- Cyclopropenium Enhanced Thiourea Catalysis
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An integral part of modern organocatalysis is the development and application of thiourea catalysts. Here, as part of our program aimed at developing cyclopropenium catalysts, the synthesis of a thiourea-cyclopropenium organocatalyst with both cationic hydrogen-bond donor and electrostatic character is reported. The utility of the this thiourea organocatalyst is showcased in pyranylation reactions employing phenols, primary, secondary, and tertiary alcohols under operationally simple and mild reaction conditions for a broad substrate scope. The addition of benzoic acid as a co-catalyst facilitating cooperative Br?nsted acid catalysis was found to be valuable for reactions involving phenols and higher substituted alcohols. Mechanistic investigations, including kinetic and 1H NMR binding studies in conjunction with density function theory calculations, are described that collectively support a Br?nsted acid mode of catalysis.
- Smajlagic, Ivor,Durán, Rocio,Pilkington, Melanie,Dudding, Travis
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supporting information
p. 13973 - 13980
(2018/11/21)
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- BiCl3: A versatile catalyst for the tetrahydropyranylation and depyranylation of 1°,2°,3°, allylic, benzylic alcohols, and symmetric diols
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Bismuth trichloride as mild reagent, has been found to be a worthful catalyst for tetrahydropyranylation of 1°,2°,3°, allylic, benzylic alcohols, and symmetric di-ols. At room temperature the reagent THP(3,4-dihydro-2H-pyran) was successfully employed as pyranylating agent in presence of BiCl3catalyst without the use of a solvent and the yields of the products were found to be 90-96%. Further, the depyranylation of alcohols was achieved in quantitative yield by simple addition of MeOH using the same catalyst. The developed method was showed good chemo-selectivity in symmetrical diols for mono THP protection.
- Vijaya Durga,Balamurali Krishna,Baby Ramana,Santha Kumari,Vijay,Hari Babu
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p. 1030 - 1034
(2017/05/26)
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- Facile O-glycosylation of glycals using Glu-Fe3O4-SO3H, a magnetic solid acid catalyst
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A new glucose derived magnetic solid acid catalyst (Glu-Fe3O4-SO3H) was synthesized in a convenient and ecofriendly manner and well characterized using FTIR, PXRD, EDAX, SEM, and XPS which showed the presence of Fe3/
- Thombal, Raju S.,Jadhav, Vrushali H.
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p. 30846 - 30851
(2016/04/09)
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- Organocatalyzed direct glycosylation of unprotected and unactivated carbohydrates
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Organocatalyzed direct glycosylation of unprotected and unactivated carbohydrates is reported. This process is catalyzed by triphenylphosphine and tetrabromomethane at room temperature under neutral conditions. With this operationally simple protocol thermodynamically favored, glycosides were obtained in a very straightforward reaction.
- Schmalisch, Sebastian,Mahrwald, Rainer
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supporting information
p. 5854 - 5857
(2013/12/04)
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- Direct glycosylation of unprotected and unactivated carbohydrates under mild conditions
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Ligand exchange acetalization of acetals in the presence of catalytic amounts of mandelic acid and titanium tert-butoxide is reported. This transformation is successfully extended to glycosylation of unprotected and unactivated pentoses. Even unreactive pentoses such as d-arabinose or d-lyxose can be transformed by this new methodology into corresponding isopropyl glycosides.
- Pfaffe, Matthias,Mahrwald, Rainer
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supporting information; experimental part
p. 792 - 795
(2012/05/04)
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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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- Mild and efficient chemoselective tetrahydropyranylation of alcohols using bronsted acidic ionic liquid as catalyst under solvent-free conditions
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A straightforward and efficient method for preparation of morpholinium bisulfate ([mroH]HSO4) as a novel acidic ionic liquid is reported. The application of this efficient and inexpensive acidic ionic liquid catalyst for tetrahydropyranylation of alcohols under mild and solvent-free conditions at room was investigated.
- Hajipour, Abdol R.,Nasresfahani, Zahra
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experimental part
p. 1995 - 2006
(2012/06/04)
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- Solvent-free tetrahydropyranylation of alcohols catalyzed by amine methanesulfonates
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A comparative study of tetrahydropyranylation of alcohols under various solvents or solvent-free conditions using different amine methanesulfonates as catalysts shows that tetrahydropyranyl ethers of alcohols are obtained under solvent-free conditions in good yields using catalytic amounts of triethylenediamine methanesulfonate, 1,6-hexanediamine methanesulfonate, diethylenetriamine methanesulfonate and pyridine methanesulfonate, respectively. The reaction occurs readily in short times at room temperature catalyzed by these catalysts, especially triethylenediamine methanesulfonate. Some of the major advantages of this procedure are that the catalysts are environmentally friendly, highly effective, and easy to prepare and handle. The reaction is also clean and needs no solvent, and the work-up is very simple.
