The Belluš–Claisen Rearrangement

✍ Scribed by Jozef Gonda

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 263 KB
• Volume: 43
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/anie.200301718

✦ Synopsis

Abstract

Among the reactions available to synthetic chemists for the construction of new CC bonds, the Claisen rearrangement is one of the most powerful, elegant, and well‐characterized methods. A genuinely new variant, the Belluš–Claisen rearrangement came to light a quarter of a century ago: The reaction of an allylic ether, thioether, or amine with a ketene leads through a [3,3] sigmatropic bond reorganization of a zwitterionic intermediate to an E unsaturated ester, thioester, or amide. When applied to cyclic allylic substrates, a ring‐enlargement by four carbon atoms in one step provides medium‐ring unsaturated E‐configured lactones, thiolactones, and lactams. The scope of the Belluš–Claisen rearrangement and the optimum reaction conditions will be discussed in this Minireview.