An organocatalytic method for the synthesis of some novel xanthene derivatives by the intramolecular Friedel–Crafts reaction

An efficient organocatalytic method for the synthesis of new substituted 9-arylxanthenes ( 2a–2u ) starting from diarylcarbinol compounds with an arenoxy group ( 1a–1u ) has been developed using the intramolecular Friedel–Crafts reaction. The substrates were prepared in two steps by Ullmann-type coupling and then Grignard reaction. Some organic Brønsted acids were studied as catalysts ( 3a–3g ) in the intramolecular Friedel–Crafts alkylation reaction for the first time. N -triflylphosphoramide ( 3g ) provided the synthesis of some novel substituted 9-arylxanthenes with excellent yields at room temperature within 15 minutes.