Metallation-silylation and kinetic studies of arylmethylacetylenes

Arylmethylacetylenes, XC₆H₄CCCH₃, have been metallated with an excess of n-butyllithium in diethyl ether at 0°C. By quenching the metallation mixtures with trimethylchlorosilane at different times, mono-, di- and tri-silyl derivatives have been isolated. Pseudo-first order rate constants for the monometallation were calculated from the rate of formation of the silylated products. A Hammett plot gave ? = 1.3, indicating moderate delocalization into the aromatic ring, of the negative charge developed at the propargylic carbon during the metallation.