- Palladium-Catalyzed Enantioselective Carbene Insertion into Carbon-Silicon Bonds of Silacyclobutanes
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We report herein a highly efficient palladium-catalyzed carbene insertion into strained Si-C bonds with excellent enantioselectivity, which provides a rapid and distinct method to access silacyclopentanes with a three- or four-substituted stereocenter asymmetrically. Mechanistic studies using hybrid density functional theory suggest a catalytic cycle involving oxidative addition, carbene migratory insertion, and reductive elimination. In addition, roles of the chiral ligands in controlling the reaction enantioselectivity are also elucidated.
- Huo, Jingfeng,Lan, Yu,Liu, Zhenxing,Lyu, MyeeMay,Ping, Yifan,Wang, Jianbo,Xue, Yazhen,Zhong, Kangbao
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supporting information
p. 12968 - 12973
(2021/09/03)
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- Hydroboration Reaction and Mechanism of Carboxylic Acids using NaNH2(BH3)2, a Hydroboration Reagent with Reducing Capability between NaBH4and LiAlH4
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Hydroboration reactions of carboxylic acids using sodium aminodiboranate (NaNH2[BH3]2, NaADBH) to form primary alcohols were systematically investigated, and the reduction mechanism was elucidated experimentally and computationally. The transfer of hydride ions from B atoms to C atoms, the key step in the mechanism, was theoretically illustrated and supported by experimental results. The intermediates of NH2B2H5, PhCH= CHCOOBH2NH2BH3-, PhCH= CHCH2OBO, and the byproducts of BH4-, NH2BH2, and NH2BH3- were identified and characterized by 11B and 1H NMR. The reducing capacity of NaADBH was found between that of NaBH4 and LiAlH4. We have thus found that NaADBH is a promising reducing agent for hydroboration because of its stability and easy handling. These reactions exhibit excellent yields and good selectivity, therefore providing alternative synthetic approaches for the conversion of carboxylic acids to primary alcohols with a wide range of functional group tolerance.
- Wang, Jin,Ju, Ming-Yue,Wang, Xinghua,Ma, Yan-Na,Wei, Donghui,Chen, Xuenian
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p. 5305 - 5316
(2021/04/12)
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- Photo-organocatalytic synthesis of acetals from aldehydes
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A mild and green photo-organocatalytic protocol for the highly efficient acetalization of aldehydes has been developed. Utilizing thioxanthenone as the photocatalyst and inexpensive household lamps as the light source, a variety of aromatic and aliphatic aldehydes have been converted into acyclic and cyclic acetals in high yields. The reaction mechanism was extensively studied.
- Nikitas, Nikolaos F.,Triandafillidi, Ierasia,Kokotos, Christoforos G.
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supporting information
p. 669 - 674
(2019/02/14)
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- Aryl Boronic Acid Catalysed Dehydrative Substitution of Benzylic Alcohols for C?O Bond Formation
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A combination of pentafluorophenylboronic acid and oxalic acid catalyses the dehydrative substitution of benzylic alcohols with a second alcohol to form new C?O bonds. This method has been applied to the intermolecular substitution of benzylic alcohols to form symmetrical ethers, intramolecular cyclisations of diols to form aryl-substituted tetrahydrofuran and tetrahydropyran derivatives, and intermolecular crossed-etherification reactions between two different alcohols. Mechanistic control experiments have identified a potential catalytic intermediate formed between the aryl boronic acid and oxalic acid.
- Estopi?á-Durán, Susana,Donnelly, Liam J.,Mclean, Euan B.,Hockin, Bryony M.,Slawin, Alexandra M. Z.,Taylor, James E.
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supporting information
p. 3950 - 3956
(2019/02/16)
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- Method for synthesizing alkyne through catalytic asymmetric cross coupling (by machine translation)
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The invention belongs to the field of, asymmetric synthesis, and discloses a method for catalyzing asymmetric cross- coupling to synthesize: an alkyne, and the L method comprises, the following steps, of A: preparing B a cuprous, salt and C a: ligand; preparing a catalyst; adding a base; reacting the compound with the compound with the compound; and reacting the compound with the compound. Of these, one of them, X is selected from the group consisting of, R halogens. 1 Optionally substituted heteroarylsulfonylcyanamide groups selected from the, group consisting, of optionally substituted, phenyl groups In-flight vehicle, R6 Trialkyl silyl groups or alkyl radicals, R2 Cycloalkyl radicals optionally substituted with an, optionally substituted alkyl, (CH radical2 )n R4 Multi,layer chain, n=0-10,R saw blade4 A group selected, from, the group consisting of phenyl, alkenyl, aralkynyls, noonyloxy,and, noonylsulfonylsulfonylsulfonylsulfonylsulfonylsulfonylsulfonylsulfonylsulfonylsulphonylsulphonylsulphonylsulphonylsulphonylsulphonylsulphonylsulphonylsulphonylsulphonylphenyl disiloxy-radicals. R3 A ligand, selected from hydrogen or any of the functional groups, is selected from the group consisting of, hydrogen and any L other functional group. The method, R disclosed by the, A invention has the, advantages of good catalytic, R ’ effect, wide application range. and high catalytic efficiency, and the, method disclosed by the, invention has the. advantages of good catalytic effect, wide application range and high catalytic efficiency. (by machine translation)
- -
-
Paragraph 0366
(2020/01/12)
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- Synthesis of Enantiopure γ-Lactones via a RuPHOX-Ru Catalyzed Asymmetric Hydrogenation of γ-Keto Acids
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A RuPHOX?Ru catalyzed asymmetric hydrogenation of γ-keto acids has been developed, affording the corresponding enantiopure γ-lactones in high yields and with up to 97% ee. The reaction could be performed on a gram scale with a relatively low catalyst loading (up to 10000 S/C) under the indicated reaction conditions and the resulting products can be transformed to several enantiopure building blocks, biologically active compounds and enantiopure drugs. (Figure presented.).
