- Prenylated β-diketones, two new additions to the family of biologically active Hypericum perforatum L. (Hypericaceae) secondary metabolites
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Two novel β-diketones, 2,6,9-trimethyl-8-decene-3,5-dione (A) and 3,7,10-trimethyl-9-undecene-4,6-dione (B), were identified from the renowned medicinal plant Hypericum perforatum L. The structures of β-diketones A and B were corroborated by syntheses (4 steps starting from methyl acetoacetate, overall yields 30% and 23%, respectively). In solution, these β-diketones predominantly exist as two rapidly interconverting β-keto-enol tautomers. The structures of A and B show some common fragments with the molecules of hyperforin and adhyperforin, respectively, the acknowledged multi-target secondary metabolites from St. John's wort. It is therefore not surprising that A displayed a noteworthy biological activity profile as well (including brine shrimp toxicity, antinociceptive, antidepressant and acetylcholinesterase inhibitory activity). β-Diketone A manifested the most outstanding potency as an acetylcholinesterase inhibitor with IC50 value of 1.51 μM pointing again to the β-keto-enol moiety as a promising lead structure for the development of drugs that could lessen symptoms of Alzheimer's disease (such as dementia, depression and pain).
- Radulovi?, Niko S.,Gen?i?, Marija S.,Stojanovi?, Nikola M.,Randjelovi?, Pavle J.,Baldovini, Nicolas,Kurteva, Vanya
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- SAPONINS FROM STEM BARK OF PETERSIANTHUS MACROCARPUS
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Two bioactive saponins were isolated from the stem bark of Petersianthus macrocarpus.Their structures were elucidated by chemical degradations and by a combination of 2D NMR techniques and by Californium plasma desorption mass spectrometry.They are 3-O-2)>3)>-β-D-glucuronopyranosyl>-21-O- barringtogenol C and 3-O-2)>3)>-β-D-glucuronopyranosyl>-28-O-α-L-rhamnopyranosyl barringtogenol C-21-O-benzoate.The absolute configuration of nilic acid was determined by partial synthesis. 3,3'-Dimethoxy ellagic acid and 3,3'-dimethoxy-4-O-β-D-glucopyranosyl ellagic acid were also isolated.Key Word Index: Petersianthus macrocarpus; Lecythidaceae; bark; saponins; nilic acid; ellagic acid.
- Massiot, Georges,Chen, Xiang-Fei,Lavaud, Catherine,Men-Olivier, Louisette le,Delaude, Clement,et al.
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- Total Synthesis of Oridamycins A and B
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(Chemical Equation Presented) The total synthesis of both oridamycin A and oridamycin B was accomplished starting from a common synthetic intermediate readily prepared from geranyl acetate. The sequence utilizes an oxidative radical cyclization to construct the trans-decalin ring system, setting three of four contiguous stereocenters in one operation. The carbazole nucleus was forged through a one-pot process entailing acid-promoted dehydration followed by 6π-electrocyclization/aromatization.
- Trotta, Adam H.
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- Catalytic Asymmetric Homologation of Ketones with α-Alkyl α-Diazo Esters
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The homologation of ketones with diazo compounds is a useful strategy to synthesize one-carbon chain-extended acyclic ketones or ring-expanded cyclic ketones. However, the asymmetric homologation of acyclic ketones with α-diazo esters remains a challenge due to the lower reactivity and complicated selectivity. Herein, we report the enantioselective catalytic homologation of acetophenone and related derivatives with α-alkyl α-diazo esters utilizing a chiral scandium(III) N,N′-dioxide as the Lewis acid catalyst. This reaction supplies a highly chemo-, regio-, and enantioselective pathway for the synthesis of optically active β-keto esters with an all-carbon quaternary center through highly selective alkyl-group migration of the ketones. Moreover, the ring expansion of cyclic ketones was accomplished under slightly modified conditions, affording a series of enantioenriched cyclic β-keto esters. Density functional theory calculations have been carried out to elucidate the reaction pathway and possible working models that can explain the observed regio- and enantioselectivity.
