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1.
Jean-Luc Vasse 《Tetrahedron letters》2004,45(34):6449-6451
Cyclopropylcarbinylzirconium complexes were generated from homoallylic ethers and zirconocene (Cp2ZrCl2/2n-BuLi). They underwent further in situ transformations that is, bromination-substitution, transmetallation-functionalization and insertion reactions to afford various cyclopropylcarbinyl derivatives. In contrast, ring-opening products could be selectively obtained by treating the zirconium complex with MeLi, prior to functionalization. 相似文献
2.
Gonçalves AG Noseda MD Duarte ME Grindley TB 《The Journal of organic chemistry》2007,72(26):9896-9904
Long-chain alkyl ether derivatives of sulfated oligosaccharides were semisynthesized as follows: two naturally occurring red seaweed galactans (neutral agarose and kappa-carrageenan) were submitted to partial reductive hydrolysis to give neutral and sulfated oligosaccharide alditols. The neutral disaccharide alditol (1) and its trityl ether (5) were sulfated and/or alkylated through formation of their dibutylstannylene or (bis)dibutylstannylene acetals. In these reactions, the dibutylstannylene acetals of the terminal 1,2-diols in the alditol units were more reactive than those formed on the cis-diols of the galactopyranosidic units. This property allowed the regioselective monoalkylation of a neutral tetrasaccharide alditol (2), which contained eleven free hydroxyl groups, the highest selectivity ever observed with dibutylstannylene acetals. An alkylated/sulfated derivative (11) was also obtained through the regioselective alkylation of a naturally sulfated disaccharide alditol (10, a kappa-carrageenan derivative). 相似文献
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5.
New compounds containing the thienotriazolopyrimidine and thienopyrimidotetrazine skeleton are prepared from the bifunctional intermediates 2,3‐diamino‐5,6‐dimethylthieno[2,3‐d]pyrimidin‐4(3H)‐one derivatives 13–17 . The 2,3‐dihydro‐3‐substituted‐5,6‐dimethylthieno[2,3‐d]pyrimidin‐4(1H)‐one derivatives 8–12 are also prepared. 相似文献
6.
[reaction: see text] Indoles are allylated and benzylated in moderate to quantitative yield when stirred with allyl and benzyl halides in 80% aqueous acetone in the presence of NH(4)HCO(3) at room temperature. 相似文献
7.
Mitsuo Ishikawa Takamasa Fuchikami Makoto Kumada 《Journal of organometallic chemistry》1978,162(2):223-238
Photolysis of phenylpentamethyldisilane, 1,1-diphenyltetramethyldisilane and 1-isopropyl-1-phenyltetramethyldisilane in the presence of a wide variety of olefins has been studied. All reactions investigated, with the exception of those with 1-methylcyclohexene and tetramethylethylene, afforded the corresponding 1/1 addition products. Yields of the adducts depended highly on the structure of the olefins used. In the photolysis of phenylpentamethyldisilane in the presence of an equimolar mixture of 1,1- and 1,2-bis(trimethylsilyl)ethene under competitive reaction conditions, the main product was the one arising from the 1,1-isomer. A possible mechanism for the process of addition of olefin to the photochemically generated silicon-carbon double-bonded intermediate (A) is discussed. 相似文献
8.
The cationic alkyl zirconocene complex Cp2Zr+Me[CH3B−(C6F5)3] is found to initiate the ringopening polymerization of 1,5,7,11-tetraoxaspiro[5,5]undecane under mild condition to give poly(oxypropylenepropylenecarbonate) with low polydispersity. The rate of the polymerization is first-order with respect to monomer and catalyst concentration. At high monomer concentration, the initial rate of polymerization becomes zero-order with respect to monomer concentration. 相似文献
9.
The trapping reaction of the transient intermediate ortho-quinone methides, generated by the insertion of arynes into a carbon–oxygen double bond of DMF, with dienophiles was investigated. The [4+2] cycloaddition products were obtained when the diesters of acetylenedicarboxylic acid were employed as dienophiles. 相似文献
10.
A convenient and efficient copper-catalyzed cascade method has been developed for the synthesis of benzimidazoquinazoline derivatives via reactions of readily available substituted 2-(2-halophenyl)benzoimidazoles with amidines or guanidine under mild conditions (even at room temperature). 相似文献
11.
Shahera Farhat 《Tetrahedron》2004,60(6):1329-1337
An easy and straightforward new method for the preparation of sp2 zirconocene derivatives from a wide range of heterosubstituted alkenes such as vinyl sulfides, sulfoxides and sulfones is described. In all cases, a complete isomerization of the stereochemistry is observed and only the E-isomer is obtained. The reactivity of the resulting vinylic organometallic can be increased by a transmetalation reaction into organocopper, organozinc or organopalladium species and, therefore, several carbon-carbon formation were easily realized. 相似文献
12.
