Self-Supported BINOL-Derived Phosphoric Acid Based on a Chiral Carbazolic Porous Framework.

Abstract

The facile synthesis of a porous heterogeneous BINOL-derived chiral phosphoric acid BiCz-POF-1 using the mild, FeCl3-promoted oxidative polymerization is reported. For the first time, carbazole is introduced at the 3,3'-positions of the chiral BINOL-derived phosphoric acid to (1) offer steric hindrance for achieving a high enantioselectivity and (2) serve as a cross-linker for the construction of the porous solid catalyst. BiCz-POF-1 exhibits remarkable catalytic activity and enantioselectivity toward transfer hydrogenation of 1,4-benzoxazine, 1,4-benzoxazinone, and 2-phenylquinolone. Combined with its facile synthesis and excellent recyclability, BiCz-POF-1 represents a new class of heterogeneous chiral phosphoric acid that has wide potential utility in enantioselective organocatalysis.