- Combined Theoretical and Experimental Studies Unravel Multiple Pathways to Convergent Asymmetric Hydrogenation of Enamides
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We present a highly efficient convergent asymmetric hydrogenation of E/Z mixtures of enamides catalyzed by N,P-iridium complexes supported by mechanistic studies. It was found that reduction of the olefinic isomers (E and Z geometries) produces chiral amides with the same absolute configuration (enantioconvergent hydrogenation). This allowed the hydrogenation of a wide range of E/Z mixtures of trisubstituted enamides with excellent enantioselectivity (up to 99% ee). A detailed mechanistic study using deuterium labeling and kinetic experiments revealed two different pathways for the observed enantioconvergence. For α-aryl enamides, fast isomerization of the double bond takes place, and the overall process results in kinetic resolution of the two isomers. For α-alkyl enamides, no double bond isomerization is detected, and competition experiments suggested that substrate chelation is responsible for the enantioconvergent stereochemical outcome. DFT calculations were performed to predict the correct absolute configuration of the products and strengthen the proposed mechanism of the iridium-catalyzed isomerization pathway.
- Yang, Jianping,Massaro, Luca,Krajangsri, Suppachai,Singh, Thishana,Su, Hao,Silvi, Emanuele,Ponra, Sudipta,Eriksson, Lars,Ahlquist, M?rten S. G.,Andersson, Pher G.
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p. 21594 - 21603
(2021/12/27)
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- syn-Selective Michael Reaction of α-Branched Aryl Acetaldehydes with Nitroolefins Promoted by Squaric Amino Acid Derived Bifunctional Br?nsted Bases
-
Here we describe a direct access to 2,2,3-trisubstituted syn γ-nitroaldehydes by addition of α-branched aryl acetaldehydes to nitroolefins promoted by a cinchona based squaric acid-derived amino acid peptide. Different α-methyl arylacetaldehydes react with β-aromatic and β-alkyl nitroolefins to afford the Michael adducts in high enantioselectivity and syn-selectivity. NMR experiments and DFT calculations predict the reaction to occur through the intermediacy of E-enolate. The interaction between the substrates and the catalyst follows Pápai's model, wherein an intramolecular H-bond interaction in the catalyst between the NH group of one of the tert-leucines and the squaramide oxygen seems to be key for discrimination of the corresponding reaction transition states.
- Campano, Teresa E.,García-Urricelqui, Ane,Mielgo, Antonia,Palomo, Claudio,de Cózar, Abel
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p. 3604 - 3612
(2021/07/26)
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- A Bifunctional Copper Catalyst Enables Ester Reduction with H2: Expanding the Reactivity Space of Nucleophilic Copper Hydrides
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Employing a bifunctional catalyst based on a copper(I)/NHC complex and a guanidine organocatalyst, catalytic ester reductions to alcohols with H2 as terminal reducing agent are facilitated. The approach taken here enables the simultaneous activation of esters through hydrogen bonding and formation of nucleophilic copper(I) hydrides from H2, resulting in a catalytic hydride transfer to esters. The reduction step is further facilitated by a proton shuttle mediated by the guanidinium subunit. This bifunctional approach to ester reductions for the first time shifts the reactivity of generally considered "soft"copper(I) hydrides to previously unreactive "hard"ester electrophiles and paves the way for a replacement of stoichiometric reducing agents by a catalyst and H2.
- Kaicharla, Trinadh,Ngoc, Trung Tran,Teichert, Johannes F.,Tzaras, Dimitrios-Ioannis,Zimmermann, Birte M.
-
supporting information
p. 16865 - 16873
(2021/10/20)
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- Palladium-Catalyzed Allenamide Carbopalladation/Allylation with Active Methine Compounds
-
A palladium-catalyzed allenamide carbopalladation/allylation with active methine compounds has been developed. Various indoles and isoquinolinones bearing a quaternary carbon center were achieved with good efficiency, a broad substrate scope and good functional group tolerance. This reaction underwent cascade oxidative addition, carbopalladation, and allylic alkylation, and two new C-C bonds were formed in one pot.
- Zhu, Xiaoyi,Li, Ruibo,Yao, Hequan,Lin, Aijun
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p. 4630 - 4634
(2021/06/28)
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- Binuclear Pd(I)-Pd(I) Catalysis Assisted by Iodide Ligands for Selective Hydroformylation of Alkenes and Alkynes
-
Since its discovery in 1938, hydroformylation has been thoroughly investigated and broadly applied in industry (>107 metric ton yearly). However, the ability to precisely control its regioselectivity with well-established Rh- or Co-catalysts has thus far proven elusive, thereby limiting access to many synthetically valuable aldehydes. Pd-catalysts represent an appealing alternative, yet their use remains sparse due to undesired side-processes. Here, we report a highly selective and exceptionally active catalyst system that is driven by a novel activation strategy and features a unique Pd(I)-Pd(I) mechanism, involving an iodide-assisted binuclear step to release the product. This method enables β-selective hydroformylation of a large range of alkenes and alkynes, including sensitive starting materials. Its utility is demonstrated in the synthesis of antiobesity drug Rimonabant and anti-HIV agent PNU-32945. In a broader context, the new mechanistic understanding enables the development of other carbonylation reactions of high importance to chemical industry.
