Sparteine-n-BuLi

The reaction of the preformed (-)-sparteine n-BuLi complex (1 equiv) with benzaldehyde AT-(diisobutylalumino)imine (1 equiv) at -78 °C in pentane gave the best result 70% yield and 74% ee favoring the i -enantiomer. On the other hand, a preformed (-)-sparteine benzaldehyde N-borylimine complex (1 equiv) was treated with -BuLi (1 equiv) at -78 °C in Et20 to give the corresponding primary amine in 68% yield and 50% ee, favoring also the i -enantiomer. 

Triphenylmethyl methacrylate (TrMA) is a unique monomer, which affords a highly isotactic polymer (PTrMA) even by a radical process, and the polymer with more than a 95% triad isotacticity can be obtained by the anionic polymerization with butyllithium (BuLi) [10]. In 1979, we found that optically active PTrMA is formed during the anionic polymerization of TrMA with the complex of ( )-sparteine-n-BuLi at —78°C (Fig. 5) [11, 12]. This is the first example of helix-sense-selective polymerization preferentially producing a stable one-handed helical polymer through the polymerization process. The results clearly indicated that the existence of a stable helical polymer even in solution is possible on a vinyl polymer without chiral side groups. The helical structure is maintained due to the steric hindrance of the bulky triphenylmethyl groups. Therefore, when the ester groups are hydrolyzed with an acid, the optical activity of the polymer disappears. 

Fig. 5 Helix-sense-selective polymerization of triphenylmethyl methacrylate (TrMA) with (—)-sparteine-n-BuLi complex. Reprinted by permission from Chemical Society of Japan [5]...

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