Zhenxing Xi - Academia.edu (original) (raw)
Uploads
Papers by Zhenxing Xi
Catal. Sci. Technol., 2014
An analog of Grubbs' second generation catalyst with a tetralkylammonium chloride containing ... more An analog of Grubbs' second generation catalyst with a tetralkylammonium chloride containing phosphine exhibits faster rates in the presence of polystyrene-SO3Ag.
Tetrahedron, 2008
An efficient copper-catalyzed N-arylation and N-heteroarylation reactions of imidazole, pyrrole, ... more An efficient copper-catalyzed N-arylation and N-heteroarylation reactions of imidazole, pyrrole, indole, pyrazole, and perimidine with aryl or heteroaryl halides using pyridine-functionalized 1,3-diketone as ligands have been investigated. The ligands bearing pyridyl and 1,3-diketone moieties, which may form chelated Cu(I) species, are inexpensive and readily available. The combination of CuI and 1,3-di(pyridin-2-yl)propane-1,3-dione is very efficient for CeN coupling reactions to afford various N-arylated products in good to excellent yields.
Organic Letters, 2011
Analogs of Grubbs' second generation catalyst with hydrophilic phosphine ligands are synthesized,... more Analogs of Grubbs' second generation catalyst with hydrophilic phosphine ligands are synthesized, and those with Cy 2 PCH 2 CH 2 N(CH 3) 3 þ Cl À and Cy 2 P À CHCH 2 CH 2 N(CH 3) 2 þ CH 2 À CH 2 Cl À give much faster ring closing metatheses under CH 2 Cl 2 /aqueous or CH 2 Cl 2 /aqueous HCl biphasic as opposed to CH 2 Cl 2 monophasic conditions. This is attributed to rapid phase transfer of the dissociated ligand to the aqueous phase, where under acidic conditions it is protonated.
The Journal of Organic Chemistry, 2008
We describe the first nickel-N-heterocyclic carbene catalyzed Negishi cross-coupling reaction of ... more We describe the first nickel-N-heterocyclic carbene catalyzed Negishi cross-coupling reaction of a variety of unactivated aryl chlorides, heterocyclic chlorides, aryl dichlorides, and vinyl chloride. The mononuclear and binuclear nickel-NHC complexes supported by heteroarene-functionalized NHC ligands are found to be highly efficient for the coupling of unactivated aryl chlorides and organozinc reagents, leading to biaryls and terphenyls in good to excellent yields under mild conditions. For all aryl chlorides, the binuclear nickel catalysts show activities higher than those of mononuclear nickel complexes because of possible bimetallic cooperative effect.
The Journal of Organic Chemistry, 2008
The Kumada cross-coupling reaction of a variety of unactivated aryl chlorides, vinyl chlorides, a... more The Kumada cross-coupling reaction of a variety of unactivated aryl chlorides, vinyl chlorides, and heteroaryl chlorides catalyzed by nickel(II) complexes containing pyridine-functionalized NHC ligands is described. The catalysts are so active that the reactions proceed at room temperature in excellent yields.
Journal of Coordination Chemistry, 2007
Organometallics, 2008
ABSTRACT [Ni2(3,5-bis(N-methylimidazolylidenylmethyl)pyrazolate)2](PF6)2 (1), [Ni2(μ-OH)(3,5-bis(... more ABSTRACT [Ni2(3,5-bis(N-methylimidazolylidenylmethyl)pyrazolate)2](PF6)2 (1), [Ni2(μ-OH)(3,5-bis(N-pycolylimidazolylidenylmethyl)pyrazolate)](PF6)2 (2), and [Ni2(μ-OH)(3,5-bis(N-pyridylimidazolylidenylmethyl)pyrazolate)](PF6)2 (3) have been prepared from the corresponding imidazolium salts via in situ generated silver-carbene complexes. The complexes and imidazolium salts were characterized by elemental analyses and NMR spectroscopy. The structures of 1−3 were identified by X-ray diffraction analysis. In complex 1, two nickel(II) ions are sandwiched by two 3,5-bis(N-methylimidazolylidenylmethyl)pyrazolates behaving as anionic tetradentate ligands. Complexes 2 and 3 contain Ni2(μ-OH) cores with two nickel centers bridged by anionic hexadentate imidazolylidene ligands. Complexes 2 and 3 show excellent catalytic activities in Suzuki−Miyaura and Kumada−Corriu coupling reactions of various aryl chlorides. The cross-coupling reactions of deactivated aryl chlorides with arylboronic acids and Grignard reagents have been accomplished in excellent yields at low catalyst loadings.
