A new method for recycling asymmetric catalysts via formation of charge transfer complexes.
[reaction: see text]. A new concept for recycling asymmetric bis(oxazoline)-type catalysts is reported. The formation of charge-transfer complexes between the chiral ligand and trinitrofluorenone and their subsequent precipitation and reuse by addition of new substrate solutions is described. The efficiency of this procedure is demonstrated in a Diels-Alder reaction to reach the expected endo product as major isomer (up to 97% de and 94% ee): the catalyst was used up to 12 times without loss of either activity or selectivity.
Chollet
Guillaume
G
Laboratoire de Catalyse Moléculaire, Institut de Chimie Moléculaire et des Matériaux d'Orsay, Université Paris Sud, Bât 420, 91405 Orsay, France.
Rodriguez
Fernand
F
Schulz
Emmanuelle
E