- Triphenylselenonium Salts as Effective Phase-Transfer Catalysts
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Triphenylselenonium salts work as highly efficient phase-transfer catalysts for nucleophilic substitution reaction of octyl bromide and addition reaction of dichlorocarbene to olefins.
- Kondo, Shuji,Shibata, Akihiro,Kunisada, Hideo,Yuki, Yasuo
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Read Online
- Effect of the Leaving Group and Solvent in Nucleophilic Aliphatic Substitutions Promoted by Quarternary Onium Salts
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Rates of nucleophilic substitutions by N3- and SCN- (as hexadecyltributylphosphonium salts) in a series of n-octyl derivatives (C8H17X, X = Cl, Br, I, OTos, OMes) have been measured in different solvents (MeOH, Me2SO, PhCl, cyclohexane).Nucleofugacity scales are as follows: OTos > I > OMes * Br >> Cl in MeOH; I > Br > OTos > OMes > Cl in Me2SO; I > OTos* Br > OMes >> Cl in PhCl; OTos > OMes > I > Br >> Cl in cyclohexane.In the case of the methanesulfonic group, reaction rates progressively increase as the polarity and polarizability of the medium diminish: the highest rates are observed in cyclohexane, with 732- and 33-fold enhancements for MeOH and Me2SO, respectively, with N3-, and 22- and 14-fold enhancements with SCN-.In the case of halo derivatives the highest rates are observed in Me2SO with enhancements up to three orders of magnitude with respect to MeOH.The rate ratios in Me2SO and MeOH, expressed as log kMe2SO/kMeOH are OMes (1.3), OTos (1.7), Cl (2.2), Br (2.4), I (2.9); they show the anionic nature of the activated complexes and reflect an increasing polarizability (hence an increasing solvation by Me2SO) of the activated complexes on transfer from mesilate to iodide according to the reported sequence.In cyclohexane any appreciable solvation of the entering group and of the activated complex can be excluded.Therefore, the observed rates should reflect, better than in any other solvent, not only the intrinsic nucleophilicity of the entering group but also the intrinsic nucleofugacity of the leaving group.Rate variations observed in the nonprotic solvents are discussed on the basis of differences of solvation of the activated complex as a function of its polarizability and of that of the solvent.
- Landini, Dario,Maia, Angelamaria,Montanari, Fernando,Rolla, Franco
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Read Online
- COMPARISON OF UNSTIRRED, SONICATED AND STIRRED MIXTURES ON THE TWO-PHASE DISPLACEMENT OF HALIDE BY THIOCYANATE ION
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The two-phase catalytic reaction of alkyl halides with aqueous thiocyanate ion has been found to proceed readily in stirred, unstirred, and sonicated solutions.
- Reeves, W. Preston,McClusky, John V.
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Read Online
- Straightforward Access to Thiocyanates via Dealkylative Cyanation of Sulfoxides
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Thiocyanates, versatile building blocks in organic synthesis, are shown to be easily accessible via an interrupted Pummerer reaction of sulfoxides. This facile dealkylative functionalization proceeds under mild conditions through electrophilic activation of the sulfoxide partner. The resulting thiocyanate itself can serve as a handle for diversification in a straightforward one-pot procedure.
- Todorovi?, Uro?,Klose, Immo,Maulide, Nuno
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supporting information
p. 2510 - 2513
(2021/04/13)
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- An ionic liquid supported on magnetite nanoparticles as an efficient heterogeneous catalyst for the synthesis of alkyl thiocyanates in water
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The present study describes a convenient method to synthesize alkyl thiocyanates from alkyl halides with the use of a novel nanomagnetic-supported organocatalyst (MNP@PEG-ImCl). The new supported ionic liquid is fully characterized by field-emission scanning electron microscopy (FESEM), Fourier-transform infrared (FT-IR), energy dispersive X-ray analysis (EDAX), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM) as well as thermogravimetric analysis (TGA) techniques. It is noteworthy that we observed easy separation of the catalyst from the reaction mixture by a simple magnetic decantation and its reutilization many times without any appreciable loss of activities.
- Fallah-Mehrjardi, Mehdi,Sayyahi, Soheil
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p. 335 - 345
(2021/02/26)
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- Sulfuryl Fluoride Promoted Thiocyanation of Alcohols: A Practical Method for Preparing Thiocyanates
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A novel SO 2F 2-promoted thiocyanation method for the one-step synthesis of thiocyanates through C-O bond cleavage of readily available alcohols with ammonium thiocyanate as the thiocyanating agent was developed. The method avoids the use of additional catalyst, and a variety of (hetero)arene, alkene and aliphatic alcohols reacted with high efficiency in ethyl acetate under mild conditions to afford the corresponding thiocyanates in excellent to quantitative yields with broad functional-group compatibility.
- Zhang, Guofu,Xuan, Lidi,Zhao, Yiyong,Ding, Chengrong
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supporting information
p. 1413 - 1417
(2020/10/02)
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- 2,4,4,6-Tetrabromo-2,5-cyclohexadienone as an efficient reagent for phosphine-free electrophilic transformation of alcohols and epoxides
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In this study, 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TABCO) was prepared and used successfully as a stable phosphine-free reagent for the conversion of alcohols into alkyl thiocyanates and epoxides into 2-hydroxythiocyanates. The reactions seem to proceed via in situ generation of electrophilic sulfur species by reaction of NH4SCN and TABCO. This combined reagent worked well with both alcohols and epoxides in acetonitrile solvent and under solvent-free conditions.