- Li, Jing,Ma, Yujie,Lu, Yufei,Liu, Yangang,Liu, Delong,Zhang, Wanbin
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p. 1146 - 1153
(2019/01/30)
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- Chemoselectivity Control in the Asymmetric Hydrogenation of γ- and δ-Keto Esters into Hydroxy Esters or Diols
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The asymmetric hydrogenation of aromatic γ- and δ-keto esters into optically active hydroxy esters or diols under the catalysis of a novel DIPSkewphos/3-AMIQ–RuII complex was studied. Under the optimized conditions (8 atm H2, Ru complex/t-C4H9OK=1:3.5, 25 °C) the γ- and δ-hydroxy esters (including γ-lactones) were obtained quantitatively with 97–99 % ee. When the reaction was conducted under somewhat harsh conditions (20 atm H2, [t-C4H9OK]=50 mm, 40 °C), the 1,4- and 1,5-diols were obtained predominantly with 95–99 % ee. The reactivity of the ester group was notably dependent on the length of the carbon spacer between the two carbonyl moieties of the substrate. The reaction of β- and ?-keto esters selectively afforded the hydroxy esters regardless of the reaction conditions. This catalyst system was applied to the enantioselective and regioselective (for one of the two ester groups) hydrogenation of a γ-?-diketo diester into a trihydroxy ester.
- Arai, Noriyoshi,Namba, Takanori,Kawaguchi, Kei,Matsumoto, Yuki,Ohkuma, Takeshi
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supporting information
p. 1386 - 1389
(2018/01/01)
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- Lewis Base-Promoted Ring-Opening 1,3-Dioxygenation of Unactivated Cyclopropanes Using a Hypervalent Iodine Reagent
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A facile and effective system has been developed for the regio- and chemoselective ring-opening/electrophilic functionalization of cyclopropanes through C?C bond activation by [bis(trifluoroacetoxy)iodo]benzene with the aid of the Lewis basic promoter p-toluenesulfonamide. The p-toluenesulfonamide-promoted system works well for a wide range of cyclopropanes, resulting in the formation of 1,3-diol products in good yields and regioselectivity.
- Gieuw, Matthew H.,Ke, Zhihai,Yeung, Ying-Yeung
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supporting information
p. 3782 - 3786
(2018/03/13)
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- Pd-Catalyzed debenzylation and deallylation of ethers and esters with sodium hydride
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Herein we demonstrate simply that the addition of Pd(OAc)2 as a promotor switches the reactivity of a commonly used base NaH to a nucleophilic reductant. The reactivity is engineered into a palladium-catalyzed reductive debenzylation and deallylation of aryl ethers and esters. This operationally simple, mild protocol displays a broad substrate scope and a broad spectrum of functional group tolerance (>50 examples) and high chemoselectivity toward aryl ethers over aliphatic structures. Moreover, the dual reactivity of NaH as a base and a reductant is demonstrated in efficient synthetic elaboration.
- Mao, Yujian,Liu, Ye,Hu, Yanwei,Wang, Liang,Zhang, Shilei,Wang, Wei
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p. 3016 - 3020
(2018/04/14)
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- Photocatalysis with Quantum Dots and Visible Light: Selective and Efficient Oxidation of Alcohols to Carbonyl Compounds through a Radical Relay Process in Water
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Selective oxidation of alcohols to aldehydes/ketones has been achieved with the help of 3-mercaptopropionic acid (MPA)-capped CdSe quantum dot (MPA-CdSe QD) and visible light. Visible-light-prompted electron-transfer reaction initiates the oxidation. The thiyl radical generated from the thiolate anion adsorbed on a CdSe QD plays a key role by abstracting the hydrogen atom from the C?H bond of the alcohol (R1CH(OH)R2). The reaction shows high efficiency, good functional group tolerance, and high site-selectivity in polyhydroxy compounds. The generality and selectivity reported here offer a new opportunity for further applications of QDs in organic transformations.
- Zhao, Lei-Min,Meng, Qing-Yuan,Fan, Xiang-Bing,Ye, Chen,Li, Xu-Bing,Chen, Bin,Ramamurthy, Vaidhyanathan,Tung, Chen-Ho,Wu, Li-Zhu
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supporting information
p. 3020 - 3024
(2017/03/13)
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- Cyclic ether synthesis from diols using trimethyl phosphate
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Cyclic ethers have been effectively synthesized via the intramolecular cyclization of diols using trimethyl phosphate and NaH. The present cyclization could proceed at room temperature to produce 5-7 membered cyclic ethers in good to excellent yields. Substrates possessing a chiral secondary hydroxy group were transformed into the corresponding chiral cyclic ethers along with the retention of their stereochemistries.
