- A Direct Method for the Efficient Synthesis of Benzylidene Acetal at Room Temperature
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For the first time, a metal-free direct method has been developed for the efficient synthesis of benzylidene acetal at room temperature using Dowex 50WX8 as a solid acid catalyst and Cl3CCN as a novel water scavenger. At room temperature, a wide variety of aryl and α,β-unsaturated aldehydes react readily with functionalized 1,2- and 1,3-diols to furnish the corresponding acetals in very good yields. Labile functional groups, like N-Boc, N-Cbz, -OTBDMS, -OBn, -N3 and acetonide are found to be stable under the reaction conditions. The versatility of this method is further demonstrated with carbohydrate substrates and optically active diols.
- Reddy, Narra Rajashekar,Kumar, Rashmi,Baskaran, Sundarababu
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supporting information
p. 1548 - 1552
(2019/01/09)
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- Synthesis of a simplified triazole analogue of pateamine A
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Pateamine A is a naturally occurring metabolite extracted from the marine sponge Mycale hentscheli. It exhibits potent cytotoxicity towards cancer cell lines and has been shown to target protein translation initiation via inhibition of the function of euk
- Hemi Cumming,Brown, Sarah L.,Tao, Xu,Cuyamendous, Claire,Field, Jessica J.,Miller, John H.,Harvey, Joanne E.,Teesdale-Spittle, Paul H.
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p. 5117 - 5127
(2016/06/14)
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- Cyclopentyl methyl ether-NH4X: A novel solvent/catalyst system for low impact acetalization reactions
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Cyclopentyl methyl ether, a low impact ether forming a positive azeotrope with water, was successfully employed as a solvent in the synthesis of 1,3-dioxanes and 1,3-dioxolanes carried out under Dean-Stark conditions by the acetalization of aliphatic and aromatic aldehydes or ketones, employing ammonium salts as environmentally friendly acidic catalysts.
- Azzena, Ugo,Carraro, Massimo,Mamuye, Ashenafi Damtew,Murgia, Irene,Pisano, Luisa,Zedde, Giuseppe
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supporting information
p. 3281 - 3284
(2015/06/25)
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- A METHOD OF ACETALIZING AN ALDEHYDE
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A method of acetalizing an aldehyde comprising reacting said aldehyde with an alcohol in the presence of a polymeric catalyst to form an acetal wherein the polymeric catalyst is a mesoporous poly-melamine-formaldehyde polymer.
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-
Page/Page column 22; 23; 24
(2013/09/26)
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- Synthesis of 2-R-1,3-dioxanes, derivatives of functionally substituted aldehydes of vanillin series
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By the condensation of substituted aldehydes of vanillin series with 1,3-propanediol in boiling benzene in the presence of sulfo cation exchanger FIBAN K-1 as catalyst functionally 2-R-substituted 1,3-dioxanes were synthesized.
- Dikusar,Potkin,Zvereva,Zhukovskaya,Petkevich,Pavlyuchenkova,Murashova,Polikarpov,Shunkevich,Yuvchenko,Zolotar'
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p. 221 - 227
(2013/07/25)
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- Mesoporous poly-melamine-formaldehyde (mPMF)-a highly efficient catalyst for chemoselective acetalization of aldehydes
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A mesoporous poly-melamine-formaldehyde polymer with a high surface area, good porosity and a high density of amine and triazine functional groups was investigated as a highly efficient hydrogen-bonding catalyst. This porous organic polymer was found to be highly effective in catalyzing chemoselective acetalization of aldehydes, without the consumption of any dehydrating agents. The turnover frequency of mesoporous poly-melamine-formaldehyde is hundreds of times higher than melamine monomer, and this high efficiency is due to the high density of aminal (-NH-CH2-NH-) groups and triazine rings in the polymer network, which provides an inherently powerful system with multiple hydrogen bonds. This unique characteristic imparts mesoporous poly-melamine-formaldehyde polymer with a very high activity as a heterogeneous organocatalyst. The polymer is also low cost, and easy to be synthesized and recycled.