- Tan, Fei,Pu, Maoping,He, Jun,Li, Jinzhao,Yang, Jian,Dong, Shunxi,Liu, Xiaohua,Wu, Yun-Dong,Feng, Xiaoming
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supporting information
p. 2394 - 2402
(2021/02/16)
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- Method for preparing pentazocine intermediate
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The invention belongs to the technical field of chemical synthesis, and provides a method for preparing a pentazocine intermediate, which comprises the following steps: by using low-price methyl acetoacetate as a raw material, carrying out methylation, methoxyformylation and removal of one methoxyformyl group, reducing by using a reducing agent, and reacting the reduction product with alkyl sulfonyl chloride to obtain the pentazocine intermediate; generating a compound with a dialkyl sulfonyl group; reacting a compound with dialkyl sulfonyl with phthalimide potassium salt, removing one alkyl sulfonyl, and grafting phthalimide; carrying out dehydrogenation reaction on the phthalimido product under an alkaline condition to generate a vinyl compound, and reacting the vinyl compound with hydrazine hydrate to obtain the pentazocine intermediate. Cheap compounds are used as initial raw materials, the whole route avoids high-pressure and high-temperature dangerous reactions, and industrial production is facilitated.
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Paragraph 0044-0045
(2021/02/13)
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- Palladium Catalyzed Ring Expansion Reaction of Isoxazolones with Isocyanides: Synthesis of 1,3-Oxazin-6-One Derivatives
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A palladium catalyzed ring expansion reaction of isoxazolones with isocyanides was disclosed. In the reaction, a cascade process involving ring-opening/cyclization was suggested. The reaction features high atomic economy due to no elimination of CO2 occurred. Moreover, products obtained demonstrate aggregation-induced emission properties with relatively high solid-state emission efficiencies. (Figure presented.).
- Zhu, Yi-Ming,Zhang, Wan,Li, Hongkun,Xu, Xiao-Ping,Ji, Shun-Jun
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p. 808 - 818
(2020/12/03)
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- Synthesis method of pirimicarb intermediate 2-methyl acetoacetate
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The invention relates to a synthesis method of a pirimicarb intermediate 2-methyl acetoacetate, comprising the following steps of: in the presence of tertiary amine and a polymerization inhibitor, carrying out an addition reaction on raw materials methyl acrylate and acetyl chloride to obtain 2-acetyl-methyl acrylate, and carrying out hydrogenation reduction to obtain the product 2-methyl acetoacetate. The synthetic method of the pirimicarb intermediate 2-methyl acetoacetate has the advantages of high yield, high purity and few byproducts.
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Paragraph 0040; 0044-0047; 0050-0052; 0055-0057; 0060-0062
(2020/12/10)
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- Synthesis method of 2-methyl methyl acetoacetate for pesticide production
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The invention discloses a synthesis method of 2-methyl methyl acetoacetate for pesticide production. By means of matching of methyl acetoacetate, palladium on carbon, acetic acid and pyridine, the recovery rate of methyl acetoacetate can be increased while the reaction rate is proper; through control over the ratio of formaldehyde to methyl acetoacetate, the recovery rate of methyl acetoacetate can be increased while quality is guaranteed; through control over the adding time of formaldehyde, the yield of products can be increased, filtered palladium on carbon is recycled, the production cost can be reduced, the vacuum degree ranges from 1,330 Pa to 2,660 Pa, and the effect of reduced pressure distillation can be improved. 2-methyl methyl acetoacetate synthesized through the synthesis method has the advantages of being high in yield and low in cost, market potential is large, and prospects are wide.
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Paragraph 0011; 0012; 0013; 0014
(2017/08/27)
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- Iron-Catalyzed Carbene Insertion Reactions of α-Diazoesters into Si-H Bonds
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An efficient iron-catalyzed carbene insertion reaction of α-diazo carbonyl compounds into the Si-H bond was developed. A wide range of α-silylesters was obtained in high yields (up to 99%) from α-diazoesters using a simple iron(II) salt as catalyst.
