Palladium-catalyzed metathesis of phenylalkyl- or chloroalkyldigermanes with allylic chlorides at room temperature

Article abstract of DOI:10.1016/S0022-328X(97)00651-7

Metathesis of phenylalkyldigermanes (1,2-diphenyltetraethyl-, 1,2-diphenyltetramethyl-, phenylpentaethyl- or phenylpentamethyldigermane) or chloroalkyldigermanes (1,2-dichlorotetraethyl- or 1,2-dichlorotetramethyldigermane) with allylic chlorides proceeds

Full text of DOI:10.1016/S0022-328X(97)00651-7

Ž
.
Journal of Organometallic Chemistry 553 1998 493–496
Preliminary communication
Palladium-catalyzed metathesis of phenylalkyl- or
chloroalkyldigermanes with allylic chlorides at room temperature
a
a
a
b
Taichi Nakano a,), Tatsuki Enokido , Sigeyuki Noda , Nao-aki A-ihara , Masanori Kosugi ,
a,1
Toshihiko Migita
a
Department of Material Science and Technology, School of High-Technology for Human Welfare, Tokai UniÕersity, 317 Nishino, Numazu,
Shizuoka 410-03, Japan
b
Department of Chemistry, Faculty of Engineering, Gunma UniÕersity, Kiryu, Gunma 376, Japan
Received 1 July 1997; received in revised form 1 September 1997
Abstract
Ž
Metathesis of phenylalkyldigermanes 1,2-diphenyltetraethyl-, 1,2-diphenyltetramethyl-, phenylpentaethyl- or phenylpentamethyldiger-
.
Ž
.
mane or chloroalkyldigermanes 1,2-dichlorotetraethyl- or 1,2-dichlorotetramethyldigermane with allylic chlorides proceeds smoothly
Ž
.
Ž .
even at room temperature in the presence of tris dibenzylideneacetone dipalladium 0 to afford the corresponding 2-alkenylgermanes in
good to high yields. q 1998 Elsevier Science S.A.
Keywords: Germanium; Digermane; Palladium-catalysis; Metathesis; Allylgermanes
w x
except for our recent report 9 , although the reactions
1. Introduction
w
x
w x
of bromobenzene 10,11 , benzyl chloride 11 or styryl
w x Ž
.
Palladium-catalyzed metathesis of group 14 bimetal-
lic compounds with allylic halides or esters is one of the
important methods to prepare allylated 14 metallic
compounds. In fact, disilanes have been reported to
undergo the metathesis with allylic chlorides or esters in
the presence of Pd PPh3 5 or Pd P OPh
bromide 11 in the presence of Pd PPh3 have been
4
Ž
.
published. In 1996, we reported that Pd2 dba effected
3
2
the metathesis of hexaethyl-digermane with allylic
halides to produce allylgermanes with a good regiose-
w x
lectivity 9 . However, it required vigorous reaction
Ž
.
w x
Ž Ž
. . w x
6 . Tsuji
Ž
.
conditions 1708C to ensure the reaction. Therefore, it
is desirable to search for the milder reaction conditions.
Thus, we tried to enhance the reactivity of the diger-
4
3 4
w x
2
et al.
7
have recently reported that the use of
Ž
.
Pd dba –LiCl combination catalyst made the condi-
Ž .
tions in the metathesis of hexamethyldisilane with al-
lylic acetates much milder than those of previously
reported. Quite recently, they also reported that when
allylic trifluoroacetates were used instead of allylic
acetates, the reaction proceeded at room temperature in
mane by selecting substituent s on germanium. After
several trials, we have found that, quite interestingly,
the germanium–germanium bond of digermanes such as
1,2-diphenyltetraethyldigermane 1, 1,2-diphenyltetra-
methyldigermane 2, phenylpentaethyldigermane 3,
phenylpentamethyldigermane 4, 1,2-dichlorotetraethyl-
digermane 5 and 1,2-dichlorotetramethyl-digermane 6
was easily cleaved without heating or additive such as
Ž
.
the presence of Pd dba to give allylsilanes in good
2
w x
yields 8 . On the other hand, little attention has been
paid to the reaction of digermanes with allylic halides
Ž
.
LiCl in the presence of a catalytic amount of Pd2 dba
3
and reacted with allylic chlorides to give corresponding
allylgermanes in good yields. To our knowledge, there
is no reports that palladium-catalyzed reaction of diger-
manes with organic halides proceeds even at room
temperature.
)
Corresponding author.
1 Retired, March 31, 1997.
2
w
x
For allylgermanes: see Refs. 1–4
0022-328Xr98r$19.00 q 1998 Elsevier Science S.A. All rights reserved.