- Zhang, Yang,Torker, Sebastian,Sigrist, Michel,Bregovi?, Nikola,Dydio, Pawe?
-
supporting information
p. 18251 - 18265
(2020/11/02)
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- Carbonylative Transformation of Allylarenes with CO Surrogates: Tunable Synthesis of 4-Arylbutanoic Acids, 2-Arylbutanoic Acids, and 4-Arylbutanals
-
In this Communication, procedures for the selective synthesis of 4-arylbutanoic acids, 2-arylbutanoic acids, and 4-arylbutanals from the same allylbenzenes have been developed. With formic acid or TFBen as the CO surrogate, reactions proceed selectively and effectively under carbon monoxide gas-free conditions.
- Wu, Fu-Peng,Li, Da,Peng, Jin-Bao,Wu, Xiao-Feng
-
supporting information
p. 5699 - 5703
(2019/08/01)
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- Mild Iridium-Catalysed Isomerization of Epoxides. Computational Insights and Application to the Synthesis of β-Alkyl Amines
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The isomerization of epoxides to aldehydes using the readily available Crabtree's reagent is described. The aldehydes were transformed into synthetically useful amines by a one-pot reductive amination using pyrrolidine as imine-formation catalyst. The reactions worked with low catalyst loadings in very mild conditions. The procedure is operationally simple and tolerates a wide range of functional groups. A DFT study of its mechanism is presented showing that the isomerization takes place via an iridium hydride mechanism with a low energy barrier, in agreement with the mild reaction conditions. (Figure presented.).
- Cabré, Albert,Cabezas-Giménez, Juanjo,Sciortino, Giuseppe,Ujaque, Gregori,Verdaguer, Xavier,Lledós, Agustí,Riera, Antoni
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p. 3624 - 3631
(2019/07/10)
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- Highly Enantioselective Catalytic Kinetic Resolution of α-Branched Aldehydes through Formal Cycloaddition with Homophthalic Anhydrides
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A new catalytic methodology was developed to promote an efficient one-pot kinetic resolution of racemic aldehydes with selectivity (s*) of up to 91 (99:1 d.r., >99 % ee) in a cycloaddition reaction with enolizable anhydrides to afford dihydroisocoumarin products (a core prevalent in natural products and molecules of medicinal interest) containing three contiguous stereocentres.
- Farid, Umar,Aiello, Maria Luisa,Connon, Stephen J.
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p. 10074 - 10079
(2019/07/18)
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- Generation and Application of (Diborylmethyl)zinc(II) Species: Access to Enantioenriched gem-Diborylalkanes by an Asymmetric Allylic Substitution
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We report the successful generation of (diborylmethyl)zinc(II) species by transmetallation beteween isolable (diborylmethyl)lithium and zinc(II) halide (X=Br, Cl) and their application in the synthesis of enantioenriched gem-diborylalkanes bearing a stereogenic center at the β-position of the diboryl groups by an asymmetric allylic substitution reaction. The reaction has a broad substrate scope, and various enantioenriched gem-diborylalkanes can be obtained in good yields with excellent enantioselectivity. Further elaboration of the enantioenriched gem-diborylalkanes provides access to a diverse set of valuable chiral building blocks.
- Lee, Yeosan,Park, Jinyoung,Cho, Seung Hwan
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p. 12930 - 12934
(2018/09/25)
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- Rhodium/Phosphine catalysed selective hydroformylation of biorenewable olefins
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This work reports rhodium catalyzed selective hydroformylation of natural olefins like eugenol, estragole, anethole, prenol and isoprenol using biphenyl based Buchwald phosphine ligands (S-Phos (L1), t-Bu XPhos (L2), Ru-Phos (L3), Johnphos (L4) and DavePhos (L5). Ru-Phos (L3) ligand exhibited high impact on the hydroformylation of eugenol providing high selectivity (90%) of linear aldehyde as major product. In addition, internal natural olefins like anethole and prenol provided moderate to high selectivity (65% and 85% respectively) of branched aldehydes as a major products. The various reaction parameters such as influence of ligands, P/Rh ratio, syngas pressure, temperature, time and solvents have been studied. A high activity and selectivity gained on the way to the linear aldehydes it may be due to the bulky, steric cyclohexyl and isopropoxy groups present in L3 phosphine ligand. Moreover, this catalytic system was smoothly converting natural olefins into corresponding linear and branched aldehydes with higher selectivity under the mild reaction conditions.
- Jagtap, Samadhan A.,Bhanage, Bhalchandra M.
