Homolytic hydrogermylation of alkenes with dibutylchlorogermane

Article abstract of DOI:10.1016/j.jorganchem.2006.04.043

In the presence of Et₃B-dry air, dibutylchlorogermane (Bu₂GeClH) reacted smoothly with alkenes at room temperature to give hydrogermylation products in high yields. This homolytic hydrogermylation was applicable to various alkenes in

Full text of DOI:10.1016/j.jorganchem.2006.04.043

Journal of Organometallic Chemistry 692 (2007) 514–519
www.elsevier.com/locate/jorganchem
Homolytic hydrogermylation of alkenes with dibutylchlorogermane
a,
a
b,
*
Katsukiyo Miura *, Kazunori Ootsuka , Akira Hosomi
a
Department of Chemistry, 21st Century COE, Graduate School of Pure and Applied Sciences, University of Tsukuba, and CREST,
Japan Science and Technology Corporation (JST), Tsukuba, Ibaraki 305-8571, Japan
Faculty of University Evaluation and Research, National Institution for Academic Degrees and University Evaluation, Kodaira, Tokyo 187-8587, Japan
b
Received 2 March 2006; received in revised form 25 April 2006; accepted 27 April 2006
Available online 30 August 2006
Abstract
In the presence of Et3B-dry air, dibutylchlorogermane (Bu2GeClH) reacted smoothly with alkenes at room temperature to give
hydrogermylation products in high yields. This homolytic hydrogermylation was applicable to various alkenes including electron-defi-
cient, electron-rich, and internal alkenes. Under the same conditions, tributylgermane (Bu3GeH) showed much lower reactivity than
Bu2GeClH. The Et3B-initiated reaction of 1,6-dienes with Bu2GeClH gave germylmethylated cyclopentanes.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Hydrogermane; Hydrogermylation; Alkenes; Radical reactions
1. Introduction
achieved by low reversibility of the radical addition step
and fast hydrogen abstraction of the alkyl radical interme-
diate. A few kinds of group 14 metal hydrides are known to
satisfy these requirements in hydrometalations of both
unactivated and activated alkenes. For example, tris(trim-
ethylsilyl)silane ((Me3Si)3SiH) [4], tri(2-furyl)germane ((2-
furyl)3GeH) [5], and dialkylhalostannanes (R2SnXH) [6]
are valuable for efficient, mild homolytic hydrometalations
of a wide range of alkenes.
In the course of our studies on highly selective homolytic
hydrostannylations of alkenes and alkynes with Lewis acidic
hydrostannanes [7], we found that dibutylchlorostannane
(Bu2SnClH) added exclusively to 1-undecen-3-ol in the
coexistence of 1-octene (Eq. (1)) [7a]. The high chemoselec-
tivity is attributable to the coordination of the hydroxy
group to the Lewis acidic tin nucleus in the b-stannylalkyl
radical intermediate (Scheme 2). The Sn–O coordination
would retard the decomposition (inverse reaction) of the
intermediate to Bu2ClSnÆ and the substrate to promote the
hydrostannylation process. This chemoselective hydrostan-
nylation with Bu2SnClH induced us to investigate the reac-
tivity of dibutylchlorogermane (Bu2GeClH, 1a), a Lewis
acidic hydrogermane, toward homolytic hydrogermylation
of alkenes [8]. Herein we describe that 1a adds smoothly
to a variety of alkenes in the presence of Et3B-dry air.
Hydrometalation reactions of alkenes with hydrosilanes,
-germanes, and -stannanes provide powerful tools for the
synthesis of alkylsilanes, -germanes, and -stannanes,
respectively [1–3]. Radical initiators and transition metal
catalysts are well known to be effective in acceleration of
these hydrometalations. The propagation mechanism of
the radical-initiated hydrometalations involves reversible
addition of a metal radical and hydrogen abstraction of
the resultant alkyl radical from a metal hydride (Scheme
1). The radical process is applicable to various alkenes
due to high reactivity of the radical species as well as high
compatibility with polar functionalities. However, there are
some drawbacks such as severe reaction conditions, low
reaction efficiency caused by side radical reactions, and
low stereoselectivity, particularly, in the reactions using tri-
alkylmetal hydrides (R3MH, R = alkyl, M = Si, Ge, Sn).
Judging from the reaction mechanism, an efficient homo-
lytic hydrometalation under mild conditions can be
*
Corresponding authors. Tel.: +81 29 853 4486; fax: +81 29 853 6503
(K. Miura); fax: +81 42 353 1805 (A. Hosomi).
E-mail addresses: miura@chem.tsukuba.ac.jp (K. Miura), hosomi@
chem.tsukuba.ac.jp (A. Hosomi).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.04.043