- Khajeh-Kolaki, Aslan,Mokhtari, Babak
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p. 251 - 258
(2016/06/01)
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- A simple, one-pot and phosphine-free procedure for thiocyanation of alcohols Using N-(p-toluenesulfonyl) imidazole (TsIm)
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An efficient, one-pot, phosphine-free thiocyanation of alcohols has been achieved utilising potassium thiocyanate and N-(p-toluenesulfonyl) imidazole (TsIm) as a coupling agent in the presence of triethylamine in anhydrous DMF at 70 °C. This method converts primary alcohols into the corresponding thiocyanates, without isomerisation to isothiocyanates, in good to excellent yields. A total of 17 thiocyananates were prepared, five of which are novel. Using one equivalent of KSCN, the method shows good selectivity in the thiocyanation of a primary alcohol in the presence of a secondary alcohol.
- Rad, Mohammad Navid Soltani
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p. 583 - 587
(2016/10/18)
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- Iron-Catalyzed Decarboxylation of Trifluoroacetate and Its Application to the Synthesis of Trifluoromethyl Thioethers
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Nucleophilic CF3 has been generated by decarboxylation of potassium trifluoroacetate, arguably the most easy-to-handle, inexpensive, and sustainable source of trifluoromethyl groups. Simple iron(II) chloride catalyzes the decarboxylation as well as a subsequent trifluoromethylation of organothiocyanates, resulting in a straightforward synthesis of trifluoromethyl thioethers. The KCN byproduct is absorbed by iron(II) with formation of nontoxic potassium hexacyanoferrate. An analogous trifluoromethylation of aldehydes with trifluoroacetate underlines the synthetic potential of such iron-catalyzed decarboxylative trifluoromethylations.
- Exner, Benjamin,Bayarmagnai, Bilguun,Jia, Fan,Goossen, Lukas J.
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supporting information
p. 17220 - 17223
(2016/01/25)
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- Chlorodiphenylphosphine as highly selective and efficient reagent for the conversion of alcohols, tetrahydropyranyl and silyl ethers to thiocyanates and isothiocyanates
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(Equation present) A simple, highly selective and efficient method is described for the conversion of primary alcohols, tetrahydropyranyl and silyl ethers to thiocyanates by use of chlorodiphenylphosphine and ammonium thiocyanate. Secondary substrates produce both the two isomeric products, thiocyanate and isothiocyanate, while tertiary ones give isothiocyanates as the only products by this new method. In contrast to previously reported methods based on trivalent phosphorus for this transformation, the present method does not require an electrophile in the presence of trivalent phosphorus (ClPPh 2). The order of activity of these substrates is silyl ether> alcohol > tetrahydropyranyl ether. The present method not only interestingly distinguishes between primary, secondary and tertiary substrates but also converts them to the corresponding thiocyanates with excellent chemoselectivity in the presence of several other functional groups. 2014 Copyright Taylor & Francis Group, LLC.
- Aghapour, Ghasem,Asgharzadeh, Ameneh
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p. 796 - 802
(2014/07/08)
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- Copper-catalyzed cyanation of disulfides by azobisisobutyronitrile leading to thiocyanates
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The copper-catalyzed cyanation of disulfides by azobisisobutyronitrile (AIBN) was developed, leading to thiocyanates in moderate to good yields. This procedure tolerates a series of functional groups, such as chloro, nitro, methyl and methoxycarbonyl in the phenyl ring of disulfides. Notably, it enables the use of two ArS units in (ArS)2. CuI was found to be essential for the in situ formation of cyanide anions. This journal is
- Teng, Fan,Yu, Jin-Tao,Yang, Haitao,Jiang, Yan,Cheng, Jiang
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supporting information
p. 12139 - 12141
(2014/12/11)
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- Phosphine-free conversion of alcohols into alkyl thiocyanates using trichloroisocyanuric acid/NH4SCN
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A convenient and efficient phosphine-free procedure for the one-pot conversion of primary, secondary and tertiary alcohols into the corresponding alkyl thiocyanates or alkyl isothiocyanates is described using trichloroisocyanuric acid/NH4SCN.
- Azadi, Roya,Mokhtari, Babak,Makaremi, Mohamad-Ali
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experimental part
p. 77 - 80
(2012/03/26)
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- β-cyclodextrin immobilized onto dowex resin: A unique microvessel and heterogeneous catalyst in nucleophilic substitution reactions
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The catalytic activity of β-cyclodextrin immobilized on Dowex resin as an efficient solid-liquid phase transfer catalyst was developed for the synthesis of alkyl thiocyanates and phenacyl derivatives in water. The nucleophilic substitution reactions were performed under mild reaction condition and gave the products in excellent yields. Furthermore, the catalyst could be recycled by facile separation without any loss of activity.
