- Reducing characteristics of borohydride exchange resin-CuSO4 in methanol
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Reducing characteristics of borohydride exchange resin (BER)-CuSO 4 (cat.) were studied in methanol at room temperature. Carbon-carbon double bonds conjugated with benzene or carbonyl group were more rapidly reduced than was the case with isolated double bonds. Carbonyl groups were readily reduced, whereas esters and amides were inert, and nitriles were slowly reduced. High chemoselectivity was also observed in halide reductions: p-bromochlorobenzene and p-bromoiodobenzene were reduced quantitatively to chlorobenzene and bromobenzene, respectively. Aliphatic epoxides were inert to this reagent; however, styrene oxide derivatives were readily reduced to the corresponding deoxygenated products. Aliphatic azides were reduced slowly during 6 h, whereas phenyl azide was transformed to aniline in 1 h. Nitrocyclohexane was reduced at room temperature, but nitrobenzene, nitrosobenzene, azobenzene, and azoxybenzene required an elevated temperature (65 °C) for rapid reductions (1 h). Similarly, N,N-dimethylanihne N-oxide was reduced at room temperature, whereas pyridine N-oxide required refluxing. Finally, among the sulfur compounds tested, only diphenyl disulfide was reduced readily, and sulfide, aliphatic disulfide, sulfoxide, sulfone, and tosylate were inert to this reducing system.
- Sim, Tae Bo,Yoon, Nung Min
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p. 1101 - 1107
(2007/10/03)
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- Bimolecular formation of radicals by hydrogen transfer, 11: Transfer hydrogenation of conjugated cyclic dienes and trienes
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1,3-Cyclohexadiene, 1,3-cycloheptadiene and cycloheptatriene are smoothly hydrogenated to cyclohexene and cycloheptene, respectively, when heated to 260-340°C with an excess of 9,10-dihydroanthracene (DHA) in diphenyl ether or benzonitrile. On the basis of a mechanistic study a nonchain three-step mechanism is proposed which is initiated by a transfer of a hydrogen atom from DHA to the polyenes (retrodisproportionation). VCH Verlagsgesellschaft mbH, 1996.
- Morgenthaler, Jens,Ruechardt, Christoph
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p. 1529 - 1532
(2007/10/03)
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- Regioselective Hydrogenation of Conjugated Dienes Catalyzed by Hydridopentacyanocobaltate Anion using β-Cyclodextrin as the Phase-Transfer Agent and Lanthanide Halides as Promotors
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β-Cyclodextrin is a useful phase-transfer agent for the hydrogenation of conjugated dienes to monoolefins catalyzed by the in situ generated hydridopentacyanocobaltate anion.This reaction, which usually proceeds by 1,2-addition to the diene, is promoted by cerium or lanthanum chloride.Polyethyleneglycol (PEG-400), with or without added lanthanide, can also used as the phase-transfer agent for the reduction process.
- Lee, Jong-Tae,Alper, Howard
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p. 1854 - 1856
(2007/10/02)
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- Stereochemistry of the Bicyclopentane Ringopening; Thermolysis of Tricyclo2,4>heptane Derivatives
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Thermolysis of the anti-tricyclic compounds 6, 22 and 34 proceeds preferentially by concerted 2s+?2a>-reactions and leads to cis,trans-olefines 8, 24 and 37.The rearrangement of the syn-isomers on the other hand seems to be a nonconcerted reaction yielding the diradicals 15, 27 and 36.
- Roth, Wolfgang R.,Klaerner, Frank-Gerit,Grimme, Wolfram,Koeser, Hans G.,Busch, Ralf,et al.
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p. 2717 - 2737
(2007/10/02)
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- Organic Photochemistry in the Far-ultraviolet: Unusual Wavelength Dependence in Solution-phase Irradiations
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In the region from 185 to 215 nm certain compounds show extreme selectivity in their photodecomposition modes in solution depending on the wavelength even though such compounds possess only one intense absorption in this region.
- Srinivasan, Ra,Baum, Thomas,Brown, Karen,Ors, Jose,White, Lloyd S.,et al.
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p. 973 - 974
(2007/10/02)
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