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A qu
alit
ative study of the effects of v
arious substituents on the silicon
atom in cross-coupling re
actionsof
alkenylsil
anes h
as been c
arried out. In intermolecul
ar competition experiments, the influence of c
arbon-b
ased groups (methyl, ethyl, isopropyl,
tert-butyl, phenyl,
and 3,3,3-trifluoropropyl)
and
alkoxy groups(monoethoxydimethyl-, diethoxymethyl-,
and triethoxy) on the silicon h
ave been ev
alu
ated under
activ
ationby two different methods, fluoride (TBAF)
and sil
anol
ate (TMSOK). The influence of the substituentsw
as highly dependent on the method of
activ
ation. In the presence of TBAF, there w
as only
a modeststeric effect (except for
tert-butyl substituents),
and the efficiency decre
ased slightly with incre
asingnumbers of
alkoxy groups. In the presence of TMSOK,
a signific
ant steric effect w
as noted, but thenumber of
alkoxy groups h
ad
almost no influence. These trends were interpreted in terms of the divergentmech
anisms for the cross-coupling process.