- Asai, Shota,Kato, Maho,Monguchi, Yasunari,Sajiki, Hironao,Sawama, Yoshinari
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p. 4787 - 4790
(2017/07/06)
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- Stereoselective organocatalytic oxidation of alcohols to enals: A homologation method to prepare polyenes
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A novel method for organocatalytic oxidation through oxidative enamine catalysis was developed with excellent compatibility for the direct syntheses of enals from simple saturated alcohols. By using this amine-catalyzed IBX-oxidation, a wide range of aromatic and aliphatic substituted enals were successfully generated in high yields and exclusively stereoselective E-geometry. Moreover, varying the solvents and/or the loading amounts of IBX allowed for the selective oxidation of alcohols and aldehydes. Importantly, the homologous application of this method provided a selective and efficient way of preparing various highly sensitive conjugated polyene frameworks, which are enriched in natural products.
- Chen, Xiaobei,Zhang, Yinan,Wan, Huixin,Wang, Wei,Zhang, Shilei
-
supporting information
p. 3532 - 3535
(2016/03/04)
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- Chelating Bis(1,2,3-triazol-5-ylidene) Rhodium Complexes: Versatile Catalysts for Hydrosilylation Reactions
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NHC-rhodium complexes (NHC=N-heterocyclic carbenes) have been widely used as efficient catalysts for hydrosilylation reactions. However, the substrates were mostly limited to reactive carbonyl compounds (aldehydes and ketones) or carbon-carbon multiple bonds. Here, we describe the application of newly-developed chelating bis(tzNHC)-rhodium complexes (tz=1,2,3-triazol-5-ylidene) for several reductive transformations. With these catalysts, the formal reductive methylation of amines using carbon dioxide, the hydrosilylation of amides and carboxylic acids, and the reductive alkylation of amines using carboxylic acids have been achieved under mild reaction conditions.
- Nguyen, Thanh V. Q.,Yoo, Woo-Jin,Kobayashi, Shu
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supporting information
p. 452 - 458
(2016/02/12)
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- Hydroxy-directed, fluoride-catalyzed epoxide hydrosilylation for the synthesis of 1,4-diols
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Abstract A novel highly regioselective, fluoride-catalyzed hydrosilylation of β-hydroxy epoxides has been developed. The reaction is modular and applicable to the synthesis of a broad range of 1,4-diols. Fluoride is crucial for two reasons: First, it promotes the formation of a silyl ether (which contains a Si-H bond) and, second, it enables ring opening by an intramolecular SN2 reaction through activation of the silane. The reaction can be performed under air. A modular, convergent, and stereoselective synthesis of 1,4-diols by epoxide hydrosilylation has been developed (see scheme). The reaction occurs under fluoride catalysis, is high yielding, highly regioselective, and can be carried out on a large scale.
- Zhang, Yong-Qiang,Funken, Nico,Winterscheid, Peter,Gans?uer, Andreas
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p. 6931 - 6934
(2015/06/08)
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- Iridium-Catalyzed C-C Coupling of a Simple Propargyl Ether with Primary Alcohols: Enantioselective Homoaldol Addition via Redox-Triggered (Z)-Siloxyallylation
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A chiral iridium complex formed in situ from [Ir(cod)Cl]2 and (R)-H8-BINAP is found to catalyze the direct enantioselective C-C coupling of a simple propargyl ether, TIPSOCH2C-CH, with primary alcohols to form γ-hydroxy (Z)-enol silanes with uniformly high enantioselectivity and complete alkene (Z)-stereoselectivity. As corroborated by deuterium labeling studies, these studies represent the first examples of 1,2-hydride shift-enabled π-allyl formation in the context of iridium catalysis.
- Liang, Tao,Zhang, Wandi,Krische, Michael J.
-
supporting information
p. 16024 - 16027
(2016/01/15)
-
- Br?nsted Acid-Catalyzed Intramolecular Nucleophilic Substitution of the Hydroxyl Group in Stereogenic Alcohols with Chirality Transfer
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The hydroxyl group of enantioenriched benzyl, propargyl, allyl, and alkyl alcohols has been intramolecularly displaced by uncharged O-, N-, and S-centered nucleophiles to yield enantioenriched tetrahydrofuran, pyrrolidine, and tetrahydrothiophene derivatives with phosphinic acid catalysis. The five-membered heterocyclic products are generated in good to excellent yields, with high degree of chirality transfer, and water as the only side-product. Racemization experiments show that phosphinic acid does not promote SN1 reactivity. Density functional theory calculations corroborate a reaction pathway where the phosphinic acid operates as a bifunctional catalyst in the intramolecular substitution reaction. In this mechanism, the acidic proton of the phosphinic acid protonates the hydroxyl group, enhancing the leaving group ability. Simultaneously, the oxo group of phosphinic acid operates as a base abstracting the nucleophilic proton and thus enhancing the nucleophilicity. This reaction will open up new atom efficient techniques that enable alcohols to be used as nucleofuges in substitution reactions in the future.
