- Dual Mechanisms of Bimolecular Nucleophilic Subtitution of a Heterobenzylic Bromide Related to Thiamin
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4-Amino-5-(bromomethyl)-1,2-dimethylpyrimidinium ion at 25 deg C in 0.9 M KCl made to an ionic strength of 1 M with buffers react with hydroxide ion with a rate constant 725 M-1s-1.Evidence for an intermediate is found in the large common ion rate retarding effect of added bromide ion.An addition-elimination mechanism (SN(AE)) involving the addition of hydroxide ion to give a pseudobase intermediate followed by loss of bromide ion is advanced.Chloride ion reacts by an SN2 mechanism (5.9E-5 M-1s-1).When 2-thiopyridone acts as a nucleophile by the SN2 mechanism, its sulfur atom is heterobenzylated with a rate constant of 0.28 M-1s-1 (31 deg C).Two different bimolecular mechanisms of nucleophilic substitution are thereby observed.
- Zoltewicz, John A.,Uray, Georg
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Read Online
- Unusual Deoxidative Coupling Reaction of β-Sulfinyl Esters with Benzylic Trimethylammonium Salts
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A KOH-promoted unusual deoxidative coupling reaction of β-sulfinyl esters with benzylic trimethylammonium salts to produce thioethers is discovered for the first time. If quaternary ammonium salts synthesized from enantiomerically enriched amines are adopted, highly enantiomerically enriched benzyl thioethers (>95-99% ee) with configurations opposite to those of the enantiomerically enriched amines are obtained.
- Chen, Feng,Feng, Hang,He, Ze,Zeng, Qingle,Zhang, Qiaoling
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p. 7806 - 7812
(2021/06/25)
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- Transition metal-free coupling reactions of benzylic trimethylammonium salts with di(hetero)aryl disulfides and diselenides
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A new protocol was developed to synthesize (enantioenriched) thioethers and selenoethers from (chiral) benzylic trimethylammonium salts and di(hetero)aryl disulfides or diselenides. These syntheses were promoted by the presence of weak base and did not require the use of any transition metal, and resulted in the target products with good to excellent yields (72-94%). Using quaternary ammonium salts synthesized from enantiomerically enriched amines led to highly enantiopure benzylic thioethers and selenoethers (94-99% ee) with configurations reversed from those of their enantioenriched quaternary ammonium salts. This journal is
- Li, Fuhai,Wang, Dan,Chen, Hongyi,He, Ze,Zhou, Lihong,Zeng, Qingle
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p. 13029 - 13032
(2020/11/07)
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- Synthesis method of heteroaryl thioether
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The invention discloses a synthesis method of heteroaryl thioether. Under the conditions of no catalyst, no solvent, no additive and the like, aryl halide/2-bromopyridine, thiourea and substituted benzyl bromide which are directly taken as raw materials to selectively synthesize asymmetric heteroaryl thioether in one step without using conventional organic sulfides such as mercaptan or thiophenol.The use of organic sulfides with high toxicity and heavy odor, such as mercaptan or thiophenol, is avoided, and the synthesis steps are shortened, so that the synthesis efficiency is improved, the reaction has good selectivity, and the asymmetric thioether can be preferentially obtained.
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Paragraph 0019-0022
(2020/08/30)
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- Promoting Effect of Crystal Water Leading to Catalyst-Free Synthesis of Heteroaryl Thioether from Heteroaryl Chloride, Sodium Thiosulfate Pentahydrate, and Alcohol
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It is observed the crystal water in sodium thiosulfate pentahydrate (Na2S2O3·5H2O) can promote its multicomponent reaction with heteroaryl chlorides and alcohols, providing a facile, green, and specific synthesis of unsymmetrical heteroaryl thioethers via one-step formation of two C-S bonds under catalyst-, additive-, and solvent-free conditions. Mechanistic studies suggest that the crystal water in Na2S2O3·5H2O is crucial in generating the key thiol intermediates and byproduct NaHSO4, which then catalyzes the dehydrative substitution of alcohols with thiols to afford thioethers.
