Chitosan-supported L-proline complex was synthesized and applied as a catalyst for the direct asymmetric aldol reaction in various organic solvents and water as well. It was found that the novel synthesized catalyst was able to efficiently catalyze the aldol reaction in various media. The catalytic capacity and stereoselectivity of the catalyst were obviously improved with the introduction of aqueous micelle, possibly because the micelle functioned as a hydrophobic pocket, like the hydrophobic portion in enzymes. Moreover, the present synthetic catalyst showed performance similar to that of enzymes and could be used as a model of enzyme catalysis to help better understand the mystic mechanism of enzymes.

Well-defined polyethylene molecular brushes were synthesized, for the first time, by combining polyhomologation and ring opening metathesis polymerization (ROMP).

A novel one-pot methodology combining anionic polymerization and polyhomologation, through a ''bridge'' molecule (BF 3 OEt 2 ), was developed for the synthesis of polyethylene (PE)-based block copolymers. The anionically synthesized macroanion reacts with the ''bridge'' molecule to afford a 3-arm star (trimacromolecular borane) which serves as an initiator for the polyhomologation.Polyethylene (PE)-based materials are very important to modern life covering a wide spectrum of applications from commodity plastics (e.g. packaging, bottles) to precision-processed biomaterials (e.g. total joint replacement and medical devices).1 In order to better understand the behaviour and improve the performance of these materials, welldefined (controllable molecular weight, narrow molecular weight and structural distribution) PE-based polymers are needed. 2 Unfortunately, anionic polymerization which gives access to well-defined polymers when chain growth occurs in a ''living'' fashion is not compatible with ethylene, the monomer of PE. 3 The only way to prepare well-definedPEs by anionic polymerization is by hydrogenation of the corresponding anionically prepared PBd-1,4. However, the produced PE possesses butylene units originating from the hydrogenation of the unavoidable 1,2-units (minimum 5%) formed during the chain growth. 4 Recently, Shea developed a novel polymerization methodology leading to perfectly linear PEs. 5 The general reaction scheme involves the formation of an organoboron zwitterionic complex between a methylide (monomer) and a trialkylborane Lewis acid (initiator) which breaks down by the intramolecular 1,2-migration. As a consequence, the methylene group of methylide is randomly inserted one by one into the three branches of the trialkylborane leading to a 3-arm PE star. The resulting star is subsequently oxidized/hydrolysed to give perfectly OH-end-capped linear PEs. Molecular weights from 500 to 5.0 Â 10 5 and the polydispersity index (PDI) typically less than 1.1 have been reported. For this type of polymerization Shea coined the name polyhomologation or C1 polymerization. 5-7By using functionalized ylides and/or organoboranes, functionalized linear and nonlinear homo/copolymers, such as a-hydroxylo-allylic PE, 3-armed a-hydroxyl PE star, PE-co-PP(polypropylene) and cyclic PE have been synthesized. Here, we report a novel one-pot methodology combining anionic polymerization and polyhomologation, through a ''bridge'' molecule (BF 3 OEt 2 ), for the synthesis of polyethylene (PE)-based block copolymers. The synthetic approach involves: (a) the synthesis of a 3-arm star polymer (trimacromolecular borane, macroinitiator) by reacting living macroanions with BF 3 OEt 2 , (b) the in situ polyhomologation of dimethylsulfoxonium methylide, with the macroinitiator to produce a 3-arm star block copolymer of PE, and (c) the oxidation/hydrolysis by trimethylamine N-oxide dihydrate (TAO) to afford the PE-based block copolymers. As examples the syntheses of PBd-b-PE (PBd: polybutadiene) and PS-b-PE are shown in Scheme...

Novel well-defined bilayered molecular cobrushes with internal polyethylene blocks, P(PE core -b-PS corona ) (PE: polyethylene; PS: polystyrene), and ω-hydroxyl-functionalized polyethylene homobrushes, P(PE-OH), were synthesized through the macromonomer strategy. Two main steps were involved in the synthesis of the P(PE core -b-PS corona ) bilayered cobrushes: (i) formation of norbornyl-terminated macromonomer (Nor-PE-b-PS) by esterification of PS-b-PE-OH (combination of anionic polymerization, hydroboration, and polyhomologation) with 5-norbornene-2-carboxylic acid and (ii) ring-opening metathesis polymerization (ROMP) of Nor-PE-b-PS. The synthesis of P(PE-OH) was achieved by (i) hydroboration of tertbutyldimethylsilyl-protected allyl alcohol, followed by polyhomologation of dimethylsulfoxoniun methylide with the formed tri[3-(tert-butyldimethylsilyloxyl)propyl]borane initiator, oxidation/hydrolysis, and esterification of the TBDMS-O-PE-OH with 5-norbornene-2-carboxylic acid to afford the macromonomer TBDMS-O-PE-Nor, and (ii) ROMP of TBDMS-O-PE-Nor, followed by deprotection. Nuclear magnetic resonance spectroscopy ( 1 H and 13 C NMR) and high temperature gel permeation chromatography (HT-GPC) were used to characterize all macromonomers/molecular brushes and differential scanning calorimetry (DSC) to study the thermal properties. The molecular brush P(PE-b-PS) showed lower melting point (T m ) and better solubility in toluene than the corresponding macromonomer PS-b-PE-Nor. In the case of homobrushes, the thermal properties were strongly affected by the presence of the PE end-groups.