- A green process for the oxidative lactonization of 1,2-benzenedimethanol by tungstic acid with aqueous H2O2
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A new economic and green route to synthesize phthalide from 1,2-benzenedimethanol using aqueous hydrogen peroxide as the oxidant and tungstic acid as the catalyst under organic solvent-free conditions is presented. This process proceeds with advantages from the viewpoint of green chemistry, in which the only by-product of H2O2 is water and the catalyst can also be easily recovered. The desired product with high purity and good yield can be conveniently obtained when cooled after reaction.
- Zhu, Quan-Jing,Dai, Wei-Lin,Fan, Kang-Nian
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- Catalytic reductive deoxygenation of esters to ethers driven by hydrosilane activation through non-covalent interactions with a fluorinated borate salt
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We report the catalytic and transition metal-free reductive deoxygenation of esters to ethers through the use of a hydrosilane and a fluorinated borate BArF salt as a catalyst. Experimental and theoretical studies support the role of noncovalent interactions between the fluorinated catalyst, the hydrosilane and the ester substrate in the reaction mechanism.
- Agbossou-Niedercorn, Francine,Dixit, Ruchi,Merle, Nicolas,Michon, Christophe,Rysak, Vincent,Trivelli, Xavier,Vanka, Kumar
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p. 4586 - 4592
(2020/08/14)
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- One-Pot Synthesis of O-Heterocycles or Aryl Ketones Using an InCl3/Et3SiH System by Switching the Solvent
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An efficient one-pot synthesis of O-heterocycles or aryl ketones has been achieved using Et3SiH in the presence of InCl3 via a sequential ionic hydrogenation reaction by switching the solvent. This methodology can be used to construct C-O bonds and to prepare conjugate reduction products, including chromans, tetrahydrofurans, tetrahydropyrans, dihydroisobenzofurans, dihydrochalcones, and 1,4-diones in a facile manner. In addition, a novel plausible mechanism involving a conjugate reduction and a tandem reductive cyclization was verified by experimental investigations.
- Jia, Wenqiang,Xi, Qiumu,Liu, Tianqi,Yang, Minjian,Chen, Yonghui,Yin, Dali,Wang, Xiaojian
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p. 5141 - 5149
(2019/05/10)
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- An ether compound of green high-efficient synthetic method (by machine translation)
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The invention discloses an ether compound of green high-efficient synthetic method, energy-saving environmental protection, comprising: mild reaction system, uses aldehyde, silane as the starting material, under the action of the silver salt in a price, for in solvent-free conditions, through reducing the - coupling - cheng mi reaction, realization of high efficiency alcohol of preparation. Synthesis method of the invention has the advantages of low dosage of catalyst, solvent-free, conversion and high yield, the reaction time is short, safe and stable, easy to operate, the product only distillation purification without any additional organic solvent, the whole range of green, environmental protection, high efficiency and the like, can overcome the defects of the prior art, it has very good industrial application value. (by machine translation)
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Paragraph 0051
(2018/07/07)
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- Cyclic ether synthesis from diols using trimethyl phosphate
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Cyclic ethers have been effectively synthesized via the intramolecular cyclization of diols using trimethyl phosphate and NaH. The present cyclization could proceed at room temperature to produce 5-7 membered cyclic ethers in good to excellent yields. Substrates possessing a chiral secondary hydroxy group were transformed into the corresponding chiral cyclic ethers along with the retention of their stereochemistries.
