- Unexpected formation of 10-iodo- and 10-chlorocamphor under halosulfonylation conditions, and convenient routes to 10-chloro- and 10-bromocamphor
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The generation of camphor-10-sulfonyl iodide in situ under halosulfonylation conditions or exposure of camphor-10-sulfonyl chloride to copper(II) chloride under Asscher-Vofsi conditions leads unexpectedly to the formation of 10-iodocamphor or 10-chlorocamphor, respectively. Additionally, convenient syntheses of 10-bromocamphor and 10-chlorocamphor have been achieved by extension of a previously reported methodology.
- Lewis, Frank W.,Egron, Gilles,Grayson, David H.
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- Synthesis and characterization of camphorsulfonyl acetate of cellulose
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Novel cellulose derivatives were prepared from reacting (1R)-(+)-camphor-10-sulfonic chloride (CSC) with cellulose acetate (CA) in acetone and triethylamine. The reaction conditions, including reaction time and reactant molar ratios, were optimized. The structure of the products was confirmed by means of 1H NMR, 13C NMR, FT-IR and elementary analysis. The techniques were also used to determine the degree of the substitution of camphorsulfonyl groups (DSCS). The data calculated from 1H NMR, 13C NMR, percent grafting (G%) and elementary analysis coincided with those from chemical analysis. Compared to cellulose acetate, the cellulose derivatives exhibited decreased thermal stability, improved solubility in organic solvents and enhanced enantioselectivity towards tyrosine isomers. The solubility and enantioselectivity increased with increasing degrees of camphorsulfonyl substitution.
- Xiao, Dingshu,Hu, Jiwen,Zhang, Mingqiu,Li, Mingwei,Wang, Guozhi,Yao, Haisong
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- Chiral Polysiloxane-Fixed Metal 1,3-Diketonates (Chirasil-Metals) as Catalytic Lewis Acids for a Hetero Diels-Alder Reaction -Inversion of Enantioselectivity upon Catalyst-Polymer Binding
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A dimethylpolysiloxane chain is covalently bound to the monomeric Lewis acid catalyst (lR)-(+)-oxovanadium(IV) bis[3heptafluorobutanoylcamphorate] [(+)-5a] at the C-10 position of the camphor moiety yielding the novel chiral polymeric (1S)-(+)-oxovanadium(IV) bis[3-heptafluorobutanoylcamphoratej-dimethylpolysiloxane [(+)-6a][1]. The Lewis acid promoted hetero Diels-Alder reaction of //ans-l-methoxy-3(trimethylsilyloxy)-l,3-butadiene (1) and benzaldehyde (2) is studied in the presence of the enantiomerically pure monomeric (5a, 5b) and polymeric (6a, 6b) catalysts. The monomeric and polymeric catalysts of identical chirality'1' invoke opposite enantioselectivities toward the formation of 2-phenyl2,3-dihydro-4H-pyrone (4). This remarkable result is corroborated by numerous control experiments. Thus, it is demonstrated that the environment of the active site of the catalyst is changed when the complex is fixed to a polymeric chain. In contrast to 5 and 6, the monomeric 12 and polymeric 13 europium(HI) tris[3-heptafluorobutanoylcamphorates] of identical chirality invoke the same enantioselectivity toward the formation of 4. The concept of polymer attachment is utilized to recover the catalyst from the reaction mixture by precipitation and to recycle it for subsequent catalytic runs. VCH Verlagsgcscllschaft mbH,.
- Keller, Fritz,Weinmann, Hilmar,Schurig, Volker
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- Modeling of the Diels-Alder reaction enantioselectivity by quantum mechanics and molecular mechanics
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The enantioselectivity of the Diels-Alder reaction between (E)-3-(4-nitrophenyl)-1-(pyridin-3-yl)prop-2-en-1-one and cyclopenta-1,3-diene in the chiral ionic liquids 3-butyl-1-methylimidazolium (S)-camphorsulfonate and (S)-1-methyl-3-(pyrrolidin-2-ylmethyl)- imidazolium tosylate or upon chiral promotion with chiral oxazaborolidine was modeled by molecular and quantum mechanics and then experimentally studied; computations were in good agreement with the experimental data, resulting in no stereoselectivity with a chiral ionic liquid used as a co-solvent and prominent stereoselectivity upon chiral promotion.
- Zeifman, Alexey A.,Stroylov, Viktor S.,Titov, Ilya Yu.,Novikov, Fedor N.,Stroganov, Oleg V.,Svitanko, Igor V.,Chilov, Ghermes G.
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- Synthesis of (1S)-(+)-camphor-10-sulfonic acid derivatives and investigations in vitro and in silico of their antiviral activity as the inhibitors of fi lovirus infections
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N-Heterocycle-containing (1S)-(+)-camphor-10-sulfonamide derivatives were synthesized. Their antiviral activity against the Ebola and Marburg viruses was estimated using a pseudovirus system based on the vesicular stomatitis virus. The derivatives bearing morpholine and triazole moieties demonstrated the highest inhibitory activity towards the Ebola virus glycoprotein. A moderate activity against the Marburg virus was found for a compound containing the piperidine moiety. A molecular modeling of the interaction between the synthesized derivatives and the binding site of glycoprotein of the Ebola virus was performed.
