Transformation of Terminal Diols of Cyclic and Acyclic Saccharides to Epoxides and Alkenes by Reaction with Triphenylphosphine,Imidazole and Iodine

ABSTRACT

Reaction of various terminal diols 1,4,6,8-12, derived from cyclic and acyclic monosaccharides, with 2 mol equivalents each of TPP-imidazole-I₂ between -8 °C and 15 °C in THF afforded the corresponding epoxides 2,5,7,13-17, respectively, with 4 mol equivalents each of TPP-imidazole-I₂ in toluene at reflux temperature the starting diols afforded the corresponding alkenes 3,18-24, respectively.     

Efficient Synthesis of Epoxides from Vicinal Diols Via Cyclic Sulfates

Reaction of cyclic sulfates of vic-diols with sodium hydroxide in THF-MeOH produced the corresponding epoxides in excellent isolated yields at room temperature. Cyclic sulfates of trans-diols gave cis-epoxides, and cyclic sulfates of cis-diols afforded trans-epoxides exclusively. Various cyclic sulfates of vic-diols can be converted into the epoxides under the conditions.     

Preparation and Characterization of PbS Nanoparticles via Cyclic Microwave Radiation Using Precursor of Lead (II) Oxalate

PbS nanoparticles have been successfully synthesized through a simple, rapid microwave route using lead (II) oxalate as precursor, [Pb(O₄C₂)]. In this study, four different sulfur sources were applied that including sodium thiosulfate (Na₂S₂O₃), thioacetamide (NH₂CSCH₃), thioglycolic acid (HSCH₂CO₂H), and l-cysteine (HO₂CCH(NH₂)CH₂SH). The effects of sulfur sources on morphology and size of products in two different solvents, ethylene glycol (EG) and poly EG (PEG 400), were investigated. The products were analyzed by X-ray diffraction analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray energy dispersive spectroscopy. Photoluminescence was used to study the optical properties of PbS nanoparticles.     

微乳液反应法制备草酸铜均匀微粒

在Ｔｒｉｔｏｎ ｘ－１００－ｎ－Ｃ６Ｈ１３ＯＨ／ｃ－Ｃ６Ｈ１２／水溶液（硝酸铜或草酸）体系Ｗ／Ｏ微乳液中，通过变换草酸和硝酸铜溶液的速度、温度和ｐＨ值而获得超细、方形的、管状的以及网络状的多种形态粒子，特别是制备得到方形和管状两种均匀胶体粒子。研究了影响粒子形态和大小的因素。     

Synthesis and Characterization of CdS Nanoparticles via Cyclic Microwave from Cadmium Oxalate

The present study reports synthesis and characterization of CdS nanoparticles prepared by cyclic microwave route with the use of [Cd(C₂O₄)·3H₂O] powder as a precursor. The products, with an average size ~15 nm, were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, thermogravimetric analysis, transmission electron microscopy and Fourier transform infrared spectroscopy. Optical property of obtained product was investigated by photoluminescence spectroscopy. The prepared nanostructures displayed a very strong luminescence at 528 nm (2.34 eV) at room temperature.     

草酸镁二水合物的非等温热分解动力学

The thermal decomposition of the magnesium oxalate dihydrate in a static air atmosphere was investigated by TG-DTG techniques. The intermediate and residue of each decomposition were identified from their TG curve. The kinetic triplet, the activation energy E, the pre-exponential factor A and the mechanism functionsf（a） were obtained from analysis of the TG-DTG curves of thermal decomposition of the first stage and the second stage by the Popesou method and the Flynn-Wall-Ozawa method.     

阴离子交换树脂催化丙烯腈与二醇的Michael加成反应

利用阴离子交换树脂为催化剂进行了丙烯腈与二醇的Ｍｉｃｈａｅｌ加成反应的研究，对影响反应的诸因素进行了讨论，产物收率为７０－９０％。     

Reaction of Cyclic Sulfates with Phosphines

In their reactions with phosphines, cyclic sulfates 9, 10, 11, and 12 afforded corresponding olefins by way of phosphonium sulfate salts whereas sugar cyclic sulfates 21 and 22 gave anhydrosugar 23.     

