- En Route to a Practical Primary Alcohol Deoxygenation
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A long-standing scientific challenge in the field of alcohol deoxygenation has been direct catalytic sp3 C-O defunctionalization with high selectivity and efficiency, in the presence of other functionalities, such as free hydroxyl groups and amines widely present in biological molecules. Previously, the selectivity issue had been only addressed by classic multistep deoxygenation strategies with stoichiometric reagents. Herein, we propose a catalytic late-transition-metal-catalyzed redox design, on the basis of dehydrogenation/Wolff-Kishner (WK) reduction, to simultaneously tackle the challenges regarding step economy and selectivity. The early development of our hypothesis focuses on an iridium-catalyzed process efficient mainly with activated alcohols, which dictates harsh reaction conditions and thus limits its synthetic utility. Later, a significant advancement has been made on aliphatic primary alcohol deoxygenation by employing a ruthenium complex, with good functional group tolerance and exclusive selectivity under practical reaction conditions. Its synthetic utility is further illustrated by excellent efficiency as well as complete chemo- and regio-selectivity in both simple and complex molecular settings. Mechanistic discussion is also included with experimental supports. Overall, our current method successfully addresses the aforementioned challenges in the pertinent field, providing a practical redox-based approach to the direct sp3 C-O defunctionalization of aliphatic primary alcohols.
- Dai, Xi-Jie,Li, Chao-Jun
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supporting information
p. 5433 - 5440
(2016/05/19)
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- Ionic liquids - Promoted S-methylation of thiols utilizing dimethyl carbonate
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Convenient and efficient S-methylation of mercaptans or thiophenols occurs with dimethyl carbonate (DMC) in room temperature ionic liquids (RTILs) [Bmim]Cl. [Bmim]Cl can be recycled in four subsequent runs with only a gradual decrease in activity. A possible mechanism of this transformation is also discussed. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. Copyright Taylor & Francis Group, LLC.
- Xie, Jiangang,Wu, Chengyao,Christopher, Branford White,Quan, Jing,Zhu, Limin
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experimental part
p. 31 - 37
(2011/04/22)
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- Enantioselective synthesis of phenyl-ethanolamines through application of chiral sulfoxide
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Efficient enantioselective synthesis of (R)- and (S)-enantiomers of 2-(tert-butylamino)-1-(p-methoxyphenyl)-ethanol has been achieved in high enantiomeric excess by using asymmetric sulfoxide as a chiral auxiliary. The present synthetic approach was further extended to the asymmetric synthesis of (R)-salbutamol. Copyright Taylor & Francis Group, LLC.
- Sivakumar, Aathimanivelu V.,Lahoti, Anand M.,Bhat, Sujata V.
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experimental part
p. 3338 - 3347
(2011/03/19)
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- Trifluoromethylthiolation of 1,3-dithiane
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With a view to synthesize 2-(trifluoromethylthio)-1,3-dithiane (1), 1,3-dithiane (2) was reacted in dry pentane at -78°C under dry N2 with trifluoromethylsulfenyl chloride (3) and was found to furnish the desired compound in poor yields along with ten other compounds. Under similar conditions, 2-lithio-1,3-dithiane on treatment with 2 and bis-(trifluoromethyl) disulfide (4) gave 8.0% and 10.0% yields of 1, respectively. In connection with this study, (cholromethyl) propyl sulfide and bis(propylthio)methane were synthesized. The reaction of the latter with 3 was also investigated. The characterization of the primary compound formed in the reaction of 2 with 3 using the 'INAPT'-NMR and GC-MS, the probable mechanism of the formation of the various compounds and their mass spectral identification are presented in this article. Copyright Taylor & Francis Group, LLC.
- Munavalli,Rohrbaugh,Szafraniec,Durst
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p. 305 - 324
(2008/02/04)
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- Intermediacy of ion neutral complexes in the fragmentation of short-chain dialkyl sulfides
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The main fragmentation processes after electron ionization of butyl methyl and butyl ethyl sulfides are rationalized by the intermediacy of the ion neutral complex [RSH · methylcyclopropane](+·) as demonstrated by extensive labeling and collision activation studies.
