Recyclable dirhodium catalysts embedded in nanoporous surface-functionalized organosilica hosts for carbenoid-mediated cyclopropanation reactions

Recyclable and efficient heterogeneous catalysts have been prepared by embedding dirhodium(II,II) core carboxylate complexes into the amine-functionalized nanosized channels of a mesoporous silica host, amine-SBA-15. Two alternative synthetic procedures for the preparation of the catalysts have been developed and adapted for the immobilization of dirhodium complexes of variable Lewis acidity. The catalytic activity of the resulting solid materials has been evaluated in model cyclopropanation reactions of styrene at variable reaction conditions (reaction substrate, temperature, time, and solvent). Importantly, the designed catalysts, which can be readily recovered and reused, display the reactivity and selectivity profiles exceeding or comparable to their homogeneous dirhodium(II) counterparts.