- Copper nitrate/acetic acid as an efficient synergistic catalytic system for the chemoselective tetrahydropyranylation of alcohols and phenols
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Tetrahydropyranylation of alcohols and phenols was accomplished successfully using copper nitrate and acetic acid as a synergistic catalyst at room temperature under solvent-free condition. Compared with other synergistic catalytic systems, copper nitrate/acetic acid proved to be the most efficient. Both alcohols (primary, secondary, tertiary, benzylic, cyclic, allyl, cinnamyl, and furyl) and phenols reacted smoothly in high yields. Graphical abstract: [Figure not available: see fulltext.]
- Wang, Min,Song, Zhi-Guo,Gong, Hong,Jiang, Heng
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Read Online
- Metal benzenesulfonates/acetic acid mixtures as novel catalytic systems: Application to the protection of a hydroxyl group
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A surprising synergistic effect has been discovered in mixtures of metal benzenesulfonates (Co, Al, Ni, Zn, Cd, Pr, La, Cu, Mn) and acetic acid, leading to active catalytic systems for the tetrahydropyranylation of alcohols and phenols to produce tetrahydropyranyl ethers. All reactions proceed mildly and efficiently with moderate to high yields at room temperature without solvent. After the reaction, the metal benzenesulfonate can be easily recovered and reused many times. The efficiency of these systems might result from the "double activation" by Bronsted and Lewis acid catalysis.
- Wang, Min,Gao, Jingjing,Song, Zhiguo
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Read Online
- Copper p-toluenesulfonate/acetic acid: A recyclable synergistic catalytic system for the tetrahydropyranylation of alcohols and phenols
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Copper p-toluenesulfonate/acetic acid was found to be an efficient, chemoselective synergistic catalytic system, with catalyst loading as low as 0.3 mol% leading to clean, high-yielding tetrahydropyranylation of a variety of alcohols and phenols. By simple phase-separation, copper p-toluenesulfonate can be easily recovered and reused for several times without deterioration in catalytic activity.
- Wang, Min,Song, Zhi-Guo,Jiang, Heng,Gong, Hong
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Read Online
- Highly selective tetrahydropyranylation/dehydropyranylation of alcohols and phenols using porous phenolsulfonic acid-formaldehyde resin catalyst under solvent-free condition
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An efficient protocol for solvent-free chemoselective tetrahydropyranylation/depyranylation of alcohols and phenols is reported herein using mesoporous Phenolsulfonic Acid Formaldehyde Resins as a heterogeneous acid catalyst. The catalyst successfully performed chemoselective protection and deprotection reactions of a wide range of substrates ranging from primary to secondary and tertiary alcohols and also phenols. The reactions were carried out at ambient temperature under solvent-free condition (SolFC) which resulted in high yields within a very short time. FT-IR, TEM, SEM, EDS and TG-DSC analysis techniques were employed to characterize the synthesized polymeric catalyst. The chemoselective nature of our method was confirmed using 13C DEPT-135 NMR studies. The polymer catalyst was found to be recoverable even after 10th catalytic cycle without much depreciation in its activity. The heterogeneity of the catalyst was verified by hot filtration method. Good yield, energy and cost- effective method, solvent-free protocol, mild reaction conditions, no inert atmosphere, metal-free heterogeneous polymer catalyst and excellent recoverability of the catalyst are notable milestones of the reported protocol.
- Rajkumari, Kalyani,Laskar, Ikbal Bahar,Kumari, Anupama,Kalita, Bandita,Rokhum, Lalthazuala
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- Zwitterionic imidazolium salt: An efficient organocatalyst for tetrahydropyranylation of alcohols
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An aprotic imidazole based zwitterionic-salt, 4-(3-methylimidazolium)-butane sulfonate has been found to be an efficient organocatalyst for tetrahydropyranylation by the reaction of 3,4-dihydro-2H-pyran (DHP) and different aliphatic alcohols as well as various phenolic compounds. The notable advantages of the present method are general applicability to various alcohols, clean reaction, production of no hazardous waste, open air reaction conditions and high yields. The catalyst can be reused without the loss of significant catalytic activity.
