Communication
Chemoselective Cleavage of Si−C(sp3) Bonds in Unactivated
Tetraalkylsilanes Using Iodine Tris(trifluoroacetate)
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ABSTRACT: Organosilanes are synthetically useful reagents and precursors in organic chemistry. However, the typical inertness of
unactivated Si−C(sp3) bonds under conventional reaction conditions has hampered the application of simple tetraalkylsilanes in
organic synthesis. Herein we report the chemoselective cleavage of Si−C(sp3) bonds of unactivated tetraalkylsilanes using iodine
tris(trifluoroacetate). The reaction proceeds smoothly under mild conditions (−50 °C to room temperature) and tolerates various
polar functional groups, thus enabling subsequent Tamao−Fleming oxidation to provide the corresponding alcohols. NMR
experiments and density functional theory calculations on the reaction indicate that the transfer of alkyl groups from Si to the I(III)
center and the formation of the Si−O bond proceed concertedly to afford an alkyl-λ3-iodane and silyl trifluoroacetate. The developed
method enables the use of unactivated tetraalkylsilanes as highly stable synthetic precursors.
ilyl groups are stable and easy-to-handle synthetic
linchpins that can be converted into various functional
using a phenylthallium(III) complex (Scheme 1b).9 More
recently, Suginome and co-workers developed a stepwise
approach to convert trimethylsilyl groups into hydroxy groups
via Ir-catalyzed C−H borylation of a Me group and three
subsequent oxidative transformations in the presence of ester
or ether functionalities (Scheme 1c).10a However, only very
few oxygen-containing substrates were examined in those
reports. Thus, the development of general methods for the
cleavage of unactivated Si−C(sp3) bonds that can tolerate
various polar functional groups is important for the further
expansion of the application of tetraalkylsilanes in organic
chemistry.10b
S
groups via oxidation, halogenation, and cross-coupling
reactions.1 While transformations of arylsilane derivatives
have been widely studied, alkylsilanes have attracted less
attention in organic synthesis because of their lower reactivity.
A notable exception is the Tamao−Fleming oxidation,2 which
transforms alkylsilanes into the corresponding alcohols,
typically using peroxides and fluoride activators. These
protocols have often been employed in the total synthesis of
complex natural products.3 Nevertheless, to facilitate oxidation
of the silyl groups, the silicon atom must carry at least one
heteroatomic functional group or aryl/allyl substituent, which
can be selectively converted into a heteroatomic functional
group through electrophilic transformations.4 Simple, unac-
tivated tetraalkylsilanes are unreactive under conventional
organic synthesis reaction conditions, including those of the
Tamao−Fleming oxidation. The synthetic utility of trialkylsilyl
groups (e.g., −SiMe3 and −SiEt3) in aliphatic backbones has
scarcely been explored.5 However, the high stability of
tetraalkylsilanes and the low cost of some trialkylsilyl reagents
would make the application of tetraalkylsilanes as synthetic
precursors attractive if the Si−C(sp3) bond could be cleaved
under mild reaction conditions.
Herein we report the chemoselective cleavage of Si−C(sp3)
bonds in unactivated tetraalkylsilanes containing a wide range
of polar functional groups using iodine tris(trifluoroacetate)
(ITT) (Scheme 1d). We discovered that ITT reacts with
various tetraalkylsilanes under mild reaction conditions (−50
°C to room temperature) to cleave Si−C(sp3) bonds. The
resulting intermediates can be further converted into the
corresponding alcohols via subsequent oxidation with H2O2.
During our studies on the reactivity of ITT and I(OAc)3 in
organic synthesis,11,12 we envisioned that the high electro-
philicity of ITT could potentially enable the cleavage of
unreactive electron-rich covalent bonds, including Si−C(sp3)
bonds. We initially attempted the reaction of ITT with Me4Si
(A) in CDCl3 at room temperature (Scheme 2). To our
delight, the cleavage of one Si−C(sp3) bond of A proceeded
Cleavage of the Si−C(sp3) bonds in unactivated tetraalkyl-
silanes has to date mainly been accomplished by proto-
desilylation reactions using strong Brønsted acids,6 redistrib-
ution reactions using strong Lewis acids,7 or oxidation
reactions using highly electrophilic reagents.8 In most of
those previous studies, the substrates have been limited to
Me4Si or other tetraalkylsilanes that do not carry polar
functional groups, and the functional group tolerance has not
yet been investigated (Scheme 1a). In 1993, Murai and co-
workers reported the oxidative cleavage of unactivated Si−
C(sp3) bonds in a hydroxy-group-containing tetraalkylsilane
Received: November 6, 2020
J. Am. Chem. Soc. XXXX, XXX, XXX−XXX
© XXXX American Chemical Society
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