Synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes promoted by Mg(HSO4)2

14-Aryl or alkyl-14H-dibenzo[a,j]xanthenes were prepared by condensation of 2-naphthol and aldehydes in the presence of Mg(HSO4)2 as an efficient, cheap, readily available and eco-friendly catalyst. This procedure has the advantages of high yields, easy work-up, short reaction times, and green conditions.