- Mahato, Sachinta,Chatterjee, Rana,Chakraborty Ghosal, Nirnita,Majee, Adinath
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supporting information
p. 1905 - 1915
(2017/10/07)
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- Croconamides: A new dual hydrogen bond donating motif for anion recognition and organocatalysis
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We introduce bis-aryl croconamides as a new member in the family of dual hydrogen bonding anion receptors. In this study a series of croconamides are synthesised, and the selectivity for anion binding is investigated (Cl- > Br- > I- in CH2Cl2). The croconamides exhibit different structures in the crystal phase depending on the substituents on the aromatic rings, and furthermore, the crystal structure revealed the presence of tautomers. DFT calculations elucidated the complex structures formed upon addition of anion to the croconamides, confirming the order of association constants towards the halogen anions. The use of croconamides as organocatalysts in a proof-of-concept study is demonstrated in the formation of THP ethers. In addition to this, construction of a Hammet plot further elucidates the mechanism in action on formation of THP ethers.
- Jeppesen, Anne,Nielsen, Bjarne E.,Larsen, Dennis,Akselsen, Olivia M.,S?lling, Theis I.,Brock-Nannestad, Theis,Pittelkow, Michael
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supporting information
p. 2784 - 2790
(2017/04/03)
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- Tetrahydropyranylation of alcohols and phenols catalyzed by a new multi-wall carbon nanotubes-bound tin(IV) porphyrin
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Abstract: In the present study, tetrahydropyranylation of alcohols and phenols with 3,4-dihydro-2H-pyran (DHP) using tetrakis(p-aminophenyl)porphyrinatotin(IV) trifluoromethanesulfonate, [SnIV(TNH2PP)(OTf)2], and tetrakis(p-aminophenyl)porphyrinatotin(IV) tetrafluoroborate, [SnIV(TNH2PP)(BF4)2], supported on multi-wall carbon nanotubes as new catalytic systems is investigated. These new catalysts, [SnIV(TNH2PP)(OTf)2@MWCNT] and [SnIV(TNH2PP)(BF4)2@MWCNT], were characterized using elemental analysis, FT-IR spectroscopic techniques, scanning electron microscopy and diffuse reflectance UV–Vis spectroscopic methods. In these catalytic systems, an optimization on the amounts of catalysts and amount of DHP was done in the tetrahydropyranylation of alcohols and phenols with DHP and the best outcomes were received in the presence of 0.01?mmol (40?mg) of [SnIV(TNH2PP)(OTf)2@MWCNT] and [SnIV(TNH2PP)(BF4)2@MWCNT] with 2?mmol of DHP. Efficiency and reusability are two important features of these new heterogenized catalysts for tetrahydropyranylation of primary, secondary and tertiary alcohols as well as phenols at room temperature. These catalysts were recovered several times with no loss on their initial activity, which indicates their high reusability and stability. Graphical Abstract: In the present study, tetrahydropyranylation of alcohols and phenols with 3,4-dihydro-2H-pyran (DHP) using tetrakis(p-aminophenyl)porphyrinatotin(IV) trifluoromethanesulfonate, [SnIV(TNH2PP)(OTf)2], and tetrakis(p-aminophenyl)porphyrinatotin(IV) tetrafluoroborate, [SnIV(TNH2PP)(BF4)2], supported on multi-wall carbon nanotubes as new catalytic systems is investigated. These new catalysts, [SnIV(TNH2PP)(OTf)2@MWCNT] and [SnIV(TNH2PP)(BF4)2@MWCNT], were characterized using elemental analysis, FT-IR spectroscopic techniques, scanning electron microscopy and diffuse reflectance UV–Vis spectroscopic methods. In these catalytic systems, an optimization on the amounts of catalysts and amount of DHP was done in the tetrahydropyranylation of alcohols and phenols with DHP and the best outcomes were received in the presence of 0.01?mmol (40?mg) of [SnIV(TNH2PP)(OTf)2@MWCNT] and [SnIV(TNH2PP)(BF4)2@MWCNT] with 2?mmol of DHP. Efficiency and reusability are two important features of these new heterogenized catalysts for tetrahydropyranylation of primary, secondary and tertiary alcohols as well as phenols at room temperature. These catalysts were recovered several times with no loss on their initial activity, which indicates their high reusability and stability. [Figure not available: see fulltext.].
