- Development of effective bidentate diphosphine ligands of ruthenium catalysts toward practical hydrogenation of carboxylic acids
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Hydrogenation of carboxylic acids (CAs) to alcohols represents one of the most ideal reduction methods for utilizing abundant CAs as alternative carbon and energy sources. However, systematic studies on the effects of metal-to-ligand relationships on the catalytic activity of metal complex catalysts are scarce. We previously demonstrated a rational methodology for CA hydrogenation, in which CA-derived cationic metal carboxylate [(PP)M(OCOR)]+ (M = Ru and Re; P = one P coordination) served as the catalyst prototype for CA self-induced CA hydrogenation. Herein, we report systematic trial- and-error studies on how we could achieve higher catalytic activity by modifying the structure of bidentate diphosphine (PP) ligands of molecular Ru catalysts. Carbon chains connecting two P atoms as well as Ar groups substituted on the P atoms of PP ligands were intensively varied, and the induction of active Ru catalysts from precatalyst Ru(acac)3 was surveyed extensively. As a result, the activity and durability of the (PP)Ru catalyst substantially increased compared to those of other molecular Ru catalyst systems, including our original Ru catalysts. The results validate our approach for improving the catalyst performance, which would benefit further advancement of CA self-induced CA hydrogenation.
- Saito, Susumu,Wen, Ke,Yoshioka, Shota
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p. 1510 - 1524
(2021/06/18)
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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.
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supporting information
p. 16865 - 16873
(2021/10/20)
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- Radical hydroxymethylation of alkyl iodides using formaldehyde as a C1 synthon
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Radical hydroxymethylation using formaldehyde as a C1 synthon is challenging due to the reversible and endothermic nature of the addition process. Here we report a strategy that couples alkyl iodide building blocks with formaldehyde through the use of photocatalysis and a phosphine additive. Halogen-atom transfer (XAT) from α-aminoalkyl radicals is leveraged to convert the iodide into the corresponding open-shell species, while its following addition to formaldehyde is rendered irreversible by trapping the transient O-radical with PPh3. This event delivers a phosphoranyl radical that re-generates the alkyl radical and provides the hydroxymethylated product.
- Caiger, Lewis,Constantin, Timothée,Douglas, James J.,Juliá, Fabio,Leonori, Daniele,Sheikh, Nadeem S.,Sinton, Conar
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p. 10448 - 10454
(2021/08/20)
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- Redox-active ligand based Mn(i)-catalyst for hydrosilylative ester reduction
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Herein a Mn(i) catalyst bearing a redox-active phenalenyl (PLY) based ligand is reported for the efficient hydrosilylation of esters to alcohols using the inexpensive silane source polymethylhydrosiloxane (PMHS) under mild conditions. Mechanistic investigations suggest a strong ligand-metal cooperation where a ligand-based single electron transfer (SET) process initiates the reaction through Si-H bond activation.
- Chakraborty, Soumi,Das, Arpan,Mandal, Swadhin K.
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supporting information
p. 12671 - 12674
(2021/12/04)
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- Nitrile Synthesis by Aerobic Oxidation of Primary Amines and in situ Generated Imines from Aldehydes and Ammonium Salt with Grubbs Catalyst
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Herein, a Grubbs-catalyzed route for the synthesis of nitriles via the aerobic oxidation of primary amines is reported. This reaction accommodates a variety of substrates, including simple primary amines, sterically hindered β,β-disubstituted amines, allylamine, benzylamines, and α-amino esters. Reaction compatibility with various functionalities is also noted, particularly with alkenes, alkynes, halogens, esters, silyl ethers, and free hydroxyl groups. The nitriles were also synthesized via the oxidation of imines generated from aldehydes and NH4OAc in situ. (Figure presented.).
- Utsumi, Tatsuki,Noda, Kenta,Kawauchi, Daichi,Ueda, Hirofumi,Tokuyama, Hidetoshi
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supporting information
p. 3583 - 3588
(2020/08/05)
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- Design, Synthesis, and in vitro Evaluation of P2X7 Antagonists
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The P2X7 receptor is a promising target for the treatment of various diseases due to its significant role in inflammation and immune cell signaling. This work describes the design, synthesis, and in vitro evaluation of a series of novel derivatives bearing diverse scaffolds as potent P2X7 antagonists. Our approach was based on structural modifications of reported (adamantan-1-yl)methylbenzamides able to inhibit the receptor activation. The adamantane moieties and the amide bond were replaced, and the replacements were evaluated by a ligand-based pharmacophore model. The antagonistic potency of the synthesized analogues was assessed by two-electrode voltage clamp experiments, using Xenopus laevis oocytes that express the human P2X7 receptor. SAR studies suggested that the replacement of the adamantane ring by an aryl-cyclohexyl moiety afforded the most potent antagonists against the activation of the P2X7 cation channel, with analogue 2-chloro-N-[1-(3-(nitrooxymethyl)phenyl)cyclohexyl)methyl]benzamide (56) exhibiting the best potency with an IC50 value of 0.39 μΜ.
- Durner, Anna,Koufaki, Maria,Kritsi, Eftichia,Nicke, Annette,Papakostas, Alexios,T. Pournara, Dimitra,Zoumpoulakis, Panagiotis
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p. 2530 - 2543
(2020/10/19)
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- A General Method for Photocatalytic Decarboxylative Hydroxylation of Carboxylic Acids
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A general and practical method for decarboxylative hydroxylation of carboxylic acids was developed through visible light-induced photocatalysis using molecular oxygen as the green oxidant. The addition of NaBH4 to in situ reduce the unstable peroxyl radical intermediate much broadened the substrate scope. Different sp3 carbon-bearing carboxylic acids were successfully employed as substrates, including phenylacetic acid-type substrates, as well as aliphatic carboxylic acids. This transformation worked smoothly on primary, secondary, and tertiary carboxylic acids.
