Synthesis of organosilatranes via rhodium(I)-catalyzed silylation of organic iodides with hydrosilatrane

Article abstract of DOI:10.1055/s-2007-983890

The silylation of aryl and alkenyl iodides with hydrosilatrane in the presence of a rhodium(I) catalyst and DABCO provides the corresponding organosilatranes in good yield. The same catalyst system also enables the related coupling of hydrogermatrane. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2007-983890

2944
SHORT PAPER
Synthesis of Organosilatranes via Rhodium(I)-Catalyzed Silylation of Organic
Iodides with Hydrosilatrane
R
hodium-Catalyze
d
Si
i
lylation
k
of
A
ryl Iod
i
ides
w
ith Hyd
M
rosilatrane urata,* Hiroyuki Yamasaki, Kota Uogishi, Shinji Watanabe, Yuzuru Masuda
Department of Materials Science, Kitami Institute of Technology, 165 Koen-cho, Kitami, Hokkaido 090-8507, Japan
Fax +81(157)264973; E-mail: muratamk@mail.kitami-it.ac.jp
Received 6 June 2007
to explore the possibility of using hydrosilatrane (1)5 and
Abstract: The silylation of aryl and alkenyl iodides with hydro-
silatrane in the presence of a rhodium(I) catalyst and DABCO pro-
vides the corresponding organosilatranes in good yield. The same
catalyst system also enables the related coupling of hydroger-
matrane.
hydrogermatrane [3, N(CH2CH2O)3MX; M = Ge, X = H]9
as a metalloid source for the transition-metal-catalyzed
metalation of aryl halides.
As a test for the optimization of reaction parameters, hy-
drosilatrane (1) and 4-iodobenzotrifluoride (5) were se-
lected as reaction partners (Table 1). The reactions were
performed using 2 equivalents of 1 and 1 equivalent of 5
with 5 equivalents of base in N,N-dimethylformamide
at 80 °C. Initial examination revealed that 3 mol% of
Key words: silicon, rhodium, catalysis, cross-coupling, halides
Metallatranes of Group 14 elements, N(CH2CH2O)3MX,
such as silatranes (M = Si, 2,8,9-trioxa-5-aza-1-silabicy-
clo[3.3.3]undecane derivatives) and germatranes
(M = Ge), are important heterocyclic molecules with in-
teresting physical and chemical properties due to the M–
N transannular interaction (Figure 1).1,2 For example,
their potential application in palladium-catalyzed cross-
coupling reactions of organometallatranes has been re-
ported.3,4 The commonest method for the synthesis of
metallatranes is alcoholysis of the corresponding tri-
alkoxy derivatives using triethanolamine.4,5 Recently,
Miyaura and co-workers reported that an iridium-cata-
lyzed direct silylation of aromatic C–H bonds using hy-
drosilatrane [1, N(CH2CH2O)3MX; M = Si, X = H]
afforded arylsilatranes 2 (M = Si, X = Ar).6 Although the
C–H silylation is the most straightforward route, this is
somewhat problematic with regard to the control of regio-
selectivity.
a
rhodium catalyst, such as Rh(acac)(cod) or
[Rh(cod)(MeCN)2]BF4, can effect the transformation of 5
to the corresponding arylsilatrane 2a (entries 2 and 3), but
several attempts at silylation with palladium catalysts
were unsuccessful (entry 1). In addition to the desired 2a,
side products (reduced arene 6 and homocoupled biaryl 7)
were produced. Upon screening commonly used bases, it
was found that the use of DABCO is crucial to the success
of the silylation (entries 2 and 3). Both triethylamine and
DBU were considerably less effective for this coupling re-
action due to the extensive formation of 6 (entries 4 and
Table 1 Rhodium-Catalyzed Silylation of Aryl Iodide 5 with
Hydrosilatrane (1)a
O
O
Rh catalyst, base
DMF, 80 °C
N
N
Si
H
+
I
CF3
N(CH2CH2O)3M X
N
O
1
5
M = Si X = H (1)
,
M
X = Ar
(2)
O
O
O
O
O
M = Ge X = H (3)
,
X
CF3
CF3
+
Si
CF3
+
X = Ar (4)
2
O
2a
6
7
Figure 1 Metallatranes of group 14 elements
Entry Catalyst
Base
Yieldb (%)
Much attention has been focused on the coupling reaction
of metalloid hydrides with organic electrophiles as a
chemo- and regioselective method for the synthesis of or-
ganometalloids. We and others have demonstrated that ar-
yl(triethoxy)silanes, which are precursors of 2, can be
easily prepared using either a palladium or rhodium cata-
lyst.7,8 Based on our success in this area, we decided to ex-
pand the scope of the carbon–metalloid bond-formation
protocol to the synthesis of arylmetallatrane derivatives 2
and 4 (M = Si, Ge; X = Ar). The goal of this research was
2a
0
6
7
1
2
3
4
5
6
Pd(dba)2
Rh(acac)(cod)
DABCO
DABCO
DABCO
Et3N
100
21
0
7
72
53
4
[Rh(cod)(MeCN)2]BF4
[Rh(cod)(MeCN)2]BF4
[Rh(cod)(MeCN)2]BF4
[Rh(cod)(MeCN)2]BF4
29 18
58
59
3
2
DBU
4
K2CO3
18
38 43
a Reaction conditions: 5 (0.5 mmol), 1 (1 mmol), base (2.5 mmol), cat-
alyst (15 mmol), DMF (0.5 mL), 80 °C, 16 h.
b NMR yields based on 5.
SYNTHESIS 2007, No. 19, pp 2944–2946
Advanced online publication: 11.09.2007
DOI: 10.1055/s-2007-983890; Art ID: F10407SS
© Georg Thieme Verlag Stuttgart · New York
x
x.
x
x
.
2
0
0
7

