Synthesis of N-(o-amino aryl) pyrroles by Paal-Knorr reaction

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

“…It is noteworthy to mention that the classical reaction for the synthesis of 1g in boiling acetic acid during 7 h gave 23% yield [49], while the same yield was obtained under BiCl 3 /SiO 2 catalyzed reaction conditions at ambient temperature within 1 h.…”

Product Class 4: Benzimidazoles

“…To the resin was added BuOH (6 mL), DMF (5 mL), and ethyl benzimidate hydrochloride (0.53 g, 2.7 mmol), and the mixture was shaken (24±40 h) at 55±90 8C. [80,124,127,128] Moderate yields of 1-substituted benzimidazoles can be obtained by reaction of two molar proportions of formaldehyde with an N-substituted 1,2-diaminoarene in boiling hydrochloric acid. The support-bound benzimidazole product was treated for 3±12 h with TFA/H 2 O (8 mL, 95:5), the solvent collected, and the resin washed with MeOH/CH 2 Cl 2 (3 10 mL).…”