- Khan, Shah Nawaz,Zaman, Muhammad Kashif,Li, Ruining,Sun, Zhankui
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p. 5019 - 5026
(2020/05/01)
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- Continuous-Flow Amide and Ester Reductions Using Neat Borane Dimethylsulfide Complex
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Reductions of amides and esters are of critical importance in synthetic chemistry, and there are numerous protocols for executing these transformations employing traditional batch conditions. Notably, strategies based on flow chemistry, especially for amide reductions, are much less explored. Herein, a simple process was developed in which neat borane dimethylsulfide complex (BH3?DMS) was used to reduce various esters and amides under continuous-flow conditions. Taking advantage of the solvent-free nature of the commercially available borane reagent, high substrate concentrations were realized, allowing outstanding productivity and a significant reduction in E-factors. In addition, with carefully optimized short residence times, the corresponding alcohols and amines were obtained in high selectivity and high yields. The synthetic utility of the inexpensive and easily implemented flow protocol was further corroborated by multigram-scale syntheses of pharmaceutically relevant products. Owing to its beneficial features, including low solvent and reducing agent consumption, high selectivity, simplicity, and inherent scalability, the present process demonstrates fewer environmental concerns than most typical batch reductions using metal hydrides as reducing agents.
- ?tv?s, Sándor B.,Kappe, C. Oliver
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p. 1800 - 1807
(2020/02/27)
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- Catalytic Enantioselective α-Ketol Rearrangement
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A highly enantioselective α-ketol rearrangement has been developed. In the presence of a chiral Cu-bisoxazoline complex, achiral β-hydroxy-α-dicarbonyls were isomerized to chiral α-hydroxy-β-dicarbonyls and their bicyclic derivatives in excellent yields and enantioselectivities. Enantioenriched 2-acyl-2-hydroxy cyclohexan-1-ones, dihydroxyhexahydrobenzofuranones, and dihydroxyhexahydro-cycloheptafuranones, with up to three stereocenters, were readily prepared from achiral starting materials in one operation. The reaction is applicable to the desymmetrization of meso substrates and kinetic resolution of racemic alcohols.
- Wu, Hua,Andres, Rémi,Wang, Qian,Zhu, Jieping
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supporting information
p. 499 - 503
(2018/12/13)
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- Preparation of isoquinazolines: Via metal-free [4 + 2] cycloaddition of ynamides with nitriles
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TfOH-mediated [4 + 2] cycloaddition of ynamides with nitriles to construct 1,2-dihydroquinazolines is realized by a direct reaction in moderate to excellent yields (up to 93%) in a stereospecific manner. A rapid and efficient strategy has been employed for the syntheses of alkyl-substituted 1,2-dihydroquinazoline derivatives, and it exhibits good functional group tolerance, has a short reaction time, shows excellent diastereoselectivity, and is a simple and high-yielding reaction.
- Wu, Hao,Liu, Yu,He, Ming-Xing,Wen, Hao,Cao, Wei,Chen, Ping,Tang, Yu
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p. 8408 - 8416
(2019/09/30)
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- Controlled Reduction of Carboxamides to Alcohols or Amines by Zinc Hydrides
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New protocols for controlled reduction of carboxamides to either alcohols or amines were established using a combination of sodium hydride (NaH) and zinc halides (ZnX2). Use of a different halide on ZnX2 dictates the selectivity, wherein the NaH-ZnI2 system delivers alcohols and NaH-ZnCl2 gives amines. Extensive mechanistic studies by experimental and theoretical approaches imply that polymeric zinc hydride (ZnH2)∞ is responsible for alcohol formation, whereas dimeric zinc chloride hydride (H?Zn?Cl)2 is the key species for the production of amines.
- Ong, Derek Yiren,Yen, Zhihao,Yoshii, Asami,Revillo Imbernon, Julia,Takita, Ryo,Chiba, Shunsuke
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supporting information
p. 4992 - 4997
(2019/03/13)
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- The reductive deaminative conversion of nitriles to alcohols using: Para -formaldehyde in aqueous solution
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We report herein, for the first time, the application of para-formaldehyde (pFA) to the reductive deamination of both aliphatic and aromatic nitriles in aqueous solution under transfer hydrogenation conditions. A broad range of primary alcohols have been synthesized selectively with very good to excellent yields under the optimized conditions. The study disclosed that the air-stable, inexpensive and commercially available catalyst [Ru(p-cymene)Cl2]2 acts as the catalyst precursor in this reaction, converting to other more active catalytic species in the presence of pFA, resulting in its degradation to CO2 and H2. Nitriles are also showed to play a dual role in this transformation, both as a substrate and as a ligand, where the dimeric catalyst structures convert to monomeric ones upon the coordination of nitrile molecules.
- Tavakoli, Ghazal,Prechtl, Martin H. G.