- Asai, Shota,Kato, Maho,Monguchi, Yasunari,Sajiki, Hironao,Sawama, Yoshinari
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supporting information
p. 4787 - 4790
(2017/07/06)
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- Lewis acid promoted ruthenium(II)-catalyzed etherifications by selective hydrogenation of carboxylic acids/esters
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Ethers are of fundamental importance in organic chemistry and they are an integral part of valuable flavors, fragrances, and numerous bioactive compounds. In general, the reduction of esters constitutes the most straightforward preparation of ethers. Unfortunately, this transformation requires large amounts of metal hydrides. Presented herein is a bifunctional catalyst system, consisting of Ru/phosphine complex and aluminum triflate, which allows selective synthesis of ethers by hydrogenation of esters or carboxylic acids. Different lactones were reduced in good yields to the desired products. Even challenging aromatic and aliphatic esters were reduced to the desired products. Notably, the in situ formed catalyst can be reused several times without any significant loss of activity. An assist from Al: A bifunctional catalyst system consisting of a Ru/phosphine complex and aluminum triflate allows selective hydrogenation of esters to ethers. A variety of lactones were reduced to the desired products in good yields. The catalyst further provides a general method for the reduction of linear esters and reductive etherification of carboxylic acids with alcohols.
- Li, Yuehui,Topf, Christoph,Cui, Xinjiang,Junge, Kathrin,Beller, Matthias
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supporting information
p. 5196 - 5200
(2015/04/27)
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- Synthesis of five- and six-membered heterocycles by dimethyl carbonate with catalytic amounts of nitrogen bicyclic bases
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A catalytic amount of a nitrogen bicyclic base, i.e., DABCO, DBU or TBD, is effective for the one-pot synthesis of heterocycles from 1,4-, 1,5-diols and 1,4-bifunctional compounds via dimethyl carbonate chemistry under neat conditions. Nitrogen bicyclic bases that were previously shown to have enhanced the reactivity of DMC in methoxycarbonylation reaction by a BAc2 mechanism are herein used for the first time as efficient catalysts for cyclization reactions encompassing both BAc2 and BAl2 pathways. This synthesis procedure was also applied to a large scale synthesis of cyclic sugars, isosorbide and isomannide, starting from d-sorbitol and d-mannitol, respectively. The resulting anhydro sugar alcohols were obtained as pure crystalline compounds that did not require any further purification or crystallization. This journal is
- Aricò,Evaristo,Tundo
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p. A1176 - A1185
(2015/03/04)
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- Selective catalytic synthesis of unsymmetrical ethers from the dehydrative etherification of two different alcohols
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The cationic ruthenium-hydride complex [(C6H6)(PCy3)(CO)RuH]+BF4- catalyzes selective etherification of two different alcohols to form unsymmetrically substituted ethers. The catalytic method exhibits a broad substrate scope while tolerating a range of heteroatom functional groups in forming unsymmetrical ethers, and it is successfully used to directly synthesize a number of highly functionalized chiral nonracemic ethers.
- Kim, Junghwa,Lee, Dong-Hwan,Kalutharage, Nishantha,Yi, Chae S.
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p. 3881 - 3885
(2015/01/16)
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- Synthesis of ethers from esters via Fe-catalyzed hydrosilylation
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Triiron dodecacarbonyl allows for the selective reduction of esters into the corresponding ethers. This protocol has a wide substrate scope. In addition, cholesteryl pelarogonate has been reduced under the reaction conditions with an excellent yield.
- Das, Shoubhik,Li, Yuehui,Junge, Kathrin,Beller, Matthias
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supporting information
p. 10742 - 10744
(2013/01/15)
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- Synthesis of five-membered cyclic ethers by reaction of 1,4-diols with dimethyl carbonate
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The reaction of 1,4-diols with dimethyl carbonate in the presence of a base led to selective and high-yielding syntheses of related five-membered cyclic ethers. This synthetic pathway has the potential for a wide range of applications. Distinctive cyclic ethers and industrially relevant compounds were synthesized in quantitative yield. The reaction mechanism for the cyclization was investigated. Notably, the chirality of the starting material was maintained. DFT calculations indicated that the formation of five-membered cyclic ethers was energetically the most favorable pathway. Typically, the selectivity exhibited by these systems could be rationalized on the basis of hard-soft acid-base theory. Such principles were applicable as far as computed energy barriers were concerned, but in practice cyclization reactions were shown to be entropically driven. Copyright
- Aricó, Fabio,Tundo, Pietro,Maranzana, Andrea,Tonachini, Glauco
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experimental part
p. 1578 - 1586
(2012/10/07)
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- A facile synthesis of 5,6-dihydro-4H-pyrrolo[3,4-d]thiazole and other pyrrolidine-fused aromatic ring systems via one-step cyclization from diols
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A facile synthetic method of 5,6-dihydro-4H-pyrrolo[3,4-d]thiazole, which is a subunit of a potent factor Xa (fXa) inhibitor was developed. This new approach employs one-step cyclization from a diol and can be applied to the syntheses of other pyrrolidine-fused aromatic ring sytems.