- Ma, Xiantao,Yu, Jing,Yan, Ran,Yan, Mengli,Xu, Qing
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supporting information
p. 11294 - 11300
(2019/09/12)
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- Synthesis of N-Alkylpyridin-4-ones and Thiazolo[3,2- a]pyridin-5-ones through Pummerer-Type Reactions
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N-Alkylated 4-pyridones were obtained through a one-pot procedure involving either normal or interrupted Pummerer reactions between triflic anhydride-activated sulfoxides and 4-fluoropyridine derivatives, followed by hydrolysis. On the other hand, triflic anhydride-activated benzyl 6-fluoro-2-pyridyl sulfoxide could react with alkenes or alkynes to afford thiazolo[3,2-a]pyridin-5-ones, via the pyridinium salt intermediates.
- Huang, Jingjia,Hu, Gang,An, Shaoyu,Chen, Dongding,Li, Minglei,Li, Pingfan
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p. 9758 - 9769
(2019/08/08)
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- Efficient Generation of C–S Bonds via a By-Product-Promoted Selective Coupling of Alcohols, Organic Halides, and Thiourea
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A metal- and base-free three-component coupling of alcohols, heteroaryl halides, and thiourea has been developed for direct and selective synthesis of heteroaryl thioethers. This method can be easily scaled up to the gram scale and extended to dialkyl thioethers, heteroaryl selenides, benzothiazoles, and some antimycobacterially-active thioethers. Mechanistic studies revealed that a by-product-promoted in situ C–O activation of alcohols to more reactive alkyl halides and slow release of the thiol and alkyl halide intermediates are the key to the high selectivity and success of the reaction. (Figure presented.).
- Ma, Xiantao,Yu, Lei,Su, Chenliang,Yang, Yaqi,Li, Huan,Xu, Qing
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p. 1649 - 1655
(2017/05/29)
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- Efficient dehydrative alkylation of thiols with alcohols catalyzed by alkyl halides
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Alcohols can be efficiently converted into the useful thioethers by a transition metal- and base-free dehydrative S-alkylation reaction with thiols or disulfides by employing alkyl halides as the effective catalyst. This simple and efficient method is a green and practical way for the preparation of thioethers, as it tolerates a wide range of substrates such as aryl and alkyl thiols, as well as benzylic, allylic, secondary, tertiary, and even the less reactive aliphatic alcohols.
- Yang, Yaqi,Ye, Zihang,Zhang, Xu,Zhou, Yipeng,Ma, Xiantao,Cao, Hongen,Li, Huan,Yu, Lei,Xu, Qing
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supporting information
p. 9638 - 9642
(2017/11/30)
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- Carbon-sulfur bond reductive coupling from a platinum(II) thiolate complex
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The room temperature addition of electrophilic alkyl halide reagents (RX = MeI, EtI and PhCH2Br) to complex [Pt(ppy)(η1-S-Spy)(PPh3)], 1a, in which ppyH = 2-phenylpyridine and pySH = pyridine-2-thiol, resulted in a rapid carbon-sulfur (C-S) bond reductive coupling to produce alkyl sulfides and corresponding halide complexes [Pt(ppy)(PPh3)X], X = I (2a) and Br (2b). A mechanism for this C-S bond formation reaction was suggested based on 1H and 31P {1H} NMR spectroscopic analyses. In the suggested mechanism, the reaction proceeded through a binuclear intermediate complex [{Pt(ppy)(PPh3)}2(μ2-Spy)]I, 3-I, which was separately synthesized by another counter anion (PF6) and it was fully characterized by multinuclear NMR spectroscopy and single X-ray crystallography. Also, density functional theory (DFT) calculations were used to theoretically assess the structures of intermediates and transition states in this bond formation reaction.
- Niazi, Maryam,Shahsavari, Hamid R.,Haghighi, Mohsen Golbon,Halvagar, Mohammad Reza,Hatami, Samaneh,Notash, Behrouz
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p. 95073 - 95084
(2016/10/22)
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- Efficient synthesis of unsymmetrical heteroaryl thioethers and chalcogenides by alkali hydroxide-mediated SNAr reactions of heteroaryl halides and dichalcogenides
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An efficient alkali hydroxide-mediated SNAr reaction of heteroaryl halides has been developed for the practical synthesis of the useful unsymmetrical heteroaryl thioethers and chalcogenides. The usually odorless, easily available, lowly toxic, and easily stored and handled diorganyl dichalcogenides can be used as safer and convenient chalcogen nucleophile precursors and diverse unsymmetrical heteroaryl chalcogenides can be obtained in good to high yields by the method.
