Organometallics
Communication
the electrophilicity of the silyliminium ion must be well
balanced.
Table 2. Reduction of Aryl- and Alkyl-Substituted N-
Tosylated Aldimines Using either tBuFcMeSiH (2) or
Et3SiH (8) as Hydride Source
a
ASSOCIATED CONTENT
* Supporting Information
■
S
Text and figures giving general procedures and characterization
data as well as 1H, 13C, and 29Si NMR spectra for amines 5d−f,
d-5f, 7f, and 17f−24f as well as the deuterated silane d-2. This
material is available free of charge via the Internet at http://
AUTHOR INFORMATION
Corresponding Author
b
■
yield (%)
entry
imine
R3
amine
with 2
with 8
1
2
3
4
5
6
7
8
9
4f
Ph
5f
90
61
85
59
93
63
98
95
97
96
92
78
93
90
66
99
96
96
Notes
9f
4-BrC6H4
4-tolyl
17f
18f
19f
20f
21f
22f
23f
24f
The authors declare no competing financial interest.
10f
11f
12f
13f
14f
15f
16f
2-Tolyl
ACKNOWLEDGMENTS
This research was supported by the Deutsche Forschungsge-
meinschaft (International Research Training Group Munster-
■
1-naphthyl
2-naphthyl
cyclohexyl
tert-butyl
pentan-3-yl
̈
Nagoya, GRK 1143) and the Studienstiftung des deutschen
Volkes (predoctoral fellowship to K.M., 2009−2012). M.O. is
indebted to the Einstein Foundation (Berlin) for an endowed
professorship.
a
All reactions were performed according to the general procedure (cf.
the Supporting Information) on a 0.20 mmol scale. Analytically pure
b
product after flash column chromatography on silica gel.
REFERENCES
■
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In summary, we have demonstrated the potential of silylium
ions to act as promoters for the reduction of imines. Several N-
tosylated aldimines were readily reduced to the corresponding
amines at room temperature using either our tBuFcMeSiH (2)
or commercially available Et3SiH (8) as the stoichiometric
hydride source. With Et3SiH (8), even an N-tosylated ketimine
was reduced under these mild reaction conditions. The catalyst
performance is, however, inferior to that of the B(C6F5)3/
R3SiH combination, where hydrosilylation is faster and less
reactive imines do react at an elevated temperature of 70 °C.24a
That might be due to the intermediacy of a borohydride as the
actual reductant.21 The crucial step of the present catalysis, that
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̈
C
dx.doi.org/10.1021/om4002796 | Organometallics XXXX, XXX, XXX−XXX