Acetyl oxime/azirine 1, 3-dipole and strategy for the regioselective synthesis of polysubstituted pyrroles via [3 + 2] cycloaddition with alkyne utilizing Fe2O3@cellulose catalyst

Fe2O3@cellulose catalyzed regioselective [3 + 2] cycloaddition of acetyl oxime with alkynes via 2H‑azirines intermediate generated in situ in an aqueous ethanolic medium is described. The methodology is highly regioselective for the synthesis of polysubstituted pyrroles in good yield. The products were isolated without using any column chromatography. The catalyst could be separated by using an external magnet and the recovered catalyst could be reused for four consecutive cycles with negligible loss in its catalytic activity. Broad functional group tolerance, mild reaction condition, easily accessible starting materials, utilization of green reaction medium, recyclability of the catalyst up to further reaction without affecting the outcome of the reaction, gram-scale synthesis are some of the salient features of this strategy.