Organolithium reagents, addition hydrolysis

The addition reactions of alkyllithium-lithium bromide complexes to a-trimethylsilyl vinyl sulfones that have as a chiral auxiliary a y-mono-thioacetal moiety derived from ( + )-camphor are highly diastereoselective. A transition state that involves chelation of the organolithium reagent to the oxygen of the thioacetal moiety has been invoked. The adducts are readily converted via hydrolysis, to chiral a-substituted aldehydes22. 

Some imidoyllithiums 52 derived from triphenylmethyl isocyanide (51) dissociate to produce nitriles, which react with an organolithium reagent to give the corresponding imines and, after their hydrolysis, ketones. The intermediate nitrile can be isolated working at —78°C, whereas for the isolation of imines or ketones, after addition of the organolithium, the reaction was allowed to warm to room temperature (Scheme 14)74. The structure of the imidoyllithium intermediate has been assigned by IR spectroscopy... 

Dimethyl 2-phenylselanyl fumarate has also been used as a good Michael acceptor of organolithium reagents [57]. After hydrolysis of the resulting enolates, the addition products were isolated in good yields (66 - 82 %) with the major formation of the erythro-isomer. The oxidative syn elimination of the selanyl... 

Grignard reagents and organolithium reagents react as carban-ions with aldehydes and ketones to give alcohols in a two-step process (1) acyl addition and (2) hydrolysis. The organometallic reagent reacts as a nucleophile with epoxides at the less substituted carbon atom. 

Tomioka documented the use of organolithium reagents in enantioselec-tive conjugate additions to conjugated imines (Equation 31) [136]. The readily available chiral diether 173 served to mediate such additions with high asymmetric induction for example, the addition of PhLi to 172 furnished aldehyde 174 in 94% ee after hydrolysis of the imine adduct. In subsequent developments, Tomioka reported the enantioselective preparation of biaryls in which a naphthyllithium participates in a nucleophilic aromatic substitution catalyzed by only 5mol% of 173 (see insert on the left) and delivers the product in 82% ee [137]. 

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