- Kiasat, Ali Reza,Zarinderakht, Nasrollah,Sayyahi, Soheil
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experimental part
p. 699 - 702
(2012/05/05)
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- A facile and green protocol for nucleophilic substitution reactions of sulfonate esters by recyclable ionic liquids [bmim][X]
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Ionic liquids [bmim][X] (X = Cl, Br, I, OAc, SCN) are highly efficient reagents for nucleophilic substitution reactions of sulfonate esters derived from primary and secondary alcohols. The counter anions (X-) of the ionic liquids, [bmim][X], effectively replace the sufonates affording the corresponding substitution products such as alkyl halides, acetates, and thiocyanides in excellent yields. The newly developed protocol is very environmentally attractive because the reactions use stoichiometric amounts of ionic liquids as sole reagents in most cases and do not require additional solvents, any other activating reagents, non-conventional equipment, or special precautions. Moreover, these ionic liquids can be readily recycled without loss of reactivity, making the whole process greener.
- Liu, Yajun,Xu, Yongnan,Jung, Sun Ho,Chae, Junghyun
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p. 2692 - 2698,7
(2012/12/12)
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- A facile and green protocol for nucleophilic substitution reactions of sulfonate esters by recyclable ionic liquids [bmim][X]
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Ionic liquids [bmim][X] (X = Cl, Br, I, OAc, SCN) are highly efficient reagents for nucleophilic substitution reactions of sulfonate esters derived from primary and secondary alcohols. The counter anions (X-) of the ionic liquids, [bmim][X], effectively replace the sufonates affording the corresponding substitution products such as alkyl halides, acetates, and thiocyanides in excellent yields. The newly developed protocol is very environmentally attractive because the reactions use stoichiometric amounts of ionic liquids as sole reagents in most cases and do not require additional solvents, any other activating reagents, non-conventional equipment, or special precautions. Moreover, these ionic liquids can be readily recycled without loss of reactivity, making the whole process greener. Georg Thieme Verlag KG Stuttgart · New York.
- Liu, Yajun,Xu, Yongnan,Jung, Sun Ho,Chae, Junghyun
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p. 2692 - 2698
(2013/01/15)
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- Selectfluor F-TEDA-BF4 mediated thiocyanation or isothiocyanation of alcohols by in situ generation of [+SCN] under heterogeneous and neutral conditions
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A convenient approach for thiocyanation of alcohols has been developed using ammonium thiocyanate as thiocyanating agent in the presence of a catalytic amount of Selectfluor F-TEDA-BF4 in aqueous acetonitrile. In this method various alcohols generally afforded the corresponding thiocyanates or isothiocyanates directly in good to high yield under heterogeneous and neutral conditions.
- Khazaei, Ardeshir,Rahmati, Sadegh,Khalafi-Nezhad, Ali,Saednia, Shahnaz
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experimental part
p. 123 - 125
(2012/05/05)
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- A convenient, rapid, and general synthesis of α-oxo thiocyanates using clay supported ammonium thiocyanate
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A very rapid, convenient, and general method for the synthesis of α-oxo thiocyanates has been described by using clay supported ammonium thiocyanate. The procedure avoids the use of additional catalyst, solvent, aqueous work-up and the yields are high. Moreover, the method is applicable for a variety of aryl, heteroaryl, alkyl α-halo carbonyls, β-keto tosylates, α-halo β-dicarbonyl, α-tosyl, β-dicarbonyl, alkyl halide, and alkyl tosylates.
- Meshram,Thakur, Pramod B.,Madhu Babu,Bangade, Vikas M.
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experimental part
p. 1780 - 1785
(2012/05/04)
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- 2-Chloro-1-methylpyridinium iodide, an efficient reagent for the conversion of alcohols into alkyl thiocyanates both under solvent and solvent-free conditions
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A new application of the Mukaiyama reagent for the simple phosphine-free conversion of alcohols into the corresponding alkyl thiocyanates is described. This transformation can be achieved either in acetonitrile or under solvent-free conditions and the products obtained in good to excellent yields. The solvent-free procedure described here is the first report on the solvent-free thiocyanation of alcohols.
- Mokhtari, Babak,Azadi, Roya,Mardani, Edris
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experimental part
p. 491 - 493
(2012/02/01)
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- Ionic liquid brush as a highly efficient and reusable catalyst for on-water nucleophilic substitutions
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A very efficient and reusable catalyst has been developed for the on-water nucleophilic substitution of alkyl halides and tosylates with azide or thiocyanate in excellent to quantitative yields. The reaction proceeds smoothly and cleanly without any organic cosolvent or other adductive, and the brush can be reused at least 10 times without noticeable loss of the catalytic activity. The high efficiency, simplicity of product and catalyst isolation, outstanding recyclability, and organic-solvent-free conditions show promise for the use of this catalyst in the laboratory and in industry. A highly efficient and reusable ionic liquid brush catalyst has been developed for the on-water nucleophilic substitution of alkyl halides and tosylates with azide or thiocyanate in excellent to quantitative yields without any organic cosolvent or other adductive. The catalyst can be reused at least 10 times without noticeable loss of the catalytic activity. Copyright
- Li, Jing,Cao, Jing-Jing,Wei, Jun-Fa,Shi, Xian-Ying,Zhang, Li-Hui,Feng, Jin-Juan,Chen, Zhan-Guo
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supporting information; experimental part
p. 229 - 233
(2011/03/20)
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- A new synthesis of alkane and polyfluoroalkanesulfonyl chlorides
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This study describes a new and advantageous procedure for the synthesis of alkanesulfonyl chlorides (2) by the reaction of alkyl thiocyanates (1) with sulfuryl chloride in a mixture of acetic acid and water. The alkanesulfonyl chlorides were obtained in good yields.