- Gharaati, Shadab,Kargar, Hadi,Falahati, Ali Mohammad
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p. 1169 - 1178
(2017/05/15)
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- Thiosemicarbazone organocatalysis: Tetrahydropyranylation and 2-deoxygalactosylation reactions and kinetics-based mechanistic investigation
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The first use of thiosemicarbazone-based organocatalysis was demonstrated on both tetrahydropyranylation and 2-deoxygalactosylation reactions. The organocatalysts were optimised using kinetics-based selection. The best catalyst outperformed previously reported thiourea catalysts for tetrahydropyranylation by 50-fold. Hammett investigations of both the organocatalyst and the substrate indicate an oxyanion hole-like reaction mechanism.
- Larsen, Dennis,Langhorn, Line M.,Akselsen, Olivia M.,Nielsen, Bjarne E.,Pittelkow, Michael
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p. 7978 - 7982
(2017/11/28)
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- Supported N-propylsulfamic acid onto Fe3O4 magnetic nanoparticles as a reusable and efficient nanocatalyst for the protection/deprotection of hydroxyl groups and protection of aldehydes
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N-propylsulfamic acid supported onto Fe3O4 magnetic nanoparticles (MNPs-PSA) as an efficient and magnetically reusable nanocatalyst has been reported for the tetrahydropyranylation/depyranylation of a wide variety of alcohols and phenols by changing the solvent medium. Also, the protection of aldehydes as acylals using Ac2O in the presence of catalytic amount MNPs-PSA in good to high yields at room temperature under solvent-free conditions is described. After completing the reaction, the catalyst was easily separated from the reaction mixture with the assistance of an external magnetic field and reused for several consecutive runs without significant loss of their catalytic efficiency.
- Rostami, Amin,Tahmasbi, Bahman,Abedi, Fatemeh
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p. 3689 - 3701
(2016/04/05)
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- Selective tetrahydropyranylation of alcohols and phenols using titanium(IV) salophen trifluoromethanesulfonate as an efficient catalyst
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Titanium(IV) salophen trifluoromethanesulfonate, [TiIV(salophen)(OSO2CF3)2], as a catalyst enables selective tetrahydropyranylation of alcohols and phenols with 3,4-dihydro-2H-pyran. Using this catalytic system, primary, secondary and tertiary alcohols, as well as phenols, were converted to their corresponding tetrahydropyranyl ethers in high yields and short reaction times at room temperature. Investigation of the chemoselectivity of this method showed discrimination between the activity of primary alcohols in the presence of secondary and tertiary alcohols and phenols. This heterogenized catalyst could be reused several times without loss of its catalytic activity. Copyright
- Yadegari, Maryam,Moghadam, Majid
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p. 872 - 875
(2016/09/20)
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- P4VPy–CuO nanoparticles as a novel and reusable catalyst: application at the protection of alcohols, phenols and amines
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P4VPy–CuO nanoparticles were synthesized using ultrasound irradiations. Relevant properties of the synthesized nanoparticles were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. After identification, the prepared reagent was used for the promotion of different types of protection reactions of alcohols, phenols and amines. Easy workup, short reaction times, excellent yields, relatively low cost and reusability of the catalyst are the striking features of the reported methods.
- Shirini, Farhad,Fallah-Shojaei, Abdollah,Abedini, Masoumeh,Samavi, Laleh
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p. 1699 - 1712
(2016/07/27)
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- Highly efficient protection of alcohols and phenols catalysed by tin porphyrin supported on MIL-101
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The catalytic activity of 5,10,15,20-tetrakis(4-aminophenyl)porphyrinatotin(IV) trifluoromethanesulfonate, [SnIV(TNH2PP)(OTf)2], supported on chloromethylated MIL-101, was investigated in the trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) and also their tetrahydropyranylation with 3,4-dihydro-2H-pyran. Excellent yields, mild reaction conditions, short reaction times and reusability of the catalyst without significant decrease in its initial activity are noteworthy advantages of this supported catalyst.
