- Iodoetherification of unactivated alkenes catalyzed by diphosphine palladium(II) complexes
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A palladium-catalyzed intramolecular iodoetherification of alkenes is reported. The reaction is efficient and highly diastereoselective for disubstituted alkenes. The tether length between the alcohol and alkene can be varied to produce tetrahydrofuran and tetrahydropyran rings. Diphosphine palladium(II) salts are highly active catalysts enabling future studies on the development of an enantioselective process.
- Doroski, Todd A.,Cox, Matthew R.,Morgan, Jeremy B.
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- Reaction of homoallylic alcohols with NaIO4/NaHSO3 reagent - Synthesis of alkyl substituted tetrahydrofuran derivatives
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Treatment of homoallylic alcohols with NaIO4/NaHSO3 reagent in aqueous t-BuOH under mild conditions produced tetrahydrofuran derivatives together with iodohydrins in a stereospecific manner. The reaction pathways of the formation of tetrahydrofurans from trans- and cis-homoallylic alcohols were found to be different. The present method provides a new approach to various alkylated tetrahydrofuran derivatives. (C) 2000 Elsevier Science Ltd.
- Okimoto, Yoshio,Kikuchi, Daisuke,Sakaguchi, Satoshi,Ishii, Yasutaka
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- A New Easy Method for the Synthesis of Cyclic Halogenoethers and Halogenolactones
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Oxidation of halogen salts with m-chloroperbenzoic acid in the presence of 18-crown-6 and of suitable hydroxy or carboxy alkenes leads readily to high yield production of cyclic halogenoethers or halogenolactones.
- Srebnik, Morris,Mechoulam, Raphael
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- Direct halogenation of organic compounds with halides using oxone in water - A green protocol
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Direct bromination and iodination of various aromatic compounds with NaBr and NaI using oxone (2KHSO5·KHSO4·K 2S04) in water was accomplished successfully in high-to-excellent yields. The main benefit of this protocol is the performance of the reactions in water in the presence of a harmless oxidant without the use of any organic cosolvents. Using NaBr and NaI as the safe sources of halogens is another advantage of the protocol. This method is easily applicable to the large-scale operations. We have also applied this method successfully for the iodocyclization of an unsaturated alcohol and an unsaturated carboxylic acid.
- Firouzabadi,Iranpoor,Kazemi
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experimental part
p. 1675 - 1681
(2010/01/29)
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- Highly efficient halogenation of organic compounds with halides catalyzed by cerium(III) chloride heptahydrate using hydrogen peroxide as the terminal oxidant in water
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In this article a new environmentally friendly catalytic method is described for the efficient monoiodination and bromination of arenes and also iodoetherification and iodolactonization of olefins using hydrogen peroxide as the terminal oxidant. The method is based on using sodium iodide or sodium bromide, hydrogen peroxide (35%) and cerium(III) chloride as an effective catalyst in water at room temperature or under reflux conditions. By this protocol, iodination of anilines proceeded with high regioselectivity at the para position with the formation of small amounts of the ortho isomers. However, bromination of anilines proceeded with absolute regioselectivity to give the para isomers as the sole products in high yields. Iodinations and bromi-nations of m-xylene, toluene, chloro- and bromobenzenes were proceeded with excellent regioselectivity to produce the para isomers as the sole products. Benzene was also halogenated by this catalytic system to give the monohalogenated benzene in good yields. Iodoetherification and iodolactonization of olefins also proceeded easily in high yields at room temperature. However, the bromination of olefins by this protocol failed and the starting materials were detected intact.
- Firouzabadi, Habib,Iranpoor, Nasser,Kazemi, Somayeh,Ghaderi, Arash,Garzan, Atefeh
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experimental part
p. 1925 - 1932
(2011/03/18)
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- A convenient method for in situ generation of I2 using CuSO 4/NaI and its applications to the deprotection of acetals, etherifications and iodolactonizations
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A convenient method for the in situ generation of I2 using CuSO4/NaI has been developed. The applications of this method to the deprotection of acetals, etherifications and iodolactonizations have been demonstrated. The use of toxic and corrosive molecular iodine is avoided. Georg Thieme Verlag Stuttgart.
- Bailey, Aaron D.,Cherney, Steven M.,Anzalone, Peter W.,Anderson, Erin D.,Ernat, Justin J.,Mohan, Ram S.
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p. 215 - 218
(2007/10/03)
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- Oxone-KI Induced Lactonization and Etherification of Unsaturated Acids and Alcohols: A Formal Synthesis of Mintlactone
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Unsaturated acids and alcohols interact with Oxone and KI in acetonitrile-H2O and undergo iodolactonization and iodoetherification in short times with good yields. The reaction has been used for the formal synthesis of mintlactone starting from isopulegol.
