Reactions of aliphatic terminal alkynes with Ti(OiPr)₄/BuLi: selectivity, kinetic aspects, and a new tetramerisation process

The reactions of terminal aliphatic alkynes with Ti(OiPr)4/nBuLi or Ti(OiPr)4/sBuLi were investigated. These substrates were transformed more slowly than previously studied 1-aryl acetylene compounds and mixtures of products were generally obtained. This allowed the rate constants of the elementary steps involved to be evaluated. One substrate was shown to undergo cyclotrimerisation with high regioselectivity in favour of the 1,2,4 adduct. Furthermore, an unprecedented tetramerisation process was uncovered.