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ABSTRACT: An efficient and regioselective ruthenium-catalyzed oxidative annulation of enamides with alkynes via the cleavage of C(sp(2))-H/N-H bonds is reported. The reactions can afford N-acetyl substituted or N-unsubstituted pyrroles by altering the reaction conditions slightly.
Organic Letters 12/2012; · 5.86 Impact Factor
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ABSTRACT: The mechanism of the [(Cp*MCl(2) )(2) ] (M=Rh, Ir)-catalyzed oxidative annulation reaction of isoquinolones with alkynes was investigated in detail. In the first acetate-assisted CH-activation process (cyclometalated step) and the subsequent mono-alkyne insertion into the MC bonds of the cyclometalated compounds, both Rh and Ir complexes participated well. However, the desired final products, dibenzo[a,g]quinolizin-8-one derivatives, were only formed in high yield when the Rh species participated in the final oxidative coupling of the CN bond. Moreover, a Rh(I) sandwich intermediate was isolated during this transformation. The iridium complexes were found to be inactive in the oxidative coupling processes. All of the relevant intermediates were fully characterized and determined by single-crystal X-ray diffraction analysis. Based on this mechanistic study, a Rh(III) →Rh(I) →Rh(III) catalytic cycle was proposed for this reaction.
Chemistry 11/2012; · 5.93 Impact Factor
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ABSTRACT: The cascade oxidative annulation reactions of benzoylacetonitrile with internal alkynes proceed efficiently in the presence of a rhodium catalyst and a copper oxidant to give substituted naphtho[1,8-bc]pyrans by sequential cleavage of C(sp(2))-H/C(sp(3))-H and C(sp(2))-H/O-H bonds. These cascade reactions are highly regioselective with unsymmetrical alkynes. Experiments reveal that the first-step reaction proceeds by sequential cleavage of C(sp(2))-H/C(sp(3))-H bonds and annulation with alkynes, leading to 1-naphthols as the intermediate products. Subsequently, 1-naphthols react with alkynes by cleavage of C(sp(2))-H/O-H bonds, affording the 1:2 coupling products. Moreover, some of the naphtho[1,8-bc]pyran products exhibit intense fluorescence in the solid state.
Journal of the American Chemical Society 09/2012; 134(39):16163-6. · 9.91 Impact Factor
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ABSTRACT: The mechanism of [{RuCl(2) (p-cymene)}(2) ]-catalyzed oxidative annulations of isoquinolones with alkynes was investigated in detail. The first step is an acetate-assisted CH bond activation process to form cyclometalated compounds. Subsequent mono-alkyne insertion of the RuC bonds of the cyclometalated compounds then takes place. Finally, oxidative coupling of the CN bond of the insertion compounds occurs to afford Ru(0) sandwich complexes that undergo oxidation to regenerate the catalytically active Ru(II) complex with the copper oxidant and release the desired dibenzo[a,g]quinolizin-8-one derivatives. All of the relevant intermediates were fully characterized and determined by single crystal X-ray diffraction analysis. The [{RuCl(2) (p-cymene)}(2) ]-catalyzed CH bond functionalization of isoquinolones with alkynes to synthesize dibenzo[a,g]quinolizin-8-one derivatives through CH/NH activation was also demonstrated.
Chemistry 08/2012; 18(40):12873-9. · 5.93 Impact Factor
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ABSTRACT: Ruthenium-catalyzed oxidative C-H bond olefination of N-methoxybenzamides using an oxidizing directing group with a broad substrate scope is reported. The reactions of N-methoxybenzamides with acrylates in MeOH and styrene (or norbornadiene) in CF(3)CH(2)OH afforded two types of products.
Organic Letters 02/2012; 14(3):736-9. · 5.86 Impact Factor
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Chemistry 09/2011; 17(45):12573-7. · 5.93 Impact Factor
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ABSTRACT: A series of o-hydroxyaryl imidazolinium pro-ligands 3a−3e were synthesized by the reactions of 4-bromo-2,4,6-tri-tert-butyl-2,5-cyclohexadien-1-one (1) with different N-substituted imidazoles. Treatment of the pro-ligands with Pd(OAc)2 afforded the corresponding bis(aryloxide-NHC) palladium complexes (NHC = N-heterocyclic carbene). The N-substituents at the NHCs were found to have significant effects on the structures of the bis(aryloxide-NHC) palladium complexes. Trans isomers were obtained when R = Me and iPr, while cis isomers were obtained for R = Ph and Mes (Mes = mesityl). However, for R = tBu, a cis isomer with a normal and an abnormal NHC ligand was obtained. All these complexes have been characterized by 1H and 13C NMR and HRMS spectroscopy. The molecular structures of the pro-ligand 3b and complexes 4−8 were determined by single-crystal X-ray diffraction analysis. With methylaluminoxane (MAO) as cocatalyst these bis(aryloxide-NHC) palladium complexes showed excellent catalytic activities up to 107 g of PNB (mol of Pd)−1 h−1 in the addition polymerization of norbornene.
