Hydroxyamide-catalyzed enantioselective addition of diethylzinc to benzaldehyde in the absence of titanium

Three camphor-based tertiary-amido isoborneols have been obtained from ketopinic acid and tested as ligands for the hydroxy-amide-catalyzed enantioselective addition of diethylzinc to benzaldehyde in the absence of Ti(O-i-Pr)(4). The results obtained have been compared with previous results published by Oppolzer. The new chiral ligands showed effective asymmetric activity in the absence of titanium (up to 98% yield and 90% ee). It is demonstrated that non-bulky dialkylamino groups are necessary for obtaining high chemical yields, whereas the C-2 symmetry is necessary to reach a good enantioselection level. (c) 2008 Elsevier Ltd. All rights reserved.