- Vanadium-Catalyzed Oxidative Debenzylation of O-Benzyl Ethers at ppm Level
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An advantageous methodology for the oxidative debenzylation of ethers has been developed. Very low amounts of a catalyst system based on vanadyl acetylacetonate and a triazole type pincer ligand allow the selective oxidative cleavage of a number of O-benzyl ethers in the presence of oxygen as the sole oxidant. The methodology tolerates a number of functional groups such as halo-, alkoxy-, or trifluoromethylarenes, alkyne, alkene, ether, and acetal units. Large-scale deprotections can be also carried out by the optimized procedure, which is amenable to enantioenriched reactants as well. (Figure presented.).
- Urgoitia, Garazi,SanMartin, Raul,Herrero, María Teresa,Domínguez, Esther
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p. 3307 - 3312
(2016/10/21)
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- Syntheses and biological evaluation of 1,2,3-triazole and 1,3,4-oxadiazole derivatives of imatinib
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Three novel series of 1,2,3-triazole and 1,3,4-oxadiazole derivatives of imatinib were prepared and evaluated in vitro for their cytostatic effects against a human chronic myeloid leukemia (K562), acute myeloid leukemia (HL60), and human leukemia stem-like cell line (KG1a). The structure-activity relationship was analyzed by determining the inhibitory rate of each imatinib analog. Benzene and piperazine rings were necessary groups in these compounds for maintaining inhibitory activities against the K562 and HL60 cell lines. Introducing a trifluoromethyl group significantly enhanced the potency of the compounds against these two cell lines. Surprisingly, some compounds showed significant inhibitory activities against KG1a cells without inhibiting common leukemia cell lines (K562 and HL60). These findings suggest that these compounds are able to inhibit leukemia stem-like cells.
- Li, Yong-Tao,Wang, Jing-Han,Pan, Cheng-Wen,Meng, Fan-Fei,Chu, Xiao-Qian,Ding, Ya-Hui,Qu, Wen-Zheng,Li, Hui-Ying,Yang, Cheng,Zhang, Quan,Bai, Cui-Gai,Chen, Yue
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p. 1419 - 1427
(2016/02/19)
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- Zinc triflate: A mild and efficient catalyst for deprotection of tetrahydropyranyl ethers
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Treatment of tetrahydropyranyl (THP) ethers with zinc triflate in methanol provides a simple and efficient process for deprotection of these ethers and the parent alcohols are obtained in excellent yields.
- Srinivasulu,Satyanarayana,Ravi Kumar
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p. 2419 - 2422
(2014/03/21)
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- Simple and efficient method for deprotection of tetrahydropyranyl ethers by using Silica supported sodium hydrogen sulphate
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Tetrahydropyranyl (THP) ethers have been efficiently and simply deprotected by using Silica supported sodium hydrogen sulphate (NaHSO4-SiO 2) in methanol at room temperature to regenerate the parent alcohols in high yields. Tetrahydropyranyl (THP) ethers have been efficiently and simply deprotected by using silica supported sodium hydrogen sulphate (NaHSO 4-SiO2) in methanol at room temperature to regenerate the parent alcohols in high yields.
- Kumar, K. Ravi,Satyanarayana,Reddy, B. Srinivasa
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experimental part
p. 1189 - 1191
(2012/07/27)
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- Preference of β-lactam formation in Cu(I)-catalyzed intramolecular coupling of amides with vinyl bromides
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(Chemical Equation Presented) A general and highly efficient synthesis of 4-alkylidene-2-azetidinones was achieved by the Cu(I)-catalyzed intramolecular C-N coupling of amides with vinyl bromides. This 4-exo ring closure was found to be fundamentally preferred over other modes (5-exo, 6-exo, and 6-endo) of cyclization under copper catalysis. Tandem C-N bond formation was then successfully developed to allow the convenient generation of medium-sized lactams.
- Zhao, Qiwu,Li, Chaozhong
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supporting information; experimental part
p. 4037 - 4040
(2009/05/27)
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- Chemoselective TBS deprotection of primary alcohols by means of pyridinium tribromide (Py·Br3) in MeOH
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A catalytic amount of pyridinium tribromide (Py·Br3) in MeOH chemoselectively deprotects primary TBS ethers in the presence of a variety of other protecting and common functional groups in modest to excellent yields when performed at 0 °C.
- Martinez-Solorio, Dionicio,Jennings, Michael P.
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p. 5175 - 5178
(2008/12/20)
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- A simple, efficient and highly selective deprotection of t-butyldimethylsilyl (TBDMS) ethers using silica supported sodium hydrogen sulfate as a heterogeneous catalyst
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t-Butyldimethylsilyl (TBDMS) ethers have been efficiently and selectively deprotected using silica supported sodium hydrogen sulfate (NaHSO4·SiO2) as a heterogeneous catalyst at room temperature to regenerate the parent alcohols in high yields.