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)
494
T. Nakano et al.rJournal of Organometallic Chemistry 553 1998 493–496
2. Results and discussion
manes in good yields. Results are summarized in Table
1.
The reaction of 2 with trans-cinnamyl chloride in the
As shown in Table 1, the palladium-catalyzed reac-
Ž
.
Ž .
tion of 1 with crotyl chloride entry 1 gave a mixture of
presence of 1 mol% of tris dibenzylideneacetone dipal-
Ž .
Ž . Ž
crotyldiethylphenylgermane 78% and 1-methylprop-
ladium 0 in benzene proceeded smoothly at room tem-
. Ž .
2-enyl diethylphenylgermane 10% and with 3-chloro-
perature to produce trans- and cis-cinnamyl-
dimethylphenylgermane in 96% and 3% yields based on
the digermane consumed, respectively, while no reac-
tion took place without the palladium catalyst. The
Ž
.
but-1-ene entry 2 the same products were also pro-
duced in 82% and 16% based on the digermane con-
sumed, respectively. It suggests that the reactions seem
to proceed through a similar intermediate. On the other
hand, digermane 1 reacted with prenyl chloride to give
only prenyldiethylphenylgermane in 80% yield. The
metathesis of 1 with trans-cinnamyl chloride similarly
proceeded to give trans- and cis-cinnamyl-
diethylphenylgermane in 90% and 10% yields based on
the digermane consumed. In these reactions, high re-
gioselectivity was observed.
Ž
formation of another expected product, 1-phenylprop-
.
2-enyl dimethylphenylgermane, was not observed by
GLC analysis. The results encouraged us to examine the
reaction of other digermanes such as 1, 3, 4, 5 and 6.
These digermanes reacted with various allylic chlorides
such as crotyl chloride, 3-chlorobut-1-ene, prenyl chlo-
ride or methallyl chloride as well as cinnamyl chloride
at room temperature to give the corresponding allylger-
Table 1
X
a
Ž
.
Palladium-catalyzed reaction of digermanes XR2GeGeR2 X with allylic chlorides
Entry
1
R
X
XX Halide
Timerhb Solvent Conversionr%c Productr%d
Ph Ph CH3CH5CHCH2Cle
15
25
17
PhH
96
trans- and cis-CH3CH5CHCH2GeEt2 Ph 78
CH2 5CHCH GeEt2 Ph CH3 10
trans- and cis-CH3CH5CHCH2GeEt2 Ph 82
Ž
.
.
Et
Ž
.
Ž .
Ž
2
Et
Ph Ph CH2 5CHCHClCH3
PhH
93
Ž
.
Ž .
Ž .
CH2 5CHCH GeEt2 Ph CH3 16
Ž
.
Ž
.
3
4
Et
Et
Ph Ph
CH3 2C5CHCH2Cl
none
PhH
100
93
CH3 2C5CHCH2GeEt2 Ph 80
Ž .
trans-PhCH5CHCH2GeEt2 Ph 90
Ph Ph trans-PhCH5CHCH2Cl 15
Ž
.
cis-PhCH5CHCH2GeEt2 Ph 10
trans- and cis-CH3CH5CHCH2GeMe2 Ph 70
Ž .
CH3 2C5CHCH2GeMe2 Ph 61
trans-PhCH5CHCH2GeMe2 Ph 96
Ž
.
5
Me Ph Ph CH2 5CHCHClCH3
4
PhH
100
Ž
.
CH2 5CHCH GeMe2 Ph CH3
9
Ž
.
Ž
.
Ž .
6
7
Me Ph Ph
Me Ph Ph trans-PhCH5CHCH2Cl
CH3 2C5CHCH2Cl
15
1
none
PhH
100
94
Ž
.
Ž .
cis-PhCH5CHCH2GeMe2 Ph 3
Ph Et CH3CH5CHCH2Cle
Ph Et CH2 5CHCHClCH3
17
16
PhH
PhH
72
77
trans- and cis-CH3CH5CHCH2GeEt2 Ph 92
CH2 5CHCH GeEt2 Ph CH3 2.3
trans- and cis-CH3CH5CHCH2GeEt2 Ph 84
Ž
.
.
8
9
Et
Et
Et
Ž
.
Ž
.
Ž
Ž
.
Ž
.
CH2 5CHCH GeEt2 Ph CH3 1.8
Ž
.
Ž
.
Ž .
10
11
12
13f
Ph Et
CH3 2C5CHCH2Cl
18
17
16
none
PhH
PhH
PhH
100
86
95
CH3 2C5CHCH2GeEt2 Ph 68
Me Ph Me CH3CH5CHCH2Cle
Me Ph Me CH2 5CHCHClCH3
trans- and cis-CH3CH5CHCH2GeMe2 Ph 55
Ž
trans- and cis-CH3CH5CHCH2GeMe2 Ph 40
Ž .
trans-PhCH5CHCH2GeMe2 Ph 86
Ž
.
.
Me Ph Me trans-PhCH5CHCH2Cl 16
96
Ž
.
cis-PhCH5CHCH2GeMe2 Ph 14
Cl Cl CH3CH5CHCH2Cle
Cl Cl CH2 5CHCHClCH3
Cl Cl trans-PhCH5CHCH2Cl 62
17
16
none
none
PhH
100
100
100
trans- and cis-CH3CH5CHCH2GeEt2Cl 46
trans- and cis-CH3CH5CHCH2GeEt2Cl 65
trans-PhCH5CHCH2GeEt2Cl 80
Ž
Ž
.
.
14
15
16
Et
Et
Et
Ž .
.
Ž
cis-PhCH5CHCH2GeEt2Cl 1.8
Ž .
trans- and cis-CH3CH5CHCH2GeMe2Cl 75
Ž
.
PhCH GeEt2Cl CH5CH2
4
Me Cl Cl CH3CH5CHCH2Cle
Me Cl Cl CH2 5CHCHClCH3
Me Cl Cl
Me Cl Cl CH2 5C CH3 CH2Cl
Me Cl Cl trans-PhCH5CHCH2Cl
11
11
14
16
7
PhH
PhH
PhH
PhH
PhH
90
100
98
100
100
Ž
Ž
.
.
17
18
19
20
21
trans- and cis-CH3CH5CHCH2GeMe2Cl 55
Ž
.
Ž
.
Ž .
CH3 2C5CHCH2Cl
CH3 2C5CHCH2GeMe2Cl 80
Ž
.
Ž
.
Ž
.
CH2 5C CH3 CH2GeMe2Cl quant.
Ž
.
trans-PhCH5CHCH2GeMe2Cl 70
Ž .
cis-PhCH5CHCH2GeMe2Cl 2
Ž
.
Ž
.
PhCH GeMe2Cl CH5CH2 1.8
a
Ž
.
Ž
.
Ž
.
Ž
.
Ž
.
Conditions: digermane 0.5 mmol , allylic chloride 1 mmol , Pd2 dba 3 PCHCl3 0.005 mmol and solvent 1 ml , at room temperature.
bReaction time was not optimized.
cConversion of the digermane.
dGLC yields based on the digermane consumed.
etrans- and cis-isomeric mixture.
f
Ž
.
Ž
.
Ž
.
Ž
.
Ž
.
Conditions: digermane 0.5 mmol , allylic chloride 0.5 mmol , Pd2 dba 3 PCHCl3 0.01 mmol and PhH 1 ml .

