Tosylhydrazones reaction with organolithium

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... 

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). 

The Shapiro Reaction, a variation on the Bamford-Stevens Reaction, is the base-induced reaction of tosylhydrazones to afford alkenes. This reaction is carried out with two equivalents of an organolithium compound. 

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. 

The base catalyzed decomposition of arylsulfonylhydrazones of aldehydes and ketones to provide alkenes is called the Bamford-Stevens reaction. When an organolithium compound is used as the base, the reaction is termed the Shapiro reaction. The most synthetically useful protocol involves treatment of the substrate with at least two equivalents of an organolithium compound (usually MeLi or BuLi) in ether, hexane, or tetramethylenediamine. The in s/ft formed alkenyllithium is then protonated to give the alkene. The above procedure provides good yields of alkenes without side reactions and where there is a choice, the less highly substituted alkene is predominantly formed. Under these reaction conditions tosylhydrazones of a,(3-unsaturated ketones give rise to conjugated dienes. It is also possible to trap the alkenyllithium with electrophiles other than a proton. 

LDA). Furthermore, Katrizky and coworkers have achieved highly stereoselective synthesis of -stilbene by reaction of tosylhydrazones with benzotriazole-stabilized carbanion with the aid of organolithium [32,33] - see (5) - X = 1 -benzotriazolyl (Bt). This method can be compared with Julia-type olefination, in which aldehyde is the substrate in the place of tosylhydrazone. 

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