Deprotonation from Diphenylsilane with Organosilyllithium Agents

27 July 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

In contrast to their carbon analogs, there are only a few reports on deprotonation from silanes. This is because the normal polarization of a Si-H bond is Si(delta+)-H(delta-), while that of a C-H bond is C(delta-)-H(delta+). From a bond orbital perspective, a sigma*CH orbital has greater expansion on hydrogen, while a sigma*SiH orbital has greater expansion on Si. Thus, the lone pair of a base mainly attacks hydrogen of a C-H bond for deprotonation, but adds to the silicon atom of a Si-H bond. Previous reports showed that the assistance of negative hyperconjugation between the lone pair of the silyl anion and sigma* orbitals on silyl substituent(s) or an intramolecular chelating group (a pincer ligand) is necessary for deprotonation from silanes. In fact, Kira et al. found that treatment of diphenylsilane with t-butyllithium or LDA resulted in nucleophilic substitution, not deprotonation, only to eliminate a hydride as a leaving group. Recently, we developed a silicon-homologation reaction by a deprotonation-nucleophilic substitution sequence. In that reaction, we assumed that dispro-portionation led to alkoxysilyllithium or a silenoid species generated in situ. We expected that a disproportionation approach could be applied to the deprotonation of monosilanes, such as diphenylsilane. Here we report the first successful approach to the deprotonation of monosilanes with no intramolecular chelation.

Supplementary materials

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