- Dehydrative allylation of alcohols and deallylation of allyl ethers catalyzed by [CpRu(CH3CN)3]PF6 and 2-pyridinecarboxylie aeid derivatives. Effect of π-accepting ability and COOH acidity of ligand on reactivity
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2-Quinolinecarboxylic acid efficiently promotes both the dehydrative allylation of alcohols and the deallylation of allyl ethers and esters in the presence of [CpRu(CH3CN)3JPF6. Comparison of the relative reactivity of various 4-substituted 2-pyridinecarboxylic acids has revealed two linear relations with different ρ values in the Hammett plots. These phenomena can be rationalized by the balance between the π-accepting ability of the pyridine moiety and the acidity of the carboxylic acid of the 2-pyridinecarboxylic acid derivative. Copyright
- Tanaka, Shinji,Saburi, Hajime,Hirakawa, Takuya,Seki, Tomoaki,Kitamura, Masato
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- Nano-dispersed platinum(0) in organically modified silicate matrices as sustainable catalysts for a regioselective hydrosilylation of alkenes and alkynes
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Nano-dispersed platinum(0) particles stabilized in a range of organically modified silicate (ORMOSIL) matrices are investigated as sustainable catalysts for the hydrosilylation of alkenes and alkynes. In this study, five different siloxane matrices including triethoxysilane (HTEOS), methyltriethoxysilane (MTES), ethyltriethoxysilane (ETES), triethoxyvinylsilane (TEVS) and propyltriethoxysilane (PTES) are investigated, and the distribution of the metal particles in these materials analyzed by transition electron microscopy (TEM). The particles appeared to be generally of a small size, with a diameter of ca. 2-5 nm in each of these catalysts, however the distribution is not equally uniform from one matrix to the other. HTEOS, MTES and ETES that respectively carry a hydrogen, a methyl and an ethyl group on the triethoxysilane moiety, displayed a more uniform distribution, while particles appeared to be more scattered in the remaining matrices. Catalysts with a uniform particles distribution produced higher and consistent yields, while those with poor particles distribution produced lower and almost random yields, suggesting that the uniformity in particle distribution, and by extension the nature of the siloxane matrix, are important for the catalytic properties of these materials. The scope of the reaction was broadened to a range of olefins, with a goal of investigating the tolerability of the reaction toward a number of reactive functional groups, resulting in the preparation of 28 compounds. This catalytic system also enabled the hydrosilylation of a limited number of alkynes under the optimized reaction conditions.
- Duke, Brett J.,Akeroyd, Evan N.,Bhatt, Shreeja V.,Onyeagusi, Chibueze I.,Bhatt, Shreya V.,Adolph, Brandy R.,Fotie, Jean
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p. 11782 - 11795
(2018/07/25)
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- Hypervalent Iodine(III)-Mediated Oxidative Fluorination of Alkylsilanes by Fluoride Ions
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The first example of a hypervalent iodine(III)-mediated oxidative fluorination of alkylsilanes by fluoride ions without the use of transition metals is demonstrated. This reaction is operationally simple, scalable, and proceeds under mild reaction conditions. Mechanistic studies suggest the involvement of a single-electron transfer resulting from the interaction of an organopentafluorosilicate and aryliodonium difluoride, which were generated in situ from the corresponding alkylsilane and iodosobenzene, respectively, in the presence of fluoride ions.
- Xu, Peng,Wang, Feng,Fan, Guilan,Xu, Xiufang,Tang, Pingping
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supporting information
p. 1101 - 1104
(2017/01/18)
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- Step-economy etherification of acylated alcohols
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An efficient and convenient protocol has been developed for ether bond formation in mild conditions. A mixture of primary/secondary ester and allylic/benzylic halide in tetrahydrofuran was treated with KOtBu at room temperature to give ether in high yield. This step economic method enabled direct alkylation of the acyl group masked O-nucleophiles. Application of this method in carbohydrate synthesis was feasible and chemo-selectivity can be achieved.
- Xu, Hua-Dong,Xu, Ke,Zheng, Qing,He, Wei-Jie,Shen, Mei-Hua,Hu, Wen-Hao
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supporting information
p. 6836 - 6838
(2015/01/09)
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- Highly reactive and chemoselective cleavage of allyl esters using an air- and moisture-stable [CpRu(IV)(π-C3H5)(2-quinolinecarboxylato)]PF6 catalyst
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A new catalytic process for allyl ester cleavage has been developed by using a robust cationic CpRu(IV) π-allyl complex of 2-quinolinecarboxylic acid that can be stored for over six months in air without any loss of catalytic activity. The deprotection of various alcohols and acids can be attained simply with high reactivity and chemoselectivity under mild conditions. Furthermore, with continuous removal of the low-boiling point coproduct, a turnover number of 1 000 000 can be achieved.
- Tanaka, Shinji,Saburi, Hajime,Murase, Takanori,Ishibashi, Yoshitaka,Kitamura, Masato
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p. 295 - 298
(2008/02/03)
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- [CpRu(IV)(π-C3H5)(2-quinolinecarboxylato)]PF 6 complex: A robust catalyst for the cleavage and formation of allyl ethers
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A facile and efficient method for the quantitative synthesis of [CpRu(IV)(π-C3H5)(2-quinolinecarboxylato)]PF 6 from [CpRu(CH3CN)3]PF6, 2-quinolinecarboxylic acid, and 2-propen-1-ol has been established. The cationic Ru(IV) complex is air- and moisture-stable, and can be stored in a vial for at least six months. This complex realizes a simple and easy operation for both the deallylation of allyl ethers in methanol and the dehydrative allylation of alcohols. Furthermore, with removal of the volatile allyl methyl ether co-product from the reaction system, the robust catalyst can attain a turnover of 10000 cycles of allyl ether cleavage.