-
-
- Copper-catalyzed vinylogous aerobic oxidation of unsaturated compounds with air
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A mild and operationally simple copper-catalyzed vinylogous aerobic oxidation of β,γ- and α,β-unsaturated esters is described. This method features good yields, broad substrate scope, excellent chemo- and regioselectivity, and good functional group tolerance. This method is additionally capable of oxidizing β,γ- and α,β-unsaturated aldehydes, ketones, amides, nitriles, and sulfones. Furthermore, the present catalytic system is suitable for bisvinylogous and trisvinylogous oxidation. Tetramethylguanidine (TMG) was found to be crucial in its role as a base, but we also speculate that it serves as a ligand to copper(II) triflate to produce the active copper(II) catalyst. Mechanistic experiments conducted suggest a plausible reaction pathway via an allylcopper(II) species. Finally, the breadth of scope and power of this methodology are demonstrated through its application to complex natural product substrates.
- Zhang, Hai-Jun,Schuppe, Alexander W.,Pan, Shi-Tao,Chen, Jin-Xiang,Wang, Bo-Ran,Newhouse, Timothy R.,Yin, Liang
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p. 5300 - 5310
(2018/04/24)
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- Asymmetric α-Allylation of Aldehydes with Alkynes by Integrating Chiral Hydridopalladium and Enamine Catalysis
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A palladium-catalyzed asymmetric α-allylation of aldehydes with alkynes has been established by integrating the catalysis of enamine and chiral hydridopalladium complex that is reversibly formed from the oxidative addition of Pd(0) to chiral phosphoric acid. The ternary catalyst system, consisting of an achiral palladium complex, a primary amine, and a chiral phosphoric acid allows the reaction to tolerate a wide scope of α,α-disubstituted aldehydes and alkynes, affording the corresponding allylation products in high yields and with excellent levels of enantioselectivity.
- Su, Yong-Liang,Li, Lu-Lu,Zhou, Xiao-Le,Dai, Zhen-Yao,Wang, Pu-Sheng,Gong, Liu-Zhu
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p. 2403 - 2406
(2018/04/27)
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- Rhodium-catalyzed asymmetric hydrogenation of β-branched enamides for the synthesis of β-stereogenic amines
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Using a rhodium complex of a bisphosphine ligand (R)-SDP, β-branched simple enamides with a (Z)-configuration were hydrogenated to β-stereogenic amines in quantitative yields and with excellent enantioselectivities (88-96% ee).
- Zhang, Jian,Liu, Chong,Wang, Xingguang,Chen, Jianzhong,Zhang, Zhenfeng,Zhang, Wanbin
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p. 6024 - 6027
(2018/06/18)
-
- Agent for reduction of sensory irritation
-
Provision of a TRPA1 activity inhibitor capable of reducing sensory irritation to skin or mucous membrane and an agent for reduction of sensory irritation for skin or mucous membrane. A TRPA1 inhibitor and an agent for reduction of sensory irritation for skin or mucous membrane comprising as an active ingredient a compound represented by the following formula (1) wherein R1 and R3 each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R2 represents an alkyl group having 1 to 6 carbon atoms, R4 represents a hydrogen atom, a methyl group or an ethyl group, and a double line composed of a dotted line and a solid line represents a single bond or a double bond.
- -
-
Page/Page column 11
(2018/02/03)
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- Design of Potent and Druglike Nonphenolic Inhibitors for Catechol O-Methyltransferase Derived from a Fragment Screening Approach Targeting the S-Adenosyl- l -methionine Pocket
-
A fragment screening approach designed to target specifically the S-adenosyl-l-methionine pocket of catechol O-methyl transferase allowed the identification of structurally related fragments of high ligand efficiency and with activity on the described orthogonal assays. By use of a reliable enzymatic assay together with X-ray crystallography as guidance, a series of fragment modifications revealed an SAR and, after several expansions, potent lead compounds could be obtained. For the first time nonphenolic and small low nanomolar potent, SAM competitive COMT inhibitors are reported. These compounds represent a novel series of potent COMT inhibitors that might be further optimized to new drugs useful for the treatment of Parkinson's disease, as adjuncts in levodopa based therapy, or for the treatment of schizophrenia.
- Lerner, Christian,Jakob-Roetne, Roland,Buettelmann, Bernd,Ehler, Andreas,Rudolph, Markus,Sarmiento, Rosa María Rodríguez
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p. 10163 - 10175
(2016/12/07)
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- Iron-Catalyzed e?Selective dehydrogenative borylation of vinylarenes with pinacolborane
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We report the dehydrogenative borylation of vinylarenes with pinacolborane (HBpin) catalyzed by an iron(0) complex “(PMe3)4Fe”. A variety of monosubstituted and disubstituted vinylarenes underwent this iron-catalyzed transformation, affording E-vinyl boronate esters (VBEs) selectively in hi h ields. In addition we coupled this iron-catal zed dehydrogenative borylation with further transformations of the resulting vinyl boronate esters and developed various one-pot procedures for the functionalization of the vinylic C?H bonds in vinylarenes. Mechanistic studies reveal that this Fe-catalyzed reaction proceeds through syn-insertion of vinylarenes into a Fe-boryl species followed by β-hydrogen elimination from a syn coplanar conformation of the borylalkyl iron intermediate.