- Yoshikawa, Kenji,Nagata, Tsutomu,Yoshino, Toshiharu,Nakamoto, Yumi,Haginoya, Noriyasu,Muto, Ryo,Mochizuki, Akiyoshi,Kanno, Hideyuki,Ohta, Toshiharu
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experimental part
p. 1711 - 1720
(2012/09/07)
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- Intramolecular condensation of 1,2-C6H4(CH 2RH)2 (R = O, S, and NH) to yield heterocyclic compounds over halide-cluster catalysts
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1,2-Benzenedimethanol was reacted under a helium stream in the presence of [(Nb6Cl12)Cl2(H2O) 4]·4H2O supported on silica gel. When the temperature was raised above 200 °C, catalytic activity of the cluster for cyclization appeared, yielding 1,3-dihydroisobenzofuran in 91% selectivity at 350 °C. The corresponding halide clusters of tantalum and tungsten also catalyzed the reaction. cis-1,2-Cyclohexanedimethanol and 1,4-butanediol exclusively produced the corresponding furans. 1,2-Benzenedimethanamine and 1,2-benzenedimethanethiol selectively afforded isoindoline and 1,3-dihydrobenzo[c]thiophene, respectively.
- Nagashima, Sayoko,Kamiguchi, Satoshi,Kudo, Kentaro,Sasaki, Tomoaki,Chihara, Teiji
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scheme or table
p. 78 - 80
(2011/05/07)
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- FLUOROBORON COMPOUND HAVING AROMATIC RING OR SALT THEREOF, AND PROCESS FOR PRODUCTION OF COMPOUND HAVING CYCLIC ETHER-FUSED AROMATIC RING BY USING THE SAME
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Provided is a fluoroboron compound which is highly safe and stable and is capable of forming a cyclic ether-fused ring by the intramolecular alkoxymethylation reaction, or a salt thereof. The compound can be synthesized by the intramolecular alkoxymethylation reaction of a fluoroboron compound represented by the formula (I) or a salt thereof in the presence of a metal catalyst. (wherein the moiety represented by the formula represents an aromatic ring; L represents a substituent such as a halogen atom; R represents a substituted or unsubstituted alkylene group having 1 or 2 carbon atoms; and M represents an alkali metal cation or the like, with the proviso that L and -R-OCH2BF3M are respectively located on contiguous carbon atoms on the aromatic ring, or in the case of a fused aromatic ring, on two carbon atoms adjacent to one carbon at the fused position).
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Page/Page column 13
(2009/06/27)
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- A one-pot tandem oxidation-reduction protocol for the synthesis of cyclic ethers from their diols
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A novel and an efficient one-pot cyclization method for the preparation of cyclic ethers from their diols via a tandem oxidation-reduction protocol using a cocktail of MnO2/Et3SiH/CF3COOH is reported.
- Panda, Biswajit,Sarkar, Tarun K.
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scheme or table
p. 6701 - 6703
(2009/04/07)
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- New formation of 4,5,6,7-tetrahydroisoindoles
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The high-yield syntheses of 4,5,6,7-tetrahydro-isoindoles from N-substituted isoindolines under palladium catalyzed hydrogenation conditions are reported. Mechanistic study with deuterated and saturated substrates show extensive H/D exchange and the essence of aromaticity in this transformation.