Dalton Transactions, 2009
Organometallics, 2008
ABSTRACT
Catal. Sci. Technol., 2014
An analog of Grubbs' second generation catalyst with a tetralkylammonium chloride containing ... more An analog of Grubbs' second generation catalyst with a tetralkylammonium chloride containing phosphine exhibits faster rates in the presence of polystyrene-SO3Ag.
Tetrahedron, 2008
An efficient copper-catalyzed N-arylation and N-heteroarylation reactions of imidazole, pyrrole, ... more An efficient copper-catalyzed N-arylation and N-heteroarylation reactions of imidazole, pyrrole, indole, pyrazole, and perimidine with aryl or heteroaryl halides using pyridine-functionalized 1,3-diketone as ligands have been investigated. The ligands bearing pyridyl and 1,3-diketone moieties, which may form chelated Cu(I) species, are inexpensive and readily available. The combination of CuI and 1,3-di(pyridin-2-yl)propane-1,3-dione is very efficient for CeN coupling reactions to afford various N-arylated products in good to excellent yields.
Organic Letters, 2011
Analogs of Grubbs' second generation catalyst with hydrophilic phosphine ligands are synthesized,... more Analogs of Grubbs' second generation catalyst with hydrophilic phosphine ligands are synthesized, and those with Cy 2 PCH 2 CH 2 N(CH 3) 3 þ Cl À and Cy 2 P À CHCH 2 CH 2 N(CH 3) 2 þ CH 2 À CH 2 Cl À give much faster ring closing metatheses under CH 2 Cl 2 /aqueous or CH 2 Cl 2 /aqueous HCl biphasic as opposed to CH 2 Cl 2 monophasic conditions. This is attributed to rapid phase transfer of the dissociated ligand to the aqueous phase, where under acidic conditions it is protonated.
The Journal of Organic Chemistry, 2008
We describe the first nickel-N-heterocyclic carbene catalyzed Negishi cross-coupling reaction of ... more We describe the first nickel-N-heterocyclic carbene catalyzed Negishi cross-coupling reaction of a variety of unactivated aryl chlorides, heterocyclic chlorides, aryl dichlorides, and vinyl chloride. The mononuclear and binuclear nickel-NHC complexes supported by heteroarene-functionalized NHC ligands are found to be highly efficient for the coupling of unactivated aryl chlorides and organozinc reagents, leading to biaryls and terphenyls in good to excellent yields under mild conditions. For all aryl chlorides, the binuclear nickel catalysts show activities higher than those of mononuclear nickel complexes because of possible bimetallic cooperative effect.
The Journal of Organic Chemistry, 2008
The Kumada cross-coupling reaction of a variety of unactivated aryl chlorides, vinyl chlorides, a... more The Kumada cross-coupling reaction of a variety of unactivated aryl chlorides, vinyl chlorides, and heteroaryl chlorides catalyzed by nickel(II) complexes containing pyridine-functionalized NHC ligands is described. The catalysts are so active that the reactions proceed at room temperature in excellent yields.
Journal of Coordination Chemistry, 2007
Organometallics, 2008
ABSTRACT [Ni2(3,5-bis(N-methylimidazolylidenylmethyl)pyrazolate)2](PF6)2 (1), [Ni2(μ-OH)(3,5-bis(... more ABSTRACT [Ni2(3,5-bis(N-methylimidazolylidenylmethyl)pyrazolate)2](PF6)2 (1), [Ni2(μ-OH)(3,5-bis(N-pycolylimidazolylidenylmethyl)pyrazolate)](PF6)2 (2), and [Ni2(μ-OH)(3,5-bis(N-pyridylimidazolylidenylmethyl)pyrazolate)](PF6)2 (3) have been prepared from the corresponding imidazolium salts via in situ generated silver-carbene complexes. The complexes and imidazolium salts were characterized by elemental analyses and NMR spectroscopy. The structures of 1−3 were identified by X-ray diffraction analysis. In complex 1, two nickel(II) ions are sandwiched by two 3,5-bis(N-methylimidazolylidenylmethyl)pyrazolates behaving as anionic tetradentate ligands. Complexes 2 and 3 contain Ni2(μ-OH) cores with two nickel centers bridged by anionic hexadentate imidazolylidene ligands. Complexes 2 and 3 show excellent catalytic activities in Suzuki−Miyaura and Kumada−Corriu coupling reactions of various aryl chlorides. The cross-coupling reactions of deactivated aryl chlorides with arylboronic acids and Grignard reagents have been accomplished in excellent yields at low catalyst loadings.
Dalton Transactions, 2009
Organometallics, 2008
ABSTRACT