516-91-6Relevant academic research and scientific papers
A facile and green protocol for nucleophilic substitution reactions of sulfonate esters by recyclable ionic liquids [bmim][X]
Liu, Yajun,Xu, Yongnan,Jung, Sun Ho,Chae, Junghyun
, p. 2692 - 2698,7 (2012/12/12)
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.
A facile and green protocol for nucleophilic substitution reactions of sulfonate esters by recyclable ionic liquids [bmim][X]
Liu, Yajun,Xu, Yongnan,Jung, Sun Ho,Chae, Junghyun
, p. 2692 - 2698 (2013/01/15)
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.
Iron(III)-catalyzed halogenations by substitution of sulfonate esters
Ortega, Nuria,Feher-Voelger, Andres,Brovetto, Margarita,Padron, Juan I.,Martin, Victor S.,Martin, Tomas
experimental part, p. 963 - 972 (2011/06/20)
A novel halogenation reaction from sulfonates catalyzed by iron(III) is described. The reaction can be performed as a stoichiometric or a catalytic version. This reaction provides a convenient strategy for the efficient access to structurally diverse secondary chlorides, bromides and iodides. The stereochemical course of the reaction is governed by the substrate and the experimental conditions. Secondary alcohols modified as quisylates or pysylates are substantially more reactive. Aliphatic quisylates proceed with overall inversion of configuration under catalytic conditions. Chemoselectivity in bismesylates was observed in favour of the secondary mesylate. Additionally, based on the experimental results, a possible catalytic cycle for the halogenation has been proposed.
In situ phosphine oxide reduction: A catalytic appel reaction
Van Kalkeren, Henri A.,Leenders, Stefan H. A. M.,Hommersom, C. Rianne A.,Rutjes, Floris P. J. T.,Van Delft, Floris L.
supporting information; experimental part, p. 11290 - 11295 (2011/10/19)
Several important reactions in organic chemistry thrive on stoichiometric formation of phosphine oxides from phosphines. To avoid the resulting burden of waste and purification, cyclic phosphine oxides were evaluated for new catalytic reactions based on in situ regeneration. First, the ease of silane-mediated reduction of a range of cyclic phosphine oxides was explored. In addition, the compatibility of silanes with electrophilic halogen donors was determined for application in a catalytic Appel reaction based on in situ reduction of dibenzophosphole oxide. Under optimized conditions, alcohols were effectively converted to bromides or chlorides, thereby showing the relevance of new catalyst development and paving the way for broader application of organophosphorus catalysis by in situ reduction protocols. Copyright
Catalytic phosphorus(V)-mediated nucleophilic substitution reactions: Development of a catalytic appel reaction
Denton, Ross M.,An, Jie,Adeniran, Beatrice,Blake, Alexander J.,Lewis, William,Poulton, Andrew M.
experimental part, p. 6749 - 6767 (2011/10/02)
Catalytic phosphorus(V)-mediated chlorination and bromination reactions of alcohols have been developed. The new reactions constitute a catalytic version of the classical Appel halogenation reaction. In these new reactions oxalyl chloride is used as a consumable stoichiometric reagent to generate the halophosphonium salts responsible for halogenation from catalytic phosphine oxides. Thus, phosphine oxides have been transformed from stoichiometric waste products into catalysts and a new concept for catalytic phosphorus-based activation and nucleophilic substitution of alcohols has been validated. The present study has focused on a full exploration of the scope and limitations of phosphine oxide catalyzed chlorination reactions as well as the development of the analogous bromination reactions. Further mechanistic studies, including density functional theory calculations on proposed intermediates of the catalytic cycle, are consistent with a catalytic cycle involving halo- and alkoxyphosphonium salts as intermediates.
Practical synthesis of 3β-amino-5-cholestene and related 3β-halides involving i-steroid and retro-i-steroid rearrangements
Sun, Qi,Cai, Sutang,Peterson, Blake R.
supporting information; experimental part, p. 567 - 570 (2009/07/18)
(Equation Presented) Derivatives of 3β-amino-5-cholestene (3β-cholesterylamine) are of substantial interest as cellular probes and have potential medicinal applications. However, existing syntheses of 3β-amino-5-cholestene are of limited preparative utility. We report here a practical method for the stereoselective preparation of 3β-amino-5- cholestene, 3β-chloro-5-cholestene, 3β-bromo-5-cholestene, and 3β-iodo-5-cholestene from inexpensive cholesterol. A sequential i-steroid/retro-i-steroid rearrangement promoted by boron trifluoride etherate and trimethylsilyl azide converted cholest-5-en-3β-ol methanesulfonate to 3β-azido-cholest-5-ene with retention of configuration in 93% yield.
Stereoretentive halogenations and azidations with titanium(IV) enabled by chelating leaving groups
Lepore, Salvatore D.,Mondal, Deboprosad,Song, Ye Li,Bhunia, Anjan K.
supporting information; body text, p. 7511 - 7514 (2009/03/12)
Titaniumdoes it again! With the help of nucleophile-assisting leaving groups (NALGs), alkyl bromides, iodides, and, for the first time, azides are obtained from sulfonates withcomplete retention of configuration. Critical to the design of these new titanium(IV) reactions has been the use of NALGs which are thought to chelate the Lewis acid reagent in the transition state promoting an SNi-type mechanism. (Chemical Equation Presented)
Silicaphosphine (Silphos): A filterable reagent for the conversion of alcohols and thiols to alkyl bromides and iodides
Iranpoor, Nasser,Firouzabadi, Habib,Jamalian, Arezu,Kazemi, Foad
, p. 5699 - 5704 (2007/10/03)
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.
Fluorous solvent as a new phase-screen medium between reagents and reactants in the bromination and chlorination of alcohols
Nakamura, Hiroyuki,Usui, Taikou,Kuroda, Hirokazu,Ryu, Ilhyong,Matsubara, Hiroshi,Yasuda, Shinji,Curran, Dennis P.
, p. 1167 - 1169 (2007/10/03)
(Matrix presented) A perfluorohexane layer regulates the rate of reagent transport in the bromination and chlorination of alcohols. A fluorous triphasic U-tube method is effective for lighter reagents; the thionyl chloride layer (yellow) vanishes, and the chlorides are obtained from the right top organic layer in the chlorination of alcohols.
SYNTHESIS OF TRITERPENE AND STEROID GLYCOSIDES
Uvarova, Nina I.,Atopkina, Lyubov N.,Elyakov, Georgi B.
, p. 33 - 42 (2007/10/02)
The glycosylation of cholesterol, β-sitosterol, 28-O-acetylbetulin, and betulin with acylated glycosyl halides in the presence of Hg(OAc)2, Hg(CN)2, CdCO3, Ag2O, Ag2CO3, and HgO + HgBr2 usually gives acylated αβ-glycosides accompanied by acetates, ethers, and bromo and unsaturated derivatives of the initial alcohols.The use of Hg(CN)2 gave mainly β anomers (40-87percent), whereas α anomers preponderated when Hg(OAc)2 was the catalyst.When there was a deficiency of hydrogen halide acceptor and in the presence of the acidic catalyst HgBr2*HBr, the β anomer, produced initially, underwent anomerisation.Cholesteryl α-D-glucopyranoside tetra-acetate (48percent) was obtained by anomerisation of the β anomer.