10/2009;
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ABSTRACT: Thermal treatment of indenyl-functionalized imidazolium salts and N-heterocyclic carbenes with Ru3(CO)12 gave different products. The normal mononuclear metal complexes (2a, 2b) were obtained via direct reaction of indenyl-functionalized imidazolium salts (1a, 1b) with Ru3(CO)12. Unexpected intramolecular C-H activated products (3a, 3b, 4a, 4b) were obtained via thermal treatment of corresponding indenyl-functionalized N-heterocyclic carbenes. All complexes were determined by 1H NMR, 13C NMR, IR spectra and elemental analysis. The molecular structures of 2b, 3a, 3b and 4b were determined by X-ray diffraction.
Dalton Transactions 09/2009; · 3.84 Impact Factor
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ABSTRACT: The intramolecular sp2 and sp3 C-H activated products, as well as the monometalated products, based on the "(p-cymene)Ru(NHC)" framework were synthesised by treatment of a series of NHCs (1-R-3-methylimidazol-2-ylidene [R=Ph (1), Bn (2), t-Bu (3), i-Pr (4), Mes (5), Cy (6)] and 1,3-bis(isopropyl)imidazol-2-ylidene (7)) with [(p-cymene)RuCl2]2 under mild conditions. A new NHC precursor (1-tert-butyl-3-phenyl-4,5-dihydro-imidazol-2-ylidene) was also designed to compare the reactivity of sp2 C-H and sp3 C-H bonds upon cyclometalation, and only the sp3 C-H activated product (8) was observed. The factors that possibly determine the selectivity of intramolecular sp2 or sp3 C-H activation are elucidated by a series of experiments. In the cases where activation of both sp2 C-H and sp3 C-H is possible, steric factors overrode the others to dominate the regioselectivity of activation. All complexes were characterised by 1H NMR, 13C NMR and HRMS spectra. The molecular structures of 1, 3, 5, 6, 7, and 8 were confirmed by X-ray diffraction.
Dalton Transactions 08/2009; · 3.84 Impact Factor
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Berichte der deutschen chemischen Gesellschaft 11/2008; 2008(35):5494 - 5504. · 2.94 Impact Factor
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Berichte der deutschen chemischen Gesellschaft 01/2008; 2008(8):1277 - 1286. · 2.94 Impact Factor
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ABSTRACT: Thermal treatment of the SiH-functionalized cyclopentadienes (RC5H4)SiHMeR‘ [R = H, R‘ = Ph (1), PhCH2 (2); R = t-Bu, R‘ = Ph (3), PhCH2 (4)] with Ru3(CO)12 gave the cyclic dinuclear metal complexes trans-[(R‘MeSi)(η5-RC5H3)Ru(CO)2]2 [R = H, R‘ = Ph (7), PhCH2 (8); R = t-Bu, R‘ = Ph (10), PhCH2 (11)] containing two Si−Ru bonds via Si−H activation. A cyclopentenyl complex, [(η2-C5H7)SiMe(CH2Ph)Ru(CO)3]2 (9), bridged by a vinylsilyl ligand was also obtained from the reaction, but reactions of the SiH-functionalized tetramethylcyclopentadienes (C5Me4H)SiHMeR‘ [R‘ = Ph (5), PhCH2 (6)] with Ru3(CO)12 only gave the cyclic diruthenium complex [(PhMeSi)(η5-C5Me4)]Ru2(CO)6 (12) with one Si−Ru bond and the desilylation product [(η5-C5Me4H)Ru(CO)]2(μ-CO)2 (13). When 2 and 4 reacted with M(CO)6, the similar cyclic dinuclear complexes trans-[(PhCH2MeSi)(η5-RC5H3)M(CO)3]2 [R = H, M = W (18); R = t-Bu, M = Mo (15), W (20)] were obtained, in addition to the desilylation products [(η5-RC5H4)M(CO)3]2 [R = H, M = Mo (14), W (19); R = t-Bu, M = Mo (16), W (21)], but reactions of 6 with M(CO)6 only gave the desilylation products [(η5-C5Me4H)M(CO)3]2 [M = Mo (17); M = W (22)]. The molecular structures of 7, 9, 12, 13, 15, 18, and 20 were determined by X-ray diffraction.
