Halloysite functionalized with Cu (II) Schiff base complex containing polymer as an efficient catalyst for chemical transformation

Copper Schiff base complex with allyl functionality was prepared and reacted with amino-functionalized halloysite. The resultant compound was then reacted successively with melamine and the as-prepared copper Schiff base complex to furnish a polymeric moiety with multi copper Schiff base complex on the halloysite outer surface. The latter was then characterized by EDS, FTIR, TGA, ICP, TEM, XRD, VSM and elemental mapping analysis and subsequently applied as a catalyst for promoting one-pot reaction of aldehydes and dimedone to synthesize xanthene derivatives. The catalyst showed high catalytic activity under mild reaction condition and could be easily recovered and efficiently recycled with low Cu leaching. Notably, this protocol could be generalized to various aldehydes with different electron densities.