- Tan, Mei Xuan,Gu, Liuqun,Li, Nannan,Ying, Jackie Y.,Zhang, Yugen
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p. 1127 - 1132
(2013/06/05)
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- Organocatalysis for the acid-free O-arylidenation of carbohydrates
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Methyl glycopyranosides of glucose, galactose, and mannose, their 2,3-di-O-benzyl-protected derivatives, as well as the unprotected sugars react with p-methoxybenzaldehyde dimethyl acetal (3) and with benzaldehyde dimethyl acetal (7) as reagents in the presence of thiourea 1 or squaramide 2 as the organocatalyst to afford regioselectively 4,6-O-arylidenated derivatives 5 and 8. With an excess amount of 3 or 7, diarylidenated derivatives are also obtained. In situ formation of acetals of type 3 and 7 from corresponding aldehydes 10 and 13 in the presence of an orthoester and organocatalyst 1 or 2 can be used to generate 5 and 8 directly from the aldehydes. Some substrates also lead to mixed orthoesters with this procedure. The reaction courses are discussed. A squaramide catalyzes the 4,6-O-arylidenation of glucose, mannose, and galactose with the use of arenecarbaldehyde dimethyl acetals or arenecarbaldehydes and orthoesters as the reagents. Glycoside derivatives also undergo this reaction. Copyright
- Geng, Yiqun,Faidallah, Hassan M.,Albar, Hassan A.,Mhkalid, Ibrahim A.,Schmidt, Richard R.
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p. 7035 - 7040
(2013/11/06)
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- Synthesis of the C1-C9 fragment of the potent antitumor agent dictyostatin
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We describe herein a short and efficient synthesis of the C1-C9 fragment of the potent antitumor agent dictyostatin. Notable features of this approach include a Sharpless asymmetric epoxidation followed by epoxide opening under Myashita's conditions to in
- Dias, Luiz C.,Sant'ana, Danilo P.,Vieira, Ygor W.,Gonc?alves, Caroline C.S.,Lima, Dimas J.P.
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scheme or table
p. 344 - 348
(2012/06/01)
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- 2,3-dichloro-5,6-dicyano-1,4-benzoquinone-catalyzed teactions employing MnO2 as a stoichiometric oxidant
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Several oxidative reactions can be effected with MnO2 in the presence of substoichiometric quantities of DDQ. These transformations include oxidative cyclization, deprotection, and dehydrogenation reactions. The use of MnO2 as a terminal oxidant for DDQ-mediated reactions is attractive based on economical and environmental factors.
- Liu, Lei,Floreancig, Paul E.
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supporting information; experimental part
p. 4686 - 4689
(2010/12/24)
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- Further studies toward the stereocontrolled synthesis of silicon-containing peptide mimics
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Further studies are reported on the utilization of the versatile reaction between chiral sulfinimines and alkyldiphenylsilyl lithium reagents with the goal of preparing a wide range of silanediol-based protease inhibitors. In particular, focus has been placed to demonstrate how a number of genetically encoded amino acid side chains such as serine, threonine, tyrosine, lysine, proline, arginine, aspartate and asparagine might be incorporated into the overall approach. Efforts to apply this synthetic methodology for accessing biologically relevant silanediol dipeptide mimics are also described. This includes the synthesis of a potential inhibitor of the human neutrophil elastase, as well as a diphenylsilane mimic of a hexapeptide fragment of the human islet amyloid polypeptide.
- Hernandez, Dacil,Lindsay, Karl B.,Nielsen, Lone,Mittag, Tina,Bjerglund, Klaus,Friis, Stig,Mose, Rasmus,Skrydstrup, Troels
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supporting information; experimental part
p. 3283 - 3293
(2010/08/07)
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- Acetalization of carbonyl compounds catalyzed by bismuth triflate under solvent-free conditions
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Carbonyl compounds were converted to the corresponding 1,3-dioxolanes and 1,3-dioxanes with ethylene glycol and 1,3-propandiol in the presence of bismuth triflate under solvent-free conditions. In addition, high chemoselective protection of aldehydes in the presence of ketones has been achieved.
