1,1′-Bi-2-naphthol-fluoroacetyl compounds in fluorescent recognition of amines

Abstract

Several 1,1′-bi-2-naphthol (BINOL) derivatives containing fluoroacetyl functions were synthesized, which included (S)-4 with two difluoroacetyl groups at the 3,3′-positions of BINOL, (R)-7 with two trifluoroacetyl groups at the 3,3′-positions of a partially hydrogenated BINOL, and (S)-12 containing two trifluoroacetyl groups at the 6,6′-positions. Compounds (S)-4 and (R)-7 were nonfluorescent but (S)-12 gave intense fluorescence. This indicates that intramolecular hydrogen bondings between the BINOL hydroxyl groups and the 3,3′-dicarbonyl groups of (S)-4 and (R)-7 could have effectively quenched their fluorescence. The fluorescence responses of these compounds towards a variety of amines were studied. It was found that (S)-4 showed greatly enhanced fluorescence in the presence of diamines and also highly enantioselective fluorescent response toward a chiral diamine. However, monoamines could not turn on the fluorescence of this compound. Compound (S)-12 showed greatly increased fluorescence quenching by amines in comparison with BINOL.