07/2007;
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ABSTRACT: Ansa-Cyclohexyl-bis(4,5,6,7-tertrahydro-1-indenyl) zirconium dichloride (5) was used as catalyst for propylene and ethylene
polymerization together with methyl aluminoxane (MAO) as the cocatalyst. Isotactic polypropylene (PP) was obtained with the
highest activity of 6.37×107g PP (molZr)−1h−1. The meso-meso (mmmmm) pentads sequence content of PP was determined by 13C NMR spectroscopy. The dependence of the microstructure on the reaction temperature and the Al/Zr molar ratio was examined
and the catalytic activity of complex 5 was compared with that of the similar ansa-zirconocene 3. The high activity of the new zirconocene 5 for propylene isospectic polymerization at high temperature (60 °C) is the result of its unique bridged-group structure.
Complex 5/MAO displays also high catalytic activity of 0.46×106 to 9.87×106g PE(molZr)−1h−1 in the homo-polymerization of ethylene. The visometric molecular weight of PE ranges from 0.97×104 to 11.16×104 g·mol−1 under the given conditions.13C NMR spectroscopy analysis proves the PE to be linear polyethylene (LPE).
Journal of Wuhan University of Technology-Mater Sci Ed 01/2007; 22(4):667-672. · 0.35 Impact Factor
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ABSTRACT: The reaction of dibenzofuran 1, lithium pieces (2.2 equiv), and TMEDA (2.2 equiv) in dry ether under reflux led to a solution of the corresponding C,O-dilithiated intermediate 2 which, upon treatment with different ketones or aldehydes (0.8 equiv) at -78 degrees C, afforded, after hydrolysis and dehydration, 6,6-substituted-6H-dibenzo[b,d]pyrans 3 in good yields. The reaction undergoes reductive ring opening and cyclization, and the intermediate diol 4e was isolated.
The Journal of Organic Chemistry 11/2006; 71(21):8291-3. · 4.45 Impact Factor
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ABSTRACT: Reactions of CpArCHCHArCp [Ar = Ph (1), p-MeOC6H4 (2)] with Ru3(CO)12 in refluxing xylene afforded the unexpected bridging C−C cleavage and cyclopentadienyl coupling products: the 2,2‘-bisubstituted fulvalene diruthenium complexes (η5:η5-2,2‘-ArCH2C5H3C5H3CH2Ar)Ru2(CO)4 [Ar = Ph (5), p-MeOC6H4 (9)] and the partially hydrogenated products (η5:η3-ArCH2C5H3C5H6CHAr)Ru2(CO)4 [Ar = Ph (4), p-MeOC6H4 (8)], in addition to the normal bridged bis(cyclopentadienyl) tetracarbonyl diruthenium complexes (ArCHCHAr)[(η5-C5H4)Ru(CO)]2(μ-CO)2 [Ar = Ph (7), p-MeOC6H4 (10)]. When ligand (tBuC5H4)PhCHCHPh(tBuC5H4) (3) reacted with Ru3(CO)12, the tetrasubstituted fulvalene diruthenium complex (η5:η5-PhCH2tBuC5H2C5H2tBuCH2Ph)Ru2(CO)4 (11) and three normal bridged bis(cyclopentadienyl) diruthenium complexes (PhCHCHPh)[(η5-tBuC5H3)Ru(CO)]2(μ-CO)2 (12−14) were obtained. The molecular structures of 4, 5, 7-meso, 7-rac, 8, 10-meso, 11, 12, 13, and 14 were determined by X-ray diffraction. The stereochemistry of the reaction was also studied, and the possible mechanism was discussed.
01/2006;
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ABSTRACT: Thermal treatment of the pyridyl side-chain-functionalized cyclopentadienes with Fe(CO)5 and Ru3(CO)12 gave different intramolecular C−H activated products, in addition to the normal dinuclear metal complexes. Reactions of the dinuclear metal complexes with I2 also gave different metal iodide complexes.
