Stereoselective synthesis of spirocyclic pyrrolidines/pyrrolizidines/pyrrolothiazolidines using l-proline functionalized manganese ferrite nanorods as a novel heterogeneous catalyst

Abstract

An efficient, green, one-pot, and three-component protocol has been reported for the stereoselective synthesis of a new class of spiro thiazolidines. A series of spiro-heterocycle derivatives were produced stereoselectively in high yields by the reaction of 5-arylidene thiazolidine-2,4-diones, isatin, and secondary amino acids in the presence of MnCoCuFe₂O₄@L-proline (MCCFe₂O₄@L-proline) magnetic nanorods as a novel nanocatalyst. The synthesized catalyst was fully characterized for thermal stability, magnetic properties, and other physicochemical properties via numerous techniques. It was applied as an efficient and reusable catalyst for the synthesis of endo-isomers of spirocyclic pyrrolidine/pyrrolizidine/pyrrolothiazolidine derivatives in high yield. The regioselectivity and stereochemistry of these heterocyclic spiro-compounds were established by ¹H, ¹³C, HMBC, HSQC, and COSY NMR spectroscopy techniques. The main attractive characteristics of the presented protocol are high yield, high level of diastereoselectivity, and easy recovery of catalyst without significant loss of its catalytic activity.