Dehydrobromination of αα-dibromotetrahydrobenzocyclohepten-5-ones: a convenient synthesis of benzocyclohepten-5-ones
- 1 January 1969
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society C: Organic
- No. 20,p. 2656-2661
- https://doi.org/10.1039/j39690002656
Abstract
Reaction with Lithium chloride in boiling dimethylformamide has been shown to give high yields of benzocyclohepten-5-ones (9–11) from 6,6-dibromo-6,7,8,9-tetrahydrobenzocyclohepten-5-ones (6–8). Similar eliminations occur from 6,9-dibromo-6,7,8,9-tetrahydrobenzocyclohepten-5-ones (12) and (14). The mechanism of the elimination has been investigated by preparation of possible intermediates, an x-bromo-1,2,2a,7a-tetrahydrocyclobut[a]inden-7-one (22) or (23) and 6-bromo-8,9-dihydrobenzocyclohepten-5-one (28). The available evidence favours an acid-catalysed double bond isomerisation.Keywords
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