- Keipour, Hoda,Ollevier, Thierry
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supporting information
p. 5736 - 5739
(2017/11/10)
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- Enantioselective Palladium-Catalyzed Carbene Insertion into the N?H Bonds of Aromatic Heterocycles
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C3-substituted indoles and carbazoles react with α-aryl-α-diazoesters under palladium catalysis to form α-(N-indolyl)-α-arylesters and α-(N-carbazolyl)-α-arylesters. The products result from insertion of a palladium-carbene ligand into the N?H bond of the aromatic N-heterocycles. Enantioselection was achieved using a chiral bis(oxazoline) ligand, in many cases with high enantioselectivity (up to 99 % ee). The method was applied to synthesize the core of a bioactive carbazole derivative in a concise manner.
- Arredondo, Vanessa,Hiew, Stanley C.,Gutman, Eugene S.,Premachandra, Ilandari Dewage Udara Anulal,Van Vranken, David L.
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supporting information
p. 4156 - 4159
(2017/04/03)
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- Method for preparing 2-methyl-1,3-dicarbonyl derivative
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The invention discloses a method for preparing a 2-methyl-1,3-dicarbonyl derivative. A 1,3-dicarbonyl derivative serves as an initiator, raw materials are easy to obtain, and a great variety of raw materials are available. The product obtained through the method has high type diversity and can be used directly or used for other further reactions. Besides, only organic peroxides and a catalytic amount of inorganic copper salt are used, so that cost is low. According to the method, a reaction is conducted in air, reaction conditions are mild, pollution is small, reaction time is short, the yield of the target product is high, reaction operation and aftertreatment are easy, and the method is suitable for industrial production.
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Paragraph 0042
(2016/10/08)
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- Calcium-Catalyzed Synthesis of Polysubstituted 2-Alkenylfurans from β-Keto Esters Tethered to Propargyl Alcohols
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An efficient synthesis of polysubstituted 2-alkenylfurans using Ca(NTf2)2/KPF6as a catalytic mixture is described. It is based on the cycloelimination of readily available propargyl alcohols tethered to β-keto esters under dry conditions to avoid competitive Meyer–Schuster rearrangement. The furan can be further functionalized in situ by a calcium-catalyzed Friedel–Crafts-type reaction with secondary and tertiary alcohols. The title reaction allows for the high-yielding preparation of di-, tri-, and tetrasubstituted 2-alkenylfurans, which are important subunits of bioactive compounds.
- Morcillo, Sara P.,Leboeuf, David,Bour, Christophe,Gandon, Vincent
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supporting information
p. 16974 - 16978
(2016/11/16)
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- Expanding dynamic kinetic protocols: Transaminase-catalyzed synthesis of α-substituted β-amino ester derivatives
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Several α-alkylated β-amino esters have been obtained via DKR processes employing a kit of transaminases and isopropylamine as an amino donor in aqueous medium under mild conditions. Thus, while acyclic α-alkyl-β-keto esters afforded excellent conversions and enantioselectivities, although usually low diastereoselectivities, using more constrained cyclic β-keto esters high to excellent inductions were obtained.
- Cuetos, Anibal,Lavandera, Ivan,Gotor, Vicente
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supporting information
p. 10688 - 10690
(2013/11/06)
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- Catalytic asymmetric insertion of diazoesters into Aryl-CHO bonds: Highly enantioselective construction of chiral all-carbon quaternary centers
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This paper describes a catalytic enantioselective route to synthesize functionalized all-carbon quaternary acyclic systems via a boron Lewis acid-promoted formal C-C insertion of diazoesters into aryl-CHO bonds. In the presence of chiral (S)-oxazaborolidinium cation 1d as a catalyst, the reaction proceeded in good yield (up to 83%) with good regioselectivity (up to 88:12) and excellent enantioselectivity (up to 99% ee). The synthetic potential of this method was illustrated by conversion of the products to both α-and β-amino esters.
