Iron-Promoted Elimination of β-Thioalkoxy Alcohols. Olefination by Coupling of a Carbonyl Group with a Dithioacetal
摘要:
Treatment of propargylic dithiolanes with (BuLi)-Bu-n followed by a carbonyl electrophile yields the corresponding propargylic dithioacetals. Upon treatment with 1 equiv of Fe(acac)(3) and excess MeMgI, elimination of SR and OH moieties from 8 affords the corresponding olefins in satisfactory yield. Benzylic dithioacetals behave similarly. The reaction can be considered an alternative of McMurry coupling of two different carbonyl equivalents.
Cyclopentenones are synthetically versatile structures, and their straightforward construction from alkynone substrates by employing synthetically streamlining C-H insertion is conceptually appealing and of high synthetic potential. But, its implementation is very limited. Herein we report a Au-catalyzed version, which affords 2-bromocyclopent-2-en-1-ones with a broad scope and synthetically desirable
环戊烯酮是合成通用的结构,它们通过合成流线型 CH 插入从炔酮底物直接构建在概念上具有吸引力且具有高合成潜力。但是,它的实施非常有限。在此我们报告了一种 Au 催化的版本,它提供了具有广泛范围和合成所需的非对映选择性的 2-bromocyclopent-2-en-1-ones。所提出的能够插入未活化 CH 键的关键中间体是一种完全功能化的金亚乙烯基,它是通过一种新的分子间策略产生的。这种可能的金亚乙烯基的灵活获取为探索其多功能反应性提供了各种机会。
has been developed toward a range of carbocycles. The key success is based on the use of a batch of newly designed cyclic carbonates as substrates that can provide carbon–carbon zwitterion intermediate under palladium catalysis. The kinetics of the reactions are controllable toward either strained seven- or thermodynamically more favored five-membered carbocycles. The release of this chemistry will
alkynyl ketones with 1,2-ethanedithiol in the presence of BF 3 -OEt 2 in methanol afforded the corresponding dithioacetal. Removal of the silyl group under basic conditions followed by palladium-catalyzed coupling reactions with aryl iodides yielded the corresponding propargylic dithioacetals in excellent yield.
Mild propargylic oxidation using a diacetoxyiodobenzene/tert-butyl hydroperoxide protocol
作者:Yi Zhao、Angela Wan Ting Ng、Ying-Yeung Yeung
DOI:10.1016/j.tetlet.2014.06.032
日期:2014.7
A mild propargylic oxidation of alkynes is reported using a diacetoxyiodobenzene/tert-butylhydroperoxide (DIB/TBHP) protocol. The reactions proceed smoothly at 0 °C and a number of α,β-unsaturated alkynoic ketones are obtained.
Stepwise palladium-catalyzedcross-coupling between terminalalkynes and vinyl triflates afforded the first cross-conjugated enyne macrocycles constructed of 3-alkylidene-1-propynyl [-C≡C-C(=CR2)-] building blocks, namely, the expanded radialene 1 and the hybrid radialene 2.