Supported sulfonic acids: reusable catalysts for more sustainable oxidative coupling of xanthene-like compounds with nucleophiles

The oxidative coupling of xanthene and thioxanthene with methylene active compounds can be achieved in good yields (55–92%) and selectivities (83–99%) by using the commercial catalyst Amberlyst-15, an inexpensive, safe to handle and easy to recycle sulfonic resin. The method is completely metal-free and shows a very high atom economy (99.2%).