- Gold N-Heterocyclic Carbene Catalysts for the Hydrofluorination of Alkynes Using Hydrofluoric Acid: Reaction Scope, Mechanistic Studies and the Tracking of Elusive Intermediates
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An efficient and chemoselective methodology deploying gold-N-heterocyclic carbene (NHC) complexes as catalysts in the hydrofluorination of terminal alkynes using aqueous HF has been developed. Mechanistic studies shed light on an in situ generated catalyst, formed by the reaction of Br?nsted basic gold pre-catalysts with HF in water, which exhibits the highest reactivity and chemoselectivity. The catalytic system has a wide alkyl substituted-substrate scope, and stoichiometric as well as catalytic reactions with tailor-designed gold pre-catalysts enable the identification of various gold species involved along the catalytic cycle. Computational studies aid in understanding the chemoselectivity observed through examination of key mechanistic steps for phosphine- and NHC-coordinated gold species bearing the triflate counterion and the elusive key complex bearing a bifluoride counterion.
- Bédard, Sandrine,Cavallo, Luigi,Falivene, Laura,Gauthier, Rapha?l,Nolan, Steven P.,Paquin, Jean-Fran?ois,Saab, Marina,Tzouras, Nikolaos V.,Van Hecke, Kristof,Zhang, Ziyun
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- Hypervalent Iodine as a Terminal Oxidant in Wacker-Type Oxidation of Terminal Olefins to Methyl Ketones
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A mimic of the Wacker process for C=O bond formation in terminal olefins can be initiated by a combination of the Pd(II) and hypervalent iodine reagent, Dess-Martin periodinane to generate methyl ketones. This operationally simple and scalable method offers Markovnikov selectivity, has good functional group compatibility, and is mild and high yielding.
- Chaudhari, Dipali A.,Fernandes, Rodney A.
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p. 2113 - 2121
(2016/03/15)
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- Tsuji-Wacker Oxidation of Terminal Olefins using a Palladium-Carbon Nanotube Nanohybrid
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Palladium nanoparticles supported on carbon nanotubes were used in the Tsuji-Wacker oxidation. The palladium-based nanohybrid was found to be very active in combination with cuprous chloride for the selective oxidation of terminal olefins into methyl ketones. The co-catalytic system operates under very mild and sustainable conditions (room temperature, atmospheric pressure, low catalyst loading), as opposed to previously reported catalysts, and can be recycled without any loss in activity. Give it a whack: Palladium nanoparticles supported on carbon nanotubes are used in combination with cuprous chloride for the selective Tsuji-Wacker oxidation of terminal olefins into methyl ketones. The co-catalytic system operates under very mild and sustainable conditions and can be recycled without any loss in activity.
- Donck, Simon,Gravel, Edmond,Shah, Nimesh,Jawale, Dhanaji V.,Doris, Eric,Namboothiri, Irishi N. N.
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p. 2318 - 2322
(2015/08/11)
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- Synthesis of methyl ketones from terminal olefins using PdCl 2/CrO3 system mimicking the Wacker process
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An efficient synthesis of methyl ketones from terminal olefins using PdCl2/CrO3 system mimicking the Wacker process is developed. The method shows good functional groups compatibility, no aldehyde by-products and is operationally simple. CrO3 is the sole oxidant and replaces both Cu-salts and molecular oxygen, traditionally used in this process. The method holds potential for future applications in organic synthesis.
- Fernandes, Rodney A.,Bethi, Venkati
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p. 4760 - 4767
(2014/06/24)
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- Iron(III) sulfate as terminal oxidant in the synthesis of methyl ketones via wacker oxidation
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An efficient and environmentally benign method using Fe(III) sulfate as a terminal oxidant in the synthesis of methyl ketones from terminal olefins via the Wacker process is developed. The methodology offers high selectivity for a Markonikov product, shows good functional group compatibility, involves mild reaction conditions, and is operationally simple. Fe2(SO 4)3 is the sole terminal oxidant in this process. The method holds potential for future applications in organic synthesis.
- Fernandes, Rodney A.,Chaudhari, Dipali A.
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p. 5787 - 5793
(2014/07/08)
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- Greening the Wacker process
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Wacker oxidation of various terminal olefins with Pd0/C- KBrO3, a nontoxic, environmentally benign, and easy to handle catalyst system, was achieved in high isolated yields. The described protocol offers an alternative to the traditional Wacker system which uses CuCl 2 as co-catalyst. The catalyst is reusable while maintaining high activity and selectivity.