- Ma, Xiantao,Liu, Quan,Jia, Xiaojuan,Su, Chenliang,Xu, Qing
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p. 56930 - 56935
(2016/07/06)
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- Versatile C(sp2)?C(sp3) Ligand Couplings of Sulfoxides for the Enantioselective Synthesis of Diarylalkanes
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The reaction of chiral (hetero)aryl benzyl sulfoxides with Grignard reagents affords enantiomerically pure diarylalkanes in up to 98 % yield and greater than 99.5 % enantiomeric excess. This ligand coupling reaction is tolerant to multiple substitution patterns and provides access to diverse areas of chemical space in three operationally simple steps from commercially available reagents. This strategy provides orthogonal access to electron-deficient heteroaromatic compounds, which are traditionally synthesized by transition metal catalyzed cross-couplings, and circumvents common issues associated with proto-demetalation and β-hydride elimination.
- Dean, William M.,?iau?iulis, Mindaugas,Storr, Thomas E.,Lewis, William,Stockman, Robert A.
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supporting information
p. 10013 - 10016
(2016/08/16)
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- Palladium-Catalyzed Remote ortho-C-H Alkenylation of Alkyl Aryl Sulfones: Access to Densely Functionalized Indane Derivatives
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A practical method for the palladium-catalyzed ortho-olefination of benzyl and phenethyl 2-pyridyl sulfones with electron-deficient alkenes using N-fluoro-2,4,6-trimethylpyridinium triflate ([F+]) as the terminal oxidant is described. The chela
- Legarda, Pablo D.,García-Rubia, Alfonso,Gómezarrayás, Ramón,Carretero, Juan C.
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supporting information
p. 1065 - 1072
(2016/04/19)
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- Enantioselective Sulfoxidation Catalyzed by a Bisguanidinium Diphosphatobisperoxotungstate Ion Pair
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The first enantioselective tungstate-catalyzed oxidation reaction is presented. High enantioselectivities were achieved for a variety of drug-like phenyl and heterocyclic sulfides under mild conditions with H2O2, a cheap and environmentally friendly oxidant. Synthetic utility was demonstrated through the preparation of (S)-Lansoprazole, a commercial proton-pump inhibitor. The active ion-pair catalyst was identified to be bisguanidinium diphosphatobisperoxotungstate using Raman spectroscopy and computational studies.
- Ye, Xinyi,Moeljadi, Adhitya Mangala Putra,Chin, Kek Foo,Hirao, Hajime,Zong, Lili,Tan, Choon-Hong
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supporting information
p. 7101 - 7105
(2016/07/06)
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- The effect of nitrogen atoms in the enantioselective oxidation of aryl or heteroaryl benzyl sulfides
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Some aminophenyl benzyl sulfides or benzyl pyridyl sulfides were asymmetrically oxidized with tert-butyl hydroperoxide in the presence of a complex between titanium i-propoxide and (S, S)-hydrobenzoin, an oxidation system that works particularly well with
- Capozzi, Maria Annunziata M.,Fracchiolla, Giuseppe,Cardellicchio, Cosimo
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p. 646 - 650
(2014/01/06)
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- Iodine-mediated thioetherification of alcohols with disulfides or NaSh under microwave irradiation
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An efficient and novel method for the thioetherification of an alcohol with disulfides or NaSH under microwave irradiation is presented. In the presence of iodine, a variety of alcohols were smoothly S-alkylated with disulfides or NaSH to give the corresponding thioethers in moderate to excellent yields. Copyright
- Hu, Bolun,Sun, Leilei,Tang, Riyuan,Hu, Huanan
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p. 2556 - 2562,7
(2020/09/16)
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- Microwave-assisted Ullmann-Buchwald C-S bond formation using a copper(I) catalyst and trans-cyclohexane-1,2-diol as ligand
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Microwave irradiation of a thiophenol or alkyl thiol (1 equiv.) and an aryl halide (1 equiv.) in 2-propanol at 120°C for three hours in the presence of K2CO3 (2 equiv.) as base using copper(I) iodide as catalyst (5 mol%) and trans-cyclohexane-1,2-diol (2 equiv.) as ligand provides a rapid and convenient method for C-S bond formation. The process is most efficient using thiophenol and aryl iodide precursors, both of which may contain electron-donating and electronwithdrawing groups, to give the corresponding diaryl sulfide in good to excellent yield. ARKAT-USA, Inc.