- Zadehahmadi, Farnaz,Tangestaninejad, Shahram,Moghadam, Majid,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj,Kardanpour, Reihaneh
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p. 209 - 215
(2015/03/30)
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- 3,5-Dinitrobenzoic acid catalyzed synthesis of 2,3-unsaturated O- and S-glycosides and tetrahydropyranylation of alcohols and phenols
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A simple procedure for the synthesis of 2,3-unsaturated glycosides in acetonitrile and tetrahydropyranylation of alcohols and phenols in dichloromethane in the presence of 3,5-dinitrobenzoic acid is described. A variety of alcohols and thiols are reacted with glycals to give the desired products in high yields with high α-selectivity.
- Bodipati, Naganjaneyulu,Palla, Srinivasa Rao,Komera, Venkateshwarlu,Peddinti, Rama Krishna
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supporting information
p. 6878 - 6881
(2015/02/02)
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- Short communication: Catalytic tetrahydropyranylation of phenols and alcohols using vanadium(V)-substituted polyoxomolybdates
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Alcohols and phenols were tetrahydropyranylated in the presence of H 7[PMo8V4O40] in good to excellent yields in acetonitrile and under solventfree reaction conditions. A mild and convenient method for the formation and deprotection of ethers (THP ethers) is described. The formation of THP ethers from the corresponding alcohols was accomplished in the presence of acid-sensitive functional groups.
- Gharib, Ali,Jahangir, Manouchehr
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experimental part
p. 287 - 296
(2012/05/20)
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- Polystyrene-supported GaCl3: A new, highly efficient and recyclable heterogeneous Lewis acid catalyst for tetrahydropyranylation of alcohols and phenols
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A new, simple and highly chemoselective method for tetrahydropyranylation of alcohols and phenols with 3,4-dihydro-2H-pyran (DHP) in the presence of polystyrene-supported gallium trichloride (PS/GaCl3) as a highly active and reusable heterogeneous Lewis acid catalyst at room temperature is presented.
- Rahmatpour, Ali
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p. 66 - 71,6
(2012/12/11)
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- Tetrahydropyranylation of alcohols and phenols catalyzed by a new polystyrene-bound tin(IV) porphyrin
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In the present work, tetrahydropyranylation of alcohols and phenols with 3,4-dihydro-2H-pyran (DHP) catalyzed by tetrakis(p-aminophenyl) porphyrinatotin(IV) trifluoromethanesulfonate, [SnIV(TNH 2PP)(OTf)2], supported on chloromethylated polystyrene is reported. The prepared catalyst was characterized by elemental analysis, FT-IR and diffuses reflectance UV-Vis spectroscopic methods. This new heterogenized catalyst was found as efficient and reusable catalyst for tetrahydropyranylation of primary, secondary and tertiary alcohols as well as phenols at room temperature.
- Moghadam, Majid,Tangestaninejad, Shahram,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj,Gharaati, Shadab
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experimental part
p. 95 - 101
(2011/04/22)
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- Synthesis of sulfonic acid functionalized carbon catalyst from glycerol pitch and its application for tetrahydropyranyl protection/deprotection of alcohols and phenols
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A novel carbon catalyst with -SO3H, -OH and -COOH functional groups was prepared from glycerol pitch by in situ partial carbonization and sulfonation with sulfuric acid. The activity of the catalyst was investigated through tetrahydropyranylation and dehydropyranylation of a wide variety of alcohols and phenols at room temperature by changing the solvent medium from dichloromethane to methanol. Excellent yields, short reaction times, easy and quick isolation of the products and reusability of the catalyst are the main attractions of this method. The novel carbon catalyst holds great potential in the green chemical processes.
