4-dodecylbenzenesulfonic acid (dbsa) as an efficient and recyclable catalyst for synthesis of 14-aryl- and 14-alkyl-14-h-dibenzo [a,j]xanthenes under solvent-free conditions

14-aryl- and 14-alkyl-14-h-dibenzo [a,j]xanthenes are prepared from the reaction of aromatic- and aliphaticaldehydes with β-naphthol in the presence of catalytic amounts of 4-dodecylbenzenesulfonic acid(dbsa) as asurfactant-type brønsted acid catalyst in toluene and under solvent-free conditions in excellent yields and shortreaction times. the catalyst was recovered and reused for five successive times without considerable loss in itsactivity.