Fused-Ring Formation by an Intramolecular “Cut-and-Sew” Reaction between Cyclobutanones and Alkynes
作者:Lin Deng、Likun Jin、Guangbin Dong
DOI:10.1002/anie.201712487
日期:2018.3.1
alkynes to construct cyclohexenone‐fused rings is described herein. The challenge arises from the need for selective coupling at the more sterically hindered proximal position, and can be addressed by using an electron‐rich, but less bulky, phosphine ligand. The control experiment and 13C‐labelling study suggest that the reaction may start with cleavage of the less hindered distal C−C bond of cyclobutanones
Iodine-Mediated Electrophilic Cyclization of 2-Alkynyl-1-methylene Azide Aromatics Leading to Highly Substituted Isoquinolines and Its Application to the Synthesis of Norchelerythrine
作者:Dirk Fischer、Hisamitsu Tomeba、Nirmal K. Pahadi、Nitin T. Patil、Zhibao Huo、Yoshinori Yamamoto
DOI:10.1021/ja805326f
日期:2008.11.19
corresponding isoquinoline derivatives in excellent to allowable yields. Electron-donating and electron-accepting substituents on the aromatic ring were equally tolerated, and either acidic or basic (or even neutral) reaction conditions, depending on the reactivity of the substrate, could be applied to smoothly convert the azide starting materials into the desired isoquinoline products in moderate to good yields
Rhodium-catalyzed cyclic carbonylation of 2-ethynylbenzylalcohols under water-gas shift reactionconditions gives selectively 3-isochromanones which are derived from and one molecule each of hydrogen and carbon monoxide with incorporation of the hydroxymethyl group adjacent to the ethynyl group.
Synthesis of 2-Aryl Acetophenones via Hydrobromination and Oxy-isomerization of (<i>o</i>-Arylethynyl)benzyl Alcohols
作者:Tzu-Hsuan Kuan、Duen-Ren Hou
DOI:10.1021/acs.joc.1c00294
日期:2021.5.7
Hydrobromination and oxy-isomerization of (o-arylethynyl)benzyl alcohols to yield brominated aryl ketones were achieved with bromotrimethylsilane. The substrate scope suggested that vinyl carbocations, stabilized by the conjugated aryl groups, are the reaction intermediates. 1H-Isochromene was also detected by 1H NMR, and an isolated 1H-isochromene was converted to the product when retreated with TMSBr
用溴代三甲基硅烷实现了(邻-芳基乙炔基)苄醇的氢溴化和氧异构化,生成溴化的芳基酮。底物范围表明,通过共轭芳基稳定的乙烯基碳阳离子是反应中间体。还通过1 H NMR检测到1 H-异戊二烯,当用TMSBr处理时,分离出的1 H-异戊二烯转化为产物。1 H-异戊二烯的形成等同于6-内挖-环化,并与在基本条件下的相应反应形成对比,在该条件下,以5-外-挖为主导。
Cyclization reactions of 2-alkynylbenzyl alcohol and 2-alkynylbenzylamine derivatives promoted by tetrabutylammonium fluoride
The regioselectivity of the cyclization reaction of 2-ethynylbenzyl alcohol and 2-ethynylbenzylamine derivatives promoted by TBAF was investigated. Six-membered ring derivatives were obtained from the compounds, which have a butyl group on the triple bond. Whereas five-membered ring products were afforded from the substrates having hydrogen or aromatic substituents. on the acetylene moiety. It was also concluded that both the tetrabutylammonium cation and fluoride anion were essential for the cyclization. Thus, the actual mechanism and catalytic cycle were also suggested. (C) 2001 Elsevier Science Ltd. All rights reserved.