Deprotonation quantum chemical studies

The deprotonation of A-Boc-piperidine (159), giving substituted piperidines such as 160, proceeds with much lower efficiency (equation 36)" " . The main side reaction is the attack of i-BuLi at the Boc-group. The observation of slower and less selective lithiation is supported by quantum-chemical studies. ... 

Quantum chemical DFT calculations at the B3LYP/6-31G(d) level have been used to study the enantioselective lithiation/deprotonation of O -alkyl and O-alk-2-enyl carbamates in the presence of (—)-sparteine and (—)-(f )-isosparteine.7 Complete geometry optimization of the precomplexes consisting of the carbamate, the chiral ligand, and the base (/-PrLi), for the transition states of the proton-transfer reaction, and for the resulting lithio carbamates have been performed in order to quantify activation barriers and reaction energies. 

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