Some Reactions of Free Radicals and Grignard Reagents with Organosilicon Compounds

Abstract

Considerable confusion exists in the literature concerning
the reactivity of allylsilanes in radical
addition reactions. The reactions of allylsilanes with
radical addition reagents have been reexamined and contrary
to a previous report it has been found that both carbon
tetrachloride and n-butyraldehyde add readily to allyitriethylsilane.
Similar reactions of both trimethyl- and
triphenylallylsilane with carbon tetrachloride and bromo=
trichloromethane also gave good yields of adducts. The
relative reactivities of the double bond in three series of
ω-alkenylsilanes, R3Si(CH2)nCH=CH2 (R=Me, Ph or Cl) toward addition by the trichloromethyl radical have been determined and the relative reactivities of vinyl- and
allyltrimethylsilane toward free radical addition by
n-dodecanethiol have been investigated. The factors
affecting the reactivities of the various ω-alkenylsilanes
toward radical addition reagents are discussed.

Unsuccessful attempts have been made to prepare
compounds containing silacyclopropane rings via Grignard
cyclisation reactions.

The reactions of hydrosilyl Grignard reagents with
chlorosilanes have been investigated and silyl chloride
reduction has been observed to predominate in many cases.
A mechanism for the reduction process is suggested.

Silyl alkoxides were isolated in good yield from
reaction of hydrosilylmethyl Grignard reagents with
benzophenone together with smaller quantities of benzhydrol
and 1,1-diphenylethylene. Possible mechanisms are discussed
for the formation of the observed products. The
products of reaction of benzoyl chloride and dimethyl-silylmethylmagnesium
bromide are those derived primarily
from reduction processes. A mechanism is proposed
involving the intermediacy of 2-sileisobutene.

The photolysis of hydrosilylmethyl Grignard reagents
and their reaction with cuprous chloride have been examined
with a view to the detection of silicon carbon Π-bonded
intermediates.

Date of Award	1972
Original language	English