共查询到20条相似文献,搜索用时 11 毫秒
1.
Silver(I)-promoted intramolecular addition reaction between N-heterocyclic carbene and unsaturated esters in water is described. The reaction leads to 1H-imidazo[1,2-a]indole derivatives in moderate to excellent yields. 相似文献
2.
The reaction of allylic compounds with alkyl Grignard reagents in the presence of a catalytic amount of copper N-heterocyclic carbene (NHC) complexes proceeded predominantly in an SN2′ reaction pathway to give γ-substituted product in excellent yield. The method was applied to asymmetric reaction by using optically active NHC ligands. 相似文献
3.
Shravankumar KankalaRavikrishna Edulla Sarangapani ModemRavinder Vadde Chandra Sekhar Vasam 《Tetrahedron letters》2011,52(29):3828-3831
The intramolecular crossed aldehyde-ketone benzoin condensation in the chalcone of o-phthalaldehyde (OPA) catalyzed by N-heterocyclic carbene (NHCs) generated in situ from readily available imidazolium and thiazolium salts is described. In this reaction, bicyclic α-hydroxyl ketones (naphthalenone type tertiary alcohol) were selectively produced in good yields (75-94%) in shorter reaction times (20 min) through nucleophilic addition of acyl anion generated by umpolung in OPA-chalcone (regio controlled). 相似文献
4.
Angeles Martín 《Tetrahedron》2009,65(31):6147-3404
The nitrogen-centred radical generated by reaction of an N-phosphoramidate or N-cyanamide, attached to a tri- or tetramethylene tether extended from the C-1 of a carbohydrate, with (diacetoxyiodo)benzene (DIB) and iodine can undergo a regio- and stereoselective intramolecular hydrogen atom transfer (HAT) reaction to furnish four different oxa-azaspirobicyclic systems: 1-oxa-6-azaspiro[4.4]nonane, 1-oxa-6-azaspiro[4.5]decane, 6-oxa-1-azaspiro[4.5]decane and 1-oxa-7-azaspiro[5.5]undecane. A tandem 1,5- or 1,6-HAT-oxidation-nucleophilic cyclisation mechanism is proposed. 相似文献
5.
Taichi Kano 《Tetrahedron letters》2006,47(27):4615-4618
The synthetic utility of N-heterocyclic carbenes was demonstrated by the trialkylsilylcyanation of aldehydes, ketones and imines. In the presence of a catalytic amount of 3a, the reactions with Me3SiCN proceeded smoothly to give the corresponding cyanohydrin trimethylsilyl ethers or amino nitrile derivatives in good to excellent yields. 相似文献
6.
Naoko Saino 《Journal of organometallic chemistry》2006,691(14):3129-3136
An iron species derived from FeCl2 or FeCl3 by in situ reduction with zinc powder in the presence of imidazol-2-ylidene or bidentate nitrogen ligand could effectively catalyze intramolecular cycloisomerization of triynes to annulated benzenes. With a 2-iminomethylpyridine ligand, hydrates of FeCl2 and FeCl3 as well as their anhydrous ones could be used. 相似文献
7.
An unusual substitution reaction of an aromatic sulfonic group based on 3-carbonyl-4-phenolsulfonic acid was discovered in a diazo-coupling process.The reaction occurred under mild reaction conditions (pH 8.0-9.0.0-5 C,solvent:water) within a short reaction time(1h).A plausible substitution reaction mechanism by phenol-ketone resonance was proposed. 相似文献
8.
Highly diastereoselective cyclization (>20:1) as a new entry to functionalized cycloalkylamines has been conducted with acyclic N,O-acetal TMS ethers possessing an allylsilane moiety. 相似文献
9.
Novel synthesis of medium-sized oxa-heterocycles by palladium-catalyzed intramolecular Heck reaction
An efficient and high yielding method for the synthesis of eight-membered heterocyclic skeletons has been developed via palladium-catalyzed intramolecular Heck reaction. 相似文献
10.
Reactions of (IPr)Cu(X) (X = Cl or trifluoromethanesulfonate, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) complexes with the strong acids HOTf or HCl result in protonation of the C2 carbon of the IPr ligand to form imidazolium cations. Coordination of the imidazolium to the resulting CuI system depends upon the identity of the two counterions (chloride or triflate). The copper complexes [(IPrH)Cu(OTf)(μ-OTf)]2 and [IPrH][CuCl2] as well as the imidazolium salt [IPrH][OTf] have been characterized by NMR spectroscopy and single crystal X-ray diffraction studies. 相似文献
11.
