- Photoinduced Diverse Reactivity of Diazo Compounds with Nitrosoarenes
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A diverse reactivity of diazo compounds with nitrosoarene in an oxygen-transfer process and a formal [2 + 2] cycloaddition is reported. Nitosoarene has been exploited as a mild oxygen source to oxidize an in situ generated carbene intermediate under visible-light irradiation. UV-light-mediated in situ generated ketenes react with nitosoarenes to deliver oxazetidine derivatives. These operationally simple processes exemplify a transition-metal-free and catalyst-free protocol to give structurally diverse α-ketoesters or oxazetidines.
- Roy, Sourav,Kumar, Gourav,Chatterjee, Indranil
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p. 6709 - 6713
(2021/09/08)
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- Preparation method of alpha-ketoester compound
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The invention discloses a preparation method of an alpha-ketone ester compound. The method specifically comprises the following operation steps: adding raw materials alpha-diazo ester and an organic photocatalyst into a reaction flask, then adding an organic solvent, and reacting for 2-12 hours in air at room temperature under the irradiation of a visible light lamp; after the reaction is monitored by thin-layer chromatography (TLC), stopping the reaction, and extracting a reaction solution by using ethyl acetate; concentrating the extracting solution under reduced pressure to obtain a crude product, and performing column chromatography separation on the crude product to obtain the alpha-diazonium ester compound. According to the preparation method, clean visible light is used as reaction energy, cheap organic dye is used as a photocatalyst, air is used as a green oxidizing agent and an oxygen source, and the preparation method has the advantages of simplicity and convenience in operation, no metal residue and mild reaction conditions.
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Paragraph 0138-0141
(2021/04/21)
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- Copper(I)-catalyzed aerobic oxidation of α-diazoesters
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A practical Cu-catalyzed oxidation of α-diazoesters to α-ketoesters using molecular oxygen as an oxidant has been developed. Both electron-poor and electron-rich aryl α-diazoesters are suitable substrates and provide the α-ketoesters in good yields. In this oxidative system, α-diazo-β-ketoesters are also compatible as substrates but unexpectedly furnish α-ketoesters via C-C bond cleavage, rather than the vicinal tricarbonyl products.
- Xu, Changming,Bai, Lei,Wang, Yongchang
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p. 12579 - 12584
(2020/11/09)
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- Green preparation method of aryl [alpha]-keto ester compound
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The invention discloses a green preparation method of an aryl [alpha]-keto ester compound. The method comprises the specific steps that an [alpha]-diazo compound serves as a reaction raw material, copper sulfate serves as a catalyst, water serves as a solvent, a target product aryl [alpha]-keto ester compound is prepared through a reaction at the temperature of 60 DEG C, the structural general formula of the [alpha]-diazo compound is shown in the specification, and the structural general formula of the correspondingly prepared target product aryl [alpha]-keto ester compound is shown in the specification. The method for synthesizing the target product aryl [alpha]-keto ester compound by catalyzing the [alpha]-diazo compound derivative with copper sulfate has the advantages that the reactioncondition is green and mild, the catalyst is cheap and easy to obtain, the operation is simple and convenient, the yield is relatively high, the universality of a reaction substrate is wide, and thelike.
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Paragraph 0045-0048
(2020/05/30)
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- Highly adequate oxidative esterification of α-carbonyl aldehydes with alkyl halides in TBAI/TBHP mediated system
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An efficient and viable synthesis of α-ketoesters from alkyl halides and α-carbonyl aldehydes has been reported under metal-free conditions. The present method involves oxidative esterification of α-carbonyl aldehydes with alkyl halide using TBAI as a promoter and TBHP as an oxidant to form α-ketoesters in good to excellent yields with versatile structural diversity. Use of commercially accessible and inexpensive substrates, broad substrate scope and good functional group tolerance are the key features of this protocol.
- Bhargude, Pooja L.,Lade, Jatin J.,Patil, Bhausaheb N.,Vadagaonkar, Kamlesh S.,Chaskar, Atul C.
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supporting information
p. 1325 - 1333
(2019/04/30)
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- Copper-catalyzed Pummerer type reaction of α-thio aryl/heteroarylacetates: Synthesis of aryl/heteroaryl α-keto esters
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A copper catalyzed Pummerer type reaction of α-thio aryl/heteroarylacetates is described for the first time. This transformation represents a new route to synthesize α-keto esters, which are important intermediates for pharmaceuticals and organic synthesis. The reaction proceeds via in situ generation of a thionium ion that undergoes hydrolysis to furnish α-keto esters in synthetically viable yields (up to 82%).
- Saha, Pipas,Ray, Sumit Kumar,Singh, Vinod K.
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p. 1765 - 1769
(2017/04/13)
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- Alkyl halide-free heteroatom alkylation and epoxidation facilitated by a recyclable polymer-supported oxidant for the in-flow preparation of diazo compounds
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Highly reactive metal carbenes, generated from simple ketones via diazo compounds, including diazoamides and -phosphonates, using a recyclable reagent inflow, are transient but versatile electrophiles for heteroatom alkylation reactions and for epoxide formation. The method produces no organic waste, with the only byproducts being water, KI and nitrogen, without the attendant hazards of isolation of intermediate diazo compounds.
