- Metal Triflates for the Production of Aromatics from Lignin
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The depolymerization of lignin into valuable aromatic chemicals is one of the key goals towards establishing economically viable biorefineries. In this contribution we present a simple approach for converting lignin to aromatic monomers in high yields under mild reaction conditions. The methodology relies on the use of catalytic amounts of easy-to-handle metal triflates (M(OTf)x). Initially, we evaluated the reactivity of a broad range of metal triflates using simple lignin model compounds. More advanced lignin model compounds were also used to study the reactivity of different lignin linkages. The product aromatic monomers were either phenolic C2-acetals obtained by stabilization of the aldehyde cleavage products by reaction with ethylene glycol or methyl aromatics obtained by catalytic decarbonylation. Notably, when the method was ultimately tested on lignin, especially Fe(OTf)3 proved very effective and the phenolic C2-acetal products were obtained in an excellent, 19.3±3.2 wt % yield.
- Deuss, Peter J.,Lahive, Ciaran W.,Lancefield, Christopher S.,Westwood, Nicholas J.,Kamer, Paul C. J.,Barta, Katalin,de Vries, Johannes G.
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- Stereoselective Anti-Markovnikov Geminal Diamination and Dioxygenation of Vinylarenes Mediated by the Bromonium Ion
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A straightforward method is reported for the stereoselective anti-Markovnikov geminal diamination and stoichiometric geminal dioxygenation of vinylarenes mediated by a bromonium ion. The role of the substituent on the nucleophile and the nucleophilicity of the heteroatom in the competing geminal and vicinal addition pathways has been described. The stereoselectivity of the geminal dioxygenation is dependent on the ring size of the product and the position of the substituent that induces the stereoselectivity. The migration of the phenyl group through a semi-pinacol rearrangement during the geminal addition process was confirmed by the results of deuterium labelling studies.
- Balaji, Pandur Venkatesan,Chandrasekaran, Srinivasan
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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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- New Br?nsted-Lewis acidic quaternary ammonium ionic liquids: Synthesis, acidity determination and acidity-catalytic activity relationship
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A series of new Br?nsted-Lewis acidic ionic liquids, which are operational simplicity, high stability, low cost and applicable for scaling up, have been synthesized and their activity for acetalization was examined. The comprehensive studies on the acidity-catalytic performance relationship of the Br?nsted-Lewis acidic ionic liquids were performed. IR spectroscopy results confirmed that the new Br?nsted-Lewis acidic ionic liquids possess both Br?nsted and Lewis acid sites. The acidities were determined by Hammett method, and further studies on acidity-activity relationship revealed that the acidity played a key role in the acid-catalyzed probe reactions.
- Yi, Fengping,Gao, Jie,Zhang, Lirong,Jiang, Xiaoyan
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- Cesium hydroxide catalyzed addition of alcohols and amine derivatives to alkynes and styrene
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In the presence of catalytic amounts of cesium hydroxide (CsOH · H2O), alcohols, substituted anilines and heterocyclic amines undergo an addition in NMP to phenylacetylene leading to functionalized enol ethers and enamines. Anilines add to styrene (90-120°C, 12-14 h) leading to N-substituted anilines in satisfactory yields.
- Tzalis, Dimitrios,Koradin, Christopher,Knochel, Paul
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- Acetalization of carbonyl compounds catalyzed by acidic ionic liquid immobilized on silica gel
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Imidazolium-silica heterogeneous catalyst (SG-[(CH2) 3SO3H-HIM]HSO4) was prepared by immobilization of acidic ionic liquid 1-(propyl-3-sulfonate) imidazolium hydrosulfate ([(CH2)3SO3H-HIM]HSO4) on silica-gel using tetraethoxysilane (TEOS) as silica source in this study. The properties of the samples were characterized by FT-IR, SEM and TG/DSC. The results suggested that [(CH2)3SO3H-HIM]HSO4 had been successfully immobilized on the surface of silica-gel and the immobilized ionic liquid catalyst SG-[(CH2)3SO 3H-HIM]HSO4 had good thermal stability. The original smooth surface of silica-gel was covered with [(CH2) 3SO3H-HIM]HSO4 and a rough surface of SG-[(CH2)3SO3H-HIM]HSO4 was formed, but the size of particles had no obvious change. Moreover, SG-[(CH 2)3SO3H-HIM]HSO4 exhibited high catalytic activity for a series of acetalization and could be recovered easily. After reused for 10 times in the synthesis of benzaldehyde ethanediol acetal, the catalyst could still give satisfactory catalytic activity.
