Catalytic Asymmetric Bromination and Chlorination of β-Ketoesters

✍ Scribed by Mauro Marigo; Nagaswami Kumaragurubaran; Karl Anker Jørgensen

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 132 KB
• Volume: 10
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200305759

✦ Synopsis

Abstract

The first general catalytic asymmetric bromination and chlorination of β‐ketoesters has been developed. The reactions proceed for both acyclic and cyclic β‐ketoesters catalyzed by chiral bisoxazolinecopper(II) complexes giving the corresponding optically active α‐bromo‐ and α‐chloro‐β‐ketoesters in high yields and moderate to good enantioselectivities. For the optically active chlorinated products the isolated yields are in the range of 88–99 % and the enantiomeric excesses up to 77 % ee, while the optically active brominated adducts are formed in 70–99 % isolated yield and up to 82 % ee. Based on the absolute configuration of the optically active products, the face selectivity for the catalytic enantioselective halogenation is discussed based on a bidentate coordination of the β‐ketoester to the chiral catalyst and a X‐ray structure of chiral α,γ‐diketoesterenolatebisoxazolinecopper(II) complex.