Coordination-induced proximity

Interestingly, in the reaction of 2-(3-chlorophenyl)-4,4-dimethyloxazoline with an alkyllithium [25], the deprotonation is chelation-controlled, but the addition of R" follows PAR. A reverse regioselectivity for alkylcuprate addition may well be explained by a complex-induced proximity effect which has been invoked to rationalize the alkyllithium additions. It is known that copper coordinates exceptionally well with amino and imino ligands. 

An insight into the deprotonation reaction of 1 with rert-butyllithium can be gained by computational methods [9]. In the experiment, this reaction is effected at very low temperatures (-70 to -90 °C) under kinetically controlled conditions. Under these conditions, the reaction will proceed via the energetically more stable transition state. Two reaction paths are plausible, resulting in the formation of the two possible epimers (R,S)-2 and (SJS)-2. Each of these reaction paths will be considered separately. With the implication of the complex induced proximity effect (CIPE) [10], the reaction is believed to start with a pre-coordinated te/t-butyllithium molecule, whose lithium... 

A basic three-step mechanism has been proposed to explain the DoM reaction (Scheme 11.2). This invokes the complex-induced proximity effect (CIPE) wherein the allq l lithium aggregate (RLi) coordinates to the DMG through an equilibrium process, and the complex thus formed places the base in close proximity to the ortho proton leading to a coordinated ortho-lithiated species, which then reacts with the electrophile to form the 1,2-disubstituted arene. ... 

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