- Bagley, Mark C.,Fusillo, Vincenzo,Hills, Edward G.B.,Mulholland, Alex T.,Newcombe, Joseph,Pentecost, Leanne J.,Radley, Emily L.,Stephens, Bethan R.,Turrell, Christopher C.
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p. 294 - 313
(2013/01/16)
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- Preparation of N-alkyl 2-pyridones via a lithium iodide promoted oto N-alkyl migration: Scope and mechanism
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An efficient and inexpensive LiI-promoted O- to N-alkyl migration of 2-benzyloxy-, 2-allyloxy-, and 2-propargyloxypyridines and heterocycles is reported. The reaction produces the corresponding N-alkyl 2-pyridones and analogues under green, solvent-free conditions in good to excellent yields (30 examples, 20-97% yield). This method has been shown to be intermolecular and requires heat and lithium cation to occur.
- Tasker, Sarah Z.,Bosscher, Michael A.,Shandro, Christina A.,Ryu, Keun Ah,Snapper, Gregory S.,Utter, Jarrad M.,Anderson, Carolyn E.,Lanni, Erica L.,Ellsworth, Bruce A.
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p. 8220 - 8230,11
(2020/10/15)
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- Development of UV-responsive catch-and-release system of a cysteine protease model peptide
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Cysteine proteases are attractive drug targets due to their involvement in a wide variety of diseases. To evaluate the potential of a particular protease as a drug target, use of a reagent that controls activity of the protease is indispensable. In this context, we have developed a catch-and-release reagent that first forms a covalent bond with the active center thiol of a cysteine protease to suppress its activity and then is removed by UV-irradiation to release the parent active protease. In this paper, the design and synthesis of a catch-and-release reagent of thiols are described. Its application to caging (catch) and UV-induced uncaging (release) of a model peptide derived from an active site of caspase-9 and introduction of a recognition moiety on the reagent are also reported.
- Shigenaga, Akira,Morishita, Ko,Yamaguchi, Keiko,Ding, Hao,Ebisuno, Koji,Sato, Kohei,Yamamoto, Jun,Akaji, Kenichi,Otaka, Akira
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experimental part
p. 8879 - 8886
(2011/12/03)
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- Mild addition of nucleophiles to pyridine-N-oxides
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A general and facile one-pot procedure for the synthesis of 2-substituted pyridines from the corresponding pyridine-N-oxides and nucleophiles is presented as a mild alternative to SNAr chemistry. A variety of nucleophiles and heterocyclic-N-oxi
- Londregan, Allyn T.,Jennings, Sandra,Wei, Liuqing
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supporting information; experimental part
p. 1840 - 1843
(2011/05/15)
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- Studies on the reactive species in fluoride-mediated carbon-carbon bond-forming reactions: Carbanion formation by desilylation with fluoride and enolates
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The reactive species in fluoride-mediated carbon-carbon bond-forming reactions was investigated. The regio- and diastereoselectivities of silanes reacting with cyclohexenone in the presence of a catalytic amount of fluoride was compared to the reactivity of analogous solvent-separated lithium ion pairs. Closely analogous behavior was observed, showing that carbanions and not siliconate complexes are the reactive species in the fluoride-catalyzed reactions. Spectroscopic investigations unambiguously show that phenylthiobenzyl anion will form by reaction of silane with tris(dimethylamino)sulfonium difluorotrimethylsilicate (TASF) or crypt[2.1.1]-solvated lithium enolates. The catalytic cycle runs smoothly with the crypt[2.1.1] complex of α-(phenylthio)benzyllithium as the initiator and enolate as the carrier of the desilylation reaction.
- Biddle, Margaret M.,Reich, Hans J.
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p. 4031 - 4039
(2007/10/03)
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- Antimycobacterial Agents. 1. Thio Analogues of Purine
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Thio analogues of purine, pyridine, and pyrimidine were prepared based on the initial activity screening of several analogues of these heterocycles against Mycobacterium tuberculosis (Mtb). Certain 6-thio-substituted purine analogues described herein showed moderate to good inhibitory activity. In particular, two purine analogues 9-(ethylcarboxymethyl)-6-(decylthio)-9H-purine (20) and 9-(ethylcarboxymethyl)-6-(dodecylthio)-9H-purine (21) exhibited MIC values of 1.56 and 0.78 μg/mL respectively against the Mtb H37Rv strain. N9-Substitution apparently enhances the antimycobacterial activity in the purine series described herein.
