甲硅烷基烯醇醚5和β-内酰胺9(R = Me 3 Si)偶联得到酮13a-d。化合物13a,13c和13d转化为三环内酰胺16-20、23-25。(光学纯的甲硅烷基烯醇醚5的化学酶法合成可得到同手性内酰胺23-25。)此外,酮氮杂环丁酮13被保护为1,3-恶唑烷30。使用Bouffard方法进行所需的立体化学反应,得到醇32。形成相应的碳酸硝基苄酯,脱保护和氧化提供了酮35a和35b,其随后分别转化为三苯甲基41a和41b。
Epoxides can be cleaved in a regio- and stereoselective manner under neutral conditions with alcohols and acetic acid in the presence of catalytic amounts of decatungstocerate(IV) ion, ([CeW10O36]8−), affording the corresponding β-alkoxy and β-acetoxy alcohols in high yields. In water, ringopening of epoxides occurs with this catalyst to produce the corresponding diols in good yields.
可以在中性条件下用醇和乙酸在催化量的decatungstocerate(IV)离子([CeW 10 O 36 ] 8-)存在下,以区域和立体选择性的方式裂解环氧化合物,得到相应的β-烷氧基和β-乙酰氧基醇收率高。在水中,该催化剂会发生环氧化物的开环反应,从而以高收率生产出相应的二醇。
Design and preparation of a polymer resin-supported organoselenium catalyst with industrial potential
作者:Yuguang Wang、Lihua Yu、Bingchun Zhu、Lei Yu
DOI:10.1039/c6ta02566h
日期:——
activated species that could be re-oxidized by air so that no excess H2O2 was required for the reaction. The results were superior to those of reactionscatalyzed by small molecules, for which excess H2O2, long reaction time or expensive CF3-activated catalysts and environmentally unfriendly MeCN solvent were required.
六价硒?是! 与小分子聚合物相比,聚合物上的硒具有完全不同的特性。在有机硒化学中稀有的六价硒被发现是聚合物中的主要物种。可回收的聚合物树脂上的高价硒元素可以快速催化环己烯与水中的H 2 O 2氧化反应,以几乎定量的产率生产工业上重要的中间体反式-1,2-环己二醇。在催化循环中,高价硒物种被还原为二价硒,这是一种高度活化的物种,可以被空气重新氧化,因此没有过量的H 2 O 2。反应所需的。结果优于由小分子催化的反应,需要过量的H 2 O 2,较长的反应时间或昂贵的CF 3活化催化剂以及对环境不利的MeCN溶剂。
Reduction of Aliphatic and Aromatic Cyclic Ketones tosec-Alcohols by Aqueous Titanium Trichloride/Ammonia System. Steric Course and Mechanistic Implications
In contrast to the dissolved metal and metal hydride reductions, the reduction of cyclic ketones by the aqueous TiCl3/NH3 system favours the formation of the less thermodynamically stable axial alcohol. The ammonium ion formed in situ is essential for the reduction to proceed because it behaves as a mild Bronsted acid in basic medium and favours the protonation of the intermediate ketyl. The corresponding
Reduction of Carbonyl Compounds by Lanthanide Metal/2-Propanol: In-situ Generation of Samarium Isopropyloxide for Stereoselective Meerwein−Ponndorf−Verley Reduction
reducing agent may be samariumisopropyloxide, which mediates the Meerwein−Ponndorf−Verley-type hydride-transfer reaction, since the reaction can be carried out catalytically with respect to samarium. The stereoselectivities of the reductions of the 2- and 4-substituted cyclohexanones with Sm/iPrOH were higher than those achieved with SmI2/iPrOH or Sm/H2O. The asymmetric reduction of acetophenone could
Bismuth(III) Chloride (BiCl<sub>3</sub>); An Efficient Catalyst for Mild, Regio- and Stereoselective Cleavage of Epoxides with Alcohols, Acetic Acid and Water
Abstract Epoxides can be cleaved in a regio- and stereoselective manner with alcohols, acetic acid and water in the presence of catalytic amounts of bismuth(III) chloride, affording the corresponding β-alkoxy and β-acetoxy alcohols and diols in high yields.