Bonalumi N Vargas A Ferri D Baiker A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(33):9236-9244
The adsorption behavior of O-methyl and O-trimethylsilyl derivatives of cinchonidine (CD), employed as chiral modifiers for heterogeneous enantioselective hydrogenations on supported Pt catalysts, has been investigated by using attenuated total reflection infrared spectroscopy (ATR-IR) and density functional theory (DFT) electronic structure calculations. The ATR-IR spectroscopic investigation provided detailed insight of the adsorbed modifiers under conditions close to those employed during catalytic processes, and electronic structure calculations were used as a complement to the experiments to uncover the implications of conformational changes in generating the topology of the surface chiral site. The structural investigation of the adsorbed modifiers revealed a relationship between the spatial positions of the ether substituents and the enantiodifferentiation induced by the modified catalyst observed in the hydrogenation of alpha-activated ketones. Experiments and calculations corroborate a model, according to which the addition of a bulky ether group to CD reshapes the chiral sites, thus generating catalytic chiral surfaces with different and, in some cases (e.g. hydrogenation of ketopantolactone), even opposite enantioselective properties to those obtained with CD without altering the absolute configuration of the modifier. The study also confirms that active surface conformations of cinchona modifiers are markedly different from those existing in vacuum and in solution, thus underlying the necessity of investigating the surface-modifier interaction in order to understand enantioselectivity. 相似文献
13.
《Journal of organometallic chemistry》2007,692(1-3):579-584
1H-pyrrolin-2(5H)-one derivatives are easily obtained from carbonyl-ene-nitrile compounds and alkenes or alkynes by copper(II)-catalyzed tandem sequence involving vinylation or allylation as well as Ritter-type hydration and dehydrative cyclization. 相似文献
14.
6,6-二烷基富烯与有机锂的反应-双(取代环戊二烯基)钛, 锆衍生物的合成 总被引:6,自引:0,他引:6
本文研究了6,6-二烷基富烯与有机锂反应的立体效应。6,6二甲基、甲基乙基、二乙基、甲基苯基富烯与乙基锂易发生环外双键的还原反应。6-甲基-6-正丙基、异丁基富烯同正丁基锂则发生环外双键的加成反应。6,6-多亚甲基富烯[C5H4=C(CH2)n]与有机锂的反应随n值不同而异, n=4的富烯同正丙基锂和正丁基锂进行α-攫氢和环外双键还原的竞争反应; n=5,6 的富烯与乙基锂, 异丙基锂和异丁基锂发生还原反应, 与正丙基俚和正丁基锂则进行加成与还原的竞争反应,n=4 的富烯与芳基锂发生α-攫氢反应, 随n值增大则倾向于加成反应。通过上述反应所得的锂化合物合成了一系列新的仲、叔烷基和烯基取代的环戊二烯基钛、锆衍生物。应用^1HNMR证明了化合物的结构。 相似文献
15.
Combined polymerization catalysis of nickel complex and zirconocene for branched polyethylene 总被引:2,自引:0,他引:2
The polymerization behavior of 2-(2′-pyridyl) quinoxaline nickel dibromide/Cp2ZrCl2/MAO system was investigated in three ways: the Ni catalyst was added first, followed by addition of Zr catalyst (method I);
the Ni and Zr catalysts were added simultaneously (method II); and the Zr catalyst was added first, followed by addition of
Ni catalyst (method III). Results of GC-MS, GPC,13C NMR and DSC investigations indicated that the properties of resulting polyethylene were greatly varied by changing feeding
orders of the two catalysts. Decreasing Ni/Zr molar ratio or increasing polymerization temperature gave corresponding polyethylenes
with less branches and higher melting point. Compared to the procedure using Cp2ZrCl2 catalyst only, the activity of Zr catalyst in those combined system decreased because of the competition of ethylene between
the [Ni−C] and [Zr−C] active centers. In addition, other zirconocenes were also employed as copolymerization catalysts in
the combined system with nickel complex. compared to Cp2ZrCl2 case, the ethyl-bridged Zr catalyst performed better for polymerization of ethylene while the Si-bridged Zr catalyst showed
better copolymerization ability. 相似文献
16.
Treatment of 2-acetoxy glycopyranosyl azides with Ph3P gave isoxazolines by ring closure of the phosphorimine. Coupling of in situ generated isoxazolines with acylating reagents gave mixtures of alpha- or beta-glycopyranosyl amides. The alpha/beta ratio depended upon the acylating reagent and metal salts employed. For example, coupling of isoxazoline 3 with Z-Asp-(SPy)-OBn in the presence of CuCl2 gave exclusively alpha-N-glucopyranosylasparagine derivative 8. This general procedure has been applied to mono-, di-, and trisaccharide systems. 相似文献
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18.
Lee K Ryu JS Jin Y Kim W Kaur N Chung SJ Jeon YJ Park JT Bang JS Lee HS Kim TY Lee JJ Hong YS 《Organic & biomolecular chemistry》2008,6(2):340-348
A new series of geldanamycin derivatives were synthesized using a semi-synthetic approach involving genetically engineered biosynthetic intermediates. These analogues were then evaluated for anti-proliferation activity in human cancer cell lines, SK-Br3 and SK-Ov3. Most of the synthesized compounds exhibited potent in vitro anti-proliferation activity toward both cell lines. Such compounds potently inhibited the expression of the Hsp90 client protein ErbB2. 相似文献
19.
Franz Wochner Laszlo Zsolnai Gottfried Huttner Hans H. Brintzinger 《Journal of organometallic chemistry》1985,288(1):69-77
Ethylene-bridged titanocene and zirconocene derivatives with permethylated ring ligands, C2H4(C5(CH3)4)2TiCl2 and C2H4(C5(CH3)4)2ZrCl2, have been synthesized and their crystal structures determined. 相似文献
20.
A new effective Suzuki-Miyaura coupling reaction between alkynylboronic esters (generated in situ from acetylenic derivatives) and arylbromides or vinylbromides is reported. 相似文献