- Pathak, Ashish K.,Pathak, Vibha,Seitz, Lainne E.,Suling, William J.,Reynolds, Robert C.
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p. 273 - 276
(2007/10/03)
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- A novel method for the stereoselective synthesis of tetralins and indanes
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Heavily-substituted 1-aryltetralins and 1-arylindanes were prepared in a highly stereoselective manner using a two-step sequence. Addition of t-butyl benzyl sulfoxides to unsaturated carbonyl compounds gave conjugate adducts with high diastereoselectivity
- Appelbe, Zelda,Casey, Mike,Keaveney, Claire M.,Kelly, Cornelius J.
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p. 1404 - 1408
(2007/10/03)
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- Synthesis of alkylthio- and arylthioheteroarenes by regioselective grignard reaction of thiocyanatoheteroarenes
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Treatment of thiocyanatoheteroarenes (1) with Grignard reagents (2) afforded alkylthio- or arylthioheteroarenes (3-6) in good yields. Grignard reagents regioselectively attacked the sulfur atom of the thiocyanato group owing to the metal-chelating effect of this group in combination with the hetero ring-nitrogen. 2-Thiocyanatopyridine (1a), 2-thiocyanatopyrimidine (1b), 2-thiocyanatobenzothiazole (1c), and 4-thiocyanatoquinazoline (1d) were converted into a variety of sulfides. Sulfides consisting of two heteroarenes linked by a sulfur atom were readily obtained by this method.
- Nagasaki, Izuru,Matsumoto, Miyuki,Yamashita, Masanori,Miyashita, Akira
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p. 1015 - 1024
(2007/10/03)
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- Intramolecular homolytic substitution with amidyl radicals: A free-radical synthesis of ebselen and related analogues
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Irradiation of a water-cooled benzene solution of pyridine-2-thioneoxycarbonyl (PTOC) imidate esters 9 derived from N-butyl-2-(benzylseleno)benzamide (6, R = Bu), 2-(benzylseleno)-N-hexylbenzamide (6, R = Hex), N-benzyl-2-(benzylseleno)benzamide (6, R = Bn), and 2-(benzylseleno)-N-cyclohexylbenzamide (6, R = c-Hex) with a 250-W low-pressure mercury lamp affords the corresponding 1,2-benzisoselenazol-3(2H)-ones (1) in yields of 81-91% (R = primary alkyl) and 45% (R = c-Hex). Presumably, these transformations involve formation of amidyl radicals 2 which undergo subsequent intramolecular homolytic substitution at the selenium atom with expulsion of a benzyl radical. PTOC imidate esters derived from 2-(benzylseleno)benzanilide (6, R = Ph) and 2-(benzylseleno)-N-tert-butylbenzamide (6, R = t-Bu) were unable to be prepared in this manner. 1,2-Benzisoselenazol-3(2H)-ones (1, R = Ph, Hex, i-Pr, t-Bu) could also be prepared in 76-85% yield by reaction of the corresponding 2,2'-diselenobis(benzamide) (15) with benzoyl or tert-butyl peroxide. The mechanisms of these transformations are discussed.
- Fong, Mei C.,Schiesser, Carl H.
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p. 3103 - 3108
(2007/10/03)
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- Oxidation potential as a measure of the reactivity of anionic nucleophiles. Behaviour of different classes of nucleophiles
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Anodic peak potentials for 42 anionic nucleophiles are reported along with the rate constants for the reactions of the anions with benzyl chloride.By comparing these rate constants with those of the reactions of outer-sphere electron-transfer reagents (radical anions), it has been demonstrated that the reactions of the anions with benzyl chloride are typical single-step SN2 reactions as opposed to a two-step process comprising dissociative single electron transfer (SET) to benzyl chloride followed by radical combination.The data suggest that very electron-rich nucleophilic anions with potentials of -1.5 to -2.2 V (and more negative) with respect to the ferrocenium/ferrocene couple might participate in a SET reaction.The 42 anions studied included representatives of four classes of nucleophiles, viz. sulfur-, carbon-, oxygen- and nitrogen-centred anions.The previously observed correlation of rate constants and anodic peak potential was again found for these anions with the most reactive species having the most negative peak potentials.Correlations by class indicate that the sensitivity of rate constants to changes in peak potential is greatest (and equivalent) for the sulfur-, carbon- and oxygen-anions and for representatives with the same peak potential, the rate constants by class follow the order sulfur > carbon > oxygen.The nitrogen nucleophiles show a significantly lower sensitivity of rate constant to changes in peak potential than do the other three classes.
