Acetylenic alkyllithiums cyclization

Although the chemistry of anionic cyclizations of organolithium moieties derived from acetylenic systems has been less investigated38, studies of some acetylenic alkyllithiums, e.g. 131 (formed from 130), have shown that the ring closure proceeds in a regiospecific and highly stereoselective syw-fashion to give exocyclic vinyllithiums 132 (Scheme 43). 

In light of the facile 5-exo-dig carbolithiation reaction of simple acetylenic alkyllithiums, Bailey and Longstaff have studied the analogous 5-exo cyclization of a benzyne-tethered alkyllithium. Regioselectively 4-functionalized indanes 281 have been prepared... 

---