Borane-Catalyzed Reductive α-Silylation of Conjugated Esters and Amides Leaving Carbonyl Groups Intact
作者:Youngchan Kim、Sukbok Chang
DOI:10.1002/anie.201508669
日期:2016.1.4
valuable α‐silyl carbonyl products. The α‐silylation occurs chemoselectively, thus leaving the labile carbonylgroups intact. The reaction features a broad scope of both acyclic and cyclic substrates, and the synthetic utility of the obtained α‐silyl carbonyl products is also demonstrated. Mechanistic studies revealed two operative steps: fast 1,4‐hydrosilylation of conjugated carbonyls and then slow
本文描述了由B(C 6 F 5)3催化的α,β-不饱和酯和酰胺的氢化硅烷化反应,以提供具有合成价值的α-甲硅烷基羰基产物。α-甲硅烷基化是化学选择性发生的,因此保留了不稳定的羰基。该反应具有无环和环状底物的广泛范围,并且还证明了所得α-甲硅烷基羰基产物的合成效用。机理研究揭示了两个操作步骤:共轭羰基的快速1,4-氢化硅烷化,然后减慢甲硅烷基醚中间体的甲硅烷基迁移。
Asymmetric Olefin Isomerization of Butenolides via Proton Transfer Catalysis by an Organic Molecule
作者:Yongwei Wu、Ravi P. Singh、Li Deng
DOI:10.1021/ja205674x
日期:2011.8.17
general olefin isomerization was realized via biomimetic protontransfer catalysis with a new chiral organic catalyst. A broad range of mono- and disubstituted β,γ-unsaturated butenolides were transformed into the corresponding chiral α,β-unsaturated butenolides in high enantioselectivity and yield in the presence of as low as 0.5 mol % catalyst. Mechanistic studies have revealed the protonation as the
Et3N catalyzed direct α-addition cascade isomerization of deconjugated butenolides with α-ketoesters for the synthesis of α,γ-disubstituted butenolide derivatives
γ-disubstituted butenolides are widespread occurrences in numerous pharmacologically active molecules. In this paper, a highly efficient method for the synthesis of α,γ-disubstituted butenolide derivatives via a direct α-addition cascade isomerization of deconjugated butenolides with α-ketoesters using Et3N as catalyst, has been successfully developed. A series of α,γ-disubstituted butenolides have been
α,γ-二取代丁烯内酯广泛存在于许多药理活性分子中。本文成功开发了一种以 Et 3 N 为催化剂,通过去共轭丁烯内酯与 α-酮酯直接 α-加成级联异构化合成 α,γ-二取代丁烯内酯衍生物的高效方法。一系列 α,γ-二取代丁烯内酯的产率高达 97%,具有优异的区域选择性(高达 >19/1 rr)。据我们所知,迄今为止,在直接α-加成级联异构化制备α,γ-二取代丁烯内酯中应用去共轭丁烯内酯尚无先例。
Regioselective α-Addition of Deconjugated Butenolides: Enantioselective Synthesis of Dihydrocoumarins
deconjugated butenolides with ortho‐quinonemethides generated in situ afforded a series of functionalized 3,4‐dihydrocoumarins containing two contiguous stereogenic centers with excellent diastereo‐ and enantioselectivity. DFT calculations suggested that the rarely observed regioselectivity was due to the distortion energy that resulted from the interaction between the nucleophilic dienolate and the electrophilic
γ-substituted deconjugated butenolides is described. While Lewis base catalyst quinidine leveraged O-selective nitrosocarbonyl aldol reaction exclusively at the γ-position of deconjugated butenolides to produce γ-aminoxylation products, Lewis acid catalyst Cu(OTf)2 steered the competitive N-selective nitrosocarbonyl aldol reaction at the β-position, resulting in heterodifunctionalized butenolides. Both processes