Efficient immobilization of sulfonic acid groups in the backbone of aluminoborate-based molecular sieve for the expeditious synthesis of 14-aryl-14H-dibenzo[a,j]xanthene and α-aminonitrile derivatives under solvent-free conditions

Solid acid materials functionalized by sulfonic acid groups (–SO₃H) is receiving a great deal of attention recently because of the effective substitute for conventional liquid mineral acids. In this work, the controllable –SO₃H acidic sites were successfully immobilized in the backbone of aluminoborate-based molecular sieve (PKU1), which were well-confirmed by some physicochemical characterizations. Under solvent-free reaction condition, the as-prepared PKU1-SO₃H solid acids exhibit both high activity and chemical stability for the expeditious synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes and α-aminonitrile derivatives. Eight new crystal structure have been found and were also determined with single crystal X-ray diffraction method. A plausible reaction mechanism was proposed to interpret the key role of –SO₃H active sites on the catalytic synthesis of 14-phenyl-14H-dibenzo[a,j]xanthene derivatives. This work provides an available candidate in the environmentally benign catalysis and a helpful understanding on the reaction mechanism using solid acid catalyst for selective synthesis of some value-added compounds.