Diastereoselective arylation of L-proline derivatives at the 5-position

Diastereoselective introduction of nucleophiles into L-proline derivatives at the 5-position was achieved with suitable selection of N-protecting group. N-Methoxycarbonylated or benzyloxycarbonylated L-proline derivatives reacted with arene to give cis-arylated products. On the other hand, N-benzoylated L-proline derivative preferentially gave trans-arylated product, which could be easily transformed into optically active C-2-symmetrical pyrrolidine derivative. Such derivative 5 worked well as an organic activator in the asymmetric reduction of aromatic imines by Cl3SiH. (C) 2008 Elsevier Ltd. All rights reserved.