- Kulkarni, Mukund G.,Shaikh, Yunnus B.,Borhade, Ajit S.,Chavhan, Sanjay W.,Dhondge, Attrimuni P.,Gaikwad, Dnyaneshwar D.,Desai, Mayur P.,Birhade, Deekshaputra R.,Dhatrak, Nagorao R.
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supporting information
p. 2293 - 2295
(2013/06/26)
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- Palladium-catalyzed asymmetric quaternary stereocenter formation
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An efficient palladium catalyst is presented for the formation of benzylic quaternary stereocenters by conjugate addition of arylboronic acids to a variety of β,β-disubstituted carbocyclic, heterocyclic, and acyclic enones. The catalyst is readily prepared from PdCl2, PhBOX, and AgSbF 6, and provides products in up to 99 % enantiomeric excess, with good yields. Based on this strategy, (-)-α-cuparenone has been prepared in only two steps. Copyright
- Gottumukkala, Aditya L.,Matcha, Kiran,Lutz, Martin,De Vries, Johannes G.,Minnaard, Adriaan J.
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supporting information; experimental part
p. 6907 - 6914
(2012/07/01)
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- Copper(I)-catalyzed asymmetric desymmetrization: Synthesis of five-membered-ring compounds containing all-carbon quaternary stereocenters
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A highly stereoselective catalytic alkylation sequence for the synthesis of highly functionalized and versatile five-membered-ring compounds bearing all-carbon quaternary stereocenters was developed. Enantioselective desymmetrization of achiral cyclopentene-1,3-diones was thus executed by chiral Cu-phosphoramidite catalysts. A variety of complicated cyclopentane derivatives can be synthesized with excellent stereoselectivities using a low catalyst loading in a one-pot operation.
- Aikawa, Kohsuke,Okamoto, Tatsuya,Mikami, Koichi
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supporting information; experimental part
p. 10329 - 10332
(2012/07/30)
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- Pd(0)/C catalyzed efficient Wacker oxidation of functionalized terminal olefins
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Wacker oxidation of terminal olefins was carried out at room temperature and atmospheric pressure by using Pd(0)/C in THF/H2O (9:1). Palladium(0)/C was proven to be highly efficient catalyst for the Wacker oxidation of terminal olefins to the corresponding methyl ketones. The catalyst was reusable while maintaining its activity and selectivity to a high degree.
- Kulkarni, Mukund G.,Bagale, Sharanappa M.,Shinde, Mahadev P.,Gaikwad, Dnyaneshwar D.,Borhade, Ajit S.,Dhondge, Attrimuni P.,Chavhan, Sanjay W.,Shaikh, Yunnus B.,Ningdale, Vijay B.,Desai, Mayur P.,Birhade, Deekshaputra R.
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experimental part
p. 2893 - 2894
(2009/09/06)
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- Process for preparing optically active secondary alcohols having nitrogenous or oxygenic functional groups
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A process for preparing optically active secondary alcohols of the general formula (3), [wherein R1 is linear lower alkyl, an aromatic ring group, or the like; A is CH2NR2R3 or the like; n is an integer of 0 to 2; and * represents an asymmetric carbon atom] by asymmetrically hydrogenating a ketone compound of the general formula (1) having nitrogenous or oxygen functional group at any of the a-, β- and γ-positions, with selectivity among functional groups by the use of a ruthenium/optically active bidentate phosphine/diamine complex as the catalyst in the presence of hydrogen alone or together with a base. The optically active secondary alcohols obtained by the process are useful as drugs and intermediates for the preparation of drugs.
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- Guanidine mimics as factor Xa inhibitors
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The present application describes nitrogen containing heteroaromatics and derivatives thereof of formula I: or pharmaceutically acceptable salt forms thereof, wherein rings D—E represent guanidine mimics, which are useful as inhibitors of factor Xa.
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Page column 69-72
(2010/02/04)
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- Syntheses of α,β-unsaturated carbonyl compounds from the reactions of monosubstituted ozonides with stable phosphonium ylides
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Ozonides derived from terminal alkenes reacted with 1.3 mol equiv. of stable phosphonium ylides to give (E)-αβ-unsaturated carbonyl compounds in good to excellent yields. No reducing agent is needed in the reaction. However, alkoxyalkyl-substituted ozonides afforded a mixture of (Z)- and (E)-αβ-unsaturated carbonyl compounds under similar condition. The E/Z isomeric ratio is affected by the position of the heteroatom in the substituent of the ozonides. The possible mechanism of this reaction will be discussed. (C) 2000 Elsevier Science Ltd.