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p. 6092 - 6101
(2019/11/11)
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- General and Phosphine-Free Cobalt-Catalyzed Hydrogenation of Esters to Alcohols
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Catalytic hydrogenation of esters is essential for the sustainable production of alcohols in organic synthesis and chemical industry. Herein, we describe the first non-noble metal catalytic system that enables an efficient hydrogenation of non-activated esters to alcohols in the absence of phosphine ligands (with a maximum turnover number of 2391). The general applicability of this protocol was demonstrated by the high-yielding hydrogenation of 39 ester substrates including aromatic/aliphatic esters, lactones, polyesters and various pharmaceutical molecules.
- Shao, Zhihui,Zhong, Rui,Ferraccioli, Raffaella,Li, Yibiao,Liu, Qiang
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supporting information
p. 1125 - 1130
(2019/10/22)
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- Cu-Catalyzed Hydroxymethylation of Unactivated Alkyl Iodides with CO To Provide One-Carbon-Extended Alcohols
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We have developed a reductive carbonylation method by which unactivated alkyl iodides can be hydroxymethylated to provide one-carbon-extended alcohol products under Cu-catalyzed conditions. The method is tolerant of alkyl β-hydrogen atoms, is robust towards a wide variety of functional groups, and was applied to primary, secondary, and tertiary alkyl iodide substrates. Mechanistic experiments indicate that the transformation proceeds by atom-transfer carbonylation (ATC) of the alkyl iodide followed in tandem by two CuH-mediated reductions in rapid succession. This radical mechanism renders the Cu-catalyzed system complementary to precious-metal-catalyzed reductive carbonylation reactions.
- Zhao, Siling,Mankad, Neal P.
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supporting information
p. 5867 - 5870
(2018/04/17)
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- Multiple Halogenation of Aliphatic C?H Bonds within the Hofmann–L?ffler Manifold
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An innovative approach to position-selective polyhalogenation of aliphatic hydrocarbon bonds is presented. The reaction proceeded within the Hofmann-L?ffler manifold with amidyl radicals as the sole mediators to induce selective 1,5- and 1,6-hydrogen-atom transfer followed by halogenation. Multiple halogenation events of up to four innate C?H bond functionalizations were accomplished. The broad applicability of this new entry into polyhalogenation and the resulting synthetic possibilities were demonstrated for a total of 27 different examples including mixed halogenations.
- Del Castillo, Estefanía,Martínez, Mario D.,Bosnidou, Alexandra E.,Duhamel, Thomas,O'Broin, Calvin Q.,Zhang, Hongwei,Escudero-Adán, Eduardo C.,Martínez-Belmonte, Marta,Mu?iz, Kilian
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supporting information
p. 17225 - 17229
(2018/11/10)
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- Reduction and Reductive Deuteration of Tertiary Amides Mediated by Sodium Dispersions with Distinct Proton Donor-Dependent Chemoselectivity
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A practical and scalable single electron transfer reduction mediated by sodium dispersions has been developed for the reduction and reductive deuteration of tertiary amides. The chemoselectivity of this method highly depends on the nature of the proton donor. The challenging reduction via C-N bond cleavage has been achieved using Na/EtOH, affording alcohol products, while the use of Na/NaOH/H2O leads to the formation of amines via selective C-O scission. Sodium dispersions with high specific surface areas are crucial to obtain high yields and good chemoselectivity. This new method tolerates a range of tertiary amides. Moreover, the corresponding reductive deuterations mediated by Na/EtOD-d1 and Na/NaOH/D2O afford useful α,α-dideuterio alcohols and α,α-dideuterio amines with an excellent deuterium content.
- Zhang, Bin,Li, Hengzhao,Ding, Yuxuan,Yan, Yuhao,An, Jie
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p. 6006 - 6014
(2018/05/24)
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- A process for preparing hydroxy adamantane glycine derivatives
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The invention aims to provide a novel and simple synthesis route of a hydroxyadamantylglycine derivative represented by the formula I, namely (aS)-a-[[(1,1-dimethylethoxy)carboxyl]-amino]-1-(3-hydroxyadamantyl)-acetic acid) or salts of the derivative through developing a novel compound. A novel compound namely 2(aS)-a-amino-1-adamantyl-acetamide represented by the formula III is taken as the primary raw material and then is subjected to hydrolysis reactions and hydroxy group introduction so as to obtain the (aS)-a-[[(1,1-dimethylethoxy)carboxyl]-amino]-1-(3-hydroxyadamantyl)-acetic acid) represented by the formula I or salts of the derivative. The invention further provides a synthesis method of the novel compound represented by the formula III. The synthesis method can solve the disadvantages that the cost of enzyme catalyzed reactions is high, the enzyme catalyzed reactions are unstable, the chemical catalysis method has a low ee value, and the reaction product is not easy to purify in the prior art, and thus is more suitable for industrial production.
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Paragraph 0014; 0015; 0016
(2017/07/14)
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- Ruthenium-Catalyzed Deaminative Hydrogenation of Aliphatic and Aromatic Nitriles to Primary Alcohols
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The deaminative hydrogenation of nitriles towards alcohols is a useful reaction to transform nitriles into alcohols with NH3 as the sole byproduct. Using the simple and robust RuHCl(CO)(PPh3)3 complex as a catalyst, at low H2 pressures a series of aliphatic and aromatic nitriles could be transformed into the corresponding alcohols. Suitable solvent systems for these reactions were 1,4-dioxane/water and EtOH/water mixtures. In most cases, the selectivity for the alcohols was excellent, and the corresponding amines were formed only in trace amounts.