- Benfodda, Zohra,Guillen, Franck,Arnion, Helene,Dahmani, Abdelkader,Blancou, Hubert
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experimental part
p. 355 - 361
(2010/07/16)
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- In situ-generated N-thiocyanatosuccinimide (NTS) as a highly efficient reagent for the one-pot thiocyanation or isothiocyanation of alcohols
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The first application of in situ-generated N-thiocyanatosuccinimide (NTS) for the thiocyanation of alcohols is described. This method can be easily applied for the facile conversion of primary, secondary and tertiary alcohols into the corresponding alkyl thiocyanates or alkyl isothiocyanates in good to excellent yields.
- Mokhtari, Babak,Azadi, Roya,Rahmani-Nezhad, Samira
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experimental part
p. 6588 - 6589
(2011/02/21)
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- Simple and quick preparation of α-thiocyanate ketones in hydroalcoholic media. Access to 5-aryl-2-imino-1,3-oxathiolanes
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A simple preparation on gram-scale of thiocyanate derivatives via nucleophilic substitution of halogenated compounds with SCN salts at high substrate concentrations in a few minutes and excellent yields was successfully accomplished in hydroalcoholic media. The obtained compounds were employed for the efficient synthesis of valuable 5-aryl-2-imino-1,3-oxathiolane derivatives (a one-pot approach is also presented).
- Bisogno, Fabricio R.,Cuetos, Anibal,Lavandera, Ivan,Gotor, Vicente
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supporting information; experimental part
p. 452 - 454
(2010/04/22)
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- Pharmaceutical Compositions Based on Fluorinated Sulphamides and Sulphinimides
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Pharmacuetical composition comprising compounds of formula (I): [in-line-formulae]NZ1Z2Z3 ??(I) [/in-line-formulae] in which: Z1, Z2, Z3 each independently of the others represents: a hydrogen atom; C1-C6-alkyl group; a group —SO2R3 wherein R3 represents a linear or branched C1-C12-alkyl, -alkenyl or -alkynyl group, a C3-C10-cycloalkyl group or a C6-C10-aryl group, a (C1-C6)-alkyl-(C6-C14)-aryl group, or a C5-C10-heteroaryl group; it being understood that at least one of the groups Z1, Z2, Z3 represents a group of formula (II) [in-line-formulae]X—RF—(CH2)n—SO2—??(II) [/in-line-formulae] X, RF and n being as defined in claim 1.
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Page/Page column 9
(2008/06/13)
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- Reactivity of anionic nucleophiles in ionic liquids and molecular solvents
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The nucleophilic reactivity of a representative series of anions has been measured in [hmim][ClO4] 3i, [hm2im][ClO4] 3′i, and [hmim][PF6] 3l ILs in the reaction with n-alkyl methanesulfonates and compared with that found in common molecular solvents (MeOH, DMSO, PhCl). The reactivity is found to depend on both the imidazolium cation-anion interaction and the specific solvation by water present in the IL, the water playing the main effect, in particular with hydrophilic anions. Removal of the largest quantity of water remarkably increases the ion pair reactivity in the IL up to rate constant value k comparable with those obtained in DMSO and in low polarity media (PhCl).
- Betti, Cecilia,Landini, Dario,Maia, Angelamaria
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p. 1689 - 1695
(2008/09/18)
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- Revisiting nucleophilic substitution reactions: Microwave-assisted synthesis of azides, thiocyanates, and sulfones in an aqueous medium
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A practical, rapid, and efficient microwave (MW) promoted synthesis of various azides, thiocyanates, and sulfones is described in an aqueous medium. This general and expeditious MW-enhanced nucleophilic substitution approach uses easily accessible starting materials such as halides or tosylates in reaction with alkali azides, thiocyanates, or sulfinates in the absence of any phase-transfer catalyst, and a variety of reactive functional groups are tolerated.
- Ju, Yuhong,Kumar, Dalip,Varma, Rajender S.
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p. 6697 - 6700
(2007/10/03)
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- Preparation of thiocyanates and isothiocyanates from alcohols, thiols, trimethylsilyl-, and tetrahydropyranyl ethers using triphenylphosphine/2,3-dichloro-5,6-dicyanobenzoquinone (DDQ)/n-Bu4NSCN system
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A combination of triphenylphosphine (PPh3) and 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) provides a safe and easily available mixed reagent system for the conversion of 1° and 2° alcohols, thiols, trimethylsilyl-, and tetrahydropyranyl ethers to their corresponding thiocyanates and the 3° ones to isothiocyanates in good to high yields.