SHORT PAPER
Rhodium-Catalyzed Silylation of Aryl Iodides with Hydrosilatrane
2945
5). The use of inorganic bases (entry 6) or other solvents10 In conclusion, hydrosilatrane (1) was found to undergo
inhibited the silylation. Thus, the use of DABCO in N,N- the rhodium(I)-catalyzed silylation of aryl iodides. Addi-
dimethylformamide was identified as the optimal reaction tionally, the present coupling can be applied to hydroger-
conditions, although we were unable to completely con- matrane (3) for the synthesis of arylgermatranes 4. Further
trol the selectivity of the products.
investigations to improve the selectivity, as well as to illu-
minate the reaction mechanism, are currently underway.13
The results obtained with representative aryl iodides, giv-
ing the corresponding arylsilatranes 2, are listed in
Table 2. The presence of functional groups, such as ester
(entry 1) and ketone carbonyl groups (entry 2), in the
starting aryl iodides did not interfere with the outcome of
the present reaction. Furthermore, not only aryl iodides
but also alkenyl iodides can be employed (entry 4).11 It is
noteworthy that the germylation of electron-deficient aryl
iodides with hydrogermatrane (3) proceeded under simi-
All experiments were carried out under a N2 atmosphere using
oven-dried glassware. NMR spectra were recorded on a JEOL
JNM-A500 spectrometer (1H, 500 MHz; 13C, 125 MHz). Mass spec-
tra were obtained at an ionization potential of 70 eV with a JEOL
JMS-SX102 spectrometer.
Synthesis of 1-Arylsilatranes (1-Aryl-2,8,9-trioxa-5-aza-1-sila-
bicyclo[3.3.3]undecanes) 2; General Procedure
lar reaction conditions (entries 5 and 6), as no example of Rh(acac)(cod) (15 mmol), hydrosilatrane (1; 1.0 mmol), and
DABCO (2.5 mmol) were placed in a test tube capped with a rubber
the palladium-catalyzed germylation of such aryl iodides
with tri(2-furyl)germane was reported.12
septum. The test tube was flushed with N2 and then charged with
DMF (0.5 mL). Then, an aryl iodide (0.5 mmol) was added. The re-
action mixture was stirred at 80 °C for 16 h, then the mixture was
diluted with CH2Cl2 (5 mL), washed with H2O (5 mL), and dried
Table 2 Synthesis of Arylmetallatrane Derivatives 2 and 4a
(Na2SO4). The solvent was removed under reduced pressure, and
the residue was poured into hexane–toluene (10:1, 3 mL) and stirred
for 2 h at r.t. Filtration and drying afforded the analytically pure
product 2 as a white solid.
O
O
O
O
Rh catalyst, DABCO
DMF, 80 °C
N
M
H
+
I
R
N M R
O
O
M = Si (1), Ge (3)
