yamamoto, Eriko,Tonegawa, Shota,Iezumi, Makoto,Takeuchi, Ryo
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scheme or table
p. 2013 - 2021
(2011/10/09)
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- Fe(OTf)3-catalyzed reaction of benzylic acetates with organosilicon compounds
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Fe(OTf)3-catalyzed reaction of benzylic acetates with allyltrimethylsilane, azidotrimethylsilane, and cyanotrimethylsilane afforded the corresponding allylated, azido, and cyano products in high yields. 2-Trimethylsilyl-substituted benzofuran and indole worked well to furnish the benzyl-substituted benzofuran and indoles. Georg Thieme Verlag Stuttgart New York.
- Chan, Li Yan,Kim, Sundae,Chung, Wan Ting,Long, Chong,Kim, Sunggak
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experimental part
p. 415 - 419
(2011/04/22)
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- O-Benzenedisulfonimide as a reusable broonsted acid catalyst for hosomi-sakurai reactions
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Various acetals or alcohols react with allyl(trimethyl)silane or 1-phenyl-2-(trimethylsilyl)acetylene in the presence of a catalytic amount of the Bronsted acid o-benzenedisulfonimide under mild conditions to give good yields of the corresponding products. The catalyst can be easily recovered and purified for use in further reactions, which has economic and ecological advantages. Georg Thieme Verlag Stuttgart.
- Barbero, Margherita,Bazzi, Stefano,Cadamuro, Silvano,Dughera, Stefano,Piccinini, Claudia
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experimental part
p. 315 - 319
(2010/03/05)
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- Direct allylation of α-aryl alcohols with allyltrimethylsilane catalyzed by heterogeneous tin ion-exchanged montmorillonite
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The direct allylation of α-aryl alcohols with allyltrimethylsilane efficiently proceeded in the presence of tin ion-exchanged montmorillonite under mild conditions according to the proper addition order of reactants and a catalyst.
- Wang, Jiacheng,Masui, Yoichi,Onaka, Makoto
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experimental part
p. 3300 - 3303
(2010/07/06)
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- Protodeboronation of tertiary boronic esters: Asymmetric synthesis of tertiary alkyl stereogenic centers
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While tertiary boranes undergo efficient protodeboronation with carboxylic acids, tertiary boronic esters do not. Instead, we have discovered that CsF with 1.1 equiv of H2O (on tertiary diarylalkyl boronic esters) or TBAF?3H2O (on tertiary aryldialkyl boronic esters) effect highly efficient protodeboronation of tertiary boronic esters with essentially complete retention of configuration. Furthermore, substituting D2O for H2O provides ready access to deuterium-labeled enantioenriched tertiary alkanes. The methodology has been applied to a short synthesis of the sesquiterpene, (S)-turmerone.
- Nave, Stefan,Sonawane, Ravindra P.,Elford, Tim G.,Aggarwal, Varinder K.
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supporting information; experimental part
p. 17096 - 17098
(2011/03/01)
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- Regioselective cross-coupling of allylindium reagents with activated benzylic bromides-a simple and efficient procedure for the synthesis of terminal alkenes
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Allylindium reagents undergo facile and highly regioselective cross-coupling with benzylic and cinnamyl bromides in THF at room temperature without any catalyst producing terminal alkenes in high yields. The addition is highly regioselective and is found to provide γ-adducts in all reactions.
- Ranu, Brindaban C.,Banerjee, Subhash,Adak, Laksmikanta
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p. 7374 - 7379
(2008/03/13)
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- Rhenium- and gold-catalyzed coupling of aromatic aldehydes with trimethyl(phenylethynyl)silane: Synthesis of diethynylmethanes
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(Chemical Equation Presented) Very couply! Coupling reactions of propargyl or benzyl alcohols with allyl- or alkynylsilanes proceed efficiently using [{ReBr(CO)3(thf)}2] as catalyst. Additionally, diethynylmethane derivatives were obtained by the reaction of aromatic aldehydes with trimethyl(phenylethynyl)silane in the presence of both the rhenium complex and AuCl (see scheme).