- Hon, Yung-Son,Lu, Ling,Chang, Rong-Chi,Lin, Sheng-Wun,Sun, Pei-Pei,Lee, Chia-Fu
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p. 9269 - 9279
(2007/10/03)
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- Amino acid analogs for tumor imaging
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The invention provides novel amino acid compounds of use in detecting and evaluating brain and body tumors. These compounds combine the advantageous properties of 1-amino-cycloalkyl-1-carboxylic acids, namely, their rapid uptake and prolonged retention in tumors with the properties of halogen substituents, including certain useful halogen isotopes including fluorine-18, iodine-123, iodine-125, iodine-131, bromine-75, bromine-76, bromine-77 and bromine-82. In one aspect, the invention features amino acid compounds that have a high specificity for target sites when administered to a subject in vivo. Preferred amino acid compounds show a target to non-target ratio of at least 5:1, are stable in vivo and substantially localized to target within 1 hour after administration. An especially preferred amino acid compound is ?18 F!-1-amino-3-fluorocyclobutane-1-carboxylic acid (FACBC). In another aspect, the invention features pharmaceutical compositions comprised of an α-amino acid moiety attached to either a four, five, or a six member carbon-chain ring. In addition, the invention features analogs of α-aminoisobutyric acid.
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- Amino acid analogs for tumor imaging
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The invention provides novel amino acid compounds of use in detecting and evaluating brain and body tumors. These compounds combine the advantageous properties of 1-amino-cycloalkyl-1-carboxylic acids, namely, their rapid uptake and prolonged retention in tumors with the properties of halogen substituents, including certain useful halogen isotopes including fluorine-18, iodine-123, iodine-125, iodine-131, bromine-75, bromine-76, bromine-77 and bromine-82. In one aspect, the invention features amino acid compounds that have a high specificity for target sites when administered to a subject in vivo. Preferred amino acid compounds show a target to non-target ratio of at least 5:1, are stable in vivo and substantially localized to target within 1 hour after administration. An especially preferred amino acid compound is ?18 F!-1-amino-3-fluorocyclobutane-1-carboxylic acid (FACBC). In another aspect, the invention features pharmaceutical compositions comprised of an α-amino acid moiety attached to either a four, five, or a six member carbon-chain ring. In addition, the invention features analogs of α-aminoisobutyric acid.
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- Synthesis of α,α-disubstituted-α-amino acids by double nucleophilic addition to cyanohydrins
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The synthesis of tertiary carbinamines was achieved by the double nucleophilic addition of Grignard reagents to cyanohydrins. Titanium isopropoxide was found to promote the process. In a typical example, the rapid conversion of a carbinamine to the corespondlng α,α-disubstituted- α-amino acid was also demonstrated.
- Charette, Andre B.,Gagnon, Alexandre,Janes, Marc,Mellon, Christophe
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p. 5147 - 5150
(2007/10/03)
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- The mechanistic study and synthetic applications of the base treatment in the ozonolytic reactions
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The E1cb mechanism is the overwhelming process in the reaction of bases and ozonides. As a quenching agent in the ozonolysis of a variety of alkenes, the reactions involving triethylamine often gave better yields and proceeded faster than those involving methyl sulfide. On the other hand, in the presence of 4 A molecular sieves, the secondary amines reacted with mono- and 1,1-di-substituted ozonides to afford the reductive amination products in high yields. The formation of ammonium formate in the reaction mixture also supported the E1cb mechanism in the reaction of ozonide and amine.
- Hon, Yung-Son,Lin, Sheng-Wun,Lu, Ling,Chen, Yao-Jung
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p. 5019 - 5034
(2007/10/02)
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- A convenient and efficient workup of ozonolysis reactions using triethylamine
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Comparisons were made between triethylamine and methyl sulfide for their use as a quenching agent in the ozonolysis of a variety of alkenes. The reactions involving triethylamine often gave better yields and proceeded faster than those of involving methyl sulfide. The role of triethylamine played as base instead of reducing agent in the reaction.
