Diastereo- and Enantioselective Synthesis of Polyfunctional Cyclic Ketones with Neighboring Quaternary and Tertiary Stereogenic Centers via [2,3]-Wittig Rearrangement
摘要:
介绍了通过 SAEP-hydrazones 2 的不对称 [2,3]-Wittig 重排,非对映地和对映体选择性地合成具有邻近四元和三元立体中心的δ²-取代δ³,δ-不饱和环状δ-羟基酮 4 的方法,该方法具有良好的总收率(58-74%)、高反选择性(92-94%)和优异的对映体过量(ee ≥ 96%)。通过对腙 3b 的 X 射线结构分析和 1H NMR NOE 测量确定了其绝对构型。
Enhanced metal loading in SBA-15-type catalysts facilitated by salt addition: Synthesis, characterization and catalytic epoxide alcoholysis activity of molybdenum incorporated porous silica
摘要:
We report a novel method to increase the metal loading in SBA-15 silica matrix via direct synthesis. It was demonstrated through the synthesis and characterization of a series of molybdenum containing SBA-15 mesoporous silica catalysts prepared with and without diammonium hydrogen phosphate (DHP) as an additive. Catalysts prepared with DHP show a 2-3 times increase in incorporation of molybdenum in the silica matrix and pore size enlargement. The synthesized catalysts were characterized using nitrogen sorption, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma-optical emission spectroscopy (ICP-OES). The catalytic activity of catalysts prepared with DHP for alcoholysis of epoxides was superior than the catalyst prepared without DHP. Alcoholysis of epoxides was demonstrated for a range of alcohols and epoxides under ambient conditions in as little as 30 min with high selectivity. (C) 2014 Elsevier B.V. All rights reserved.