- Modular Tuning of Electrophilic Reactivity of Iridium Nitrenoids for the Intermolecular Selective α-Amidation of β-Keto Esters
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We report herein an Ir-catalyzed intermolecular amino group transfer to β-keto esters (amides) to access α-aminocarbonyl products with excellent chemoselectivity. The key strategy was to engineer electrophilicity of the putative Ir-nitrenoids by tuning electronic property of the κ2-N,O chelating ligands, thus facilitating nucleophilic addition of enol π-bonds of 1,3-dicarbonyl substrates.
- Lee, Minhan,Jung, Hoimin,Kim, Dongwook,Park, Jung-Woo,Chang, Sukbok
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p. 11999 - 12004
(2020/08/06)
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- Radical Aza-Cyclization of α-Imino-oxy Acids for Synthesis of Alkene-Containing N-Heterocycles via Dual Cobaloxime and Photoredox Catalysis
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Nitrogen-containing heterocycles are prevalent in both naturally and synthetically bioactive molecules. We report herein an unprecedented protocol for radical aza-cyclization of α-imino-oxy acids with pendant alkenes via synergistic photoredox and cobaloxime catalysis. With or without alkenes as the intermolecular cross-coupling partners, the transformation provides a variety of corresponding alkene-containing dihydropyrrole products in satisfactory yields. In the presence of external alkenes, the tandem reaction generates E-selective coupling products with excellent chemo- and stereoselectivity.
- Tu, Jia-Lin,Liu, Jia-Li,Tang, Wan,Su, Ma,Liu, Feng
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supporting information
p. 1222 - 1226
(2020/02/15)
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- Enantioselective Mannich reaction of β-keto esters with aromatic and aliphatic imines using a cooperatively assisted bifunctional catalyst
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An efficient urea-enhanced thiourea catalyst enables the enantioselective Mannich reaction between β-keto esters and N-Boc-protected imines under mild conditions and minimal catalyst loading (1-3 mol %). Aliphatic and aromatic substituents are tolerated on both reaction partners, affording the products in good enantiomeric purity. The corresponding β-amino ketones can readily be accessed via decarboxylation without loss of enantiomeric purity.
- Neuvonen, Antti J.,Pihko, Petri M.
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supporting information
p. 5152 - 5155
(2015/01/08)
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- Ligand steric and electronic effects on β-ketiminato neutral nickel(II) olefin polymerization catalysts
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A series of novel neutral nickel complexes 3a-g and 4a-d bearing the β-ketiminato ligands [(2,6-iPr2C6H 3)N=CHCHC(R)O]Ni(R′)(L) (for 3a-g, R′ = Me, L = Py, and R = tBu (3a), Ph (3b), 1-naphthyl (3c), 9-anthryl (3d), PhNMe 2(p) (3e), PhOMe(p) (3f), PhCF3(p) (3g); for 4a-d, R′ = Ph, L = PPh3, and tBu (4a), Ph (4b), 1-naphthyl (4c), 9-anthryl (4d)) have been synthesized and characterized. The molecular structures of 3b-d,f,g and 4a,c were further confirmed by X-ray crystallographic analysis. These complexes were employed in ethylene polymerization to systematically investigate ligand steric and electronic effects on the catalytic properties, including activity, molecular weight (MW), and branching number of the polyethylene obtained. The complexes bearing more bulky ligands showed higher activities and produced more branched polyethylene. Electron-deficient ligands were found to increase the catalytic activity, decrease the MW, and enhance the branching content of the polyethylene. In addition, phosphine NiII-Ph complexes 4a-d proved to be more active than the corresponding pyridine NiII-Me complexes 3a-d, probably due to the easier dissociation of PPh3 relative to a pyridine from a nickel center.