- Hon,Lin,Chen
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p. 1543 - 1553
(2007/10/02)
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- Functional analogs of CC-1065 and the duocarmycins incorporating the 9a-(chloromethyl)-1,2,9,9a-tetrahydrocyclopropa[c]benz[e]indol-4-one (C2BI) alkylation subunit: Synthesis and preliminary DNA alkylation studies
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A concise and effective nine to ten step synthesis of 9a-(chloromethyl)-1,2,9,9a-tetrahydrocyclopropa[c]benz[e]indol-4-one (C2BI) is detailed based on the implementation of a key 5-exo-trig aryl radical-alkene cyclization for direct introduction of a selectively protected 3,3-bis(hydroxymethyl)indoline. The incorporation of C2BI into functional analogs of CC-1065 and the duocarmycins (C2BI-COPI1, C2BI-CDPI2, C2BI-TMI, and C2BI-indole2) is described. The fundamental solvolytic behavior of N-BOC-C2BI is detailed (t1/2 = 433 h, pH = 3) in studies which reveal that the agent is approximately 12 times more stable than the authentic alkylation subunit of CC-1065 and that it participates in the stereoelectronically-controlled reaction with nucleophilic addition to the least substituted cyclopropane carbon. Preliminary studies demonstrating the DNA alkylation and cross-linking properties of C2BI-CDPI2 are presented.
- Boger, Dale L.,Palanki, Moorthy S.S.
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p. 9318 - 9327
(2007/10/02)
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- Stereochemically Controlled Bakers'-Yeast-Mediated Reductions: Synthesis of (S)-(+)-1,2-Propanediol and (S)-(-)-1,3-Butanediol, 1-Benzyl Ethers
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Benzyloxyketones 1a and b can be reduced by fermenting bakers' yeast to the corresponding protected (S)-diols 2a and b in 76 and 52percent yields, respectively (90 and >95percent e.e., respectively, as (R)-(+)-MTPA esters).
- Manzocchi, Ada,Fiecchi, Alberto,Santaniello, Enzo
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p. 1007 - 1009
(2007/10/02)
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- Synthetic Studies of Carbohydrate Derivatives by Photochemical Reactions. Part 16. Synthesis of DL-Apiose Derivatives by Photochemical Cycloaddition of 1,3-Dihydroxypropan-2-one Derivatives with Ethenediol or Ethenol Derivatives
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Irradiation of a benzene solution of 1,3-diacetoxypropan-2-one (5) and 1,3-dioxol-2-one (6) with a high-pressure mercury lamp gave a photocycloaddition product, (7-acetoxymethyl-3-oxo-2,4,6-trioxabicycloheptan-7-yl)-methyl acetat (7) (55percent yield).Similar photocycloadditions of (5)with (Z)-vinylene diacetate (23), with (Z)-2-(benzyloxy)vinyl acetate (25), with 2,3-dihydro-1,4-dioxin (27), with vinyl acetate (28), with isopropenyl acetate (29), with ethoxyethene (30), and with 1,1-diethoxyethene (43) afforded cis-4,4-bis(acetoxymethyl)oxetan-2,3-diyl diacetat (31) (46percent yield) and the trans-isomer (32) (49percent yield); 2,2-bis(acetoxymethyl)-4-(benzyloxy)-oxetan-3-yl acetate (33) (composed of the two isomers; 11percent and 26percent yields) and 4,4-bis(acetoxymethyl)-3-benzyloxy)oxetan-2-yl acetate (38) (composed of the two isomers; 11percent and 9percent yields); (8-acetoxymethyl-2,5,7-trioxabicyclooct-8-yl)methyl acetate (34) (25percent yield); 2,2-bis(acetoxymethyl)oxetan-3-yl acetate (35) (28percent yield) and 4,4-bis(acetoxymethyl)oxetan-2-yl acetate (39) (15percent yield); 2,2-bis(acetoxymethyl)-3-methyloxetan-3-yl acetate (36) (55percent yield); (2-acetoxymethyl-3-ethoxyoxetan-2-yl)methyl acetate (37) (53percent yield); and (2-acetoxymethyl-3,3-diethoxyoxetan-2-yl)methyl acetate (44) (48percent yield) and ethyl 4-acetoxy-3-acetoxymethyl-3-hydroxybutyrate (45) (19percent yield), respectively.The reaction of (5) with (43) was also induced thermally togive ethyl 4-acetoxy-3-(acetoxymethyl)coronate (46) (24percent yield) in addition to (45) (20percent yield).Photocycloaddition of diethyl mesoxalate (21) with (6) gave diethyl 3-oxo-2,4,6-trioxabicycloheptane-7,7-dicarboxylate (22) (23percent yield).On the other hand, the reactions of 1,3-dimethoxy- (8) and 1,3-bis(benzyloxy)-propan-2-one (13) respectively with (6) afforded none of the expected photocycloadducts, but several products due to the intramolecular hydrogen abstraction from (8) and (13).The reaction of 2,2-dimethyl-1,3-dioxan-5-one (2) with (6) was also accompanied by predominant decomposition of (20).
- Araki, Younosuke,Nagasawa, Jun-ichi,Ishido, Yoshiharu
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