- Prabhavathi Devi,Gangadhar,Siva Kumar,Shiva Shanker,Prasad,Sai Prasad
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experimental part
p. 96 - 100
(2011/10/05)
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- Highly efficient tetrahydropyranylation of alcohols and phenols catalyzed by a new and reusable high-valent vanadium(IV) porphyrin
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In the present work, the catalytic activity of high-valent tetraphenylporphyrinatovanadium(IV) trifluoromethanesulfonate, [V IV(TPP)(OTf)2], in the tetrahydropyranylation of alcohols and phenols with 3,4-dihydro-2H-pyran (DHP) is reported. This new electron-deficient V(IV) compound was used as a highly efficient catalyst for pyranylation of primary (aliphatic and benzylic), sterically-hindered secondary and tertiary alcohols with DHP. Tetrahydropyranylation of phenols with DHP was also performed to afford the desired THP-ethers. The chemoselectivity of this method was also investigated. The results indicated that primary alcohols are more reactive in the presence of secondary and tertiary alcohols and phenols. This catalyst was reused several times without loss of its activity.
- Abdolmanaf Taghavi,Moghadam, Majid,Mohammadpoor-Baltork, Iraj,Tangestaninejad, Shahram,Mirkhani, Valiollah,Khosropour, Ahmad Reza
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experimental part
p. 1095 - 1102
(2012/03/11)
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- High-valent tin(IV) porphyrin: An efficient and reusable catalyst for tetrahydropyranylation of alcohols and phenols under mild conditions
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In this paper, rapid and highly efficient tetrahydropyranylation of alcohols and phenols with 3,4-dihydro-2H-pyran (DHP) in the presence of catalytic amounts of high-valent tin (IV) tetraphenylporphyrinato trifluoromethanesufonate, [SnIV(TPP)(OTf)2] is reported. In this catalytic system, primary, secondary and tertiary alcohols as well as phenols were converted to their corresponding tetrahydropyranyl ethers (THP-ethers) in excellent yields and short reaction times at room temperature. It is noteworthy that this method can be used for chemoselective tetrahydropyranylation of primary alcohols in the presence of secondary and tertiary alcohols and phenols. The catalyst was reused several times in the protection reactions without loss of its catalytic activity.
- Moghadam, Majid,Tangestaninejad, Shahram,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj,Gharaati, Shadab
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experimental part
p. 1523 - 1528
(2010/08/04)
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- Carbon tetrabromide/sodium triphenylphosphine-m-sulfonate (TPPMS) as an efficient and easily recoverable catalyst for acetalization and tetrahydropyranylation reactions
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A solid complex, conveniently prepared from carbon tetrabromide and sodium triphenylphos-phine-m-sulfonate (TPPMS), can be used as an easily recoverable catalyst for the selective acetalization of aldehydes and tetrahydropyranylation of alcohols. The catalyst can be recovered by simple pre-cipitation with ether and can be reused at least 7 times without loss of catalytic activity.
- Huo, Congde,Chan, Tak Hang
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experimental part
p. 1933 - 1938
(2011/02/28)
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- Generally applicable organocatalytic tetrahydropyranylation of hydroxy functionalities with very low catalyst loading
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This paper presents the first acid-free, organocatalytic tetrahydropyran and 2-methoxypropene protection of alcohols, phenols, and other ROH derivatives utilizing privileged N,N′-bis[3,5-bis(trifluoromethyl)phenyl]thiourea and a polystyrene-bound analogue. The reactions are broadly applicably (also on preparative scale), in particular, to acid-sensitive substrates such as aldol products, hydroxy esters, acetals, silyl-protected alcohols, and cyanohydrins. The catalytic efficiency is truly remarkably with turnover numbers of 100,000 and turnover frequencies of up to 5700 h-1 at catalyst loadings down to 0.001 mol%. The computationally supported mechanistic interpretation emphasizes the hydrogen bond assisted heterolysis of the alcohol and concomitant preferential stabilization of the oxyanion hole in the transition state. Georg Thieme Verlag Stuttgart.
- Kotke, Mike,Schreiner, Peter R.
