Leaving groups chiral alkoxy

Substituted binaphthyl compounds can be synthesized in high optical yields using nucleophilic aromatic substitution reactions in which the chiral leaving groups are alkoxy moieties derived from naturally occurring alcohols28-29. For example, the condensation of 2-(l-alkoxynaphth-2-yl)-4.5-dihydro-4,4-dimethyl-l,3-oxazole with 1-naphthyllithium or 2-methoxy-l-naphthyl 2-magnesium bromide leads to (ft)- or (.S)-(l,T-binaphthyl-2-yl)-4,5-dihydro-4,4-dimethyl-l,3-oxazole derivatives. 

In the hope of gaining further experimental insight into the mechanism of nucleophilic displacement at sulfur, the alkaline hydrolysis of chiral dialkoxysulfonium salts was investigated (162). At least two interesting features of these model systems for nucleo-phihc substitution studies should be accentuated both alkoxy groups are of comparable leaving group ability, and there are essentially two identical tetrahedral faces to be attacked by the nucleophile. 

An alternate route to chiral binaphthyls involves displacement of a chiral l-alkoxy group from an achiral naphthyloxazoline with a-naphthyllithium or an a-naphthyl Grignard reagent. The optical yields in this process depend on the choice of the leaving group. 

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