- Hou, Duen-Ren,Hsieh, Yih-Dar,Hsieh, Yi-Wei
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p. 5927 - 5929
(2007/10/03)
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- Process for producing isochromanones and intermediates thereof
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(1) Methods for producing isochromanone compounds from o-xylene compounds as starting compounds through α-halogeno-o-xylene derivatives, α-cyano-o-xylene derivatives, and α-halogeno-α′-cyano-o-xylene derivatives, and (2) methods for producing isochromanone compounds from o-xylene compounds as starting compounds through α,α′-dihalogeno-o-xylene derivatives, α,α′-dihydroxy-o-xylene derivatives, α-halogeno-α′-hydroxy-o-xylene derivatives and α-cyano-α′-hydroxy-o-xylene derivatives, and methods for producing these intermediate compounds.
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- Solvent-free synthesis of cyclic ethers from dihalo compounds in the presence of alumina
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Facile synthesis of cyclic ethers from dihalo compounds on alumina has been accomplished in good yields. The reactions proceeded smoothly both in refluxing hexane and by microwave irradiation in the absence of solvent. In addition to being an organic-solvent-free operation, it also entails a short reaction time.
- Mihara, Masatoshi,Ishino, Yoshio,Minakata, Satoshi,Komatsu, Mitsuo
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p. 1526 - 1528
(2007/10/03)
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- Intramolecular Reactivity of Arylcarbenes: 2-(Alkoxymethyl)phenylcarbenes
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Both singlet and triplet states contribute to the intramolecular C-H insertion reactions of 2-(alkoxymethyl)phenylcarbenes, leading to dihydro-1H-2-benzopyrans.Competitively, oxygen ylides are generated which eventually give rise to benzocyclobutenes and dihydroisobenzofurans.The radical pair mechanism of the Stevens rearrangement is confirmed by variation of the alkyl groups and by means of chiral substrates.
- Kirmse, Wolfgang,Schnitzler, Dirk
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p. 1699 - 1702
(2007/10/02)
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- Unusual Stability of N-Methylmaleimide Cycloadducts: Characterization of Isobenzofuran Retro-Diels-Alder Reactions
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Many years ago Diels and Thiele noted the unusual stability of maleic anhydride cycloadducts and employed this feature in scavenging anthracene generated in a retro- reaction.N-methylmaleimide, although nearly identical to maleic anhydride in rates of Diels-Alder reactions, forms even more stable cycloadducts.The rate constants for the four reactions that characterize the furan/N-methylmaleimide system were measured under the conditions used by Lee and Herndon to study the furan/maleic anhydride system.Comparison of the two dienophiles indicates thatN-methylmaleimide adducts are ca. 3 kcal*mol-1 more stable than the corresponding exo- and endo-maleic anhydride adducts.Somewhat larger (ca. 4 +/- 0.5 kcal*mol-1) differences in stability were found for the cycloadducts of the much more reactive diene isobenzofuran.N-Methylmaleimide is used as a diene scavenger to obtain rate constants for retro-Diels-Alder reactions of isobenzofuran adducts with maleic anhydride and some substituted analogs.The rates of retro-Diels-Alder reactions of substituted N-methylmaleimide adducts were also determined by an alternative method.The substituents examined enhance the rates of exo retro-Diels-Alder reactions by factors of 15-40, while endo adduct retro-Diels-Alder rates are only slightly affected.Calculations were done at the MP2/6-31G*//HF/6-31G* level to compare the heats of hydrogenation of maleic anhydride and maleimide.The reduction of maleimide is calculated to be 2.5 kcal*mol-1 more exergonic, supporting the experimental observations.
- Tobia, David,Harrison, Roy,Phillips, Brian,White, Thomas L.,DiMare, Marcello,Rickborn, Bruce
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p. 6701 - 6706
(2007/10/02)
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- Reduction of Dicarboxylic Acid Anhydride with 2-Propanol over Hydrous Zirconium Oxide
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The reduction of dicarboxylic acid anhydrides with 2-propanol proceeded efficiently over hydrous zirconium oxide to give the corresponding lactones and cyclic ethers.Secondary and primary alcohols, with the exception of methanol, are able to act as hydride donors in this reduction.The reduction proceeded as nearly second order concerning the concentration of 2-propanol and minus order concerning that of acid anhydride.These results suggest that the reduction was preferred under lower concentrations of acid anhydride and higher concentrations of 2-propanol.The selectivity of lactone or ether could be changed by the reaction temperature or the molar ratio of dicarboxylic acid anhydride to alcohol.
