- Thiourea-Mediated Halogenation of Alcohols
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The halogenation of alcohols under mild conditions expedited by the presence of substoichiometric amounts of thiourea additives is presented. The amount of thiourea added dictates the pathway of the reaction, which may diverge from the desired halogenation reaction toward oxidation of the alcohol, in the absence of thiourea, or toward starting material recovery when excess thiourea is used. Both bromination and chlorination were highly efficient for primary, secondary, tertiary, and benzyl alcohols and tolerate a broad range of functional groups. Detailed electron paramagnetic resonance (EPR) studies, isotopic labeling, and other control experiments suggest a radical-based mechanism. The fact that the reaction is carried out at ambient conditions, uses ubiquitous and inexpensive reagents, boasts a wide scope, and can be made highly atom economic, makes this new methodology a very appealing option for this archetypical organic reaction.
- Mohite, Amar R.,Phatake, Ravindra S.,Dubey, Pooja,Agbaria, Mohamed,Shames, Alexander I.,Lemcoff, N. Gabriel,Reany, Ofer
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supporting information
p. 12901 - 12911
(2020/11/26)
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- An efficient conversion of alcohols to alkyl bromides using pyridinium based ionic liquids: A green alternative to appel reaction
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Pyridinium based ionic liquids namely 4-alkylpyridinium bromides were prepared and used for the conversion of alcohols to alkyl bromides in the presence of p-toluenesulphonic acid in the absence of volatile organic compounds. This solvent free procedure promises to be a much improved and environmentally benign alternative to the Appel reaction.
- Das, Pranab J.,Das, Jupitara,Das, Dimpee
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p. 651 - 654
(2018/02/09)
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- Scalable anti-Markovnikov hydrobromination of aliphatic and aromatic olefins
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To improve access to a key synthetic intermediate we targeted a direct hydrobromination-Negishi route. Unsurprisingly, the anti-Markovnikov addition of HBr to estragole in the presence of AIBN proved successful. However, even in the absence of an added initiator, anti-Markovnikov addition was observed. Re-examination of early reports revealed that selective Markovnikov addition, often simply termed "normal" addition, is not always observed with HBr unless air is excluded, leading to the rediscovery of a reproducible and scalable initiator-free protocol.
- Galli, Marzia,Fletcher, Catherine J.,Del Pozo, Marc,Goldup, Stephen M.
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supporting information
p. 5622 - 5626
(2016/07/06)
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- Aromatic cation activation: Nucleophilic substitution of alcohols and carboxylic acids
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A new method for the nucleophilic substitution of alcohols and carboxylic acids using aromatic tropylium cation activation has been developed. This article reports the use of chloro tropylium chloride for the rapid generation of alkyl halides and acyl chlorides under very mild reaction conditions. It demonstrates, for the first time, the synthetic potential of tropylium cations in promoting chemical transformations.
- Nguyen, Thanh V.,Bekensir, Alp
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supporting information
p. 1720 - 1723
(2014/04/17)
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- H3PW12O40-[bmim][FeCl4]: A novel and green catalyst-medium system for microwave-promoted selective interconversion of alkoxymethyl ethers into their corresponding nitriles, bromides and iodides
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In the present work, the catalytic activity of 12-tungstophosphoric acid immobilized on [bmim][FeCl4] ionic liquid as a highly efficient and eco-friendly catalytic system for rapid and chemoselective direct conversion of MOM- or EOM-ethers into their corresponding nitriles, bromides and iodides under microwave irradiation is reported. In these reactions, the products are obtained in high yields. The catalyst exhibited remarkable reactivity and was reused several times.
- Mohammadpoor-Baltork, Iraj,Moghadam, Majid,Tangestaninejad, Shahram,Mirkhani, Valiolah,Mirjafari, Arsalan
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experimental part
p. 1468 - 1473
(2011/10/09)
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- Microwave-promoted, one-pot conversion of alkoxymethylated protected alcohols into their corresponding nitriles, bromides, and iodides using [bmim][InCl4] as a green catalyst
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The Lewis acid room temperature ionic liquid, [bmim][InCl4], was found to be an efficient and green catalyst for the highly chemoselective and one-pot conversion of MOM- or EOM-ethers into their corresponding nitriles, bromides, and iodides under microwave irradiation. The procedures are simple, rapid, and high yielding. The catalyst exhibited a remarkable reactivity and is reusable.
