Epoxide-opening and group-transfer reactions mediated by monomeric zirconium imido complexes.
N-tert-Butylimidozirconocene (Cp2Zr=Nt-Bu) and its analogue (ebthi)Zr=NAr (ebthi = ethylenebis(tetrahydroindenyl), Ar = 2,6-dimethylphenyl) undergo overall cycloaddition reactions at ambient temperature with epoxides that lack accessible beta-hydrogens. The process results in addition of the Zr=N bond to an epoxide C-O bond, leading to azazirconacyclopentanes. The regio- and stereochemistry of the products implicate a stepwise mechanism, with the intermediacy of zwitterions having substantial carbocation character at the substituted carbon of the ring-opened epoxide-derived fragment. The azametallacycles undergo facile cleavage to beta-amino alcohols upon addition of mild acid.
Blum
Suzanne A
SA
Center for New Directions in Organic Synthesis, Department of Chemistry, University of California, Berkeley, CA 94720, USA.
Walsh
Patrick J
PJ
Bergman
Robert G
RG
D018360:Crystallography, X-Ray; D004852:Epoxy Compounds / Q000737:chemistry*; D007094:Imides / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D013237:Stereoisomerism; D015040:Zirconium / Q000737:chemistry*
D004852:Epoxy Compounds; D007094:Imides; D009942:Organometallic Compounds; C013690:styrene oxide; D015040:Zirconium