Heterogeneous Chiral Covalent Organic Framework for the Enantioselective Epoxidation of Styrenes and Chromenes.

Herein, we report the synthesis of two-dimensional chiral Zn Salen covalent organic frameworks (COFs) () via rapid microwave-promoted condensation of C-symmetric 1,3,5-tris[(5--butyl-3-formyl-4-hydroxyphenyl)ethynyl]benzene with (1,2)-1,2-diaminocyclohexane in excellent yields. The synthesized chiral Zn Salen COF () showed a 454 m g BET surface area with excellent crystallinity and thermal stability. Further, the post-synthetic metal exchange reaction was performed for chiral Zn Salen COFs () with Mn(OAc)·4HO to synthesize chiral Mn Salen COFs () and utilized as an effective heterogeneous catalyst for the enantioselective epoxidation of styrenes and chromenes to afford chiral epoxides up to 72% . Chiral Mn Salen COF () could easily be separated by centrifugation and reused up to four recycles with an observable loss in activity without impairing enantioselectivity.