- Phthalimidosulphenyl chloride part 2. Synthesis of unusual thiirane derivatives
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Vinylthio phthalimides 1, synthesized by addition of phtalimidosulphenyl chloride to some alkynes, react with 2 equivalents of lithiumtriethylboron hydride to give vinylthio substituted thiiranes 3 with high degree of diasteroselectivity. The reaction of
- Capozzi,Gori,Menichetti
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- Cycloaddition of thiophene S-oxides to allenes, alkynes and to benzyne
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Thiophenes have been treated with alkynes in the presence of m-chloroperoxybenzoic acid to give substituted arenes as cycloadducts. Alternatively, thiophene S-oxides have been prepared by oxidation from thiophenes and have been subjected to cycloaddition with alkynes in a subsequent step. The outcome of the reaction is dependent on the steric demand of the thiophene S-oxide. Some thiophene S-oxides can be reacted at temperatures as high as 140°C without decomposition. Thiophenes as deoxygenated products are the main by-products. Reactions of thiophene S-oxides with allenes give in part thiabicyclo[2.2.1]heptene S-oxides of type 12a and 13 along with aromatized products. Thiophene S-oxides also cycloadd to benzyne.
- Thiemann, Thies,Fujii, Hideki,Ohira, Daisuke,Arima, Kazuya,Li, Yuanqiang,Mataka, Shuntaro
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p. 1377 - 1384
(2007/10/03)
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- Synthesis, properties, oxidation, and electrochemistry of 1,2- dichalcogenins
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Syntheses are presented of the 1,2-dichalcogenins: 1,2-dithiin, 1,2- diselenin, and 2-selenathiin, both substituted and unsubstituted. 1,2-Dithiin and 1,2-diselenin are prepared by reaction of PhCH2XNa (X = S or Se) with 1,4-bis(trimethylsilyl)-1,3-butadiyne followed by reductive cleavage and oxidation. 2-Selenathiin is similarly prepared using a mixture of PhCH2SeNa and PhCH2SNa. Reaction of titanacyclopentadienes with (SCN)2 or (SeCN)2 followed by bis(thiocyanate) or bis(selenocyanate) cyclization affords substituted 1,2-dithiins or 1,2-diselenins, respectively. With S2Cl2, 1,2- dithiins are directly formed from titanacyclopentadienes. Oxidation of 1,2- dithiins and 1,2-diselenins gives the corresponding 1-oxide and, with 1,2- dithiins and excess oxidant, 1,1-dioxides; oxidation of 2-selenathiin gives the 2-oxide. Electrochemical oxidation of 1,2-dichalcogenins, which have a twisted geometry, affords planar radical cations by an EC mechanism. One- electron AlCl3 oxidation of 3,6-diphenyl-1,2-dithiin gives the corresponding radical cation, characterized by EPR spectroscopy. Theoretical calculations result in a flattened structure for the 1,2-dithiin radical cation and a fully planar structure for the 1,2-diselenin radical cation. The 77Se NMR chemical shifts of 1,2-diselenin are characteristically high-field-shifted with respect to open chain diselenides in good agreement with results of GIAO-DFT calculations based on MP2 and DFT optimum geometries.
- Block, Eric,Birringer, Marc,Deorazio, Russell,Fabian, Juergen,Glass, Richard S.,Guo, Chuangxing,He, Chunhong,Lorance, Edward,Qian, Quangsheng,Schroeder, T. Benjamin,Shan, Zhixing,Thiruvazhi, Mohan,Wilson, George S.,Zhang, Xing
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p. 5052 - 5064
(2007/10/03)
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- A Convenient Synthesis of 1,2-Dithietes and 1,2-Dithioxo Compounds Stabilized by Buttressing and Resonance Effects, Respectively, by Sulfuration of Alkynes with Elemental Sulfur
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Sulfuration of a series of alkynes by elemental sulfur was investigated.Alkynes carrying highly bulky substituents, 2,2,5,5-tetramethyl-3-hexyne (6a), 1,2-di-(1-adamantyl)ethyne (6b), 3,3-dimethyl-1-phenyl-1-butyne (6c), and 1-(1-adamantyl)-2-phenylethyne (6d), reacted with sulfur to give the corresponding stable 1,2-dithietes 7a-d in 46-65percent yields.Less hindered alkynes reacted with sulfur to afford 1,4-dithiins and thiophenes as the final products which were derived from the initial products, 1,2-dithietes, via their tautomerization to the corresponding 1,2-dithioxo compounds, while extremely congested alkynes failed to react with sulfur even under forcing conditions.On the other hand, ynamines, a typical electron-rich alkyne, 1-diethylamino-2-phenylthioethyne (6o), 1-diethylamino-2-phenylselenoethyne (6p), and tetraethylethynediamine (6q) were sulfurated under milder conditions to afford resonance-stabilized 1,2-dithioxo compounds 19o-q as the principal products.Mechanism of the formation of 1,2-dithietes, 1,2-dithioxo compounds, and other products is discussed.
