- Selective acylation of a sterically hindered hydroxyl group of unsymmetrical diols containing a primary hydroxyl group such as 1,5-hexanediol in the presence of silica gel with acetyl chloride
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The selective acetylation of sterically hindered hydroxyl groups of 1,5-hexanediol preadsorbed on silica gel was reported. The relation between the adsorption of the diol on SiO2 and its reactivity for selective acetylation was studied. Results demonstrated that unsymmetrical diols get adsorbed on the surface of SiO2 preferentially via a primary OH group, leaving the non-adsorbed OH group available for reaction.
- Ogawa, Haruo,Ide, Yuko,Honda, Ryoichi,Chihara, Teiji
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- Preparation of the enantiomers of 1-phenylethan-1,2-diol. Regio- and enantioselectivity of acylase I and Candida antarctica lipases A and B
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Acylase I and Candida antarctica lipases A (CAL-A) and B (CAL-B) were evaluated for the preparation of the enantiomers of 1-phenylethan-1,2-diol. In the presence of CAL-B, the sequential one-pot methanolysis of the diacetate in acetonitrile allowed the preparation of (S)-diol (e.e. 97%) and (R)-1-acetoxy-1-phenylethanol (e.e. 94%). Base-catalyzed methanolysis of the monoacetate resulted in the corresponding (R)-diol. When one of the diol enantiomers was subjected to Mitsunobu esterification, inversion of configuration occurred, allowing transformation of the initially racemic mixture to one enantiomer. Acylase I-catalysis led to the chemo- and enantioselective formation of (S)-1-acetoxy-1-phenylethanol (e.e. 97%) in the presence of the primary hydroxyl function through acetylation of the secondary hydroxyl group. The low chemical yield (ca. 25%) was due to the moderate enzymatic regioselectivity. CAL-A behaved in a similar way to acylase I.
- Virsu, Pauliina,Liljeblad, Arto,Kanerva, Anu,Kanerva, Liisa T.
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- TiCl3(OTf) and TiO(TFA)2 efficient catalysts for ring opening of epoxides with alcohols, acetic acid and water
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TiCl3 (OTf) and TiO(TFA)2 can efficiently catalyze nucleophilic ring opening of epoxides in primary, secondary and tertiary alcohols, acetic acid and water to give the corresponding β-alkoxy alcohols, β-acetoxy alcohols and vicinal diols with high stereo- and regioselectivity in excellent yields. The reaction of optically active styrene oxide in MeOH with two titanium reagents was found to be highly stereospecific and afforded the corresponding S-(+)-2-methoxy-2-phenyl ethanol in 89-95% ee.
- Iranpoor, Nasser,Zeynizadeh, Behzad
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- Investigation of the catalytic activity of an electron-deficient vanadium(IV) tetraphenylporphyrin: A new, highly efficient and reusable catalyst for ring-opening of epoxides
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In this work, the catalytic activity of high-valent tetraphenylporphyrinatovanadium(IV) trifluoromethanesulfonate, [V IV(TPP)(OTf)2], in the nucleophilic ring-opening of epoxides is reported. This new V(IV) catalyst was used as an efficient catalyst for alcoholysis with primary (methanol, ethanol and n-propanol), secondary (iso-propanol) and tertiary alcohols (tert-butanol), hydrolysis and acetolysis of epoxides with acetic acid and also for the conversion of epoxides to 1,2-diacetates with acetic anhydride, conversion of epoxides to thiiranes with ammonium thiocyanate and thiourea, and for conversion of epoxides to acetonides with acetone. The catalyst was reused several times without loss of its activity.
- Taghavi, S. Abdolmanaf,Moghadam, Majid,Mohammadpoor-Baltork, Iraj,Tangestaninejad, Shahram,Mirkhani, Valiollah,Khosropour, Ahmad Reza,Ahmadi, Venus
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- Regioselective acetylation of carbohydrates and diols catalyzed by tetramethyl-ammonium hydroxide in water
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A novel method for an efficient regioselective acetylation of carbohydrates and diols in aqueous solution is described. Treatment of substrates with 1-acetylimidazole, and tetramethyl-ammonium hydroxide (TMAH) in water under mild conditions gave highly regioselective acetylation for primary hydroxyl groups. This discovery provides an eco-friendly way for selective acetylation of non-protected glycosides and diols in water, avoiding the use of toxic organic solvents and the necessity of pre-protection of secondary hydroxyl groups. This journal is
- Lu, Yuchao,Wei, Peng,Pei, Yuxin,Xu, Hengfu,Xin, Xiaoting,Pei, Zhichao
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- OXIDATION OF ISOXAZOLINES BY PERACIDS - A USEFUL ROUTE TO β-HYDROXY KETONES AND ACYLATED DIOLS
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A method for bringing about the ring cleavage of isoxazolines by the use of peracids is described.