- Wang, Chao,Wu, Caizhi,Ge, Shaozhong
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p. 7585 - 7589
(2018/05/23)
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- Dual Catalysis Using Boronic Acid and Chiral Amine: Acyclic Quaternary Carbons via Enantioselective Alkylation of Branched Aldehydes with Allylic Alcohols
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A ferrocenium boronic acid salt activates allylic alcohols to generate transient carbocations that react with in situ-generated chiral enamines from branched aldehydes. The optimized conditions afford the desired acyclic products embedding a methyl-aryl quaternary carbon center with up to 90% yield and 97:3 enantiomeric ratio, with only water as the byproduct. This noble-metal-free method complements alternative methods that are incompatible with carbon-halogen bonds and other sensitive functional groups.
- Mo, Xiaobin,Hall, Dennis G.
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p. 10762 - 10765
(2016/09/09)
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- Enantioselective Rhodium-Catalyzed Allylic Alkylation of Prochiral α,α-Disubstituted Aldehyde Enolates for the Construction of Acyclic Quaternary Stereogenic Centers
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A highly enantioselective rhodium-catalyzed allylic alkylation of prochiral α,α-disubstituted aldehyde enolates with allyl benzoate is described. This protocol provides a novel approach for the synthesis of acyclic quaternary carbon stereogenic centers and it represents the first example of the direct enantioselective alkylation of an aldehyde enolate per se. The versatility of the α-quaternary aldehyde products is demonstrated through their conversion to a variety of useful motifs applicable to target-directed synthesis. Finally, mechanistic studies indicate that high levels of asymmetric induction are achieved from a mixture of prochiral (E)- and (Z)-enolates, which provides an exciting development for this type of transformation.
- Wright, Timothy B.,Evans, P. Andrew
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p. 15303 - 15306
(2016/12/09)
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- Direct Synthesis of α-Allenols from TMS-Protected Alkynes and Aldehydes Mediated by Tetrabutylammonium Fluoride
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A unique chemoselective synthesis of α-allenic alcohols is presented. Tetrabutylammonium fluoride (TBAF) mediated this transformation under mild reaction conditions. A range of functional groups is well-tolerated in this reaction, while affording adducts
- Huang, Xiaojun,Bugarin, Alejandro
-
supporting information
p. 12696 - 12700
(2016/08/30)
-
- Dynamic kinetic asymmetric amination of alcohols: From a mixture of four isomers to diastereo- and enantiopure α-branched amines
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The first dynamic kinetic asymmetric amination of alcohols via borrowing hydrogen methodology is presented. Under the cooperative catalysis by an iridium complex and a chiral phosphoric acid, α-branched alcohols that exist as a mixture of four isomers undergo racemization by two orthogonal mechanisms and are converted to diastereo- and enantiopure amines bearing adjacent stereocenters. The preparation of diastereo- and enantiopure 1,2-amino alcohols is also realized using this catalytic system.
- Rong, Zi-Qiang,Zhang, Yao,Chua, Raymond Hong Bing,Pan, Hui-Jie,Zhao, Yu
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p. 4944 - 4947
(2015/05/05)
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- A simple primary amine catalyst for enantioselective α-hydroxylations and α-fluorinations of branched aldehydes
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A new primary amine catalyst for the asymmetric α-hydroxylation and α-fluorination of α-branched aldehydes is described. The products of the title transformations are generated in excellent yields with high enantioselectivities. Both processes can be performed within short reaction times and on gram scale. The similarity in results obtained in both reactions, combined with computational evidence, implies a common basis for stereoinduction and the possibility of a general catalytic mechanism for α-functionalizations. Promising initial results in α-amination and α-chlorination reactions support this hypothesis.
- Witten, Michael R.,Jacobsen, Eric N.
-
supporting information
p. 2772 - 2775
(2015/06/16)
-
- An air-stable cationic iridium hydride as a highly active and general catalyst for the isomerization of terminal epoxides
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We describe the use of an air-stable iridium hydride catalyst for the isomerization of terminal epoxides into aldehydes with perfect regioselectivity. The system operates at low loadings of catalyst (0.5 mol%), is highly practical, scalable, and tolerates functional groups that would not be compatible with Lewis acids typically used in stoichiometric amounts. Evidence for a rare hydride mechanism are provided. This journal is the Partner Organisations 2014.
- Humbert, Nicolas,Vyas, Devendra J.,Besnard, Céline,Mazet, Clément
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supporting information
p. 10592 - 10595
(2014/10/15)
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- Isomerization of terminal epoxides by a [Pd-H] catalyst: A combined experimental and theoretical mechanistic study
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An unusual palladium hydride complex has been shown to be a competent catalyst in the isomerization of a variety of terminal and internal epoxides. The reaction displayed broad scope and synthetic utility. Experimental and theoretical evidence are provided for an unprecedented hydride mechanism characterized by two distinct enantio-determining steps. These results hold promise for the development of an enantioselective variant of the reaction.