- Miao, Jinmei,Wan, Hui,Shao, Yanbing,Guan, Guofeng,Xu, Bin
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- Sequential Suzuki-Miyaura Coupling/Lewis Acid-Catalyzed Cyclization: An Entry to Functionalized Cycloalkane-Fused Naphthalenes
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Functionalized angular cycloalkane-fused naphthalenes were prepared using a two-step process involving a Pd-catalyzed Suzuki-Miyaura coupling of aryl pinacol boronates and vinyl triflates followed by a boron trifluoride etherate-catalyzed cycloaromatization.
- Mahecha-Mahecha, Camilo,Lecornué, Frédéric,Akinari, Sumita,Charote, Thomas,Gamba-Sánchez, Diego,Ohwada, Tomohiko,Thibaudeau, Sébastien
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p. 6267 - 6271
(2020/09/02)
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- Tropylium salts as efficient organic Lewis acid catalysts for acetalization and transacetalization reactions in batch and flow
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Acetalization reactions play significant roles in the synthetically important masking chemistry of carbonyl compounds. Herein we demonstrate for the first time that tropylium salts can act as organic Lewis acid catalysts to facilitate acetalization and transacetalization reactions of a wide range of aldehyde substrates. This metal-free method works efficiently in both batch and flow conditions, prompting further future applications of tropylium organocatalysts in green synthesis.
- Lyons,Crocker,Enders,Nguyen
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supporting information
p. 3993 - 3996
(2017/09/08)
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- Palladium-Catalyzed Aerobic Synthesis of Terminal Acetals from Vinylarenes Assisted by π-Acceptor Ligands
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Terminal acetals were synthesized from various vinylarenes and 1,2- or 1,3-diols using a simple PdCl2(MeCN)2/methoxy-p-benzoquinone (MeOBQ)/CuCl catalyst system and 1 atm of O2 under mild reaction conditions by the anti-Markovnikov nucleophilic attack of an oxygen nucleophile on the coordinated vinylarenes. Cyclic α,β-unsaturated carbonyl compounds such as MeOBQ and N-phenylmaleimide were especially effective as additives to afford higher yields of the desired terminal acetals. Kinetic experiments indicated that MeOBQ operates as a π-acceptor ligand for Pd to accelerate the reaction and that the dissociation of a chloride ion from Pd precedes the rate-determining step.
- Matsumura, Satoko,Sato, Ruriko,Nakaoka, Sonoe,Yokotani, Wakana,Murakami, Yuka,Kataoka, Yasutaka,Ura, Yasuyuki
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p. 751 - 757
(2017/03/13)
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- Visible-light-induced acetalization of aldehydes with alcohols
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In this work, we have achieved a simple and general method for acetalization of aldehydes by means of a photochemical reaction under low-energy visible light irradiation. A broad range of aromatic, heteroaromatic, and aliphatic aldehydes have been protected under neutral conditions in good to excellent yields using a catalytic amount of Eosin Y as the photocatalyst. Our visible light mediated acetalization strategies are successful for more challenging acid-sensitive aldehydes and sterically hindered aldehydes. Notably, this protocol is chemoselective to aldehydes, while ketones remain intact.
- Yi, Hong,Niu, Linbin,Wang, Shengchun,Liu, Tianyi,Singh, Atul K.,Lei, Aiwen
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supporting information
p. 122 - 125
(2017/11/27)
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- Combination of NH2OH·HCl and NaIO4: an effective reagent for molecular iodine-free regioselective 1,2-difunctionalization of olefins and easy access of terminal acetals
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We have demonstrated a new application of our oxidizing reagent, a combination of NH2OH·HCl and NaIO4, in the first generalized regioselective 1,2-difunctionalization of olefins. It is a general method for the preparation of β-iodo-β′-hydroxy ethers, β-iodo ethers, β-iodohydrin, and β-iodo acetoxy compounds using different reaction media. The reactions are highly regioselective, always affording Markovnikov's type addition products. The methodology is also applicable for the easy access of terminal acetals. Molecular iodine-free synthesis, room temperature reaction conditions, high yields, use of less expensive reagents, mild reaction conditions, broad applicability of nucleophiles, and applicability for gram-scale synthesis are the notable advantages of this present protocol.
