A rapid and efficient method for the synthesis of 14H-dibenzo[α.j] xanthenes, aryl-5H-dibenzo [b.i]xanthene-5,7,12,14-(13H)-tetraone and 1,8-dioxo-octahydroxanthenes by acidic ionic liquid

Various xanthenes have been synthesized by the condensation of β-naphthol, 2-hydroxynaphthalene-1,4-dione or dimedone with various aldehydes in the presence of trifluoroacetic acid as catalyst in 1,1,3,3-N,N,N′,N′-tetramethylguanidinium trifluoroacetate (TMGT) ionic liquid within 1 h at 75 °C.