- Niyazymbetov, Murat E.,Rongfeng, Zhou,Evans, Dennis H.
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p. 1957 - 1962
(2007/10/03)
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- A facile preparation method for α,α-difluoroalkanecarboxylic acids and esters. A formal difluoromethylene insertion to alkanecarboxylic acids using radical reaction
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Various alkyl radicals generated by the photoreaction of a series of Barton esters reacted with 1,1-dichloro-2,2-difluoroethene to give radical adducts as the major product accompanied with self-trapping products. Primary, secondary, tertiary, benzyl, and some unsaturated alkyl radicals as well as those with another functional group such as ether, carbonyl, and azide were applicable. Barton esters of diacids also afford 1:2 adducts with a small amount of 1:1 adducts and bis-self-trapping products except for the succinic case. These adducts were hydrolyzed with AgNO3/H2O-THF to α,α-difluoroalkanecarboxylic acids and methanolyzed with AgNO3/MeOH to the corresponding methyl esters. 4-Azido-2,2-difluorobutylic acid and the methyl ester were converted to difluoro-GABA and difluoro-γ-lactams.
- Okano, Takashi,Takakura, Nobuyuki,Nakano, Yuko,Okajima, Asako,Eguchi, Shoji
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p. 1903 - 1920
(2007/10/02)
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- Homolytic substitution by iminyl radical at selenium: A free-radical route to 1,2-benzoselenazoles
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Thiohydroxamic esters (3) derived from the O-carboxymethyl oxime derivatives (2) of 2-(benzylseleno)-benzaldehyde (1: R = H), 2-(benzylseleno)acetophenone (1: R = Me) and 2-(benzylseleno)propiophenone (1: R = Et) decompose smoothly, upon irradiation, with the loss of carbon dioxide and formaldehyde to give the 1,2-benzoselenazoles (5). The reaction presumably involves the iminyl radical intermediate (4) which undergoes intramolecular free-radical homolytic substitution at selenium to afford the product (5).
- Fong, Mei C.,Schiesser, Carl H.
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p. 4347 - 4348
(2007/10/02)
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- α,α-Difluoroalkanecarboxylic acids: A general synthesis via alkyl radical addition to 1,1-dichloro-2,2-difluoroethylene
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Photodecomposition of alkanoic acid esters of N-hydroxy-2-thiopyridone with 1,1-dichloro-2,2-difluoroethylene gives alkyl-radical-trapped products, which give α,α-difluoroalkanoic acids and their methyl esters on hydrolytic or methanolytic treatment with silver nitrate.
- Okano,Takakura,Nakano,Eguchi
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p. 3491 - 3494
(2007/10/02)
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- Conversion of Hydroxyl Groups in Alcohols to Other Functional Groups with N-Hydroxy-2-thiopyridone, and Its Application to Dialkylamines and Thiols
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The radical decarboxylation reaction of N-alkoxyoxalyloxy-2-thiopyridone which was prepared by the reaction of alcohol, oxalyl chloride, and N-hydroxy-2-thiopyridone was studied both in the absence and presence of olefinic compounds.The same reactions with olefinic and acetylenic alcohols gave the corresponding lactone derivatives.On the other hand the unsymmetrical alkyl 2-pyridyl disulfides were obtained by the same reaction with aliphatic thiols.
- Togo, Hideo,Fujii, Misa,Yokoyama, Masataka
-
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- Studies on the stereoselective methylation of α-sulfinyl carbanions generated from three isomeric pyridylmethyl π-tolyl sulfoxides and benzyl 2-pyridyl sulfoxide
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A high stereoselectivity in the methylation of 2-pyridylmethyl p-totyl sulfoxide (2a) with lithium diisopropylamide and iodomethane was observed at low temperature. The chelation of Li+ by both the nitrogen atom in the pyridine ring and the sulfinyl oxygen atom in 2a promotes the stereoselectivity as compared with isomeric sulfoxides.