- Sokolova,Baranova,Yarovaya,Baev,Polezhaeva,Zybkina,Shcherbakov,Tolstikova,Salakhutdinov
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- Synthesis, surface and antimicrobial properties of some quaternary ammonium homochiral camphor sulfonamides
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A group of homochiral quaternary ammonium sulfonamides bearing hydrophobic camphor derived moieties were synthesized and characterized. The described synthetic procedure is quick and efficient. The novel quaternary ammonium bromides were tested as antimicrobial and antifungal agents. They exhibited strong antimicrobial and also antifungal activity, especially N-{2-[((1S, 4R)-7,7-dimethyl-2-oxobicyclo[2.2.1]heptan-1-yl)methylsulfonamido] ethyl}-N,N-dimethyltetradecan-1-aminium bromide 1c. The surface properties of prepared compounds were evaluated by surface tension measurements and critical micelle concentration (CMC) with surface tension at CMC (γCMC) was calculated.
- Miklá?,Miklá?ová,Bukovsky,Horváth,Kubincová,Devínsky
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- First study of rhodium(I) complexes with chiral sulfur-containing terpenoids as catalytic systems for ketone hydrosilylation
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Using a “chiral pool” approach, a number of chiral thiolate and sulfide ligands based on natural terpenes and terpenoids have been synthesized in a few simple steps. Two new Rh-thiolate complexes with the formula [Rh(CO)2(μ-SR)]2 were obtained. The influence of these complexes and catalytic systems formed by combining the synthesized ligands with [Rh(CO)2(μ-Cl)]2 and [Rh(cod)(μ-Cl)]2, on the reaction rate, chemoselectivity, stereoselectivity and formation of tetraphenyldisiloxane in Rh-catalyzed asymmetric hydrosilylation of acetophenone as a model reaction have been studied. Mechanistic aspects of formation of silyl enol ether as a side product in the presence of S-containing ligands are presented.
- Uvarov, Vladimir M.,de Vekki, Dimitry A.
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p. 376 - 387
(2019/12/24)
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- New chemical agents based on adamantane-monoterpene conjugates against orthopoxvirus infections
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Currently, the spectrum of agents against orthopoxviruses, in particular smallpox, is very narrow. Despite the fact that smallpox is well controlled, there is, for many reasons, a real threat of epidemics associated with this or a similar virus. In order to search for new low molecular weight orthopoxvirus inhibitors, a series of amides combining adamantane and monoterpene moieties were synthesized using 1- and 2-adamantanecarboxylic acids as well as myrtenic, citronellic and camphorsulfonic acids as acid components. The produced compounds exhibited high activity against the vaccinia virus (an enveloped virus belonging to the poxvirus family), which was combined with low cytotoxicity. Some compounds had a selectivity index higher than that of the reference drug cidofovir; the highest SI = 1123 was exhibited by 1-adamantanecarboxylic acid amide containing the (-)-10-amino-2-pinene moiety. The produced compounds demonstrated inhibitory activity against other orthopoxviruses: cowpox virus (SI = 30-406) and ectromelia virus (mousepox virus, SI = 39-707). This journal is
- Agafonov, Alexander P.,Bormotov, Nikolay I.,Korchagina, Dina V.,Maksyutov, Rinat A.,Mozhaytsev, Evgenii S.,Salakhutdinov, Nariman F.,Serova, Olga A.,Shishkina, Larisa N.,Suslov, Evgenii V.,Volcho, Konstantin P.,Yarovaya, Olga I.
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p. 1185 - 1195
(2020/11/03)
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- Solid Polymer Electrolytes Comprising Camphor-Derived Chiral Salts for Solid-State Batteries
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Solid polymer electrolytes (SPEs) with both excellent processability and flexibility have been deemed as an auspicious alternative to develop safe solid-state lithium metal (Li°) batteries (SSLMBs). The electrochemical performance of SSLMBs is ultimately associated with the nature of the Li-salt anion and the widely used bis(trifluoromethanesulfonyl)imide anion (TFSI) is "slippery"due to its perfluorinated nature and therefore highly mobile, which leads to severe polarization upon battery cell charge/discharge cycles. In this work, we report on a new type of chiral salts, synthesized from commercially available camphorsulfonic acid, used in poly(ethylene oxide) (PEO)-based SPEs. The impact of the chirality of the anions on the fundamental physical properties of the SPEs is extensively studied in terms of thermal stability, phase transition and ionic conductivity, etc. We demonstrate that the resulting SPEs exhibit agreeable ionic conductivities (ca. 104 S cm1) accompanied by high cation transference numbers (ca. 0.5) at 70 °C. Whether either the R or the S enantiomers are used the ion transport properties are the same, as expected, but rather surprisingly the artificial racemic mixture is within the errors of the measurements just as conductive. We discuss how this opens a new avenue to design novel salts for reaching high-performant SSLMBs.
- Armand, Michel,Johansson, Patrik,Lobato, Elias,Martinez-Ibaez, María,Qiao, Lixin,Sanchez-Diez, Eduardo,Santiago, Alexander,Treskow, Marcel,Zhang, Heng,Zhang, Yan
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- Formation, Alkylation, and Hydrolysis of Chiral Nonracemic N-Amino Cyclic Carbamate Hydrazones: An Approach to the Enantioselective α-Alkylation of Ketones
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The α-alkylation of ketones is a fundamental synthetic transformation. The development of asymmetric variants of this reaction is important given that numerous natural products, drugs, and related compounds exist as α-functionalized ketones or derivatives thereof. We previously reported our preliminary studies on the development of a new enantioselective ketone α-alkylation procedure using N-amino cyclic carbamate (ACC) auxiliaries. In comparison to other auxiliary-based methods, ACC alkylation offers a number of advantages and is both highly enantioselective and high yielding. Herein, we provide a full account of our studies on the enantioselective ACC ketone α-alkylation method.
- Huynh, Uyen,McDonald, Stacey L.,Lim, Daniel,Uddin, Md. Nasir,Wengryniuk, Sarah E.,Dey, Sumit,Coltart, Don M.
