An efficient and reusable ionic liquid catalyst for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes under solvent-free conditions

Abstract

In this work, it was found that acidic protic ionic liquid N,N-dimethylaminoethanol hydrosulfate ([DMEA][HSO₄]) was an efficient and reusable catalyst for the one-pot synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes under solvent-free conditions. This ionic liquid is very cheap, air and water stable, and can be easily recovered and reused for at least six cycles. The catalytic system described here is a green protocol since in the one-pot synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes, the yield of the target compounds is excellent, operation and work-up procedures are simple, and no volatile organic solvents have been used. It is suggested that the synergetic effect of the cation and the anion of this ionic liquid is the main reason for the high catalytic activity and high chemo-selectivity. Scale-up experiments also suggest that this catalytic system has potential in industrial application.