the viability of a wide range of crystalline aromatic and aliphatic carboxylic acids as organocatalysts has been investigated for solvent-free Paal–Knorr pyrrole synthesisundermicrowave activation. Among these potential catalysts, crystalline salicylic acid proved to be a remarkable catalyst because its efficiency remained high even under low microwave power irradiation or a shorter reaction time
摘要 在这项研究中,已经研究了微波活化下无溶剂的Paal-Knorr吡咯合成中各种结晶性芳族和脂肪族羧酸作为有机催化剂的可行性。在这些潜在的催化剂中,结晶水杨酸被证明是出色的催化剂,因为即使在低微波功率辐照下或模型反应的反应时间较短的情况下,其效率仍然很高。水杨酸出色的催化活性使Paal–Knorr环缩合的周转频率高达1472 h -1,这在无金属均相催化的情况下是独一无二的。这种有机催化剂的吸引人的特点是它有助于超快速的吡咯合成,并且没有金属污染的风险。 图形摘要 概要:引入了一种绿色快速的方法,该方法通过水杨酸作为催化剂(固态)与微波的组合来合成2,5-二甲基吡咯。
Naturally occurring organic acids for organocatalytic synthesis of pyrroles via Paal–Knorr reaction
In this study, common naturallyoccurring organic acids, namely oxalic, malonic, succinic, tartaric and citric acid (as safe, inexpensive, and biodegradable organocatalysts), have been employed for Paal–Knorr pyrrole synthesis. The organocatalyzed reaction proved to be effective in ethanol at 60 °C. However, the reaction rate is mainly dominated by the nature and position of functional groups on the
在这项研究中,常见的天然有机酸,即草酸、丙二酸、琥珀酸、酒石酸和柠檬酸(作为安全、廉价和可生物降解的有机催化剂)已被用于 Paal-Knorr 吡咯合成。证明有机催化反应在 60 °C 下在乙醇中是有效的。然而,反应速率主要取决于官能团在底物芳环上的性质和位置。这种无金属工艺可以容忍一系列官能团,应该被视为制药行业的一项资产,因为在吡咯支架的合成过程中不会发生金属污染。
Microwave-induced calcium(II) chloride-catalyzed Paal–Knorr pyrrole synthesis: a safe, expeditious, and sustainable protocol
alkaline-earth (Ca, Mg, Sr, Ba) chlorides, calcium(II) chloride was found to be a cost-effective Lewis acid catalyst for solvent-free synthesis of pyrroles from primary aromatic and aliphaticamines under open-vessel focused microwave irradiation. The salient features of this environmentally benign method are high to quantitative conversion, short reaction time, safe and clean reaction profile, possibility of
(2021). Imidazolium Triflate IonicLiquid Improves the Activity of ZnCl2 in the Synthesis of Pyrroles and Ketones. Organic Preparations and Procedures International: Vol. 53, No. 2, pp. 157-165.
A green and efficient method for the synthesis of pyrroles using a deep eutectic solvent ([CholineCl][ZnCl<sub>2</sub>]<sub>3</sub>) under solvent-free sonication
An efficient deep eutectic solvent-based synthesis of pyrroles under ultrasound irradiation has been developed to provide a significant improvement of the yield up to 99% in a short reaction time. The synthesis of pyrroles is highly atom-economical, producing water as the sole byproduct. In addition, [CholineCl][ZnCl2]3 is easily synthesized from commercially available choline chloride and zinc chloride