- Kuninobu, Yoichiro,Ishii, Eri,Takai, Kazuhiko
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p. 3296 - 3299
(2008/03/11)
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- Nucleophilic substitution reactions of alcohols with use of montmorillonite catalysts as solid Bronsted acids
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(Chemical Equation Presented) We have developed an environmentally benign synthetic approach to nucleophilic substitution reactions of alcohols that minimizes or eliminates the formation of byproducts, resulting in a highly atom-efficient chemical process. Proton- and metal-exchanged montmorillonites (H- and Mn+-mont) were prepared easily by treating Na +-mont with an aqueous solution of hydrogen chloride or metal salt, respectively. The H-mont possessed outstanding catalytic activity for nucleophilic substitution reactions of a variety of alcohols with anilines, because the unique acidity of the H-mont catalyst effectively prevents the neutralization by the basic anilines. In addition, amides, indoles, 1,3-dicarbonyl compounds, and allylsilane act as nucleophiles for the H-mont-catalyzed substitutions of alcohols, which allowed efficient formation of various C-N and C-C bonds. The solid H-mont was reusable without any appreciable loss in its catalytic activity and selectivity. Especially, an Al3+-mont showed high catalytic activity for the α-benzylation of 1,3-dicarbonyl compounds with primary alcohols due to cooperative catalysis between a protonic acid site and a Lewis acidic Al3+ species in its interlayer spaces.
- Motokura, Ken,Nakagiri, Nobuaki,Mizugaki, Tomoo,Ebitani, Kohki,Kaneda, Kiyotomi
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p. 6006 - 6015
(2008/02/10)
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- InCl3-catalyzed cross-coupling of alkyl trimethylsilyl ethers and allylsilanes via an in situ derived combined lewis acid of InCl3 and Me3SiI
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(Chemical Equation Presented) Direct Csp3-Csp3 coupling of various aliphatic trimethylsilyl ethers and allylsilanes is effectively catalyzed by InCl3 and I2. The transformation is thought to involve an in situ-derived combined Lewis acid of InCl3 and Me3SiI. The reaction can be used for the construction of quaternary-quaternary and quaternary-tertiary carbon-carbon bonds. This system enabled a highly chemoselective coupling to be conducted with a trimethylsilyl ether including an aryl halide moiety. Furthermore, couplings were possible using an alkynyltri-methylsilane and a trimethylsilyl ketene acetal.
- Saito, Takahiro,Nishimoto, Yoshihiro,Yasuda, Makoto,Baba, Akio
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p. 8588 - 8590
(2008/02/12)
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- Deoxygenative allylation of benzyl acetates and cinnamyl alcohols catalyzed by molecular iodine
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Benzyl acetates undergo smooth deoxygenative allylation with allyltrimethylsilane in the presence of 10 mol % of molecular iodine under mild conditions to afford the corresponding allyl derivatives in excellent yields and with high selectivity. Cinnamyl alcohols also react readily with allylsilane under similar conditions. The use of molecular iodine makes this method quite simple, more convenient and cost effective. Copyright
- Yadav,Reddy, B. V. Subba,Reddy, A. Srinivas,Eeshwaraiah
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p. 1500 - 1501
(2008/03/14)
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- Direct coupling reaction between alcohols and silyl compounds: Enhancement of Lewis acidity of Me3SiBr using InCl3
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The combination of InCl3 and Me3SiBr provided an enhanced Lewis acid system that can be used to promote a wide range of direct coupling reactions between alcohols and silyl nucleophiles in non-halogenated solvents, such as hexane or MeCN. The enhanced Lewis acidity of this system was measured by the 13C NMR in terms of the coordination to an alcohol. Moreover, the interaction between Me3SiBr and the In(III) species was revealed by 29Si NMR spectral analysis. Highly chemoselective allylations toward a hydroxyl moiety over ketone and acetoxy ones have been demonstrated.
