- 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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- New method for the synthesis of benzyl alkyl ethers mediated by FeSO 4
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The synthesis of benzyl alkyl ethers from benzyl bromides and alcohols using FeSO4 as a recoverable and reusable mediator has been described without use of base and cosolvent under mild conditions.
- Joshi, Girdhar,Adimurthy, Subbarayappa
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experimental part
p. 720 - 728
(2011/03/22)
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- Polymer having antireflective properties, hardmask composition including the same, process for forming a patterned material layer, and associated device
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An antireflective hardmask composition includes an organic solvent, and at least one polymer represented by Formulae A, B or C: In Formulae A and B, the fluorene group is unsubstituted or substituted, in Formula C, the naphthalene group is unsubstituted or substituted, n is at least 1 and is less than about 750, m is at least 1, and m+n is less than about 750, G is an aromatic ring-containing group having an alkoxy group, and R1 is methylene or includes a non-fluorene-containing aryl linking group.
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- Efficient synthesis of cryptophycin-52 and novel para- Alkoxymethyl unit A analogues
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Cryptophycins are a family of highly cytotoxic, cyclic depsipeptides. They display antitumour activity that is largely maintained for multidrug-resistant tumour cells. Cryptophycins are composed of four building blocks (units A-D) that correspond to the respective amino and hydroxy acids. A new synthetic route to unit A allows the selective generation of all four stereogenic centres in a short, efficient and reliable synthesis and con-tributes to an easier and faster synthesis of cryptophycins. The first two stereogenic centres are introduced by a catalytic asymmetric dihydroxylation, whereas the remaining two stereogenic centres are introduced with substrate control of diastereoselectivity. The stereogenic diol function also serves as the epoxide precursor. The approach was used to synthesise the native unit A building block as well as three paraalkoxymethyl analogues from which cryptophycin-52 and three analogous cryptophycins were prepared. Macrocyclisation of the seco-depsipeptides was based on ring-closing metathesis.
- Eissler, Stefan,Bogner, Tobias,Nahrwold, Markus,Sewald, Norbert
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scheme or table
p. 11273 - 11287
(2010/04/28)
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- PROCESS
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A process for the alkoxyalkylation of an unsubstituted aromatic substrate or a substituted aromatic substrate, said substitution being via a carbon-carbon bond, said process comprising reacting the aromatic substrate with a dialkoxyalkane in the presence of a catalyst.
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Page/Page column 15
(2008/06/13)
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- Synthetic Study of Selective Benzylic Oxidation
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Oxidation of bisbenzyl ethers was studied using 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ). Compared to other benzylic oxidations such as Kornblum type reaction of benzyl bromides or MnO2 oxidation of benzyl alcohols, DDQ oxidation offered advantages of being mild and highly selective to provide monoaldehyde products. We have explored factors which influence the course of the reaction and exemplified the synthetic value of the approach by preparing a number of aromatic intermediates (7-8, 15-25).
- Wang, Wuyi,Li, Tiechao,Attardo, Giorgio
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p. 6598 - 6602
(2007/10/03)
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- A convenient synthesis of methyl- and isopropyl-benzyl ethers using silver(II) oxide as reagent
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Substituted bromomethyl- and chloromethylbenzenes and bis(bromomethyl) benzenes were directly converted, in high yields, to the corresponding methyl- and isopropyl-benzyl ethers by treatment with silver(II) oxide in methanol or isopropanol.
- Ortiz,Walls,Yuste,Barrios,Sanchez-Obregon,Pinelo
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p. 749 - 756
(2007/10/02)
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- Convenient Synthesis of Some Functionalized Dewar Benzenes and Effect of Chlorine Substitution on the Rates of Their Aromatization
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1,4-Bis(hydroxymethyl) Dewar benzenes were prepared in five steps from dimethyl acetylenedicarboxylate in ca. 10percent overall yield and rates of their aromatization were measured: dichloro substitution at both the 2,5- and 2,6-positions led to substantial deceleration of the isomerization.
- Tsuji, Takashi,Watanabe, Harumi,Tanaka, Jun,Inada, Mari,Nishida, Shinya
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p. 1193 - 1196
(2007/10/02)
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- Anodic Oxidation of Xylenes. Electrochemical Obtention of Cyclohexa-1,4-diene Derivatives
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cis- and trans-3,6-dimethoxy-3,6-dimethylcyclohexa-1,4-dienes obtained by methoxylation of p-xylene were completely separated.The unequivocal structure of the trans isomer was assigned by X-ray diffraction, and the cis:trans ratio is satisfactorily explained by an EECrCp mechanism.When the substrates were p- and o-xylene, the nuclear-addition products were obtained in a two-electron process, but when the substrate was m-xylene, the major muclear-addition product was obtained in a four-electron process.
- Barba, Isidoro,Alonso, Francisco,Florencio, Feliciana
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p. 4365 - 4367
(2007/10/02)
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- Methylation of Alcohols, Phenols, and Carboxylic Acids, and Selective Monomethylation of Diols and Dicarboxylic Acids with Dimethyl Sulfate by Use of Alumina
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Alcohols in cyclohexane give their methyl ethers in high yields by the use of a combination of dimethyl sulfate and alumina.Some diols and dicarboxylic acids adsorbed on alumina react with dimethyl sulfate and produce the corresponding monomethyl ethers and esters in high selectivities.
- Ogawa, Haruo,Ichimura, Youko,Chihara, Teiji,Teratani, Shousuke,Taya, Kazuo
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p. 2481 - 2484
(2007/10/02)
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