- Evidence for Ketene Intermediates in the Reactions of 2-Oxobutanedioic Acid Diesters with Alcohols and Water
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The reactions of diethyl ester (1a) and dimethyl ester (1b) of 3-methyl-2-oxobutanedioic acid with excess ethanol, methanol, or water in a sealed tube at approximately 125 deg C were studied.With methanol, 1a yielded mainly 3-methyl-2-oxobutanedioic acid 1-ethyl 4-methyl diester, 2a; with ethanol, 1b yielded mainly the 4-ethyl 1-methyl diester, 2b, while reaction of 1a with water yielded carbon dioxide, 2-oxobutanoic acid ethyl ester, 6, and 2-methyl-3-oxopropanoic acid ethyl ester, 7.These results suggested that the ketene intermediates 3-methyl-2,4-dioxo-3-butenoic acid ethyl or methyl ester, 4a and 4b, respectively, are implicated.The similarity of these reactions to those exhibited by ethyl acetoacetate, such as alkoxy group exchange, and formation of dehydroacetic acid, now thought to proceed by way of acetyl ketene, was demonstrated.
- Emerson, David W.,Titus, Richard L.,Gonzalez, Rowena M.
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- Catalytic cyclization reactions of Huisgen zwitterion with -ketoesters by in situ chemoselective phosphine oxide reduction
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The first examples of catalytic cyclization reactions between the Huisgen zwitterion and α-ketoester derivatives are reported. The use of phenylsilane with a substoichiometric amount of bis(p-nitrophenyl)phosphate/diisopropylethylamine proved to be crucial for the in situ reduction of the phosphine oxide formed during the reaction. The optimized protocol is applied to alkyl or aryl ketoesters, furnishing either the corresponding cycloadducts or the hydrazone derivatives, depending on the substitution patterns of the substrates, in moderate to good yields (up to 80% yield, 18 examples).
- Fourmy, Kévin,Voituriez, Arnaud
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- Diastereo- and Enantioselective Synthesis of Fluorine Motifs with Two Contiguous Stereogenic Centers
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The synthesis of chiral fluorine containing motifs, in particular, chiral fluorine molecules with two contiguous stereogenic centers, has attracted much interest in research due to the limited number of methods available for their preparation. Herein, we report an atom-economical and highly stereoselective synthesis of chiral fluorine molecules with two contiguous stereogenic centers via azabicyclo iridium-oxazoline-phosphine-catalyzed hydrogenation of readily available vinyl fluorides. Various aromatic, aliphatic, and heterocyclic systems with a variety of functional groups were found to be compatible with the reaction and provide the highly desirable product as single diastereomers with excellent enantioselectivities.
- Ponra, Sudipta,Rabten, Wangchuk,Yang, Jianping,Wu, Haibo,Kerdphon, Sutthichat,Andersson, Pher G.
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supporting information
p. 13878 - 13883
(2018/10/24)
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- Cationic Ir/Me-BIPAM-catalyzed asymmetric intramolecular direct hydroarylation of α-ketoamides
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Asymmetric intramolecular direct hydroarylation of α-ketoamides gives various types of optically active 3-substituted 3-hydroxy-2-oxindoles in high yields with complete regioselectivity and high enantioselectivities (84-98 % ee). This is realized by the use of the cationic iridium complex [Ir(cod) 2](BArF4) and the chiral O-linked bidentate phosphoramidite (R,R)-Me-BIPAM. Carbon's got a brand new bond: Asymmetric intramolecular direct hydroarylation of α-ketoamides gives various optically active 3-substituted 3-hydroxy-2-oxindoles in high yields with complete regioselectivity and high enantioselectivities. This is realized by the use of an asymmetric cationic iridium complex formed in situ (see Scheme).
- Shirai, Tomohiko,Ito, Hajime,Yamamoto, Yasunori
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supporting information
p. 2658 - 2661
(2014/03/21)
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- Preparation of α,α-disubstituted α-amino acid derivatives via alkyl addition to α-oxime esters with organozinc species
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An α-oxime ester derivative prepared via treatment of an acetylenedicarboxylate or an α-keto ester with hydroxylamine underwent C-alkylation to the C=N bond of the oxime group by a Lewis-acid-promoted reaction with a trialkylzincate or a dialkylzinc reagent. The O-N bond of the thus obtained adduct was reductively cleaved under hydrogenolysis in the presence of the Pd-C catalyst to afford an α-amino ester. Treatment of the oxime derivative prepared from methyl 5-bromo-2-oxopentanoate with the trialkylzincate gave an α-alkyl proline derivative via the addition reaction followed by the intramolecular attack upon a bromine-bearing carbon. The reaction of ethyl 4-oxo-2-pentynoate with hydroxylamine formed an isoxazole derivative by way of the intramolecular attack of an in situ-generated oxime to the carbonyl group. From this isoxazole derivative, ethyl 2-amino-4-oxo-2- pentenoate was given by the Pd-C-catalyzed hydrogenolysis. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Mitani, Michiharu,Tanaka, Yasunori,Sawada, Akihiko,Misu, Ayuko,Matsumoto, Yoshihiro
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body text
p. 1383 - 1391
(2009/04/04)
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- Method for preparing chiral diphosphines
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The invention concerns a method for preparing a compound of formula (1) wherein: A represents naphthyl or phenyl optionally substituted; and Ar1, Ar2independently represent a saturated or aromatic carbocyclic group, optionally substituted.