- Saito, Takahiro,Nishimoto, Yoshihiro,Yasuda, Makoto,Baba, Akio
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p. 8516 - 8522
(2007/10/03)
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- Determination of rate constants in the carbocationic polymerization of styrene: Effect of temperature, solvent polarity, and lewis acid
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The electrophilicity parameter (E = 9.6) of the 1-phenylethyl cation, 1+, has been determined and combined with the nucleophilicity parameter (N = 0.78, s = 0.95) of styrene (St) to predict diffusion-limited propagation in the cationic polymerization of St by the linear free energy relationship log k = s(N + E). This prediction has been experimentally verified using two different diffusion clock methods, which provided a value of k p± ≈ 2 × 109 L mol-1 s-1, 6 orders of magnitude higher than previously accepted, for the absolute rate constant of propagation of the TiCl4-induced polymerization of St in methyl cyclohexane/methyl chloride 60/40 (v/v) at -80°C. The kp± value remained unchanged in the temperature range -50 to -80°C, indicating that propagation does not have an enthalpic barrier; however, it increased moderately with increasing solvent polarity. The nature of the Lewis acid has little effect on kp ± as similar values have been obtained with TiCl4 or SnCl4. The apparent rate constant of ionization, k iapp, the rate constant of deactivation, k-i, and the apparent equilibrium constant of ionization, Ki app, have also been determined as a function of temperature. The kiapp increases slightly and k-i increases moderately with increasing temperature; therefore, Kiapp and the overall polymerization rate decrease moderately with increasing temperature.
- De, Priyadarsi,Faust, Rudolf,Schimmel, Holger,Ofial, Armin R.,Mayr, Herbert
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p. 4422 - 4433
(2007/10/03)
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- Direct substitution of the hydroxy group in alcohols with silyl nucleophiles catalyzed by indium trichloride
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Straightforward substitution: An excellent combination of a silyl nucleophile and indium catalyst was used to accomplish the dehydroxylation/ alkylation of alcohols under nearly neutral conditions (see scheme, Si = silyl group) even though this type of reaction usually requires at least an equimolar amount of acid.
- Yasuda, Makoto,Saito, Takahiro,Ueba, Masako,Baba, Akio
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p. 1414 - 1416
(2007/10/03)
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- InBr3-Catalyzed Deoxygenative Allylation of Benzylic and Allylic Alcohols and Acetates with Allyltrimethylsilane
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Deoxygenative allylations of benzylic and allylic alcohols and acetates with allyltrimethylsilane in the presence of a catalytic amount of InBr3 (5 mol percent) were successfully achieved in high yields.
- Kim, Sang Hee,Shin, Chul,Pae, Ae Nim,Koh, Hun Yeong,Chang, Moon Ho,Chung, Bong Young,Cho, Yong Seo
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p. 1581 - 1584
(2007/10/03)
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- B(C6F5)3-catalyzed allylation of secondary benzyl acetates with allylsilanes
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(Equation presented) A highly effective protocol for allylation of secondary benzylic alcohol derivatives with allylsilanes in the presence of catalytic amounts of B(C6F5)3 has been developed. Some additional functionalities, such as bromo, acetoxy, and primary benzyloxy groups, were tolerated under these conditions.
- Rubin, Michael,Gevorgyan, Vladimir
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p. 2705 - 2707
(2007/10/03)
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- Indium compound-catalyzed deoxygenative allylation of aromatic ketones by a hydrosilane-allylsilane system
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A combination of chlorodimethylsilane and allyltrimethylsilane effectively promoted the deoxygenative allylation of aromatic ketones in the presence of a catalytic amount of an indium compound to give the terminal alkenes. Indium trihalide or metallic indium showed high catalytic activity. (C) 2000 Elsevier Science Ltd.
- Yasuda, Makoto,Onishi, Yoshiyuki,Ito, Takeshi,Baba, Akio
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p. 2425 - 2428
(2007/10/03)
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- Radical reaction initiated and stereocontrolled by zinc chloride
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The reaction of allyltributyltin with methyl 2-[N-((4S)-4-(1-methylethyl)-2-oxazolidinone-3-carbamoyl)amino]-2-bromoacetate (5 a) was accelerated at -50°C in the presence of AIBN and stopped in the presence of galvinoxyl, indicating that the reaction proceeds through a radical mechanism. The reaction was accelerated dramatically at -78°C in the presence of ZnCl2·OEt2, and the ZnCl2-mediated reaction was stopped in the presence of galvinoxyl. In the presence of 2 equiv ZnCl2·OEt2, the reaction afforded methyl (2R)-2-[N-((4SH-(1-methylethyl)-2-oxazolidinone-3-carbamoyl)amino]-4-pentenoate {6a(R)} with high diastereoselectivity (93:7). Taken together, ZnCl2·OEt2 works as a radical initiator as well as chelating agent.
