Silica-supported bismuth(III) chloride as a new recyclable heterogeneous catalyst for the Paal–Knorr pyrrole synthesis

Silica-supported bismuth(III) chloride (BiCl3/SiO2) acts as as a highly efficient heterogeneous Lewis acid catalyst for the Paal–Knorr pyrrole synthesis in hexane at room temperature. The catalyst exhibited remarkable reusable activity and higher catalytic performance than homogeneous BiCl3. A plausible mechanism for the catalytic action of BiCl3/SiO2 has been introduced.

Graphical abstractSilica-supported bismuth(III) chloride (BiCl3/SiO2) acts as as a highly efficient heterogeneous Lewis acid catalyst for the Paal–Knorr pyrrole synthesis in hexane at room temperature. The catalyst exhibited remarkable reusable activity and higher catalytic performance than homogeneous BiCl3. A plausible mechanism for the catalytic action of BiCl3/SiO2 has been introduced.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Immobilization of Bi(III) ion onto silica surface. ► Formation of O–BiOCl as stable Lewis acid sites. ► Heterogeneous pyrrole synthesis applicable to a wide range of aniline substrates. ► Low catalyst loading with high activity. ► Catalyst recycled several times due to negligible leaching of the metal.