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p. 779 - 790
(2008/01/03)
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- N-Bromosuccinimide (NBS): A mild and efficient catalyst for tetrahydropyranylation of alcohols and phenols under solvent-free conditions
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Different types of alcohols and phenols are tetrahydropyranylated in the presence of NBS catalyst in good to excellent yields under mild, neutral and solvent-free conditions.
- Khazaei, Ardeshir,Rostami, Amin,Raiatzadeh, Ayeh
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p. 1029 - 1032
(2008/03/11)
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- Tetrahydropyranylation of alcohols and phenols using the synergistic catalyst system, copper(II) chloride-acetic acid
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Copper(II) chloride-acetic acid was found to be an efficient synergistic catalytic system for the tetraphydropyranylation of various alcohols and phenols in high yields at room temperature in short reaction times. Springer-Verlag 2007.
- Wang, Min,Song, Zhi-Guo,Jiang, Heng,Gong, Hong
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p. 599 - 602
(2008/02/03)
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- Silica-gel-supported aluminium chloride: A stable, efficient, selective, and reusable catalyst for tetrahydropyranylation of alcohols and phenols
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A simple, effective, and highly chemoselective method to form 2-tetrahydropyranyl ethers of alcohols and phenols in the presence of silica-gel-supported aluminium chloride as a heterogeneous Lewis acid catalyst is described. The catalyst can be easily recovered and reused without appreciable change in its efficiency. Copyright Taylor & Francis Group, LLC.
- Borujeni, Kaveh Parvanak
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p. 2705 - 2710
(2007/10/03)
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- Selective tetrahydropyranylation under non-acidic conditions
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We report that the tetrahydropyranylation of hydroxyl groups, exhibiting especially very low nucleophilicities, can be achieved by means of Mitsunobu reaction with 2-hydroxytetrahydropyran. This reaction led to the protection of phenols and pyridinols without the use of an acidic catalyst. For instance hydroxypyridines could not be protected by dihydropyran under acidic conditions, whereas they underwent a smooth tetrahydropyranylation under Mitsunobu conditions. The method is selective for a phenol over an alcohol. Georg Thieme Verlag Stuttgart.
- Azzouz, Rabah,Bischoff, Laurent,Fouquet, Marc-Henri,Marsais, Francis
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p. 2808 - 2810
(2007/10/03)
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- A mild and efficient method for tetrahydropyranylation and detetrahydropyranylation of alcohols and phenols by BiOClO4.xH 2O (or) BiONO3
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A mild and efficient method for the protection of alcohols and phenols as tetrahydropyranyl ethers 3a-k and their deprotection at room temperature using BiOClO4.xH2O (or) BiONO3 as catalyst is described.
- Thirupathi Reddy,Narsimha Reddy,Sunil Kumar,Srinivasulu,Rajitha
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p. 2396 - 2398
(2007/10/03)
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- A mild and efficient tetrahydropyranylation and detetrahydropyranylation of alcohols and phenols by VCl3
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Vanadium chloride is found to be an efficient catalyst for the tetrahydropyranylation and detetrahydropyranylation of various alcohols and phenols, giving good yields at room temperature and short reaction times. 2005 Springer Science+Business Media, Inc.
- Narsimha Reddy,Sunil Kumar,Kumar,Srinivasulu,Thirupathi Reddy,Rajitha
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p. 1371 - 1373
(2007/10/03)
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- Ti(III) chloride: A novel reagent for the chemoselective deprotection of tetrahydropyranyl ethers
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Ti(III) chloride was found to be an effective catalyst for the deprotection of tetrahydropyranyl ethers of alcohols and phenols at an ambient temperature. Allyl ether, benzyl ether, tert-butyl-diphenylsilyl (TBDPS) ether, p-toluenesulfonate ester and isomerizable double bond were found to be compatible under the reaction conditions.
- Semwal, Abha,Nayak, Sandip K.
