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Wenbin Lin

Publications and source records attributed to Wenbin Lin.

At least 37 records · Page 2Linked to original sources
PubMed2004

4,4'-Disubstituted BINAPs for highly enantioselective Ru-catalyzed asymmetric hydrogenation of ketones.

A family of tunable precatalysts Ru(4,4'-BINAP)(chiral diamine)Cl2 was synthesized and used for highly enantioselective hydrogenation of aromatic ketones. This result differs from previous chiral diphosphines that rely on the bis(xylyl)phosphino groups to control enantioselectivity. An X-ray structural study reveals that the bulky substituents on the 4,4'-positions of BINAP can effectively create a suitable chiral pocket in the transition state and thus provide a new mechanism for the enantiocontrol in such a remarkable asymmetric catalytic process.

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PubMed2004

Expeditious assembly of mesoscopic metallocycles.

Very large chiral metallocycles with tunable cavities in the range of 0.9-22 nm were efficiently assembled from the requisite metal- and ligand-terminated oligomers that are built from the 2,2'-diacetoxy-1,1'-binaphthyl-3,3'-bis(ethyne) bridging ligand and trans-Pt(PEt3)2 metal connector. These unprecedented nanoscopic and mesoscopic molecular metallocycles have been characterized with 1H, 13C{1H}, and 31P{1H} NMR spectroscopy, microanalysis, IR, UV-vis, and circular dichroism spectroscopies, MALDI-TOF MS, and size exclusion chromatography (SEC). SEC results indicated that the metallocycles appear to be much more compact and rigid than the metal- and ligand-terminated oligomers. The present molecular metallocycles provide interesting building blocks for the construction of larger functional structures that cannot be accessed from a top-down approach.

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PubMed2004

Chiral metallacyclophanes: self-assembly, characterization, and application in asymmetric catalysis.

[structure: see text] A family of chiral metallacyclophanes has been readily assembled based on robust Pt-acetylide linkage and characterized by a variety of spectroscopic techniques and X-ray crystallography. The steric congestion around the chiral dihydroxy groups in rigid metallacyclophane 4 prevents their reactions with Ti(O(i)()Pr)(4) to form active catalysts for enantioselective diethylzinc additions to aromatic aldehydes. In contrast, chiral dihydroxy groups in more flexible unclosed metallacyclophane 5 are effective ligands for enantioselective catalytic diethylzinc additions to aromatic aldehydes.

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PubMed2003

Chiral porous hybrid solids for practical heterogeneous asymmetric hydrogenation of aromatic ketones.

Chiral porous zirconium phosphonates containing Ru-BINAP-DPEN moieties were synthesized via a molecular building-block approach, and characterized by a variety of techniques including TGA, adsorption isotherms, XRD, SEM, IR, and microanalysis. These hybrid solids were used for enantioselective heterogeneous asymmetric hydrogenation of aromatic ketones with remarkably high ee values of up to 99.2%. These solid catalysts can also be easily recycled and reused for eight times without the loss of activity and enantioselectivity. Ready tunability of such a molecular building-block approach will allow the optimization of these hybrid materials and promise to lead to other practically useful heterogeneous asymmetric catalysts.

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PubMed2003

Highly enantioselective catalytic asymmetric hydrogenation of beta-keto esters in room temperature ionic liquids.

Polar phosphonic acid-derived Ru-BINAP systems were used to catalyze asymmetric hydrogenation of beta-keto esters in room temperature ionic liquids (RTILs) with complete conversions and ee values higher than those obtained from homogeneous reactions in MeOH (up to 99.3%), and were recycled by simple extraction and used for four times without the loss of activity and enantioselectivity.

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PubMed2003

Self-assembly of chiral molecular polygons.

Treatment of 2,2'-diacetyl-1,1'-binaphthyl-6,6'-bis(ethyne), L-H2, with 1 equiv of trans-Pt(PEt3)2Cl2 led to a mixture of different sizes of chiral metallocycles [trans-(PEt3)2Pt(L)]n (n = 3-8, 1-6). Each of the chiral molecular polygons 1-6 was purified by silica gel column chromatography and characterized by 1H, 13C{1H}, and 31P{1H} NMR spectroscopy, MS, IR, UV-vis, and circular dichroism spectroscopies, and microanalysis. The presence of tunable cavities (1.4-4.3 nm) and chiral functionalities in these molecular polygons promises to make them excellent receptors for a variety of guests.