- Bunrit, Anon,Dahlstrand, Christian,Olsson, Sandra K.,Srifa, Pemikar,Huang, Genping,Orthaber, Andreas,Sj?berg, Per J. R.,Biswas, Srijit,Himo, Fahmi,Samec, Joseph S. M.
-
supporting information
p. 4646 - 4649
(2015/04/27)
-
- Enantioselective 1,1-arylborylation of alkenes: Merging chiral anion phase transfer with pd catalysis
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A palladium-catalyzed three-component coupling of α-olefins, aryldiazonium salts, and bis(pinacolato)diboron affords direct access to chiral benzylic boronic esters. This process is rendered highly enantioselective using an unprecedented example of cooperative chiral anion phase transfer and transition-metal catalysis.
- Nelson, Hosea M.,Williams, Brett D.,Miró, Javier,Toste, F. Dean
-
supporting information
p. 3213 - 3216
(2015/03/30)
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- METHOD FOR MANUFACTURING ALCOHOL BY HYDROGENATION OF CARBOXYLIC ACID COMPOUND AND ESTER COMPOUND
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PROBLEM TO BE SOLVED: To provide a method for obtaining alcohol by hydrogenation of carboxylic acid compound efficiently by using a homogeneous system catalyst, especially a method for obtaining alcohol by hydrogenation of various carboxylic acid compound and ester compound by the homogeneous system catalyst efficiently even under alleviation condition. SOLUTION: A carboxylic acid compound and/or an ester compound is hydrogenated in a presence of a rhenium complex represented by ReXmYnZp, where X is a halogen atom, Y is same or different and each a ligand containing one or more phosphorus atom, Z is a ligand other than X and Y, m is an integer of 1 to 6, p is an integer of 0 to 2 and the sum of m, n and p is an integer of 2 to 6, and a specific alkali metal salt. COPYRIGHT: (C)2015,JPOandINPIT
- -
-
Paragraph 0117; 0118; 0127; 0129; 0130
(2016/10/10)
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- Synthesis of oxacyclic scaffolds via dual ruthenium hydride/Bronsted acid-catalyzed isomerization/cyclization of allylic ethers
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A ruthenium hydride/Bronsted acid-catalyzed tandem sequence is reported for the synthesis of 1,3,4,9-tetrahydropyrano[3,4-b]indoles (THPIs) and related oxacyclic scaffolds. The process was designed on the premise that readily available allylic ethers would undergo sequential isomerization, first to enol ethers (Ru catalysis), then to oxocarbenium ions (Bronsted acid catalysis) amenable to endo cyclization with tethered nucleophiles. This methodology provides not only an attractive alternative to the traditional oxa-Pictet-Spengler reaction for the synthesis of THPIs, but also convenient access to THPI congeners and other important oxacycles such as acetals.
- Ascic, Erhad,Ohm, Ragnhild G.,Petersen, Rico,Hansen, Mette R.,Hansen, Casper L.,Madsen, Daniel,Tanner, David,Nielsen, Thomas E.
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supporting information
p. 3297 - 3300
(2014/04/03)
-
- Laccase/2,2,6,6-tetramethylpiperidinoxyl radical (TEMPO): An efficient catalytic system for selective oxidations of primary hydroxy and amino groups in aqueous and biphasic media
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Copper salts/2,2,6,6-tetramethylpiperidinoxyl radical (TEMPO) catalytic systems enable efficient aerobic oxidations of primary alcohols but they generally show a reduced reactivity in aqueous medium. Herein, we report an oxidative catalytic system composed of Trametes versicolor laccase and TEMPO, which is able to work in buffer solutions at room temperature using ambient air. Although this catalytic system displays great efficiency in aqueous systems, the addition of methyl tert-butyl ether allows the reduction of TEMPO loading, also enhancing the solubility of hydrophobic compounds. This practical methodology promotes the chemoselective aerobic oxidation of hydroxy or amino groups, leading to interesting organic derivatives such as aldehydes, lactones, hemiaminals or lactams.
- Díaz-Rodríguez, Alba,Martínez-Montero, Lía,Lavandera, Iván,Gotor, Vicente,Gotor-Fernández, Vicente
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supporting information
p. 2321 - 2329
(2014/07/21)
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- Ketyl-type radicals from cyclic and acyclic esters are stabilized by SmI2(H2O)n: the role of SmI2(H 2O)n in post-electron transfer steps
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Mechanistic details pertaining to the SmI2-H2O- mediated reduction and reductive coupling of 6-membered lactones, the first class of simple unactivated carboxylic acid derivatives that had long been thought to lie outside the reducing range of SmI2, have been elucidated. Our results provide new experimental evidence that water enables the productive electron transfer from Sm(II) by stabilization of the radical anion intermediate rather than by solely promoting the first electron transfer as originally proposed. Notably, these studies suggest that all reactions involving the generation of ketyl-type radicals with SmI2 occur under a unified mechanism based on the thermodynamic control of the second electron transfer step, thus providing a blueprint for the development of a broad range of novel chemoselective transformations via open-shell electron pathways.
- Szostak, Michal,Spain, Malcolm,Procter, David J.
