title: Synthetic and Mechanistic Studies of Strained Heterocycle Opening Reactions Mediated by Zirconium(IV) Imido Complexes.
abstract: The reactions of the bis(cyclopentadienyl)(tert-butylimido)zirconium complex (Cp(2)Zr=N-t-Bu)(THF) (1) with epoxides, aziridines, and episulfides were investigated. Heterocycles without accessible beta-hydrogens undergo insertion/protonation of the C-X bond to produce 1,2-amino alcohols (X = O) and 1,2-diamines (X = NR), whereas heterocycles with accessible beta-hydrogens undergo elimination/protonation to produce allylic alcohols (X = O) and allylic sulfides (X = S). Mechanistic investigations support a stepwise pathway with zwitterionic intermediates for the first reaction class and a concerted pathway for the second reaction class. Additionally, the feasibility of chirality transfer from the planar-chiral ebthi (ebthi = ethylenebis(tetrahydroindenyl)) ligand was demonstrated with a chiral analogue, (ebthi)-Zr=NAr(THF) (Ar = 2,6-dimethylphenyl), 2, through the diastereoselective ring opening of meso epoxides.
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720.
authors.forename: Suzanne A
authors.initials: SA
authors.lastname: Blum
authors.forename: Vicki A
authors.initials: VA
authors.lastname: Rivera
authors.forename: Rebecca T
authors.initials: RT
authors.lastname: Ruck
authors.forename: Forrest E
authors.initials: FE
authors.lastname: Michael
authors.forename: Robert G
authors.initials: RG
authors.lastname: Bergman