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PubMed2003

Interlocked chiral nanotubes assembled from quintuple helices.

Homochiral helical chains were rationally synthesized from C2-symmetric 1,1-binaphthyl-6,6'-bipyridine ligands and linear metal-connecting points, Ni(acac)2. Five such homochiral helices associate in parallel to form nanotubes of 2 x 2 nm in dimensions which further intertwine to form periodically ordered, interlocked nanotubular architectures that possess nanometer-scale open channels and have high affinity for aromatic molecules. Chiral crown ethers have also been successfully incorporated into the walls of these nanotubes, which promises to lead to novel chiral zeolitic materials applicable in enantioselective processes.

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PubMed2003

Hierarchical assembly of homochiral porous solids using coordination and hydrogen bonds.

A family of homochiral metal carboxylate coordination polymers have been synthesized by treating 2,2'-dihydroxy-1,1'-binaphthalene-6,6'-dicarboxylic acid (H(2)BDA) with metal salts at elevated temperatures. BDA ligands link adjacent metal centers to form 1D coordination polymeric chains using the carboxylate functionality, while the hydroxyl groups of BDA ligands form H-bonds with carboxylate oxygen atoms to link 1D coordination polymeric chains into open frameworks of higher dimensionality. We also present evidence for the important role played by H-bonds in the stabilization of open framework structures which allows for the hierarchical assembly of chiral porous solids.

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PubMed2003

A chiral metallacyclophane for asymmetric catalysis.

Chiral metallacyclophanes were self-assembled from cis-(PEt3)2PtCl2 and enantiopure atropisomeric 1,1'-bina-phthyl-6,6'-bis(acetylenes) and used in highly enantioselective catalytic diethylzinc additions to aldehydes to afford chiral secondary alcohols.

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PubMed2002

Chiral crown ether pillared lamellar lanthanide phosphonates.

A new chiral bridging ligand, 2,2'-pentaethylene glycol-1,1'-binaphthyl-6,6'-bis(phosphonic acid), was synthesized in 40.7% overall yield in five steps and used to generate single crystals of the first porous lanthanide phosphonates with chiral crown ether pillars. Single-crystal and powder X-ray crystallography established that these chiral crown ether decorated lamellar solids retain their framework structures after the removal of their included guest molecules and serve as structural models for porous solids that are exploitable for bulk chiral separations.

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PubMed2002

Self-assembly of nanoscale, porous T-symmetric molecular adamantanoids.

Treatments of lanthanide nitrate or perchlorate and C2-symmetric 2,2'-hydroxy-1,1'-binaphthalene-6,6'-dicarboxylic acid (6,6'-H2BDA) led to diastereoselective self-assembly of nanoscale, porous molecular adamantanoids [Ln4(BDA)6(H2O)12]*12DMF (Ln = Gd, La, 1a,b). These adamantanoid clusters possess perfect T symmetry as a result of the C2-symmetric nature of BDA bridging ligands and C3-symmetric nature of lanthanide ions. Face-to-face intercluster hydrogen bonds formed between 2,2'-dihydroxyl groups of BDA ligands and carboxylate oxygen atoms direct the assembly of 3D polycages based on chiral molecular adamantanoid building blocks which possess two different types of open channels.

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PubMed2002

The first chiral organometallic triangle for asymmetric catalysis.

A family of chiral organometallic triangles based on cis-Pt(PEt3)2 metallocorners and enantiopure atropisomeric bis(alkynyl) bridging ligands (L1-4) has been synthesized and characterized by 1H, 13C{1H}, and 31P{1H} NMR, UV-vis, and circular dichroism (CD) spectroscopies, FAB and MALDI-TOF mass spectrometry, and microanalysis. Metallocycle 4 which contains three 1,1'-bi-2-naphthol functionalities in combination with Ti(iOPr)4 has been shown to be an excellent catalyst for highly enantioselective additions of diethylzinc to aromatic aldehydes to afford chiral secondary alcohols. This research illustrates the potential of generating novel functional materials on the basis of supramolecular chemistry.

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