Ultrasound-assisted synthesis of pyrroles catalyzed by zirconium chloride under solvent-free conditions

Abstract

A straightforward synthesis of substituted pyrroles using zirconium chloride-catalyzed modified Paal-Knorr method has been accomplished under ultrasound irradiation. Compared to known methods, this new method provides as easy access to various substituted pyrroles in good to excellent yields with short reaction times.

Use of Ultrasound in the Synthesis of Heterocycles of Medicinal Interest

“…Zhang et al [52] also developed a protocol for substituted pyrroles using different catalysts such as FeCl 3 , BiCl 3 , LaCl 3 [53] accessed to a faster and efficient metal-free synthesis of polysubstituted pyrroles (23) in good yields under ultrasound assistance. Starting materials were β-keto esters (19), benzylamines (20), aromatic aldehydes (21), and nitromethane (22) in the presence of amberlyst-15 as a reusable catalyst via a four-component reaction (Scheme 7).…”

Ultrasonics Promoted Synthesis of 5-(Pyrazol-4-yl)-4,5-Dihydropyrazoles Derivatives

“…Compared with traditional methods, this method is more convenient and easily controlled. A large number of organic reactions can be carried out in a higher yield shorter reaction time and milder conditions under ultrasound [48][49][50][51][52].…”

Novel Bifunctional Mesoporous Catalysts Based on Preyssler Heteropolyacids for Green Pyrrole Derivative Synthesis

“…Mechanically, this synthetic process is simple, but it has a high versatility that depends on the type of carbonyl and amine used. This allows for a wide range of modifications and improvements, from the use of different types of Lewis acid catalysts and biodegradable catalysts [17], through unusual solvents such as ionic liquids [18], and to the use of activation techniques such as microwaves (MW) [19] and ultrasounds (US) [20]. Catalytic processes using heteropolyacids (HPAs) as solid acid catalysts have many advantages over catalysis using liquid acids.…”