Preparation of Primary and Secondary Azidosugars from Diols using the Dioxaphosphorane Methodology

ABSTRACT

Treatment of methyl 2,3-di-O-benzyl-α-D-glucopyranoside (1), methyl 2,3-di-O-acetyl-α-D-glucopyranoside (4), 3-O-benzyl-1,2-O-(1-methylethylidene)-α-D-glucofuranose (6), 3-O-acetyl-1,2-O-(1-methylethylidene)-α-D-glucofuranose (9), 1,2-O-(1-methylethylidene)-α-D-xylofuranose (11) and methyl 2,3-di-O-acetyl-α-D-galactopyranoside (15) with diisopropylazodicarboxylate-triphenylphosphine in tetrahydrofuran led to the corresponding dioxaphosphoranes, which were opened by trimethylsilyl azide affording the silylated primary azidodeoxysugars. When the same reaction was performed on methyl 2,3-di-O-benzyl-α-D-galactopyranoside (20), an inversion of the regioselectivity of the dioxaphosphorane opening was observed, leading mainly to the 4-azido-4-deoxy-α-D-glucopyranoside derivative 27.     

Preparation of Diphenyl Oxalate from Transesterification of Dimethyl Oxalate with Phenol over TS—1 Catalyst

Diphenyl oxalate was synthesized from transesterification of dimethyl oxalate with phenol over TS-1(2.5 wt% Ti)catalyst.TS-1 catalyst,as a beterogeneous catalyst,showed excellent selectivity of diphenyl oxalate and methylphenyl oxalate compared with other homogeneous catalysts.Lewis acid sites on TS-1 catalyst were the active sites for transesterification of dimethyl oxalate with phenol.the high selectivity was closely related to the weak acid sites over TS-1.     

Synthesis of Diethyl Oxalate by a Coupling—Regeneration Reaction of Carbon Monoxide

This article describes a process for the synthesis of diethyl oxalate by a copling reaction of carbon monoxide,catalyzed by palladium in the presence of ethyl nitrite ,The kinetics and mechanism of the coupling and regeneration reaction are also discussed ,This paper presents the results of a scale-up test of the catalyst and the process based on an a priori computer simulation.     

New Preparation of Cyclic Acyloxyphosphorane by Reaction of Glyoxylic Acid with Phosphorus(III) Compounds

We have recently found that the reaction of α-keto acids (1) with phosphorus (III) compounds (3) yielded cyclic acyloxyphosphoranes(C-AOPs, 4), a new class of pentacovalent phosphorus species having a P-OC(O) group.^{1, 2)} The present paper deals with a new reaction of glyoxylic acid (2) with 3 to give C-AOPs (5) having no substituent at the C-3 position. 1 is an α-keto acid whereas 2 can be taken as an α-formyl acid. Although it is well known in the field of organic chemistry that the formyl group often behaves differently from a keto group, the reaction of 2 with 3 provides an example in which both groups behave in a similar manner.     

Non-isothermal Kinetics of the First-stage Decomposition Reaction of Cobalt Oxalate Dihydrate

Introduction Solid state kinetics has been extensively studied by means of thermal analysis methods[1]. The aim of the study is to determine the mechanism function f(α) , the activation energy E and the pre-exponential factor A. In recent years there have been many methods of processing thermal analysis kinetic data[2-11].     

Synthesis of Diethyl Oxalate by a Coupling-Regeneration Reaction of Carbon Monoxide

This article describes a process for the synthesis of diethyl oxalate by a coupling reaction of carbon monoxide, catalyzed by palladium in the presence of ethyl nitrite. The kinetics and mechanism of the coupling and regeneration reaction are also discussed. This paper presents the results of a scale-up test of the catalyst and the process based on an a priori computer simulation.     

Organocatalyzed Enantioselective Desymmetrization of Diols in the Preparation of Chiral Building Blocks

Desymmetrization of diols is a powerful tool to the synthesis of chiral building blocks. Among the different approaches to perform discrimination between both enantiotopic hydroxyl groups, the organocatalytic approach has gained importance in the last years. A diverse range of organocatalysts has been used to efficiently promote this enantioselective transformation and this Minireview examines the different contributions in this field.