- Wang, Rui,Sun, Mingzhu,Jiang, Heng
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experimental part
p. 61 - 67
(2012/02/16)
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- 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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experimental part
p. 1349 - 1352
(2011/01/11)
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- Poly(N-bromo-N-ethyl-benzene-1,3-disulfonamide), N,N,N′,N′- tetrabromobenzene-1, 3-disulfonamide as new efficient reagents for conversion of alcohols to THP ethers and aldehydes to oxazoline compounds
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This paper is concerned with an easy preparation of THP ethers from primary, secondary and tertiary alcohols and oxazoline compounds from various aldehydes using poly(N-bromo-N-ethyl-benzene-1,3-disulfonamide), N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide [TBBDA] as new and efficient reagents under ambient conditions without over-oxidation.
- Ghorbani-Vaghei,Akbari-Dadamahaleh,Amiri
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experimental part
p. 301 - 307
(2010/09/03)
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- 1,6-Hexanediamine methanesulfonate: A mild and efficient catalyst for the tetrahydropyranylation of alcohols under solvent-free conditions
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Various alcohols react with 3,4-dihydro-2 H-pyran under mild conditions using a catalytic amount of 1,6-hexanediamine methanesulfonate. It affords the corresponding tetrahydropyranyl ethers in good yields at a faster rate in the absence of solvent. Taylor & Francis Group, LLC.
- Wang, Rui,Jiang, Heng
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experimental part
p. 171 - 176
(2012/01/05)
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- 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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experimental part
p. 177 - 179
(2010/04/02)
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- Tetrahydropyranylation of alcohols under solvent-free conditions
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A green, efficient, and large-scale method for tetrahydropyranylation of alcohols in the presence of a catalytic amount of pyridinium chloride at room temperature under solvent-free conditions is reported. Copyright Taylor & Francis Group, LLC.
- Hajipour, Abdol R.,Kargosha, Majid,Ruoho, Arnold E.
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experimental part
p. 1084 - 1091
(2009/09/08)
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- 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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experimental part
p. 601 - 604
(2009/08/07)
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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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- 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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- Efficient role of ionic liquid (bmim)HSO4 as novel catalyst for monotetrahydropyranylation of diols and tetrahydropyranylation of alcohols
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A simple procedure for the monotetrahydropyranylation of diols and alcohols, in excellent to moderate yields, has been reported using a catalytic amount of the acidic ionic liquid, 1-butyl-3-methylimidazolium hydrogensulphate (bmim)HSO4 under microwave and ultrasonic irradiation. Results have been compared with those obtained by reactions in the absence of these energies, and effectiveness of the recycled ionic liquid has also been studied. Copyright Taylor & Francis Group, LLC.
- Singh, Jasvinder,Gupta, Neeraj,Kad, Goverdhan L.,Kaur, Jasamrit
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p. 2893 - 2900
(2007/10/03)
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- Ruthenium(III) acetylacetonate [Ru(acac)3] - An efficient chemoselective catalyst for the tetrahydropyranylation (THP) of alcohols and phenols under solvent-free conditions
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A catalytic amount of ruthenium(III) acetylacetonate (2 mol%) [Ru(acac)3] enables solvent-free tetrahydropyranylation of different types of alcohols and phenols at ambient temperature in moderate to excellent yields. Notably, selective monoprotection of diols can be achieved chemoselectively. Furthermore, the catalyst could be recovered and reused if necessary.
- Varala, Ravi,Adapa, Srinivas R.
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p. 1174 - 1179
(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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- Simple and facile tetrahydropyranylation of alcohols by use of catalytic amounts of benzyltriphenylphosphonium tribromide
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An efficient and mild system for protection of a variety of alcohols with 3,4-dihydro-2H-pyran (DHP) in the presence of catalytic amounts of benzyltriphenyl-phosphonium tribromide (BTPTB) (1) gives the corresponding tetrahydropyan ethers (ROTHP) in dichloromethane. The experimental procedure is simple, and the products are straightforwardly isolated in high to excellent yields. Copyright Taylor & Francis, Inc.
- Hajipour,Pourmousavi,Ruoho
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p. 2889 - 2894
(2007/10/03)
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- Bronsted acidic ionic liquids: Fast, mild, and efficient catalysts for solvent-free tetrahydropyranylation of alcohols
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Bronsted acidic ionic liquids as efficient and reusable catalysts for the protection of alcohols as tetrahydropyranyl (THP) ethers under solvent-free conditions at room temperature was investigated. Good to excellent yields were obtained at a faster rate over [BMIm][HSO4] or [BMIm][H2PO4]. Copyright Taylor & Francis, Inc.
- Duan, Zhiying,Gu, Yanlong,Deng, Youquan
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p. 1939 - 1945
(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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- Chemoselective tetrahydropyranylation of alcohols and phenols using polystyrene supported aluminium chloride as a catalyst
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A simple, efficient and highly chemoselective method for tetrahydropyranylation of alcohols and phenols has been developed by their reaction with 3,4-dihydro-2H-pyran at room temperature in the presence of a catalytic amount of polystyrene supported AlCl3. The method is also highly selective for monoprotection of symmetrical diols.
