Abstract
The synthesis of silanes starting from multifunctionalized precursors often suffers
from low chemoselectivity due to the similar kinetic reaction profiles, leading to
the formation of difficult to separate side products. The opposite approach, which
is an access based on unreactive tetraalkylsilanes as starting materials, is far less
developed. Making use of the silylium-ion-initiated chemoselective halodealkylation
of tetraalkylsilanes recently developed by our laboratory, an extension of this protocol,
namely the direct synthesis of dihalosilanes from tetraalkylsilanes, is reported.
Following a sequence of halodehydrogenation and halodealkylation, trialkylhydrosilanes
can also be converted into dihalosilanes. Commercially available 1,2-dihaloethane
acts as the halogen source and is involved in the generation of the catalytically
active arenium ion by an SEAr substitution of the benzene solvent. The formation of an uncommon halogen-substituted
silylium ion as an intermediate is assumed, likely accounting for the need of an elevated
reaction temperature.
Key words
arenium ions - halodealkylation - halodehydrogenation - Lewis acids - silicon - silylium
ions