- Nicolle, Simon M.,Hayes, Christopher J.,Moody, Christopher J.
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supporting information
p. 4576 - 4579
(2015/03/18)
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- Palladium-catalyzed allylic esterification via C-C bond cleavage of a secondary homoallyl alcohol
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Palladium-catalyzed allylic esterifications of secondary homoallyl alcohols with acids via sequential retro-allylation and esterification are demonstrated, affording the corresponding allyl ester in up to 99% yield. The electron effect of the substituent of the secondary alcohol was found to be crucial to the selective C-C bond cleavage.
- Wang, Yong,Kang, Qiang
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supporting information
p. 4190 - 4193
(2014/10/15)
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- Synthesis of γ,δ-unsaturated quaternary α-alkylamino acids using umpolung reaction and Claisen rearrangement
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A new synthesis of γ,δ-unsaturated quaternary α-amino acid derivatives was developed utilizing N-alkylation and Claisen rearrangement of allyl α-iminocarboxylates.
- Mizota, Isao,Tanaka, Katsuki,Shimizu, Makoto
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supporting information; experimental part
p. 1847 - 1850
(2012/05/04)
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- Palladium-catalyzed divergent reactions of α-diazocarbonyl compounds with allylic esters: Construction of quaternary carbon centers
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Take two: α-Diazocarbonyl compounds display a diverse pattern of reactivity upon palladium-catalyzed reaction with esters. Esters bearing an alkynyl group on the carbonyl carbon atom lead to two different C-C bonds at the same carbon atom in a single operation through decarboxylation and migratory insertion, whereas aromatic and benzylic acid derivatives afford aromatic and benzylic esters bearing an O-substituted quaternary carbon center. Copyright
- Chen, Zi-Sheng,Duan, Xin-Hua,Zhou, Ping-Xin,Ali, Shaukat,Luo, Jian-Yi,Liang, Yong-Min
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supporting information; experimental part
p. 1370 - 1374
(2012/03/27)
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- Synthesis of α,β-unsaturated ketones by Pd-catalyzed decarboxylative allylation of α-oxocarboxylates
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A palladium/p-tolylphosphine system has been developed that catalyzes the extrusion of carbon dioxide from α-oxocarboxylic acid allyl esters, leading to α,β-unsaturated ketones (see scheme). The palladium complex activates the substrate and mediates the carbon-carbon bond formation to give allyl ketones, and subsequent double bond shift to the α,β position. The actual decarboxylation step with formation of the acyl nucleophile is promoted by phosphine.
- Rodriguez, Nuria,Manjolinho, Filipe,Gruenberg, Matthias F.,Goossen, Lukas J.
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supporting information; experimental part
p. 13688 - 13691
(2012/01/15)
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- Irreversible catalytic ester hydrolysis of allyl esters to give acids and aldehydes by homogeneous ruthenium and ruthenium/palladium dual catalyst systems
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An irreversible hydrolysis reaction of allyl esters (1) into carboxylic acids (2) and propanal (3) was achieved with a ruthenium/palladium (Ru/Pd) dual catalyst system. The optimized catalysts consists of a 1:1:1 mixture of (cyclopentadienyl)tris(acetonitrile)ruthenium hexafluorophosphate {[RuCp(MeCN)3] PF6}, bis(acetonitrile)palladium dichloride [PdCl2(MeCN)2] and 1,6-bis(diphenylphosphanyl)hexane (DPPHex). The reaction proceeds via isomerization of allyl esters to 1-propenyl esters and hydrolysis of them to give 2 and 3. The first isomerization step was virtually catalyzed by the Ru components and the second hydrolysis step was mainly catalyzed by the Pd components. The optimized bidentate phosphine (DPPHex) which has long alkylene chain effectively generates two vacant sites on the Ru centers by bridging coordination. When a chelating bidentate phosphine such as DPPE was employed, only one vacant site remained on the Ru center and resulted in a low activity. This chelating Ru complex of DPPE formed even in the presence of 2 equivalents of Ru or additional 1 equivalent of Pd. These differences in coordination behaviour between DPPHex and 1,2- bis(diphenylphosphanyl)ethane (DPPE) cause the differences of the catalytic activity in the first step. The phosphine coordination to Pd center slightly decreases the activity of second hydrolysis step but which was compensated by the increasing of the stability of Pd. On the whole, the optimized Ru/Pd dual catalyst system exhibited good performances on the irreversible hydrolysis of allyl esters.