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p. 12951 - 12964
(2018/11/30)
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- 2-Azaadamantane N-oxyl (AZADO)/Cu Catalysis Enables Chemoselective Aerobic Oxidation of Alcohols Containing Electron-Rich Divalent Sulfur Functionalities
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The chemoselective oxidation of alcohols containing electron-rich sulfur functionalities (e.g., 1,3-dithianes and sulfides) into their corresponding carbonyl compounds with the sulfur groups can sometimes be a demanding task in modern organic chemistry. A reliable method for this transformation, which features azaadamantane-type nitroxyl radical/copper catalysis using ambient air as the terminal oxidant is reported. The superiority of the developed method was demonstrated by comparing it with various conventional alcohol oxidation methods.
- Sasano, Yusuke,Kogure, Naoki,Nagasawa, Shota,Kasabata, Koki,Iwabuchi, Yoshiharu
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supporting information
p. 6104 - 6107
(2018/09/27)
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- A synthetic S-(+)-tetrahydrofuran-3-methanol method
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The invention discloses a method for synthesizing S-(+)-tetrahydrofuran-3-methanol. The method comprises the following steps: reacting D (+)-10-camphorsulfonic acid with thionyl chloride, so as to obtain D-(+)-10-camphor sulfonyl chloride; reacting D-(+)-10-camphor sulfonyl chloride with (+/-)-tetrahydrofuran-3-methanol, so as to obtain tetrahydrofuran-3-methyl camphor sulphonate; standing tetrahydrofuran-3-methyl camphor sulphonate to crystallize, performing configuration inversion in the crystallization process, so as to obtain tetrahydrofuran-3-methyl camphor sulphonate of single configuration, dissociating the crystal by using a dissociation agent, so as to obtain S-(+)-tetrahydrofuran-3-methanol. By adopting the method, the phenomenon that only 50% of single configuration can be obtained in the chiral resolution process is avoided, the yield is greatly increased, the synthesis route is short, and the operation is simple. The method is mainly applied to synthesis of a midbody, namely, S-(+)-tetrahydrofuran-3-methanol.
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Paragraph 0024; 0025
(2016/12/16)
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- Influence of norbornanone substituents on both the Wagner-Meerwein skeletal rearrangements under sulfonation conditions and the diastereoselectivity of the corresponding N,N′-bis-fumaroyl sultams in uncatalyzed Diels-Alder cycloadditions to cyclopenta-1,3-diene
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The Wagner-Meerwein domino rearrangement of norbornanone skeletons, under sulfonation conditions, is strongly influenced by the absence of a gem-dimethyl moiety at C(7). As a result, sulfonation at C(10) is less efficient due to a divergent pathway in the intermediate double bond formation and/or isomerization. Furthermore, the absence of such a gem-dimethyl moiety in the corresponding norbornane[10,2]sultam derivatives, sterically influences the orientation of the SO(1) and SO(2) substituents, hence on the π-facial steric shielding of the thermodynamically more stable anti-s-cis N-alkenoyl dienophiles. As a consequence, their diastereoselective [4+2] cycloadditions to cyclopenta-1,3-diene, under nonchelating conditions, are not as efficient due to a less pseudo axial SO(1) and the consequent loss of pseudo C 2-symmetry.
- Pia?tek, Anna,Chapuis, Christian
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p. 4247 - 4249
(2013/07/26)
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- Total synthesis of (+)-pentamethylsalvianolic acid C
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The total synthesis of a methylated analogue of (+)-Salvianolic acid C has been achieved. Key aspects of the synthetic route include an economical Cu(i) acetylide coupling, unique carboxyl activation conditions via microwave irradiation and a novel lipase catalysed kinetic resolution of a racemic mixture of secondary alcohol Danshensu. The preparation of this methylated analogue will not only improve the bioavailability, but also enable access to new and wider bioactivity applications for (+)-Salvianolic acid C.
- Alford, Benjamin L.,Huegel, Helmut M.
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supporting information
p. 2724 - 2727
(2013/06/04)
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- Asymmetric transfer hydrogenation of 1-phenyl dihydroisoquinolines using Ru(II) diamine catalysts
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A new [Ru(II)(η6-p-cymene)(1R,2R)-N-((1S,2S)-borneol-10- sulfonyl)-1,2-diphenylethylenediamine] catalyst for the asymmetric transfer hydrogenation of both 1-alkyl and 1-aryl dihydroisoquinolines has been isolated. For the first time in this type of reaction, the catalyst employs an N-alkylsulfonyl group instead of N-arylsulfonyl.
- P?ech, Jan,Václavík, Ji?í,?ot, Petr,Pechá?ek, Jan,Vilhanová, Beáta,Janu??ák, Jakub,Syslová, Kamila,Pa?out, Richard,Maixner, Jaroslav,Zápal, Jakub,Kuzma, Marek,Ka?er, Petr
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- CAMPHOR-DERIVED COMPOUNDS, METHOD FOR MANUFACTURING THE SAME, AND APPLICATION THEREOF
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Camphor-derived compounds are disclosed, which are represented as the following formula (I): wherein R1, R2, R3, and R4 each are defined as described in the specification. In addition, a method for manufacturing the camphor-derived compounds and application thereof are disclosed.
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Page/Page column 6-7
(2012/04/05)
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- Ligand dependence of the synthetic approach and chiroptical properties of a magic cluster protected with a bicyclic chiral thiolate
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Chiral gold clusters stabilised by enantiopure thiolates were prepared, size-selected and characterised by circular dichroism and mass spectrometry. The product distribution is found to be ligand dependent. Au25 clusters protected with camphorthiol show clear resemblance of their chiroptical properties with their glutathionate analogue. The Royal Society of Chemistry 2012.
