Epoxide-Opening and Group-Transfer Reactions Mediated by Monomeric Zirconium Imido Complexes
2003-11-26T00:00:00Z (GMT) by
N-tert-Butylimidozirconocene (Cp2ZrNt-Bu) and its analogue (ebthi)ZrNAr (ebthi = ethylenebis(tetrahydroindenyl), Ar = 2,6-dimethylphenyl) undergo overall cycloaddition reactions at ambient temperature with epoxides that lack accessible β-hydrogens. The process results in addition of the ZrN bond to an epoxide CO 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 β-amino alcohols upon addition of mild acid.
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