- Molnár, István Gábor,Calleja, Pilar,Ernst, Martin,Hashmi, A. Stephen K.,Schaub, Thomas
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p. 4175 - 4178
(2017/10/09)
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- Rhenium-Loaded TiO2: A Highly Versatile and Chemoselective Catalyst for the Hydrogenation of Carboxylic Acid Derivatives and the N-Methylation of Amines Using H2 and CO2
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Herein, we report a heterogeneous TiO2-supported Re catalyst (Re/TiO2) that promotes various selective hydrogenation reactions, which includes the hydrogenation of esters to alcohols, the hydrogenation of amides to amines, and the N-methylation of amines, by using H2 and CO2. Initially, Re/TiO2 was evaluated in the context of the selective hydrogenation of 3-phenylpropionic acid methyl ester to afford 3-phenylpropanol (pH2 =5 MPa, =5 MPa, T=180 °C), which revealed a superior performance over other catalysts that we tested in this study. In contrast to other typical heterogeneous catalysts, hydrogenation reactions with Re/TiO2 did not produce dearomatized byproducts. DFT studies suggested that the high selectivity for the formation of alcohols in favor of the hydrogenation of aromatic rings is ascribed to the higher affinity of Re towards the COOCH3 group than to the benzene ring. Moreover, Re/TiO2 showed a wide substrate scope for the hydrogenation reaction (19 examples). Subsequently, this Re/TiO2 catalyst was applied to the hydrogenation of amides, the N-methylation of amines, and the N-alkylation of amines with carboxylic acids or esters.
- Toyao, Takashi,Siddiki,Morita, Yoshitsugu,Kamachi, Takashi,Touchy, Abeda S.,Onodera, Wataru,Kon, Kenichi,Furukawa, Shinya,Ariga, Hiroko,Asakura, Kiyotaka,Yoshizawa, Kazunari,Shimizu, Ken-Ichi
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supporting information
p. 14848 - 14859
(2017/10/27)
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- Tunable Ligand Effects on Ruthenium Catalyst Activity for Selectively Preparing Imines or Amides by Dehydrogenative Coupling Reactions of Alcohols and Amines
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Selective dehydrogenative synthesis of imines from a variety of alcohols and amines was developed by using the ruthenium complex [RuCl2(dppea)2] (6 a: dppea=2-diphenylphosphino-ethylamine) in the presence of catalytic amounts of Zn(OCOCF3)2 and KOtBu, whereas the selective dehydrogenative formation of amides from the same sources was achieved by using another ruthenium complex, [RuCl2{(S)-dppmp}2] [6 d: (S)-dppmp=(S)-2-((diphenylphosphenyl)methyl)pyrrolidine], in the presence of catalytic amounts of Zn(OCOCF3)2 and potassium bis(trimethylsilyl)amide (KHMDS). Our previously reported ruthenium complex, [Ru(OCOCF3)2(dppea)2] (8 a), was the catalyst precursor for the imine synthesis, whereas [Ru(OCOCF3)2{(S)-dppmp}2] (8 d), which was derived from the treatment of 6 d with Zn(OCOCF3)2 and characterized by single-crystal X-ray analysis, was the pre-catalyst for the amide formation. Control experiments revealed that the zinc salt functioned as a reagent for replacing chloride anions with trifluoroacetate anions. Plausible mechanisms for both selective dehydrogenative coupling reactions are proposed based on a time-course study, Hammett plot, and deuterium-labeling experiments.
- Higuchi, Takafumi,Tagawa, Risa,Iimuro, Atsuhiro,Akiyama, Shoko,Nagae, Haruki,Mashima, Kazushi
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supporting information
p. 12795 - 12804
(2017/09/06)
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- Conformationally Driven Two- and Three-Photon Cascade Processes in the Stereoselective Photorearrangement of Pyrroles
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A TBSO group has been shown to exert a high degree of stereocontrol during the two-photon photocycloaddition/rearrangement of N-butenylpyrroles to complex tricyclic aziridines. Moreover, this and other bulky groups have been shown to change the outcome of the reaction, promoting a new two-photon sequence to tricyclic imines and an unprecedented stereoselective three-photon sequence to azabicyclo[3.3.1]nonanes.
- Koovits, Paul J.,Knowles, Jonathan P.,Booker-Milburn, Kevin I.
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supporting information
p. 5608 - 5611
(2016/11/17)
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- METHOD FOR PRODUCING ALCOHOL BY HYDROGENATION OF CARBOXYLIC ACID COMPOUND, AND RUTHENIUM COMPLEX FOR USE IN THE PRODUCTION METHOD
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PROBLEM TO BE SOLVED: To provide a method of obtaining an alcohol by efficiently hydrogenating a variety of carboxylic acid compounds under mild conditions using a homogeneous catalyst. SOLUTION: The present invention provides a method of hydrogenating a carboxylic acid compound, in the presence of a ruthenium complex represented by RuXnYpZq, in an atmosphere of hydrogen [X is a group represented by the following formula; Y is a phosphine ligand having a substituted/unsubstituted alkyl group or a substituted/unsubstituted aryl group; Z is a ligand other than X and Y; n is 1 or 2; p is an integer of 1-4; q is an integer of 0-2] {R1 is H, a substituted/unsubstituted alkyl group or a substituted/unsubstituted aryl group; A1 and A2 independently represent O, NR4 (R4 is H, a substituted/unsubstituted alkyl group or a substituted/unsubstituted aryl group) or S; m is an integer of 1 or more; a solid line and a dashed line both represent a single bond or a double bond}]. SELECTED DRAWING: None COPYRIGHT: (C)2017,JPOandINPIT
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Paragraph 0133; 0137; 0138
(2017/02/02)
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- Intramolecular C-H Amination Reaction Provides Direct Access to 1,2-Disubstituted Diamondoids
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We present a new approach to disubstituted diamondoids from corresponding carboxylic acids. A dirhodium-acetate-catalyzed (1 mol-%) nitrene insertion reaction of sulfamides was, for the first time, applied to intramolecular C-H functionalization reactions of rigid tricyclic frameworks. This straightforward approach enables the effective and regioselective synthesis of a variety of diamondoid-based cyclic sulfamidates, which are synthetically valuable building blocks. Reductive deprotection of the sulfamidate moiety leads to corresponding 1,3-amino alcohol derivatives. Oxidation of the sulfamidate moiety by KMnO4 provides access to 1,3-keto alcohols or imines. Finally, we report the synthesis of Vildagliptin analogues as new antidiabetic drug candidates (DPP-4 inhibitors). Intramolecular dirhodium-acetate-catalyzed (1 mol-%) nitrene insertion reactions provide direct access to 1,2-disubstituted diamondoids. This approach was applied to the synthesis of Vildagliptin (DPP-4 inhibitor) analogues.