- Takahashi, Kyoko,Shibagaki, Makoto,Matsushita, Hajime
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p. 262 - 266
(2007/10/02)
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- A new synthesis of isochromans and phtalans
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A short and efficient synthesis of isochromans and phtalans has been devised. This synthesis involves the intramolecular Friedel-Crafts cyclialkylation of oxonium species generated by reaction of MEM ethers with Lewis acids.
- Ahmar,Bloch
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p. 1417 - 1420
(2007/10/02)
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- Carbenes and the O-H Bond: Hydroxyalkyl-Substituted Arylcarbenes
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carbene (4), phenylcarbene (19), and carbene (30) have been generated by photolysis of tosylhydrazone or diazo precursors in protic solvents.These carbenes give cyclic ethers (7, 18, 33) competitively with insertion into O-H bonds of the solvent.For comparison, the analogous benzyl cations (9, 17, 31) have been generated by solvolysis or dediazoniation.The cations are more sensitive to structural variation than their carbenic counterparts: 9 does not undergo intramolecular nucleophilic substitution, in contrast to 17 and 31.These observations are explicable in terms of high barriers for rotation about aryl-cation bonds, as compared with low barriers for rotation about aryl-carbene bonds.Two major effects of the solvent (ROH) and of the base (RONa) on product formation may be distinguished: (i) protonation of the carbene (or of its precursors) in the more acidic media leads to predominantly cationic processes; (ii) deprotonation of the OH group under strongly basic conditions enhances the nucleophilicity of the oxygen, and also facilitates insertion into the α-C-H bonds of 30.
- Kirmse, Wolfgang,Kund, Klaus
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p. 2325 - 2332
(2007/10/02)
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- Catalytic hydrogenation of heterocyclic compounds. (II). Bond isomerization and hyperstability
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Bond isomerization is common during catalytic hydrogenation reactions. Recent studies have focused on examining alkenes that reduce only with great difficulty. The concept of hyperstability has been used to account for the observed non-reactivity. In this work we examine both problems and suggest an explanation to account for hyperstability.
- Johnson,Mundy
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p. 6633 - 6636
(2007/10/02)
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- Intramolecular Generation of Oxonium Ylides from Functionalized Arylcarbenes
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Arylcarbenes carrying alkoxyalkyl groups in the ortho position have been generated by flash pyrolysis and photolysis of appropriate tosylhydrazone sodium salts.In the gas phase and in a aprotic solvents, interaction of the carbenes with the lone electron pairs of oxygen competes efficiently with insertion into C-H bonds.Both five- and six-membered cyclic oxonium ylides have been generated.The ylides 23, 37, 61b, and 74 undergo 1,2 shifts of benzyl groups with ease, even if ring contraction to highly strained benzocyclobutenes is involved (23, 74).The oxonium ylides37 and 61b strongly prefer the nonconcerted Stevens rearrangement to the sigmatropic Sommelet rearrangement, in contrast to analogous ammonium ylides.Alkyl shifts occur to a very minor extent, if at all.Evidence is presented that alcohols intercept both the carbenes and the oxonium ylides.Protonation of the ylides leads to cyclic oxonium ions, which undergo nucleophilic cleavage of the C-O bonds.Acid catalyzed decomposition of the appropriate diazo compounds gives rise to six-membered, but not to five-membered, cyclic oxonium ions, thus confirming the different intramolecular reactivities of arylcarbenes and benzyl cations.The efficiency of carbene interception increases with increasing acidity of the medium, suggesting nucleophilic behavior (protonation) of the arylcarbenes.