- Park, Pyeong-uk,Kozikowski, Alan P.
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- A highly efficient protocol for regioselective ring-opening of epoxides with alcohols, water, acetic acid, and acetic anhydride catalyzed by SbF3
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SbF3as an efficient catalyst has been used for regioselective alcoholysis, acetolysis and hydrolysis of epoxides to the corresponding β-alkoxy, β-acetoxy alcohols, and 1,2-diols in high to excellent yields. This study also represents a convenient synthesis of vic-diacetates from ring-opening of epoxides with acetic anhydride.
- Zeynizadeh, Behzad,Gilanizadeh, Masumeh,Aminzadeh, Farkhondeh Mohammad
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- Synthesis and characterization of a novel Fe3O4@SiO2/bipyridinium dichloride nanocomposite and its application as a magnetic and recyclable phase-transfer catalyst in the preparation of β-azidoalcohols, β-cyanohydrins, and
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β-Azidoalcohols, β-cyanohydrins, and β-acetoxy alcohols have been synthesized in the presence of a Fe3O4@SiO2/bipyridinium nanocomposite (Fe3O4@SiO2/BNC) as a novel magnetic and recyclable
- Kiasat, Ali Reza,Chadorian, Fatemeh,Saghanezhad, Seyyed Jafar
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- Mild and efficient ring opening of epoxides catalyzed by potassium dodecatungstocobaltate(III)
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Efficient ring opening of epoxides under mild conditions is reported. Potassium dodecatungstocobaltate(III) trihydrate was used as an efficient catalyst for the alcoholysis and acetolysis of epoxides. Conversion of epoxides to thiiranes was also performed efficiently in the presence of this catalyst. Springer-Verlag 2005.
- Tangestaninejad, Shahram,Moghadam, Majid,Mirkhani, Valiollah,Yadollahi, Bahram,Mirmohammadi, S. Mohammad R.
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- Efficient and regioselective ring-opening of epoxides with carboxylic acid catalyzed by graphite oxide
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An efficient, simple and regioselective ring-opening reaction of epoxides with various carboxylic acids under metal-free conditions is reported. The ring-opening of epoxides takes place in the presence of graphite oxide as an efficient and available catalyst to produce the corresponding 2-hydroxy monoester and 1,2-diester derivatives in good yields. Regioselective attack of the nucleo-phile, short reaction times, metal-free conditions and reusability of catalyst are among the advantages of the present protocol.
- Mirza-Aghayan, Maryam,Tavana, Mahdieh Molaee,Niazi, Elaheh Golam Alipour,Boukherroub, Rabah
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p. 532 - 538
(2020/07/17)
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- A Phosphonium Ylide as an Ionic Nucleophilic Catalyst for Primary Hydroxyl Group Selective Acylation of Diols
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Carbonyl-stabilized phosphonium ylides exhibit great utility in modern organic synthesis, and they are known as an ambident nucleophile at the carbonyl oxygen atom and at the α-carbon atom. However, they have found limited use as catalysts. We focused on the inherent nucleophilicity of the oxygen atom to develop an ionic nucleophilic catalysis, and the phosphonium ylide-catalyzed primary alcohol selective acylation of mixed diols with acid anhydrides has been demonstrated. Mechanistic studies revealed the behavior of a catalyst, which would contribute to the field of ylide chemistry.
- Toda, Yasunori,Sakamoto, Tomoyuki,Komiyama, Yutaka,Kikuchi, Ayaka,Suga, Hiroyuki
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p. 6150 - 6154
(2017/09/15)
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- Aniline-terephthalaldehyde resin p-toluenesulfonate (ATRT) as a highly efficient and reusable catalyst for alcoholysis, hydrolysis, and acetolysis of epoxides
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Alcoholysis, hydrolysis, and acetolysis of epoxides were carried out in the presence of a catalytic amount of aniline-terephthalaldehyde resin p-toluenesulfonate (ATRT) to give the corresponding β-substituted alcohols in good yields. Alcoholysis and hydrolysis of epoxides catalyzed by ATRT proceeded faster than those by pyridinium p-toluenesulfonate (PPTS).