- Yamamoto, Yoshinori,Onuki, Setsuko,Yumoto, Masatoshi,Asao, Naoki
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p. 765 - 780
(2007/10/03)
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- Palladium Complexes Containing Rigid Bidentate Nitrogen Ligands as Catalysts for Carbon-Carbon Bond Formation
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Zerovalent Pd(Ar-BIAN)(dimethyl fumarate) and divalent PdCl2(Ar-BIAN) complexes containing the rigid bidentate nitrogen ligand bis(arylimino)acenaphthene (Ar-BIAN; Ar = C6H5, p-MeC6H4, p-MeOC6H4) are efficient catalysts for the cross coupling reaction of various organic halides (including acyl-, allyl-, aryl-, benzyl-, vinyl- and 1,2-dienylhalides) with organomagnesium, -zinc and -tin reagents.Coupling reactions of organic halides with one equivalent of organomagnesium and -zinc reagents, in the presence of 1 mol percent of a Pd(Ar-BIAN) catalyst, generally proceed smoothly in THF at 20 degC, giving complete conversion of the starting halide within 1-16 hours.Good isolated yields of carbon-carbon coupled products are obtained and the ratio cross/homo coupling varies between 98/2 and 0/100, depending on the substrates used.Reactions employing organotin reagents proceed best in DMF or HMPA and need longer reaction times and/or higher temperatures, as compared to organomagnesium and -zinc reagents, to go to completion.The selectivity for cross coupling is high (generally >99 percent) and high isolated yields of cross coupled products can be obtained.In the presence of carbon monoxide (1-5 bar) ketones can be formed with excellent selectivity and in good yields, as was demonstrated for the carbonylative coupling of benzyl bromide with tetramethyltin or (p-tolyl)trimethyltin.Comparison of some Pd(Ar-BIAN) catalyzed reactions with Pd-phosphine catalyzed reactions reveals that these reactions complement each other: for example, when a Pd(Ar-BIAN) catalyst was employed, the coupling of 2-methylallyl chloride with phenyltributyltin was much faster, whereas the coupling of iodobenzene with vinyltrimethyltin was much slower, as compared to the Pd(PPh3)n catalyzed reactions.
- Asselt, Rob van,Elsevier, Cornelis J.
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p. 323 - 334
(2007/10/02)
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- Relative Reactivities of Alkyl Chlorides under Friedel-Crafts Conditions
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Competition experiments have been performed to determine the relative reactivities of 23 alkyl chlorides toward allyltrimethylsilane in the presence of catalytic amounts of ZnCl2.The krel scale spans over 11 orders of magnitude from 1-adamantyl chloride (least reactive) to bis(p-methoxyphenyl)methyl chloride (most reactive compound).A fair correlation between the alkylating ability and the SN1 reactivity in solvolysis reactions is found, thus providing a quantitative basis for our long-standing working hypothesis that Lewis acid-catalyzed additions of alkyl halides to CC multiple bonds only yield 1:1 products if the reactants ionize faster than the products.Trityl chlorides do not follow this correlation and are 1E5 times less reactive than predicted from their SN1 reactivities. - Key Words: Alkylation / Allylation / Carbenium ions / Friedel-Crafts reactions / Linear free energy relationships
- Dau-Schmidt, Jan-Peter,Mayr, Herbert
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p. 205 - 212
(2007/10/02)
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- The Diastereoselectivity of Electrophilic Attack on Trigonal Carbon Adjacent to a Stereogenic Centre: Diastereoselective Protonation, Epoxidation and Acylation of Allylsilanes
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The four allylsilanes 6 and 8, which have a stereogenic centre carrying a phenyl group, a methyl group and a hydrogen atom adjacent to the nucleophilic end of the double bond, react with protic (or deuteronic) acid, m-chloroperbenzoic acid and chlorosulfonyl isocyanate to give eletrophilic substitution of the allylsilane, with diastereoselectivity in the sense 2, in conformity to a general rule for electrophilic attack on a double bond adjacent to a stereogenic centre.The most reliably stereoselective reactions took place with the allylsilane 6b, in which the stereogenic centre is cis to a group larger than a hydrogen atom in both the E- and Z-isomer.In general, chlorosulfonyl isocyanate induces higher stereoselectivity than the peracid, and the peracid higher stereoselectivity than the proton (or deuteron).