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supporting information
p. 8459 - 8466
(2014/06/24)
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- Concise, stereodivergent and highly stereoselective synthesis of cis-and trans-2-substituted 3-hydroxypiperidines-development of a phosphite-driven cyclodehydration
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A concise (5 to 6 steps), stereodivergent, highly diastereoselective (dr up to >19:1 for both stereoisomers) and scalable synthesis (up to 14 g) of cis- and trans-2-substituted 3-piperidinols, a core motif in numerous bioactive compounds, is presented. This sequence allowed an efficient synthesis of the NK-1 inhibitor L-733,060 in 8 steps. Additionally, a cyclodehydration-realizing simple triethylphosphite as a substitute for triphenylphosphine is developed. Here the stoichiometric oxidized P(V)-byproduct (triethylphosphate) is easily removed during the work up through saponification overcoming separation difficulties usually associated to triphenylphosphine oxide.
- Huy, Peter H.,Westphal, Julia C.,Koskinen, Ari M.P.
-
supporting information
p. 369 - 383
(2014/03/21)
-
- Selective synthesis of unsymmetrical ethers from different alcohols catalyzed by sodium bisulfite
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An efficient method for the preparation of unsymmetrical ethers from alcohols catalyzed by sodium bisulfite is reported. The procedure enables the direct dehydration of primary, secondary, and tertiary benzylic alcohols with aliphatic alcohols in the abse
- Yu, Jun-Lai,Wang, Hui,Zou, Kai-Feng,Zhang, Jia-Rui,Gao, Xiang,Zhang, Dan-Wei,Li, Zhan-Ting
-
supporting information
p. 310 - 315
(2013/01/15)
-
- Catalytic asymmetric hydrogenation of δ-ketoesters: Highly efficient approach to chiral 1,5-diols
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High turnover: An highly efficient catalytic asymmetric hydrogenation of δ-aryl-δ-ketoesters has been realized by using the chiral spiroiridium catalyst (R)-1. Chiral 1,5-diol products are obtained with excellent enantioselectivity and turnover numbers (TONs) as high as 100 000. TOF=turnover frequency. Copyright
- Yang, Xiao-Hui,Xie, Jian-Hua,Liu, Wei-Peng,Zhou, Qi-Lin
-
supporting information
p. 7833 - 7836
(2013/08/23)
-
- Bronsted acid catalyzed asymmetric SN2-Type O-alkylations
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Bridging the gap: Bronsted acids catalyze an intramolecular S N2-type alkylation of alcohols with ethers by bridging a pentacoordinate transition state, thus simultaneously activating both the leaving group and nucleophile (see scheme). Density functional calculations provide detailed insight into the course of the reaction and the transition-state structure.
- Coric, Ilija,Kim, Ji Hye,Vlaar, Tjostil,Patil, Mahendra,Thiel, Walter,List, Benjamin
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supporting information
p. 3490 - 3493
(2013/05/09)
-
- Methods for the synthesis of chiral sulfur heterocycles and their application in the asymmetric Baylis-Hillman reactions
-
Enantiomerically pure (2S,6S)-2,6-diphenyltetrahydro-2H-thiopyran, (2S)-2-phenyltetrahydro thiophene, and (2S)-2-phenyltetrahydro-2H-thiopyran were prepared in 70-72% yields and with 86-99% ee via cyclization of the corresponding dimesylate in an SN2 cyclization reaction using sodium sulfide nonahydrate. The results on the application of various chiral sulfides in asymmetric Baylis-Hillman reactions are also described.
- Periasamy, Mariappan,Gurubrahamam, Ramani,Muthukumaragopal, Gopal P.
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p. 568 - 574
(2013/06/27)
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- Efficient, stereodivergent access to 3-piperidinols by traceless P(OEt)3 cyclodehydration
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A stereodivergent and highly diastereoselective (dr up to >19:1 for both isomers), step economic (5-6 steps), and scalable synthesis (up to 14 g) of cis- and trans-2-substituted 3-piperidinols, the core motif of numerous bioactive compounds, providing efficient access to the NK-1 inhibitor L-733,060 is presented. Additionally, a "traceless" (referring to the simplified byproduct separation) cyclodehydration realizing simple P(OEt)3 as a substitute for PPh3 is developed.
- Huy, Peter H.,Koskinen, Ari M. P.
-
supporting information
p. 5178 - 5181
(2013/11/06)
-
- Ligand-controlled, norbornene-mediated, regio- and diastereoselective rhodium-catalyzed intramolecular alkene hydrosilylation reactions
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Ligand-controlled, norbornene-mediated, regio- and diastereoselective rhodium-catalyzed intramolecular alkene hydrosilylation of homoallyl silyl ethers (1) exploiting either BINAP or 1,6-bis(diphenylphosphino)hexane (dpph) has been developed. This method
- Hua, Yuanda,Nguyen, Hiep H.,Scaggs, William R.,Jeon, Junha
-
supporting information
p. 3412 - 3415
(2013/07/26)
-
- One-pot asymmetric synthesis of 2-and 2,3-disubstituted tetrahydrofuran derivatives
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A novel and convenient one-pot asymmetric synthesis of 2- and 2,3-disubstituted tetrahydrofurans has been achieved in 56-81% yields and 86-99% ee from aliphatic and aromatic aldehydes via an allyl/crotyl/ alkoxyallylboration-hydroboration-iodination-cyclization reaction sequence.