- Gao, Lizhu,Kang, Byung Chul,Ryu, Do Hyun
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supporting information
p. 14556 - 14559
(2013/10/22)
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- Access to enantiopure α-alkyl-β-hydroxy esters through dynamic kinetic resolutions employing purified/overexpressed alcohol dehydrogenases
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α-Alkyl-β-hydroxy esters were obtained via dynamic kinetic resolution (DKR) employing purified or crude E. coli overexpressed alcohol dehydrogenases (ADHs). ADH-A from R. ruber, CPADH from C. parapsilosis and TesADH from T. ethanolicus afforded syn-(2R,3S) derivatives with very high selectivities for sterically not impeded ketones ('small-bulky' substrates), while ADHs from S. yanoikuyae (SyADH) and Ralstonia sp. (RasADH) could also accept bulkier keto esters ('bulky-bulky' substrates). SyADH also provided preferentially syn-(2R,3S) isomers and RasADH showed in some cases good selectivity towards the formation of anti-(2S,3S) derivatives. With anti-Prelog ADHs such as LBADH from L. brevis or LKADH from L. kefir, syn-(2S,3R) alcohols were obtained with high conversions and diastereomeric excess in some cases, especially with LBADH. Furthermore, due to the thermodynamically favoured reduction of these substrates, it was possible to employ just a minimal excess of 2-propanol to obtain the final products with quantitative conversions. Copyright
- Cuetos, Anibal,Rioz-Martinez, Ana,Bisogno, Fabricio R.,Grischek, Barbara,Lavandera, Ivan,De Gonzalo, Gonzalo,Kroutil, Wolfgang,Gotor, Vicente
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supporting information; body text
p. 1743 - 1749
(2012/07/28)
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- Desymmetrizing asymmetric ring expansion of cyclohexanones with α-diazoacetates catalyzed by chiral aluminum Lewis acid
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Chiral aluminum Lewis acid catalyst composed of Me3Al and 3,3′-bis(trimethylsilyl)-BINOL in a 2:1 ratio was found to promote novel catalytic asymmetric ring expansion of cyclohexanone with α-substituted α-diazoacetates to give seven-membered rings with an all-carbon quaternary center. Application of this strategy to 4-substituted cyclohexanones opened up a novel way for the catalytic desymmetrizing asymmetric construction of cycloheptanones bearing remote α,δ-chiral centers.
- Hashimoto, Takuya,Naganawa, Yuki,Maruoka, Keiji
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supporting information; experimental part
p. 8834 - 8837
(2011/08/03)
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- Synthesis of amino-1,4-benzoquinones and their use in Diels - Alder approaches to the aminonaphthoquinone antibiotics
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A new protocol for the synthesis of protected amino-1,4-benzoquinones by oxidation of the corresponding 2,5-dimethoxyaniline derivatives using PhI(OAc)2 or PhI- (OCOCF3)2 in water containing 2.5% methanol is reported. The process represents an improvement over previously reported methods, both in terms of yield and number of steps, and in the range of nitrogen protecting groups that it tolerates. A number of novel aminobenzoquinones were prepared and subsequently used as dienophiles in Diels - Alder reactions to (Figure presented) form building blocks for the synthesis of the aminonaphthoquinone antibiotics such as salinisporamycin.
- Nawrat, Christopher C.,Lewis, William,Moody, Christopher J.
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experimental part
p. 7872 - 7881
(2011/12/14)
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- Dynamic kinetic resolution of α-substituted β-ketoesters catalyzed by Baeyer-Villiger monooxygenases: Access to enantiopure α-hydroxy esters
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BVMOs make a play: The dynamic kinetic resolution of racemic α-alkyl-β-ketoesters was performed through a selective Baeyer-Villiger oxidation employing different Baeyer-Villiger monooxygenases (BVMOs) in mild basic media. The product diesters were obtained with excellent yields and enantioselectivities, and used as precursors for optically active α-hydroxy esters.
