Synthesis, resolution and crystal structures of two enantiomeric rhodamine derivatives

Abstract

The title molecule, rac-6′-bromo-3′-diethylamino-3H-spiro[2-benzofuran-1,9′-xanthen]-3-one, C24H20BrNO3, was synthesized and the two enantiomers which formed were separated. The structures of all three compounds were determined and compared with those of a variety of related derivatives. A notable feature is the fold of the xanthene portion which ranges from 15.15 (13)° in the racemate to 2.42 (2)° in one molecule of the R enantiomer with that for the S enantiomer having an intermediate value. The differences are attributed to the number and severity of intermolecular interactions which include C—H...O hydrogen bonds, C—H...π(ring) and, in the S enantiomer, a π-stacking interaction between the carbonyl group and an aromatic ring.

Keywords

• crystal structure
• rhodamine
• xanthene
• hydrogen bond
• chiral sensors