K. Miura et al. / Journal of Organometallic Chemistry 692 (2007) 514–519
515
Table 1
Hydrogermylation of allyl alcohol 2a with 1aa
Entry
Solvent
Time
Isolated yield (%)
1b
2
THF
5 min
10 h
3 h
5 min
24 h
1 h
99
96
90
97
0
0
37
0
Hexane
Toluene
Neatc
Neatc
THF
3
4b
5d
6e
7f
8g
a
Scheme 1.
THF
THF
24 h
24 h
Unless otherwise noted, all reactions were carried out with 2a
(0.50 mmol), 1a (0.60 mmol), Et3B (1 M in hexane, 0.025 mmol), dry air
(2.5 mL), and solvent (1.0 mL). The mixture was stirred for 10 min at 0 ꢁC
and then warmed to rt. The resultant mixture was treated with BuMgBr/
Et2O (1.5 mmol) in entries 1, 4, and 5 or BuLi/hexane (1.2 mmol) in
entries 2, 3, and 6.
Scheme 2.
b
The reaction was carried out at 0 ꢁC.
c
The reaction mixture contained a small amount of hexane coming
from 1 M solution of Et3B.
d
Without Et3B-dry air.
With galvinoxyl (0.025 mmol).
Bu2Ge(OEt)H (1b) was used instead of Bu2GeClH.
Bu3GeH (1c) was used instead of Bu2GeClH.
e
f
ð1Þ
g
(Table 1). In the presence of Et3B-dry air as radical initiator
[11], the reaction of 2a with 1a in THF at 0 ꢁC reached com-
pletion within 5 min. Treatment of the resultant mixture
with BuMgBr gave 3-tributylgermyl-1-propanol (3a) in a
quantitative yield after purification by silica gel column
chromatography (entry 1) [12]. Use of hexane and toluene
as solvent decreased the reaction rate, although prolonged
reaction achieved high yields of 3a (entries 2 and 3). Without
solvent, the hydrogermylation proceeded rapidly and effi-
ciently (entry 4). Hydrogermane 1a did not add to 2a in
the absence of Et3B-dry air (entry 5). Addition of galvinoxyl
suppressed the Et3B-initiated reaction completely (entry 6).
The results of entries 5 and 6 clearly indicate that the present
hydrogermylation involves a radical chain mechanism. The
reaction with dibutyl(ethoxy)germane (Bu2Ge(OEt)H, 1b)
was much slower than that with 1a (entries 1 and 7) [8]. Trib-
utylgermane (Bu3GeH, 1c) was insensitive to 2a even in the
presence of Et3B-dry air (entry 8). Thus, introduction of a
chloro group on the germanium atom is very effective in
improving the reactivity of hydrogermanes [8].
2. Results and discussion
2.1. Synthesis of dibutylchlorogermane (1a)
Hydrogermane 1a was prepared from GeCl4 by four
steps without difficulty (Scheme 3) [9]: butylation of GeCl4
with BuMgBr, dealkylative dichlorination of Bu4Ge with
AcCl and AlCl3, reduction of Bu2GeCl2 with LiAlH4,
and chlorination of Bu2GeH2 with CuCl2 [10].
2.2. Optimization of reaction conditions using 2-propen-1-ol
(2a)
We first examined the radical-initiated hydrogermylation
of 2-propen-1-ol (2a) with 1a under various conditions
2.3. Hydrogermylation of various alkenes
The Et3B-initiated hydrogermylation with 1a is applica-
ble to various alkenes as shown in Table 2. 1-Undecen-3-ol
(2b) and 2-methyl-2-propen-1-ol (2c) as well as 2a under-
went the hydrogermylation efficiently (entries 1–3).
Scheme 3.