- Tanemura, Kiyoshi,Suzuki, Tsuneo
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p. 1781 - 1789
(2016/11/17)
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- Monoacetylation of carbohydrate diols via transesterification with ethyl acetate
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Monoacetylation of secondary diols in protected monosaccharides was achieved with ethyl acetate as acyl donor and sodium tert-butoxide as a base. The regioseletivity of the reaction varied depending on the substrate. This new method provides a simple, fast, and efficient method to access selectively acetylated carbohydrates that is compatible with acid-sensitive protecting groups. CSIRO 2014.
- Liu, Xuyu,Becker, Bernd,Cooper, Matthew A.
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p. 679 - 683
(2014/05/06)
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- Iron(III) tosylate catalyzed acylation of alcohols, phenols, and aldehydes
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Iron(III) p-toluenesulfonate (tosylate) is an efficient catalyst for acetylation of alcohols, phenols, and aldehydes. The acetylation of 1° and 2° alcohols, diols, and phenols proceeded smoothly with 2.0 mol % of catalyst. However, the reaction worked well with only a few 3° alcohols. The methodology was also applicable to the synthesis of a few benzoate esters but required the use of 5.0 mol % catalyst. Aldehydes could also be converted into the corresponding 1,1-diesters (acylals) under the reaction conditions. Iron(III) tosylate is an inexpensive, and easy to handle, commercially available catalyst.
- Baldwin, Neil J.,Nord, Anna N.,O'Donnell, Brendan D.,Mohan, Ram S.
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p. 6946 - 6949
(2013/01/15)
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- N-acyl 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) tetraphenylborate salts as O-acylating agents
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Air-stable and crystalline N-acyl DBN tetraphenylborate salts have been shown to be effective O-acylating agents, reacting with both primary and secondary alcohols to give the corresponding esters in good yields. In the case of diols, the N-acyl DBN·BPh4 salts have been shown to acylate regioselectively the primary alcohol functionality in the presence of a secondary alcohol. The DBN hydrotetraphenylborate side product can be readily removed by filtration, providing the ester products without the need for further purification.
- Taylor, James E.,Williams, Jonathan M.J.,Bull, Steven D.
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experimental part
p. 4074 - 4076
(2012/08/28)
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- Enantioselective production of (S)-1-phenyl-1,2-ethanediol from dicarboxyesters by recombinant Bacillus subtilis esterase
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The whole cells of recombinant Escherichia coli BL21 overexpressing a Bacillus subtilis esterase (BsE) were utilized to sequentially hydrolyze the dicarboxyester of 1-phenyl-1,2-ethanediol for production of (S)-1-phenyl-1,2- ethanediol (PED), exhibiting high hydrolytic activity, excellent regio- and enantioselectivities towards the dicarboxyester of PED. Among the dicarboxyesters with different acyl chains (e.g., acetyl, n-butyl, and n-hexyl), the best enantioselectivity (E = 176) was observed when PED diacetate was employed as the initial substrate. Various reaction conditions were systematically investigated for enantioselective hydrolysis of PED diacetate. Under the optimal reaction conditions, kinetic resolution of 100 mM PED diacetate resulted in 49% conversion within 1 h, affording (S)-PED in 96% ee. A 150-ml scale reaction was performed, affording (S)-PED in 49% yield and 95% ee. After recrystallization in chloroform, the optical purity of (S)-PED was improved up to >99% ee, with a total yield of 45%. These results imply that this recombinant esterase (BsE) is a potentially promising biocatalyst for bioproduction of (S)-PED, an important chiral building block with wide application in pharmaceutical industry and liquid-crystal display materials.
