The combination of an alkoxy and an amino function combined in one silane is rarely found due to the difficult synthesis and isolation.[1] However, this combination offers unique opportunities to investigate the influence of steric requirements or the size of a metal on the structure or reactivity of alkoxysilylamides towards electrophiles by varying the metallating reagent (n‐butyllithium or di‐n‐butylmagnesium) or the organo group on the amino function. For this purpose, we synthesized two alkoxyaminosilanes with acidic NH units that can be metalated. On the one hand, the tert‐butylamino‐substituted (tert‐butylamino)‐methoxydiphenylsilane (1) and on the other hand the isopropylamino‐substituted methoxydiphenyl(isopropylamino)silane (2). The resulting structures showed an interesting interrelation between the Si–O or Si–N bond lengths and the strength of the coordinative bond to the corresponding metal cation (lithium or magnesium).

We report a highly selective substitution of silicon-bound methoxy groups by primary lithium amides. This unusual reactivity is possible because of the formation of particularly stable lithium methoxide, which compensates for the decreased Si–N bond enthalpy compared to Si–O bonds. In contrast to substitution reactions on halosilanes, highly selective monosubstitutions under mild conditions are possible, even in the presence of further reactive methoxy groups. A combination of experiments and density functional theory calculations was carried out in order to get an extensive understanding of the reaction. The calculations reveal a possible reaction mechanism with considerably low activation barriers and the entry of the nucleophile to be the rate-determining step. The low activation energies allow for the substitutions to be carried out at low temperatures, therefore preventing side reactions from occurring. The presented investigations expand the view of fundamental transformation processes on silicon and give access to a wide variety of functionalized silicon-based building blocks for various fields of chemistry.

Das ITA erforscht in Zusammenarbeit mit C. Gerhardt eine neue Methode zur Faserextraktion, um die Qualitätssicherung von Faserbeschichtungen zu vereinfachen.

Organolithium compounds have been used successfully in flow chemistry since the recent past. Most of the studies dealt with the use in halogen-lithium exchanges. So far, however, there has been a lack of use in substitution reactions. The use of flow microreactors makes the highly reactive organolithium compounds more controllable and thus creates new synthetic possibilities.