使用K 12 Ga 4 L 6四面体催化剂评估主体结构对分子内Prins反应的选择性和机理的影响。通过修改螯合部分的结构和芳香族间隔基的大小来改变主体结构。虽然通常观察到螯合剂取代基的变化会影响速率的变化,但不会影响选择性,但改变主体间隔基会导致效率和产物非对映选择性的差异。观察到失误数量极高(高达 840 次)。测得的最大速率加速度约为 10 5,这是使用合成主体催化剂测得的最大过渡态稳定量级之一。据观察,宿主/客体尺寸效应在宿主介导的对映选择性中发挥重要作用。
Über eine neue Synthese von Citral und verwandten Verbindungen
作者:G. Saucy、R. Marbet、H. Lindlar、O. Isler
DOI:10.1002/hlca.19590420624
日期:——
A new method for the preparation of α,β-unsaturated aldehydes and α,β;γ,δ-unsaturated ketones is described. The method is based upon the rearrangement of acetates of tertiary ethynyl carbinols to allenic acetates in the presence of acetic acid and silver or copper catalyst; partial conversion of the allenic acetates to diacetates takes place under the reaction conditions. In some cases enol acetates
Novel Preparation of α,β-Unsaturated Aldehydes. Benzeneselenolate Promotes Elimination of HBr from α-Bromoacetals
作者:Andrei Vasil'ev、Lars Engman
DOI:10.1021/jo9917644
日期:2000.4.1
elimination/hydrolysis of these mixtures afforded alpha,beta-unsaturated aldehydes in 50-80% overall yields. In the case of tertiary alpha-bromoacetals, treatment with benzeneselenolate afforded only dehydrobromination products as mixtures of isomers. The presence of at least a catalytic amount of the organoselenium reagent was found to be crucial for olefin formation. A SET-mechanism, involving benzeneselenolate-induced
The ?Aldol Condensation? of Citral and Related Reactions
作者:Alan F. Thomas、Ren�e Guntz-Dubini
DOI:10.1002/hlca.19760590642
日期:——
The reaction of citral with anhydrous base leads initially to a cyclohexa-1,3-dienecarbaldehyde. Stronger base and longer reaction times result in deconjugation to a cyclohexa-1,4-diene-carbaldehyde, together with oxidative loss of six carbon atoms to yield 2-methyl-4-(4-methylpent-3-enyl)benzaldehyde. A mixed aldolreaction between citral and 3-methyl-2-butenal (= senecia aldehyde) is described.
The selective hydrogenation of furfural (a biomass-derived platform compound, CO versus CC) is an important reaction for the production of chemical intermediates widely used in the polymer industry. Herein, we report three non-precious intermetalliccompounds (IMCs) (Ni3Sn1, Ni3Sn2 and Ni3Sn4) derived from a layered double hydroxide (LDH) precursor, which are characterized by a highly uniform dispersion
糠醛的选择性加氢(生物质衍生平台化合物,C ö与Ç C)是用于生产广泛用于聚合物工业的化学中间体的重要反应。在此,我们报道了从层状双氢氧化物(LDH)前体衍生的三种非贵金属互化物(IMC)(Ni 3 Sn 1,Ni 3 Sn 2和Ni 3 Sn 4),其特征在于IMC的高度均匀分散纳米颗粒,并显示出惊人的催化性能,可将糠醛(CO)选择性氢化为糠醇。特别是Ni 3 Sn 2IMC表现出最佳的催化性能(转化率:100%;选择性:99%),超过了报道的非贵金属催化剂,甚至可以与贵金属催化剂(例如Au,Pd和Pt)相媲美。基于原位FT-IR,XANES和Bader电荷研究的组合研究验证了电子从Sn到Ni的转移,从而促进了Ni顶部位点上C O键的吸附活化,同时抑制了C C的吸附。研究(原位FT-IR和催化评估)和理论计算(DFT计算和微动力学模型)揭示了糠醛分子在Ni 3 Sn 2上的垂直吸附构型I
Iron-iron oxide core–shell nanoparticles are active and magnetically recyclable olefin and alkyne hydrogenation catalysts in protic and aqueous media
作者:Reuben Hudson、Antoine Rivière、Ciprian M. Cirtiu、Kylie L. Luska、Audrey Moores
DOI:10.1039/c2cc16438h
日期:——
We report for the first time the use of iron-iron oxide core-shellnanoparticles for the hydrogenation of olefins and alkynes under mild conditions in ethanol and in an aqueous medium. This catalyst proves robust towards the presence of oxidants, such as oxygen and water, is magnetically recoverable and shows selectivity towards the less activated double bonds.