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1.
Intermolecular hydroamination of alkynes catalyzed by Ti(NMe2)4 was much improved with N-heterocyclic carbenes and LiN(SiMe3)2, by which high Markovnikov selectivity was attained for the coupling of nearly all alkynes and amines.  相似文献   

2.
Conditions for a FeCl3/PPh3-catalyzed and palladium-, copper-, amine free-Sonogashira coupling reaction of aryl halides with terminal alkynes are reported. The protocol was applicable to a wide variety of substituted aryl iodides and alkynes with different steric and electronic properties and gave excellent yields of the desired coupling products.  相似文献   

3.
The chemistry of Cp2V2(CO)5 (I) with alkynes is reported. In non-coordinating solvents, I reacts with large, electron-poor alkynes to give the cyclobutadiene complexes CpV(CO)2(C4R4), which are not formed from photolysis of CpV(CO)4 in the presence of alkyne. Smaller, more basic alkynes give simple monomeric adduct products of the type CpV(CO)2(RCCR). This latter product is the only one obtained if coordinating solvents are employed. It is demonstrated that coupling to form the cyclobutadiene ligand occurs on the dimer. The dimeric intermediate, produced at low temperature and observed at low temperature by IR and NMR, is believed to have the formula Cp2V2(CO)4(μ-RCCR) (X).Cp2V2(CO)5 is active as a catalyst precursor in the photochemical hydrogenation of diphenyl acetylene to cis-stilbene. The mechanism appears to proceed through a Cp2V2(CO)4(alkyne) intermediate.  相似文献   

4.
An unprecedented route to prepare terminal alkynes from 1,1-dibromo-1-alkenes mediated by Cs2CO3 was proven. 1,1-Dibromo-1-alkenes bearing various functional groups were efficiently converted to corresponding terminal alkynes in moderate to excellent yields.  相似文献   

5.
The reaction of mono- and disubstituted alkynes with CH2I2-R3Al (R = Me, Et, i-Bu) was studied. It was found that the reaction of alkynes with CH2I2 in the presence of Me3Al gives β-iodoethyl-substituted cyclopropanes. The use of Et3Al or i-Bu3Al affords exclusively cyclopropylic organoaluminum compounds.  相似文献   

6.
This review describes the preparation, characterization and application of KNH2 loaded on alumina and KF loaded on alumina. These strong solid bases catalyze a variety of organic reactions in a very selective manner. The reactions include isomerizations of alkenes and alkynes, dimerization of alkynes, Tishchenko reaction, and the reaction of silanes to form of Si–C, Si–N and Si–O bonds.  相似文献   

7.
Kenta Yoshida  Hideo Tanaka 《Tetrahedron》2008,64(24):5800-5807
The RhCl3·3H2O/i-Pr2NEt-catalyzed [2+2+2] cyclotrimerization of alkynes has been achieved. The reaction can be widely used for various alkynes and provides tri- or hexa-substituted benzenes regioselectively in high yields. The [2+2+2] cycloaddition of diynes and alkynes is also developed, and it affords benzene derivatives in moderate to high yields.  相似文献   

8.
In contrast to the observation made by the Laguna group, we report that the combination of PdCl2(PPh3)2 and AuCl(PPh3) makes a unique catalytic system that allows Sonogashira-type cross-coupling of both aryl and alkyl alkynes with aryl halides in excellent yields.  相似文献   

9.
A thermally promoted and CuSO4-catalyzed new version of the Huisgen-click reaction is presented in this Letter. Notably, this protocol was suitable not only for the reactions between organic azides and alkynes, but also for one-pot three-component reactions among alkyl halides, NaN3, and alkynes.  相似文献   

10.
The silica-supported aqueous-phase catalyst (SAPC) approach has proven convenient for efficiently performing the hydration of alkynes with HgSO4/H2SO4 to give the corresponding carbonyl compounds in dichloromethane under mild conditions. The use of this solid reagent significantly improves the reaction work-up as it merely involves filtering and evaporating the solvent.  相似文献   

11.
The regioselective reaction of 2,2′-dihydroxybiphenyl with terminal alkynes was found to be rapidly catalyzed by InCl3 and ZrCl4. The chemoselectivity of catalysts and alkynes for biphenol over water, together with the reaction mechanism are discussed in details.  相似文献   