- Furukawa,Hosono,Fujihara,Ogawa
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p. 461 - 465
(2007/10/02)
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- OCCURRENCE OF LIGAND COUPLING IN THE REACTIONS OF VARIOUS SULFOXIDES WITH GRIGNARD REAGENTS
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Ligand coupling reactions take place not only between benzyl and 2-pyridyl groups and two 2-pyridyl groups in the treatment of benzyl, alkyl and aryl 2-pyridyl sulfoxides with Grignard reagents, but also between such groups as p-benzenesulfonylphenyl, 4-pyridyl, 2-quinolyl and 2-pyrimidyl, and the benzyl group.There are cases in which ligand exchange precedes ligand coupling, especially with 2-heteroaryl groups.In addition, even some alkyl groups were found to couple with the 2-pyridyl group.The ease of coupling seems to be associated with the electronegativity of the coupling carbon atom of the ligand, when one compares the 13C NMR chemical shifts.
- Kawai, Tsutomu,Kodera, Yoichi,Furukawa, Naomichi,Oae, Shigeru,Ishida, Masahiro,et al.
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p. 139 - 148
(2007/10/02)
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- THE INVENTION OF RADICAL REACTIONS. PART XV. SOME MECHANISTIC ASPECTS OF THE DECARBOXYLATIVE REARRANGEMENT OF THIOHYDROXAMIC ESTERS
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Esters (mixed anhydrides) derived from aliphatic or alicyclic carboxylic acids (RCO2H) and thiohydroxamic acids 2 or 3 undergo a thermally or photochemically induced radical chain reaction to give sulphides 4 with loss of carbon dioxide.On irradiation at low temperature however, the chain reaction is essentially suppressed.Under these conditions moderate to good yields of dimers R-R are obtained from primary acids.The mechanistic and synthetic implications of these observations are discussed.
- Barton, Derek H. R.,Bridon, Dominique,Fernandez-Picot, Isabel,Zard, Samir Z.
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p. 2733 - 2740
(2007/10/02)
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- Benzylation of Thioamides and Thioureas with Triethylbenzylammonium Chloride Under Phase Transfer Catalysis
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The reactions of triethylbenzylammonium chloride with thioamides/thioureas under phase transfer catalysis conditions provide mainly S-benzylated products.The reactions have been rationalised and optimum condition worked out to get the maximum yield of the
- Singh, Paramjit,Aggarwal, Sunil K.,Sarin, Rakesh,Malhotra, Nageshwar,Singh, Harjit
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p. 263 - 265
(2007/10/02)
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- THE INVENTION OF NEW RADICAL CHAIN REACTIONS. PART VIII. RADICAL CHEMISTRY OF THIOHYDROXAMIC ESTERS; A NEW METHOD FOR THE GENERATION OF CARBON RADICALS FROM CARBOXYLIC ACIDS.
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The aliphatic and alicyclic esters of N-hydroxy-pyridine-2-thione are readily reduced by tributylstannane in a radical chain reaction to furnish nor-alkanes.In the absence of the stannane a smooth decarboxylative rearrangement occurs to give 2-substituted thiopyridines.The radicals present in this reaction provoke with t-butylthiol an efficient radical reaction with formation of nor-alkane and 2-pyridyl-t-butyl disulphide.Similarly these carbon radicals can be captured by halogen atom transfer to give noralkyl chlorides, bromides and iodides.With oxygen in the presence of t-butylthiol the corresponding noralkyl hydroperoxides are formed in another radical chain reaction.
- Barton, Derek H. R.,Crich, David,Motherwell, William B.
