Application of Tridentate Bis(oxazoline) Ligands in Catalytic Asymmetric Nozaki–Hiyama Allylation and Crotylation: An Example of High Enantioselection with a Non-Symmetric Bis(oxazoline) Ligand

✍ Scribed by Helen A. McManus; Pier Giorgio Cozzi; Patrick J. Guiry

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 115 KB
• Volume: 348
• Category: Article
• ISSN: 1615-4150
• DOI: 10.1002/adsc.200505332

✦ Synopsis

Abstract

A series of both symmetric and non‐symmetric bis(oxazoline) ligands was applied in the Nozaki–Hiyama allylation and crotylation of benzaldehyde. It was found that both the magnitude and sense of the asymmetric induction depended strongly on the nature and combination of the oxazoline substituents. For both reactions, the non‐symmetric tert‐butyl/benzyl‐substituted ligand proved to be the optimal ligand and was applied successfully in the allylation and crotylation of a range of aryl and aliphatic aldehydes. The enantioselectivities obtained in allylation were up to 91% ee and in crotylation up to 92% with typical syn:anti ratios of up to 80 : 20.