Ionic Liquid as Catalyst and Reaction Medium: A Simple and Efficient Procedure for Paal–Knorr Furan Synthesis
作者:Gangqiang Wang、Zhi Guan、Rongchang Tang、Yanhong He
DOI:10.1080/00397910902978049
日期:2010.1.14
The ionicliquid 1-butyl-3-methyl-imidazolium hydrogen sulfate, [bmim]HSO4, efficiently catalyzes Paal–Knorr furan synthesis without any organic solvent. A wide range of aliphatic and aromatic 1,4-diketones easily undergo condensations to form furan derivatives, providing a general and convenient procedure. The Paal–Knorr reaction of ester-substituted 1,4-diketones is first reported. The ionic liquid
Base-Catalyzed Stereoselective Vinylation of Ketones with Arylacetylenes: A New C(sp3)C(sp2) Bond-Forming Reaction
作者:Boris A. Trofimov、Elena Yu. Schmidt、Igor' A. Ushakov、Nadezhda V. Zorina、Elena V. Skital'tseva、Nadezhda I. Protsuk、Al'bina I. Mikhaleva
DOI:10.1002/chem.201000227
日期:——
those with condensed aromatic moieties, are readily vinylated with arylacetylenes (KOH/DMSO, 100 °C, 1 h) to give regio‐ and stereoselectively the (E)‐β‐γ‐ethylenic ketones ((E)‐3‐buten‐1‐ones) in 61–84 % yields and with approximately 100 % stereoselectivity. This vinylation represents a newC(sp3)C(sp2) bond‐forming reaction of high synthetic potential.
σ-Bond initiated generation of aryl radicals from aryl diazonium salts
作者:Elene Tatunashvili、Bun Chan、Philippe E. Nashar、Christopher S. P. McErlean
DOI:10.1039/d0ob00205d
日期:——
transform aryl diazoniumsalts into aryl radicals. Experimental and computational studies show that Hantzsch esters transfer hydride to aryl diazonium species, and that oxygen initiates radical fragmentation of the diazene intermediate to produce aryl radicals. The operational simplicity of this addition-fragmentation process for the generation of aryl radicals, by a polar-radical crossover mechanism, has been
Preparations of Furans from<b><i>α</i></b>-Bromo Ketones and Enol Ethers Catalyzed by a Rhenium(I) Nitrogen Complex
作者:Yuji Koga、Hiroyuki Kusama、Koichi Narasaka
DOI:10.1246/bcsj.71.475
日期:1998.2
By the catalytic use of a rhenium(I) nitrogencomplex, [ReCl(N2)(PMe2Ph)4], α-keto radicals are generated from α-bromo ketones and react with vinyl ethers and silylenolethers intermolecularly. Various substituted furans, including tetrasubstituted furans such as furoguaiacin, are prepared by this method.
Brønsted acid-catalysed desilylative heterocyclisation to form substituted furans
作者:Emily G. Babcock、Md. Shafiqur Rahman、James E. Taylor
DOI:10.1039/d2ob01828d
日期:——
Heterocyclisation of tert-butyldimethylsilyl (TBS) protected γ-hydroxy-α,β-unsaturated ketones catalysed by para-toluenesulfonic acid (p-TSA) to form substituted furans is reported. The reaction proceeds undermildconditions at room temperature in methanol to give a range of furan products (21 examples, up to 98% yield). Mechanistic experiments suggest the reaction proceeds via in situ deprotection