Aj. Kresge et Jb. Tobin, PROTONATION OF PHENYL(TRIMETHYLSILYL)ACETYLENE - A SURPRISINGLY WEAK STABILIZATION OF A CARBOCATION BY A BETA-TRIMETHYLSILYL GROUP, Angewandte Chemie, International Edition in English, 32(5), 1993, pp. 721-723
The protodesilylation of the title compound 1 [Eq. (a)] proceeds via t
he vinyl cation 2, whose stabilization by the beta-trimethylsilyl grou
p is much smaller than expected, The comparison of the rate of protona
tion of 1 and that of phenyl-acetylene gives a small beta-silyl stabil
izing effect (DELTADELTAG(not-equal) = 3.4 kcal mol-1). This surprisin
g result is explained by insufficient hyperconjugation. [G