Enantioselective fluorescent recognition of mandelic acid by unsymmetrical salalen and salan sensors

As sensors with multiple chiral centers, salalen 1 and salan 2 composed of trans-cyclohexane-1,2-diamine (trans-DACH) and 1,1'-bi-2-naphthol (BINOL) units were designed and synthesized. Fluorescent recognition studies of resulting sensors towards mandelic acid (MA) reveal that salan 2a containing (R)-BINOL and (R,R)-DACH exhibits highly sensitive and enantioselective response towards MA. The relationship between the chirality combination and the enantioselectivity is discussed. Based on the studies of concentration and solvent effect on the recognition process of 2a, it was found that the sensitivity and enantioselectivity could be enhanced via changing the concentration of sensors or altering the polarity of solvents. To explain why higher enantioselectivity can be achieved in moderate polar solvent other than in nonpolar or polar solvent, a solvent-guest competition mechanism, which may shed a light on the enhancement of the enantioselectivity of chiral recognition and noncovalent asymmetric catalysis, has been proposed and validated.     

Catalytic enantioselective aryl transfer to aldehydes using chiral 2,2'-bispyrrolidine-based salan ligands

Chiral C?-symmetric diamines have emerged as versatile auxiliaries or ligands in numerous asymmetric transformations. Chiral 2,2'-bispyrrolidine-based salan ligands were prepared and applied to the asymmetric aryl transfer to aldehydes with arylboronic acids as the source of transferable aryl groups. The corresponding diarylmethanols were obtained in high yields with moderate to good enantioselectivitives of up to 83% ee.     

L-Proline promoted fluorescent sensor for Mg2+ detection in a multicomponent sensory system

Mg(2+) can lead to the fluorescence enhancement of a dye molecule as high as 47.3-fold while L-proline acts as a promoter in this multicomponent sensory system. The fluorescence color could be easily detected by the naked eye under a UV-lamp.     

The design and synthesis of β‐trifluoromethylenol phosphates as potential insecticides

A new group of compounds, β‐trifluoromethylenol phosphates [(RO)₂P(O)OCRCHCF₃], has been designed and prepared by several methods. Some of them showed good insecticidal activities. In the molecular structure, the designed leaving group can rearrange to a powerful electrophilic agent, β,β‐difluorovinyl ketone, which would be a potential enzyme inhibitor. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:304–308, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10147