- Hrdina, Radim,Metz, Fabian M.,Larrosa, Marta,Berndt, Jan-Philipp,Zhygadlo, Yevgeniya Y.,Becker, Sabine,Becker, Jonathan
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supporting information
p. 6231 - 6236
(2015/10/06)
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- Access to nitriles from aldehydes mediated by an oxoammonium salt
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A scalable, high yielding, rapid route to access an array of nitriles from aldehydes mediated by an oxoammonium salt (4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate) and hexamethyldisilazane (HMDS) as an ammonia surrogate has been developed. The reaction likely involves two distinct chemical transformations: reversible silyl-imine formation between HMDS and an aldehyde, followed by oxidation mediated by the oxoammonium salt and desilylation to furnish a nitrile. The spent oxidant can be easily recovered and used to regenerate the oxoammonium salt oxidant.
- Kelly, Christopher B.,Lambert, Kyle M.,Mercadante, Michael A.,Ovian, John M.,Bailey, William F.,Leadbeater, Nicholas E.
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supporting information
p. 4241 - 4245
(2015/04/14)
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- Protected amino hydroxy adamantane carboxylic acid and process for its preparation
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Dipeptidyl peptidase IV (DP 4) inhibiting compounds are provided. The provided compounds can be used for treating diabetes and related diseases, especially Type II diabetes, and other diseases as set out herein, employing such DP 4 inhibitor or a combination of such DP 4 inhibitor and one or more of another antidiabetic agent such as metformin, glyburide, troglitazone, pioglitazone, rosiglitazone and/or insulin and/or one or more of a hypolipidemic agent and/or anti-obesity agent and/or other therapeutic agent.
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- Organoborane-Catalyzed Hydrogenation of Unactivated Aldehydes with a Hantzsch Ester as a Synthetic NAD(P)H Analogue
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We have developed a method for the hydrogenation of unactivated aldehydes, using a Hantzsch ester as a NAD(P)H analogue in the presence of an electron-deficient triarylborane as a Lewis acid catalyst. Thus, tris[3,5-bis(trifluoromethyl)phenyl]borane efficiently catalyzes the hydrogenation of aliphatic aldehydes with a Hantzsch ester in 1,4-dioxane at 100 °C to give the corresponding aliphatic primary alcohols in up to 97% yield. Aromatic aldehydes also undergo the hydrogenation, even at 25 °C, to furnish the corresponding aromatic primary alcohols in up to 100% yield.
- Hamasaka, Go,Tsuji, Hiroaki,Uozumi, Yasuhiro
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supporting information
p. 2037 - 2041
(2015/09/01)
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- Chemoselective ruthenium-catalysed reduction of carboxylic acids
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A very general and efficient catalytic protocol for the selective reduction of carboxylic acids to their corresponding alcohols under mild conditions is described. Various carboxylic acids, including benzoic acids, were reduced in good yields using the presented methodology. The ruthenium-catalysed method yields a highly chemoselective reduction permitting the reduction of a carboxylic acid functionality in the presence of numerous other potentially reducible moieties.
- Fernandez-Salas, Jose A.,Manzini, Simone,Nolan, Steven P.
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supporting information
p. 308 - 312
(2014/05/20)
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- A PROCESS FOR INDUSTRIAL PREPARATION OF [(S)-N-TERT BUTOXYCARBONYL-3-HYDROXY]ADAMANTYLGLYCINE
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A commercially viable process for industrial preparation of [(S)-n-tert butoxycarbonyl-3-hydroxy]adamantylglycine which is a key intermediate for saxagliptin synthesis and is represented by compound of Formula-VI. The compound-VI obtained by the process of present invention has more than 99.5% HPLC purity, not more than 0.15 % of dihydroxy impurity, not more than 0.05% of isomer impurity and not more than 0.1% of any unknown impurity. Formula (VI).