- Iranpoor, Nasser,Firouzabadi, Habib,Nowrouzi, Najmeh
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p. 5498 - 5501
(2007/10/03)
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- A new diphenylphosphinite ionic liquid (IL-OPPh2) as reagent and solvent for highly selective bromination, thiocyanation or isothiocyanation of alcohols and trimethylsilyl and tetrahydropyranyl ethers
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A new diphenylphosphinite ionic liquid (IL-OPPh2) is introduced. This ionic liquid is used as both a reagent and a solvent to convert alcohols and trimethylsilyl and tetrahydropyranyl (THP) ethers into their corresponding alkyl bromides, thiocyanates or isothiocyanates in the presence of Br2 and SCN- at 80 °C. In this ionic liquid, bromination and thiocyanation of alcohols occurs highly selectively in the presence of trimethylsilyl and THP-ethers and also between different classes of alcohols. The use of this ionic liquid allows easy separation of the desired products from the phosphinate by-product.
- Iranpoor, Nasser,Firouzabadi, Habib,Azadi, Roya
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p. 5531 - 5534
(2007/10/03)
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- Efficient conversion of tetrahydropyranyl (THP) ethers to their corresponding thiocyanates with in-situ-generated Ph3P(SCN) 2
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Immediate and efficient one-pot conversion of tetrahydropyranyl (THP) ethers to their corresponding thiocyanates by in-situ-generated Ph 3P(SCN)2 is described. Primary and secondary alkyls and also benzylic THP ethers are converted to their corresponding thiocyanates in excellent yields at room temperature by this method. Copyright Taylor & Francis Inc.
- Iranpoor, Nasser,Firouzabadi, Habib,Shaterian, Hamid Reza
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p. 2093 - 2096
(2007/10/03)
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- Anion nucleophilicity in ionic liquids: A comparison with traditional molecular solvents of different polarity
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The nucleophilic reactivity of a homogeneous series of anions (halides, pseudohalides and organic anions) in the ionic liquids [hexmim] [ClO 4] and [hexmim] [PF6] has been measured in their reaction with n-alkyl methanesulfonates, and compared with that found in traditional molecular solvents of different polarity, that is, chlorobenzene, DMSO, and MeOH.
- Landini, Dario,Maia, Angelamaria
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p. 3961 - 3963
(2007/10/03)
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- Conversion of Alcohols, Thiols, Carboxylic Acids, Trimethylsilyl Ethers, and Carboxylates to Thiocyanates with Triphenylphosphine/ Diethylazodicarboxylate/NH4SCN
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A novel and highly selective method is described using triphenylphosphine/ diethylazodicarboxylate (DEAD)/NH4SCN for the conversion of alcohols, thiols, carboxylic acids, silyl ethers, and silyl carboxylates to their corresponding thiocyanates.
- Iranpoor, Nasser,Firouzabadi, Habib,Akhlaghinia, Batool,Azadi, Roya
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- Preparation of alkyl nitrates, nitrites, and thiocyanates from alcohols utilizing trichloroisocyanuric acid with triphenylphosphine
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Alcohols in acetonitrile are converted into alkyl nitrates, nitrites, or thiocyanates by the action of triphenylphosphine and trichloroisocyanuric acid along with silver nitrate, silver nitrite, or sodium thiocyanate, respectively.
- Hiegel, Gene A.,Nguyen, Jeremiah,Zhou, Yan
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p. 2507 - 2511
(2007/10/03)
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- Nucleophilic displacements in supercritical carbon dioxide under phase-transfer catalysis conditions. 2. Effect of pressure and kinetics
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The nucleophilic displacement on n-octylmesylate (n-C8H17OSO2CH3, 1) with four different anions (I-, Br-, N3-, and SCN-) is investigated under liquid-supercritical phase-transfer catalysis (LSc-PTC) conditions, i.e. in a biphase system of supercritical carbon dioxide (scCO2) and water, in the presence of both silica supported and conventional onium salts. The CO2 pressure greatly affects the concentration of 1 in the sc-phase and plays a major role on its conversion. For example, at 50 °C and with a supported PT-catalyst, the conversion of 1 into n-octyl iodide drops by a factor of 5 as the CO2 pressure is increased from 80 to 150 bar, while in the same pressure range, the solubility of n-octylmesylate in scCO2 shows a 6-fold increase, indicating that the reagent is desorbed from the catalyst. Under LSc-PTC conditions, pseudo-first-order kinetic rate constants, evaluated for the investigated reactions, show that the performance of scCO2 as a PTC solvent and the relative nucleophilicity order of the anions (N3- > I- > Br- > SCN-) are comparable to those of toluene and n-heptane. The behavior of conventional phosphonium salts in the scCO2/H2O biphase system suggests that the reaction may take place either within small droplets of PT-catalyst containing water or in a separate third liquid phase of the PT-catalyst itself.
- Loris, Alessandro,Perosa, Alvise,Selva, Maurizio,Tundo, Pietro
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p. 4046 - 4051
(2007/10/03)
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- Efficient conversion of thiols to thiocyanates by in situ generated Ph3P(SCN)2
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A new, novel, rapid and simple method is described for the one-pot conversion of thiols to thiocyanates by use of in situ generated PPh3(SCN)2 at room temperature.
