Synthesis of chiral Mn(III)-meso-tetrakis-[2.2]-p-cyclophanyl-porphyrin: a new catalyst for enantioselective epoxidation

✍ Scribed by Stefano Banfi; Amedea Manfredi; Fernando Montanari; Gianluca Pozzi; Silvio Quici

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 801 KB
• Volume: 113
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/s1381-1169(96)00048-9

✦ Synopsis

The synthesis of Mn(III)-complexes of new chiral porphyrins la and lb prepared by condensation of enantiomerically pure [2.2]-p-cyclophane-4-carbaldehyde and pyrrole are described. These compounds were used as catalysts in epoxidation reactions of prochiral alkenes, carried out in the presence of aqueous NaOCl at pH = 10.0 as oxygen donor and small amounts of 4-tert-butylpyridine as axial ligand, in CH,Cl,/H,O two-phase conditions at 0°C. Results indicate a satisfactory catalytic efficiency (up to 700 overall turnovers), with enantiomeric excesses in the range 22-31%.