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T. Nakano et al.rJournal of Organometallic Chemistry 553 1998 493–496
495
Scheme 1.
It should be noted that the metathesis occurred at
room temperature even in the reaction of monopheny-
lated digermanes. Entries 8 through 13 show the results
for the reactions of phenylpentaalkyldigermanes 3 and
4. In these cases, there are two possible products ex-
pected; one of which is the allylated phenyldialkylger-
mane, and the other is allylated trialkylgermane. In
these reactions, 2-alkenyldialkylphenylgermane was a
predominant product. Actually, the reaction of 3 with
crotyl chloride smoothly proceeded to afford
clear yet. Metallylchlorodimethylgermane was formed
in the reaction of 6 with methallyl chloride in quantita-
Ž
.
tive yield entry 20 . Digermane 5 also entered into the
Ž
.
reaction with cinnamyl chloride to form trans- 80%
and cis-cinnamylchlorodiethylgermane 1.8% and 1-
phenyl-prop-2-enyl chlorodiethylgermane 4% based on
the digermane consumed entry 16 . A similar reaction
Ž
.
.
Ž
.
Ž
Ž
.
of 6 gave the corresponding products in 70%, 2% and
Ž
.
1.8% yields, respectively entry 21 . High regioselectiv-
ities were also observed for these reactions.
Ž
crotyldiethylphenylgermane and 1-methylprop-2-
From the results of Scheme 2, it is easy to assume
the formation of the same p-allylpalladium chloride
intermediate which derived from the reaction of
.
enyl diethylphenylgermane in 92% and 2.3% yields,
Ž
.
respectively entry 8 , as shown in Scheme 1.
Ž
.
A similar reaction with 3-chlorobut-1-ene also gave
the same products in 84% and 1.8% yields, respectively
Pd2 dba with crotyl chloride or 3-chlorobut-1-ene at
3
w
x
room temperature 12 . So we examined the reaction of
p-allylchloropalladium dimer with 1,2-diphenyltetra-
Ž
.
Ž
.
entry 9, Scheme 1 . Phenylpentamethyldigermane re-
acted with cinnamyl chloride to produce trans- and
cis-cinnamyldimethylphenylgermane in 86% and 14%
yields based on the digermane consumed, respectively
methyldigermane in benzene at room temperature and
found the reaction reached to completion for 30 min
giving allylphenyldimethylgermane in quantitative yield
Ž
.
Ž
.
Ž
.
entry 13 . The results for the selective formation of
Scheme 2 . In addition, the reaction of Pd2 dba with
3
2-alkenyldialkylphenylgermanes are well consistent with
those reported for the metathesis of phenylpentamethyl-
the digermane 2 was extremely slow at room tempera-
ture compared to that of the Pd-dibenzylideneacetone
complex with an allylic chloride. Thus, stirring a ben-
w x
disilane with allylic acetates 8 .
Ž
.
1,2-Dichlorinated digermanes were also subject to
the metathesis with allylic chlorides at room tempera-
ture. Entries 14 through 21 show the results for the
reaction of digermanes 5 and 6. The metathesis of 5 or
6 with crotyl chloride or 3-chlorobut-1-ene gave regios-
electively the corresponding crotylchlorodiethylger-
zene solution of equimolecular amounts of Pd2 dba
3
and 2 for 10 h did not cause any reaction, although 16%
of 2 was consumed after 72 h. Consequently, the mech-
anism for the reactions seems to be interpreted by the
well-known oxidative addition and reductive elimina-
Ž
.
tion processes Fig. 1 . In addition, it should be empha-
sized that the metathesis of the digermane bearing phenyl
Ž .
Ž . Ž
mane s or crotylchlorodimethylgermane s entries 14
.
Ž .
and 17 , while the reactions of phenyldigermanes 1 and
or chloro substituent s proceeds smoothly even at room
Ž
3 were accompanied by the formation of 1-methylprop-
temperature, although the activating effect of phenyl or
.
Ž
.
Ž .
2-enyl germanes entries 1 and 8 . The reason is not
chloro substituent s to a metal–metal bond in group 14
Scheme 2.

