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Acid‐Catalysed Rearrangements of α‐Vinylcyclobutanones
Author(s) -
Jackson David A.,
Rey Max,
Dreiding André S.
Publication year - 1985
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19850680217
Subject(s) - chemistry , cyclopentenone , cyclopropane , cyclobutanone , derivative (finance) , bicyclic molecule , medicinal chemistry , stereochemistry , organic chemistry , ring (chemistry) , financial economics , economics
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 .