- Ramachandran, P. Veeraraghavan,Nair, Hari N. G.,Gagare, Pravin D.
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p. 5394 - 5398
(2012/08/07)
-
- Highly enantioselective synthesis of chiral allenes by sequential creation of stereogenic center and chirality transfer in a single pot operation
-
Chiral allenes are readily accessed in a single pot operation in the reaction of terminal alkynes, aldehydes, chiral secondary amines, and zinc halides in good yields (up to 77% yield) and excellent enantioselectivities (up to 99% ee) in toluene at 120 °C. The reaction proceeds through initial formation of chiral propargylamine intermediates with creation of a new stereogenic center and subsequent chirality transfer via an intramolecular hydride shift to produce chiral allenes with high enantiomeric purities.
- Periasamy, Mariappan,Sanjeevakumar, Nalluri,Dalai, Manasi,Gurubrahamam, Ramani,Reddy, Polimera Obula
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supporting information; scheme or table
p. 2932 - 2935
(2012/08/28)
-
- Nickel-catalyzed reductive cyclization of organohalides
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A mild and convenient nickel-catalyzed method for free-radical cyclization of organohalides is described. The use of a NiCl2DME/Pybox complex as the catalyst and zinc powder in methanol efficiently promotes the reductive cyclization of various
- Kim, Hyejin,Lee, Chulbom
-
supporting information; experimental part
p. 2050 - 2053
(2011/06/25)
-
- Cyclopropenium-activated cyclodehydration of diols
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The dehydrative cyclization of diols to cyclic ethers via cyclopropenium activation is described. Using 2,3-diphenylcyclopropene and methanesulfonic anhydride, a series of 1,4-and 1,5-diols are rapidly cyclized to furnish tetrahydrofurans and tetrahydropyrans in high yield. Eleven total substrates are shown, including a gram scale cyclization of a diterpene derivative.
- Kelly, Brendan D.,Lambert, Tristan H.
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supporting information; experimental part
p. 740 - 743
(2011/05/04)
-
- Systematic investigations on the reduction of 4-aryl-4-oxoesters to 1-aryl-1,4-butanediols with methanolic sodium borohydride
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4-Aryl-4-oxoesters undergo facile reduction of both the keto and the ester groups with methanolic NaBH4 at room temperature to yield the corresponding 1-aryl-1,4-butanediols whereas 4-alkyl-4-oxoesters furnish the corresponding 1,4-butanolides via selective reduction of the keto moiety. Results of a detailed and systematic investigation of the reaction are described.
- Chaudhuri, Subrata Kumar,Saha, Manabendra,Saha, Amit,Bhar, Sanjay
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supporting information; experimental part
p. 748 - 755
(2011/01/03)
-
- Gold-catalysed cyclic ether formation from diols
-
Gold(I) and (III) salts have been found to be highly effective at the catalysis of ether formation from alcohols. Intramolecular ether formation of a 1,5-diol was also achieved, with a stereoselectivity that indicates that an SN1 mechanism predominates. In an attempt to form a seven-membered ring, a stable 14-membered dimer product was also formed. Attempts to control the diastereoselectivity of the reaction using a chiral anionic counterion did not give products with a high de.
- Jiang, Xiaolu,London, Emma K.,Morris, David J.,Clarkson, Guy J.,Wills, Martin
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experimental part
p. 9828 - 9834
(2011/02/23)
-
- Reduction of aromatic and aliphatic keto esters using sodium borohydride/MeOH at room temperature: a thorough investigation
-
Reduction of keto esters is a valuable alternative to produce diols. Sodium borohydride/MeOH system at room temperature and short reaction time efficiently reduced α, β, γ, and δ-keto esters having α-keto esters as the most reactive. The ester functionality was reduced effectively due to the presence of oxo group that somehow facilitates the formation of ring intermediate. As expected, the chemoselective experiments showed that ester functionality was not reduced using this system. This study presents a simple, easy, and benign reduction process of various keto esters to its corresponding diols.
- Kim, Juryoung,De Castro, Kathlia A.,Lim, Minkyung,Rhee, Hakjune
-
supporting information; experimental part
p. 3995 - 4001
(2010/07/05)
-
- Chromium-catalyzed homoaldol equivalent reaction employing a nucleophilic propenyl acetate
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A scalable, highly regioselective chromium-catalyzed homoaldol equivalent reaction employing 3-bromopropenyl acetate as a masked homoenolate nucleophile in additions to aromatic, aliphatic, and α,β-unsaturated aldehydes under mild Cr/Mn redox conditions in good to excellent yields is reported. The resulting vinyl acetate-containing adducts are easily hydrolyzed with mild base to provide formal homoaldol adducts, or transformed to other more functionalized products by stereoselective transformations including epoxidation and cyclopropanation.
- Kang, Jun Yong,Connell, Brian T.