- Vyas, Devendra J.,Larionov, Evgeny,Besnard, Celine,Guenee, Laure,Mazet, Clement
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p. 6177 - 6183
(2013/06/04)
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- Complementary catalytic strategies to access α-chiral aldehydes
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The present article summarizes the development of two novel and complementary catalytic methods to access α-chiral aldehydes. A C1-symmetric chiral (P,N) ligand with a structure derived from the ubiquitous binepine scaffold has been specifically designed for the Pd-catalyzed α arylation of aldehydes to access indane derivatives with a well-defined quaternary stereocenter in high yields and excellent enantioselectivities. In addition, a dinuclear palladium hydride catalyst has been synthesized for the isomerization of terminal and trisubstituted epoxides into aldehydes and ketones respectively. Combined experimental and theoretical investigations pointed to an unprecedented 'epoxide-opening/hydride-transfer' sequence. The mechanism also features two distinct enantio-determining steps in the kinetic resolution of racemic epoxides. Schweizerische Chemische Gesellschaft.
- Mazet, Clement
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p. 658 - 662
(2013/11/06)
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- β-tert-Butyl aspartate as an organocatalyst for the asymmetric α-amination of α,α-disubstituted aldehydes
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The enantioselective α-amination reaction of α,α- disubstituted aldehydes can lead to a variety of enantioenriched amino aldehydes, amino alcohols, and amino acids. After screening a variety of amino acids and their derivatives, we identified a cheap, simple, commercially available aspartic acid derivative that can catalyze efficiently the reaction between α,α-disubstituted aldehydes and dialkyl azodicarboxylates. The reaction proceeds smoothly leading to the corresponding α-aminated adducts in moderate to quantitative yields and moderate to high enantioselectivities (up to 96% ee). Finally, the conversion of these adducts to α,α-disubstituted quaternary amino acids is also described.
- Theodorou, Alexis,Papadopoulos, Giorgos N.,Kokotos, Christoforos G.
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supporting information
p. 5438 - 5443
(2013/07/05)
-
- AGENT FOR REDUCTION OF SENSORY IRRITATION
-
Provision of a TRPA1 activity inhibitor capable of reducing sensory irritation to skin or mucous membrane and an agent for reduction of sensory irritation for skin or mucous membrane. A TRPA1 inhibitor and an agent for reduction of sensory irritation for skin or mucous membrane comprising as an active ingredient a compound represented by the following formula (1) wherein R1 and R3 each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R2 represents an alkyl group having 1 to 6 carbon atoms, R4 represents a hydrogen atom, a methyl group or an ethyl group, and a double line composed of a dotted line and a solid line represents a single bond or a double bond.
- -
-
Paragraph 0044; 0045
(2013/07/19)
-
- Oxidative cleavage of α-aryl aldehydes using iodosylbenzene
-
We found that α-aryl aldehydes can be cleaved to chain-shortened carbonyl compounds and formaldehyde by various iodosylbenzene complexes. A mechanistic scheme is presented that accounts for the loss of one carbon atom. Formaldehyde is further oxidized to CO and CO2 under the reaction conditions.
- Havare, Nizam,Plattner, Dietmar A.
-
supporting information
p. 5078 - 5081,4
(2020/09/15)
-
- Enantioselective organocatalytic formal allylation of α-branched aldehydes
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Heteroarylvinyl sulfone 1 has been successfully used as a new sulfonyl Michael acceptor in aminocatalytic reactions with branched aldehydes. Subsequent one-pot Julia-Kocienski olefination allows the challenging preparation of enantiomerically pure α-allylated aldehydes bearing C-α quaternary carbons.
- Rodrigo, Eduardo,Morales, Sara,Duce, Sara,Ruano, Jose Luis Garcia,Cid, M. Belen
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p. 11267 - 11269
(2011/12/05)
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- Hydroformylation of alkenes using heterogeneous catalyst prepared by intercalation of HRh(CO)(TPPTS)3 complex in hydrotalcite
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Intercalation of HRh(CO)(TPPTS)3 complex into the interlayer space of hydrotalcite was carried out to prepare an eco-friendly heterogeneous hydroformylation catalyst. Intercalated catalyst was characterized by 31P NMR, P-XRD, FT-IR, SEM and surface area measurements. Catalytic activity of intercalated catalyst [HT(3.5)-INT] was evaluated for hydroformylation of linear alkenes of varied carbon number from C5 to C13 as well as cyclic alkenes. Selectivity of the aldehydes was observed to decrease with increase in the carbon chain length of linear alkenes. Effect of reaction parameters on catalytic activity of intercalated catalyst was studied by varying the catalyst amount, 1-hexene concentration, reaction temperature, partial pressure of carbon monoxide and hydrogen for hydroformylation of 1-hexene. The catalyst was re-cycled up to five times without significant loss in the alkene conversion and selectivity of aldehydes.
- Sharma, Sumeet K.,Parikh, Parimal A.,Jasra, Raksh V.
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experimental part
p. 153 - 162
(2010/05/01)
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- Preparation of multisubstituted enamides via rhodium-catalyzed carbozincation and hydrozincation of ynamides
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(Chemical Equation Presented) Rhodium-catalyzed carbozincation of ynamides using diorganozinc reagents or functionalized organozinc halides is described.Using a tri(2-furyl)phosphine-modified rhodium catalyst, the reaction course is altered to hydrozincation when diethylzinc is employed as the organozinc reagent. Trapping of the alkenylzinc intermediates produced in these reactions in further functionalization reactions is possible. Collectively, these processes enable access to a range of multisubstituted enamides in stereo- and regiocontrolled fashion.