- Rioz-Martínez, Ana,Cuetos, Aníbal,Rodríguez, Cristina,De Gonzalo, Gonzalo,Lavandera, Iván,Fraaije, Marco W.,Gotor, Vicente
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supporting information; experimental part
p. 8387 - 8390
(2011/10/09)
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- The first enantioselective synthesis of cytotoxic marine natural product palau'imide and assignment of its C-20 stereochemistry
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Methyl tetramate derivative 6 has been developed as a new building block for the flexible and racemization-free synthesis of methyl 5-benzyl-3- methyltetramate via alkylation, and used in the first asymmetric synthesis of palau'imide (1). This allowed the establishment of the hitherto unknown stereochemistry at the C-20 of palau'imide as S.
- Lan, Hong-Qiao,Ruan, Yuan-Ping,Huang, Pei-Qiang
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supporting information; scheme or table
p. 5319 - 5321
(2010/09/03)
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- Cerium-catalyzed α-hydroxylation reactions of α-cyclopropyl β-dicarbonyl compounds with molecular oxygen
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Three α-cyclopropyl β-dicarbonyl compounds have been used as probes for α-radicals as electrophilic reaction intermediates in a cerium-catalyzed α-hydroxylation reaction with molecular oxygen. Since the cyclopropyl group did not ring-open to products with a butenyl moiety, but was retained in the products, a localized unpaired electron at the α position can be excluded during the course of the reaction. The α-cyclopropyl- substituted substrates were prepared by aldol or Claisen reactions. Other substrates with α-methyl, α-isopropyl, and α-tert-butyl substituents were prepared and converted under the α-hydroxylation conditions in order to estimate steric influences on the yield of the reaction. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Christoffers, Jens,Kauf, Thomas,Werner, Thomas,Roessle, Michael
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p. 2601 - 2608
(2007/10/03)
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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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- Syntheses and kinetic evaluation of racemic and optically active 2-benzyl-2-methyl-3,4-epoxybutanoic acids as irreversible inactivators for carboxypeptidase A
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Racemic and optically active 2-benzyl-2-methyl-3,4-epoxybutanoic acids were synthesized and evaluated as inactivators for carboxypeptidase A, a representative zinc-containing proteolytic enzyme. Only the threo-form of the inactivator is effective and its potency in terms of kinact/KI value is lower by 42-fold compared with 2-benzyl-3,4-epoxybutanoic acid, indicating that the α-methyl group affects adversely in the inactivation contrary to the expectation that it would enhance the inactivation activity of the inhibitor through additional interactions of the methyl group with a small cavity (α-methyl hole) present next to the S1′ hydrophobic pocket. Of the enantiomeric pair, the inactivator having the (2S,3R)-configuration is more potent than its enantiomer by 44-fold. The observed kinetic results may be rationalized on the basis that the methyl group in the inactivator having the (2R,3S)-configuration experiences the van der Waals repulsive interactions with the bottom of the active site crevice in binding to CPA, casting a doubt on the presence of the so-called α-methyl hole at the active site of carboxypeptidase A. Copyright
- Lee, Mijoon,Kim, Dong H.
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p. 913 - 922
(2007/10/03)
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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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- Palladium catalysed conversion of vinyl bromo allylic alcohols into vinylic carbonyl compounds and oxidation of secondary alcohols to ketones
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A variety of vinyl bromo allylic alcohols are converted into the corresponding vinylic carbonyl compounds and secondary alcohols are oxidised into ketones upon treatment with palladium acetate in the presence of potassium carbonate under the typical Heck reaction conditions.
- Pitre, Sangceta V.,Vankar, Padma S.,Vankar, Yashwant D.
