An Improved Procedure for the Synthesis of Terminal and Internal Alkynes from 10-Undecenoic Acid

A remarkable solvent preference for dehydrobromination to yield 10-Undecynoic acid (5) and 9-Undecynoic acid (6) is observed in the case of 10,11-dibromoundecanoic acid (1). Thus, 10-Undecenoic acid can be easily and quantitatively converted to 6 in PEG-400, while 5 is produced in PEG-200. 5 can also be obtained in non-polar solvents with PEG-200/400 as a phase transfer catalyst.     

Synthesis and Crystal Structure of a Hexameric Organooxotin Cluster from Benzilic Acid

1 INTRODUCTION There is great interest in the study of organotin carboxylic ester compounds due to their consider- able biological activities and structural diversities[1~3]. Since Holmes, R. R.[4] first reported the hexameric drum organotin compound, many organotin carboxy- lic ester compounds with drum-shape have been syn- thesized in recent years[5, 6]. It has been revealed that organotin compounds containing carboxylate ligands with additional donor atoms that are available for coord…     

An Improved Procedure for N-Ethynylpyrrole

N-Ethynylpyrrole can be obtained in good overall yields by reacting pyrrole with potassium tert-butoxide and trichloroethene in tetrahydrofuran, and subsequently dechlorinating the adduct with methyllithium or n-butyllithium in diethyl ether.     

An Improved Procedure for the Epoxidation of Methyl Cinnamate Derivatives and Production of Acid Sensitive Epoxides

By using a biphasic epoxidation system, unreactive methyl cinnamate derivatives were epoxidized at higher rates, and epoxides that decomposed in the presence of m-chlorobenzoic acid (mCBA) to diol ester opening products under standard conditions were obtained in fair to excellent yields.     

一种改进的制备手性氨基醇的方法

采用NaBH4/TiCl4还原体系 ,在THF溶剂中 ,将手性氨基酸还原制备相应的氨基醇 ,具有相对经济、操作简便、可大量制备等优势 .     

An Improved Reductive Methylation Procedure for Quinones

The reductive methylation of quinones bearing electron donating groups such as hydroxyl or alkoxyl groups proceeds in good yields. The improved conditions greatly extend the scope of this useful reaction.     

An Improved Synthesis of Retinoic Acid from β-Ionone

A convenient and large-scale preparation of retinoic acid 1 from β-ionone in five steps with 38% overall yield is described.The key steps are the epoxidization of 2 with a new methylated agent and the condensation 4 with tetraethyl methylenediphophonate in one-pot procedure to prepare 6.     

An Improved and Convenient Procedure for the Synthesis of Ozagrel

Ozagrel 1 is a 1-alkylimidazole derivative that acts as a selective inhibitor ofthromboxane A2 (TXA2) with an IC50 of 11mol/L. The beneficial effects of TXA2inhibition by ozagrel include improved motor coordination after experimental stroke, andantihypert…     

An Improved Procedure for the Synthesis of Ethyl Glycidate

Ethylglycidate (1), is a useful intermediate which can be used in several reactions involving epoxide ring opening with the introduction of an ester function and in co-polymer chemistry (1,2). Emmons and Pagano (3) described the preparation of I by epoxidation of ethyl acrylate with peroxytrifluoroacetic acid in 54% yield.     

An Improved Procedure for the Synthesis of Prostaglandin Analogues

Hydrozirconation-iodination of a terminal acetylene followed by lithium-iodide exchange and finally dilithio cyanocuprate mediated conjugate addition to an appropriate cyclopentenone is reported as an efficient method for the synthesis of prostaglandin analogues.     

An Efficient Procedure for Esterification of Aryloxyacetic Acid and Arylthioacetic Acid Catalyzed by Silica Sulfuric Acid

Aryloxyacetate and arylthioacetate are wildly used in herbicides, plant regulator and insecticides. Recently, Wille et al. have reported that methyl aryloxyacetate is an efficient agent to prevent and treat allergic contact dermatitis.[1] The most popular synthesis is by heating sodium phenoxide (mercaptide) with ethyl chloroacetate in DMF,[2] or by the esterification of acid with alcohol using concentrated H2SO4 as catalyst.[3] In this paper, synthesis of aryloxyacetate and aryl thioacetate from aryloxyacetic acid and arylthioacetic acid respectively in ether catalyzed by silica sulfuric acid in 83%～94% yields is described. The catalyst is reused for 3 times without significant loss of activity (Entry 4). Compared with common procedures, the present procedure possesses the advantages of the operational simplicity, short reaction time,less-corrosion, high yield and reusable catalyst.     