- Tamami, Bahman,Parvanak Borujeny, Kaveh
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p. 715 - 718
(2007/10/03)
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- Zeolite-catalyzed environmentally friendly tetrahydropyranylation of alcohols and phenols
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A simple and environmentally friendly tetrahydropyranylation of various alcohols and phenols at room temperature was elaborated by using a small pore size zeolite. The material is also suitable for the deprotection but with less efficiency.
- Hegedues, Adrienn,Vigh, Ilona,Hell, Zoltan
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p. 4145 - 4152
(2007/10/03)
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- Solvent-Free Tetrahydropyranylation of Alcohols with Sulfamic Acid as Reusable Catalyst
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An efficient H2NSO3H-catalyzed solvent-free tetrahydropyranylation of various alcohols at room temperature was investigated. The features of mild conditions, cost-efficient catalyst, simple work-up, and the recyclability of the catalyst were displayed in this article.
- Wang, Bo,Yang, Li-Ming,Suo, Ji-Shuan
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p. 3929 - 3934
(2007/10/03)
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- Envirocat EPZG as a new heterogenous catalyst for the solvent-free tetrahydropyranylation of alcohols and phenols
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Envirocat EPZG was used as a solid supported acid catalyst for tetrahydropyranylation of alcohols and phenols in the absence of a solvent. This new method is rapid, efficient and convenient giving the corresponding products in high yields and purity.
- Bandgar,Jagtap,Aghade,Wadgaonkar
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p. 2211 - 2215
(2007/10/02)
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- 2-Alkoxy-3-oxoalkyl-tetrahydropyrans and -tetrahydrofurans: versatile intermediates in heterocyclic synthesis
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A new Lewis acid-catalysed Michael-type addition of heterocyclic enol ethers to hemiacetal vinylogues 1 or to enones in the presence of a hydroxylic compounds is described.The 1,5-keto acetal 3 so obtained have been studied with a view to synthetic applications.Acidic hydrolysis of compound 3 leads in most cases to annulation products 9 in a stereocontrolled manner.Organometallic addition, hydride reduction or reductive amination of 1,5-keto acetals 3 afford, in good yields, the hydroxy acetals 12 (and cyclisation products 13) and amino acetals 18, respectively.Acidic treatment of these compounds gave access to oxa- and aza-annulation products 13, 17 and 19 by an efficient kinetically controlled heterocyclisation process.These products can be obtained with high cis-junction selectivities as established by NMR spectroscopy and confirmed by equilibration studies.
- Duhamel, Pierre,Deyine, Abdallah,Dujardin, Gilles,Ple, Gerard,Poirier, Jean-Merie
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p. 2103 - 2114
(2007/10/02)
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- A versatile ruthenium catalyst for the tetrahydropyranylation of alcohols and phenols
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The tetrahydropyranyl derivatives of alcohols and phenols are efficiently prepared in the presence of catalytic amounts of [Ru(CH3CN)3(triphos)](OTf)2 (triphos = CH3C(CH2PPh2)3) under mild conditions, in good to excellent yields.
- Ma,Venanzi
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p. 5269 - 5272
(2007/10/02)
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- Catalysis by Acidic Clay of the Protective Tetrahydropyranylation of Alcohols and Phenols
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The K-10 montmorillonite, a readily available and inexpensive industrial catalyst, cleanly effects the title reaction.
- Hoyer, Susanne,Laszlo, Pierre,Orlovic, Mirko,Polla, Eugenio
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p. 656 - 657
(2007/10/02)
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- Photochemistry of 3-Oxacycloalkenes
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Direct and sensitized photolyses of 3-oxacycloalkenes 1a-c has been studied in n-pentane and in alkohols.In contrast to the photochemistry of cycloalkenes, the direct photolyses of 1a and 1b in pentane gave the products 2, 3, and 4, 5, respectively, which are derived from an allylic O-C bond cleavage.In addition, in the case of 1b, a small amount of the carbene-derived product 6 was also obtained.The seven-membered oxacycloalkene 1c gave no volatile product upon direct irradiation in pentane.Upon direct or sensitized photolyses in methanol, oxacycloalkenes 1b or 1cgave the adducts 7b,c as major products.Irrespective of the method of excitation, the yield of the adduct in the photolyses in a series of alcohols decreased with decreasing pK(a) value of the alcohol which can be explained in terms of the formation and subsequent trapping of the intermediate trans isomer 14 by the alcohol.These results can be rationalized in terms of the reactivities of the ?,?* and ?,?* states and the increased stability of the Rydberg state.
- Inoue, Yoshihisa,Matsumoto, Naofumi,Hakushi, Tadao,Srinivasan, R.
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p. 2267 - 2272
(2007/10/02)
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