- Nakamura, Asami,Hamasaki, Akiyuki,Goto, Sachihiko,Utsunomiya, Masaru,Tokunaga, Makoto
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supporting information; experimental part
p. 973 - 984
(2011/06/19)
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- Rapid access to α-alkoxy and α-amino acid derivatives through safe continuous-flow generation of diazoesters
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Microreactors: A highly efficient continuous-flow process has been developed for the synthesis of diazoesters from arylsulfonylhydrazones by means of in-flow Bamford-Stevens reactions. Furthermore, a range of α-alkoxy and α-amino acid derivatives have bee
- Bartrum, Hannah E.,Blakemore, David C.,Moody, Christopher J.,Hayes, Christopher J.
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supporting information; experimental part
p. 9586 - 9589
(2011/10/08)
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- Chiral cobalt-catalyzed enantioselective aerobic oxidation of α-hydroxy esters
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A chiral cobalt-catalyzed enantioselective aerobic oxidative kinetic resolution of (±)-α-hydroxy esters, using molecular oxygen as a sole oxidant, is reported and a maximum of selectivity factor (s) 31.9 was achieved with >99% enantiomeric excess for unreacted α-hydroxy esters.
- Alamsetti, Santosh Kumar,Sekar, Govindasamy
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supporting information; experimental part
p. 7235 - 7237
(2010/12/24)
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- Synthesis of tertiary α-hydroxy acids by silylene transfer to α-keto esters
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(Chemical Equation Presented) α-Keto esters can be converted into α-hydroxy acids in a single flask involving metal-catalyzed silylene transfer, 6π-electrocyclization, Ireland-Claisen rearrangement, and hydrolysis. This reaction sequence is stereoselectiv
- Howard, Brett E.,Woerpel
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p. 4651 - 4653
(2008/03/12)
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- Surfactant-mediated solvent-free dealkylative cleavage of ethers and esters and trans-alkylation under neutral conditions
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A simple, surfactant-mediated, one-pot, solvent-free dealkylative cleavage of aryl ethers and esters followed by subsequent optional trans-alkylation under essentially neutral conditions has been developed.
- Bhattacharya, Apurba,Patel, Nitin C.,Vasques, Tomas,Tichkule, Ritesh,Parmar, Gaurang,Wu, Jiejun
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p. 565 - 567
(2007/10/03)
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- A general and simple synthesis of phenylglyoxylic esters via the oxidation of mandelic esters with ammonium chlorochromate adsorbed on alumina
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A general method for preparation of phenylglyoxylic esters by oxidation of mandelic esters with readily available ammonium chlorochromate adsorbed on alumina is described.
- Zhang, Gui-Sheng,Gong, Hui
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p. 3149 - 3153
(2007/10/03)
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- The influence of oxime stereochemistry in the generation of nitrones from ω-alkenyloximes by cyclization or 1,2-prototropy
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Thermally induced cyclization of the anti-alkenyl oximes E-7a,b and E-17a,b affords cyclic α-alkoxycarbonylnitrones 8 and the 6,7-bicyclic nitrones 18, respectively. The syn-oximes Z-7b and Z-17b react via an alternate pathway to give exclusively the fuse
- Heaney, Frances,O'Mahony, Colm
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p. 341 - 349
(2007/10/03)
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- Photochemical Reactions of Alkenyl Phenylglyoxylates
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The photochemical reactions of alkyl phenylglyoxylate esters whose ester function contains double bonds of differing substitution, situated at varying distances from the carbonyl group, have been studied. The intramolecular Paterno-Buechi reaction is the dominating photoreaction when an electron rich alkenyl group is situated at the proper distance as in 1′,5′-dimethylhex-4′-enyl phenylglyoxylate (6). When the distance between the excited carbonyl group and the same alkenyl function is increased, as it is in 3′,7′-dimethyl-6′-octenyl phenylglyoxylate (7), intramolecular γ-hydrogen abstraction (Norrish type II) products, as well as the products of intramolecular photocycloaddition, are observed. We suggest this to be the result of a competitive distant dependent electron transfer reaction between the excited carbonyl group and the alkene. A longer distance of separation between these two reactive functions decreases the efficiency of formation of the cycloaddition product. When the separation of the same alkene from the glyoxylate is shortened as in 4′-methylpent-3′-enyl phenylglyoxylate (5), electron transfer-induced remote proton abstraction leading to cyclol formation occurs, in addition to the Paterno-Buechi reaction. Further reducing the distance as in 3′-methylbut-2′-enyl phenylglyoxylate (3) results in only the normal intramolecular (Norrish type II) and intermolecular hydrogen abstraction products. At a distance where both oxetane and cyclol formation are possible as in 5, decreasing the electron richness of the alkenyl group as in cis-3′-hexenyl phenylglyoxylate (cis-4) eliminates the oxetane product. Formation of cyclol is shown to be conformationally controlled in that a similar product is not observed to be formed from trans-3′-hexenyl phenylglyoxylate (trans-4). If both the electron richness of the alkenyl group and the distance of separation are decreased as in 2′-hexenyl phenylglyoxylate (2), only γ-hydrogen abstraction products result. Cis-trans isomerization of the olefln is not observed in either 2 or 4.
- Hu, Shengkui,Neckers, Douglas C.
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p. 6820 - 6826
(2007/10/03)
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