12.
Ya Li 《Tetrahedron》2009,65(2):478-483
Stereoselective free radical (phenylsulfonyl)difluoromethylation of terminal alkynes with iododifluoromethyl phenyl sulfone (PhSO2CF2I) has been accomplished by using Et3B/air as an initiator. The obtained PhSO2CF2-substituted vinyl iodides, which can be further subjected to Suzuki coupling and Sonogashira coupling reactions, are useful precursors for the preparation of many structurally diverse PhSO2CF2- and CF2H-substituted alkenes.  相似文献   

13.
It is shown that alkynes, such as CF3C≡CCF3 and CH3OOCC≡CCOOCH3, which contain strongly electron-attracting groups, undergo insertion into the metal-metal bond of [FeX(CO)3]2 complexes (X = SCH3, SC6H5, P(CH3)2) under UV irradiation. The reactions of the products with trimethylphosphine are also described.  相似文献   

14.
A highly regioselective cyclotrimerization of olefins with electron-withdrawing groups in a PdCl2/O2/DMF catalytic system is disclosed, and a possible mechanism has also been proposed, which reveals the PdCl2-catalyzed cyclotrimerization of olefins with electron-withdrawing groups goes through a quite different pathway from that of alkynes.  相似文献   

15.
The complex [Ir(σ-carb)(CO)(PhCN)(PPh3)], where carb = -7-C6H5-1,2C2B10H10, was found to be an effective catalyst for homogeneous hydrogenation of terminal olefins and acetylenes at room temperature and atmospheric or subatmospheric hydrogen pressure. Internal olefins are not hydrogenated, but simple alk-1-enes are readily converted into the corresponding alkanes. Isomerization of the double bond catalyzed by the metal complex occurs at very small extent. Catalytic hydrogenation of olefins having carboxylate substituents on the unsaturated carbon atoms is prevented by the formation of thermally stable chelate hydridoalkyl complexes of the type I(H)(σ-CHRCHR′C(O)OR″) (σ-carb)(CO)(PPh3)]. Acetylenes are hydrogenated to alkenes. The alk-1-enes formed in the hydrogenation of the alkynes HCCR in turn undergo the more slow reactions either of hydrogenation to alkanes or isomerization to internal olefins which cannot be further hydrogenated. Hydrogenation of alkynes of the type RCCR′ is stereospecifically cis, yielding cis- olefins. Catalyzed cistrans isomerization reaction of these internal olefins occurs only to a negligeable extent.  相似文献   

16.
Rh2(S-PTAD)4 is an effective catalyst for the asymmetric cyclopropenation of aryl alkynes using a siloxyvinyldiazoacetate as the carbenoid precursor. Upon deprotection of the silyl protecting group, highly enantioenriched cyclopropenes bearing geminal acceptor groups can be accessed. These cyclopropenes undergo regioselective rhodium(II)-catalyzed ring expansion to furans.  相似文献   

17.
The mechanism of the addition reaction of TeCl4 to alkynes was indirectly established by the detection of TeCl3 centered radicals using EPR spin trapping, ESI-MS and ESI-MS/MS characterization.  相似文献   

18.
ReBr(CO)5-catalyzed addition of Et2NH and CO2 to terminal alkynes afforded anti-Markovnikov adducts of alkenyl carbamates in good to excellent yield and high regioselectivity.  相似文献   

19.
The complex (η5-C5H5)NiRu3(μ-H)(CO)942-CCHBut) (1a) reacts with olefins to give several organic products, including species derived from the coupling of the vinylidene ligand with an olefin-derived =CRR′ fragment, representing the first example of a (non catalytic) olefin metathesis reaction involving a metal cluster; other complexes structurally or chemically related to the compound 1a have also been treated with olefins and alkynes.  相似文献   

20.
This review reports the contribution of the catalyst precursor RuCl(COD)C5Me5, and of the Rennes team, for the selective transformation of alkynes to generate high value chemicals with atom economy reactions. Ruthenium activation processes are discussed. Are successively presented (i) the cross-oxidative coupling of alkyne and allyl alcohol to generate γ,δ-unsaturated aldehydes, (ii) the head-to-head dimerisation of alkynes in the presence of carboxylic acids, via a mixed Fischer-Schrock type biscarbene-ruthenium complex, to give functional dienes, and that of propargyl alcohols, via cyclobutadienyl-ruthenium intermediate, to produce cyclobutene derivatives, (iii) the addition of diazoalkanes to alkynes leading to functional dienes via double carbene addition and (iv) the reaction of diazoalkanes to enynes leading to new bicyclo[3.1.0]hexane compounds. Most of the above catalytic reactions involve carbene-ruthenium catalytic species of type Cp*(Cl)Ru(biscarbene) or Cp*(Cl)RuCHR.  相似文献   

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