- Aliyan, Hamid,Fazaeli, Razieh,Massah, Ahmad Reza,Momeni, Ahmad Reza,Naghash, Hamid Javaherian,Moeinifard, Behzad
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experimental part
p. 873 - 876
(2012/04/05)
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- Stereoselective total synthesis of etnangien and etnangien methyl ester
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A highly stereoselective joint total synthesis of the potent polyketide macrolide antibiotics etnangien and etnangien methyl ester was accomplished by a convergent strategy and proceeds in 23 steps (longest linear sequence). Notable synthetic features include a sequence of highly stereoselective substrate-controlled aldol reactions to set the characteristic assembly of methyl- and hydroxyl-bearing stereogenic centers of the propionate portions, an efficient diastereoselective Heck macrocyclization of a deliberately conformationally biased precursor, and a late-stage introduction of the labile side chain by means of a high-yielding Stille coupling of protective-group-free precursors. Along the way, an improved, reliable protocol for a Z-selective Stork?Zhao?Wittig olefination of aldehydes was developed, and an effective protocol for a 1,3-syn reduction of sterically particularly hindered β-hydroxy ketones was devised. Within the synthetic campaign, a more detailed understanding of the intrinsic isomerization pathways of these labile natural products was elaborated. The expedient and flexible strategy of the etnangiens should be amenable to designed analogues of these RNA-polymerase inhibitors, thus enabling further exploration of the promising biological potential of these macrolide antibiotics.
- Li, Pengfei,Li, Jun,Arikan, Fatih,Ahlbrecht, Wiebke,Dieckmann, Michael,Menche, Dirk
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supporting information; experimental part
p. 2429 - 2444
(2010/07/06)
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- Highly efficient and chemoselective acetalization of carbonyl compounds catalyzed by new and reusab e zirconyl triflate, zr0(0tf)2
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Various types of aromatic aldehydes were efficiently converted to their corresponding 1,3-dioxanes and 1,3-dioxolane with 1,3-propanediol and ethylene glycol, respectively, in the presence of catalytic amount of ZrO(OTf) 2 in acetonitrile at room temperature. The catalyst can be reused several times without loss of its catalytic activity. Very short reaction times, selective acetalization of aromatic aldehydes in the presence of aliphatic aldehydes and ketones, very mild reaction conditions, reusability of the catalyst, and easy workup are noteworthy advantages of this method.
- Moghadam, Majid,Mohammadpoor-Baltork, Iraj,Tangestaninejad, Shahram,Mirkhani, Valiollah,Yazdani, Parvin,Ghorjipoor, Saeedeh
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experimental part
p. 131 - 135
(2009/09/30)
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- Diastereodivergent Aldol reactions of β-alkoxy ethyl ketones: Modular access to (1,4)-syn and -anti polypropionates
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(Chemical Equation Presented) Asymmetric substrate-controlled aldol reactions of ethyl ketones of type 4 with aldehyde 3 are reported. Modular access to all possible syn-and anti-aldol products was obtained by careful choice of reaction conditions. To ach
- Arikan, Fatih,Li, Jun,Menche, Dirk
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supporting information; experimental part
p. 3521 - 3524
(2009/05/27)
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- Intermolecular reactions of chlorohydrine anions: Acetalization of carbonyl compounds under basic conditions
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Nonenolizable aldehydes and ketones react with 2-chloroethanol and 3-chloropropanol under basic conditions (t-BuOK, DMF/THF) with formation of 2-substituted 1,3-dioxolanes and 1,3-dioxanes, respectively. Conversion of the two-step addition-alkylation process depends on the electrophilicity of the carbonyl group that governs the equilibrium of addition of chloroalkoxides. This method of protection of carbonyl groups in the form of cyclic acetals under kinetically controlled conditions is complementary to the acid-catalyzed reaction with diols.
- Barbasiewicz, Michal,Makosza, Mieczyslaw
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p. 3745 - 3748
(2007/10/03)
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- N-bromosuccinimide (NBS) catalyzed highly chemoselective acetalization of carbonyl compounds using silylated diols and pentaerythritol under neutral aprotic conditions
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Various types of carbonyl compounds are efficiently converted to their 1,3-dioxanes and pentaerythritol diacetals by the use of either 1,3-bistrimethylsiloxy propane (A) or 1,3-bistrimethylsilanyloxy-2,2- bistrimethylsilanyloxymethyl propane (D) and a catalytic amount of N-bromosuccinimide (3-10 mol%) under essentially neutral aprotic condition, respectively. A variety of functionalities such as both aliphatic and phenolic -OTBDMS, -OMe, -OBz, furan ring, double bonds and more significantly phenolic -OTHP survived under the present reaction condition. The efficient conversion of two α-tertiary ketones to their cyclic acetals was also achieved using the present protocol.
