Efficient two-step synthesis of 9-aryl-6-hydroxy-3H-xanthen-3-one fluorophores

[GRAPHIC] A two-step method for the synthesis of 9-aryl-6-hydroxy-3Hxanthen-3-one fluorophores involving condensation of aryl aldehydes and fluororesorcinol is shown to proceed through a triarylmethane intermediate. The condensation is complicated by retro-Friedel-Crafts reactions which can be minimized by controlling the amount of acid. The xanthenone ring system is prepared by a final oxidative cyclization with DDQ.