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1.
Burling S Paine BM Nama D Brown VS Mahon MF Prior TJ Pregosin PS Whittlesey MK Williams JM 《Journal of the American Chemical Society》2007,129(7):1987-1995
A series of ruthenium hydride N-alkyl heterocyclic carbene complexes has been investigated as catalysts for a tandem oxidation/Wittig/reduction reaction to give C-C bonds from alcohols. The C-H-activated carbene complex Ru(IiPr(2)Me(2))'(PPh(3))(2)(CO)H (9) proves to be the most active precursor catalyzing the reaction of PhCH(2)OH and Ph(3)P=CHCN in 3 h at 70 degrees C. These results provide (a) a rare case in which N-alkyl carbenes afford higher catalytic activity than their N-aryl counterparts and (b) a novel example of the importance of NHC C-H activation in a catalytic cycle. 相似文献
2.
Tandem catalysis can offer unique and powerful strategies for converting simple starting materials into more complex products in a single reaction vessel while generating less waste and minimizing handling. In this regard, Grubbs' ruthenium alkylidene (Cy3P)2Cl2Ru=CHPh is shown to catalyze two mechanistically distinct transformations to offer a unique protocol that effects multiple bond changes in a single operation. A tandem ruthenium-catalyzed olefin ring-closing metathesis (RCM)/Kharasch addition allows for the facile preparation of bicyclic [3.3.0], [4.3.0], and [5.3.0] ring systems in one step from the appropriately functionalized acyclic precursors. For substrates where the intramolecular Kharasch addition fails, an intermolecular Kharasch addition is possible. By combining the intra- and intermolecular Kharasch additions with RCM, three new contiguous carbon-carbon bonds with multiple stereocenters can be generated by the ruthenium catalyst in a controlled fashion in one operation through two mechanistically distinct pathways. 相似文献
3.
The natural chalcone bavachromanol has been prepared through a tandem reaction sequence that joins cationic cyclization of an epoxide to an adjacent MOM-acetal with electrophilic aromatic substitution by a presumed methoxymethylene cation. Only a single regioisomer of the tandem product was observed, with substitution taking place exclusively ortho to the position of the original acetal. This regiocontrol provided a key intermediate from a symmetrical precursor, and allowed preparation of the meroterpenoid through a short reaction sequence. 相似文献
4.
Processes that form multiple carbon-carbon bonds in one operation can generate molecular complexity quickly and therefore be used to shorten syntheses of desirable molecules. We selected the hetero-Pauson-Khand (HPK) cycloaddition and ring-closing metathesis (RCM) as two unique carbon-carbon bond-forming reactions that could be united in a tandem ruthenium-catalyzed process. In doing so, complex polycyclic products can be obtained in one reaction vessel from acyclic precursors using a single ruthenium additive that can catalyze sequentially two mechanistically distinct transformations. 相似文献
5.
An application of the Horner-Wadsworth-Emmons reaction carried out on a ruthenium compound as the electrophilic precursor is described for the synthesis of fused donor-acceptor system 1 based on an extended tetrathiafulvalene and a ruthenium complex of dipyridoquinoxaline units. 相似文献
6.
7.
Acyclic enynes undergo a tandem enyne metathesis/cyclopropanation sequence in the presence of Grubbs' 1st generation metathesis catalyst and diazo compounds. In practice, the acyclic substrates in the presence of the ruthenium alkylidene first undergo a ring-closing enyne metathesis to generate cyclic 1,3-dienes; then upon addition of a diazo compound, these products are cyclopropanated selectively at the more accessible olefin. Overall, the reaction sequence converts acyclic enynes into vinyl cyclopropanes in single operation through two unique ruthenium-catalyzed transformations. 相似文献
8.
[reaction: see text] A one-pot tandem cross-metathesis/hydrogenation/cyclization procedure was achieved at room temperature, under 1 atm of hydrogen, in the presence of a ruthenium catalyst and PtO(2) showing the compatibility of the two catalysts. This tandem reaction allows the synthesis of substituted lactones and lactols from acrylic acid and acrolein, respectively, in the presence of unsaturated alcohols. 相似文献
9.
《Tetrahedron letters》1998,39(38):6815-6818
We show here the first example of a ruthenium catalyzed ene-yne metathesis reaction in tandem with a Diels-Alder cycloaddition reaction to efficiently form highly substituted hexahydroisoindole ring systems on Wang resin. This approach was used to prepare a 4200 membered combinatorial library. 相似文献
10.
