Reactivity of the Triple Ion and Separated Ion Pair of Tris(trimethylsilyl)methyllithium with Aldehydes: A RINMR Study
摘要:
Low-temperature rapid-injection NMR (RINMR) experiments were performed on tris(trimethylsilyl) methyllithium. In THF/Me2O solutions, the separated ion (IS) reacted faster than can be measured at -130 degrees C with Mel and substituted benzaldehydes (k >= 2s(-1) whereas the contact ion (1C) dissociated to IS before reacting. Unexpectedly, the triple ion reacted faster with electron-rich benzaldehydes relative to electron-deficient ones. The addition of HMPA had no effect on the rate of reaction of the triple ion with p-diethylaminobenzaldehyde, and the immediate product of the reaction was the HMPA-solvated separated ion IS, with the Peterson product forming only slowly. Thus, the aldehyde is catalyzing the dissociation of the triple ion. HMPA greatly decelerated the reaction of IS (< 10(-10)), providing an estimate of the Lewis acid activating effect of a THF-solvated lithium cation in an organolithium addition to an aldehyde.
作者:Bildstein, Benno、Giselbrecht, Karlheinz、Sladky, Fritz
DOI:——
日期:——
Reactivity of the Triple Ion and Separated Ion Pair of Tris(trimethylsilyl)methyllithium with Aldehydes: A RINMR Study
作者:Amanda C. Jones、Aaron W. Sanders、William H. Sikorski、Kristin L. Jansen、Hans J. Reich
DOI:10.1021/ja8003528
日期:2008.5.1
Low-temperature rapid-injection NMR (RINMR) experiments were performed on tris(trimethylsilyl) methyllithium. In THF/Me2O solutions, the separated ion (IS) reacted faster than can be measured at -130 degrees C with Mel and substituted benzaldehydes (k >= 2s(-1) whereas the contact ion (1C) dissociated to IS before reacting. Unexpectedly, the triple ion reacted faster with electron-rich benzaldehydes relative to electron-deficient ones. The addition of HMPA had no effect on the rate of reaction of the triple ion with p-diethylaminobenzaldehyde, and the immediate product of the reaction was the HMPA-solvated separated ion IS, with the Peterson product forming only slowly. Thus, the aldehyde is catalyzing the dissociation of the triple ion. HMPA greatly decelerated the reaction of IS (< 10(-10)), providing an estimate of the Lewis acid activating effect of a THF-solvated lithium cation in an organolithium addition to an aldehyde.
Multinuclear NMR Study of the Solution Structure and Reactivity of Tris(trimethylsilyl)methyllithium and its Iodine Ate Complex
作者:Hans J. Reich、William H. Sikorski、Aaron W. Sanders、Amanda C. Jones、Kristin N. Plessel
DOI:10.1021/jo802032d
日期:2009.1.16
The extreme steric bulk of tris(trimethylsilyl)methyl derivatives (1-X) provides interesting structural and dynamic behavior for study. Dynamic NMR studies on 1-SePh and 1-I showed restricted rotation around the C−Si bonds of each trimethylsilyl groups. An extensive multinuclear NMR study of natural abundance and 6Li and 13C enriched 1-Li revealed three species in THF-containing solvents, a dimer 1T