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- Microwave-assisted preparation of imidazolium-based tetrachloroindate(III) and their application in the tetrahydropyranylation of alcohols
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Microwave-assisted preparation of 1-alkyl-3-methylimidazolium tetrachloroindate(III), [Rmim][InCl4] (R = methyl, ethyl, butyl, hexyl, octyl) and their application as recyclable catalysts for the efficient and eco-friendly protection of alcohols to form tetrahydropyranyl (THP) ethers are described.
- Kim, Yong Jin,Varma, Rajender S.
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p. 1467 - 1469
(2007/10/03)
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- Bismuth triflate: An efficient catalyst for the formation and deprotection of tetrahydropyranyl ethers
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The tetrahydropyranylation of alcohols under solvent-free conditions is efficiently catalyzed by bismuth triflate (0.1 mol %). The experimental procedure is simple and works well with a variety of alcohols and phenols. The catalyst is insensitive to air and small amounts of moisture, easy to handle and relatively nontoxic. The deprotection of THP ethers is also catalyzed by bismuth triflate (1.0 mol %). ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).
- Stephens, Jacqueline R.,Butler, Phillip L.,Clow, Curtis H.,Oswald, Matthew C.,Smith, Russell C.,Mohan, Ram S.
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p. 3827 - 3831
(2007/10/03)
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- Lithium triflate (LiOTf) catalyzed efficient and chemoselective tetrahydropyranylation of alcohols and phenols under mild and neutral reaction conditions
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Different types of alcohols and phenols were effectively converted to the corresponding THP ethers in the presence of DHP and a catalytic amount of lithium trifluoromethanesulfonate (LiOTf) in refluxing 1,2-dichloroethane under essentially neutral reaction conditions. The method also shows good chemoselectivity for mono-tetrahydropyranylation of symmetrical diols.
- Karimi, Babak,Maleki, Jafar
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p. 5353 - 5355
(2007/10/03)
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- Protection of alcohols and phenols with dihydropyran and detetrahydropyranylation by ZrCl4
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Alcohols and Phenols are protected efficiently with dihydropyran(DHP) in the presence of catalytic amounts of zirconium tetrachloridein dichloromethane. Deprotection of THP-ethers is also afforded in a methanolic solution at room temperature.
- Rezai, Nasrin,Meybodi, Farhat Alsadat,Salehi, Peyman
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p. 1799 - 1805
(2007/10/03)
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- Spanish sepiolite clay as a new heterogeneous catalyst for the tetrahydropyranylation of alcohols and phenols
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OH-protection of alcohols and phenols by heating the hydroxylated compound with 3,4-dihydro-2H-pyrane in the presence of a readily available and inexpensive spanish sepiolite heterogeneous acid clay catalyst is described. Isolated yields, not optimized, were in the range 29-99%.
- Campelo,Garcia,Lafont,Luna,Marinas
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p. 1345 - 1350
(2007/10/02)
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- Molybdenum catalyzed protective tetrahydropyranylation of alcohols and phenols
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Molybdenyl(VI) acetylacetonate is an effective catalyst for the protective tetrahydropyranylation of alcohols and phenols.
- Lakshmi Kantam,Lakshmi Santhi
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p. 2225 - 2228
(2007/10/02)
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- Lanthanum trichloride catalysed protective tetrahydropyranylation of alcohols and phenols
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Lanthanum Trichloride is an effective catalyst for the protective tetrahydropyranylation of alcohols and phenols. The catalyst is recycled almost quantitatively.
- Bhuma,Kantam
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p. 2941 - 2944
(2007/10/02)
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- AlPO4 and AlPO4-Al2O3 as new heterogeneous catalysts for the solvent-free tetrahydropyranylation of alcohols and phenols
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OH-protection of alcohols and phenols by heating the hydroxylated compound with 3,4-dihydro-2H-pyrane in the presence of an AlPO4 or AlPO4-Al2O3 heterogeneous acid catalyst is described. Isolated yields, not optimized, were in the range 50-99%.
