Chemoselective Protection of Hydroxyl Groups and Deprotection of Silyl Ethers

 Trimethylsilylation of alcohols and phenols is carried out using hexamethyldisilazane and LiClO₄ under microwave irradiation and neutral conditions. The deprotection of silyl ethers is carried out similarly using natural kaolinitic clay and a few drops of water.     

单位圆内代数体函数的T半径

应用Ahlfors覆盖曲面的方法,在单位圆内构造了代数体函数的一个新的奇异半径(称为T半径),并应用无穷级的型函数推广了亚纯函数奇异方向的相关结论.     

Efficient and Selective Halogenation of Allylic and Benzylic Alcohols under Mild Conditions

Summary. A simple, mild, and high yielding procedure for the halogenation of allylic and benzylic alcohols using a combination of SOCl₂, benzotriazole, and potassium halides in DMF is described. The effectiveness of the protocol is manifested in its selectivity towards allylic and benzylic alcohols whereas other simple alcohols such as primary, secondary, and tertiary are found to be unreactive.     

Conformations of highly hindered aryl ethers: IX. Dipole moment evidence for an intramolecular donor-acceptor complex

In a search for evidence that a π cloud proximal halogen interaction is of importance to the mode of action of the thyroid hormones, the dipole moments of the 1'-naphthyl (I), (4.29 D), 4'-carboxymethylphenyl (II), (2.90 D), 2'-bromo4'-carboxymethylphenyl (III), (3.56 D), and methyl (IV), (3.24 D) ethers of 2,4dinitro-6-bromophenol were determined in benzene at 25 °C. The moments of (I), (II) and (III) are approximated best by those calculated for the twisted conformation in which the bromine closely approaches the face of the other ring. That of the naphthyl ether (I) can, however, be explained only by inclusion of an intramolecular electron donor-acceptor charge-transfer moment of 1.6 D directed from the π cloud of the naphthyl ring to the proximal nitro group of the other ring, or of 2.8 D to the proximal bromine of that ring. In the preferred conformation of the methyl ether (IV), the methoxy group is coplanar with the ring while the 2-nitro group is twisted 90° from coplanarity to accomodate it. A mesomeric moment of 2.3 D is estimated from this for the 2,4-dinitro-6-bromophenoxy moiety and is used in calculating the expected moments of the other ethers.     

Synthetic methods,III: Sulfated zirconia catalyzed thioacetalization of carbonyl compounds

Summary Sulfated zirconia effectively catalyzes the reaction of carbonyl compounds with 1,2-ethanedithiol or thiophenol to afford the corresponding dithioacetals as useful organosulfur synthons. Isolation of pure products in high yields by simple filtration and evaporation is an important feature of this method.

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Synthetische Methoden, 3. Mitt.: Thioacetalisierung von Carbonylverbindungen mit ZrO₂SO ₄ ^2– (Kurze Mitt.)

Zusammenfassung ZrO₂/SO _2– ⁴ katalysiert die Reaktion von Carbonylverbindungen mit 1,2-Ethandiol oder Thiophenol zu den als Organoschwefelsynthonen wertvollen entrsprechenden Dithioacetalen. Ein wichtiges Merkmal der Methode ist die einfache Isolierung der Produkte in guten Ausbeuten durch Filtration und Entfernung des Lösungsmittels.

     

ACTIVATION ENERGY OF DESORPTION OF DIBENZOFURAN ON ACTIVATED CARBONS

1. INTRODUCTION With the development of municipalization in China, more and more cities are challenged by the problem of how to dispose of the dramatically increased municipal waste. Generally, most of municipal solid waste is landfilled or dumped openly in the suburbs. It causes not only land waste, but also serious environment pollution. In order to solve efficiently the environment pollution caused by municipal solid waste, incineration technique was introduced in some big cities such…     

The Reduction of Aromatic Oximes to Amines with Borohydride Exchange Resin-Nickel Acetate System

Aromatic oximes were reduced to the corresponding amines with borohydride supported on an ion exchange resin (BER)- nickel acetate in methanol in good yields. The isolation of pure products by simple filtration and evaporation is an important feature of this method.