- Knoppe, Stefan,Kothalawala, Nuwan,Jupally, Vijay Reddy,Dass, Amala,Buergi, Thomas
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supporting information; experimental part
p. 4630 - 4632
(2012/06/15)
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- Straightforward synthesis of poly(dimethylsiloxane) phases with immobilized (1R)-3-(perfluoroalkanoyl)camphorate metal complexes and their application in enantioselective complexation gas chromatography
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A straightforward synthesis of novel chiral polysiloxane-based metal stationary phases immobilized through a propylenoxy linker (Chirasil-Metal- OC3) to the polymeric backbone is presented. Synthesis was accomplished in six steps with high overall yields starting from commercially available, enantiopure (+)-(1S)-camphorsulfonic acid. Two different approaches towards Chirasil-Metal phases featuring either a propylenoxy or propylenthio linker used for immobilization through hydrosilylation are presented. Furthermore, a new protocol for the fluoroacylation, which is one of the key steps in the synthesis of (1R)-3-(perfluoroalkanoyl)camphorate metal complexes, was developed to improve the isolation and overall yield. The immobilization of (1R,4S)-10-(allyloxy)-3-(heptafluorobutanoyl)camphor -10-(allyloxy)-hfbc -onto polysiloxanes as well as the incorporation of nickel(II), oxovanadium(IV), europium(III), and lanthanum(III) was characterized by FT ATR IR and NMR spectroscopy. Overall, seven different Chirasil-Metal-OC3 polymers with different separation properties were prepared by metal incorporation and variation of the amount of immobilized (1R,4S)-10-(allyloxy)-3- (heptafluorobutanoyl)camphor (10-allyloxy-hfbc: 3.5, 10.2, and 20.0 %). Their performance in enantioselective complexation gas chromatography was systematically studied and excellent enantioselectivity was found for Chirasil-Nickel-OC3. Separation of 29 small-sized compounds, encompassing, among others, epoxides, substituted alkenes and alkynes as well as alcohols and amides, was achieved with high separation factors α. The synthetic strategy, enantiomer separations and thermal stability (up to 160 °C) demonstrates the versatility of the newly derived Chirasil-Metal-OC 3 phases.
- Spallek, Markus J.,Storch, Golo,Trapp, Oliver
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experimental part
p. 3929 - 3945
(2012/10/08)
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- The syntheses of new camphorsulfonylated ligands derived from 2-amino-2'-hydroxy-1,1'-binaphthyl and their enantioselectivities in the addition of dialkylzinc reagents to aldehydes
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A series of new camphorsulfonylated ligands derived from chiral 2-amino-2'-hydroxy-1,1'-binaphthyl (NOBIN) and (+)-camphorsulfonic acid were synthesized by a short and simple synthetic sequence, and their enantioselective catalytic activities were assessed in the nucleophilic addition reaction of dialkylzinc reagents to aldehydes in the presence of titanium tetraisopropoxide. The most efficient ligand, N-hydroxycamphorsulfonylated (S)-NOBIN, gave (S)-addition products with good yields and up to 87% of ee value. The 1H nuclear magnetic resonance (NMR) and 13C NMR results of the titanium titration experiments on this ligand indicate that the most likely catalytic reactive species involved in this catalytic asymmetric addition is a bimetallic titanium complex. A possible catalytic reaction mechanism is proposed. Copyright
- Bian, Guangling,Huang, Huayin,Zong, Hua,Song, Ling
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p. 825 - 832
(2012/11/07)
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- Preliminary investigations on novel camphor-derived chiral sulfones: Completely stereoselective formation of tricyclic β-hydroxy sulfones from 8- and 10-functionalized camphor derivatives
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Some camphor-derived chiral allylic and benzylic sulfones in which the sulfonyl group is located at the C-10, C-9 or C-8 methyl groups of (+)-camphor were synthesized. The C-9 and C-8 substituted sulfones were obtained via Wagner-Meerwein rearrangements of the bicyclic camphor framework. On treatment with LDA, the C-10 and C-8 substituted sulfones cyclized with complete stereoselectivity, affording tricyclic β-hydroxy sulfones whose relative configurations were determined by X-ray crystallography. Tricyclic sulfones 23 and 24 underwent both β-elimination and retro-aldol reactions on further exposure to base. Reduction of the carbonyl group of the C-10 substituted sulfones afforded exo-configured isobornyl sulfones with high stereoselectivity. Reaction of the lithiated isobornyl benzyl sulfone 32 with benzaldehyde generated all four of the possible product diastereomers, of which three were isolated pure by chromatography. Attempted desulfonylation of these diastereomers failed to generate the desired optically active homobenzylic alcohols but the same sulfonyl carbanion trapping/desulfonylation sequence was successful in a model achiral series of compounds.
- Lewis, Frank W.,McCabe, Thomas C.,Grayson, David H.
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supporting information; experimental part
p. 7517 - 7528
(2011/10/12)
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- The Ru-catalyzed enantioselective preparation of chiral halohydrins and their application in the synthesis of (R)-clorprenaline and (S)-sotalol
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The asymmetric transfer hydrogenation of a series of halo-substituted aryl methyl ketones, including those substituted in both α-methyl and aryl rings, was studied for the preparation of chiral halohydrins. Up to 99.7% ee was obtained with 2-chloro-1-(2-chlorophenyl)ethanone as the substrate and Ru-CsDPEN as the catalyst in an HCOONa/H2O system. (R)-Clorprenaline, a drug used in the treatment of respiratory disorders, such as bronchitis and asthma, and (S)-sotalol, a class-III antiarrhythmic compound, were prepared with these chiral halohydrins.