- Gourdet, Benoit,Rudkin, Mairi E.,Watts, Ciorsdaidh A.,Hon, Wai Lam
-
supporting information; experimental part
p. 7849 - 7858
(2010/01/16)
-
- Enantioselective synthesis of β-trifluoromethyl-βlactones via NHC-catalyzed ketene - ketone cycloaddition reactions
-
The highly diastereo- and enantioselective synthesis of β-trifluoromethyl-β-lactones bearing two contiguous stereocenters was realized by chiral N-heterocyclic carbene-catalyzed formal cycloaddition reaction of alkyl(aryl)ketenes and trifluoromethyl ketones.
- Wang, Xiao-Na,Shao, Pan-Lin,Lv, Hui,Ye, Song
-
supporting information; experimental part
p. 4029 - 4031
(2009/12/06)
-
- Arylation of allyl alcohols in organic and aqueous media catalyzed by oxime-derived palladacycles: Synthesis of β-arylated carbonyl compounds
-
A 4-hydroxyacetophenone oxime-derived palladacycle catalyzes the Mizoroki-Heck reaction of allyl alcohols with aryl iodides, bromides, and chlorides in aqueous and organic solvents. The reaction takes place in the presence of dicyclohexylmethylamine or cesium carbonate as bases, the addition of tetrabutylammonium bromide (TBAB) as additive for aryl bromides and chlorides being necessary. Under these reaction conditions, β-arylated aldehydes and ketones are mainly obtained using a rather low loading of palladium (0.1-1 mol%). Similar catalytic activity is shown by a Kaiser oxime resin-derived palladacycle, which allows one to perform recycling and reusing experiments with low Pd leaching. The high regio- and chemoselectivity observed supported that these palladacycles, working as a source of Pd(0) species, operates mainly through a neutral mechanism. This methodology has been applied to the synthesis of important β-arylated carbonyl compounds, such as 4-phenylbutan-2-one, 4-(4-hydroxyphenyl)butan-2-one, dihydrochalcones, the anti-inflamatory nabumetone, and the fragance β-lilial. γ-Arylation is observed in the reactions of allyl alcohol and but-3-en-2-ol with 2-iodoaniline giving mainly the corresponding quinolines. The same tendency is observed in the case of 1,1-dimethylallyl alcohol affording either γ-arylated alcohols or (E)-1-arylisoprenes.
- Alacid, Emilio,Najera, Carmen
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p. 2572 - 2584
(2008/09/19)
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- Rhodium-catalyzed hydroformylation of olefins: Effect of [bis(2,4-di-tert-butyl) pentaerythritol] diphosphite (alkanox P-24) on the regioselectivity of the reaction
-
Rhodium (I) associated with [bis(2,4-di-tert-butyl) pentaerythritol] diphosphite (I) as a ligand represents an active catalyst system for highly regioselective hydroformylation of various alkenes. The commercially available bis(2,4-di-tert-butyl)pentaerythritol diphosphite (alkanox P-24) (I), which has been used so far as an antioxidant in the stabilization of polymers, was used as a diphosphite ligand for the selective hydroformylation reaction of olefins. Excellent selectivity towards linear aldehydes and excellent conversions were achieved in the hydroformylation of alkenes. The hydroformylation reaction was applied to various olefinic substrates including the internal alkenes.
- Tijani, Jimoh,El Ali, Bassam
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p. 3492 - 3497
(2008/02/12)
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- Palladium-catalyzed Heck arylations of allyl alcohols in ionic liquids: Remarkable base effect on the selectivity
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Pd-catalyzed Heck arylation of allyl alcohols in tetraalkylammonium ionic liquids (ILs) can be made highly selective toward the formation of either aromatic carbonyl compounds or aromatic conjugated alcohols by carefully choosing both the IL and the base.
- Calo, Vincenzo,Nacci, Angelo,Monopoli, Antonio,Ferola, Valentina
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p. 2596 - 2601
(2007/10/03)
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- Ru-catalyzed asymmetric hydrogenation of racemic aldehydes via dynamic kinetic resolution: Efficient synthesis of optically active primary alcohols
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A highly efficient asymmetric hydrogenation of racemic α-arylaldehydes via dynamic kinetic resolution has been developed by using [RuCl2(SDPs)(diamine)] complexes as catalysts, providing chiral primary alcohols in excellent enantioselectivities. Copyright
- Xie, Jian-Hua,Zhou, Zhang-Tao,Kong, Wei-Ling,Zhou, Qi-Lin
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p. 1868 - 1869
(2007/10/03)
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- The proline-catalyzed asymmetric amination of branched aldehydes
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An efficient access to configurationally stable α,β- disubstituted α-amino aldehydes, oxazolidinones, and α-amino acids has been presented. Starting from simple and easily available racemic aldehydes, the α-aminated products were obtained using azodicarboxylates as the nitrogen source in up to 86 % ee and moderate to excellent yield. These products could further be converted both into the corresponding α-amino alcohols and, depending on the residue of the azodicarboxylates and the reaction conditions, into the oxazolidinones. On the other hand, oxidation towards the carboxylic acid and cleavage of the hydrazide bond under mild conditions revealed the free α-alkylated phenylglycine derivative. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Baumann, Thomas,Vogt, Henning,Braese, Stefan
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p. 266 - 282
(2007/10/03)
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- Substrate specificity and reaction mechanism of recombinant styrene oxide isomerase from Pseudomonas putida S12
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To clarify the substrate specificity of the recombinant styrene oxide isomerase, various epoxides were subjected to the reaction. From the substituent effect on the rate of isomerization, the mechanism of the isomerase catalyzed reaction was estimated.