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- Mechanism of SmI2/amine/H2O-promoted chemoselective reductions of carboxylic acid derivatives (esters, acids, and amides) to alcohols
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Samarium(II) iodide-water-amine reagents have emerged as some of the most powerful reagents (E° = -2.8 V) for the reduction of unactivated carboxylic acid derivatives to primary alcohols under single electron transfer conditions, a transformation that had been considered to lie outside the scope of the classic SmI2 reductant for more than 30 years. In this article, we present a detailed mechanistic investigation of the reduction of unactivated esters, carboxylic acids, and amides using SmI2-water-amine reagents, in which we compare the reactivity of three functional groups. The mechanism has been studied using the following: (i) kinetic, (ii) reactivity, (iii) radical clock, and (iv) isotopic labeling experiments. The kinetic data indicate that for the three functional groups all reaction components (SmI2, amine, water) are involved in the rate equation and that the rate of electron transfer is facilitated by base assisted deprotonation of water. Notably, the mechanistic details presented herein indicate that complexation between SmI2, water, and amines can result in a new class of structurally diverse, thermodynamically powerful reductants for efficient electron transfer to a variety of carboxylic acid derivatives. These observations will have important implications for the design and optimization of new processes involving Sm(II)-reduction of ketyl radicals. (Chemical Equation Presented).
- Szostak, Michal,Spain, Malcolm,Eberhart, Andrew J.,Procter, David J.
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p. 11988 - 12003
(2015/01/16)
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- Highly chemoselective reduction of amides (primary, secondary, tertiary) to alcohols using SmI2/amine/H2O under mild conditions
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Highly chemoselective direct reduction of primary, secondary, and tertiary amides to alcohols using SmI2/amine/H2O is reported. The reaction proceeds with C-N bond cleavage in the carbinolamine intermediate, shows excellent functional group tolerance, and delivers the alcohol products in very high yields. The expected C-O cleavage products are not formed under the reaction conditions. The observed reactivity is opposite to the electrophilicity of polar carbonyl groups resulting from the nX → πC=O (X = O, N) conjugation. Mechanistic studies suggest that coordination of Sm to the carbonyl and then to Lewis basic nitrogen in the tetrahedral intermediate facilitate electron transfer and control the selectivity of the C-N/C-O cleavage. Notably, the method provides direct access to acyl-type radicals from unactivated amides under mild electron transfer conditions.
- Szostak, Michal,Spain, Malcolm,Eberhart, Andrew J.,Procter, David J.
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supporting information
p. 2268 - 2271
(2014/03/21)
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- Evaluating a sodium dispersion reagent for the Bouveault-Blanc reduction of esters
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A new sodium dispersion reagent has been evaluated for the reduction of esters. Na-D15, a sodium dispersion with sodium particle size of 5-15 μm, is a nonpyrophoric reagent that can be handled in air. In this study, a broad range of aliphatic ester substrates were reduced to primary alcohols by Na-D15/i-PrOH with good yields. The method compares favorably with modern metal hydride reductions and is much safer and efficient than the traditional Bouveault-Blanc reduction.
- An, Jie,Work, D. Neil,Kenyon, Craig,Procter, David J.
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p. 6743 - 6747
(2014/08/05)
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- Efficient hydroxymethylation reactions of iodoarenes using CO and 1,3-dimethylimidazol-2-ylidene borane
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A hydroxymethylation reaction of a variety of iodoarenes proceeded effectively in the presence of CO, NHC-borane, diMeImd-BH3 (2) as a radical mediator, and a catalytic amount of AIBN. The reaction took place chemoselectively at the aryl-iodine bond but not at the aryl-bromine and aryl-chlorine bonds. A three-component coupling reaction comprising aryl iodides, CO, and electron-deficient alkenes also proceeded well to give unsymmetrical ketones in good yields. Control experiments show that 2 would act as a hydrogen donor to acyl radicals and iodinated NHC-borane as a reducing agent of aldehydes.
- Kawamoto, Takuji,Okada, Takuma,Curran, Dennis P.,Ryu, Ilhyong
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supporting information
p. 2144 - 2147
(2013/06/05)
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- Preparative synthesis of vinyl diamondoids
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We describe a convenient four-step preparation of 1-vinyl adamantane, 1-vinyl diamantane, and 4,9-divinyl diamantane from the respective diamondoid acetic acids in 50-80% isolated yields involving esterification, reduction, and hydrobromination/dehydrobromination. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications to view the free supplemental file.
- Fokin, Andrey A.,Butova, Ekaterina D.,Barabash, Anastasiya V.,Huu, Nhan N.,Tkachenko, Boryslav A.,Fokina, Natalie A.,Schreiner, Peter R.
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p. 1772 - 1777
(2013/05/21)
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- Discovery of adamantane based highly potent HDAC inhibitors
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Herein, we report the development of highly potent HDAC inhibitors for the treatment of cancer. A series of adamantane and nor-adamantane based HDAC inhibitors were designed, synthesized and screened for the inhibitory activity of HDAC. A number of compounds exhibited GI50 of 10-100 nM in human HCT116, NCI-H460 and U251 cancer cells, in vitro. Compound 32 displays efficacy in human tumour animal xenograft model.
- Gopalan, Balasubramanian,Ponpandian, Thanasekaran,Kachhadia, Virendra,Bharathimohan, Kuppusamy,Vignesh, Radhakrishnan,Sivasudar, Velaiah,Narayanan, Shridhar,Mandar, Bhonde,Praveen, Rajendran,Saranya, Nithyanandan,Rajagopal, Sriram,Rajagopal, Sridharan
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p. 2532 - 2537
(2013/06/27)
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- Modernized low pressure carbonylation methods in batch and flow employing common acids as a CO source
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Carbonylation reactions, such as Heck, Sonogashira, and radical carbonylations, were successfully carried out in a two-chamber reactor where carbon monoxide was produced ex situ by the Morgan reaction (dehydration of formic acid by sulfuric acid). By a subsequent application in a microflow system using a tube-in-tube reactor where gas-permeable Teflon AF2400 was used as the inner tube, it is demonstrated that formic acid/sulfuric acid can be employed concomitantly with an amine base such as triethylamine in the Heck aminocarbonylation of aryl iodide.