- Tian, Xin,Zheng, Gao-Wei,Li, Chun-Xiu,Wang, Zhi-Long,Xu, Jian-He
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experimental part
p. 80 - 84
(2012/02/13)
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- Bis(NHC)-palladium(II) complex-catalyzed dioxygenation of alkenes
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Bis(NHC)-Pd(II) complexes derived from l,l'-binaphthyl-2,2'-diamine (BINAM) were successfully first used to catalyze the dioxygenation of alkenes under mild conditions tolerant of air and moisture. Cationic NHC-Pd2+ diaquo complex 1e showed the highest catalytic activity to give 1,2dioxygenation products with good syn-diastereoselectivity for 1,2-disubstituted alkenes.
- Wang, Wenfeng,Wang, Feijun,Shi, Min
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experimental part
p. 928 - 933
(2010/05/01)
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- Chemo-, regio-, and stereoselective synthesis of syn -aryl glycol monoesters from aryl olefins with hydrogen peroxide catalyzed by RuCl 3
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Chemo-, regio-, and stereoselectivity have been achieved in the oxidations of aryl olefins. The aryl olefins were oxidized by 2 equivalents of H 2O2 in acetic acid, catalyzed by 0.02 equivalent of RuCl3, leading to the formations of syn-aryl glycol monoesters. As the reaction is concerted, both the regio- and stereoselectivity are excellent. In the presence of aliphatic C=C bonds, the aryl C=C bonds were selectively dioxygenated. This represents the first example of chemoselective dioxygenation of aryl C=C bonds. Georg Thieme Verlag Stuttgart - New York.
- Zhang, Yanqiao,Chu, Guobiao,Cui, Xiaoxue,Han, Zhijie,Dou, Daoke,Chen, Yuanli,Yu, Xiaosong,Li, Chunbao
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supporting information; experimental part
p. 1118 - 1122
(2010/06/20)
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- Ring-opening reactions of epoxides catalyzed by molybdenum(VI) dichloride dioxide
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Transformation of epoxides to β-alkoxy alcohols, acetonides, and α-alkoxy ketones is achieved by using molybdenum(VI) dichloride dioxide (MoO2Cl2) as a catalyst. Alcohol, aldehyde, oxime, tosyl, and tert-butyldimethylsilyl functional groups are tolerated during the methanolysis and acetonidation of the functionalized epoxides. No polymerization product is observed with any of the epoxides. Direct conversion of epoxides devoid of sensitive functional groups into the corresponding α-methoxy ketone is achieved in a single step by using the MoO2Cl 2/Oxone system. Georg Thieme Verlag Stuttgart.
- Jeyakumar, Kandasamy,Chand, Dillip Kumar
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p. 807 - 819
(2008/09/21)
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- NaIO4/LiBr-mediated diastereoselective dihydroxylation of olefins: A catalytic approach to the prevost-woodward reaction
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(Chemical Equation Presented) LiBr catalyzes efficiently the dihydroxylation of alkenes to afford syn and anti diols with excellent diastereoselectivity depending upon the use of NaIO4 (30 mol %) or PhI(OAc)2 (1 equiv), respectively, as the oxidants. The oxidation of non-benzylic halides has been achieved for the first time to afford the corresponding diols in excellent yields.
- Emmanuvel, Lourdusamy,Ali Shaikh, Tanveer Mahammad,Sudalai, Arumugam
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p. 5071 - 5074
(2007/10/03)
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- Rapid and efficient ring opening of epoxides catalyzed by a new electron deficient tin(IV) porphyrin
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The new electron deficient tin(IV) tetraphenylporphyrinato trifluoromethanesulfonate, [SnIV(tpp)(OTf)2], was used as an efficient catalyst for the alcoholysis, hydrolysis and acetolysis of epoxides. Conversion of epoxides to thiiranes and acetonides were also performed efficiently in the presence of this catalyst.
- Moghadam, Majid,Tangestaninejad, Shahram,Mirkhani, Valiollah,Shaibani, Reza
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p. 6105 - 6111
(2007/10/03)
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- Efficient regio- and stereoselective ring opening of epoxides with alcohols, acetic acid and water catalyzed by ammonium decatungstocerate(IV)
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Epoxides can be cleaved in a regio- and stereoselective manner under neutral conditions with alcohols and acetic acid in the presence of catalytic amounts of decatungstocerate(IV) ion, ([CeW10O36] 8-), affording the corresponding β-alkoxy and β-acetoxy alcohols in high yields. In water, ring opening of epoxides occurs with this catalyst to produce the corresponding diols in good yields.