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496
T. Nakano et al.rJournal of Organometallic Chemistry 553 1998 493–496
collected sample. Spectral data for the sample are as
Ž
.
follows: IR neat : 3050, 3005, 2970, 2900, 1640, 1595,
1495, 1425, 1235, 1135, 1095, 960, 800, 745, 730, 695
1
cmy1. H NMR CDCl3, 400 MHz : d 0.41 and 0.43 s,
Ž
.
Ž
.
Ž
.
s, 6H , 2.03 and 2.04 dd, 1.78 H, Js4.8, 2.8 Hz, ,
Ž
.
Ž
Ž
2.19–2.21 dd, 0.27 H, Js9.2, 1.2 Hz , 2.63 m, 0.01
.
Ž
.
H , 5.04–5.09 m, 0.02 H , 5.71–5.79 dt, 0.11H, Js
.
Ž
.
Ž
11.6, 9.2 Hz , 6.25–6.28 m, 1.86H , 7.15–7.49 m,
q
P
.
Ž
.
Ž
w
xq
10H . EIMS: 298 M , 181 My CH2CH5CHPh ,
.
base peak .
Acknowledgements
We thank Asai Germanium Research Institute for
supplying tetrachlorogermane.
Fig. 1. A plausible mechanism in the formation of allylgermanes.
References
w
x
bimetallics such as disilanes has been reported 5,8,13 .
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the present reaction are now in progress.
w x
Ž
.
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yldigermane 0.5 mmol , trans-cinnamyl chloride 1
mmol and Pd2 dba . CHCl3 0.005 mmol was stirred
at room temperature. The reaction was traced with a gas
chromatograph. After 1 h, a 94% of the digermane was
consumed and trans-cinnamyldiethylphenylgermane and
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on the digermane consumed, respectively. However, H
NMR analysis of a mixture of the products collected
with GLC column; silicone KF-96, 10% on celite 545
AW disclosed that the products consisted of trans-iso-
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Ž
.
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