Catalysis by an ionic liquid: Highly efficient solvent-free synthesis of aryl-14H-dibenzo[a.j]xanthenes by molten tetrabutylammonium bromide under conventional and microwave heating

A Rapid and Green Procedure for the Synthesis of 5- Arylidene Rhodanine Derivatives

“…When the reaction was completed, the reaction mixture was recrystallized from ethanol. The mother liquor was evaporated to dryness and the resulting catalyst was reused without any treatment [23]. It was found that the catalyst could be reused at least four times without significant loss of activity.…”

Green catalytic synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes using recyclable mesoporous zirconia modified with tungstophosphoric acid

“…One of the best reported protocols for the synthesis of 14-aryl-14H-dibenzo-[a,j]xanthenes involves the mixing of 2-naphthol with aldehydes in the presence of a catalyst (30) (35), silica sulfuric acid (36), Dowex-50W (37), ionic liquid (38), bulk (39), and silica-supported (40) HPAs.…”

The Beneficial Sinergy of MW Irradiation and Ionic Liquids in Catalysis of Organic Reactions

“…Molten tetrabutylammonium bromide, Bu 4 NBr, resulted an efficient and recyclable catalyst for the MCR of β-naphthol and aromatic aldehydes that produced dibenzoxanthenes [145] (Scheme 59). Compared to other catalysts (Brønsted or Lewis acids), Bu 4 NBr was one of the most efficient, giving the same yield than those reported for p-toluenesulfonic or sulfamic acids (90-94%).…”

“…With conventional heating, in the same IL, the reaction took more than 2 h to complete; however, it is not clear whether IL is really a catalyst, because no blank experiment was reported. Molten tetrabutylammonium bromide, Bu4NBr, resulted an efficient and recyclable catalyst for the MCR of β-naphthol and aromatic aldehydes that produced dibenzoxanthenes [145] (Scheme 59). Compared to other catalysts (Brønsted or Lewis acids), Bu4NBr was one of the most efficient, giving A functional ionic liquid, 1-(2-aminoethyl)-3-methylimidazolium hexafluophosphate, catalyzed the synthesis of pyrans with MW heating [143] (Scheme 57).…”