Mechanistic Aspects of the Annelation Reactions of Benzocyclobutenedione Monoketals with Vinyllithium Reagents

Article abstract of DOI:10.1021/jo00184a026

The mechanism of the annelation reaction of vinyllithium reagents with benzocyclobutenedione monoketals has been investigated.The results of these studies strongly support a mechanism involving addition of the organolithium reagent to form the lithium salt of a benzocyclobutenol followed by ring opening and cyclization to produce the tricyclic product.This reaction was examined with benzocyclobutenone and with the ethylene glycol and ethanedithiol monoketals of benzocyclobutenedione as the carbonyl components.The lithio derivatives of the bisketal of 2-bromobenzoquinone, the ethylene glycol ketal of α-bromocyclohexenone, and the ethanedithiol ketal of β-bromocyclohexenone were explored as the organometallic components.These studies have established the major mechanistic aspects and the scope of this annelation reaction.