- Mirjafari, Arsalan,Mohammadpoor-Baltork, Iraj,Moghadam, Majid,Tangestaninejad, Shahram,Mirkhani, Valiollah,Khosropour, Ahmad Reza
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supporting information; experimental part
p. 3274 - 3276
(2010/07/18)
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- Direct bromination and iodination of non-activated alkanes by hypohalite reagents
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The direct functionalisation of alkanes through bromination and iodination has been successfully achieved. The combination of stoichiometric mixtures of elemental halogen and sodium alkoxides leads to the formation of alkyl hypobromites and hypoiodites as reagents. The halogenation occurs without external photostimulation under thermal reaction conditions. Georg Thieme Verlag Stuttgart.
- Montoro, Raul,Wirth, Thomas
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p. 1473 - 1478
(2007/10/03)
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- Silicaphosphine (Silphos): A filterable reagent for the conversion of alcohols and thiols to alkyl bromides and iodides
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Silicaphosphine (Silphos), [P(Cl)3-n(SiO2) n], as a new heterogeneous reagent is introduced. This reagent converts alcohols and thiols to their corresponding bromides and iodides in the presence of X2 (X=Br, I) in refluxing CH3CN in high to quantitative yields. Use of Silphos provides a highly practical method for the easy separation of the Silphos oxide byproduct by a simple filtration.
- Iranpoor, Nasser,Firouzabadi, Habib,Jamalian, Arezu,Kazemi, Foad
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p. 5699 - 5704
(2007/10/03)
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- Ionic liquids as reagents and solvents in conjunction with microwave heating: Rapid synthesis of alkyl halides from alcohols and nitriles from aryl halides
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We show that using ionic liquids as reagents in conjunction with microwave heating it is possible to prepare primary alkyl halides from the corresponding alcohols rapidly. Using ionic liquids as solvents in conjunction with microwave heating it is possible to prepare aryl nitriles from the corresponding aryl bromides or iodides. The scope and limitations of using microwave-promotion as a tool in these reactions is discussed.
- Leadbeater, Nicholas E.,Torenius, Hanna M.,Tye, Heather
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p. 2253 - 2258
(2007/10/03)
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- Study of activation energy and order of reaction of some liquid crystals
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Liquid crystals of the type p-phenylene-di-p-n-alkoxy benzoate have been prepared. Kissinger isothermal decomposition method has been used for determination of activation energy values of liquid crystals. Kissinger's assessment for shape index of DTA peaks is used to find the order of reaction. There is no direct relationship between the carbon atoms in terminal methylene groups and Ea values. Order of reaction value decreases with increase in heating rate upto carbon atoms 10 in the terminal methylene group but beyond this the order increases or decreases.
- Mundhe
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p. 246 - 249
(2007/10/03)
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- Calamitic organometallic liquid crystals with terminal metal. Syntheses and liquid crystal properties of dicarbonylrhodium(I) β-diketonate complexes
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A series of novel organometallic complexes based on γ-substituted β-diketone ligands with terminal metal Rh(I) have been prepared by reaction of the ligands with [Rh(CO)2(μ-Cl)]2. The mesomorphism of the ligands and complexes has been investigated using DSC and polarizing microscope. It is found that non-mesogenic ligands with n=7, 8, 9, 10, 11 can form liquid crystalline phase by direct coordination to metal. The effect of the terminal carbon number on the mesomorphism has also been discussed.
- Wan, Wen,Guang, Wen-Jie,Zhao, Ke-Qin,Zheng, Wei-Zhong,Zhang, Liang-Fu
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p. 157 - 161
(2007/10/03)
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- Esterification of carboxylic acid salts
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Mono- or polycarboxylic acid esters are prepared by reacting a salt of such carboxylic acid with an organic halocompound, e.g., a (cyclo)alkyl, (cyclo)alkenyl, aryl or aralkyl halide, in an aqueous reaction medium, in the presence of a catalytically effective amount of a phase transfer catalyst, for example an onium salt.
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- Halogen-exchange reactions between alkyl fluorides and boron trihalides or tetrahalides. A convenient synthesis of alkyl halides from alkyl fluorides
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A simple and effective method for converting fluoroalkanes to their corresponding chloro-, bromo- and iodo-alkanes using commercially available boron trihalides and titanium tetrahalides is described. - Keywords: Halogen-exchange reactions; Alkyl fluorides; Boron trihalides; Titanium tetrahalides; NMR spectroscopy; Mass spectrometry
- Namavari, Mohammad,Satyamurthy, N.,Barrio, Jorge R.
