Chiral diamines. Part 3: Effect of ligand structure on the enantioselective deprotonation of N-Boc-pyrrolidine with i-PrLi: a computational comparison of (−)-sparteine and (S,S)-1,2-bis(N,N-dimethylamino)cyclohexane

The deprotonation N-Boc-pyrrolidine by i-PrLi–(S,S)-1,2-bis(N,N-dimethylamino)cyclohexane has been studied at the HF/3-21G and B3P86/6-31G* theoretical levels. The two lowest energy complexes of the N-Boc-pyrrolidine–i-PrLi–diamine ligand, as well as the transition states leading to proton transfer, were found to be similar in both geometry and energy in accord with experimental findings. The results are compared to those for the analogous but enantioselective (−)-sparteine-mediated deprotonation.