- Chakraborty, Nirnita,Santra, Sougata,Kundu, Shrishnu Kumar,Hajra, Alakananda,Zyryanov, Grigory V.,Majee, Adinath
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p. 56780 - 56788
(2015/07/15)
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- Aromatic Monomers by in Situ Conversion of Reactive Intermediates in the Acid-Catalyzed Depolymerization of Lignin
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Conversion of lignin into well-defined aromatic chemicals is a highly attractive goal but is often hampered by recondensation of the formed fragments, especially in acidolysis. Here, we describe new strategies that markedly suppress such undesired pathways to result in diverse aromatic compounds previously not systematically targeted from lignin. Model studies established that a catalytic amount of triflic acid is very effective in cleaving the β-O-4 linkage, most abundant in lignin. An aldehyde product was identified as the main cause of side reactions under cleavage conditions. Capturing this unstable compound by reaction with diols and by in situ catalytic hydrogenation or decarbonylation lead to three distinct groups of aromatic compounds in high yields acetals, ethanol and ethyl aromatics, and methyl aromatics. Notably, the same product groups were obtained when these approaches were successfully extended to lignin. In addition, the formation of higher molecular weight side products was markedly suppressed, indicating that the aldehyde intermediates play a significant role in these processes. The described strategy has the potential to be generally applicable for the production of interesting aromatic compounds from lignin.
- Deuss, Peter J.,Scott, Martin,Tran, Fanny,Westwood, Nicholas J.,De Vries, Johannes G.,Barta, Katalin
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supporting information
p. 7456 - 7467
(2015/06/30)
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- Synthesis of sulfonic acid-functionalized MIL-101 for acetalization of aldehydes with diols
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A metal-organic framework (MOF) MIL-101 bearing sulfonic acid groups (SO3H-MIL-101), was prepared through one-pot hydrothermal synthesis strategy. This MOF was systemically characterized via XRD, N2 adsorption, acid-base titration, XPS, FT-IR techniques, and elemental analysis, and then used as a heterogeneous catalyst for liquid-phase acetalizations of various aldehydes with diols. The obtained SO3H-MIL-101 shows high catalytic activity in the acetalizations due to the high utilization efficiency of its functionalized acid sites. Additionally, this catalyst can be easily recovered and reused five times in succession without significant loss of catalytic activity.
- Jin, Yan,Shi, Jing,Zhang, Fumin,Zhong, Yijun,Zhu, Weidong
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p. 167 - 171
(2014/01/17)
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- Iodine-catalyzed tandem synthesis of terminal acetals and glycol mono esters from olefins
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A new metal-free protocol is described for the synthesis of terminal acetals by tandem oxidative rearrangement of olefins using oxone as an oxidant in the presence of iodine. Moreover, a one-pot procedure for the preparation of glycol mono esters from olefins is also presented for the first time using the same reagent system. The Royal Society of Chemistry 2013.
- Kumar, Macharla Arun,Swamy, Peraka,Naresh, Mameda,Reddy, Marri Mahender,Rohitha, Chozhiyath Nappunni,Prabhakar, Sripadi,Sarma, Akella Venkata Subrahmanya,Kumar, Joseph Richard Prem,Narender, Nama
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supporting information
p. 1711 - 1713
(2013/03/14)
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- Facile aldolization catalyzed by ionic liquid [4-sulfbmpyrazine][BF 4]
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The acidic functionalized ionic liquid 1-(4-sulfonic group)butyl-3- methylpyrazine tetrafluoroborate (abbreviated as [4-sulfbmpyrazine][BF 4]) was employed as the catalyst of the condensation of aromatic aldehyde and diols. The optimized condition was as follows: aromatic aldehyde (0.20 mol), diols (0.30 mol) and [4-sulfbmpyrazine][BF4] (0.60 g) were refluxed in cyclohexane (10.00 mL) for 1 h. A series of aromatic aldehydes were studied and afforded the corresponding acetals products with good yields which were from 70.3 to 96.9 %. The ionic liquid catalyst could be recycled for four times without significant loss of catalyst reactivity.