- Lu, Chuanjun,Luo, Zonghua,Huang, Ling,Li, Xingshu
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experimental part
p. 722 - 727
(2011/08/06)
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- METHOD FOR PREPARING 2-MORPHOLINOISOBORNANE- 10-THIOL AND INTERMEDIATES FORMED THEREIN
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A method for preparing 2-morpholinoisobornane-10-thiol is disclosed, which has simplified steps and avoids the use of Na metal. Accordingly, it is advantageous to apply the method in a mass production.
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(2011/11/12)
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- Ring-opening of NH-aziridines with thiols in ionic liquids: Application to the synthesis of aminosulfide catalysts for asymmetric epoxidation of aldehydes
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The ring opening of NH-aziridines with thiols was found to proceed in good yield at room temperature in the presence of an ionic liquid1-butyl-3- methylimidazolium chloride (BMIM chloride). This mild methodology was applied to the synthesis of a camphor-derived chiral aminosulfide. The sulfide was used to generate a sulfur ylide, which effected an asymmetric epoxidation of benzaldehyde (e.r. 85:15, trans:cis 90:10, 87% yield). The amino group enabled easy recovery of the sulfide (98% yield) after the reaction by a simple acid/base extraction. Copyright Taylor & Francis Group.
- Namutebi, Mariam,McGarrigle, Eoghan M.,Aggarwal, Varinder K.
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experimental part
p. 1250 - 1272
(2010/08/21)
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- Remarkable reaction rate and excellent enantioselective direct α-amination of aldehydes with azodicarboxylates catalyzed by pyrrolidinylcamphor-derived organocatalysts
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Remarkable reaction rate and excellent enantioselective direct α-amination of unmodified aldehydes with various azodicarboxylates was catalyzed by pyrrolidinylcamphor organocatalyst 2a (5 mol-%) to provide the desired aminated products with excellent chemical yields and high to excellent levels of enantioselectivity (up to >99%ee) at 0 °C in CH 2Cl2.
- Liu, Pang-Min,Chang, Chihliang,Reddy, Raju Jannapu,Ting, Ying-Fang,Kuan, Hsuan-Hao,Chen, Kwunmin
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body text
p. 42 - 46
(2010/03/24)
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- Synthesis, structure and activity of sulfonamides derived from (+)-camphor in the enantioselective addition of diethylzinc to benzaldehyde
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New chiral sulfonamides derived from (+)-camphor, with different substituents on camphor C2 and sulfonamide N, were synthesized. Their activity was tested in the reaction of Et2Zn addition to benzaldehyde. The yield of the reaction was 44-96%, the enantiomeric excess was 1-69%. Sulfonamides possessing the 2-hydroxyl group gave an excess of 1-(S)-phenylpropanol, while catalysts containing other sulfonamides gave 1-(R)-phenylpropanol as a major product. The best catalytic efficacy was observed for sulfonamides with (R)-C2-OH group, while the use of thioketo- and mercaptosulfonamides resulted in low enantiomeric excess and yields not exceeding 60%. Crystal structures have been determined for sulfonamides with N-benzyl moiety and different substituents on the C2 atom. The structural analysis revealed the presence of intramolecular N?O(C2) and Osulfo?O(C2) H-bonds, what confirms the ability of these molecules to adopt the conformation required for their bidentate coordination to Ti(IV) via the sulfonamide group and substituent at C2. The coordination mode for investigated sulfonamides was determined with the IR spectra for five obtained Ti(IV) complexes and crystal structure analysis of the ligands. The 3D structures of Ti(IV) complex catalysts containing investigated sulfonamides were postulated, which are consistent with the reported chirality of the addition product and observed % ee.
- Kozakiewicz, Anna,Ullrich, Ma?gorzata,We?niak, Miros?aw,Wojtczak, Andrzej
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experimental part
p. 128 - 140
(2010/10/01)
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- Highly diastereo- and enantioselective direct aldol reactions promoted by water-compatible organocatalysts bearing a pyrrolidinyl-camphor structural scaffold
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Efficient synthetic routes have been developed for the synthesis of a series of pyrrolidinyl-camphor containing organocatalysts (1-10). Structural modifications were made by varying the stereo- and electronic properties of the camphor scaffold and the aromatic substituents. These readily tunable and amphiphilic organocatalysts were evaluated for the direct asymmetric aldol reaction of various aromatic aldehydes and cyclohexanone either in organic solvents or in the presence of water. The aldol reaction proceeded smoothly with excellent chemical yields (up to 99%), enantioselectivities (up to 99% ee), and anti-diastereoselectivities (up to 99:1) with a catalytical amount of the bifunctional organocatalysts (20 mol %) under optimal reaction conditions. Mechanistic transition models are proposed and the stereochemical bias of the asymmetric aldol reaction is presented.
- Tzeng, Zheng-Hao,Chen, Hung-Yao,Reddy, Raju Jannapu,Huang, Ching-Ting,Chen, Kwunmin
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experimental part
p. 2879 - 2888
(2009/06/28)
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- Sulfonyl hydrazine as new functionality in organocatalysis: Camphorsulfonyl hydrazine catalyzed enantioselective Aza-Michael addition
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Sulfonyl hydrazine is a new functionality for the Lewis base organocatalysis. Nα-substituted camphorsulfonyl hydrazines (CaSH) are effective organocatalysts for the asymmetric aza-Michael addition to α,β-unsaturated aldehydes with enantioselectivity of up to 90%. Georg Thieme Verlag Stuttgart.