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supporting information; experimental part
p. 7826 - 7827
(2010/08/04)
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- Selective synthesis of secondary and tertiary amines by Cp*iridium-catalyzed multialkylation of ammonium salts with alcohols
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(Chemical Equation Presented) The efficient selective synthesis of secondary and tertiary amines has been achieved by means of Cp*Ir- catalyzed multialkylation of ammonium salts with alcohols without solvent: the reactions of ammonium acetate with alcohols gave tertiary amines exclusively, while those of ammonium tetrafluoroborate afforded secondary amines selectively. Using this method, secondary 5- and 6-membered cyclic amines were synthesized from ammonium tetrafluoroborate and diols in one pot.
- Yamaguchi, Ryohei,Kawagoe, Shoko,Asai, Chiho,Fujita, Ken-Ichi
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p. 181 - 184
(2008/09/18)
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- Enantioselective Claisen rearrangements with a hydrogen-bond donor catalyst
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N,N-Diphenylguanidinium ion associated with the noncoordinating BArF counterion is shown to be an effective catalyst for the [3,3]-sigmatropic rearrangement of a variety of substituted allyl vinyl ethers. Highly enantioselective catalytic Claisen rearrangements of ester-substituted allyl vinyl ethers are then documented using a new C2-symmetric guanidinium ion derivative. Copyright
- Uyeda, Christopher,Jacobsen, Eric N.
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supporting information; body text
p. 9228 - 9229
(2009/02/03)
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- Grignard reagents: Alkoxide-directed iodine-magnesium exchange at sp 3 centers
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(Chemical Equation Presented) Sequential addition of i-PrMgCl and BuLi to sp3 hybridized iodoalcohols triggers a facile iodine-metal exchange. Intercepting the resulting cyclic Grignard reagents with a slight excess of an electrophile leads to a diverse range of substituted alcohols. The iodine-magnesium exchange strategy is effective with 3-carbon iodoalcohols bearing alkyl substitutents on the carbinol or adjacent carbons and with the chain-extended homolog 4-iodobutan-1-ol.
- Fleming, Fraser F.,Gudipati, Subrahmanyam,Vu, Viet Anh,Mycka, Robert J.,Knochel, Paul
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p. 4507 - 4509
(2008/03/11)
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- Dod-S-Me and methyl 6-morpholinohexyl sulfide (MMS) as new odorless borane carriers
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Odorless Dod-S-Me (1) and MMS (3) are developed as efficient borane carriers. The yields of hydroborations and reductions with borane complex 2 of 1 are very high and the recovery of 1 after the reaction is quantitative. The borane complexes 4 and 5 of 3 are also useful. In the latter case chromatographic separation is unnecessary when excess oxidizing agent (alkaline H2O2) is used after hydroboration.
- Patra, Pranab K.,Nishide, Kiyoharu,Fuji, Kaoru,Node, Manabu
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p. 1003 - 1006
(2007/10/03)
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- Application of a one-pot lipase resolution strategy for the synthesis of chiral γ- and δ-lactones
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A successful one-pot reduction of γ-ketoesters, δ-ketoesters and lactones to the corresponding 1,4- and 1,5-diols followed by a lipase catalyzed kinetic resolution coupled with hydrolysis to afford optically active diols is described. The synthetic utility of this one-pot method was illustrated by the oxidation of these chiral diols to respective chiral γ-butyrolactone and δ-lactones. Lipase from Pseudomonas cepacia, immobilized on ceramic afforded the product with high enantiomeric excess in good yields under mild reaction conditions. This approach has been used to develop a convenient enantioselective route for several γ- and δ-lactones using achiral and corresponding racemic starting material.
- Kamal, Ahmed,Sandbhor, Mahendra,Shaik, Ahmad Ali
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p. 1575 - 1580
(2007/10/03)
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- Conversion of (Z)-1,4-dihydroxyalk-2-enes into 2,5-dihydrofurans and of alkane-1,4-diols into tetrahydrofurans via acid-catalysed cyclisation of the monoisoureas formed by their copper(I)-mediated reactions with dicyclohexylcarbodiimide
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(Z)-1,4-dihydroxyalk-2-enes were converted into 2,5-dihydrofurans and alkane-1,4-diols were converted into tetrahydrofurans via acid-catalysed cyclisation of the monoisoureas. The reaction involved protonation of the carbodiimide by acidic phenol followed by reaction with alkanol. Pd/CaCo3-quinoline catalyst system was employed in the presence of a little triethylamine to overcome partial hydrogenolysis.
- Duffy, Michael G.,Grayson, David H.
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p. 1555 - 1563
(2007/10/03)
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- Direct reduction of alcohols: Highly chemoselective reducing system for secondary or tertiary alcohols using chlorodiphenylsilane with a catalytic amount of indium trichloride
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The direct reduction of alcohols using chlorodiphenylsilane as A hydride source in the presence of a catalytic amount of indium trichloride is described. Benzylic alcohols, secondary alcohols, and tertiary alcohols were effectively reduced to give the corresponding alkanes in high yields. A compound bearing both primary and secondary hydroxyl groups was reduced only at the secondary site to afford the primary alcohol after workup with Bu4NF. This system showed high chemoselectivity only for the hydroxyl group while not reducing other functional groups that are readily reduced by standard reducing systems. Thus alcohols bearing ester, chloro, bromo, or nitro groups, which are sensitive to LiAlH4 or Zn/H+, were selectively reduced only at the hydroxyl sites by the chlorodiphenylsilane/InCl3 system. NMR studies revealed the reaction course. The hydrodiphenyl-silyl ether is initially formed and then, with InCl3 acting as a Lewis acid, forms an oxonium complex, which accelerates the desiloxylation with donation of the hydrogen to the carbon.
