- HALONIUM ION-INDUCED BIOSYNTHESIS OF CHLORINATED MARINE METABOLITES
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Bromoperoxidases do not directly oxidize the chloride ion; nevertheless, in the presence of bromide ions, chloride ions and hydrogen peroxide, bromoperoxidases react with alkenes and alkynes to produce bromochloro-derivatives.This same reaction is catalysed when seawater is the source of chloride and bromide ions.This suggests that bromonium ion-induced biosynthesis of chlorinated metabolites occurs in marine environments.The role of iodonium ions in the biosynthesis of chlorinated metabolites is also discussed.Key Word Index - Coralina sp.; Rhodophyta; biological halogenation; bromoperoxidase; enzymatic bromochlorination; marine chlorination; role of bromonium ions and iodonium ions; seawater.
- Geigert, John,Neidleman, Saul L.,Witt, Susanne K. de,Dalietos, Demetrios J.
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- Bromotrimethylsilane as a selective reagent for the synthesis of bromohydrins
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Bromotrimethylsilane (TMSBr) is a very efficient reagent in the solvent-free conversion of glycerol into bromohydrins, useful intermediates in the production of fine chemicals. As glycerol is a relevant by-product in biodiesel production, TMSBr has been also tested as a mediator in transesterification in acidic conditions, providing FAME from castor oil in good yields, along with bromohydrins from glycerol. Subsequently the glycerol conversion was optimized and depending on the reaction conditions, glycerol can be selectively converted into α-monobromohydrin (1-MBH) or α,γ-dibromohydrin (1,3-DBH) in very good yields. This journal is
- Giomi, Donatella,Salvini, Antonella,Ceccarelli, Jacopo,Brandi, Alberto
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p. 14453 - 14458
(2021/05/19)
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- Protective opening of epoxide using pivaloyl halides under catalyst-free conditions
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An efficient and environmentally benign protocol for protective opening of epoxide (POE) with pivaloyl halides in solvent-free conditions and in aqueous media under catalyst-free conditions has been developed. The green reaction conditions, simple work-up procedures, high yields and broad scope of the reaction illustrate the good synthetic utility of this method. The key advantages of the reaction are regioselectivity and reconvertability of products into their prior epoxides in the presence of mild reaction conditions.
- Rao, Chitturi Bhujanga,Rao, Dasireddi Chandra,Venkateswara, Mallem,Venkateswarlu, Yenamandra
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supporting information; experimental part
p. 2704 - 2707
(2011/12/05)
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- USES AND COMPOSITIONS OF NITRATE ESTERS FOR PROVIDING SEDATION
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Use of certain nitrate ester compounds or pharmaceutically acceptable salts thereof in the manufacture of a medicament for treating pain or providing analgesia.
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- Highly selective epoxidation of olefinic compounds over TS-1 and TS-2 redox molecular sieves using anhydrous urea-hydrogen peroxide as oxidizing agent
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Highly selective epoxidation of different olefinic compounds was carried out using urea-hydrogen peroxide adduct (UHP) as the oxidizing agent in the presence of TS-1 and TS-2 as redox catalysts. A considerable increase in the epoxide selectivity was observed for different unsaturated compounds, such as allylic (allyl alcohol, allyl chloride, allyl bromide, and methylallyl chloride), open-chain, and cyclic (1-hexene and cyclohexene) and aromatic (styrene and allylbenzene) olefinic compounds, when UHP and U + HP (urea and aqueous H2O2 added separately for the in situ formation of UHP) were used as oxidants instead of aqueous H2O2. The controlled release of anhydrous H2O2 from UHP is the main reason for enhanced epoxide selectivity. Direct spectroscopic evidences for the formation of different Ti-superoxo complexes by the solid-solid interaction between TS-1/TS-2 and urea-hydrogen peroxide adduct were obtained from the characteristic continuous absorption band in the UV-vis region (300-500 nm) and the anisotropic EPR spectra for the superoxide radical attached to Ti(IV) centers on TS-1 and TS-2.
