Under solvent-free high-speed ball milling, an I\(_{2}\)-promoted condensation/cyclization of easily available methyl ketones or 1,3-dicarbonyl compounds with 2-aminopyridines has been developed, which allows the quick assembly of 2,3-substituted imidazo[1,2-a]pyridines (IPs) with broad molecular diversity, including the antiulcer drug zolimidine. The advantages of high yields, good functional group compatibility, short reaction time (within 90 min), free use of heating, solvent and metal, employment of cheap starting materials, and simple work-up procedure make this protocol a very efficient alternative to traditional synthesis of IPs.

Promoted by KOH under ball milling, anilines were efficiently transformed into isothiocyanates (in presence of 5.0 equiv. CS2) or symmetrical thioureas (in presence of 1.0 equiv. CS2), without using any other harsh or toxic decomposition reagent. Some in situ generated isothiocyanates can directly “click” with other amines to afford unsymmetrical thioureas.