11/2005;
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Baiquan Wang,
Bin Mu,
Xiaobin Deng,
Huiling Cui,
Shansheng Xu,
Xiuzhong Zhou,
Fenglou Zou,
Yang Li,
Ling Yang,
Yufei Li,
Youliang Hu
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ABSTRACT: A series of cycloalkylidene-bridged cyclopentadienyl metallocene complexes, [(CH(2))(n)C(C(5)H(4))(2)MCl(2)] (M = Ti, n = 4 (4), 5 (5), 6 (6); M = Zr, n = 4 (7), 5 (8), 6 (9); M = Hf, n = 4 (10), 5 (11), 6 (12)), have been synthesized and applied to ethylene polymerization after activation with methyl aluminoxane (MAO). The cycloalkylidene-bridged titanocene catalysts exhibit much higher activities than the corresponding zirconocene and hafnocene analogues, and have the highest activities at higher temperatures. In comparison, the silacyclopentylidene-bridged metallocene complexes [(CH(2))(4)Si(C(5)H(4))(2)MCl(2)] (M = Ti (13), Zr (14)) and isopropylene-bridged metallocene complexes [Me(2)C(C(5)H(4))(2)MCl(2)] (M = Ti (15), Zr (16)) have also been synthesized and applied to ethylene polymerization. In both cases, the titanocene complexes show much higher activities than the corresponding zirconocene analogues, especially at a lower temperature. The molecular structures of complexes 4-9 have been determined by X-ray diffraction. The structure-activity relationships, especially the effects of the bridges of ansa-metallocene complexes, are discussed.
Chemistry 02/2005; 11(2):669-79. · 5.93 Impact Factor
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12/2003;
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ABSTRACT: Dimolybdenum complexes (X)(Y)[(η5-C5H3)Mo(CO)3]2 [Y = Me2Si, X = Me2C, (CH2)5C, CH2; Y = Ph2Si, X= Me2C] and desilylation products (X)[(η5-C5H4)Mo(CO)3]2 were obtained from the reactions of carbon and silicon doubly bridged biscyclopentadiene ligands (X)(Y)(C5H4)2 with Mo(CO)6 in refluxing xylene. When these ligands reacted with W(CO)6, under similar conditions, in addition to ditungsten complexes (X)(Y)[(η5-C5H3)W(CO)3]2 [X = Me2C; Y = Me2Si, Ph2Si] and desilylation products (X)[(η5-C5H4)W(CO)3]2, a class of structurally novel complexes (X)(η5-C5H3)(η5,η1-C5H3)[(Y)W(CO)3][W(CO)3] [for X = Me2C, (CH2)5C; Y = Me2Si] with a W−Si bond were also isolated. The reactions of carbon and germanium doubly bridged biscyclopentadiene ligands (X)(Me2Ge)(C5H4)2 [X = Me2C, (CH2)5C] with Mo(CO)6 or W(CO)6 gave similar novel complexes (X)(η5-C5H3)(η5,η1-C5H3)[(Me2Ge)M(CO)3][M(CO)3] [X = Me2C, (CH2)5C; M = Mo, W] with a M−Ge bond. The reactions also produced degermylation products. However, the corresponding dimolybdenum or ditungsten complexes were not isolated in these cases. The molecular structures of 2, 6, 8, 10, 11, 13, 14, 15, 19, 21, 22, 25t, and 26t have been determined by X-ray diffraction. The M−M distances in complexes 2 [3.4328(12) Å], 8 [3.453(2) Å], and 11 [3.403(2) Å] are conspicuously elongated and are in fact the longest ever reported among the biscyclopentadienyl dimolybdenum or ditungsten complexes. The factors affecting the structures of dimolybdenum or ditungsten complexes are discussed.
10/2003;
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ABSTRACT: A novel trigonal-bipyramidal ruthenium carbonyl cluster, [(μ3-Ge){Ru(CO)2(η5-C5Me4H)}]2Ru3(CO)9 (3), was accidentally synthesized by thermal treatment of Ru3(CO)12 and C5Me4HMe2GeGeMe2C5Me4H in boiling decalin, along with the dinuclear ruthenium complex [(Me2Ge)(η5-C5Me4)Ru2(CO)6] (4). Similar treatment of Ru3(CO)12 and C5H5Me2GeGeMe2C5H5 in boiling heptane afforded three different bimetallic complexes, [(Me2Ge)(η5-C5H4)Ru2(CO)6] (1), [(Me2Ge)(η5-C5H4)Ru(CO)2]2 (2), and dimer [(η5-C5H5)Ru(CO)2]2. Molecular structures of 2, 3, and 4 have been determined by single-crystal X-ray diffraction.
07/2001;