- Brancour, Célia,Fukuyama, Takahide,Mukai, Yu,Skrydstrup, Troels,Ryu, Ilhyong
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supporting information
p. 2794 - 2797
(2013/07/19)
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- Reductions of aldehydes and ketones with a readily available N-heterocyclic carbene borane and acetic acid
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Acetic acid promotes the reduction of aldehydes and ketones by the readily available N-heterocyclic carbene borane, 1,3-dimethylimidazol-2-ylidene borane. Aldehydes are reduced over 1-24 h at room temperature with 1 equiv of acetic acid and 0.5 equiv of the NHC-borane. Ketone reductions are slower but can be accelerated by using 5 equiv of acetic acid. Aldehydes can be selectively reduced in the presence of ketones. On a small scale, products are isolated by evaporation of the reaction mixture and direct chromatography.
- Lamm, Vladimir,Pan, Xiangcheng,Taniguchi, Tsuyoshi,Curran, Dennis P.
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p. 675 - 680
(2013/05/21)
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- Uncovering the importance of proton donors in TmI2-promoted electron transfer: Facile C-N bond cleavage in unactivated amides
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Nonclassical lanthanide(II) iodides are modern reagents for the development of challenging electron-transfer processes. It was demonstrated that alcohols are critical for the formation of a thermodynamically more powerful reductant from TmI2 (thulium diiodide), the first nonclassical lanthanide(II) iodide in the series (TmI2, DyI2, NdI2). The TmI2(ROH)n reagent promotes an unprecedented cleavage of the σ C-N bond in amides. Copyright
- Szostak, Michal,Spain, Malcolm,Procter, David J.
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supporting information
p. 7237 - 7241
(2013/07/26)
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- Electron transfer reduction of carboxylic acids using SmI 2-H2O-Et3N
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The first general method for efficient electron transfer reduction of carboxylic acids has been developed. The protocol using SmI2 - H 2O - Et3N allows for reduction of a variety of carboxylic acids in excellent yields and provides an attractive alternative to processes mediated by reactive alkali metals, lithium aluminum hydride, and boron hydrides. Of broader significance, the method allows acyl radical equivalents to be generated from carboxylic acids under mild reaction conditions.
- Szostak, Michal,Spain, Malcolm,Procter, David J.
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supporting information; experimental part
p. 840 - 843
(2012/04/11)
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- An expedient route for the reduction of carboxylic acids to alcohols employing 1-propanephosphonic acid cyclic anhydride as acid activator
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A simple and efficient method for the synthesis of alcohols from the corresponding carboxylic acids is described. Activation of carboxylic acid with 1-propane phosphonic acid cyclic anhydride (T3P) and subsequent reduction of the intermediate phosphonic anhydride with NaBH4 yield the alcohol in excellent yields with good purity in less duration. Reduction of several alkyl/aryl carboxylic acids and Nα-protected amino acids/peptide acids as well as Nβ-protected amino acids was successfully carried out to obtain corresponding alcohols in good yields and the products characterized. The procedure is mild, safe, simple and the isolation of the products is easy.
- Nagendra,Madhu,Vishwanatha,Sureshbabu, Vommina V.
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experimental part
p. 5059 - 5063
(2012/09/22)
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- PROCESS FOR PREPARING SAXAGLIPTIN AND ITS NOVEL INTERMEDIATES USEFUL IN THE SYNTHESIS THEREOF
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Methods of making saxagliptin, pharmaceutically acceptable salts and hydrates thereof and intermediates thereof.
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- Radical addition of alkyl halides to formaldehyde in the presence of cyanoborohydride as a radical mediator. A new protocol for hydroxymethylation reaction
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Hydroxymethylation of alkyl halides was achieved using paraformaldehyde as a radical C1 synthon in the presence of tetrabutylammonium cyanoborohydride as a hydrogen source. The reaction proceeds via a radical chain mechanism involving an alkyl radical addition to formaldehyde to form an alkoxy radical, which abstracts hydrogen from a hydroborate anion.
- Kawamoto, Takuji,Fukuyama, Takahide,Ryu, Ilhyong
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supporting information; experimental part
p. 875 - 877
(2012/02/15)
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- Silica gel promotes reductions of aldehydes and ketones by N-heterocyclic carbene boranes
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N-Heterocyclic carbene boranes (NHC-boranes) such as 1,3-dimethylimidazol- 2-ylidine trihydridoborane (diMe-Imd-BH3) serve as practical hydride donors for the reduction of aldehydes and ketones in the presence of silica gel. Primary and secondary alcohols are formed in good yields under ambient conditions. Aldehydes are selectively reduced in the presence of ketones. One, two, or even all three of the boron hydrides can be transferred. The process is attractive because all the components are stable and easy to handle and because both the reaction and isolation procedures are convenient.
- Taniguchi, Tsuyoshi,Curran, Dennis P.