- Yasuda,Onishi,Ueba,Miyai,Baba
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p. 7741 - 7744
(2007/10/03)
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- Elevation of HDL cholesterol by 4-[(aminothioxomethyl)hydrazono]-4-arylbutyl carbamates
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This invention relates to the treatment of atherosclerosis via raising the level of HDL cholesterol by administration of a compound of the formula STR1 wherein R1, R2, and R3 are independently hydrogen, C1 -Csu
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- Pseudo-macrocyclic chelation control in remote asymmetric induction. Highly efficient 1,7-asymmetric inductive hydride reduction and Grignard reaction of γ-keto esters of 1,1′-binaphthalen-2-ols bearing an appropriate oligoether group as the 2′-substituent
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Highly efficient 1,7-asymmetric induction was achieved in DIBAL-H reduction and Grignard reaction of γ-keto esters of podand-type 1,1′-binaphthalen-2-ol derivatives bearing an appropriate oligoether group as the 2′-substituent. Thus, the DIBAL-H reduction of keto esters 4 in dichloromethane-toluene at -78°C in the presence of an excess of MgBr2·OEt2 afforded, after further, reduction of the resulting diastereomeric hydroxy esters, 1,4-diol 8 with up to 92% optical yield. A similar treatment of keto esters 4, 5 and 7 with Grignard reagents gave the corresponding 4,4-disubstituted butan-4-olides 10-13 with up to 99% optical yield. The complexation experiments of keto ester 4b suggested that the highly efficient 1,7-asymmetric induction originated from the formation of a pseudo-macrocyclic magnesium complex composed of the podand keto ester and MgBr2.
- Tamai, Yasufumi,Hattori, Tetsutaro,Date, Masamitsu,Koike, Shinji,Kamikubo, Yoshinori,Akiyama, Masahiro,Seino, Kazuhiro,Takayama, Hideki,Oyama, Tomohito,Miyano, Sotaro
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p. 1685 - 1694
(2007/10/03)
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- Synthesis of benzanilide derivatives as dual acting agents with α1- adrenoceptor antagonistic action and steroid 5-α reductase inhibitory activity
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Synthesis of benzanilide derivatives which have dual α1-adrenoceptor antagonistic action and steroid 5α-reductase inhibitory activity and their structure-activity relationships is described.
- Yoshida, Kiyoshi,Horikoshi, Yoichiro,Eta, Masaaki,Chikazawa, Jun,Ogishima, Masayuki,Fukuda, Yohichi,Sato, Hiroki
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p. 2967 - 2972
(2007/10/03)
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- Regioselective nucleophilic ring opening of epoxides and aziridines derived from homoallylic alcohols
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The regioselectivity of nuclcopbilic ring opening of some 3,4-epoxy and 3,4-aziridino alcohols has been studied. The nucleophiles chosen were complex hydrides (LiAlH4, Red-Al and DIBAL) and Lipshutz- or Gilman-type organocuprate reagents. The C-4 substituent in the substrates was varied in order to study steric and electronic effects on the ring opening reactions. For alkyl substituents at C-4, most of the results can be explained on the basis of intramolecular delivery of the nucleophile to C-3 via a six-membered transition state, leading to 1,4-diols or 1,4-amine alcohol derivatives. In general, the epoxy alcohols gave poorer regioselectivity than the N-tosyl aziridino alcohols, for which selectivities of >95:5 were routinely obtained. The activating effect of a phenyl group at C-4 led to a switch in regiochemistry, with the 1,3-diol or 1,3-amino alcohol derivative as the major product.
- Tanner, David,Groth, Thomas
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p. 16139 - 16146
(2007/10/03)
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- Chemoselective oxidation of organozine reagents with oxygen
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Functionalized organozinc compounds prepared by hydrozincation, carbozincation or by boron-zinc exchange can be directly oxidized in a selective manner to the corresponding functionalized alcohols or hydroperoxides depending on the reaction conditions.
- Klement, Ingo,Luetjens, Henning,Knochel, Paul
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p. 9135 - 9144
(2007/10/03)
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- Process for the production of cyclic sulfonium salts
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A process for the production of a 5-7 membered ring cyclic sulfonium salt compound, including a 5-7 membered ring cyclic sulfonium salt compound having a non-nucleophilic anion, is described. Members of the latter group are potentially useful as initiators for cationic polymerizations. The process comprises reacting a 1.4-, 1.5-, or 1.6-diol compound or a 5-7 membered ring cyclic ether compound with a mercapto compound and a strong protonic acid yielding the cyclic sulfonium salt compound. Some compounds described are also novel compounds per se.
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- Oxidation of zinc organometallics prepared by hydrozincation or carbozincation using oxygen
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Organozinc compounds prepared by the hydrozincation or carbazincation of functionalized unsaturated molecules can be directly oxidized by oxygen affording alcohols after reductive workup in satisfactory yields.
- Klement, Ingo,Luetjens, Henning,Knochel, Paul
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p. 3161 - 3164
(2007/10/02)
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