- Kirmse, Wolfgang,Kund, Klaus
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p. 1465 - 1473
(2007/10/02)
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- Rhodium-catalysed -Cycloadditions of Acteylenes
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Wilkinson's catalyst (0.5-2 molpercent) catalyses the chemospecific -cycloaddition of hepta-1,6-diynes with monoynes to give polysubstituted benzene derivatives in moderate to good yield.The reaction is favoured by polar solvents such as ethanol and occurs at 0-78 deg C.Several examples of intramolecular -cycloadditions of triynes are described and a mechanism that accounts for the chemospecificty and observed variations in rates of reaction is discussed.
- Grigg, Ronald,Scott, Ronald,Stevenson, Paul
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p. 1357 - 1364
(2007/10/02)
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- Ionic Hydrogenation with Organosilanes under Acid-Free Conditions. Synthesis of Ethers, Alkoxysilanes, Thioethers, and Cyclic Ethers via Organosylil Iodide and Triflate Catalyzed Reductions of Carbonyl Compounds and Their Derivatives
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The general ether synthesis method based on the trialkylsilane/trialkylsilyl iodide or triflate reagent system has been extended to the syntheses of alkoxysilanes from ketones, tetrahydrofurans and tetrahydropyrans from dicarbonyl compounds, and thioethers by reductive cleavage of O-silylhemithioacetals.
- Sassaman, Mark B.,Prakash, G. K. Surya,Olah, George A.
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p. 3771 - 3780
(2007/10/02)
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- POPELLANES-LII THE REACTION OF CONJUGATED DIENIC PROPELLANES WITH SINGLET OXYGEN
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The reactions of propellanes containing one or two cyclohexadiene rings with singlet oxygen take the course of exclusive syn-attack with respect to a hetero-ring containing two CO groups.When only one or no CO group is found in the hetero ring, both syn- and anti-attack occur.The former course is interpreted in terms of secondary orbital interactions wich stabilize the transition state for syn-attack.
- Landheer, Iman,Ginsburg, David
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p. 133 - 142
(2007/10/02)
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- Small rings, 36. Attempts to Synthesize Tetramethyltetrahedrane from Alicyclic Precursors
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Synthesis as well as the thermal and photochemical behaviour of compounds with ring skeletons 1 and 3 are described.Whereas the former are accessible by standard procedures the approach to the bicyclobutane derivatives is based on the isomerization of diester 1b into valence isomer 3b which can be achieved in good yield by SiO2 or Al2O3.There are only minor differences in the cleavage of the pairs 1/3 provoked by heating or photochemical excitation.This is even true for irradiations in argon at 10 K.Under those conditions anhydrides 1a and 3a form the samecharge transfer complex 28a between tetramethylcyclobutadiene and phthalic anhydride.A direct detection of tetramethyltetrahedrane using these means is not possible.
- Maier, Guenther,Mayer, Wolfram,Freitag, Hans-Albrecht,Reisenauer, Hans Peter,Askani, Rainer
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p. 3935 - 3958
(2007/10/02)
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- Direct ortho-Metalation of Benzyl Alcohols. A Novel Method of Preparing ortho-Substituted Benzyl Alcohols
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Benzyl alcohol and other phenylcarbinols (8a - 11a), including α-tetralol (12a), are doubly deprotonated by excess n-butyllithium/TMEDA in pentane to give lithium ortho-lithioalkoxides (2, 8b - 12b).Alkylations (-> 3a - d, table 1), reactions with heteroelectrophiles (-> 3e - k, table 2) and with carbonyl compounds (-> 6, 13 - 17, tables 3 and 4), as well as subsequent reactions of the primary adducts (-> phthalanes 7, table 3) furnish a large variety of ortho-substituted benzyl alcohol derivatives.The scope and limitations of the dilithioorganyls (sections B and C), their mode of formation (section A), and attempts to doubly metalate 2-phenylethanol are discussed.
- Meyer, Norbert,Seebach, Dieter
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p. 1304 - 1319
(2007/10/02)
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