- Laha,Kumar
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p. 339 - 344
(2007/10/03)
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- Studies into reactions of N-methylmorpholine-N-oxide (NMMO) and its hydrates with cyanuric chloride
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The course of the reaction between N-methylmorpholine-N-oxide (NMMO, 1a) and cyanuric chloride (2) is strictly dependent on the hydrate water content of the amine oxide. In solid phase, both substances undergo an explosion-like, extremely exothermic reaction. In solution, this process becomes controllable and leads to a quantitative degradation of NMMO into morpholine and formaldehyde, with 2 only acting as an inducing agent. The reaction can be conducted in a way that a clean deoxygenative demethylation is achieved. The monohydrate of NMMO (1b) is quantitatively converted into N-methylmorpholine and hypochlorous acid by the action of 2. This conversion can be used in synthesis either to deoxygenate tertiary amine N-oxide monohydrates, or to produce chlorohydrins in non-aqueous, organic media in superior yields. The semisesquihydrate of NMMO (1c) reacts with 2 under consumption of water until non-hydrated NMMO is present, which is then further converted into morpholine and HCHO, as in the case of 1a being directly employed as the starting material.
- Rosenau, Thomas,Potthast, Antje,Kosma, Paul
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p. 9809 - 9815
(2007/10/03)
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- Synthesis of Dibromohydrins from Glycerol by Using an Ion Exchange Resin as Catalyst
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Bromination of glycerol by 48percent hydrobromic acid in the presence of an acid ion exchange resin (C264 or A19) led to the formation of a mixture of 1,3- and 2,3-dibromohydrins in a yield of around 70percent.The side products were essentially brominated polyglycerols.
- Bouillaud, Alain,Dargelos, Marianne,Borredon, Marie-Elisabeth
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p. 2123 - 2128
(2007/10/02)
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- β-Alkoxyacrylates in radical cyclizations: Remarkably efficient oxacyle synthesis
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β-Alkoxyacrylates were found to be exceptionally efficient radical acceptors in radical-mediated intramolecular cyclizations. For example, reaction of 5-bromo-2-pentanol with ethyl propiolate, tributylstannane-mediated radical cyclization, and hydrolysis yielded (±) (cis-6-methyltetrahydropyran-2-yl)acetic acid, a known component of civet.
- Lee, Eun,Tae, Jin Sung,Lee, Chulbom,Park, Cheol Min
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p. 4831 - 4834
(2007/10/02)
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- Degradation of 2,3-Dichloro-1-propanol by a Pseudomonas sp.
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A bacterium that assimilates 2,3-dichloro-1-propanol was isolated from soil by enrichment culture.The strain was identified as Pseudomonas sp. by the taxonomic studies.The strain converted 2,3-dichloro-1-propanol to 3-chloro 1,2-propanediol, releasing chloride ions.The conversion was stereospecific because the residual 2,3-dichloro-1-propanol and formed 3-chloro-1,2-propanediol gave optical rotation.The resting cells converted various halohydrins to the dehalogenated alcohols, and cell-free extracts had strong epoxyhydrolase activity.These results indicated that the strain assimilated 2,3-dichloro-1-propanol via 3-chloro-1,2-propanediol, glycidol and glycerol.The possibility to manufacture optically active 2,3-dichloro-1-propanol is discussed.
- Kasai, Naoya,Tsujimura, Kazuya,Unoura, Kinya,Suzuki, Toshio
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p. 3185 - 3190
(2007/10/02)
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- Osmium(VIII)-catalysed Reactions of Allyl and Crotyl Alcohols with Chloramine-T, Chloramine-B, Bromamine-T and Bromamine-B: Kinetics and Mechanism of Formation of Halohydrins in Alkaline Medium
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Kinetivs of reaction of allyl and crotyl alkohols with chloramine-T, chloramine-B, bromamine-T and bromamine-B-in alkaline medium in the presence of OsO4 catalyst at 40 deg C have been studied.The rate shows first order dependence in , and inverse fractional order in .The added sulphonamide and varying the ionic strength of the medium have no effect on the rate.However, the rate decreases with increase in methanol content of the reaction medium.All these observations show that neutral species are involved in rate-determing step.A mechanism in which the hypohalous acids are formed in the rate-determing step, which react with the alcohols in a fast step has been proposed.The decrease in rate in D2O (solvent isotope effect) support the proposed mechanism.
- Naidu, H. M. K.,Yamuna, B.,Mahadevappa, D. S.
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p. 114 - 117
(2007/10/02)
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