Synthesis of 9,9-bis(4-hydroxyphenyl) fluorene catalyzed by bifunctional ionic liquids†
Through structural design, a series of bifunctional ionic liquids (BFILs) containing sulfonic acid (–SO3H) and sulfhydryl groups (–SH) were synthesized and characterized by NMR and MS. The acidity of these BFILs was measured by the Hammett acidity (H0) and the effective sulfhydryl molar content of BFILs was determined by Ellman's method. Moreover, BFIL's catalytic properties in the condensation reaction of 9-fluorenone and phenol were studied. BFIL catalyst 6c can achieve nearly 100% conversion of 9-fluorenone with a high selectivity of 9,9-bis(4-hydroxyphenyl) fluorene (95.2%).