- A Bithiophene-Promoted ppm Levels of Palladium-Catalyzed Regioselective Hydrosilylation of Terminal Allenes
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A bithiophene?alkyne-based compound was synthesized and first utilized as a ligand for the selective hydrosilylation of allenes with primary and secondary phenylsilanes. It shows high selectivity towards the production of branched allylsilanes with a wide range of allenes. It is worth mentioning that the catalytic loading of the palladium can be reduced to 500 ppm. This work opens a new front of using bidentate thiophene ligand as a reaction promoter in transition-metal-catalyzed organic reaction. (Figure presented.).
- Chen, Jun-Jia,Zeng, Jia-Hao,Yang, Ying,Liu, Zhi-Kai,Jiang, Ya-Nan,Li, Miao-Ran,Chen, Li,Zhan, Zhuang-Ping
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p. 2360 - 2366
(2020/04/28)
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- E-H (E = R3Si or H) bond activation by B(C6F 5)3 and heteroarenes; Competitive dehydrosilylation, hydrosilylation and hydrogenation
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In the presence of B(C6F5)3 five-membered heteroarenes undergo dehydrosilylation and hydrosilylation with silanes. The former, favoured on addition of a weak base, produces H2 as a by-product making the process catalytic in B(C6F5) 3 but also enabling competitive heteroarene hydrogenation. the Partner Organisations 2014.
- Curless, Liam D.,Clark, Ewan R.,Dunsford, Jay J.,Ingleson, Michael J.
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supporting information
p. 5270 - 5272
(2014/05/06)
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- Catalytic transformations of alkylthiophenes
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The transformations of alkylthiophenes in the presence of amorphous aluminosilicate and decationated zeolite HNaY were studied. Substituted thiophenes with R = 2- and 3-Me, 2-Et, and 2-iso-Pr undergo dealkylation to thiophene with close rates, migration of the alkyl group from the 9α- to the β-position of the thiophene ring (or in the opposite direction with an elevated rate), and decomposition with H2S elimination. The dealkylation rate of 2-substituted thiophenes with a branched-chain radical (R = iso-Pr, terf-Bu) is much higher and the elimination rate with this radical is lower than those for normal-chain radicals; the isomerization step is virtually absent. Di-, tri-, and tetrasubstituted thiophenes with R = Et and iso-Pr undergo stepwise dealkylation, which is facilitated by an increase in the degree of substitution on the thiophene ring. Thiophene and its lower homologues can be obtained by the transformation of a mixture of high-molecular thiophenes. Copyright
- Mashkina,Chernov
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p. 209 - 215
(2007/10/03)
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- CANNABINOID RECEPTOR LIGANDS
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There are disclosed compounds of the formula I: or a pharmaceutically acceptable salt of the compound, which exhibit anti-inflammatory and immunomodulatory activity. Also disclosed are pharmaceutical compositions containing said compounds.
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Page/Page column 65
(2010/02/05)
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- SYNTHESIS AND CHARACTERIZATION OF ALKYL-, HALO- AND HETEROSUBSTITUTED DERIVATIVES OF THE POTENT PHOTOTOXIN &α-TERTHIENYL
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A number of derivatives of α-terthienyl were prepared including a series of naturally occurring compounds.A description of the syntheses of some new compounds, including 5-iodo, 5,5''-diiodo, 5,5''-diformyl, 5,5''-di-tert butyl, 5-tert-butyl, 5-tert-butoxy, 5-trimethylsilyl, 5-thiomethyl, 5,5''-dithiomethyl and 5-carboxyl-5''-(trimethylsilyl)-2,2':5',2''-terthienyl is also given.An analysis of the 1H NMR data of the derivatives is presented.
- Eachern, Anita Mac,Soucy, Chantal,Leitch, Leonard C.,Arnason, John T.,Morand, Peter
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p. 2403 - 2412
(2007/10/02)
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- Synthesis of some Thiophenium Bis(t-butoxycarbonyl)methylides
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Thiophene derivatives react with di-t-butyl diazomalonate in the presence of rhodium(II) carboxylates to yield thiophenium bis(t-butoxycarbonyl)methylides.Rhodium(II) hexanoate is a more efficient catalyst than rhodium(II) acetate, shortening reaction times and increasing yields of the ylides.Series of 2-halogeno-, 2-alkyl-, 2-benzyl-5-halogeno-, and 2-benzyl-5-alkyl-thiophenium ylides are described.Whilst 2-methyl-, 2-ethyl-, and 2-isopropyl-thiophenes readily form the ylides in good yield, 2-t-butylthiophene appears to undergo further reaction to yield 1,3-bis-t-butoxycarbonyl-2-(3-t-butyl-6,6-bis-t-butoxycarbonyl-2-thioniabicyclohex-3-en-2-yl)methanide (2) whose structure has been confirmed by X-ray crystallography.
- Bowles, Timothy,Jones, Ray,Porter, Alexander E. A.,Rechka, Josef A.,Rzepa, Henry S.,Williams, David J.
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p. 1023 - 1028
(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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- Gas-phase Heteroaromatic Substitution. Part 4. Electrophilic Attack of t-Butyl Cation on Pyrrole, N-Methylpyrrole, Furan, and Thiophene
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t-Butyl cation, obtained in the gas state from the γ-radiolysis of neopentane has been allowed to react with pyrrole (1), N-methylpyrrole (2), furan (3), and thiophene (4).Experiments have been carried out in the pressure range 50-760 Torr and in the presence of variable concentrations of a gaseous base (NMe3).The reactivity of simple heteroaromatic compounds relative to toluene in competition experiments is found to depend markedly upon the composition of the gaseous reaction environment.The apparent kS/kT ratios decrease slightly with increasing pressure.At atmospheric pressure, these ratios increase with the NMe3 concentration levelling off to a value of 1.0 (1), 2.2 (2), 2.6 (3), and 0.6 (4), at the highest base concentration (PNMe3=10 Torr).Under the same conditions, predominant β substitution occurs in the pyrroles , whereas α-attack is favoured in the case of furan (β:α=9:91) and thiophene (β:α=20:80).The gaseous elecrophile appears rather unselective between the n- and the ?-type centres of furan (O:ring=50:50) and thiophene (S:ring=40:60), while it displays no or very limited substitution on the heteroatom of pyrroles.A mechanism based upon reversible addition of the t-butyl cation to the heteroaromatic nucleus, involving premilinary formation of an electrostatic adduct, is used to account for the formation of the t-butylated products and their isomeric composition.It is concluded that the gas-phase t-butyl alkylation of simple five-membered heteroaromatic compounds is regulated by electrostatic interactions established within the encounter pair.A close correspondence exists between this rationalization of the present gas-phase results and recent theoretical and experimental evidence concerning related alkylation processes.
- Margonelli, Andrea,Speranza, Maurizio
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p. 1491 - 1498
(2007/10/02)
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