title: Regioselective, stereoselective, and conformationally controlled synthesis of (η4-tetraarylcyclobutadiene)(η5-carbomethoxycyclopentadienyl)cobalt metallocenes.
abstract: The Friedel-Crafts reaction of (η(4)-tetraphenylcyclobutadiene)(η(5)-carbomethoxycyclopentadienyl)cobalt with acid chlorides/aluminum chloride resulted exclusively in para-phenyl acylation. Both monoacylated (1.1 equiv of RCOCl/AlCl(3)) and tetraacylated products (>4 equiv of RCOCl/AlCl(3)) were synthesized. Reaction of PhCC(o-RC(6)H(4)) (R = Me, i-Pr) with Na(C(5)H(4)CO(2)Me) and CoCl(PPh(3))(3) gave predominantly (η(4)-1,3-diaryl-2,4-diphenylcyclobutadiene)(η(5)-carbomethoxycyclopentadienyl)cobalt metallocenes (1,3-[trans] vs 1,2-[cis] selectivity up to 6:1). Conformational control of Friedel-Crafts reactions on the major isomers gave exclusively para-acylation of the unsubstituted phenyl groups.
authors.affiliation: School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, United Kingdom.
authors.forename: Doyle J
authors.initials: DJ
authors.lastname: Cassar
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Nagaradja
authors.forename: David C D
authors.initials: DC
authors.lastname: Butler
authors.forename: Didier
authors.initials: D
authors.lastname: Villemin
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Richards