Rearrangement reactions of bicyclic systems. Part IV. Acid-catalysed rearrangements of 5,6,7,8-tetrafluoro-1,4-dihydro-1-methoxy-3,9-dimethyl-1,4-ethenonaphthalene (1-methoxy-3,5-dimethyltetrafluorobenzobarrelene)

Abstract

The rearrangement of the title compound in trifluoroacetic acid was shown to be directed by the methyl groups, giving 5,6,7,8-tetrafluoro-3,4-dihydro-4,10-dimethyl-1,4-ethenonaphthalen-2(1H)-one (5). On the other hand the title compound gave the lactone 7,8,9,10-tetrafluoro-1,2,5,6-tetrahydro-2,6-dimethyl-2,6-methano-3-benzoxocin-4-one (4) in 98% sulphuric acid, and in 70% sulphuric acid 5,6,7,8-tetrafluoro-3-methyl-1-naphthylacetone (6) was an important product. The mechanisms operating have been studied by using deuteriated acids; the results establish that none of the protonation steps occurs stereospecifically.