Mitsushiro Nomura Suguru Iida Kazunori Kobayashi Satoshi Horikoshi Toru Sugiyama Masatsugu Kajitani 《Journal of organometallic chemistry》2011,696(9):1723-4038
The aromatic [CpCo(S2C2(R)(H))] (R = Ph, Me, 9-phenanthryl, H) complexes reacted with N-halosuccinimides (NXS; X = Cl, Br, I) in carbon tetrachloride at room temperature to undergo the N-succinimide substitution reaction on the dithiolene ring, but no halogenated dithiolene complex was obtained. The imidation products [CpCo(S2C2(R)(N-sccinimide))] were yielded up to 64% where X = I and R = 9-phenanthryl. The reaction of [CpCo(S2C2(Ph)(H))] with N-bromophthalimide (NBP) also gave the imidation product [CpCo(S2C2(Ph)(N-phthalimide))]. This is the rare direct imidation reaction to an aromatic metallacycle by NXS. The reaction of [CpCo(S2C2H2)] (R = H) with NIS afforded the double imidation product. One by-product in this reaction was the dithiolene-dithiolene homo-coupling product [CpCo(S2C2(R))]2 (R = Ph, Me, 9-phenanthryl). The microwave-enhanced (MW) reactions were attempted in the carbon tetrachloride solution. Although the solution temperature increased up to only 43 °C by MW irradiation, the imidation reaction worked with short reaction time. 相似文献
12.
A novel one-pot protocol for the preparation of cycloalkano[1,2-a]indoles by way of an intramolecular alkyl migration reaction in cyclic indolylborates is described. NaOMe was found to act as a successful trialkylboryl-protecting group against to the lithiation at the C2 of the indole ring. Treatment of cyclic indolylborates with electrophiles produced cycloalkano-[1,2-a]indoles. 相似文献
13.
Elizabeth Tyrrell Khatebeh MazloumiDonatella Banti Paulina SajdakAlex Sinclair Adam Le Gresley 《Tetrahedron letters》2012,53(33):4280-4282
The enantiospecific synthesis of chromanes and isochromanes obtained from an intramolecular Nicholas cyclisation reaction is discussed. During the course of this study we observed the formation of chroman-4-ones from a CAN deprotection step of a dioxolane and this is also discussed. 相似文献
14.
Emanuele Miserazzi Mario Alessandro SpottiRoberto Profeta Simone SpadaArnaldo Nalin Elisa MoroDaniele Andreotti 《Tetrahedron letters》2011,52(3):448-452
An interesting and surprising rearrangement was observed during the reaction of 4-N-benzyl piperazinone derivatives with Lawesson’s reagent as a thionating agent. Investigation into the possible mechanism responsible for these results is reported herein. 相似文献
15.
New, sterically demanding 1,3-dialkyl-3,4,5,6-tetrahydropyrimidinium salts (2) as NHC precursors have been synthesized and characterized. These salts, in combination with palladium acetate, provided active catalysts for the cross-coupling of aryl chlorides and bromides under mild conditions. The catalytic system was applied to the Heck, Suzuki and benzaldehyde (Kumada) coupling reactions. Catalyst activity was found to be influenced by the presence of a methoxy group on the ring of the p-position of benzyl substituent of the ligand precursor. 相似文献
16.
Norio Sakai Akimasa Watanabe Reiko Ikeda Yumi Nakaike Takeo Konakahara 《Tetrahedron》2010,66(46):8837-8845
The Me3SiCl-promoted intramolecular aminomethylation of a novel type of N,O-acetals, which were prepared via a facile three-step synthesis from N-alkylaniline derivatives and N-alkyl-2-oxazolidinones that leads to the production of pharmaceutically useful 1,4-benzodiazepine skeletons with a variety of functional groups is described. This method was successfully applied to the facile preparation of both tricyclic benzodiazepine derivatives and a 1,4-benzoxazepine derivative via 7-exo-trig cyclization. 相似文献
17.
This article presents a full account of intramolecular vinylic substitution reactions of bromoalkenes having an acetylthio moiety, which give sulfur-containing heterocycles such as dihydrothiophene, tetrahydrothiopyran, and 2-alkylidenethietane derivatives. The reaction pathways of the substitution reactions were investigated by theoretical and experimental studies. 相似文献
18.
Jingya Li 《Journal of organometallic chemistry》2007,692(17):3732-3742
A novel air- and moisture-stable carbene adduct of cyclopalladated ferrocenylimine has been synthesized and characterized. The structure of this compound was determined by X-ray crystal structure analysis. This adduct has been applied as an efficient catalyst for the amination of aryl chlorides. 相似文献
19.
Emanuele Attolino 《Tetrahedron letters》2007,48(17):3061-3064
An efficient and completely stereocontrolled synthesis of the N-glycan Manβ(1-4)GlcNAc disaccharide is achieved by propargyl mediated intramolecular aglycon delivery (IAD). Isomerisation of the 2-O-progargyl group of a manno thioglycoside to an allene is followed by iodonium ion mediated mixed acetal formation with the 4-OH of a protected GlcNAc derivative, and subsequent intramolecular glycosylation with complete control of anomeric stereochemistry. Access to this key disaccharide intermediate allows completion of the total synthesis of the core N-glycan pentasaccharide. 相似文献
20.
Ching-Feng Fu 《Tetrahedron》2010,66(12):2119-4589
N-Heterocyclic carbenes (NHCs) are known to be useful ligands for palladium-complex catalysis. It was found that [(NHC)Pd(PPh3)Cl2] is an effective pre-catalyst in Pd-catalyzed C-S cross coupling reactions to produce the functionalized sulfides in excellent yields. The turn over frequency (TOF) for the coupling of p-CH3C6H4Br with p-CH3C6H4SH reaches to 6.25 (mol of product) (mole of catalyst)−1 h−1. 相似文献