Lithio 2- vinyllithium

The initial reaction between allylzinc bromide (69) and vinyllithium (101) gives a stable complex 102. In the next step this intermediate forms, via transition state 103, the lithio zinc adduct 104, which then oligomerizes to give very stable 105. 

Tellurium-lithium exchange proceeds in much the same way as selenium-lithium exchange but is rarely used.144 Vinyltellurides such as 179 can be converted stereospecifically into vinyllithiums 180,145 and alkyltelluro-heterocycles have been used as precursors to lithio-species.146... 

The first vinyllithium carbolithiation reaction was reported by Chamberlin and Bloom15, who showed that vinyllithium reagents derived from ketone trisylhydrazones undergo anionic cyclization reactions to give functionalized cyclopentanes (Scheme 4). These authors have also shown that 5-, 4- and 3-alkyl-substituted 2-lithio-l,6-heptadienes like... 

In l-hthio vinyl sulfides (sec. 8.6) the sulfur atom stabilized the carbanion, allowing either alkylation or condensation reactions. The sulfonyl moiety can also stabilize a vinyllithium derivative. Vinyl sulfone (321), for example, was converted to the 1-lithio derivative with methyllithium.332 xhis organometallic reacted in the usual manner with alkyl halides (methyl iodide) to give the coupling product, 322. 

IG ) level predict almost equal stability for both products. The 6-lithio derivative (three-membered chelate with N-1) is predicted to be only 0.5 kcalmoP less stable than the 5-isomer (four-membered chelate with the methoxy oxygen). Oxygen-chelated 4-lithio-5-methoxy-l,2,3-triazine is, however, lEOkcalmoP less stable than with N-3 chelation. The Li-C bond polarity has been estimated to be close to that in vinyllithium by natural population analysis (NPA) at the FIF/... 

Alternate Names l-lithio-l-(trunethylsilyl)ethylene a -(tri-methylsilyl)vinyllithium. 

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