1942-46-7Relevant articles and documents
Preparation of diynes via selective bisalkynylation of zirconacycles
Liu,Xi,Hara,Nakajima,Yamazaki,Kotora,Takahashi
, p. 6951 - 6957 (2000)
Reaction of alkynyl halides with in situ prepared zirconacyclopentanes, -pentenes, and -pentadienes in the presence of CuCl under mild reaction conditions afforded alkynes or diynes. Control of the reaction conditions selectively afforded monoalkynylation products of zirconacycles. Reaction of zirconacycles with 2 equiv of alkynyl halides resulted in the formation of diynes. Selective monoalkynylation of zirconacycle with an alkynyl halide, followed by reaction with a different alkynyl halide, afforded unsymmetrical diynes. Bisalkynylation product of zirconacyclopentadiene was gradually converted into a tricyclic compound.
Allene formation by the reaction of olefins with propargyl silyl ethers mediated by a zirconocene complex
Takahashi, Tamotsu,Hara, Ryuichiro,Huo, Shouquan,Ura, Yasuyuki,Leese, Mathew P.,Suzuki, Noriyuki
, p. 8723 - 8726 (1997)
Ethylene and styrene derivatives reacted with various propargylic ethers in the presence of zirconocene(II) to afford allenic products in high yields. The reaction proceeded via formation of zirconacyclopentenes by selective coupling of an olefin and a propargylic ether, which was followed by β-elimination of the siloxy group. Deuterolysis confirmed that the final product had a zirconium-carbon bond.
Electrochemical Reduction and Intramolecular Cyclization of 1-Iodo-5-decyne and 1-Bromo-5-decyne at Vitreous Carbon Cathodes in Dimethylformamide
Shao, Rui-lian,Peters, Dennis G.
, p. 652 - 657 (1987)
In dimethylformamide containing tetramethylammonium perchlorate, cyclic voltammograms for reduction of 1-iodo-5-decyne and 1-bromo-5-decyne at a vitreous carbon electrode each consist of a single irreversible wave due to two-electron scission of the carbon-halogen bond.Preparative-scale electrolyses of 1-iodo-5-decyne yield pentylidenecyclopentane, 5-decyne, 1-decen-5-yne, and a small amount of 5-decyn-1-ol, whereas reduction of 1-bromo-5-decyne affords mainly 5-decyne and 1-decen-5-yne along with a modest quantity of pentylidenecyclopentane.Differences in product distributions correlate with the extent to which the 5-decyn-1-yl radical persists as a transient species.Pentylidenecyclopentane arises via intramolecular cyclization of the 5-decyn-1-yl radical followed by hydrogen atom abstraction, 5-decyne is formed via protonation of the 5-decyn-1-yl carbanion by either water or the tetramethylammonium cation, and 1-decen-5-yne and 5-decyn-1-ol are obtained, respectively, via E2 and SN2 reactions between unreduced starting material and hydroxide ion (generated by deprotonation of water).In the presence of a proton donor (diethyl malonate or hexafluoroisopropyl alcohol), the quantities of pentylidenecyclopentane and 5-decyne rise noticeably and the yield of 1-decen-5-yne falls dramatically.
Rhodium(iii)-catalyzed unreactive C(sp3)-H alkenylation of N-alkyl-1H-pyrazoles with alkynes
Li, Tongyu,Liu, Chang,Wu, Shaonan,Chen, Chen C.,Zhu, Bolin
supporting information, p. 7679 - 7683 (2019/08/30)
The first example of pyrazole-directed rhodium(iii)-catalyzed unreactive C(sp3)-H alkenylation with alkynes has been described, which showed a relatively broad substrate scope with good functional group compatibility. Moreover, we demonstrated that the transitive coordinating center pyrazole could be easily removed under mild conditions.
Rh(III)-Catalyzed [5 + 2] Oxidative Annulation of Cyclic Arylguanidines and Alkynes to 1,3-Benzodiazepines. A Striking Mechanistic Proposal from DFT
Martínez-Yá?ez, Nuria,Suárez, Jaime,Cajaraville, Ana,Varela, Jesús A.,Saá, Carlos
supporting information, p. 1779 - 1783 (2019/03/29)
A novel and mild Rh(III)-catalyzed [5 + 2] oxidative annulation between cyclic arylguanidines and alkynes efficiently affords 1,3-benzodiazepines (pentacyclic guanidines). The use of O2 as the sole oxidant in place of commonly used metal oxidants such as AgOAc clearly improves the efficiency of the oxidative annulation process. The mechanism of the cycloaddition most likely involves the formation of an eight-membered rhodacycle. DFT calculations support a striking mechanistic proposal for the [5 + 2] oxidative annulation.