Wen P Itoh H Tang W Feng Q 《Langmuir : the ACS journal of surfaces and colloids》2007,23(23):11782-11790
Anatase-type TiO2 single nanocrystals with boatlike, comblike, sheetlike, leaflike, quadrate, rhombic, and wirelike particle morphologies were prepared by hydrothermal treatment of a layered titanate nanosheet colloidal solution. The formation reactions and surface properties of the TiO2 nanocrystals were investigated using XRD, TEM, TG-DTA analyses, and measurements of BET specific surface area, photocatalytic activity, and ruthenium dye (N719) adsorption. The crystal morphology can be controlled by reaction temperature, pH value of reaction solution, and exfoliating agent. The titanate nanosheets were transformed to the TiO2 nanocrystals by two types of reactions. One is an in situ topotactic structural transformation reaction, and the other is a dissolution-deposition reaction on the surface. The anatase nanocrystals formed by the in situ topotactic structural transformation reaction retain the sheetlike particle morphology of the precursor, and they preferentially expose the (010) plane of anatase structure. The crystal surface of anatase nanocrystals prepared in this study showed higher photocatalytic activity and higher ruthenium dye adsorption capacity than did the Ishihara ST-01 sample, a standard anatase nanocrystal sample. The results indicated the (010) plane of the anatase structure has high photocatalytic activity and high ruthenium dye adsorption ability. 相似文献
11.
[reaction: see text]. A ruthenium complex, Cp*Ru(bipyridyl)Cl, has been developed as a catalyst for the first regioselective tandem Michael addition-allylic alkylation of activated Michael acceptors. The net transformation is the decarboxylative insertion of Michael acceptors into allyl beta-ketoesters. 相似文献
12.
Bouziane A Hélou M Carboni B Carreaux F Demerseman B Bruneau C Renaud JL 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(18):5630-5637
Secondary allylic alcohols were synthesized from linear allylic halides or carbonates using a catalytic amount of a ruthenium complex in the presence of boronic acid. The effects of solvent, base, ruthenium precursor, and boronic acid were fully explored, and the scope of the reaction was extended to various substrates. We also describe a preliminary investigation towards an enantioselective process. 相似文献
13.
Grubbs' 2nd generation and Hoveyda-Grubbs' ruthenium alkylidenes are shown to be effective catalysts for cross-metatheses of allylic alcohols with cyclic and acyclic olefins, as well as isomerization of the resulting allylic alcohols to alkyl ketones. The net result of this new tandem methodology is a single-flask process that provides highly functionalized, ketone-containing products from simple allylic alcohol precursors. [reaction: see text] 相似文献
14.
Ruthenium-catalyzed Heck olefination and Suzuki cross coupling reactions have been developed. When starting with a ruthenium complex [RuCl(2)(p-cymene)](2) as a homogeneous catalyst precursor, induction periods were observed and ruthenium colloids of zero oxidation state were generated under catalytic conditions. Isolated ruthenium colloids carried out the olefination, implying that active catalytic species are ruthenium nanoclusters. To support this hypothesis, ruthenium nanoparticles stabilized with dodecylamine were independently prepared via a hydride reduction procedure, and their catalytic activity was subsequently examined. Olefination of iodobenzene with ethyl acrylate was efficiently catalyzed by the ruthenium nanoparticles under the same conditions, which could be also reused for the next runs. In poisoning experiments, the conversion of the olefination was completely inhibited in the presence of mercury, thus supporting our assumption on the nature of catalytic species. No residual ruthenium was detected from the filtrate at the end of the reaction. On the basis of the postulation, a heterogeneous catalyst system of ruthenium supported on alumina was consequently developed for the Heck olefination and Suzuki cross coupling reactions for the first time. It turned out that substrate scope and selectivity were significantly improved with the external ligand-free catalyst even under milder reaction conditions when compared to results with the homogeneous precatalyst. It was also observed that the immobilized ruthenium catalyst was recovered and reused up to several runs with consistent efficiency. Especially in the Suzuki couplings, the reactions could be efficiently carried out with as low as 1 mol % of the supported catalyst over a wide range of substrates and were scaled up to a few grams without any practical problems, giving coupled products with high purity by a simple workup procedure. 相似文献
15.
Clark DA Kulkarni AA Kalbarczyk K Schertzer B Diver ST 《Journal of the American Chemical Society》2006,128(49):15632-15636
To extend the versatility of the ruthenium carbene-promoted enyne metathesis, it was combined with an Ireland ester enolate Claisen rearrangement. This reaction sequence provided conjugated dienes of higher substitution pattern than that obtained through a cross-enyne metathesis alone. The Ireland-Claisen was conducted across both acyclic and cyclic dienes produced from cross-metathesis and methylene-free enyne metathesis, respectively. In the case of cyclodienes, the Ireland-Claisen rearrangement produced s-trans locked dienes which underwent mode-selective ene reaction. The tandem, sequential use of the Ireland-Claisen rearrangement also proved suitable for chirality transfer originating from chiral propargylic alcohols. Last, the tandem metathesis/Ireland-Claisen was utilized to access 4-substituted-3,5-cyclohexadiene diol derivatives, which are valuable chiral intermediates for natural product synthesis. The combination of this pericyclic reaction with a catalytic metathesis reaction extends the versatility of cross-metathesis since additional diene motifs can be accessed. 相似文献
16.
