Multi-Point Molecular Recognition Using Rhodium Porphyrins

Abstract

Rh (III) porphyrins having 2-hydroxynaphthyl or 8-quinolyl groups at the 5-and 15-meso positions exhibit novel bifunctional cooperation of the central Rh (III) ion and the naphthol hydroxyl or quinolyl nitrogen. Thus, ketones undergo a facile enolization as a result of acidbase type cooperation. Amides, on the other hand, undergo a facile acyl substitution in the presence of Ag⁺ ions, as effected by a double Lewis-acid catalysis. The bis (hydroxynaphthyl) system also fixes amino acids and esters via simultaneous two-point interacion involving the Rh (III) -NH₂-coordination and OH-CO₂R hydrogen bonding (R=H or CH₃). Some other examples of related multi-point molecular recognition using modified porphyrin systems are also presented.