- Campelo,Garcia,Lafont,Luna,Marinas
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p. 2335 - 2342
(2007/10/02)
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- The conformational behaviour of 2-aryloxytetrahydropyrans and 2-acetoxytetrahydropyran, and barrier to ring inversion
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The 13C nuclear magnetic resonance data of a series of 2-(4-substituted-phenoxy)tetrahydropyrans at 156 K and in CF2Br2 and CHFCl2 solvents show that the axial preference increases with electron withdrawal in the aryloxy group: from 79 percent (ΔG0E->A = -0.4 kcal mol-1) (4-OCH3) to 90 percent (ΔG0E->A = -0.7 kcal mol-1) (4-NO2) in CF2Br2.The axial preference (anomeric effect) is smaller in the more polar CHFCl2 solvent, as expected, and the substituent effect is smaller also: change in ΔG0E->A from -0.3 (4-OCH3) to -0.5 (4-NO2) kcal mol-1.However, the axial preference of 2-acetoxytetrahydropyran is shown to be smaller than that of 2-phenoxytetrahydropyran in CF2Br2 solvent although the acetoxy group is expexted to be more electronegative than the phenoxy group.Furthermore, the polarity of the solvent has no effect on the conformational equilibrium of 2-acetoxytetrahydropyran.The results are interpreted in terms of both orbital and electrostatic interactions.The ring-inversion barrier of 2-alkoxy and 2-aryloxytetrahydropyrans, determined by the temperature-coalescence method, is lower than that of tetrahydropyran by about 1.5 kcal mol-1.
- Quedraogo, Adama,Lessard, Jean
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p. 474 - 480
(2007/10/02)
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- The Thermal ortho-Substitution of Phenols by Vinyl Ethers
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Pyrolysis of a mixture of phenol and 3,4-dihydro-2H-pyran (6) at 150-180 deg C resulted in the formation of 2-(tetrahydro-2H-pyran-2-yl)phenol (3a) in moderate yield.This selective ortho-substitution reaction has been investigated for a range of phenols and a number of vinyl ethers.While it was found to be a fairly general reaction for phenols, only with the vinyl ether (6) and 2,3-dihydrofuran (28a) was the reaction found to be regioselective.Aluminium phenylate strongly catalyses the reaction of phenol with (6), which proceeded under these conditions at room temperature.An ene-type mechanism is proposed for the reaction.
- Pinhey, John T.,Xuan, Phan Thanh
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- MIXED AROMATIC-ALIPHATIC ACETALS; THEIR PREPARATION, (1)H AND (13)C-NMR SPECTRA AND HYDROGENOLYSIS BY ETHEREAL SOLUTION OF CHLOROALANE
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The corresponding p-X-phenylisobutyl acetals of acetaldehyde (I), 2-(p-X-phenoxy)tetrahydropyrans (II), 2-(p-X-phenoxy)tetrahydrofurans (III), and cyclohexyl(p-X-phenyl)acetals of acetaldehyde (IV) were prepared by addition of p-X-substituted phenols to isobutyl vinyl ether, 2,3-dihydro-4H-pyran, 2,3-dihydrofuran, and cyclohexyl vinyl ether, respectively.The structures of acetals I-IV were confirmed by their (1)H and (13)C-NMR spectra.Diastereotopic protons of the methylene and geminal methyl groups are anisochronous in the (1)H-NMR spectra of acetals I. (13)C-NMR spectra of acetals IV demonstrate anisochronous behaviour of cyclohexane ring diastereotopic carbon atoms.The constants ?p+ for several groups calculated using (13)C-NMR spectra are: 1-isobutoxy-1-ethoxy- (-0.58), 2-tetrahydrofuryloxy- (-0.59), and 1-cyclohexyloxy-(1-ethoxy) (-0.57).Experimental relative rate constants of hydrogenolysis of acetals I and II by ethereal solution of chloroalane yield best correlations with ?p+ constants of the substituent X, providing the values ρ= -1.09 for compounds of the series I and II, respectively.The importance of these results for finding the rate determining step of the studied reaction is discussed.
- Dusek, Jiri,Sklenar, Vladimir,Jonas, Jaroslav
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p. 2912 - 2923
(2007/10/02)
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