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p. 3901 - 3924
(2007/10/02)
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- ipso-Substitution of a Sulphinyl or Sulphonyl Group Attached to Pyridine Rings and its Application for the Synthesis of Macrocycles
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A sulphinyl or sulphonyl group directly bound to the 2- or 4-position of a pyridine ring was readily displaced by several nucleophiles such as RO-, RS-, and CN- to afford the corresponding ipso-substitution products.Similarly, 2-halogeno-6-methylsulphinyl- or -methylsulphonyl-pyridines also react with nuclephiles to afford 2-halogeno-6-substituted pyridine derivatives.Thus, the leaving abilities of the leaving groups fall in the order RSO2 > RSO > Br ca.Cl >> RS (R = alkyl or benzyl).The ipso-substitution can be applied to the synthesis of 2,6-disubstituted pyridino macrocycles containing both carbon-oxygen and carbon-sulphur bridges, resulting in several new macrocycles in moderate yields.
- Furukawa, Naomichi,Ogawa, Satoshi,Kawai, Tsutomu,Oae, Shigeru
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p. 1839 - 1845
(2007/10/02)
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- Syntheses and Some Properties of Sulfoxides, Sulfilimines, Aminosulfonium Salts and Sulfoximines Containing Pyridine Nuclei
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Several 2-pyridyl sulfides (1) (e.g., methyl (1a), ethyl (1b), isopropyl (1c), benzyl (1d), 1-phenylethyl (1e), l-menthyl (1f) 2-pyridyl sulfides); and bis(2-pyridylthio)methane (1g), and methyl 2-(N-oxy-pyridyl) sulfide (1h) were prepared by the usual method.Sulfoxides (2) were prepared by oxidation of the corresponding sulfides with m-chloroperbenzoic acid in good yields.A few sulfoxides were found to work as phase-transfer catalysts for some typical nucleophilic reactions in nonpolar solvents such as benzene, and in two-phase systems such as benzene-water.S-2-Pyridyl-N-(p-toluenesulfonyl) sulfinilimines (3) were prepared upon treatment of sulfides with Chloramine-T.Hydrolysis of N-(p-toluenesulfonyl)-2-pyridyl-o-tolylsulfilimine (3i) with conc. sulfuric acid gave the corresponding free sulfilimine in a moderate yield.S-2-Pyridyl sulfoximines (4) were not obtained by the general method from the sulfoxides and hydrazoic acid.Alkyl-2-pyridyl sulfoximines, however, were obtained by oxidation of the free sulfilimines derived from the corresponding aminosulfonium salts (5) prepared by reaction of the sulfides with mesitylene-sulfonylhydroxylamine (MSH).These free sulfilimines and sulfoximines thus prepared were found to give adducts with a few copper salts.
- Furukawa, Naomichi,Takahashi, Fujio,Tsutomu, Kawai,Kishimoto, Keiko,Ogawa, Satoshi,Oae, Shigeru
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p. 167 - 180
(2007/10/02)
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- Synthesis of 5'-Alkylthio-5'-deoxynucleosides from Nucleosides in a One-pot Reaction
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5'-Alkyl(aryl)thio-5'-deoxynucleosides were prepared in high yields by the reaction of nucleosides with dialkyl or diaryl disulphides in the presence of tri-n-butylphosphine.The method is widely applicable to the synthesis of unsymmetrical sulphides.
- Nakagawa, Iwao,Aki, Koichi,Hata, Tsujiaki
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p. 1315 - 1318
(2007/10/02)
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- Photostimulated Reactions of Alkanethiolate Ions with Haloarenes. Electron Transfer vs. Fragmentation of the Radical Anion Intermediate
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The photostimulated reactions of RS(1-) ions (R = methyl, n-butyl, tert-butyl, and benzyl) with haloarenes in liquid ammonia were studied.Two main products were formed: alkyl aryl sulfide and arenethiolate ions.The formation of these compounds is explained by the SRN1 mechanism of aromatic nucleophilic substitution.The radical anion intermediate formed in the coupling of an aryl radical with an alkanethiolate ion undergoes two competing reactions: transfer of the odd electron to the substrate leading to the substitution product or bond fragmentation leading to arenethiolate ion and an alkyl radical.It is concluded that the ratio of these products depends mainly on changes in the rate of fragmentation and not on changes in the electron-transfer reaction.
- Rossi, Roberto A.,Palacios, Sara M.
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p. 5300 - 5304
(2007/10/02)
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- Treatment of ulcers and hypertension
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The invention concerns the treatment of ulcers and hypersecretion in a mammal using compounds of the formula I where Ar is phenyl, which may be substituted or cycloalkyl of 5 to 7 carbon atoms, A is saturated or unsaturated lower alkylene which may be
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