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- Studies on non-thiazolidinedione antidiabetic agents. 1. Discovery of novel oxyiminoacetic acid derivatives
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A novel series of oxyiminoacetic acid derivatives were synthesized in an effort to develop a potent antidiabetic agent, which does not contain the 2,4-thiazolidinedione moiety. These compounds were evaluated for glucose and lipid lowering effects in genetically obese and diabetic KKAy mice. Several of the compounds showed strong antidiabetic activity, including functional potency at peroxisome proliferator-activated receptor (PPAR)-γ. (Z)-2-[4-[(5-Methyl-2-phenyl-1,3-oxazol-4-yl)methoxy]benzyloxyimino]-2-(4- phenoxyphenyl)acetic acid (25) significantly reduced plasma glucose (33%, p0.01) and plasma triglycelide levels (43%, p0.01) even at a dosage of 0.001% in diet. Pharmacokinetic analyses of 25 are also reported.
- Imoto, Hiroshi,Imamiya, Eikoh,Momose, Yu,Sugiyama, Yasuo,Kimura, Hiroyuki,Sohda, Takashi
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p. 1349 - 1357
(2007/10/03)
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- Tripeptidylpeptidase inhibitors
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A compound of formula wherein the substituents are defined as in the specification and salts or hydrates thereof is disclosed as well as a method of treating disorders associated with the inactivation or excessive degradation of cholecystokinin.
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- Asymmetric hydrogenation method of a ketonic compound and derivative
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The present invention relates to a process for the asymmetric hydrogenation of a ketonic compound and derivative. The invention relates to the use of optically active metal complexes as catalysts for the asymmetric hydrogenation of a ketonic compound and derivative. The process for the asymmetric hydrogenation of a ketonic compound and derivative is characterized in that the asymmetric hydrogenation of said compound is carried out in the presence of an effective amount of a metal complex comprising as ligand an optically active diphosphine corresponding to one of the following formulae: STR1
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- Synthesis and reactivity of α and β-chloro-α-phenylselanyl esters
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Thermal decomposition of the dichloro-adducts derived from α-phenylselanylesters 1, 2 and 4 has been studied. N-Chloro-succinimide treatment of esters 2 was an efficient preparative method for α-chloro-α-phenylselanylesters 10 and α-chloro-α,β-unsaturated esters 11. Some transformations of esters 10 were achieved, α,β-Dichloro-α-phenylselanylesters 22 were prepared from β-chloro-α-phenylselanylesters 5 or by decomposition of the dichloroselenuranes 21 derived from esters 4. (C) 2000 Elsevier Science Ltd.
- Lebarillier, Loic,Outurquin, Francis,Paulmier, Claude
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p. 7495 - 7502
(2007/10/03)
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- A convenient preparation of α-keto esters by the Grignard reaction on N-acylpyrazoles
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The α-keto esters were prepared by the formation of N-acylpyrazole followed by the appropriate Grignard reaction. These short step reaction conveniently afforded various α-keto esters in good yields.
- Kashima, Choji,Shirahata, Yoshie,Tsukamoto, Yoshihiro
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p. 459 - 464
(2007/10/03)
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- Tungsten complex induced dehydration of 2,3-dihydroxycarboxylic acids to α-keto acids
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In the absence of added base, WOCl4 induces rapid dehydration of the title compounds to give α-keto acids. A mechanism is suggested based on a neighboring group effect.
- Yu,Schwartz
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p. 6791 - 6794
(2007/10/02)
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- A One-Step Synthesis of Alkyl 2-Oxo-3-alkenoates from Alkenyl Grignard Reagents and Dialkyl Oxalates
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The reaction of alkenyl Grignard reagents with dialkyl oxalates at -80 deg C in an ether/tetrahydrofuran mixture (1:1) leads to the formation of the corresponding alkyl 2-oxo-3-alkenoates in high yields.Thus a mild and convenient one-step synthesis of 3-isopropenyl-substituted 2-oxoesters is described.
- Rambaud, M.,Bakasse, M.,Duguay, G.,Villieras, J.
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p. 564 - 566
(2007/10/02)
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- SYNTHESIS OF ALKENOIC ACID DERIVATIVES CONTAINING CYCLOPROPANE RING, NEW JUVENILE HORMONE ANALOGS
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A synthetic method is described for the preparation of new type juvenoids .