- Mirkhani, Valiollah,Tangestaninejad, Shahram,Yadollahi, Bahram,Alipanah, Ladan
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p. 8213 - 8218
(2007/10/03)
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- Aminopropyl silica gel supported iodine as catalyst in nucleophilic ring opening of epoxides and episulfides
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Silica gel functionalized by aminopropyl group was prepared. Iodine was then supported on this inorganic polymer and used as a stable and efficient heterogeneous catalyst for nucleophilic ring opening reactions of epoxides and episulfides in different nucleophilic solvents such as alcohols, water and acetic acid.
- Tamami,Iranpoor,Mahdavi
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p. 1251 - 1258
(2007/10/03)
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- Ring opening of epoxides with carboxylates and phenoxides in micellar media catalyzed with Ce(OTf)4
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Efficient ring opening reaction of epoxides with carboxylates and phenoxide anions catalyzed with ceric triflate is performed in micellar media. This new method is a useful procedure for the preparation of β-carboxy and phenoxy alcohols from epoxides under mild reaction conditions.
- Iranpoor,Firouzabadi,Safavi,Shekarriz
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p. 2287 - 2293
(2007/10/03)
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- Iron(III) trifluoroacetate as an efficient catalyst for solvolytic and nonsolvolytic nucleophilic ring opening of epoxides
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Iron(III) trifluoroacetate was used as an efficient and nonhygroscopic catalyst for the alcoholysis, hydrolysis, and acetolysis of epoxides. The addition of chloride, bromide, iodide, and nitrate ions to epoxides to produce the corresponding 2-halo and 2-nitratoalkanols and also the conversion of epoxides to acetonides and thiiranes were also performed efficiently in the presence of this catalyst.
- Iranpoor, Nasser,Adibi, Hadi
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p. 675 - 680
(2007/10/03)
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- Bismuth(III) chloride (BiCl3); an efficient catalyst for mild, regio- and stereoselective cleavage of epoxides with alcohols, acetic acid and water
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Epoxides can be cleaved in a regio- and stereoselective manner with alcohols, acetic acid and water in the presence of catalytic amounts of bismuth(III) chloride, affording the corresponding β-alkoxy and β-acetoxy alcohols and diols in high yields.
- Mohammadpoor-Baltork,Tangestaninejad,Aliyan,Mirkhani
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p. 2365 - 2374
(2007/10/03)
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- Highly efficient, regio- and stereoselective ring opening of epoxides and thiiranes with Ce(OTf)4
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Ceric triflate, Ce(OTf)4 is used as an efficient catalyst for ring opening of epoxides in the presence of alcohols, water, and acetic acid. The reactions proceed with high regio and stereoselectivity and in excellent yields. The reaction of R(+) styrene oxide with methanol occurs with excellent optical purity. Ring opening of thiiranes in alcohols, water and acetic acid followed by dimerisation to the corresponding disulfides occur efficiently in the presence of this reagent. A mild method for the preparation of dithianes from thiiranes and Ce(OTf)4 is also described.
- Iranpoor,Shekarriz,Shiriny
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p. 347 - 366
(2007/10/03)
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- An Investigation on Desilylation of Alkyl and Phenolic Silyl Ethers Using FeCl3
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A variety of alkyl and phenolic TBDMS ethers have been efficiently cleaved using anhydrous FeCl3 in MeOH under mild conditions. It was found that choice of solvent is crucial for the rate of the deprotection of TBDMS ether with FeCl3.
- Saravanan, Parthasarathy,Singh, Vinod K.
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p. 565 - 567
(2007/10/03)
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- The baker's yeast reduction of 1-acetoxy-2-alkanones in the presence of a sulfur compound
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Improved enantioselectivity was achieved in the baker's yeast reduction of the 1-acetoxy-2-alkanone derivatives by the addition of a sulfur compound such as L-cysteine and phenyl vinyl sulfide. The reaction rate of the baker's yeast reduction was accelerated using a sulfur compound as an additive. The migration of the acetyl group and the hydrolysis of the acetoxy group of the substrate was suppressed using a sulfur compound.