- Fleming, Ian,Lewis, Jeremy J.
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p. 3267 - 3276
(2007/10/02)
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- Reductive Alkylation/Arylation of Arylcarbinols and Ketones with Organosilicon Compounds
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Arylcarbinols react with certain organosilanes in the presence of boron trifluoride to yield hydrocarbons resulting from transfer of an R group from silicon to carbon.The transfer works well with aryl- and allylsilanes and fails with alkylsilanes.Allylation of ionizable carbinols is sometimes accompanied by cation-mediated oligomerization.This can be offset by converting the carbinols in question to their respective allyldimethylsilyl ethers followed by rearrangement of the ethers with BF3.While diaryl ketones are sluggishly bisallylated, the corresponding ketals undergo smooth bisallylation at 0 deg C with allytrimethylsilane/BF3/CH2Cl2.
- Cella, J. A.
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p. 2125 - 2130
(2007/10/02)
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- Reaction of Organoaluminium Reagents with Cyclopropylmethyl Acetates and 2-Vinylcyclopropane-1,1-dicarboxylate Esters
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Ring-opening alkylation of cyclopropylmethyl acetates was studied.The acetoxyl group of 7-(1-acetoxyheptyl)norcarane is substituted by the alkyl group upon treatment with trialkylaluminium, but alkylation of trans-1-(1-acetoxyethyl)-2-phenylcyclopropane with trialkylaluminium gives rise to trans-5-phenyl-2-alkenes.The reaction of (1S,2S)-2-phenylcyclopropylmethyl acetate with trimethylaluminium resulted in the complete loss of optical activity to give racemic 4-phenyl-1-pentene.Alkylation of trans-1-(1-acetoxy-3-phenylpropyl)-2-vinylcyclopropane with trialkylaluminium proceeds under regioselective ring-opening to give 3-alkylated trans-8-phenyl-1,5-octadiene (selectivity 73-83percent).The regio- and stereochemistry of homoconjugate addition to activated vinylcyclopropanes having a doubly carbonyl substituted ring carbon was studied.Trialkylaluminium on addition to diethyl 2-vinylcyclopropane-1,1-dicarboxylate in a 1,5-manner afford diethyl (2-alkyl-3-butenyl)propanedioate (over 96percent selectivity).In contrast, the reaction of this cyclopropane with tetraalkylaluminiumlithium takes place in a 1.7-manner to give diethyl (trans-4-alkyl-2-butenyl)propanedioate with 88-92percent selectivity.Clean regiocontrol of the reaction is observed in the methylation of ethyl exo-6-(trans-1-propenyl)-2-oxobicyclo(3.1.0>hexane-1-carboxylate with trimethylaluminium or tetramethyl aluminiumlithium.Alkylation with trimethylaluminium proceeds with 86percent inversion of the configuration at C(6) of the substrate, affording (2R*,3R*)-2-ethoxycarbonyl-3-cyclopentanone which is transformed into neonepetalactone.
- Hiyama, Tamejiro,Morizawa, Yoshitomi,Yamamoto, Hajime,Nozaki, Hitosi
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p. 2151 - 2160
(2007/10/02)
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- KINETIC RESOLUTION OF RACEMIC GRIGNARD REAGENTS BY NICKEL-CATALYZED ASYMMETRIC GRIGNARD CROSS-COUPLING
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Racemic Grignard reagents, 2-phenylpropylmagnesium chloride and 2-norbornylmagnesium chloride were kinetically resolved by asymmetric cross-coupling with vinyl bromides in the presence of chiral phosphine-nickel catalysts to give optically active coupling products (ca. 37percent ee) and carboxylic acids after carbonation with carbon dioxide.
- Hayashi, Tamio,Kanehira, Koichi,Hioki, Tsuyoshi,Kumada, Makoto
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p. 137 - 140
(2007/10/02)
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