- Chen, Ling-Yan,He, Hao,Pei, Bao-Jian,Chan, Wing-Hong,Lee, Albert W. M.
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scheme or table
p. 1573 - 1577
(2009/12/22)
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- Camphor-derived sulfonylhydrazines: catalysts for Diels-Alder cycloadditions
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Camphor-derived sulfonylhydrazines proved to be very active for organocatalyzed Diels-Alder cycloadditions with cyclopentadiene. Good chemical yields and enantiomeric excesses up to 89% and 88% are obtained for endo/exo adducts.
- Langlois, Yves,Petit, Alain,Rémy, Pauline,Scherrmann, Marie-Christine,Kouklovsky, Cyrille
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body text
p. 5576 - 5579
(2009/04/11)
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- Synthesis of novel chiral Schiff bases and their application in asymmetric transfer hydrogenation of prochiral ketones
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Novel chiral Schiff bases were synthesized from (+)-camphor, and their application to asymmetric transfer hydrogenation of prochiral ketones is described. The asymmetric transfer hydrogenation reaction could afford excellent conversion rates (up to 97.3%) and up to 27.3% enantiomeric excess.
- Zhou, Zhongqiang,Bian, Yongjun
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scheme or table
p. 682 - 687
(2010/11/04)
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- PROCESS FOR THE PREPARATION OF OPTICALLY ACTIVE (4E)-5- HALO-2-ALKYLPENT-4-ENOIC ACIDS AND THEIR ESTER DERIVATIVES
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A process for the preparation of optically active (4E)-5-halo-2-alkylpent-4-enoic acids and their ester derivatives by a stereoselective synthesis which employs camphorsultam as chiral auxiliary is disclosed; in particular methyl (2S, 4E)-5-chloro-2-isopropylpent-4-enoate is prepared, which is a key intermediate in the manufacturing of the new anti-hypertension drug Aliskiren. Furthermore novel N-(5-halo-2-alkylpent-4-enoyl) camphorsultams are provided. A process for the hydrolysis of substituted N-acylcamphorsultams with strong acids is also provided.
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Page/Page column 25
(2008/06/13)
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- PuPHOS and CamPHOS ligands in the intermolecular catalytic pauson-khand reaction
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The first asymmetric intermolecular cobalt-catalyzed Pauson-Khand reaction is described. The use of the hemilabile CamPHOS ligand provides good conversions and selectivity up to 28 % ee. The catalytic process was studied by in situ FT-IR and it was found that both bridged and non-bridged complexes were present in the reaction mixture. Ourresults suggest that recognition between the alkyne substrate and the ligand is essential to attain stereo-control in the catalytic cyclization.
- Lledo, Agusti,Sola, Jordi,Verdaguer, Xavier,Riera, Antoni,Maestro, Miguel A.
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p. 2121 - 2128
(2008/09/18)
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- A practical synthesis of a [2.2.1] bicyclic chiral sulfide for asymmetric transformations
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A substantially improved synthesis of synthetically useful chiral sulfide 1 is described. Starting from (+)-10-camphorsulfonic acid, the chiral sulfide was synthesised on large scale in five steps and 56% overall yield. Significant improvements include the use of Bu3P in place of Ph3P for the reduction of the chlorosulfonyl group to the thiol, allowing removal of phosphine oxide by aqueous extraction and improvements in the photochemistry using either a modified batch reactor or a single pass continuous flow reactor.
- Aggarwal, Varinder K.,Fang, Guangyu,Kokotos, Christoforos G.,Richardson, Jeffery,Unthank, Matthew G.
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p. 11297 - 11303
(2007/10/03)
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- Synthesis of phenyl 2-acryloyloxybornane-10-sulfonate diastereomers
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Several routes to phenyl 2-exo- and 2-endo-acryloyloxybornane-10-sulfonate have been investigated. Preparation of the former product is complicated by concomitant formation of 10-isobornylsultone, while addition of HCl is observed when the alcohol precursors are treated with acryloyl chloride in the presence of Al2O3. An X-ray crystal structure has been determined for one of the chlorinated derivatives.
- Duggan, Andrew R.,Kaye, Perry T.,Caira, Mino R.
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p. 744 - 747
(2007/10/03)
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- A practical large-scale synthesis of (3R,4R)-4-(Hydroxymethyl)pyrrolidin-3- ol via asymmetric 1,3-dipolar cycloaddition
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(3R,4R)-4-(Hydroxymethyl)pyrrolidin-3-ol (1), which is a useful intermediate for the synthesis of various bioactive molecules, has been synthesized in 51% overall yield by 1,3-dipolar cycloaddition reaction from the dipolarophile, (E)-3-benzyloxypropenoyl-(2′S)-bornane-10,2-sultam (5), and the achiral ylide precursor, N-(benzyl)-N-(methoxymethyl)-N- (trimethylsilylmethyl)amine (6), without using chromatography and the subsequent reduction with LAH and catalytic hydrogenation. The diastereomers 7 and 8 were separated by crystallization, and efficient procedures were developed for the subsequent reactions to afford 1.
- Kotian, Pravin L.,Lin, Tsu-Hsing,El-Kattan, Yahya,Chand, Pooran
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p. 193 - 197
(2012/12/24)
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- Total syntheses of epothilones B and D
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A convergent, total synthesis of epothilones B (2) and D (4) is described. The key steps are Normant coupling to establish the desired (Z)-stereochemistry at C12-C13, Wadsworth-Emmons olefination of methyl ketone 28 with the phosphonate ester 8, diastereoselective aldol condensation of aldehyde 5 with the enolate of keto acid derivatives to form the C6-C7 bond, selective deprotection of acid 52, and macrolactonization.
