AbstractAn operationally simple and efficient protocol for squaric acidcatalyzed synthesis of N-substituted pyrroles via the reaction of 2,5-dimethoxytetrahydrofuran and 2,5-hexandione with aryl amines in green reaction media (water, deep eutectic solvent, and polyethylene glycol) under ultrasound irradiation or thermal conditions in good to excellent yields has been developed. Graphical abstract
Reversion of Paal-Knorr Synthesis: A New Strategy for Ring-Opening and N-Substituent Change in 1<i>H</i>-Pyrroles
作者:Francisco Hidalgo、Rosario Zamora
DOI:10.1055/s-2006-941559
日期:2006.6
1H-Pyrroles were converted into 1,4-dicarbonyl compounds, and then into 1H-pyrroles with a different N-substituent by heating at 110 °C under nitrogen in 0.3 M sodium citrate buffer, pH 3, and in the presence of alkyl or aryl amines. The new pyrroles were obtained in low to very high yields depending upon the pH, the reaction time, the initial pyrrole and amine involved, and the proportion between both reagents.
Sulfamic acid as efficient and reusable catalytic system for the synthesis of pyrrole, furan, and thiophene derivatives
作者:Haitang Luo、Yuru Kang、Qi Li、Liming Yang
DOI:10.1002/hc.20389
日期:2008.3
Sulfamic acid has been utilized for the first time as an efficient and reusable catalytic system for the synthesis of heteroaromatics such as pyrrole, furan, and thiophene derivatives from 1,4-diketones. This new procedure offers significant improvements in the reaction rates and yields in a shorter reaction time and a lower reaction temperature contrasted with the reported results. The recovered catalyst
An approach to the Paal–Knorr pyrroles synthesis catalyzed by Sc(OTf)3 under solvent-free conditions
作者:Jiuxi Chen、Huayue Wu、Zhiguo Zheng、Can Jin、Xingxian Zhang、Weike Su
DOI:10.1016/j.tetlet.2006.05.085
日期:2006.7
A facile synthesis of N-substitutedpyrroles by the Paal–Knorrcondensation has been accomplished using a simple procedure. Among different metal triflates screened, 1 mol % Sc(OTf)3 efficiently promoted the reaction to give excellent yield (89–98%) under mild reaction conditions. Additionally, Sc(OTf)3 could be recovered easily after the reactions and reused without evident loss in activity.
The synthesis of pyrroles by reaction of hexane-2,5-dione with primary amines has been shown to occur in less than 2 minutes under microwave activation.