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T. Godou et al.
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Synlett
chemical behavior is consistent with previous findings from
Beller et al. on the reactivity of iron(II) complexes support-
ed by 4 in the presence of formic acid.30
to silyl ethers. The iron catalyst exhibits a catalytic behavior
similar to (triphos)Ru(OAc)2 in this reaction and was shown
to produce iron-hydride species in dichloromethane, in the
presence of silyl formates. Further efforts are underway in
our laboratories to exploit the reducing ability of such in-
termediates in new transfer hydrosilylation reactions.
Funding Information
For financial support of this work, we acknowledge CEA, CNRS, the
CHARMMMAT Laboratory of Excellence and the European Research
Council (ERC Starting Grant Agreement n.336467). T.C. thanks the
Foundation Louis D. – Institut de France for its support.
)(
Supporting Information
Supporting information for this article is available online at
Figure 1 View of complex 22 ([Fe(4)HCl]). Displacement ellipsoids are
drawn at the 50% probability level and carbon-bound hydrogen atoms
are omitted.
S
u
p
p
ortiInfogrmoaitn
S
u
p
p
o
nrtogI
f
rmoaitn
References and Notes
The catalytic implication of 22 was tested in the silyla-
tion of 3. As expected, 22 possesses a catalytic activity sim-
ilar to Fe(OAc)2/4 and the complex promotes the formation
of 5a in the reaction described in Scheme 3. Based on these
data, a mechanistic proposal is drawn in Scheme 6: an ac-
tive iron(II) hydride species (likely 22) is formed from
Fe(OAc)2 in the presence of 4 and the silyl formate reduc-
tant. The complex is then able to decompose HCO2H by suc-
cessive dehydrogenation and decarboxylation steps, in or-
der to displace the equilibrium involving the alcohol, the si-
lyl ether, and free formic acid to the formation of the silyl
ether product.
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O
Fe(OAc)2
OH
+
SiR3
R'
H
O
P(C2H4PPh)3 (4)
Et3SiOCHO (2a)
CH2Cl2
Fe
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+
(PP3)Fe
R'
H
OH
Cl
CO2
22
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O
Cl
Scheme 6 Proposed mechanism for the dehydrogenative and decar-
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© Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–E