Abstract
The addition of 1 equiv of KO2 and Kryptofix222 (Krypt) in CH3CN to a solution of LCu(CH3CN) EL = N,N'-bis(2,6-diisopropylphenyl)2,6-pyridinecarboxamide] in tetrahydrofuran at -80 degrees C yielded [K(Krypt)][LCuO2], the enhanced stability of which enabled reexamination of its reactivity with 2-phenylpropionaldehyde (2-PPA). Mechanistic and product analysis studies revealed that [K(Krypt)] [LCuO2] reacts with wet 2-PPA to form [LCuOH](-), which then deprotonates 2-PPA to yield the copper(II) enolate complex [LCu(OC=C(Me)Ph)](-). Acetophenone was observed upon workup of this complex or mixtures of KO2 and 2-PPA alone, in support of an alternative mechanism(s) to the one proposed previously involving an initial nucleophilic attack at the carbonyl group of 2-PPA.