C2-Symmetric bicyclo[3.3.1]nona-2,6-diene and bicyclo[3.3.2]deca-2,6-diene:: new chiral diene ligands based on the 1,5-cyclooctadiene framework

As a new type of C-2-symmetric chiral diene ligands, which coordinate to a metal by their 1,5-cyclooctadiene framework, we prepared 2,6-disubstituted bicyclo[3.3.1]nona-2,6-diene (bnd*) and bicyclo[3.3.2]deca-2,6-diene (bdd*), and examined their catalytic activity and enantioselectivity for rhodium-catalyzed asymmetric 1,4-addition to alpha,beta-unsaturated ketones and 1,2-addition to N-sulfonylimines. High enantioselectivity of the Ph-bnd* ligand was observed in the addition of phenylboroxine to N-tosylimine and N-4-nitrobenzenesulfonylimine of 4-chlorobenzaldehyde to give phenyl(4-chlorophenyl)methylamines in high enantiomeric excess (98-99% ee). (C) 2005 Published by Elsevier Ltd.