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- Halogen exchange reactions between alkyl halides and aqueous hydrogen halides. A new method for preparation of alkyl halides
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Alkyl fluorides and chlorides are efficiently converted to their corresponding alkyl bromides and iodides by using readily available aqueous HBr and HI. The application of the same method for the conversion of some alkyl fluorides to the corresponding alkyl chlorides with cone. HCl is also described.
- Namavari, Mohammad,Satyamurthy,Phelps, Michael E.,Barrio, Jorge R.
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p. 4973 - 4976
(2007/10/02)
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- Electron Spin Resonance Spectra and Structure of the Radical Cations of Dibromoalkanes and Monobromoalkanes
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The radical cations of dibromoalkanes containing two bromines separated by an alkyl chain, have been generated by exposing dilute solutions of the dibromoalkanes in freon to X-rays at 77 K.Two types of e.s.r. spectra were observed for these cations.The spectra obtained for Br(CH2)nBr, n = 1-7, show septet features characteristic of two equivalent Br nuclei.The coupling constant of the septet increases and reaches a plateau, with increased n in these dibromoalkanes.This indicates that a positive hole in these cations is shared, not by the two Br nuclei connected through ?-delocalization over the chain, but by the two Br nuclei directly bonded to each other, in accordance with conclusions recently drawn from e.s.r. studies of dichloroalkane cations.In contrast, the e.s.r. spectra obtained for Br(CH2)nBr, n > 7, are more complicated.When similar experiments were carried out with H(CH2)nBr, n > 7, analogous spectra were obtained, indicating that the spectra observed for these dibromoalkanes can be interpreted in terms of hyperfine interactions to only one of the two Br nuclei and to two nuclei with nuclear spins of 1/2.This result, considered together with the fact that similar cationic centres were detected for H(CH2)nBr, n > 3, and with the spectral change observed for Br(CH2)nBr and H(CH2)nBr cations in different matrices (CCl2FCClF2, CCl3F, and CCl4) indicates that cyclization also occurs for these cations, the positive hole being occupied in a three-centre bond comprising a Br nucleus, a C nucleus (four atoms away from the Br nucleus), and an H nucleus bonded to the C nucleus.
- Hasegawa, Akinori,Symons, Martyn C. R.,Shiotani, Masaru
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p. 657 - 666
(2007/10/02)
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- OXIDATION OF N-ALKYL-N'-TOSYLHYDRAZINES WITH BROMINE
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Oxidation of N-alkyl-N'-tosylhydrazines with bromine yield alkyl bromides, vicinal alkyl dibromides and traces of alcohols.The main products of primary hydrazines are monobromides whereas secondary hydrazines preferably produce dibromides.The reaction proceeds with evolution of nitrogen and hydrobromic acid and by the formation of intermediate sulfinic ester wich may be isolated.Various substrates were examined under different conditions to confirm the validity of the reaction mechanism hypothesized.
- Palmieri, Gianni
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p. 4097 - 4102
(2007/10/02)
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- LIQUID CRYSTALLINE PROPERTIES OF 4-N-ALKOXYPHENYL 4-NITROBENZOATES.
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Twelve 4-alkoxyphenyl esters of 4-nitrobenzoic acid were synthesized. The mesophases were identified and the transition temperatures and enthalpies determined. The above series shows considerable similarity to the reverse analogues, i. e. , the 4-nitro-phenyl 4-n-alkoxybenzoates.
- Galewski,Sobczyk
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- MOLECULAR MECHANISM OF HYDROGEN BROMIDE ADDITION TO OLEFINS
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Experimental results on the products and the kinetics of the hydrogen bromide addition to alkenes-1 in non-polar solvents and on complex formation in hydrogen bromide-olefin-solvent systems are reviewed.Theoretical calculations concerning hydrogen bromide-olefin complexes are used along with the experimental evidence to suggest a molecular mechanism of addition involving intermediate cyclic structures.
- Sergeev, G. B.,Stepanov, N. F.,Leenson, I. A.,Smirnov, V. V.,Pupyshev, V. I.,et al.
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p. 2585 - 2590
(2007/10/02)
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