- Hayakawa, Ryuuichirou,Shimizu, Makoto,Fujisawa, Tamotsu
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p. 3201 - 3204
(2007/10/03)
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- Iodine and iodine supported on polyvinylpyrrolidone as catalysts and reagents for alcoholysis, hydrolysis, and acetolysis of epoxides and thiiranes
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Iodine and iodine supported on polyvinylpyrrolidone (betadine) have been used as catalysts for ring opening of epoxides and as reagent for ring-opening dimerization of thiiranes in alcohols, water, and acetic acid. The reactions occur with high regio-, chemo-, and stereoselectivity. The reaction of R-(+)-styrene oxide with I2 supported on PVP in methanol was found to be very stereospecific and the product was isolated in 93% ee.
- Iranpoor, Nasser,Tamami, Bahman,Niknam, Khodabakhsh
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p. 1913 - 1919
(2007/10/03)
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- Organotin-mediated monoacylation of diols with reversed chemoselectivity. Mechanism and selectivity
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The monoesterification of unsymmetrically substituted diols, which occurs at the most substituted hydroxyl when activation of the substrate is achieved through its dibutylstannylene acetal, has been investigated to ascertain the origin of the unusual reversal of chemoselectivity. A mechanism in which the dibutylstannylene acetal plays the double role of reagent and catalyst has been established, which accounts for the reactivity, selectivity, and product distribution of the reaction. The reaction pathway involves three subsequent steps, namely, (a) esterification, (b) intra- and intermolecular transesterification, and (c) quench; interplay between kinetic and thermodynamic control over the three steps is responsible for the observed product distribution. The knowledge of the reaction mechanism allows for adjustment of experimental conditions to achieve optimum selectivity, which can be > 99% with the appropriate choice of reagents. The stannylation procedure converts hydroxyls into functional groups highly chemoselective toward acyl reagents, but inert toward sulfonyl halides and alkylating reagents. The reactivity of the Sn-O bond has been found to decrease with decreasing the electronegativity of ligands on tin, while halide ligands appear to be essential for reversal of chemoselectivity. A structure has been proposed for the catalytic species, in which complexation of the stannyl monoester intermediates with the starting dioxastannolane reagent activates the stannylated oxygen toward addition to the carbonyl and at the same time accounts for the steric hindrance that biases the intramolecular transesterification equilibrium toward the thermodynamically most stable monoester of the most substituted hydroxyl.
- Roelens, Stefano
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p. 5257 - 5263
(2007/10/03)
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- FeCl3·6H2O supported on SiO2 catalysed ring opening of epoxides with alcohols, acetic acid, water, chloride, bromide and nitrate ions
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FeCl3·6H2O absorbed on chromatographic silica gel can act as an efficient catalyst for alcoholysis, hydrolysis and acetolysis of epoxides. Methanolysis of (R)-styrene oxide proceeds with high stereospecificity and in excellent yield. This catalyst can also convert epoxides to their corresponding β-halohydrins and β-nitrato alcohols in the presence of chloride, bromide and nitrate ions respectively.
- Iranpoor, Nasser,Tarrian, Tahere,Movahedi, Zarangiz
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p. 1473 - 1476
(2007/10/03)
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- CERIC AMMONIUM NITRATE, AN EFFICIENT CATALYST FOR MILD AND SELECTIVE OPENING OF EPOXIDES IN THE PRESENCE OF WATER THIOLS AND ACETIC ACID
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Ring opening of epoxides with catalytic amounts of Ce(IV) as ceric ammonium nitrate (CAN) are performed efficiently in the presence of water, thiols and acetic acid under mild conditions.The epoxides are opened with high regio-and stereoselectivity and with good to excellent yields.The products formed from the reaction of polar substituted epoxides in acetic acid were found to be derivative of succinic acid diester.The mechanism of the reaction is believed to be a radical type, involving the formation of an epoxonium radical cation.
- Iranpoor, N.,Baltork, Mohammadpour I.,Zardaloo, F. Shiriny
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p. 9861 - 9866
(2007/10/02)
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- Sonochemical switching from Ionic to Radical Pathways in the Reactions of Styrene and trans-β-Methylstyrene with Lead Tetraacetate
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The reactions of sryrene and trans-β-methylstyrene with lead tetraacetate in acetic acid are greatly influenced by ultrasonic irradiation to give products resulting mostly from radical chain pathways, whereas mechanical agitation gives products only from ionic processes.