- Curini, Massimo,Epifano, Francesco,Marcotullio, M. Carla,Montanari, Francesca
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p. 368 - 370
(2007/10/03)
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- Bradykin B1receptor antagonists
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Bradykinin B1-receptor antagonists of formula are disclosed. The compounds are useful for treating diseases associated with inappropriate bradykinin receptor activity, such as diabetic vasculopathy, inflammation, pain, hyperalgesia, asthma, rhinitis, septic shock, atherosclerosis and multiple sclerosis. Pyrimidines, triazines, and anilines in which Q is imidazolyl or pyrrolyl are particularly preferred.
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- N-iodosaccharin - A new reagent for iodination of alkenes and activated aromatics
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A mild and efficient iodination reagent, N-iodosaccharin was prepared. Iodination of activated aromatics and alkenes with the reagent takes place fast and under very mild conditions, without the aid of strong acids or heavy metals. The reagent does not affect oxidizable groups, such as hydroxyl or aldehyde.
- Dolenc, Darko
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p. 544 - 546
(2007/10/03)
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- X+ transfer from the halonium ions of adamantylideneadamantane to acceptor olefins. The possibility of chiral induction in the transfer process
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The bromonium ion of adamantylideneadamantane (Ad=Ad-Br+) has been used to induce the bromocyclization of a 4-pentenyl glycoside (10) and a 5-hexenyl glycoside (11) in dichloroethane. The kinetics of these processes have been studied at 25°C in the presence of varying [Ad=Ad] and, in the case of the transfer to 10, in the presence of pentanol. The second-order rate constants for bromocyclization of these two alkenes are (1.04 ± 0.06) × 10-1 M-1 s-1 and (5.34 ± 0.2) × 10-2 M-1 s-1, respectively, and in no case does added Ad=Ad or pentanol alter the reaction rate. The kinetic behavior is interpreted in terms of cyclization occurring directly from a 1:1 complex of Ad=Ad-Br+ and 10 or 11. The chiral induction for the bromocyclization of 10 promoted by AdAd-Br+ was measured at 20% e.e., the (-)-(S)-tetrahydrofurfuryl bromide being the dominant stereoisomer. Ad=Ad molecules substituted at one of the homoallylic carbons by an axial methyl group (12), or by two methyl groups (axial and equatorial), were synthesized and the 1H NMR spectra of their bromonium ions is given. These materials are not stable for prolonged times at room temperature. A limited kinetic study of the reaction of 12-Br+ and 4-pentenol indicated that the Br+ transfer is 500 times faster than the comparable transfer from Ad=Ad-Br+ to 4-pentenol. The possibility of using these materials to induce chiral bromocyclization is discussed.
- Neverov, Alexei A.,Muise, Theresa L.,Brown
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p. 1844 - 1850
(2007/10/03)
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- Br+ and I+ transfer from the halonium ions of adamantylideneadamantane to acceptor olefins. Halocyclization of 1,ω-alkenols and alkenoic acids proceeds via reversibly formed intermediates
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The kinetics of the transfer of X+ from the bromonium and iodonium ions of adamantylideneadamantane (1-Br+ and 1-I+) to some 1,ω-alkenols and alkenoic acids in ClCH2CH2Cl at 25°C was investigated. In all cases, the expected products of halocyclization were observed. For the iodonium ion transfer the reaction kinetics are second order overall, first order in both 1-I+ and acceptor olefin. Transfer of the bromonium ion from 1-Br+ to these acceptor olefins exhibits different kinetic characteristics. In most cases, the rate of the Br+ transfer is subject to strong retardation in the presence of added parent olefin (Ad=Ad), suggestive of a common species rate depression. In some cases, such as 4-penten-1-ol (2b) and 4-pentenoic acid (4b), the reaction can be completely suppressed at high [Ad=Ad]. In other cases, such as 3-buten-1-ol (2a), 5-hexen-1-ol (2c), cyclohexene, 4-(hydroxymethyl)cyclohexene (3), and 5-endo-carboxynorbornene (5), added Ad=Ad does not suppress the reaction completely. In the cases of the 1,ω-alkenols, the reactions appear to exhibit kinetic terms that are greater than first order in alkenol. In these cases, alcohols such as 1-pentanol also accelerate the reaction, pointing to the involvement of the hydroxyl group of the second alkenol as a catalytic species. A unifying mechanism consistent with the data that involves two reversibly formed intermediates is presented.
- Neverov,Brown
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p. 962 - 968
(2007/10/03)
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- ALKOXY RADICALS IN ORGANIC SYNTHESIS. A NOVEL APPROACH TO SPIROKETALS
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Photolysis of an unsaturated alcohol in the presence of HgO and iodine generates an alkoxy radical which can cyclize to form a five-membered ring ether.If a hemiketal is employed, a spiroketal can be formed in good yield.
- Kraus, George A.,Thurston, Jeff
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p. 4011 - 4014
(2007/10/02)
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