- Iranpoor, Nasser,Firouzabadi, Habib,Shaterian, Hamid Reza
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p. 3439 - 3441
(2007/10/03)
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- Thiocyanation of alkyl halides with alkyl thiocyanates in the presence of quaternary phosphonium halides
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Alkyl thiocyanates undergo simple SN2 reactions with the counter ions of quaternary phosphonium salts in nonpolar solvents and thiocyanate ions are liberated as the leaving ion. Depending on the nucleophile, the reaction proceeded irreversibly or reversibly. The reaction of benzyl thiocyanate with azide ions afforded a quantitative yield of benzyl azide. The reactions of alkyl thiocyanates with halide ions gave an equilibrium mixture where the reverse reaction of the alkyl halides produced with the liberated thiocyanate ions took place simultaneously. Thus, thiocyanate-halide exchange reactions between an alkyl thiocyanate and an alkyl halide were possible in the presence of a catalytic amount of a quaternary salt.
- Ohtani, Noritaka,Murakawa, Shigeki,Watanabe, Kohji,Tsuchimoto, Daisuke,Sato, Daiki
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p. 1851 - 1856
(2007/10/03)
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- Efficient conversion of silyl ethers to thiocyanates with Ph3P(SCN)2
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A new and efficient method for the conversion of primary and secondary alkyl, aryl, allyl and benzyl silyl ethers to their corresponding thiocyanates by in-situ generation of Ph3P(SCN)2 is described. The reactions occur immediately at room temperature and provide high to excellent yields of thiocyantes.
- Iranpoor,Firouzabadi,Shaterian
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- Efficient one-pot thiocyanation of primary, secondary and tertiary alcohols by in situ generation of Ph3P(SCN)2. A modified procedure
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The preparation of Ph3P(SCN)2 is modified by using a combination of Ph3P, NH4SCN and Br2 at room temperature for the efficient conversion of primary, secondary and tertiary alcohols to their corresponding thiocyanates in excellent yields.
- Iranpoor,Firouzabadi,Shaterian
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p. 676 - 677
(2007/10/03)
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- CYCLOPHOSPHAZENIC POLYPODANDS AS POWERFUL CATION COMPLEXING AGENTS, EFFICIENT PHASE-TRANSFER CATALYSTS AND ANION ACTIVATORS
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A survey dealing with cyclophosphazenic polypodands 3a-c, a new class of "octopus-like" molecules is reported.These many-armed ligands are powerful complexing agents of alkali metal salts and hence behave as very efficient catalysts in many reations (nucleophilic substitutions, eliminations, alkylations, oxidations, reductions) under solid-liquid and liquid-liquid phase-transfer catalysis conditions.Their catalytic activity is much better than that of the open-chain analogues PEGs 4, 5 and TRIDENT-1, 6.Moreover, anion activation realized by cyclophosphazenic polypodands, both of homogeneous and heterogeneous systems, is comparable with that obtained with the more sophisticated and expensive crown ethers.
- Landini, Dario,Maia, Angelamaria,Podda, Gianni
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p. 583 - 588
(2007/10/03)
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- Mechanism and Anion Activation in Solid-Liquid Phase-transfer Reactions Catalysed by Cyclophosphazenic Polypodands. Comparison with Cyclic Analogue Crown Ethers
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A kinetic study of the nucleophilic substitution of the methanesulfonic group by anions (Cl-, Br-, I-, SCN-, C6H5O-, C6H5CH2COO-) catalysed by cyclophosphazenic polypodands has been performed under solid-liquid phase-transfer conditions.The results obtained show that the mechanism of PTC previously found for cyclic ligands (crown ethers, cryptands) also operates in the case of these open-chain ligands: the attack by the anionic nucleophile on the substrate occurs in the organic phase and is rate determining of the overall process.The nucleophilicity scales found (I- > C6H5O- ca.SCN- > C6H5CH2COO-; I- > Br- > Cl-) as well as the anion activation are comparable with those found for cyclic crown ethers.This indicates that the anionic reactive species involved are similar in the complexes of both ligands.
- Landini, Dario,Maia, Angelamaria,Podda, Gianni,Secci, Daniela,Yan, Yong Ming
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p. 1721 - 1724
(2007/10/02)
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- Novel compositions
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Sulfur-substituted alkenyl compounds, synthesis thereof, intermediates therefor, and the use of the compounds to control pests.
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- Triphenylsulfonium Salts as Effective Phase Transfer Catalysts under Alkaline Conditions
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Triphenylsulfonium salts work as effective phase transfer catalysts for nucleophilic substitution reactions on alkyl halides (e.g. 1) and addition reaction of dichlorocarbene to cyclohexene (8) under strongly alkaline conditions.
- Kondo, Shuji,Takeda, Yuji,Tsuda, Kazuichi
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p. 862 - 864
(2007/10/02)
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- Nucleophilic Substitution Reactions of Alkyl Halides By Using New Polymer-Supported Reagents Containing Hemin
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A new polymer reagent consisting of hemin, divinylbenzene, and 2-methyl-5-vinylpyridine was synthesized by suspension copolymerization.Substitution reactions of primary, secondary, and tertiary alkyl halides with the hemin copolymer combined with cyanide, azide, and thiocyanate ions were given satisfactory yields.This reaction mechanism was revealed to be a SNi type on the basis of stereochemical study.The hemin copolymer was not only a polymer-supported reagent with functional capabilities, but also served to separate the product from the reaction mixture.
