- The dual role of thiourea in the thiotrifluoromethylation of alkenes
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Alkenes substituted with a thiourea undergo C-CF3 followed by intramolecular C-S bond formation with the Togni reagent and trifluoroacetic acid (TFA) at room temperature; thiols and thioamides are not suitable S-sources for this reaction. This anti-addition process involves a CF3 radical, and affords CF3-substituted thiazolines and thiazines for medicinal applications. A metal or photoredox catalyst is not required as the thiourea acts as a reductant, as well as serving as an S-source capable of adding to a C-centered radical. Mechanistic work comparing the reactivity of thiourea, urea, thioamide and thiol in the context of alkene trifluoromethylation demonstrates that in this series, the thiourea is unique for its ability to release CF3 radical from the Togni reagent, and to orchestrate trifluoromethylation followed by S-cyclization with both activated and unactivated alkenes.
- Ricci, Paolo,Khotavivattana, Tanatorn,Pfeifer, Lukas,Médebielle, Maurice,Morphy, John Richard,Gouverneur, Véronique
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p. 1195 - 1199
(2017/02/10)
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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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- Reduction of thiophenes in the presence of sulfuric acid and zinc
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Alkyl-substituted thiophenes are hydrogenated by the Zn-H 2SO4 system to the corresponding 2,5-di- hydrothiophenes and thiophanes. In the case of 2-formyl- and 2-acetylthiophene it was established that in substituted thiophenes simul
- Latypova,Parfenova,Lyapina
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experimental part
p. 1078 - 1084
(2012/03/27)
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- Hydrogen storage using heterocyclic compounds: The hydrogenation of 2-methylthiophene
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Alkyl substituted thiophenes are promising candidates for hydrogen carriers, as their dehydrogenation reactions are known to occur under mild conditions. Four types of catalysts, including supported noble metals, bimetallic noble metals, transition metal
- Zhao,Oyama,Naeemi
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scheme or table
p. 172 - 184
(2010/11/05)
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- PROTIC-ELECTRONIC REDUCTION OF THIOPHENES
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Thiophene and 2-alkylthiophenes are hydrogenated to the respective substituted 2,5-dihydrothiophenes by the zinc-trifluoroacetic acid system.Small quantities of substituted tetrahydrothiophenes are also formed.In 2-formyl- and 2-acetylthiophene simultaneo
- Lyakhovetskii, Yu. I.,Latypova, F. M.,Lyapina, N. K.,Parnes, Z. N.
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p. 1001 - 1010
(2007/10/02)
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- Organosulfur Chemistry. II. Use of Dimethyl Sulfoxide; a Facile Synthesis of Cyclic Sulfides
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A versatile and short-reaction-time synthesis of twelve four-, five- and six-membered thiacycloalkanes (IIa-l)from the appropriate α,ω-dibromoalkanes (Ia-l)has been developed.Technical-grade dimethyl sulfoxide was proved to be by far the best for this cyclization.The pronounced effect for ring formation was recognized to be in order of five-membered ring (thiolanes) > six-membered ring (thianes) > four-membered ring (thietanes).Startling were 2-methylthiolane (IIf) and 2,5-dimethylthiolane (IIg; cis/trans mixture), both obtained in high yields although α-methyl - and α,α'-dimethyl substitution in general showing a remarkable retardation for cyclization.On the other hand, in both 3,3-dimethylthietane (IId) and 4,4-dimethylthiane (IIl) cyclization was much more efficient than other counterparts in each series, which is referred to as the gem-dimethyl effect.Keywords: thiacycloalkane; thietane; thiolane; thiane; dimethyl sulfoxide; cyclization: α,ω-dibromoalkane; sodium sulfide nonahydrate; refractive index
- Nagasawa, Kazuo,Yoneta, Akemi
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p. 5048 - 5052
(2007/10/02)
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- FAST AND SLOW STEPS OF HYDRODESULFURIZATION
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Two model mixtures (2-methylthiophene, phenol, o-toluidine, ethylbenzene and benzothiophene, o-cresol, aniline, o-xylene) were used to characterize activity and selectivity of different sulfur resistent catalysts for simultaneous HDS, HDO, HDN and hydrogenation of aromatics. 2-methyltetrahydrothiophene and dihydrobenzothiophene were found as intermediates.A mechanism for the HDS-reaction is discussed and compared to the HDN mechanism of quinoline.
