Iodine catalyzed one-pot five-component reactions for direct synthesis of densely functionalized piperidines

A simple and convenient one-pot multicomponent reaction (MCR) has been developed for the synthesis of highly functionalized piperidines catalyzed by molecular iodine. This strategy demonstrated five-component reactions of 1,3-dicarbonyl compounds, amines and aromatic aldehydes in methanol using 10 mol % of iodine at room temperature. This methodology provides an alternative approach for easy access of highly and fully substituted piperidines in moderate to good yields using three readily available starting materials. Notably, this method is mild, cheap, straight forward, applicable to broad range of substrates and environmentally friendly as compared to the existing methods. Synthetic and mechanistic studies are presented here.