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K. Miura et al. / Journal of Organometallic Chemistry 692 (2007) 514–519
Table 2
Hydrogermylation of alkenes 2 with 1aa
Entry
R1
R2
R3
Time
BuM (equiv)
Isolated yield (%)
1b
2
3
4
5
6
7c
8c
9d
10d
a
HOCH2
n-C8H17CH(OH)
HOCH2
n-C9H19
BuO
CyO2C
CyO2C
MeO2C
Pr
H
H
Me
H
H
H
H
H
H
H
H
H
H
H
H
H
H
2a
2b
2c
2d
2e
2f
5 min
30 min
30 min
30 min
30 min
30 min
10 h
10 h
1 h
1 h
BuMgBr (3)
BuLi (2.4)
BuMgBr (3)
BuLi (1.2)
99
94
99
97
82
59
86
82
92
80
BuLi (1.2)
BuMgBr (1.2)
BuMgBr (1.2)
BuMgBr (1.2)
BuLi (1.3)
2f
2g
2h
2i
Pr
(CH2)4
Me3SiO
(CH2)4
BuLi (1.3)
Unless otherwise noted, all reactions were carried out with an alkene 2 (0.50 mmol), 1a (0.60 mmol), Et3B (1 M in hexane, 0.025 mmol), and dry air
(2.5 mL) in THF (1.0 mL). The mixture was stirred for 10 min at 0 ꢁC and then warmed to rt. The resultant mixture was treated with BuMgBr/Et2O or
BuLi/hexane.
b
The reaction was carried out at 0 ꢁC.
Instead of THF, hexane was used as solvent.
The reaction was carried out without solvent, although a small amount of hexane coming from 1 M solution of Et3B was contained.
c
d
Hydrogermane 1a reacted smoothly with 1-undecene (2d),
a non-functionalized alkene, to give the corresponding
hydrogermylation product in 97% yield (entry 4). Under
the same conditions, 1a was reactive also to vinyl ether
2e, an electron-rich alkene (entry 5). Use of electron-defi-
cient alkene 2f resulted in a low yield of the corresponding
adduct 3f (entry 6). The hydrogermylation of 2f was not
completed, and elongation of the reaction time was not
effective in further consumption of 2f. However, prolonged
hydrogermylation of 2f and methyl acrylate (2g) in hexane
achieved high efficiency (entries 7 and 8). To our surprise,
the present method using 1a succeeded in efficient hydrog-
ermylation of internal alkenes such as (E)-4-octene (2h) and
1-(trimethylsiloxy)cyclohexene (2i) under solvent-free con-
ditions (entries 9 and 10) [13]. In THF, 1a did not add to
these alkenes at all.
We next tried radical cyclization of dienes with 1a. Use of
1,6-heptadiene (5a) afforded the cyclized product 6a in good
yield with moderate cis-selectivity (Scheme 5). Introduction
of methoxymethyl groups slightly improved the yield and
the stereoselectivity. This radical cyclization proceeds via
radical intermediate 7. The observed cis-selectivity can be
To disclose the chemoselectivity of the present hydroge-
rmylation, we performed competitive reaction of 2b and 2d
with 1a (2b:2d:1a = 1:1:1.1, Eq. (2)). Hexane, a non-coordi-
nating solvent, was used in view of the ease of coordination
between the hydroxy group and the germanium center.
However, the hydrogermylation gave a mixture of 3b and
3d with low chemoselectivity. This observation stands in
sharp contrast with the previous result shown in Eq. (1).
The difference between 1a and Bu2SnClH in chemoselectiv-
ity may arise from high bond energy of carbon–germanium
bond [14], which decelerates the elimination of Bu2ClGeÅ
from the b-germylalkyl radical intermediates 4 to facilitate
the radical chain process irrespective of the presence of the
hydroxy group (Scheme 4).
Scheme 4.
ð2Þ
Scheme 5.

