Vinyllithiums intramolecular carbolithiation

In this context we have recently reported that A-2-bromoallyl-iV-(3-functionalized) allylamines 315 undergo, after formation of the corresponding vinyllithiums, intramolecular carbolithiation processes giving rise to functionalized methylenepyrrolidines 316 in good yields. We have shown that a moderately activating group at the terminal position of the double bond favours the cyclization reaction and we have presented the first... 

To check the different reactivity for the carbolithiation reaction of a lithiated double bond by vinyl- or aryllithiums, tertiary amine 341 was synthesized and treated with 6 equivalents of f-BuLi and TMEDA. Subsequent deuteriolysis led to a 6 1 mixture of the dihydropyrrole derivative 342 and the indole derivative 343 in very good overall yield, showing that intramolecular carbolithiation reaction of a lithiated double bond by a vinyllithium is faster than the corresponding carbolithiation reaction by an aryllithium (Scheme 88)141. 

An extension of this intramolecular carbolithiation was recently disclosed for the preparation of bis-exocyclic 1,3-dienes by the 5-exo-dig cyclization of (5-acetylenic vinyllithiums. Through subsequent Diels-Alder chemistry, they serve as useful precursors of polycyclic ring systems [14a] (Scheme 7-13). 

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