Butyllithium sparteine asymmetric deprotonation

The Sparteine Method 42 was applied successfully to generate chiral a-lithiated pyrrolidine when using the Boc-protected (tcrt-butoxycarbonyl)pyrrolidine and sec-butyllithium/sparteine as an asymmetric deprotonating agent in diethyl ether at — 78 °C. Alkylation, silylation, stanny-lation and methylation occurred with good yield (70-75%) and high selectivity (95% ee)53. 

Asymmetric deprotonation of /V-(/-butoxycarbonyl)indolincs at the 2-position with s-butyllithium-(—)-sparteine has been reported.161 Results of an ab initio MO study of deprotonated 2,3-dihydrooxepin suggest that the allylic anion is 15 kcal mol 1 more stable than the vinylic anion, which is, in turn, 8 kcal mol 1 more stable than the vinyl anion of cyclohepta-l,3,5-triene.162... 

A-(i-butoxycarbonyl)-)V-(p-methoxyphenyl)allylamines 1,3-diphenylpropene is accomphshed with butyllithium in the presence of (—)-sparteine, followed by the addition of TMSOTf (eq 47). The same procedure allows the asymmetric deprotonation-substitution of arenetricarbonyl(0) complexes, while chiral bis(oxazolines) have been the ligands of choice to perform such transformation with aryl benzyl sulfides in these reactions, different yields and enantioselectivities are reached if trimethylsilyl chloride is used as silylating reagent, although there is a substrate dependence and no definite rules can be established. 

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