Stereoselective routes to substituted β-amino carbonyl compounds via heterodiene [4π+2π] cycloadditions of auxiliary-based C2 symmetric ketene acetals

Heterodiene [4π+2π] cycloadditions of (S,S)-4,5-diaryl-2-methylene-1,3-dioxolanes 1 to a series of β-amido-α,β-unsaturated carbonyl compounds are diastereoselective (d.r.≥4:1). The products can be purified by trituration or crystallisation and hydrolysed with acid to generate the corresponding β-amido carbonyl compounds, the overall sequence effecting an auxiliary-based enantioselective conjugate addition of an acetate enolate, leading to β-aminoacid derivatives.     

Synthesis, characterization and luminescence study of dimethyl(β-ketoiminato)gallium (-indium) complexes: crystal structure of dimethyl[1-phenyl-3-N-(4-methoxyphenylimino)-1-butanonato]gallium

Six dimethylgallium (indium) complexes of type Me₂ML [M = Ga, L = 1-phenyl-3-N-(phenylimino)-1-butanonato (1), 1-phenyl-3-N-(p-methoxyphenylimino)-1-butanonato (2), 1-phenyl-3-N-(o-chloro phenylimino)-1-butanonato (3); M = In, L = 1-phenyl-3-N-(phenyl imino)-1-butanonato (4), 1-phenyl-3-N-(p-methoxyphenylimino)-1-butanonato (5), 1-phenyl-3-N-(o-chlorophenylimino)-1-butanonato (6)] have been synthesized by reaction of trimethylgallium (indium) with appropriate 1-phenyl-3-N-(arylimino)-1-butanones. The complexes obtained have been characterized by elemental analysis, ¹H NMR, IR and mass spectroscopy. Structure of 2 has been determined by X-ray single-crystal analysis, in which Ga atom is four coordinated. Complexes 1-6 emit colors from blue to green (463-491 nm) when irradiated by UV light. The electroluminescent (EL) properties of 1-6 were examined by fabricating EL devices using 1-6 as emitter, respectively. The EL bands are located in the green region (509-522 nm).     

对苯二甲酸-铕-钇配合物的合成及荧光性质

以对苯二甲酸(H2L)为配体,合成了系列(Eu1-xYx)2L3.3H2O固体粉末配合物.通过元素分析、紫外吸收光谱、X射线衍射和红外光谱确定了配合物的组成和结构,并通过荧光光谱研究了它们的荧光性质.结果表明钇掺入配合物后,能增强Eu3+的特征荧光,当铕与钇的摩尔比为0.05∶0.95时荧光强度最强.     

One-pot synthesis of 5-(substituted-amino)pyrazoles

An efficient and mild one-pot synthesis of substituted 5-alkylamino and/or 5-(arylamino)pyrazoles is described. A suitably decorated β-ketoamide, an aryl or alkyl hydrazine and Lawesson's reagent are suspended in THF/Py and gently heated to yield the requisite 5-aminopyrazoles.     

Coating Carbon Nanotubes with Europium Oxide

Carbon nanotubes (CNTS) coating with europium oxide by a simple method is reported in this letter for the first time. The CNTS were refluxed in a solution of nitric acid containing europium nitrate, and the pH value was subsequently ajusted with ammonia solution. At last, the mixture was filtered and annealed. The TEM micrograph showed that the CNTS were covered with a uniform thin layer with thickness of about 15 nm. The XRD results revealed that the CNTS were coated with europium oxide.     

Direct catalytic asymmetric Mannich-type reactions of isomerizable aliphatic imines: chemoselective enolate formation from a hydroxyketone by a Zn-catalyst

A direct catalytic asymmetric Mannich-type reaction of isomerizable aliphatic imines is described. A Et₂Zn/(S,S)-linked-BINOL complex was suitable for chemoselective enolate formation from a hydroxyketone in the presence of isomerizable aliphatic N-diphenylphosphinoyl imines. The reaction proceeds smoothly and β-alkyl-β-amino-α-hydroxyketones were obtained in good yield and high enantioselectivity (up to 99% ee), albeit in modest to low diastereoselectivity.     

Stereoselective synthesis of (Z)-γ-cyano-β-perfluoroalkyl-β,γ-unsaturated esters

(Z)-γ-Cyano-β-perfluoroalkyl-β,γ-unsaturated esters have been synthesized by the reaction of perfluoroacylated phosphonates with organozinc reagent in 50-71% (three steps) yields.     

Improved synthesis of a [4.4]-spirolactam β-turn mimetic as surrogate of the didemnin side chain dipeptide Pro-N-Me-d-Leu

An efficient synthesis of [4.4]-spirolactam restricted derivatives of the didemnin side chain dipeptide l-Pro-N-Me-d-Leu is described. This methodology involves: (a) peptide coupling of N-Boc-2-allylproline with d-Leu-OBn; (b) OsO₄/NaIO₄ mediated allyl oxidation and intramolecular cyclization to the corresponding cyclic hemiaminals; and (c) NaBH₄ mediated reduction of an intermediate N-acyliminium ion. This synthetic strategy gave significant better results than the previously reported strategies for the synthesis of [4.4]-spirolactam β-turn mimetics.     

An improved method for synthesizing antennary β-d-mannopyranosyl disaccharide units

The merits of an indirect protecting method for hydroxyl groups using allyl groups via allyloxycarbonyl groups in the synthesis of antennary β-d-mannopyranosyl disaccharides from β-d-galactopyranosyl disaccharides were studied. Regioselective allyloxycarbonylation and conversion reactions involving simultaneous double S_N2 nucleophilic substitution at C-2′ and C-4′ of benzyl O-[β-d-galactopyranosyl]-(1-4)-3,6-di-O-benzyl-2-deoxy-2-N-phthalimido-β-d-glucopyranoside were examined for comparison with the direct allylation method. The required β-d-mannopyranosyl disaccharide having proper protecting groups was obtained using this indirect method in 52% yield. In contrast, the reported direct allylation method using methyl O-(β-d-galactopyranosyl) disaccharide gave the corresponding β-d-mannopyranosyl disaccharide in only 7.5% yield.     

Polymer-Attached Thiazolium Salts-Catalyzed Addition of Aldehydes to α, β-Unsaturated Carbonyl Compounds

A homogeneous catalyst, 3-benzyl-5-(2-hydroxyethyl)-4-methyl-1,3-thiazolium chloride, for addition of aldehydes to activated double bond, was attached to 20% cross-linked polystyrene-divinylbenzene copolymer. The attached catalysts could be easily removed from the reaction mixture. Polymer-attached thiazolium salts in the presence of triethylamine are active catalysts for addition of aromatic and aliphatic aldehydes to α,β-unsaturated ketones to yield γ-diketones.