- Saito, Kiyoshi,Harada, Kaoru
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p. 2562 - 2566
(2007/10/02)
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- Sulfonium Salts as Liquid-Liquid Phase-Transfer Catalysts
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Lauryldimethylsulfonium and tri(n-butyl)sulfonium salts serve as highly efficient catalysts for two-phase reactions.
- Kondo, Shuji,Takeda, Yuji,Tsuda, Kazuichi
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p. 403 - 404
(2007/10/02)
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- β-Cyclodextrin-Epichlorohydrin Copolymers as Efficient Catalysts in Phase-Transfer-Catalyzed Nucleophilic Substitution Reactions
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Copolymers of β-cyclodextrin (β-CD) with epichlorohydrin showed much higher phase-transfer catalytic activity than β-CD in liquid-liquid two-phase nucleophilic displacement reactions.The enhanced efficiency of the polymer catalysts was attributed to the cooperative effect of more than one β-CD group in polymers in bringing a substrate from an organic phase to an aqueous phase.
- Tanaka, Nobuo,Yamaguchi, Atsumi,Araki, Yoshio,Araki, Mikio
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p. 715 - 718
(2007/10/02)
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- POLYMER SULFOXIDES BASED ON POLY(VINYL ALCOHOL) AS EFFECTIVE CATALYSTS OF NUCLEOPHILIC SUBSTITUTION REACTIONS
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Using the addition of alcohols to ethyl vinyl sulfoxide, a number of 2-alkoxyethyl ethyl sulfoxides were prepared, containing the following alkyls: methyl, ethyl, isopropyl, benzyl, and cyclohexyl.With a 10 mole percent excess of alcohol the extent of the reaction was 70-95percent.By a polymeranalogous reaction with poly(vinyl alcohol) and poly(ethylene-co-vinyl alcohol), copolymers poly and poly were prepared; the reaction with polymer alcohols requires the use of excess ethyl vinyl sulfoxide.These polymer sulfoxides were tested as catalysts of nucleophilic substitution reactions, using reactions of 1-bromooctane with sodium phenoxide, sodium iodide and potassium thiocyanate.They are more effective catalysts than polymer sulfoxides based on crosslinked poly(styrene) under the conditions of a two-phase (S-L) and three-phase (L-S-L) catalysis.
- Hrudkova, Hana,Cefelin, Pavel,Janout, Vaclav
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p. 2204 - 2211
(2007/10/02)
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- SOLID-PHASE COSOLVENTS. A POLYMER ANALOG OF N-METHYL-2-PYRROLIDONE BASED ON CROSSLINKED POLYSTYRENE
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Polymer analogs of N-methyl-2-pyrrolidone were prepared by reacting crosslinked polystyrene with N-hydroxymethyl-2-pyrrolidone.These polymers are effective catalysts of nucleophilic substitution reactions carried out under liquid-solid (L-S) and liquid-solid-liquid conditions.
- Janout, Vaclav,Cefelin, Pavel
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p. 3525 - 3528
(2007/10/02)
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- Tetrakis-sulphoxides: a New Type of Phase-transfer Catalyst for Nocleophilic Displacements and Alkylations
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Tetrakis(alkylsulphinylmethyl)methanes have been shown to serve as good phase-transfer catalysts which accelerate SN2 type displacements of octyl bromide with various nucleophiles (thiocyanate, cyanide, phenoxide, and thiolate) in solid-liquid two-phase systems.Alkylation of phenylacetonitrile with alkyl halides has also been carried out in liquid-liquid two-phase systems in the presence of the above sulphoxides to afford the corresponding mono-alkylated products in high yields.
- Fujihara, Hisashi,Imaoka, Koji,Furukawa, Naomichi,Oae, Shigeru
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p. 333 - 336
(2007/10/02)
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- COPOLYESTERAMIDES CONTAINING POLY(ETHYLENE OXIDE) SOFT SEGMENTS AS NEW AND EFFICIENT PHASE-TRANSFER CATALYSTS
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Copolyesteramides, 1, prepared by melt polycondensation of N,N'-bis(4-methoxycarbonylbenzoyl)hexamethylenediamine, 2, 1,6-hexanediol and poly(ethylene glycol) (PEG 1000), are a new class of polymeric phase-transfer catalysts.Their catalytic activity has been tested in nucleophilic aliphatic substitutions, eliminations, alkylations of activated methylene groups, dichlorocyclopropanation of C=C double bonds, reductions of ketones to alcohols and oxydation of primary alcohols to aldehydes.
- Montanari, Fernando,Penso, Michele,Fortuna, Giorgio della,Re, Alberto
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p. 427 - 432
(2007/10/02)
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- Phase-Transfer Reactions Catalyzed by Lipophilic Cryptands and Dicyclohexano-18-crown-6: Dehydrating Effect of Concentrated Aqueous Alkaline Solutions
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A study of how the concentration of aqueous KOH affects the hydration and hence the reactivity of anions (Cl-, Br-, I-, SCN-, N3-) in aliphatic nucleophilic substitutions catalyzed by lipophilic cryptand (1a) and dicyclohexano-18-crown-6 (DCH18C6) (2) under phase-transfer conditions is reported.A comparison with the same reactions performed in classical liquid-liquid PTC and homogeneous anhydrous conditions is also included.Unlike quaternary onium salts, even at the highest KOH concentrations (53percent; ie., conditions in which aH2O ca. 0), water in the presence of 1a is not completely removed.Residual hydration depends on the nature of the anion and is the highest for anions with localized and/or less polarizable charge, such as Cl-, Br-, and N3-.As a consequence, rate constants noticeably increase in comparison with those found under conventional PTC conditions but do not reach those of anhydrous solutions.The different behavior of cryptates and quaternary salts is discussed on the basis of the different topology of the two systems.Behavior of crown ethers is in between that of quaternary salts and cryptates, since residual hydration in the presence of 53percent aqueous KOH is lower than that of cryptates, whereas anionic reactivity becomes practically identical with that found under anhydrous conditions.