- Jung, Jae-Chul,Kache, Rajashaker,Vines, Kimberly K.,Zheng, Yan-Song,Bijoy, Panicker,Valluri, Muralikrishna,Avery, Mitchell A.
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p. 9269 - 9284
(2007/10/03)
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- Development of new camphor based N,S chiral ligands and their application in transfer hydrogenation
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A new class of N,S-containing chiral compounds based on the camphor scaffold have been synthesised and evaluated as chiral catalysts in the transfer hydrogenation of acetophenone. The best results were achieved using compound 6a as the ligand and [Ir(COD)Cl]2 as the metal precursor.
- Gayet, Arnaud,Bolea, Christelle,Andersson, Pher G.
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p. 1887 - 1893
(2007/10/03)
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- 1,3-oxathiolan-5-ones useful in the production of antiviral nucleoside analogues
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A compound of the formula A, wherein R* is a chiral auxiliary, and where the configuration at the asymmetric carbon atom between oxygen and sulfur is (R), (S), or combinations of (R) and (S), useful in the preparation of enantiomerically enriched 1,3-oxathiolane nucleoside analogues, for example (?)-FTC and 3TC.
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- Synthesis and Crystal Structure of a Novel Camphor Based Thioaceal
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The synthesis of the very first example of a thioacetal containing two camphor skeletons is described. The acetal was prepared by treating 10-mercapto-iso-borneol with camphorquinone and its stereochemistry confirmed by NMR spectroscopy and X-ray crystallography.
- Ravindran, Swarnam S,Skiti, Neliswa,McCleland, Cedric,Barton, Benita,Bacsa, John
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p. 1056 - 1069
(2007/10/03)
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- Stereoselective synthesis of δ-lactones from 5-oxoalkanals via one-pot sequential acetalization, tishchenko reaction, and lactonization by cooperative catalysis of samarium ion and mercaptan
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By the synergistic catalysis of samarium ion and mercaptan, a series of 5-oxoalkanals was converted to (substituted) δ-lactones in efficient and stereoselective manners. This one-pot procedure comprises a sequence of acetalization, Tishchenko reaction and lactonization. The deliberative use of mercaptan, by comparison with alcohol, is advantageous to facilitate the catalytic cycle. The reaction mechanism and stereochemistry are proposed and supported by some experimental evidence. Such samarium ion/mercaptan cocatalyzed reactions show the feature of remote control, which is applicable to the asymmetric synthesis of optically active δ-lactones. This study also demonstrates the synthesis of two insect pheromones, (2S,5R)-2-methylhexanolide and (R)-hexadecanolide, as examples of a new protocol for asymmetric reduction of long-chain aliphatic ketones.
- Hsu,Fang
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p. 8573 - 8584
(2007/10/03)
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- Progress toward the total synthesis of callipeltin A (I): Asymmetric synthesis of (3S,4R)-3,4-dimethylglutamine
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(equation presented) During the total synthesis of the novel cyclic depsipeptide callipeltin A (1), the unit (3S,4R)-3,4-dimethylglutamine, was successfully synthesized by asymmetric Michael addition and subsequent electrophilic azidation. The key feature of this approach is the generation of three adjacent stereogenic centers using the same camphorsultam chiral auxiliary.
- Liang, Bo,Carroll, Patrick J.,Joullie, Madeleine M.
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p. 4157 - 4160
(2007/10/03)
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- Electrogenerated chiral building blocks for diastereoselective amidoalkylation reactions
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Three different electrochemical methods have been applied for the synthesis of chiral building blocks for diastereoselective amidoalkylation reactions. These are A. the direct anodic α-methoxylation of amides and carbamates; B. anodic methoxylative decarboxylation of α-amino acid derivatives (Hofer-Moest reaction) C. indirect NaCl mediated anodic α-methoxylation of α-amino acid derivatives. The application of these building blocks for the synthesis of enantiomerically pure α-amino acids, dichiral 1,2-amino alcohols and chiral 1,3-diamines is described.
- Brungs,Danielmeier,Jakobi,Nothhelfer,Stahl,Zietlow,Steckhan
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p. 575 - 590
(2007/10/03)
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- Synthesis of several novel optically active nitroxyl radicals
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Optically active nitroxyl radicals are prepared from enantiomerically pure bicyclic tempenoids. (-)-Camphoxyl radical (-)-4 derived from commercially available oxazolidinone (-)-1 and (+)-camphoxyl radical (+)-4 derived from (-)-camphene are readily prepared, conformationally rigid, enantiomeric nitroxyl radicals. (-)-Camphorsulphonic acid is used to prepare two additional optically active nitroxyl radicals 9 and 12.
- Braslau, Rebecca,Kuhn, Heiko,Burrill II, Leland C.,Lanham, Kenneth,Stenland, Chris J.
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p. 7933 - 7936
(2007/10/03)
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- Methylenecyclopropanes, XI. - Asymmetric Nickel(0)-Catalyzed Cycloadditions of Methylenecyclopropanes with Chiral Derivatives of Acrylic Acid
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The nickel(0)-catalyzed codimerisation of methylenecyclopropane 1a or 2,2-dimethylmethylenecyclopropane (1b) with the chiral derivatives of acrylic acid 2a-2f leads to the optically active 3-methylenecyclopentanecarboxylic esters 3a, 3c-3f, 4a, and 4c, or amides 3b and 4b in good yields.The diastereomeric excess accesible depends on the steric demand of the chiral auxiliaries, de values up to 98percent can be achieved.Some improvements of the preparation of optically pure auxiliaries are also described.