M = Si (2), Ge (4)
2a
Entry
Product
Catalystb Yieldc (%)
1H NMR (500 MHz, CDCl3): d = 2.96 (t, J = 5.9 Hz, 6 H), 3.92 (t,
J = 5.9 Hz, 6 H), 7.49 (d, J = 7.9 Hz, 2 H), 7.84 (d, J = 7.9 Hz, 2 H).
13C NMR (125 MHz, CDCl3): d = 50.71, 57.35, 123.40 (q, J = 4
Hz), 124.65 (q, J = 270 Hz), 129.00 (q, J = 31 Hz), 134.37, 147.89.
HRMS (EI): m/z [M+] calcd for C13H16F3NO3Si: 319.0852; found:
319.0807.
O
O
N
N
Si
CO2Et
COMe
1
2
3
4
5
6
A
A
A
B
B
B
67
83
74
83
52
48
O
2b
2c
2d
2e
4a
4b
O
O
2b
Si
1H NMR (500 MHz, CDCl3): d = 1.37 (t, J = 7.2 Hz, 3 H), 2.95 (t,
J = 5.9 Hz, 6 H), 3.92 (t, J = 5.9 Hz, 6 H), 4.34 (q, J = 7.2 Hz, 2 H),
7.80 (d, J = 7.9 Hz, 2 H), 7.93 (d, J = 7.9 Hz, 2 H).
O
13C NMR (125 MHz, CDCl3): d = 14.33, 51.06, 57.62, 60.49,
128.13, 129.34, 134.08, 148.53, 167.45.
HRMS (EI): m/z [M+] calcd for C15H21NO5Si: 323.1189; found:
323.1205.
O
O
O
O
O
N
N
N
N
Si
Br
O
2c
O
1H NMR (500 MHz, CDCl3): d = 2.56 (s, 3 H), 2.96 (t, J = 5.9 Hz,
6 H), 3.93 (t, J = 5.9 Hz, 6 H), 7.83 (d, J = 8.5 Hz, 2 H), 7.85 (d,
J = 8.5 Hz, 2 H).
Si
Ph
O
13C NMR (125 MHz, CDCl3): d = 26.66, 51.06, 57.60, 126.95,
134.33, 136.17, 149.31, 199.13.
HRMS (EI): m/z [M+] calcd for C14H19NO4Si: 293.1083; found:
293.1102.
O
Ge
CF3
O
2d
1H NMR (500 MHz, CDCl3): d = 2.93 (t, J = 5.9 Hz, 6 H), 3.90 (t,
J = 5.9 Hz, 6 H), 7.38 (d, J = 8.5 Hz, 2 H), 7.59 (d, J = 7.9 Hz, 2 H).
O
Ge
CO2Et
13C NMR (125 MHz, CDCl3): d = 51.04, 57.61, 122.35, 130.22,
135.94, 141.03.
O
HRMS (EI): m/z [M+] calcd for C12H16BrNO3Si: 331.0062; found:
331.0110.
a Reaction conditions: RI (0.5 mmol), 1 or 3 (1 mmol), DABCO (2.5
mmol), catalyst (15 mmol), DMF (0.5 mL), 80 °C, 16 h.
b A: Rh(acac)(cod), B: [Rh(cod)(MeCN)2]BF4.
c Isolated yields.
Synthesis 2007, No. 19, 2944–2946 © Thieme Stuttgart · New York

2946
2e
M. Murata et al.
SHORT PAPER
References
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4b
1H NMR (500 MHz, CDCl3): d = 1.38 (t, J = 7.0 Hz, 3 H), 2.95 (t,
J = 5.6 Hz, 6 H), 3.91 (t, J = 5.6 Hz, 6 H), 4.35 (q, J = 7.0 Hz, 2 H),
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MeCN, 0 (100); dioxane, 38 (100); DCE, 0 (8); toluene,
trace (27).
Acknowledgment
This work was partially supported by a Grant-in-Aid for Scientific
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Creation of Functional Molecules) from the Ministry of Education,
Culture, Sports, Science and Technology, Japan.
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the present situation.
Synthesis 2007, No. 19, 2944–2946 © Thieme Stuttgart · New York