- Bromination of alkenols with the H2O2 - LiBr - CeIII and H2O2 - LiBr - CeIV systems
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Reactions of alkenols with H2O2 - LiBr - Ce(NO 3)3·6H2O or H2O2 - LiBr - Ce(NH4)2(NO3)6 system led to bromination of the double bond to yield vicinal dibromoalkanols. The reaction proceeded highly selectively, no oxidation of the hydroxyl group virtually occurred.
- Nikishin,Sokova,Kapustina
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- Electroreductive Carbofunctionalization of Alkenes with Alkyl Bromides via a Radical-Polar Crossover Mechanism
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Electrochemistry grants direct access to reactive intermediates (radicals and ions) in a controlled fashion toward selective organic transformations. This feature has been demonstrated in a variety of alkene functionalization reactions, most of which proceed via an anodic oxidation pathway. In this report, we further expand the scope of electrochemistry to the reductive functionalization of alkenes. In particular, the strategic choice of reagents and reaction conditions enabled a radical-polar crossover pathway wherein two distinct electrophiles can be added across an alkene in a highly chemo- and regioselective fashion. Specifically, we used this strategy in the intermolecular carboformylation, anti-Markovnikov hydroalkylation, and carbocarboxylation of alkenes - reactions with rare precedents in the literature - by means of the electroreductive generation of alkyl radical and carbanion intermediates. These reactions employ readily available starting materials (alkyl halides, alkenes, etc.) and simple, transition-metal-free conditions and display broad substrate scope and good tolerance of functional groups. A uniform protocol can be used to achieve all three transformations by simply altering the reaction medium. This development provides a new avenue for constructing Csp3-Csp3 bonds.
- Zhang, Wen,Lin, Song
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supporting information
p. 20661 - 20670
(2020/12/23)
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- A 3 - halogenated tetrahydrofuran preparation method
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The invention discloses a 3 - halogenated tetrahydrofuran preparation method. The method comprises the following steps: in the organic solvent, 0 - 85 °C temperature, shown in formula I compound with a reducing agent, can be; wherein R1 And R2 The same, they are selected from chlorine or bromine; the reducing agent is sodium borohydride or potassium borohydride; wherein the organic solvent is b [...], 2 - chloroethyl methyl ether, ethyl ether, tetrahydrofuran or methyl tetrahydrofuran. The method of the invention less reaction steps, the process is simple, the product yield can reach 80% - 95%, and the low cost of raw materials, equipment investment, the price of the product there are advantages; in addition the method pollution is small, friendly to the environment, and is suitable for large-scale industrial production.
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Paragraph 0038; 0039
(2019/05/28)
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- Introduction of bromine and chlorine substituents in medium ring ethers and lactones
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A convenient preparation of α-halo enamines using oxalyl halides is described together with applications of these reagents in the halogenation of β-hydroxy cyclic ethers and lactones.
- Bendall, Justin G.,Payne, Andrew N.,Screen, Thomas E. O.,Holmes, Andrew B.
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p. 1067 - 1068
(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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- STRUCTURE AND FORMATION OF C4H7O(1+) IONS RESULTING FROM ELECTRON IMPACT INDUCED DECOMPOSITION OF CYCLIC PRECURSORS
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Possible structures and modes of formation of C4H7O(1+) ions formed by electron impact induced decomposition of tetrahydrofuran and tetrahydropyran derivates are discussed in view of labelling results and MIKE, CA, and T data.Limitations of these techniques are pointed out.
- Stolze, Rainer,Budzikiewicz, Herbert
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p. 781 - 787
(2007/10/02)
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