- Miyamoto, Kenji,Okuro, Kou,Ohta, Hiromichi
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p. 3255 - 3257
(2008/02/02)
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- An approach to enantioselective 5-endo halo-lactonization reactions
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Enantioselective lactonization of 4-substituted but-3-enoic acids using iodobis(N-methylephedrine) hexafluoroantimonate in dichloromethane at low temperatures is reported. The presence of bis(N-methylephedrine)silver(I) hexafluoroantimonate, derived from
- Garnier, Jean Marc,Robin, Sylvie,Rousseau, Gerard
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p. 3281 - 3291
(2008/02/10)
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- Asymmetric synthesis of novel α-amino acids with β-branched side chains
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An asymmetric synthesis of α-amino acids with novel β-branched side chains has been implemented. The syntheses feature a p-toluenesulfinylimine induced chiral Strecker approach and were found to be applicable to the introduction of both aliphatic and aromatic β-branched sidechains for preparation of previously unknown α-amino acids.
- Zhang, Minsheng,Porte, Alex,Diamantidis, George,Sogi, Kimberly,Kubrak, Dennis,Resnick, Lynn,Mayer, Scott C.,Wang, Zheng,Kreft, Anthony F.,Harrison, Boyd L.
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p. 2401 - 2403
(2008/02/03)
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- Intrazeolite photooxygenation of chiral alkenes. Control of facial selectivity by confinement and cation-π interactions
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Depending on the nature of the substituents on the stereogenic carbon atom, the ene reaction of singlet oxygen with several chiral alkenes by confinement within thionin-supported zeolite NaY, may exhibit significant changes on facial selectivity by comparison to their photooxygenation reaction in solution. It is proposed that, apart from the conformational consequences as a result of the alkene confinement within the zeolite cavities, a synergism between Na+-π interactions and singlet oxygen-Na+ interactions plays a significant role in the transition states of ene hydroperoxidation. Within NaY, the diastereoselectivity may significantly depend on the site selectivity, as probed through specific deuterium labelling of trisubstituted alkenes bearing a gem-dimethyl group. In certain cases, a remote stereogenic centre relative to the reacting double bond may induce enhanced diastereoselection and regioselectivity.
- Stratakis, Manolis,Raptis, Christos,Sofikiti, Nikoletta,Tsangarakis, Constantinos,Kosmas, Giannis,Zaravinos, Ioannis-Panagiotis,Kalaitzakis, Dimitris,Stavroulakis, Dimitris,Baskakis, Constantinos,Stathoulopoulou, Aggeliki
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p. 10623 - 10632
(2007/10/03)
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- Catalytic asymmetric reductive amination of aldehydes via dynamic kinetic resolution
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A novel organocatalytic asymmetric reductive amination of aldehydes has been developed. Treating racemic α-branched aldehydes with p-anisidine and a Hantzsch ester in the presence of our previously developed phosphoric acid catalyst, TRIP, gave β-branched secondary amines in excellent yields and enantioselectivities via an efficient dynamic kinetic resolution. The process is applicable to several different aromatic aldehydes and amines but gives slightly reduced enantiomeric ratios with aliphatic aldehydes. Copyright
- Hoffmann, Sebastian,Nicoletti, Marcello,List, Benjamin
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p. 13074 - 13075
(2008/02/08)
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- Remarkable Change of the Diastereoselection in the Dye-Sensitized Ene Hydroperoxidation of Chiral Alkenes by Zeolite Confinement
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(Equation presented) The ene reaction of singlet oxygen with chiral trisubstituted alkenes bearing an alkyl and a phenyl group at the stereogenic center is erythro diastereoselective in solution and threo diastereoselective if carried out within zeolite Na-Y. The change of the diastereoselection trend by zeolite confinement is attributed to a synergism of steric effects and cation-π interactions.
