Acid-Catalysed Rearrangements of α-Vinylcyclobutanones

✍ Scribed by David A. Jackson; Max Rey; André S. Dreiding

• Publisher: John Wiley and Sons
• Year: 1985
• Tongue: German
• Weight: 756 KB
• Volume: 68
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19850680217

✦ Synopsis

Abstract

The BF~3~ · Et~2~O‐ and the CH~3~SO~3~H‐catalysed rearrangements of 10 α‐vinylcyclobutanones have been examined. With little acid, the β,β‐dialkyl derivatives 1 were transformed into linear dienones 2 and 3; with more acid, they were converted into cyclopentenones 4 by Nazarov cyclisation of initially formed 2/3. The β‐monoalkyl (including the β,γ‐dialkyl) derivatives 7 rearranged only with a high acid concentration to afford the cyclopentenones 8 by 1,2‐acyl migration. In the case of 7a, the cyclopentenone 8a was accompanied by the unexpected constitutional isomer 9a, which is explained by a reversible interconversion of the cyclobutanone 7a with its isomer 19 via a cyclopropane intermediate like 18. In the case of the β,β‐dialkyl derivative 5, which contains an α‐isobutenyl (instead of an α‐vinyl) group, the acid‐catalysed rearrangement product was the bicyclo[3. 1. 0]hexanone derivative 6.