Oxazolines reaction with organolithium

An auxiliary approach was developed by Meyers, who found that unsaturated oxazolines such as 58 participate in asymmetric conjugate addition reactions with organolithium reagents (Equation 11) [74, 75]. With these substrates, a wide variety of chiral /1-substituted acids, including 59, were obtained with excellent enantioselectivity [75]. The yields were highest for substrates lacking allylic protons, as y-deprotonation was observed as a competing unwanted side reaction. 

The mechanism of organolithium addition to naphthyl oxazolines is believed to occur via initial complexation of the alkyllithium reagent to the oxazoline nitrogen atom and the methyl ether to form chelated intermediate 17. Addition of the alkyl group to the arena 7t-system affords azaenolate 18, which undergoes reaction with an electrophile on the opposite face of the alkyl group to provide the observed product 4. The chelating methyl... 

Asymmetric addition to chiral oxazolines. The chiral 1-oxazolinylnaphthalene 2, obtained by the reaction of (-I- )-l with a-naphthy.amide, reacts with an organolithium to form an intermediate enolatc that is trapped on me opptisite face by an electrophile to give 3 as a mixture of diastereomers in the ratio s3 17. The major product results from attack of the organolithium at the p-facc. The dia tercomers arc separable by flash chro-... 

Lithiated oxazolines (22) are asymmetric carboxylic acid enolate equivalents, allowing quite reasonable optical induction in many cases. Organolithium reagents add to vinyloxazolines such as (23) [obtained by reaction of (22 R = H) with 3-methoxypropanal], and this approach has been applied to the synthesis of chiral lactones. ... 

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