- Tanaka, Shinji,Saburi, Hajime,Kitamura, Masato
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p. 375 - 378
(2007/10/03)
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- Method of removing allyl series protecting group using novel ruthenium complex and method of synthesizing allyl ethers
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A cyclopentadienyl ruthenium (II) complex or (iv) complex having an α-imino acid type ligand or an α-amino acid type ligand.
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Page/Page column 6
(2010/02/14)
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- Catalytic dehydrative allylation of alcohols
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(Chemical Equation Presented) An environmentally benign synthesis of allyl ethers has been developed which can be applied to a highly chemoselective protection of hydroxyl groups. A highly efficient [CpRu]-2-quinolinecarboxylic acid (L) catalytic system was successfully employed for the dehydrative allylation of various alcohols without additional activators and solvent (see scheme; R = alkyl, aryl, multifunctional alkyl, Cp = C5H 5).
- Saburi, Hajime,Tanaka, Shinji,Kitamura, Masato
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p. 1730 - 1732
(2007/10/03)
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- Development of a manufacturing process for sibenadet hydrochloride, the active ingredient of viozan
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A process for commercial manufacture of the dual D2- β2 receptor agonist sibenadet hydrochloride has been developed. The process relies upon introduction of operationally simple chemistry at the final stages where two key intermediates are reacted to assemble the final molecule, isolated by crystallization. A nine-stage sequence for synthesis of the key amine hydrochloride intermediate was developed, and modifications to the original process are described. Major strategic improvements were made in definition of the final route to the "side chain" precursor molecule, the second key intermediate, hinging around a thiyl radical addition and subsequent high-yielding telescoped processes for synthesis of this highly crystalline benzoate ester. Development of these chemistries is discussed, together with some issues surrounding definition of the final validated commercial processes.
- Giles, Melvyn E.,Thomson, Colin,Eyley, Stephen C.,Cole, Andrea J.,Goodwin, Christopher J.,Hurved, Paul A.,Morlin, Andrew J. G.,Tornos, James,Atkinson, Stephanie,Just, Cecelia,Dean, Janet C.,Singleton, John T.,Longton, Andrew J.,Woodland, Ian,Teasdale, Andrew,Gregertsen, Bjoern,Else, Howard,Athwal, Mandip S.,Tatterton, Stephen,Knott, Jason M.,Thompson, Nicola,Smith, Stephen J.
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p. 628 - 642
(2013/09/02)
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- SmI2/water/amine mediates cleavage of allyl ether protected alcohols: application in carbohydrate synthesis and mechanistic considerations.
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[reaction: see text]. SmI2/H2O/amine provides selective cleavage of unsubstituted allyl ethers in good to excellent yields. This method is therefore useful in deprotection of alcohols and carbohydrates.
- Dahlen, Anders,Sundgren, Andreas,Lahmann, Martina,Oscarson, Stefan,Hilmersson, Goeran
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p. 4085 - 4088
(2007/10/03)
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- Hypervalent (tert-butylperoxy)iodanes generate iodine-centered radicals at room temperature in solution: Oxidation and deprotection of benzyl and allyl ethers, and evidence for generation of α-oxy carbon radicals
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1-(tert-Butylperoxy)-1,2-benziodoxol-3(1H)-one (1a) oxidizes benzyl and allyl ethers to the esters at room temperature in benzene or cyclohexane in the presence of alkali metal carbonates. Since this reaction is compatible with other protecting groups such as MOM, THP, and TBDMS ethers, and acetoxy groups, and because esters are readily hydrolyzed under basic conditions, this new method provides a convenient and effective alternative to the usual reductive deprotection. Oxidation with 1a occurs readily with C-H bonds activated by both enthalpic effects (benzylic, allylic, and propargylic C-H bonds) and/or polar effects (α-oxy C-H bonds), generating α-oxy carbon-centered radicals, which can be detected by nitroxyl radical trapping. Measurement of the relative rates of oxidation for a series of ring-substituted benzyl n-butyl ethers 2d and 2p-s indicated that electron-releasing groups such as p-MeO and p-Me groups increase the rate of oxidation, and Hammett correlation of the relative rate factors with the σ+ constants of substituents afforded the reaction constant ρ+ = -0.30. The large value of the isotope effect obtained for the oxidation of benzyl n-butyl ether 2d (k(H)/k(D) = 12-14) indicates that the rate-determining step of the reactions probably involves a high degree of benzylic C-H bond breaking. The effects of molecular dioxygen were examined, and the mechanism involving the intermediacy of the tert-butylperoxy acetal 5 and/or the hydroperoxy acetal 32 is proposed. Particularly noteworthy is the finding that (tert-butylperoxy)iodane 1a can generate the tert-butylperoxy radical and the iodine-centered radical 33a, even at room temperature in solution, via homolytic bond cleavage of the hypervalent iodine(III)-peroxy bond.
- Ochiai, Masahito,Ito, Takao,Takahashi, Hideo,Nakanishi, Akinobu,Toyonari, Mika,Sueda, Takuya,Goto, Satoru,Shiro, Motoo
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p. 7716 - 7730
(2007/10/03)
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- ALIPHATIC AMINO BIS-ARYL SQUALENE SYNTHASE INHIBITORS
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This invention relates to a class of novel aliphatic amino bis-aryl compounds containing at least four carbon atoms and an amino group either substituted thereon or incorporated therein and is further linked or bridged to two mono- and/or bicyclic rings. Compounds of this invention reduce levels of serum cholesterol in the body without significantly reducing mevalonic metabolite synthesis. This invention relates also to pharmacological compositions and method of treatment for lowering serum cholesterol levels using the compounds of this invention.
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