- Baan, Gabor,Vinczer, Peter,Novak, Lajos,Szantay, Csaba
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p. 4261 - 4264
(2007/10/02)
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- Studies on Conjugated Nitriles. IV. Reaction of Ethyl Cyanoformate with Organomagnesium, -zinc, and - cadmium Reagents, and Phosphonium Ylide
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The reaction of ethyl cyanoformate (1a) with phenylcadmium bromide (3a) gave ethyl benzoate (4), ethyl 2-phenyl-2-oxoacetate (5a), and 2-ethoxycarbonyl-2,4-diphenyl-3-imidazoline-5-one (6).In the presence of zinc chloride, the addition of 3a to the cyano group of 1a occured to give only 5a.The similar reaction of 1a with other organocadmium reagents (3b-f) in the presence of zinc chloride gave the corresponding α-ketoesters (5b-f) in moderate yields.The reactions of 1a with other organometallic reagents, e.g. phenylmagnesium (2a), -zinc (8) and -mercuric bromide (9) in the presence or in the absence of zinc chloride were examined.Furthermore, the addition of phosphonium ylide 13a to the cyano group of 1a in the presence of stannic chloride occured exclusively to give the phosphonium salt 14.The results are discussed in terms of the hard and soft acids and bases (HSAB) principle.Keywords - ethyl cyanoformate; benzoyl cyanide; organocadmium reagent; organozinc reagent; phosphonium ylide; cyano group addition; α-ketoester; α-dehydroamino ester; Lewis acid
- Akiyama, Yasunobu,Takebayashi, Shoko,Kawasaki, Tomomi,Sakamoto, Masanori
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p. 1800 - 1807
(2007/10/02)
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- MgBr2-PROMOTED ELECTROSYNTHESIS OF SULFENIMINES (THIOOXIMES) FROM α-AMINO-ALKANOATES AND DIARYL/DIALKYL DISULFIDES IN A CH2Cl2-H2O TWO-PHASE SYSTEM. A STRAIGHTFORWARD PREPARATION OF C(6)/C(7)-SULFENIMINE DERIVATIVES OF PENICILLIN AND CEPHALOSPORIN
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Direct transformation of α-aminoalkanoates and diaryl or dialkyl disulfides to the corresponding sulfenimines by electrolysis in a CH2Cl2-H2O-MgBr2-(Pt electrodes) system and its application to the sulfenylation of C(6)/C(7)-amino groups of penicillin and cephalosporin are described.
- Torii, Sigeru,Tanaka, Hideo,Hamano, Sin-ichi,Tada, Nobuhito,Nokami, Junzo,Sasaoka, Michio
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p. 1823 - 1826
(2007/10/02)
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- Synthesis of piperazine-2,5-diones related to bicyclomycin: 1,4-dibenzyl-3-hydroxy-3-piperazine-2,5-dione. 2. Route via cyclic intermediates
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1,4-Dibenzyl-3-hydroxy-3-piperazine-2,5-dione (43),which incorporates several of the structural features of the antibiotic bicyclomycin, has been synthesized via a reaction sequence involving early construction of the piperazine-2,5-dione ring.In model studies 3-isopropylidenepiperazine-2,5-dione was di-N-benzylated and epoxidized to give 4,7-dibenzyl-2,2-dimethyl-1-oxa-4,7-diazaspirooctane-5,8-dione (10).The opening of the epoxide ring of 10 by several reagents was investigated and it was found that treatment with magnesium isopropylcyclohexylamide (MICA) gives 1,4-dibenzyl-3-hydroxy-3-(1-methylethenyl)piperazine-2,5-dione (23).Treatment of ethyl 3-(2-methoxyethyl)-3-methyl-glycidate (28) with p-toluenesulfonic acid followed by hydrogenation and oxidation gives ethyl 5-methoxy-3-methyl-2-oxopentanoate, which on reaction with chloroacetamide and sulfuric acid followed by treatment of the resulting enamide with ammonia gives (Z)- and (E)-3-(4-methoxybut-2-ylidene)piperazine-2,5-dione.Di-N-benzylation of these followed by epoxidation gives (Z)- and (E)-4,7-dibenzyl-2-(2-methoxyethyl)-2-methyl-1-oxa-4,7-diazaspirooctane-5,8-dione (41 and 42).Treatment of 41 with MICA converts it to compound 43.Chromatography of 43 on silica converts it in part to N-benzyl-N-(2-benzylamino-2-oxoethyl)-3-(2-methoxyethyl)-2-oxo-3-butenamide, which on treatment with MICA regenerates 43.
- Yates, Peter,Hoare, John Harold
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p. 1397 - 1404
(2007/10/02)
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- REACTION OF ORGANOCADMIUM REAGENTS WITH ETHYL CYANOFORMATE: PREPARATION OF α-KETO ESTERS
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Organocadmium reagents reacted with the cyano-function of ethyl cyanoformate in the presence of ZnCl2 to afford the corresponding α-keto esters.
- Akiyama, Yasunobu,Kawasaki, Tomomi,Sakamoto, Masanori
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p. 1231 - 1232
(2007/10/02)
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- Reaction of α-Azido Esters with Lithium Ethoxide: Synthesis of Dehydroamino Esters and α-Keto Esters
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α-Azido esters 4 react with catalytic amounts of ethoxide in tetrahydrofuran/ethanol to evolve nitrogen and form dehydroamino esters 3.Acid hydrolysis gives α-keto esters 5 in good yields.
- Manis, Paul A.,Rathke, Michael W.
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p. 4952 - 4954
(2007/10/02)
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