- Song, Dong-Po,Shi, Xin-Cui,Wang, Yong-Xia,Yang, Ji-Xing,Li, Yue-Sheng
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experimental part
p. 966 - 975
(2012/04/10)
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- Expeditious solid-phase synthesis of pyrazoledicarboxylic acid derivatives by functionalization of resin-bound cyanoformate
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Esterification of the Wang resin 5 with the monoamide of oxalic acid (oxamic acid, 7) followed by dehydration of the amide function furnishes the resin-bound cyanoformate 9, which can be elaborated by zinc-catalyzed reaction with β-keto esters. The obtained enamino keto diesters 10a-d react with hydrazines affording, after removal from the solid support, fully substituted pyrazoledicarboxylic acids 12a-n. Optimization of the above sequence and the solid-phase synthesis of a small test-library of 1,5-disubstituted pyrazole-3,4-dicarboxylic acid derivatives are described. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
- Morelli, Carlo F.,Saladino, Alberto,Speranza, Giovanna,Manitto, Paolo
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p. 4621 - 4627
(2007/10/03)
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- A general synthesis of dioxolenone prodrug moieties
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A general method for the synthesis of dioxolenone prodrug moieties from appropriately substituted β-ketoesters is described. This novel and versatile sequence allows for the synthesis of alkyl- or aryl-substituted dioxolenone alcohols 8 or bromides 9. Coupling of the bromides 9 to prepare bis-dioxolenone phosphonate prodrug esters is also presented.
- Sun, Chong-Qing,Cheng, Peter T.W.,Stevenson, Jay,Dejneka, Tamara,Brown, Baerbel,Wang, Tammy C.,Robl, Jeffrey A.,Poss, Michael A.
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p. 1161 - 1164
(2007/10/03)
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- Process for producing pivaloyl-acetic acid ester
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A process for producing a pivaloylacetic acid ester comprises reacting pivaloyl chloride with an acetoacetic acid ester of an alkyl group having 1 to 4 carbon atoms in the presence of at least one nitrogen-containing basic compound (a) selected from among pyridine compounds, N,N-dialkylanilines and imidazole compounds and from 0.01 to 0.5 mole equivalent, based on the pivaloyl chloride, of a magnesium compound (b) to thereby prepare a pivaloylacetoacetic acid ester and then alcholyzing or alkali-hydrolyzing the pivaloylacetoacetic acid ester to thereby give a pivaloylacetic acid ester having a high purity at a low cost.
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- The Reformatsky Reaction of 1-Acyl-3,5-dimethylpyrazoles. A Convenient Preparation of 4-Amino-3-oxoalkanoic Acid Derivatives
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The conversion of N-acylpyrazoles into β-keto esters was accomplished efficiently by the treatment with α-bromo esters and zinc dust.Using this Reformatsky reaction of N-acylpyrazoles, 4-(protected amino)-3-oxoalkanoic acid derivatives were conveniently prepared as the key intermediates in the synthesis of statines.
- Kashima, Choji,Kita, Isanobu,Takahashi, Katsumi,Hosomi, Akira
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p. 723 - 726
(2007/10/02)
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- Structure-Activity Relations. Part 12. Antibacterial Activity of a Series of 2,4-Diamino-6-substituted 5-(4-pyridylmethylamino)pyrimidines and 2,4-Diamino-5-(4-substituted benzylamino)pyrimidines.
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A series of 6-substituted 2,4-diamino-5-(4-pyridylamino)pyrimidines and of 2,4-diamino-5-(4-substituted benzylamino)pyrimidines has been prepared.Their antibacterial activity towards L. casei, S. aureus and E. coli has been investigated.These activities have been successfully correlated by Hansch-type relations.Dependence on both lipophilicity and electronic (polar) factors has been found.The results are related to the structure and interactions with the receptor.
- Bowden, Keith,Bright, Andrew C.