An Improved General Procedure for the Synthesis of Aryloxysulfonyl Azides

In 1975, we have described the first synthesis of the aryloxysulfonyl azides (aryl azidosulfates),¹ the interest of which is confirmed to be varied, especially about the elaboration of molecules such that sulfamates² (Ar-O-SO₂-NH₂), not easily accessible by other methods and endowed with very important biological properties.^3–5 Their cycloaddition on bicyclic olefinic systems gives a new family of N-substituted aziridines, the N-aryloxy-3-aza-tricyclo[3,2,1,0^{2,4 exo}]octanes.⁶ They react with trivalent phosphorus compounds to afford some very interesting phosphine-imides.⁷     

山楂叶中熊果酸提取工艺研究

以熊果酸的提取率为指标,采用单因素与正交实验相结合的方法对提取工艺进行了优化,得到最佳提取参数为:乙醇体积分数95%、提取温度85℃、提取时间110min、液固比5:1、提取次数3次。在该条件下,熊果酸提取率为93.47%。该工艺简单合理,为工业生产提供了理论参考。     

An Improved Procedure for the Purification of Catalytically Active Alkane Hydroxylase from Pseudomonas putida GPo1

Bacterial alkane hydroxylases are of high interest for bioremediation applications as they allow some bacteria to grow in oil-contaminated environments. Furthermore, they have tremendous biotechnological potential as they catalyse the stereo- and regio-specific hydroxylation of chemically inert alkanes, which can then be used in the synthesis of pharmaceuticals and other high-cost chemicals. Despite their potential, progress on the detailed characterization of these systems has so far been slow mainly due to the lack of a robust procedure to purify its membrane protein component, monooxygenase AlkB, in a stable and active form. This study reports a new method for isolating milligramme amounts of recombinant Pseudomonas putida GPo1 AlkB in a folded, catalytically active form to purity levels above 90%. AlkB solubilised and purified in the detergent lauryldimethylamine oxide was demonstrated to be active in catalysing the epoxidation reaction of 1-octene with an estimated K (m) value of 0.2 mM.     

An Improved Procedure for the Oxidation of Alkynols to Alkynoic Acids

The chromic acid oxidation of alkynols I to the corresponding alkynoic acids II is a well known process.¹ However, in most cases, the yield of the desired acid is poor to moderate (20–50%) due to the formation of the ester III as a by-product.     

Improved Procedure for Determining Free and Conjugated Indole-3-Acetic Acid by a Spectrofluorimetric Kinetic Method

Abstract

The Indole-3-acetic acid (IAA), ester-and amide-linked IAA in peach seeds were determined by a kinetic method based on the measurement of the Indole-α-pyrone derivative of the free acid. The free acid concentration was 355 ng/g of fresh weight, the concentrations for the ester-and amide-conjugated IAA were 877 and 1785 ng/g of fresh weight, respectively. The relative standard deviation was always less than 15%.     

Alkoxycarbonyl- and Carboxylate-Group Migrations in the Benzilic Acid Rearrangement of Ethyl Cyclopropane-2, 3-dioxopropionate

In alkaline medium C₃H₅? CO? C (OH)₂? COOEt ( 1b ) is transformed into C₃H₅? C (OH)(COOH)₂ ( 2a ). Labelling experiments show that the cyclopropyl group is not shifted, but only ROOC and/or ^?O₂C groups. GC./MS. and NMR. analysis after incomplete reaction show that both ROOC- and ^?O₂C-groups Migrate; at higher pH (ca. 14) the ester group rearrangement seems to be more important than at pH ca.9-10.     

An Improved Procedure for Aryne Generation from o-Triazenylarylboronic Acids through One-Pot Boronate Formation/Silica Gel Treatment

We have developed an improved method for generating aryne from o-triazenylarylboronic acids. Unlike the previous method that required excess o-triazenylarylboronic acids as aryne precursors, we used corresponding boronates as limiting reagents, which resulted in high yields. By combining the formation of boronates and aryne generation through silica gel treatment in one-pot, we were able to effectively use a wide range of o-triazenylarylboronic acids in reactions with various arynophiles. This one-pot method was particularly suitable for transforming complex aryne precursors with different functional groups.     

Synthesis and Crystal Structure of a Copper(II) Complex with Benzilic Acid and 1,10-Phenanthroline

A new complex [Cu(phen)3][(C6H5)2C(OH)COO]2·6H2O was prepared by self-assembly of benzilic acid, 1,10-phenanthroline (phen), and copper perchlorate. It crystallizes in triclinic, space group P1, with a = 1.14661(17), b = 1.6455(2), c = 1.6457(2) nm, α = 74.779(2), β = 74.904(3), γ = 84.424(3)o, V = 2.8914(7) nm3, Dc = 1.340 g/cm3, Z = 2, F(000) = 1218, GOOF = 1.018, the final R = 0.0643 and wR = 0.1633. The crystal structure shows that the copper ion is coordinated with six nitrogen atoms from six 1,10-phenanthroline molecules, forming a distorted octahedral coordination geometry.     

An Improved Synthesis of 5-Fluorothiophene-2-Carboxylic Acid

A new and efficient route to 5-fluorothiophene-2-carboxylic acid 1 was secured in two steps and 62% yield overall.