Development of an Enyne Metathesis/Isomerization/Diels–Alder One‐Pot Reaction for the Synthesis of a Novel Near‐Infrared (NIR) Dye Core 下载免费PDF全文
Kohei Yamashita Yuki Fujii Shohei Yoshioka Dr. Hiroshi Aoyama Dr. Hirofumi Tsujino Prof. Dr. Tadayuki Uno Prof. Dr. Hiromichi Fujioka Dr. Mitsuhiro Arisawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(48):17491-17494
N‐Alkyl‐N‐allyl‐2‐alkynylaniline derivatives undergo a tandem ring‐closing enyne metathesis/isomerization/Diels–Alder cycloaddition sequence in the presence of a second‐generation Grubbs catalyst and dienophiles. In practice, the acyclic enyne in the presence of the ruthenium alkylidene first undergoes ring‐closing metathesis to generate cyclic 4‐vinyl‐1,2‐dihydroquinolines; following diene isomerization and then the addition of a dienophile, these ring‐closing metathesis products are selectively converted into a 7‐methyl‐4H‐naphtho[3,2,1‐de]quinoline‐8,11‐dione core. Overall, the reaction sequence converts simple aniline derivatives into π‐conjugated small molecules, which have characteristic absorption in the near‐infrared region, in a single operation through three unique ruthenium‐catalyzed transformations. 相似文献
17.
Yinghuai Z Widjaja E Sia SL Zhan W Carpenter K Maguire JA Hosmane NS Hawthorne MF 《Journal of the American Chemical Society》2007,129(20):6507-6512
Well dispersed ruthenium(0) nanoparticles, stabilized in the ionic liquid agent, trihexyltetradecylphosphonium dodecylbenzenesulfonate, have been successfully prepared via a reduction reaction of the precursor [CpRuCp*RuCp*]PF6 (Cp* = C5Me5). The ruthenium(0) nanoparticles were shown to catalyze the isotope exchange reaction between 10B enriched diborane and natural abundant B10H14 to produce highly 10B enriched (approximately 90%) decaborane(14) products. The ruthenium(0) nanoparticles were characterized by TEM, XRD, and XPS. The 10B enriched decaborane(14) has been analyzed by Raman spectroscopy, NMR, and high-resolution MS. 相似文献
18.
This study presents a new reaction of cationic vinylidene complexes with Me?SiN? (TMSN?), which yields N-coordinated nitrile complexes 3. Treatment of a ruthenium acetylide precursor containing indenyl and dppe ligands with a series of organic halides produced the corresponding vinylidene complexes 2 in good yield. Further reaction of 2 with TMSN? at room temperature produced N-coordinated ruthenium nitrile complexes 3. Unlike the reaction of cyclopropenylruthenium complexes with TMSN?, which yielded different products depending on the substituent at Cγ, the vinylidene complexes containing unsaturated bonds at Cd yielded similar N-coordinated nitrile complexes. This transformation did not seemingly occur in the reaction of ruthenium vinylidene complexes containing Cp and PPh? ligands with TMSN?. Deprotonation of these vinylidene complexes yielded cyclopropenyl or thermodynamic furylruthenium complexes, depending on the substitute at Cγ. Subsequent reactions of the cyclopropenyl or furylruthenium complexes with TMSN? afforded different products. 相似文献
19.
Ryan P. Murelli 《Tetrahedron letters》2008,49(40):5714-5717
Substituted vinylcyclopropanes are prepared through a ruthenium-catalyzed, tandem three-component coupling between an olefin, alkyne, and diazoester. Grubbs’ 2nd generation (NHC) ruthenium complexes in the presence of ethylene effect a stereoselective enyne-cross metathesis between alkynes and olefins to generate 1,3-substituted dienes. The slow introduction of diazoacetates to this reaction mixture then allows for the regioselective cyclopropanation of the resulting diene. When the olefin reaction partner is just ethylene (i.e., R′ = H), the tandem process is less efficient. In this case, the byproducts provide unique insight into possible catalyst decomposition pathways. 相似文献
20.
Carella A Launay JP Poteau R Rapenne G 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(27):8147-8156
The preparation of ruthenium(II) complexes coordinated to a penta(4-halogeno)phenylcyclopentadienyl ligand and to the hydrotris(indazolyl)borate ligand are detailed. Our strategy involves first the coordination of the penta(4-bromo)phenylcyclopentadienyl ligand by reaction with the ruthenium-carbonyl cluster followed by the coordination of the tripodal ligand. The pentabrominated precursor was successfully converted to the pentaiodinated derivative by using the Klapars-Buchwald methodology, applied for the first time on organometallic substrates. Cross-coupling reactions were performed on both pentabromo and pentaiodo complexes to introduce in a single step the five peripheric ferrocenyl fragments required to obtain a potential molecular motor. The two ligands present in the ruthenium complexes undergo a correlated rotation that was established both experimentally by NMR experiments and an X-ray diffraction study, and theoretically by DFT calculations. The potential-energy curve obtained by DFT revealed the energy barrier of the gearing mechanism to be only 4.5 kcal mol(-1). These sterically highly constrained complexes can be regarded as organometallic molecular turnstiles. 相似文献