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p. 514 - 539
(2007/10/02)
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- Evidence for Ketene Intermediates in the Decarbonylation of 2,4-Dioxo Acids and Esters and 2-Oxobutanedioic Acid Esters
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The mechanism by which α,γ-dioxo carboxylic acid esters 1 and 2-oxobutanedioic acid diesters 2 lose CO was explored.The compounds, 5,5-dimethyl-2,4-dioxohexanoic acid ethyl ester, 1a, α-2-dioxocyclohexaneacetic acid ethyl ester, 1b, and α,1-dioxotetrahydro-2-naphthaleneacetic acid ethyl ester, 1c, lose CO at 170-190 deg C to yield the corresponding β-keto esters 3a-c.When compounds 1 or the parent acids 4 were heated to 170-190 deg C with water in a sealed reactor, they yielded ketones resulting from replacement by H of C(O)CO2R from 1 or C(O)CO2H from 4. β-Ketoesters suffered replacement by H of the carbethoxy group to yield the corresponding ketones when heated with water at about 105 deg C.Acylketenes, such as 4,4-dimethyl-1-pentene-1,3-dione, 6a, 2-oxo-cyclohexylidenemethanone, 6b, 1-oxotetrahydro-2-naphthylidenemethanone, 6c, 3-methyl-1-butene-1,3-dione, 6d, and 1-butene-1,3-dione, 6e, are implicated as the common intermediates that react with water to form β-keto acids that subsequently decarboxylateto yield the ketones 5.Intense IR frequencies in the region of 2120-2140 cm-1, characteristic of ketenes, are observed when 1, 2, or 3 is subjected to GC-FTIR analysis with the injector and light pipe at 280 deg C.Loss of carbon monoxide and alcohol at high temperature is required to form 6 from 1, while only the loss of alcohol at lower temperature is needed to form 6 from 3.
- Emerson, David W.,Titus, Richard L.,Gonzalez, Rowena M.
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p. 5301 - 5307
(2007/10/02)
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- A Selective Method for the Direct Conversion of Aldehydes into β-Keto Esters with Ethyl Diazoacetate Catalyzed by Tin(II) Chloride
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Aldehydes are efficiently converted into β-keto esters by the addition of ethyl diazoacetate in the presence of tin(II) chloride.
- Holmquist, Christopher R.,Roskamp, Eric J.
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p. 3258 - 3260
(2007/10/02)
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- Preparation of alpha-pivaloyl-substituted acetic acid esters
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An alpha-pivaloyl-substituted acetic acid ester of the formula (H3 C)3 CCOCH2 COOR, wherein R is an optionally-substituted alkyl, aryl, alkaryl, or aralkyl group, is prepared by (a) reacting an alpha-pivaloyl-substituted malonic acid ester with a base selected from the class consisting of alkali metal alkoxides and compounds of the formula MXY, wherein M is an alkaline earth metal, X is an alkoxy group, and Y is either an alkoxy group or a halogen atom, and (b) acidifying the resulting reaction mixture.
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- Sulfur-Extrusive Rearrangement of α-Acylthio Ester by Lithium Amide
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α-Acylthio esters readily undergo facile rearrangement to give β-keto esters on treatment with lithium amide at -78 deg C.Thiolactone 3, a key intermediate for thiolactonic antibiotics, was synthesized by utilizing the rearrangement.
- Tsuzuki, Kazuo,Akeyoshi, Masaharu,Omura, Satoshi
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p. 395 - 396
(2007/10/02)
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- FACILE SYNTHESIS OF β-KETOESTERS BY A COUPLING REACTION OF THE REFORMATSKY REAGENT WITH ACYL CHLORIDES CATALYZED BY A PALLADIUM COMPLEX
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β-Ketoesters were obtained in good yields by the reaction of the Reformatsky reagent with acyl chlorides catalyzed by a palladium complex under mild conditions.
- Sato, Toshio,Itoh, Toshiyuki,Fujisawa, Tamotsu
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p. 1559 - 1560
(2007/10/02)
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- Aliphatic β-keto esters
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A process for the production of aliphatic β-keto esters by reacting a dialkyl ketone with a dialkylcarbonate in the presence of an at least equivalent quantity of a basic condensation agent based on the dialkyl ketone at a reaction temperature of 20° to 80° C and the reaction product is subsequently converted by acidification into the β-keto ester. By carrying out the condensation reaction in the presence of hexamethylphosphoric acid triamide as solvent advantageously higher yields of 20 to 50 % can be obtained by the inventive process of compared to conventional processes.
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