- Ando, Takashi,Bauchat, Patrick,Foucaud, Andre,Fujita, Mitsue,Kimura, Takahide,Sohmiya, Hajime
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p. 6379 - 6382
(2007/10/02)
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- Organotin-Mediated Monoacylation of Diols with Reversed Chemoselectivity: A Convenient Synthetic Method
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The organotin-mediated monoesterification of unsymmetrical diols with reversed chemoselectivity has been explored to ascertain scope and limits of the method and to provide an easy and convenient synthetic procedure.The reaction has been performed on a set of substituted diols with some acylating agents usually employed as protecting groups.Two different procedures have been devised to obtain either the desired diol monoesters directly or the corresponding trialkylsilyl ethers as protected derivatives.The latter provides a convenient approach to the preparation of easily interconvertible diol monoesters.Also, the reaction has been optimized as a one-pot procedure, avoiding the isolation and purification of the stannylated intermediates.The reversed monoesterification method has been successfully applied to 1,2-, 1,3-, and 1,4-diols of primary-secondary, primary-tertiary, and secondary-tertiary types and to ether functions containing 1,2-diols.Within its limits, the described method represents the first direct one-pot monoesterification of diols at the most substituted site, allowing some remarkable achievements as (a) an almost regiospecific reversed monobenzoylation of some 1,2-diols, (b) the selective acylation of the tertiary hydroxyl of a primary-tertiary diol, and (c) a highly selective preparation of secondary pivalate of primary-secondary diols.
- Reginato, Gianna,Ricci, Alfredo,Roelens, Stefano,Scapecchi, Serena
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p. 5132 - 5139
(2007/10/02)
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- Dual-function Phase-transfer Catalysis in the Metal-assisted Oxidation by Hydrogen Peroxide of Styrene to Benzaldehyde or Acetophenone
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Quaternary ammonium salts assist the extraction of both hydrogen peroxide and metal salts, e.g. ruthenium or palladium chloride from the aqueous to the non-aqueous component of a two-phase system; the system has been used for the oxidation of styrene.
- Barak, Gabriela,Sasson, Yoel
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p. 1266 - 1267
(2007/10/02)
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- The Role of Copper(II) Salts in the Oxidation of Aryl-substituted Alkenes by Peroxydisulphate Anion
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The effect of copper(II) ions on the oxidation, in acetic acid, of aryl-substituted alkenes by peroxydisulphate anion has been investigated.In the presence of the metal ions an electron-transfer process operates akin to that identified in the oxidation of alkenes by other one-electron oxidants.It is suggested that the electron-transfer agent is copper(III) and that the resultant alkene radical-cation is converted into hydroxy acetates in good yield.S2O8(2-) alone decomposes more slowly to SO4(*-) which undergoes radical addition to the alkene leading ultimately to diacetates.The presence of sodium acetate in the system reduces considerably the conversion of alkene as a result, it is suggested, of competitive oxidation of the acetate anion.
- Dobson, Peter,Norman, Julie A.,Thomas, C. Barry
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p. 1209 - 1214
(2007/10/02)
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- SELECTIVE ACYLATIONS OF AMINOPHENOLS AND HYDROXYALKYLPHENOLS WITH 1-ACETYL-v-TRIAZOLOPYRIDINE.
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The title triazolide serves as a convenient reagent for highly chemoselective acetylations of aminophenols and hydroxyalkylphenols.
- Paradisi, Mario Paglialunga,Zecchini, Giampiero Pagani,Torrini, Ines
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p. 5029 - 5032
(2007/10/02)
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- Radical-Cations as Intermediates in the Oxidation of Alkenes by Metal Ions
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The formation of hydroxy acetates in the reaction of some alkenes with lead(IV), cobalt(III), and manganese(III) in acetic acid is demonstrated to involve the intermediacy of alkene radical-cations.A study employing a range of aryl-substituted alkenes has shown that there is an inverse relationship between the yield of hydroxy acetate and the ionisation potential of the organic substrate.The electron deficiency in the radical-cations derived from these alkenes appears to be localised on the double bond: no evidence could be obtained for reaction at the aromatic ring.The introduction of the chlorine atom into this ring had the effect of repressing electron-transfer in cobalt(III) and manganese(III) oxidations but not in those involving lead(IV).
- Norman, Julie A.,Thomas, C. Barry,Burrow, Michael J.