- Das, Biswanath,Reddy, K. Ravinder,Thirupathi
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p. 5855 - 5857
(2007/10/03)
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- Picolinyl group as an efficient alcohol protecting group: Cleavage with Zn(OAc)2·2H2O under a neutral condition
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As an efficient alcohol protecting group, picolinates (Pic), prepared from the corresponding alcohols using commercial picolinoyl chloride, are readily cleaved by Zn(OAc)2 or Cu(OAc)2, even in the presence of other common alcohol protecting groups. Moreover, the picolinyl group at C-2 position in carbohydrates can be selectively cleaved to give methyl 4,6-O-benzylidene-3-O-picolinyl-α-d-glucopyranoside and 3-O-picolinyl methyl-4,6-O-benzylidene-α-d-galactopyranoside in good yields.
- Ju, Yuel Baek,Shin, Yong-Joo,Heung, Bae Jeon,Kwan, Soo Kim
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p. 5143 - 5147
(2007/10/03)
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- Study of the regioselectivity in the hydrotelluration of hydroxy alkynes
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Vinylic tellurides were synthesized by the addition of organotellurols to acetylenic alcohols and the regioselectivity of the reaction was evaluated.
- Stefani, Hélio A.,Cardoso, Lincoln D. G.,Valduga, Claudéte J.,Zeni, Gilson
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p. 167 - 172
(2007/10/03)
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- A facile and chemoselective cleavage of trityl ethers by indium tribromide
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Trityl ethers are chemoselectively, deprotected to the corresponding alcohols in high yields by a catalytic amount of indium tribromide in aqueous acetonitrile. The method is compatible with various functional groups such as acetonides, acetates, benzoates, olefins, carbamates, esters and ethers present in the substrate.
- Yadav,Reddy, B.V. Subba,Srinivas,Maiti
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p. 528 - 529
(2007/10/03)
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- A highly efficient, mild, and selective cleavage of beta-methoxyethoxymethyl (MEM) ethers by cerium(III) chloride in acetonitrile.
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[structure: see text]. A highly selective cleavage of MEM ethers has been achieved in high yields using CeCl3.7H2O in refluxing acetonitrile under mild and neutral reaction conditions. The method is very rapid and compatible with other hydroxyl protecting groups such as Bn, TBDPS, Ac, Me, Tr, PMB, benzylidene, THP, MOM, BOM, and NHAc present in the substrate.
- Sabitha,Babu,Rajkumar,Srividya,Yadav
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p. 1149 - 1151
(2007/10/03)
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- Synthesis of substituted α-methylene-γ-butyrolactones from chloroformates via palladium catalysed cyclisation-anion capture
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Cyclisation of chloroformates onto proximate alkyne functionality in the presence of a Pd(0) catalyst followed by anion capture affords α-methylene-γ-butyrolactone derivatives in moderate to good yields.
- Grigg,Savic
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p. 2381 - 2382
(2007/10/03)
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- A mild and selective cleavage of p-methoxybenzyl Ethers by CBr4-MeOH
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p-Methoxybenzyl ethers were selectively deprotected to the corresponding alcohols and phenols in high yields by CBr4 in refluxing methanol under neutral reaction conditions.
- Yadav,Reddy, B. V. Subba
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p. 566 - 567
(2007/10/03)
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- A convenient high-yield procedure for the β-hydroxyethylation of acetylenes with epoxyethane in liquid ammonia
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3-Butyn-1-ol and homologues, RC≡CCH2CH2OH (R = H or alkyl), have been obtained in excellent yields from alkynyllithium derivatives, RC≡CLi, and epoxyethane in liquid ammonia.
- Verkruijsse,Brandsma
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p. 235 - 237
(2007/10/02)
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- Elimination Instead of Rearrangement in Sulfur-Containing C12 Rings
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Syntheses of dithiacyclotetradecadiyne 13 and -diene 26 as well as thiacyclotridecatriene 36 are reported.Stevens rearrangement and elimination of sulfur from the methyl sulfonium salts 20 and 37 in order to obtain 1,4,7,10-cyclododecatetraene (1) or dienediyne 2 have not been successful; instead, only the ring-opened methyl thioethers 23 and 39 have been isolated.
- Brudermueller, Martin,Musso, Hans,Wagner, Alfred
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p. 2239 - 2244
(2007/10/02)
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- Palladium-Catalyzed Cyclizations of Bromo Dienes
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1-Bromo 1,5-dienes, 2-bromo 1,6-dienes, and 2-bromo 1,7-dienes have been found to undergo palladiumtriarylphosphine catalyzed cyclizations in the presence of piperidine to form five- or six-membered ring products in good yields.The major or only cyclic products formed are piperidino- or (piperidinomethyl)cyclopentenes and -cyclohexenes.The five-membered ring products are preferred over the six when there is a choice.
- Narula, C. K.,Mak, K. T.,Heck, R. F.
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p. 2792 - 2796
(2007/10/02)
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