title: Cobalt(I)-mediated preparation of polyborylated cyclohexadienes: scope, limitations, and mechanistic insight.
abstract: A series of 1,3- and 1,4-diboryl-1,3-cyclohexadienes have been prepared by intermolecular CoCp-mediated [2+2+2] cocyclizations of alkynylboronic pinacolate esters with alkenes, followed by oxidative demetallation with iron(III) chloride. The effect of substitution at the borylated alkyne on chemo- and regioselectivities has been studied, suggesting steric control. The proper choice of substituents allowed the preparation of 1,3-diborylated cyclohexadienes in a highly selective manner. Alternatively, 1,4-diborylated cyclohexadienes could be prepared from diborylated diynes. The scope of this reaction has been examined and found to include electron-poor, electron-rich, linear, and cyclic alkenes. The diborylated cyclohexadienes were submitted to single or double Suzuki-Miyaura cross-coupling reactions with haloarenes to afford polyarylated systems. The mechanism of the title reaction, including the regioselectivity of the cycloaddition steps, has been analyzed by means of DFT computations.
authors.affiliation: Laboratoire de Chimie Organique, Université Pierre et Marie Curie, Tour 44-54, 4 place Jussieu 75252 Paris, France.
authors.forename: Anaïs
authors.initials: A
authors.lastname: Geny
authors.forename: David
authors.initials: D
authors.lastname: Leboeuf
authors.forename: Gabriel
authors.initials: G
authors.lastname: Rouquié
authors.forename: K Peter C
authors.initials: KP
authors.lastname: Vollhardt
authors.forename: Max
authors.initials: M
authors.lastname: Malacria
authors.forename: Vincent
authors.initials: V
authors.lastname: Gandon
authors.forename: Corinne
authors.initials: C
authors.lastname: Aubert