- Karimi, Babak,Hazarkhani, Hassan,Maleki, Jafar
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p. 279 - 285
(2007/10/03)
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- A convenient and highly efficient method for the protection of aldehydes using very low loading hydrous ruthenium(III) trichloride as catalyst
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A convenient method for the chemoselective protections of both aliphatic and aromatic aldehydes has been developed. Ruthenium(III) trichloride (0.1 mol %) has found to be an highly efficient catalyst in the acetalizations of aldehydes with various simple alcohols such as methanol, ethanol, or diols such as 1,2-ethylanediol and 1,3-propanediol under mild reaction conditions.
- Qi, Jian-Ying,Ji, Jian-Xin,Yueng, Chi-Hung,Kwong, Hoi-Lun,Chan, Albert S.C.
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p. 7719 - 7721
(2007/10/03)
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- A simple and practical synthetic protocol for acetalisation, thioacetalisation and transthioacetalisation of carbonyl compounds under solvent-free conditions
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A wide variety of carbonyl compounds can be converted smoothly to the corresponding acetals on treatment with alcohols or diols and triethyl orthoformate in the presence of a catalytic amount of (bromodimethyl)sulfonium bromide at room temperature. Similarly, various carbonyl compounds can be transformed into the corresponding dithioacetals on reaction with thiol or dithiols at room temperature by employing the same catalyst without any solvent. Moreover, O,O-acetals can also be converted into the corresponding dithioacetals under identical conditions. Some of the major advantages are mild reaction conditions, a high degree of efficiency, compatibilty with other protecting groups and the lack of solvents, particularly for thioacetalisation. In addition, no brominations occur at the double bond or α to the keto position or even in the aromatic ring under these experimental conditions. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Khan, Abu T.,Mondal, Ejabul,Ghosh, Subrata,Islam, Samimul
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p. 2002 - 2009
(2007/10/03)
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- Total synthesis of (-)-pironetin
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(Matrix presented) The asymmetric total synthesis of pironetin, a compound that shows plant growth regulatory activity, immunosuppressive as well as a remarkable antitumoral activity, is described. The approach involves the use of three very efficient Eva
- Dias, Luiz C.,De Oliveira, Luciana G.,De Sousa, Marcio A.
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p. 265 - 268
(2007/10/03)
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- Highly efficient and chemoselective interchange of 1,3-oxathioacetals and dithioacetals to acetals promoted by N-halosuccinimide
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Highly efficient interconversion of a range of 1,3-oxathiolanes, 1,3-dithiolanes and 1,3-dithianes to their acetals at ambient temperature using N-bromosuccinimide or N-chlorosuccinimide and different types of alcohols and diols was investigated.
- Karimi, Babak,Seradj, Hassan,Maleki, Jafar
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p. 4513 - 4516
(2007/10/03)
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- Iodine-catalyzed, efficient and mild procedure for highly chemoselective acetalization of carbonyl compounds under neutral aprotic conditions
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Various types of carbonyl compounds are efficiently converted to their 1,3-dioxanes by the use of 1,3-bis(trimethylsiloxy)propane (BTSP) and a catalytic amount of iodine (3-7 mol%) under essentially neutral aprotic condition.
- Karimi, Babak,Golshani, Behzad
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p. 784 - 788
(2007/10/03)
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- Stereodivergent approach to enantiopure hydroxyindolizidines through 1,3-dipolar cycloaddition of 3-hydroxypyrroline N-oxide derivatives
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The (3S)-3-alkoxypyrroline N-oxides 7 and 27 were easily prepared from 1-malic acid and used as starting materials for enantiospecific syntheses of stereo differentiated polyhydro-xyindolizidines. Selection of the appropriate modality (inter or intramolec
- Cordero, Franca M.,Pisaneschi, Federica,Gensini, Martina,Goti, Andrea,Brandi, Alberto
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p. 1941 - 1951
(2007/10/03)
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- Tetrabutylammonium tribromide (TBATB) as an efficient generator of HBr for an efficient chemoselective reagent for acetalization of carbonyl compounds
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Acyclic and cyclic acetals of various carbonyl compounds were obtained in excellent yields under a mild reaction condition in the presence of trialkyl orthoformate and a catalytic amount of tetrabutylammonium tribromide (TBATB) in absolute alcohol. Chemoselective acetalization of an aldehyde in the presence of ketone, unsymmetrical acetal formation, shorter reaction times, mild reaction conditions, the stability of acid-sensitive protecting groups, high efficiencies, facile isolation of the desired products, and the catalytic nature of the reagent make the present methodology a practical alternative.