- Stratakis, Manolis,Kalaitzakis, Dimitris,Stavroulakis, Dimitris,Kosmas, Giannis,Tsangarakis, Constantinos
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p. 3471 - 3474
(2007/10/03)
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- Arylation of allylic alcohols in ionic liquids catalysed by a Pd-benzothiazole carbene complex
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The reaction of aryl bromides with allylic alcohols catalysed by a Pd-benzothiazole carbene complex, in tetrabutylammonium bromide as solvent, leads principally to β-arylated carbonyl compounds. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Calo, Vincenzo,Nacci, Angelo,Monopoli, Antonio,Spinelli, Michele
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p. 1382 - 1385
(2007/10/03)
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- Proline-catalysed asymmetric amination of α,α-disubstituted aldehydes: Synthesis of configurationally stable enantioenriched α-aminoaldehydes
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Proline-catalysed animation of α,α-disubstituted racemic aldehydes with azodicarboxylates proceeds smoothly to give configurationally stable scalemic aldehydes and oxazolidinones in up to 86% ee.
- Vogt, Henning,Vanderheiden, Sylvia,Braese, Stefan
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p. 2448 - 2449
(2007/10/03)
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- Heck arylation of allylic alcohols in molten salts
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The Heck coupling of ArX (X=I, Br) with allylic alcohols, carried out at 80-120°C in molten n-Bu4NBr using NaHCO3 as base and PdCl2 as catalyst without extra ligands, leads to the corresponding β-arylated carbonyl compounds. After extraction of the organic materials with diethyl ether, the ionic layer can be reused directly.
- Bouquillon, Sandrine,Ganchegui, Benjamin,Estrine, Boris,Hénin, Fran?oise,Muzart, Jacques
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p. 153 - 156
(2007/10/03)
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- 4-HYDROXY-BENZOPYRAN-2-ONES AND 4-HYDROXY-CYCLOALKYL[B]PYRAN-2-ONES USEFUL TO TREAT RETROVIRAL INFECTIONS
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The present invention relates to compounds of formula I which are 4-hydroxy-benzopyran-2-ones and 4-hydroxy-cycloalkyl[b]pyran-2-ones useful for inhibiting a retrovirus in a mammalian cell infected with said retrovirus. STR1 Wherein R 10 and R 20 taken together are: STR2
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- Studies on the synthesis of chiral 2-(p.chlorophenyl)-3-methylbutanoic acid, a key-precursor of Fenvalerate, by hydrocarbonylation reactions
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The preparation of racemic 2-(p.chlorophenyl)-3-methylbutanoic acid (2), a building block for (S,S)-Fenvalerate (an important broad spectrum insecticide), was effected by rhodium catalyzed hydroformylation of 2-methyl-1 -(p.chlorophenyl) propene (4) in the presence of excess of triphenylphosphine to inhibit substrate isomerization followed by mild oxidation of the resulting aldehyde 6; an overall yield of 88% was reached. Olefin 4 exhibits a very low tendency to undergo both hydrocarboethoxylation and hydrocarboxylation in the presence of palladium complexes as catalysts. Enantioselective hydrocarbonylation reactions carried out on olefin 4 afford unsatisfactory chemical and optical yields of the optically active ester 5 or acid 2. Springer-Verlag 1996.
- Botteghi, Carlo,Bona, Denis Dalla,Paganelli, Stefano,Marchetti, Mauro,Sechi, Barbara
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p. 101 - 107
(2007/10/03)
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- A further breakthrough in biphasic, rhodium-catalyzed hydroformylation: The use of per(2,6-di-O-methyl)-β-cyclodextrin as inverse phase transfer catalyst
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Solvent free biphasic hydroformylation of various water-insoluble terminal olefins can be achieved in high yields and selectivities by using a water-soluble rhodium/triphenylphosphine trisulfonate catalyst and per(2,6-di-o-methyl)-β-cyclodextrin as inverse phase transfer catalyst. The catalytic activities were up to ten times higher than those observed without per(2,6-di-o-methyl)-β-cyclodextrin.
- Monflier, Eric,Tilloy, Sebastien,Fremy, Georges,Castanet, Yves,Mortreux, Andre
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p. 9481 - 9484
(2007/10/02)
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- Al-NiCl(2°)6H2O-THF: A new, mild and neutral system for selective reduction of organic functional groups
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A mild and neutral reducing system consisting of Al-NiCl(2°)6H2O-THF has been developed and reacted with a series of organic compounds containing different functional groups in order to evaluate its synthetic utility. It was observed that this system very efficiently reduces the α-enones to the saturated ketones, aromatic aldehydes and ketones to the corresponding alcohols, nitriles and nitroarenes to amines, acid anhydrides and acid chlorides to aldehydes, disulphides to thiols and epoxides to the corresponding alcohols. On the other hand isolated double bonds, carboxylic acids, esters, lactones, primary, benzyl and allyl halides, aliphatic aldehydes and ketones and aliphatic nitro compounds were found to remain inert to this system. Furthermore, the reducing properties of Al-NiCl(2°)6H2O in several other organic solvents were also studied.
- Sarmah,Barua
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p. 8587 - 8600
(2007/10/02)
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- Synthesis of chiral adenosine receptor recognition units via a sharpless asymmetric epoxidation procedure
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Opening of the epoxide of (E)-4-phenyl-2-buten-1-ol with trimethylaluminum gave two phenonium ion-mediated products, whose ratio was dependent on reaction conditions.
- Lentz,Peet
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p. 811 - 814
(2007/10/02)
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