- Landini, Dario,Maia, Angelamaria,Montanari, Fernando
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p. 2917 - 2923
(2007/10/02)
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- Reaction Mechanism and Factors Influencing Phase-Transfer Catalytic Activity of Crown Ethers Bonded to a Polystyrene Matrix
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Polymer-supported crown ethers 1 and 2 were prepared by reaction of 1percent cross-linked chloromethylated polystyrene, with (hydroxymethyl)- and (ο-hydroxynonyl)-18-crown-6, respectively.Their phase-transfer catalytic activity was tested in anion-promoted nucleophilic aliphatic substitutions and compared with that of structurally similar soluble crown ethers and of polymer-supported and soluble phosphonium salts.Catalytic efficiency of crown ethers 1 and 2 depends on a combination of three parameters: the nature of the nucleophile, the percent ring substitution, and the presence of a spacer chain.Complexation of potassium salts largely depends on the anion, with a high degree for soft nucleophiles like I- and SCN- and a lower degree for smaller and less polarizable nucleophiles like Br- and CN-.This corresponds to high and low catalytic efficiency, respectively.Spaced catalysts 2 are on the average 2-4 times more reactive than directly bonded catalysts 1.The extent of ring substitution noticeably influences catalytic activity, the variation depending on the nature of the nucleophile.With soft nucleophiles the observed rates progressively diminish as loading increases, following a linear correlation on a semilogarithmic scale, whereas with harder nucleophiles the observed rates reach a maximum at 30percent ring substitution.All reactions follow a pseudo-first-order kinetics, and rates are linearly dependent on molar equivalents of polymer-supported crown ethers.Hydrophilicity of catalysts and the extent of complexation increase with the extent of loading.Phenol is exclusively O-alkylated, even in the presence of the most hydrophilic catalysts.The data, as a whole, lead to the conclusion that the reactions occur in the organic shell surrounding a complexed crown ether, following a mechanism analogous to that demonstrated for immobili zed quaternary salts.
- Anelli, Pier Lucio,Czech, Bronislaw,Montanari, Fernando,Quici, Silvio
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p. 861 - 868
(2007/10/02)
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- Sulphoxide Substituted Pyridines as Phase-transfer Catalysts for Nucleophilic Displacements and Alkylations
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2-Methylsulphinyl-, 2-methylsulphinylmethyl-, 2,6-bis(methylsulphinyl)-, 2,6-bis(methylsulphinylmethyl)-pyridines, bis(2-pyridylmethyl)sulphoxide, and 2-methylsulphinylpyridine N-oxide have been prepared.These sulphoxides served as good phase-transfer catalysts which accelerate SN2 type displacements of octyl bromide with various nucleophiles (thiolate, cyanide, thiocyanate, and phenoxide) in solid-liquid two-phase systems.Alkylations of phenylacetonitrile and benzyl methyl ketone with alkyl halides were also carried out in liquid-liquid two-phase systems in the presence of the above sulphoxides to afford the corresponding monoalkylated products in high yields.Pyridine derivatives bearing polysulphinyl groups were found to be even more effective catalysts for these two-phase alkylations.Neither 2-methylthio- nor 2-methylsulphonyl-pyridine catalysed SN2 type displacement reactions effectively.
- Furukawa, Naomichi,Ogawa, Satoshi,Kawai, Tsutomu,Oae, Shigeru
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p. 1833 - 1838
(2007/10/02)
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- A POLYMER ANALOG OF DIMETHYL SULFOXIDE: CATALYTIC ACTIVITY OF CROSSLINKED POLYMERIC SULFOXIDES IN NUCLEOPHILIC REACTIONS UNDER THE CONDITIONS OF THREE-PHASE CATALYSIS
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An investigation was made of the catalytic activity of polymeric sulfoxides, P-(-CH2SOCH2-)n-R where P is the crosslinked polystyrene matrix (divinylbenzene as the crosslinking agent), R is H or CH3, and n is 1, 2, or 3, in nucleophilic substitution reactions between alkyl bromides and phenoxides, iodides, thicyanates and cyanides of alkali metals under the conditions of liquid-solid-liquid (L-S-L) three-phase catalysis (TC).The effect of the structure of polymeric sulfoxides on their activity under the conditions of TC was studied; the strongest catalytic activity was found with polymeric sulfoxides having the optimal ratio between the functional groups and hydrophobic polymer matrix.Extension of the pendant sulfoxide chain has no pronounced effect of the catalytic activity of polymers.
- Janout, Vaclav,Hrudkova, Hana,Cefelin, Pavel
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p. 2096 - 2102
(2007/10/02)
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