- Filsak,Budzikiewicz
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p. 601 - 610
(2007/10/03)
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- New Synthetic Routes to Unsymmetrical Diorganyl Sulfides
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A number of new methods for preparing unsymmetrical diorganyl sulfides was proposed. The methods rely on generation of thiolate anions from thiols, isothiuronium salts, and disulfides in the system hydrazine hydrate-KOH, followed by alkylation of the anions with alkyl halides. The hydrazine hydrate plays the role of medium and reducing agent, which prevents side thiol oxidation. The yield of sulfides reaches 98%. The reaction products are readily separated from the aqueous-hydrazine layer and purified by distillation. The yield of sulfides is reduced by a deficit of alkali and by increasing chain length and functionalization of alkyl groups in the alkyl halide. The reactivity of alkyl halides is independent of the nature of the halogen. From isothiuronium salts, 2-pyridyl sulfides were obtained in the highest yields.
- Deryagina,Korchevin,Papernaya
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p. 812 - 815
(2007/10/03)
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- Synthesis of Trimethyl α-Keto Trithioorthoesters and Dimethyl α-Keto Dithioacetals by Reaction of Esters with Tris(methylthio)methyllithium
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A complete study has been made of the reaction of tris(methylthio)methyllithium with aromatic, heteroaromatic, and aliphatic esters.It is a one-pot reaction that despite its complexity, and depending on the reagent ratios, the reaction conditions, and the possible use of additional reagents (N-(methylthio)phthalimide or BuLi), can supply easily, in excellent and reproducible yields, the trimethyl α-keto trithioorthoesters 3 or, alternatively, the dimethyl α-keto dithioacetals 4.The reaction mechanism has been elucidated.
- Barbero, Margherita,Cadamuro, Silvano,Degani, Iacopo,Dughera, Stefano,Fochi, Rita
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p. 6017 - 6024
(2007/10/03)
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- Coenzyme F430 from Methanogenic Bacteria: Methane Formation by Reductive Carbon-Sulphur Bond Cleavage of Methyl Sulphonium Ions Catalysed by F430 Pentamethyl Ester
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The nickel(I)-form of coenzyme F430 pentamethyl ester is an efficient catalyst for the reductive cleavage of methyl sulphonium salts to methane and thioesters.
- Jaun, Bernhard,Pfaltz, Andreas
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p. 293 - 294
(2007/10/02)
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- New Oxyfunctionalization Capabilities for ω-Hydroxylases: Asymmetric Aliphatic Sulfoxidation and Branched Ether Demethylation
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Due to inherent difficulties in the chemical generation of aliphatic synthons, the stereo- and regioselective oxyfunctionalization of simple aliphatic substrates represents an area where chemical applications of biocatalysis would be particularly useful.The hydrocarbon monooxygenase from Pseudomonas oleovorans is a prototypical "ω-hydroxylase" known to carry out hydroxylation at the terminal methyl of alkanes as well as epoxidation of terminal olefins.It is now demonstrated that this enzyme system catalyzes stereoselective sulfoxidation of methyl thioether substrates, representing the first clear example of oxygenase-produced chiral aliphatic sulfoxides yet reported.In addition, it is shown that this enzyme system catalyzes oxygenative O-demethylation of branched alkyl methyl and branched vinyl methyl ethers to secondary alcohols and ketones, respectively.These findings establish new oxyfunctionalization capabilities, and thus a significantly expanded biotechnological potential, for the hydrocarbon monooxygenases.
- Katopodis, Andreas G.,Smith, Homer A.,May, Sheldon W.
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p. 897 - 899
(2007/10/02)
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- THIOPHILIC ADDITION OF ALKYLLITHIUM TO DITHIOCARBOXYLIC ACID ANIONS: SYNTHESIS OF 2--1,3-DITHIOLES
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2-lithio-4,5-disubstituted-1,3-dithioles react with CS2 in the presence of excess organolithium reagents yielding a product of thiophilic addition; subsequent alkylation furnished a new series of 2--1,3-dithioles.
- Moradpour, Alec,Bittner, Shmuel
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p. 3805 - 3808
(2007/10/02)
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