CuFe2O4@SO3H: A Mild, Efficient and Reusable Heterogeneous Catalyst for the Synthesis of Highly Functionalized Piperidines

Multi-component reactions (MCRs) are special types of synthetically useful organic reactionsin which three or more different starting materials react to give a final product in a one-potprocedure. MCRs are becoming powerful tools in the modern synthesis chemistry due to theirefficiency, atom economy, and convenience in the construction of multiple new bonds in onepotprocesses, which played powerful roles in approaching complex structures and promotingthe ‘green chemistry’ [1, 2]. The piperidines and its analogues are important heterocycles thatare present in many naturally occurring alkaloids, biologically active synthetic molecules andorganic fine chemicals. Some of them also act as pharmaceutical agents. Compounds containingpiperidine structural motif exhibit anti-hypertensive, antibacterial, antimalarial, anticonvulsantand anti-inflammatory activities. Thus, the synthesis of highly substituted piperidineshas gained considerable attention, and number of procedures have been developed using severalapproaches such as tandem cyclopropane ring-opening/Conia-ene cyclization, iminoDiels-Alder reactions, aza-Prins-cyclizations, intramolecular Michael reactions and intramolecularMannich reaction onto iminium ions. The functionalized piperidines have been reportedusing MCRs strategy by employing bromodimethylsulfonium bromide (BDMS), InCl3 andLProline/TFA. However, use of expensive and excess amount of catalysts are some of thedisadvantages of the above mentioned methods. Therefore, there is a need for highly efficient,versatile and eco-friendly synthetic protocol to obtain these valuable compounds in goodyields [3]. We report herein full details of a novel, convenient, and simple procedure to realizea one-pot pseudo five-component reaction of aldehydes, amines, and 1,3-dicarbonyl compounds,catalyzed by CuFe2O4@SO3H, for the preparation of piperidinecompounds in EtOHwith high yields (72-95%) and short times.