- Zou, Jianzhong,Yi, Fengping,Zhang, Lirong,Wang, Zhen
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p. 6643 - 6646
(2013/07/26)
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- A generalized approach for iron catalyzed chemo- and regioselective formation of anti-Markovnikov acetals from styrene derivatives
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Fe(BF4)2·6H2O in the presence of pyridine-2,6-dicarboxylic acid and PhI(OAc)2 can efficiently catalyze the formation of chemoselective dialkyl acetals from styrene derivatives with anti-Markovnikov regioselectivity in good to high yields under mild and benign reaction conditions.
- Chowdhury, Abhishek Dutta,Lahiri, Goutam Kumar
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supporting information; experimental part
p. 3448 - 3450
(2012/05/20)
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- Palladium-catalyzed synthesis of terminal acetals via highly selective anti-Markovnikov nucleophilic attack of pinacol on vinylarenes, allyl ethers, and 1,5-dienes
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A palladium-catalyzed reaction of vinylarenes, allyl ethers, and 1,5-dienes with pinacol proceeded via a selective anti-Markovnikov nucleophilic attack to afford corresponding terminal acetals as major products. The bulkiness of pinacol was found to be critical in controlling the regioselectivity. The Royal Society of Chemistry 2012.
- Yamamoto, Mayumi,Nakaoka, Sonoe,Ura, Yasuyuki,Kataoka, Yasutaka
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supporting information; experimental part
p. 1165 - 1167
(2012/02/04)
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- o-benzenedisulfonimide as reusable bronsted acid catalyst for acid-catalyzed organic reactions
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Acid-catalyzed organic reactions, such as etherification, esterification, acetal synthesis, cleavage, and interconversion, and pinacol rearrangement were carried out in the presence of catalytic amounts of o-benzenedisulfonimide as Bronsted acid catalyst; the conditions were mild and selective. The catalyst was easily recovered and purified, ready to be used in further reactions, with economic and ecological advantages. Georg Thieme Verlag Stuttgart.
- Barbero, Margherita,Cadamuro, Silvano,Dughera, Stefano,Venturello, Paolo
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p. 1379 - 1388
(2008/12/21)
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- Rhodium-catalyzed addition of arylboronic acids to 2-methylene-1,3-dithiane monoxide
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Treatment of 2-methylene-1,3-dithiane 1-oxide with arylboronic acid under rhodium catalysis in aqueous dioxane at 25°C provided the corresponding adduct, which is a useful 2-aryl-alkanal equivalent. Georg Thieme Verlag Stuttgart.
- Yoshida, Suguru,Yorimitsu, Hideki,Oshima, Koichiro
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p. 1622 - 1624
(2008/02/05)
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- Direct synthesis of protected arylacetaldehydes by tetrakis(phosphane)- palladium-catalyzed arylation of ethyleneglycol vinyl ether
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A range of aryl bromides undergo Heck reaction with ethylene glycol vinyl ether, in the presence of [PdCl(C3H5)]2/ cis,cis,cis-1,2,3,4-tetrakis[(diphenylphosphanyl)methyl]cyclopentane as catalyst, to give regioselectively protected arylacetaldehydes in good yields. The β-arylation products were obtained in with 93-100 % selectivity with electron-poor aryl bromides or heteroaryl bromides. Furthermore, this catalyst can be used at low loading, even for reactions with sterically hindered aryl bromides. The aryl vinyl ether intermediates undergo subsequent ketalisation to give the corresponding 2-benzyl-1,3-dioxolane derivatives. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Kondolff, Isabelle,Doucet, Henri,Santelli, Maurice
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p. 765 - 774
(2007/10/03)
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- Direct synthesis of protected arylacetaldehydes by palladium- tetraphosphine-catalyzed arylation of ethyleneglycol vinylether
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Through the use of [PdCl(C3H5)]2/cis,cis, cis-1,2,3,4-tetrakis(diphenylphosphinomethyl) cyclopentane as a catalyst, a range of aryl bromides undergo Heck reaction with ethyleneglycol vinylether to give regioselectively protected arylacetaldehydes in good yields. The β-arylation products were obtained in the range 93-98% selectivity with electron-poor aryl bromides. Furthermore, this catalyst can be used at low loading, even for reactions of sterically hindered aryl bromides. The arylvinyl ethers intermediates undergo subsequent ketalization to give the corresponding 2-benzyl-1,3-dioxolane derivatives.
