Wittig rearrangements asymmetric deprotonation

Enantioselective deprotonation to yield a configurationally defined organolithium offers great potential for future asymmetric [2,3]-Wittig rearrangements. The first steps in this area were taken by Nakai and Tomooka, who treated 182 with r-BuLi in the presence of the bis-oxazoline ligand 114. The product 183 is formed in 89% ee.133... 

Chiral lithium bases have been used for enantioselective deprotonation to yield configurationally stable a-oxy carbanions. This holds potential for asymmetric [2,3]-Wittig rearrangement in stereoselective synthesis. Thus, treatment of propargylic ether 72 with (S,S)-3 in THF at — 70 °C to —15 °C afforded propargylic alcohol 73 in 82% yield and in 69% ee of the shown enantiomer96,97. This product was successfully employed as a precursor of (-l-)-Aristolactone (Scheme 55). 

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