Chollet Guillaume, Rodriguez Fernand, Schulz Emmanuelle
Laboratoire de Catalyse Moléculaire, Institut de Chimie Moléculaire et des Matériaux d'Orsay, Université Paris Sud, Bât 420, 91405 Orsay, France.
Org Lett. 2006 Feb 2;8(3):539-42. doi: 10.1021/ol053036a.
[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.
