A Rapid, Economical Purification Method for Novel Mannich Base-Derived Imidazo [1,2-a] pyridine Using Preparative Thin-Layer Chromatography

This work reports the preparation of a series of novel Mannich bases derived from the imidazo[1,2-a]pyridine scaffold. The development of a simple new purification strategy using preparative Thin-Layer Chromatography (TLC) is described. This technique is highly efficient, economical, and readily accessible in standard laboratory settings. The crude product was dissolved in a minimal amount of dichloromethane and applied as a uniform band onto preparative silica gel TLC plates (silica gel 60 F254, 20 × 20 cm, 2 mm thickness). Plate development was conducted using an optimized solvent system, typically ethyl acetate/hexane (1:1, v/v). Following development, the plates were dried and examined under UV light at 254 nm. The target molecules were obtained in high yields (81-95) through a one-pot threecomponent Mannich reaction. Due to the limited availability of conventional chromatographic equipment during the COVID-19 period, an alternative purification protocol based on preparative TLC was optimized. The structures of all products were confirmed by 1H NMR, 13C NMR, IR, and UV spectroscopy. The proposed method offers a rapid, low- cost and solvent-saving approach for the purification of small-scale heterocyclic libraries.