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p. 4540 - 4543
(2012/10/29)
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- Synthesis of alcohols from m-fluorophenylsulfones and dialkylboranes: Application to the C14-C35 building block of E7389
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The reaction of m-fluorophenylsulfone anions with dialkylboranes, followed by alkaline hydroperoxide oxidation, yields alcohols in high yields. Optimization of the process, scope and limitation, and application to the synthesis of one of the C14-C35 building blocks of E7389, a right half analogue of halichondrin B, are reported.
- Liu, Lei,Henderson, James A.,Yamamoto, Akihiko,Bremond, Paul,Kishi, Yoshito
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p. 2262 - 2265
(2012/06/30)
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- Preparation of samarium(II) iodide: Quantitative evaluation of the effect of water, oxygen, and peroxide content, preparative methods, and the activation of samarium metal
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Samarium(II) iodide (SmI2) is one of the most important reducing agents in organic synthesis. Synthetic chemistry promoted by SmI2 depends on the efficient and reliable preparation of the reagent. Unfortunately, users can experience difficulties preparing the reagent, and this has prevented realization of the full synthetic potential of SmI2. To provide synthetic chemists with general and reliable methods for the preparation of SmI2, a systematic evaluation of the factors involved in its synthesis has been carried out. Our studies confirm that SmI2 is a user-friendly reagent. Factors such as water, oxygen, and peroxide content in THF have little influence on the synthesis of SmI2. In addition, the use of specialized glovebox equipment or Schlenk techniques is not required for the preparation of SmI2. However, our studies suggest that the quality of samarium metal is an important factor and that the use of low quality metal is the main cause of failed preparations of the reagent. Accordingly, we report a straightforward method for activation of "inactive" samarium metal and demonstrate the broad utility of this protocol through the electron transfer reductions of a range of substrates using SmI2 prepared from otherwise "inactive" metal. An investigation into the stability of SmI2 solutions and an evaluation of commercially available solutions of the reagent is also reported.
- Szostak, Michal,Spain, Malcolm,Procter, David J.
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experimental part
p. 3049 - 3059
(2012/06/01)
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- HISTONE DEACETYLASE INHIBITORS FOR THE TREATMENT OF FUNGAL INFECTIONS
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Described are bridged compounds of the formula (I), their analogs, tautomeric forms, stereoisomers, geometrical isomers, polymorphs, hydrates, solvates, pharmaceutically acceptable salts, pharmaceutical compositions, metabolites and prodrugs thereof. The invention relates to compositions and methods to treat fungal infection. These compounds are selective HDAC inhibitors that act as inherent antifungal compounds or enhance the activity of other antifungal compounds such as azoles.
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- Electron transfer reduction of unactivated esters using SmI 2-H2O
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The reduction of unactivated esters using samarium diiodide is reported for the first time. The optimised protocol allows for the reduction of primary, secondary and tertiary alkyl esters in excellent yields and is competitive with reductions mediated by metal hydrides and alkali metals.
- Szostak, Michal,Spain, Malcolm,Procter, David J.
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supporting information; experimental part
p. 10254 - 10256
(2011/10/31)
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- Black-light-induced radical/ionic hydroxymethylation of alkyl iodides with atmospheric co in the presence of tetrabutylammonium borohydride
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(Figure Presented) Tin-free radical/ionic hydroxymethylation of secondary and tertiary alkyl iodides proceeded efficiently in the presence of tetrabutylammonium borohydride as the hydrogen source under atmospheric pressure of CO In conjunction with photoirradiation using black light. Two possible mechanisms were proposed, both of which involve hybrid radical/ionic processes.
- Kobayashi, Shoji,Kawamoto, Takuji,Uehara, Shohei,Fukuyama, Takahide,Ryu, Ilhyong
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supporting information; scheme or table
p. 1548 - 1551
(2010/07/06)
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- ACETAL COMPOUNDS AND THEIR PREPARATION, POLYMERS, RESIST COMPOSITIONS AND PATTERNING PROCESS
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An acetal compound of formula (1) is provided wherein R1 is H, methyl or trifluoromethyl, R2 is a monovalent C1-C10 hydrocarbon group, R3 and R4 are H or a monovalent C1-C10 hydrocarbon group, R2 and R3 may together form an aliphatic hydrocarbon ring, and X1 is a single bond or a divalent C1-C4 hydrocarbon group. A polymer comprising recurring units derived from the acetal compound is used as a base resin to formulate a resist composition which exhibits a high resolution when processed by micropatterning technology, especially ArF lithography.
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- An improved bouveault-blanc ester reduction with stabilized alkali metals
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Significantly improved Bouveault-Blanc conditions for ester reduction have been developed using sodium in silica gel (Na-SG), a free-flowing powder that can be easily handled in the open atmosphere. Primary alcohols were prepared in excellent yield from a variety of aliphatic esters under mild reaction conditions. The chemistry presented here is far safer than the classic Bouveault-Blanc reduction and is competitive with more modern hydride reduction methods.
- Bodnar, Brian S.,Vogt, Paul F.
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supporting information; experimental part
p. 2598 - 2600
(2009/08/07)
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- Preparation of 1-adamantyl ketones: Structure, mechanism of formation and biological activity of potential by-products
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Reactions between adamantane-1-carbonyl chloride and several Grignard reagents as well as interactions with solvents have been examined. Some new and unexpected adamantane derivatives were isolated, fully characterized and their biological activity determined. In particular, an unexpected isochromanone 16 was formed in an SEAr process, in which a stable hydrocarbon was the leaving group.
- Vicha, Robert,Necas, Marek,Potacek, Milan
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p. 709 - 722
(2008/02/01)
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