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p. 12291 - 12298
(2007/10/03)
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- Stereoselective reduction of 2-methyl-3-oxo esters (or amides) with sodium borohydride catalyzed by manganese (II) chloride or tetrabutylammonium borohydride. A practical preparation of erythro and threo-3-hydroxy-2-methyl esters (or amides)
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erythro-3-Hydroxy-2-methylpropionates or erythro-3-hydroxy-2-methylpropionamides were prepared with high stereoselectivity by NaBH4 reduction of the corresponding 2-methyl-3-oxo esters or 2-methyl-3-oxo amides in the presence of a catalytic amount of manganese(II) chloride. On the other hand, reduction of these substrates with n-Bu4NBH4 provided threo-isomers selectively. erythro-Selective reduction of 2-methyl-3-oxo amides with NaBH3CN in 1N HCl-MeOH is also described.
- Taniguchi, Masahiko,Fujii, Hideaki,Oshima, Koichiro,Utimoto, Kiitiro
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p. 11169 - 11182
(2007/10/02)
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- New method of zinc activation by electrochemistry: synthetic applications to the Blaise reaction
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A new electrochemical zinc metal activation method based on the cathodic reduction of a catalytic amount of zinc bromide in the presence of a zinc anode is described.This procedure is applied to the coupling of α-bromoesters with nitriles, and affords β-ketoesters in good yield.
- Zylber, N.,Zylber, J.,Rollin, Y.,Dunach, E.,Perichon, J.
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- Electrochemical activation of zinc in the coupling reaction of α-bromoesters with carbonyl compounds
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The Reformatsky reaction has been examined using a mild and effective method of electrochemical zinc activation, based on the cathodic reduction of a catalytic amount of zing bromide in acetonitrile.
- Rollin, Y.,Gebehenne, C.,Derien, S.,Dunach, E.,Perichon, J.
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- Direct Observation of α-Oxo Ketenes from the Photolysis of α-Diazo β-Diketones
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Monitoring by IR spectroscopy of the broad-band irradiation of the symmetrically substituted 2-diazocyclohexane-1,3-dione (11), 3-diazopentane-2,4-dione (19), and 4-diazo-2,2,6,6-tetramethylheptane-3,5-dione (24) in Ar matrices at 12 K showed the formation of 2-carbonylcyclopentanone (s-Z-12), acetyl(methyl)ketene (s-E-20), and tert-butyl(pivaloyl)ketene (s-E-25), respectively, in less than 10 min.On increasing the photolysis time to >3 h, the α-oxo ketenes 12, 20, and 25 decarbonylated to the corresponding oxocarbenes which underwent Wolff rearrangement to carbonylcyclobutane (15), dimethylketene (23), and di-tert-butylketene (28), respectively.The reaction of 2-carbonylcyclopentanone (12) with CH3OH was monitored by IR spectroscopy.Thus, it was found that the reaction started at ca. 100 K and was essentially complete at 140 K, involving the initial formation of the enol form (9) of methyl 2-oxocyclopentanecarboxylate.
- Leung-Toung, Regis,Wentrup, Curt
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p. 4850 - 4858
(2007/10/02)
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- Preparation of β-Keto Ester Acetals by Reaction of Ortho Esters with Ketene Silyl Acetals in the Presence of Titanium Tetrachloride
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Reaction of 2-ethoxy-2-methyl-1,3-dioxolan (1c) with 1-methoxy-1-trimethylsilyloxyethene (4a) in dichloromethane in the presence of titanium tetrachloride gave 62percent of methyl 2-(2'-methyl-1',3'-dioxolan-2'-yl)acetate (5a).Similarly, reaction of (1c) with 1-methoxy-1-trimethylsilyloxyprop-1-ene (4b) afforded 73percent of methyl 2-(2'-methyl-1',3'-dioxolan-2'-yl)propanoate (5b).
