title: Stabilized borata-alkene formation: structural features, reactions and the role of the counter cation.
abstract: Dimethylbenzofulvene adds Piers' borane [HB(C6F5)2] at the indene double bond to give a mixture of regioisomeric boranes 8a,b. Subsequent isomerization under equilibrium conditions gives the isopropyl substituted 1H and 3H borylindenes 10a,b. Their treatment with the bulky LiTMP base under frustrated Lewis pair conditions resulted in a clean deprotonation reaction to give the borata-alkene 14. Its X-ray crystal structure analysis indicated a pronounced B[double bond, length as m-dash]C double bond character and thus a borata-benzofulvene description. The borata-alkene underwent (probably stepwise) [4 + 2] cycloaddition reactions with chalcone derivatives and a formal [6 + 2] cycloaddition with phenylmethylketene. Many products and derivatives were characterized by X-ray diffraction.
authors.affiliation: Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, D-48149 Münster, Germany. erker@uni-muenster.de.
authors.forename: Sonja
authors.initials: S
authors.lastname: Kohrt
authors.forename: Steffen
authors.initials: S
authors.lastname: Dachwitz
authors.forename: Constantin G
authors.initials: CG
authors.lastname: Daniliuc
authors.forename: Gerald
authors.initials: G
authors.lastname: Kehr
authors.forename: Gerhard
authors.initials: G
authors.lastname: Erker