- Schulz, Hans,Do, Dac-Vong
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p. 645 - 652
(2007/10/02)
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- FORMATION OF SULPHUR COMPOUNDS IN HYDRODENITROGENATION OF QUINOLINE, 1,2,3,4-TETRAHYDROQUINOLINE, PYRIDINE, PIPERIDINE AND 1-PENT-4-ENYLAMINE ON A NICKEL-TUNGSTEN CATALYST IN THE PRESENCE OF HYDROGEN SULPHIDE
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Hydrodenitrogenation (HDN) of quinoline and 1,2,3,4-tetrahydroquinoline on a sulphided nickel-tungsten catalyst in the presence of hydrogen and of its mixture with hydrogen sulphide has been studied in an autoclave at 350 deg C.The results show that hydrogen sulphide exhibits rate-accelerating effect on HDN of the above compounds by formation of sulphur compounds.It was found that neutral portion of the reaction mixture contains octahydro-2H-1-benzothiopyran, octahydro-1H-2-benzothiopyran, octahydro-2-methylbenzo(b)thiophene and other sulphur compounds.The reaction scheme for HDN of quinoline that accounts for favourable effect of hydrogen sulphide is proposed.In the neutral portion of the reaction mixture from HDN of piperidine and 1-pent-4-enylamine in the presence of hydrogen sulphide further sulphur-containing compounds were identified.
- Cerny, Mirko,Trka, Antonin
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p. 1749 - 1758
(2007/10/02)
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- Heterocyclisation alkylante radicalaire par photolyse de sulfures ethyleniques. III. Photolyse de sulfures de butene-3 yle-1 et hexene-5 yle-1
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Photolysis of allyl but-3-en-1-yl sulfide (I) gives the thiolan 3 and the 3-allylthiolan 4 resulting from "forbidden" 5-endotrig cyclization.Photolysis of allyl hex-5-en-1-yl sulfide (III) gives, besides the mixture of six- and seven-membered non-alkylated heterocycles 10 and 11, exclusively the alkylated 2-(but-3-enyl) thian 12.These and other results confirm and generalize the mechanism proposed earlier for the photolytic cyclization of pent-4-enyl sulfides.Photolitic cleavage of unsaturated allyl or benzyl sulfides gives the unsaturated thiyl radical.The unsaturated radical undergoes an intramolecular reversible addition out of the cage.Then the more stable cyclized radical is trapped selectively by the allyl or benzyl radical.
- Bastien, Gerard,Surzur, Jean-Marie
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- FORMATION OF SULFUR COMPOUNDS IN THE HYDRODENITROGENATION OF PIPERIDINE, PYRIDINE, 1-PENTYLAMINE AND 1-PENT-4-ENYLAMINE ON A NICKEL-TUNGSTEN CATALYST IN THE PRESENCE OF HYDROGEN SULFIDE
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Hydrogenations of piperidine, pyridine, 1-pentylamine, and 1-pent-4-enylamine were carried out in an autoclave at 300 deg C on a sulfidized nickel-tungsten catalyst using either pure hydrogen or a mixture of hydrogen with hydrogen sulfide.Hydrogen sulfide was found to raise the degree of conversion of the starting substances and accelerate the hydrodenitrogenation by formation of sulfur compounds; 1-pentanethiol, di(1-pentyl)sulfide, 2-methylthiacyclopentane, thiacyclohexane and other sulfur compounds were detected in the reaction mixtures in the presence of hydrogensulfide.A reaction pathway is suggested of the hydrodenitrogenation of piperidine in the presence of hydrogen sulfide, accounting for the favourable effect of the latter on the hydrodenitrogenation of nitrogen compounds.
- Cerny, Mirko
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p. 928 - 935
(2007/10/02)
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