- Gopinath, Rangam,Haque, Sk. Jiaul,Patel, Bhisma K.
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p. 5842 - 5845
(2007/10/03)
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- Stereoselective approach to hydroxyindolizidines: Protection/deprotection of the nitrone functionality via cycloaddition/retrocycloaddition
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(equation presented) The enantiomerically pure indolizidine (-)-21 has been synthesized starting from L-malic acid. The key intermediate 20 has been assembled through an intramolecular 1,3-dipolar cycloaddition of a nitrone generated in situ by retrocyclo
- Cordero, Franca M.,Gensini, Martina,Goti, Andrea,Brandi, Alberto
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p. 2475 - 2477
(2007/10/03)
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- Synthetic studies on pectenotoxins: Synthesis of the common C8-C18 THF fragment
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The stereoselective synthesis of the common C8-C18 THF fragment of pectenotoxins is reported. The THF ring was constructed by the ring closure of the epoxide possessing all six asymmetric centers with a 5-exo-mode. These stereogenic centers were arranged successively from the enantiomerically active epoxide by utilizing the stereo-differentiating influence of the proximal functional groups.
- Awakura,Fujiwara,Murai
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p. 1733 - 1736
(2007/10/03)
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- Superacid-Catalyzed Reductive Friedel-Crafts Reaction of Arenes Using Arenecarbaldehyde Acetals
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Reaction of 2-aryl-1,3-dioxane with arenes in the presence of a catalytic amount of trifluoromethane-sulfonic acid gave the corresponding diarylmethanes in good to excellent yields. The acid-catalyzed Friedel-Crafts benzylation of arenes could altenatively be carried out using arenecarbaldehyde and 1,3-propanediol. The reaction was assumed to proceed through a redox process involving hydride shift from the cyclic acetal moiety to the benzylic carbon. The hydride shift was confirmed by the reaction with 5-ethyl-2-phenyl-4,4,6,6-tetradeuterio-1,3-dioxane, wherein more than 90% deuterium was incorporated into the benzylic carbon of the diphenylmethane. Diphenylmethyl ether Ph2CHOCH2CH2CH2OH also reacted with benzene to afford diphenylmethane under the same reaction conditions, suggesting that the ether should be the plausible intermediate that underwent the hydride shift.
- Fukuzawa, Shin-Ichi,Tsuchimoto, Teruhisa,Hiyama, Tamejiro
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p. 151 - 156
(2007/10/03)
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- A Selectivity Study of Activated Ketal Reduction with Borane Dimethyl Sulfide
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A chemo- and regioselectivity study of the reagent combination BH3*SMe2/TMSOTf for ketal reduction has been undertaken.It has revealed that simple 1,3-dioxanes reduce cleanly at low temperature in CH2Cl2 while simple 1,3-dioxolanes may give complete ring cleavage and dimerization products.A study of reduction of 4-substituted 1,3-dioxolanes has revealed a solvent-directed regioselectivity which in THF favors the secondary protected derivative.A mechanism is postulated to account for the selectivities based on recent thinking on acetal substitution reactions.
- Bartels, Birgit,Hunter, Roger
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p. 6756 - 6765
(2007/10/02)
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- Synthese d'acetals cycliques dans des conditions douces; Applications a l'acetalisation du chloramphenicol
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Acetalization of 1-2 and 1-3 diols, even as sterically crowded as chloramphenicol, by carbonyl derivatives with substituents of various sizes has been performed at room temperature under mild conditions, by using heterogeneous catalysis (sulfonated polystyrene) in the presence of molecular sieves.Several new acetals of chloramphenicol have thus been obtained in good yields, isolated and characterized.
- Meslard, J. C.,Subira, F.,Vairon, J. P.,Guy, A.,Garreau, R.
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