Thermodynamic versus kinetic control in substituent redistribution reactions of silylium ions steered by the counteranion† †Electronic supplementary information (ESI) available: Experimental details, characterization, spectroscopic and crystallographic data, DFT calculation methods, energy data, and the coordinates of the calculated geometries. CCDC 1818576, 1818581, and 1818582. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c8sc01833b
| Autor: | Omann, Lukas, Pudasaini, Bimal, Irran, Elisabeth, Klare, Hendrik F. T., Baik, Mu-Hyun, Oestreich, Martin |
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| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: | |
| Zdroj: | Chemical Science |
| ISSN: | 2041-6539 2041-6520 |
| Popis: | Substituent exchange reactions of silylium ions can be steered in opposite directions. The judicious choice of the hydrosilane and the counteranion enables the selective formation of either triaryl- or trialkylsilylium ions. An in-depth experimental and theoretical study of the substituent exchange reaction of silylium ions is presented. Apart from the substitution pattern at the silicon atom, the selectivity of this process is predominantly influenced by the counteranion, which is introduced with the trityl salt in the silylium ion generation. In contrast to Müller's protocol for the synthesis of triarylsilylium ions under kinetic control, the use of Reed's carborane anions leads to contact ion pairs, allowing selective formation of trialkylsilylium ions under thermodynamic control. DFT calculations finally revealed an unexpected mechanism for the rate-determining alkyl exchange step, which is initiated by an unusual 1,2-silyl migration in the intermediate ipso-disilylated arenium ion. The resulting ortho-disilylated arenium ion can then undergo an alkyl transfer via a low-barrier five-centered transition state. |
| Databáze: | OpenAIRE |
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