Tosylhydrazones reaction with organolithium reagents

The tosylhydrazone of an aldehyde RCHO gives the reductive alkylation product RCH2R on reaction with organolithium reagent R Li. Although yields are mediocre, the procedure is simple and is particularly well suited for the introduction of branched alkyl groups.Treatment of a tosylhydrazone with n-butyl-lithium followed by MesMX (M = Si, Ge, or Sn) gives the vinyl-silane,... 

Metallated tosylhydrazones react with aldehydes and ketones to afford /8-hydroxytosylhydrazones in good to excellent yield. Further reaction with organolithium reagent gives the corresponding homoallylic alcohol (Scheme... 

The reaction of alkyllithium reagents with acyclic and cyclic tosylhydrazones can lead to mixtures of elimination (route A) and addition (route B) products (Scheme 22). The predominant formation of the less-substituted alkene product in the former reaction (Shapiro Reaction) is a result of the strong preference for deprotonation syn to the N-tosyl group. Nucleophilic addition to the carbon-nitrogen tosyl-hydrazone double bond competes effectively wiA a-deprotonation (and alkene formation) if abstraction of the a-hydrogens is slow and excess organolithium reagent is employed. Nucleophilic substitution is consistent with an Su2 addition of alkyllithium followed by electrophilic capture of the resultant carbanion. 

Other bases may be employed, e.g. lithium hydride, sodium hydride, sodium amide or sodium in ethylene glycol with sodium in ethylene glycol, the reaction is called the Bamford-Stevens reaction. Aldehyde tosylhydrazones (200) do not form dianions with organolithiums, but the reagent adds to the carbon-nitrogen double bond to give the dilithium derivative (201) which decomposes to the organolithium compound (202). 

---