Syntheses of benzocyclooctenedione derivatives, cyclopenta[a]indanones and a benzo-anellated tetraquinane via sequential transformations of tricarbonyl(η6-1,2-dioxobenzocyclobutene)chromium(0)

Abstract
Tricarbonyl(η6-1,2-dioxobenzocyclobutene)chromium(0)1 can be converted into benzocyclooctenedione derivatives 3, 7 and 8 as well as fused five-membered ring systems 2, 4 and 6 by addition of vinyl lithium derivatives and following double anionic oxy-Cope rearrangement under very mild reaction conditions (–78 °C); product ratios depend on the method of hydrolysis.
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