Dehalogenation of vicinal dihalo compounds by 1,1′-bis(trimethylsilyl)-1: H,1′ H-4,4′-bipyridinylidene for giving alkenes and alkynes in a salt-free manner
Rej, Supriya,Pramanik, Suman,Tsurugi, Hayato,Mashima, Kazushi
supporting information, p. 13157 - 13160 (2017/12/26)
We report a transition metal-free dehalogenation of vicinal dihalo compounds by 1,1′-bis(trimethylsilyl)-1H,1′H-4,4′-bipyridinylidene (1) under mild conditions, in which trimethylsilyl halide and 4,4′-bipyridine were generated as byproducts. The synthetic protocol for this dehalogenation reaction was effective for a wide scope of dibromo compounds as substrates while keeping the various functional groups intact. Furthermore, the reduction of vicinal dichloro alkanes and vicinal dibromo alkenes also proceeded in a salt-free manner to afford the corresponding alkenes and alkynes.
Arylsulfonylacetylenes as alkynylating reagents
Marzo, Leyre,Aleman, Jose,Garcia Ruano, Jose Luis
, p. 403 - 407 (2013/07/26)
The unexpected anti-Michael addition of RLi to β-substituted sulfonylacetylenes, followed by in situ elimination of the ion sulfinate, allows the alkynylation of C(sp2) and C(sp3). Aryl and heteroaryl acetylenes, enynes, and mono and dialkyl alkynes can be obtained in very high yields under very mild conditions, avoiding the use of transition metals as catalysts and, in many cases, haloderivatives as starting materials. Furthermore, the use of lithium 2-p-tolylsulfinyl benzylcarbanions as nucleophiles of these reactions allows their stereocontrolled alkynylation, affording enantiomerically pure alkynes or enantioenriched allenes depending on the protonating agent (NH4Cl or H2O).
Expanding the scope of arylsulfonylacetylenes as alkynylating reagents and mechanistic insights in the formation of Csp2-Csp and Csp 3-Csp bonds from organolithiums
Garcia Ruano, Jose Luis,Aleman, Jose,Marzo, Leyre,Alvarado, Cuauhtemoc,Tortosa, Mariola,Diaz-Tendero, Sergio,Fraile, Alberto
supporting information; experimental part, p. 8414 - 8422 (2012/07/27)
We describe the unexpected behavior of the arylsulfonylacetylenes, which suffer an "anti-Michael" addition of organolithiums producing their alkynylation under very mild conditions. The broad scope, excellent yields, and simplicity of the experimental procedure are the main features of this methodology. A rational explanation of all these results can be achieved by theoretical calculations, which suggest that the association of the organolithiums to the electrophile is a previous step of their intramolecular attack and is responsible for the unexpected "anti-Michael" reactions observed for substituted sulfonylacetylenes. A calculated conclusion: A new transition-metal-free strategy for the synthesis of any kind of alkynyl derivatives in high yields in the reaction of organolithium species with arylsulfonylacetylenes is presented (see scheme). Theoretical calculations provide a rational explanation and suggest that association of the organolithium to the electrophile is a previous step of their intramolecular attack and is responsible for the "anti-Michael" reaction. Copyright
Effect of solvent and temperature on the lithium?bromine exchange of vinyl bromides: Reactions of n -butyllithium and t -butyllithium with (E)-5-bromo-5-decene
Bailey, William F.,Luderer, Mark R.,Uccello, Daniel P.,Bartelson, Ashley L.
experimental part, p. 2661 - 2666 (2010/08/19)
The outcome of reactions of (E)-5-bromo-5-decene (1), a representative vinyl bromide, with t-BuLi or n-BuLi at 0 °C and room temperature, respectively, in a variety of solvent systems has been investigated. Vinyl bromide 1 does not react with t-BuLi in pure heptane; however, the presence of even small quantities of an ether in a predominantly heptane medium resulted in virtually complete consumption of 1 at 0 °C, resulting in nearly the same distribution of products, including 60?80% of (Z)-5-decenyllithium, regardless of the solvent composition. Vinyl bromide 1 reacts slowly with n-BuLi at room temperature in a variety of ether and heptane-ether mixtures to afford a mixture of products including significant quantities of recovered starting material. The results of these experiments demonstrate that lithium?bromine exchange between a vinyl bromide and either t-BuLi or n-BuLi at temperatures significantly above ?78 °C is not an efficient method for the generation of a vinyllithium.
Selective terminal alkyne metathesis: Synthesis and use of a unique triple bonded dinuclear tungsten alkoxy complex containing a hemilabile ligand
Coutelier, Olivier,Nowogrocki, Guy,Paul, Jean-Francois,Mortreux, Andre
, p. 2259 - 2263 (2008/09/19)
The in situ synthesis of new alkyne metathesis catalysts is described, with particular emphasis on the search for tris-alkoxytungsten-based terminal alkyne metathesis. In that context, hemilabile, ether-containing alkoxy ligands have proved to be suitable and have led to the design and use of a sterically hindered hemilable ligand for the synthesis of a well-defined binuclear, triple-bonded W ≡ W complex. This complex is shown to be a highly active and selective catalyst precursor for terminal alkyne metathesis, and allows the unprecedented metathesis of phenylacetylene.