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p. 1087 - 1094
(2007/10/02)
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- 3-ACYL-2-OXAZOLONE-ZIRCONIUM COMPLEXES AS EXCELLENT REAGENTS FOR HIGHLY REGIOSELECTIVE ACYLATION OF POLYALCOHOLS
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In combination with 3-acyl-2-oxazolones, zirconium complexes such as zirconium acetylacetonate and zirconocene chloride hydride-Mg serve well as effective catalysts for regioselective acylation of polyalcohols including 1,2-diols to permit higly preferential protection of primary hydroxyl groups.
- Kunieda, Takehisa,Mori, Takashi,Higuchi, Tsunehiko,Hirobe, Masaaki
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p. 1977 - 1980
(2007/10/02)
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- OXIDATION BY COBALT(III) ACETATE. PART 6. A NOVEL SYNTHESIS OF THE GLYCOL MONOACETATES FROM AROMATIC OLEFINS IN WET ACETIC ACID
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Oxidation of various aryl-conjugated olefins with cobalt(III) acetate in wet acetic acid under nitrogen affords the glycol monoacetates in moderate to good yields.None of the phenyl rearrangement product is formed in the present reactions.These results are best interpreted by assuming the formation of a Co-co-ordinated intermediate.
- Hirano, Masao,Morimoto, Takashi
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p. 1033 - 1036
(2007/10/02)
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- ACTIVATION OF CARBOXYL GROUPS BY DIPHENYL 2-OXO-3-OXAZOLINYLPHOSPHONATE. FACILE PREPARATION OF VERSATILE REAGENTS, 3-ACYL-2-OXAZOLONES
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Synthetic utility of the 2-oxazolone moiety as an excellent new leaving group is described.Based on such a function of the heterocycles, diphenyl 2-oxo-3-oxazolinylphosphonate has been newly introduced as a carboxyl-activating reagent which permits a facile direct preparation of 3-acyl-2-oxazolones and amides including peptides from a wide variety of carboxylic acids.The 3-acyl-2-oxazolides also serve as versatile reactive agents for highly chemoselective acyl-transfer to the nucleophilic species such as amines, alcohols and thiols, providing convenient and high-yield routes to amides, esters and thiol esters under mild conditions.They are also useful intermediates for ketones and alcohols.
- Kunieda, Takehisa,Higuchi, Tsunehiko,Abe, Yoshihiro,Hirobe, Masaaki
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p. 3253 - 3260
(2007/10/02)
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- HIGHLY SELECTIVE ACYLATION OF AMINES AND ALCOHOLS BY POLY(3-ACYL-2-OXAZOLONE)
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Poly(3-acyl-2-oxazolone) serves as a convenient reagent for highly chemo- and regioselective acylation of polyamines, amino-alcohols and polyalcohols.
- Kunieda, Takehisa,Higuchi, Tsunehiko,Abe, Yoshihiro,Hirobe, Masaaki
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p. 1159 - 1160
(2007/10/02)
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- THALLIUM NITRATE AS A REAGENT FOR THE CONVERSION OF EPOXIDES INTO α-HIDROXY-NITRATE ESTERS AND FOR THE CLEAVAGE OF ALIPHATIC ETHERS
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Simple as well as steroidal oxiranes are converted into the corresponding α-hidroxy nitrate esters by treatment with Tl(NO3)3 in hexane solution.Moreover aliphatic ethers react with Tl(NO3)3 in acetic anhydride via cleavage of the ethereal bond and formation of the corresponding acetoxy derivatives.
- Mincione, E.,Lanciano, F.
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p. 1149 - 1150
(2007/10/02)
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- Oxidation by Cobalt(III) Acetate. Part 2. Oxidation of Styrene in Acetic Acid
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The oxidation of styrene with cobalt(III) acetate has been studied in acetic acid under nitrogen.The product distribution is greatly affected by the composition of the solvent; in acetic acid and in wet acetic acid the reaction exclusively leads to 1,2-addition products, whereas in dry acetic acid preconditioned with acetic anhydride extensive formation of radical products is observed.None of the conditions gave rise to a rearrangement product.A Co-co-ordinated intermediate is proposed for the formation of 1,2-addition products.
- Hirano, Masao,Kitamura, Emi,Morimoto, Takashi
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p. 569 - 573
(2007/10/02)
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