- Kondolff, Isabelle,Doucet, Henri,Santelli, Maurice
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p. 1561 - 1564
(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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- Non-acid catalytic acetalisation of aldehydes with diols in ionic liquids
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The acetalisation of aldehydes with diols to corresponding 1,3-dioxolanes has been accomplished using ionic liquids as catalyst and reaction media. In the reaction process the removal of water produced and other catalysts were not necessary. High conversion and good selectivity were obtained when using HMImBF4, which could be easily recycled and reused.
- Zhang, Fan,Xu, Dan-Qian,Luo, Shu-Ping,Liu, Bao-You,Du, Xiao-Hua,Xu, Zhen-Yuan
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p. 773 - 774
(2007/10/03)
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- Direct Synthesis of Cyclic Ketals of Acetophenones by Palladium-Catalyzed Arylation of Hydroxyalkyl Vinyl Ethers
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Reaction of 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, or di(ethylene glycol) vinyl ether with aryl triflates, aryl bromides, or iodobenzene in presence of a catalytical amount of palladium acetate and the bidentate ligand DPPP provides a direct entry to cyclic ketals of acetophenones.It is postulated that the reaction proceeds via an initial α-arylation of the vinyl ethers to give labile aryl vinyl ether intermediates, which undergo subsequent ketalization in presence of protons in the reaction media.The method merits attention due to the simplicity of the experimental procedure and the possibility of selective ketal formation in the presence of an additional carbonyl group.
- Larhed, Mats,Hallberg, Anders
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p. 7858 - 7862
(2007/10/03)
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- Photosensitized (electron transfer) carbon-carbon bond cleavage of radical cations: the 2-phenylethyl ether and acetal systems
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The scope of the photosensitized (electron transfer) carbon-carbon bond cleavage involving radical cations has been defined for 2-phenylethyl ethers and acetals.The thresholds for reactivity of the monophenylethyl and gem-diphenylethyl derivatives are compared.While the radical cation of methyl 2,2-diphenylethyl ether (7) cleaves to give ultimately diphenylmethane (2) and dimethoxymethane (8), the radical cation of methyl 2-phenylethyl ether (9) was stable under these conditions.In contrast to the lack of reactivity of the radical cation of 9, the radical cations of methyl 2-phenyl-2-propyl ether (11), methyl 2-phenylcyclopentyl ether (13), and 2-phenylmethyl-1,3-dioxolane (16) cleave.Cleavage in the monophenylethyl series is limited to formation of a carbocation at least as stable as the secondary α-oxyalkyl or di-α-oxyalkyl.The basis for predicting this type of reactivity of radical cations is defined.The rate of carbon-carbon bond cleavage is increased the oxidation potential of the molecule, by decreasing the carbon-carbon bond strength, and (or) by decreasing the oxidation potential of that fragment that will become the carbocation.The results obtained from the reactions of 2-diphenylmethyl-1,3-dioxolane (14) and 2-phenylmethyl-1,3-dioxolane (16) cast doubt on the published oxidation potential for the 1,3-dioxolan-2-yl radical.Key words: photochemistry, radical cation, electron transfer, bond cleavage, radical.
- Arnold, Donald R.,Lamont, Laurie J.
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p. 2119 - 2127
(2007/10/02)
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- Catalyst and method for isomerization
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A catalyst for isomerization consisting essentially of a salt or complex salt represented by the formula: where M is a metal of Group IB, IIA, IIB or VIII of the periodic table, L is a ligand, Y is a conjugated base of a Bronsted acid, m is 0, 1, 2, 3 or 4 and n is 1, 2 or 3.
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