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.