- Binger, Paul,Brinkmann, Axel,Roefke, Petra,Schaefer, Bernd
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p. 739 - 750
(2007/10/02)
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- AN APPROACH TO THE ENANTIOSELECTIVE SYNTHESIS OF 2-AZABICYCLOHEPT-5-EN-3-ONE(1)
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2-Azabicyclohept-5-en-3-one (1) was obtained with a 13percent enantiomeric excess by hydrolysis of the adduct formed by Diels-Alder addition of cyclopentadiene to the new chiral dienophile (+)-10-camphorsulphonyl cyanide (6) which was prepared in three steps from (+)-10-camphorsulphonic acid (3) in 44percent overall yield.
- Caamano, Olga,Eirin, Ana,Fernandez, Franco,Gomez, Generosa,Uriarte, Eugenio
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p. 2839 - 2842
(2007/10/02)
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- IRIDOIDS : ENANTIOSELECTIVE SYNTHESIS OF LOGANIN VIA AN ASYMMETRIC DIELS-ALDER REACTION
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Starting from (-)-camphor-10-sulfonic acid (5) the crystalline sultam 9 was readily prepared.TiCl4-mediated Diels-Alder addition of the N-crotonyl sultam 11 to cyclopentadiene, crystallization of the resulrting adduct 12 and subsequent reduction gave virtually pure (1S, 4R,5R, 6S)-1 together with recovered auxiliary 9.The loganin precursor 1 was transformed into norbonanone 20, which upon Baeyer-Villiger oxidation led to the suitably substituted cyclopentane 22 from which 1-B-O-methyl loganin aglucone (2) was readily available.
- Vandewalle, M.,Van der Eycken, J.,Oppolzer, W.,Vullioud, C.
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p. 4035 - 4044
(2007/10/02)
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- Reduction of Sulfonic Acids and Related Organosulfur Compounds with Triphenylphosphine-Iodine System
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Arenesulfonic acids, their sodium salts, and alkyl arenesulfonates can be reduced readily to the corresponding arenethiols quantitatively by treatment with a mixture of triphenylphosphine and a catalytic amount of iodine, while alkanesulfonic acids, sulfinic acids, disulfides, thiosulfonic S-esters, and sulfonates are also readily reduced to the corresponding thiols similarly.Upon treatment with a mixture of triphenylphosphine and excess iodine, however, these aliphatic sulfur compounds are converted eventually to the corresponding alkyl iodides.The relative reactivities of these sulfonyl derivatives in the reaction with the triphenylphosphine-iodine system are the following.Aromatic series: ArSO2Cl, ArSO2SAr' > ArSO2H > ArSO3R > ArSO3-HNBu3+ (or PyH+) > ArSO3H > ArSO2SO2Ar >> ArSO2CH2C(CH3)3, ArSO3Ar'.Aliphatic series: RSO2Cl, RSO2SR', RSO2-HNBu3+ > RSO3-HNBu3+ > RSSR, RSO2H > RSO3H > RSH > RSO3R'.In these reactions, the arenesulfonic acids bearing electron-donating substituents can be reduced more readily than those having electron-withdrawing substituents.
- Oae, Shigeru,Togo, Hideo
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p. 3802 - 3812
(2007/10/02)
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- Chemistry of Oxaziridines. 3. Asymmetric Oxidation of Organosulfur Compounds Using Chiral 2-Sulfonyloxaziridines
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Chiral 2-sulfonyloxaziridines, 9-12, afford the best enantioselectivity of any chiral oxidizing reagent for the asymmetric oxidation of sulfides and disulfides to sulfoxides and thiosulfinates, respectively, 5-8 times better than chiral peracids.For asymmetric oxidations using 9-12, the configuration of the oxaziridine three-membered ring was shown to control the configuration of the product, which could be predicted using a chiral recognition mechanism (Figure 2).The increased asymmetric bias exhibited by chiral 2-sulfonyloxaziridines was attrbuted to the fact that the active-site oxygen was incorporated into a rigid chiral environment.The group size difference (GSD) effect in both the oxaziridine and substrate play important roles in determining the absolute configuration of the product and the magnitude of the asymmetric bias.As the GSD increases the enantioselectivity increases.
- Davis, Franklin A.,Jenkins, Robert H.,Awad, Sami B.,Stringer, Orum D.,Watson, William H.,Galloy, Jean
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p. 5412 - 5418
(2007/10/02)
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- Asymmetric Phenol Oxidation. Stereospecific and Stereoselective Oxidative Coupling of a Chiral Tetrahydronaphthol
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The study of the factors which determine the intermolecular asymmetric phenol oxidation shows the importance of the stereochemical control exerted by asymmetry in the substrate.The oxidative coupling of (S)-(+)-2-hydroxy-3,4,8-trimethyl-5,6,7,8-tetrahydronaphthalene ((S)-(+)-1) resulted in the completely stereoselective formation of the optically active dinaphthol (S,S)-(+)-trans-2a.The results argue against the necessity of an asymmetric oxidant in intermolecular phenol coupling reactions.The synthesis of enantiomerically pure (S)-(+)-1 was completed by a six-step route from racemic 7-methoxy-5,6-dimethyl-1,2,3,4-tetrahydro-1-naphthoic acid ((R,S)-16), which was resolved via its (+)-dehydroabietylamine salts.The chiroptical data of the tetrahydronaphthols 1, 10, 16, and 23-25 and of dinaphthol 2a are presented.Diastereomeric charge-transfer interactions, which resulted in long-range asymmetric influences, were observed in amides 27 and 29.
- Feringa, Ben,Wynberg, Hans
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p. 2547 - 2557
(2007/10/02)
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