- Collins, David J.,Choo, Gabrielyn Lee Poh,Obrist, Hans
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p. 617 - 622
(2007/10/02)
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- Stereochemical Control in Microbial Reduction. 9. Diastereoselective Reduction of 2-Alkyl-3-oxobutanoate with Bakers' Yeast
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Bakers' yeast reduces esters of 2-alkyl-3-oxobutanoic acid (CH3COCHRCO2R'; R=methyl, ethyl, propyl, propargyl, and allyl) into the corresponding (S)-hydroxy esters with exclusive stereoselectivity, while the configuration at the 2-position of the hydroxy esters is either S (anti) or R (syn) depending on the structure of the alkoxyl group in the carboalkoxyl moeity of the ester.Oftently, the stereoselectivity with respect to the 2-position is not satisfactory.In general, the reduction of t-butyl esters exerts predominancy in the products, whereas that of 1,1-dimethylpropyl esters exerts the syn predominancy.A marked difference between these two esters in diastereoselectivity is dicussed from the view point of plausible conformations of the esters.
- Nakamura, Kaoru,Miyai, Takehiko,Nagar, Ashish,Oka, Shinzaburo,Ohno, Atsuyoshi
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p. 1179 - 1187
(2007/10/02)
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- Synthesis of α-substituted γ,δ-unsatured β-oxo esters
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Two approaches to the synthesis of the title compounds 3 are described.The first consist of direct alkylation of the unsatured β-oxo esters 1 via their monoanions.The best results were obtained using the heterogeneous sodium methoxide/alumina system.Isolation of pure, mono-α-alkylated compounds requires chromatographic separation of the reaction products.The second approach makes use of the Horner-Wittig reaction. α-substituted phosphine oxides 4 were converted into their dianions and reacted with aldehydes and ketones to afford the mono-α-alkylated β-oxo esters 3 in good yields.The requisite phosphine oxides were obtained from the corresponding γ-bromo β-oxo esters 10 via an Arbusov reaction with ethyl diphenylphosphinite.Finally, it was found that α,α-dialkylated and α,α,γ-trialkylated β-oxo esters 8 and 15 can be obtained by reaction of 1 with an excess of alkyl halide in the presence of two or four equivalents of sodium hydride, respectively.
- Goorbergh, J. A. M. van den,Gen, A. van der
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- The Allopolarization Principle and its Applications, IV. Substituent Effects in the Methylation of Enolate Anions
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The ratio of O- and C-methylated products in the reaction of the sodium salts of acetophenones 1, propiophenones 3, phenylacetones 5, β-dicarbonyl compounds 12, α-cyanocarbonyl compounds 13, acetaldehyde, propionaldehyde, and diethylketone with dimethyl sulfate, methyl iodide, and trimethyl phosphate in HMPTA has been determined with regard to the effect of substituents.In some cases the influence of solvents, concentration and temperature has also been studied.
- Gompper, Rudolf,Vogt, Hans-Hubert
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p. 2866 - 2883
(2007/10/02)
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- The Allopolarization Principle and its Applications, VI. The Alkylation of Enolate Anions: Polarity and Regioselectivity
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The O/C methylation ratio in the reaction of sodium enolates with dimethylsulfate depends on the polar (electronic) effect of substituents.The relative ?-charge density Px/y = lx/ly can be used as a measure for the polarity of ambifunctional anions; in case of enolate anions PO/C = lO/lC.The change of the regioselectivity Sf = log QO/QC in the alkylation of enolates is a function of a change in the polarity PO/C; ΔSf=f(ΔPx/y).The polar effect of substituents influences the charge control during the alkylation process via a change of the polarity of the enolate system: The higher the polarity of the anion, the stronger the charge control and the higher the yield of enol ether (O-alkylation). - Keywords: Alkylation, Enolate Anions
- Gompper, Rudolf,Vogt, Hans-Hubert,Wagner, Hans-Ulrich
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p. 1644 - 1652
(2007/10/02)
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- α-Carboxylation reaction of carbonyl compounds with bromomagnesium ureide-carbon dioxide adducts
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Bromomagnesium ureide-carbon dioxide adducts, models of the carboxylated biotin complex, undergo caboxylation of a variety of carbonyl compounds in good yield.
- Sakurai, Hideki,Shirahata, Akihiko,Hosomi, Akira
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p. 1967 - 1970
(2007/10/02)
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