- Choi, Keun Soo,Akiyama, Isao,Hoshino, Masamatsu,Nakayama, Juzo
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p. 623 - 629
(2007/10/02)
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- An Electron Spin Resonance Study of the Radical Cations of Pyrroles, Furans, and Thiophenes in Liquid Solution
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Photolysis of alkylpyrroles in trifluoroacetic acid containing mercury(II) trifluoroacetate, alkylfurans in trifluoroacetic acid, or alkylthiophenes in sulphuric acid, induces oxidation to the corresponding radical cations.The e.s.r. spectra show that the electronic configuration is similar in all three species, the unpaired electron occupying the φA MO in which the heteroatom lies in a nodal plane.Photolysis of 2,6-dimethyl- and 2,6-diethyl-thiophene in trifluoroacetic acid containing mercury(II) trifluoroacetate, on the other hand, gave rise to spectra with a high g value (2.0062), showing hyperfine coupling to two non-equivalent pairs of alkyl groups in an unsymmetrical dimer.
- Davies, Alwyn G.,Julia, Luis,Yazdi, Safieh N.
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p. 239 - 244
(2007/10/02)
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- TERTIARY BUTYLATION OF FIVE MEMBERED HETEROCYCLES. A UPS STUDY
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The reaction of 2-chloromercuryfuran and t-butylbromide was studied by UV photoelectron spectroscopy.During the reaction the formation of t-butylfuran, 2,5-di-t-butylfuran, t-butylchloride, isobutylene and furan were found.In accordance with the experimental observations a novel reaction mechanism has been proposed.The first fast and the second slow step of the reaction has been interpreted.The corresponding thiophene derivative gave similar results.
- Nyulaszi, L.,Gyuricza, A.,Veszpremi, T.
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p. 5955 - 5960
(2007/10/02)
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- STABLE HETEROARENIUM IONS - VIII SOME TRANSFORMATIONS OF ALKYLTHIOPHENIUM IONS AND NEW SYNTHESIS OF 2-t-BUTYLTHIOPHENE
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The ratio of isomeric ?-complexes formed from thiophene, t-butyl chloride and AlCl3 was found to be changed while keeping at room temperature whitin 1-2 days.This allows to obtain after deprotonation 2-t-butylthiophene containing only 3percent of 3-isomer.Transformations of ?-complexes formed by protonation of individual 2- and 3-t-butylthiophenes in the presence of AlCl3 have been studied and there was found that isomerization and deprotonation took place during their storage resulting in mixtures of 2- and 3-t-butylthiophenes (the ratio 97:3) which contained considerable quantities of 2,4-di-t-butylthiophene.Deprotonation of t-butylthiophenium ions in the presence of acetone leads to the formation of respective t-butylsubstituted dimethyldithienylmethanes.
- Belen'kii, L. I.,Yakubov, A. P.
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p. 2471 - 2477
(2007/10/02)
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- Silica Gel as an Effective Catalyst for the Alkylation of Phenols and Some Heterocyclic Compounds
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In the presence of silica gel, the reaction of phenol with t-BuBr was examined under a variety of conditions and it was found that silica gel is an effective catalyst for the alkylation.As a result of this work 2-tert-butyl-, 2,6-di-tert-butyl-, and 2,4,6-tri-tert-butylphenols, all of which are hard to obtain directly by the Friedel-Crafts process, could be prepared easily by this one-step reaction.Several other alkyl halides were also used in this reaction.The alkylations of some heterocyclic aromatic compounds which cannot be alkylated by the conventional Friedel-Crafts method were also succesfully performed by this reaction.
- Kamitori, Yasuhiro,Hojo, Masaru,Masuda, Ryoichi,Izumi, Tatsuo,Tsukamoto, Shuichi
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p. 4161 - 4165
(2007/10/02)
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