K. Miura et al. / Journal of Organometallic Chemistry 692 (2007) 514–519
517
rationalized by cyclization through chair-equatorial confor-
mation A of 7, which is energetically more favored than
boat-equatorial and chair-axial conformations, B and C,
leading to trans-6 [15].
and evaporated. Purification of the crude product by distil-
lation gave the title compound (13.6 g, 60.9 mmol) in 92%
yield. Bp 114 ꢁC (2.3 Torr). IR (neat) 2958, 2929, 2860,
1
2058, 1464 cmꢀ1; H NMR (C6D6) d 0.85 (t, J = 7.3 Hz,
Previously we have reported that 1a acts as a good rad-
ical reducing agent and has higher hydrogen-donating abil-
ity to an alkyl radical than 1b and 1c [8]. Judging from this
observation, the high reactivity of 1a toward homolytic
hydrogermylation is attributable to its high hydrogen-
donating ability, which promotes the latter step of the
propagation process (Schemes 1 and 4). Additionally, in
the hydrogermylation of unactivated and electron-rich alk-
enes, the relatively electrophilic character of Bu2ClGeÅ
would facilitate its addition to these alkenes.
6H), 0.91–1.10 (m, 4H), 1.81–1.31 (m, 4H), 1.37–1.48 (m,
4H), 5.50 (tt, J = 2.7, 1.9 Hz, 1H); 13C NMR (C6D6) d
13.73 (CH3 · 2), 18.67 (CH2 · 2), 25.58 (CH2 · 2), 26.79
(CH2 · 2); MS m/z (relative intensity) 224 (M+, 1.3), 222
(M+ – 2, 1.5), 220 (M+ – 4, 1.3), 57 (100). Anal. Calc.
for C8H19GeCl: C, 43.03; H, 8.59. Found: C, 42.90; H,
8.45%.
4.2. Et3B-Initiated hydrogermylation of alkenes followed by
butylation
3. Conclusion
Under a nitrogen atmosphere, Et3B (1.0 M in hexane,
0.025 mL, 0.025 mmol) and dry air (2.5 mL) were added
to a solution of Bu2GeClH (1a, 134 mg, 0.60 mmol) and
allyl alcohol 2a (30 mg, 0.50 mmol) in THF (1 mL) at
0 ꢁC. After being stirred for 5 min, the resultant mixture
was treated with BuLi (1.60 M in hexane, 0.93 mL,
1.5 mmol) and stirred for 10 min. The mixture was poured
into saturated aqueous NH4Cl (10 mL). The extract with t-
BuOMe (3 · 10 mL) was dried over Na2SO4 and evapo-
rated. Purification of the crude product by silica gel column
chromatography gave 3-tributylgermyl-1-propanol (3a,
150 mg, 0.495 mmol) in 99% yield.
We have demonstrated that Bu2GeClH (1a) acts as an
efficient hydrogermylating agent. With this reagent, a vari-
ety of alkenes can be converted into the corresponding alkyl-
germanes in good to high yields. The present study has
disclosed also that a proper change of the substituent on ger-
manium makes hydrogermanes synthetically more useful.
4. Experimental
Unless otherwise noted, all reactions and distillations
were carried out under N2. Solvents were dried by distilla-
tion from sodium metal/benzophenone ketyl (THF, Et2O,
toluene) and CaH2 (hexane). All other commercially
obtained reagents were used as received. Infrared spectra
were measured on a JASCO FT/IR-230 spectrophotome-
4.2.1. 3-Tributylgermyl-1-propanol (3a)
Bp 150 ꢁC (0.45 Torr, bath temp.). IR (neat) 3323 (br s,
1
OH), 2956, 2923, 1463, 1053 cmꢀ1; H NMR (CDCl3) d
0.64–0.74 (m, 8H), 0.88 (t, J = 7.0 Hz, 9H), 1.25–1.37 (m,
12H), 1.54–1.66 (m, 3H), 3.59 (t, J = 6.8 Hz, 2H); 13C
NMR (CDCl3) d 8.15 (CH2), 12.40 (CH2 · 3), 13.76
(CH3 · 3), 26.61 (CH2 · 3), 27.45 (CH2 · 3), 28.48 (CH2),
65.94 (CH2); MS m/z (relative intensity) 247 (M+ – Bu,
100), 245 (M+ – 2 – Bu, 78), 243 (M+ – 4 – Bu, 56); Anal.
Calc. for C15H34GeO: C, 59.45; H, 11.31. Found: C, 59.76;
H, 11.02%.
1
ter. H NMR spectra at 270 MHz and 13C NMR spectra
at 67.7 MHz were recorded on a JEOL JNM-EX-270 spec-
trometer. The chemical shifts (d) are reported with refer-
ence at 0.00 ppm (Me4Si) or 7.26 ppm (CHCl3) for the
proton and at 77.00 ppm (centered on the signal of CDCl3)
for the carbon. Mass spectra were measured (by EI
method) on a Shimadzu GCMS-QP5050 instrument. Ele-
mental analyses were performed by the Analysis Center
of the University of Tsukuba.
4.2.2. 1-Tributylgermyl-3-undecanol (3b)
IR (neat) 3354 (br s, OH), 2956, 2924, 2854, 1464 cmꢀ1
;
4.1. Synthesis of dibutylchlorogermane
1H NMR (CDCl3) d 0.60–0.80 (m, 8H), 0.89 (t, J = 6.8 Hz,
12H), 1.28–1.54 (m, 29H), 3.44–3.54 (m, 1H); 13C NMR
(CDCl3) d 7.90 (CH2), 12.33 (CH2 · 3), 13.73 (CH3 · 3),
14.06 (CH3), 22.65 (CH2), 25.69 (CH2), 26.60 (CH2 · 3),
27.44 (CH2 · 3), 29.27 (CH2), 29.60 (CH2), 29.74 (CH2),
31.87 (CH2), 32.70 (CH2), 36.61 (CH2), 74.31 (CH); MS
m/z (relative intensity) 359 (M+ – Bu, 24), 357 (M+ – 2 –
Bu, 30), 355 (M+ – 4 – Bu, 21), 205 (100). Anal. Calc.
for C23H50GeO: C, 66.52; H, 12.14. Found: C, 66.29; H,
12.17%.
As shown in Scheme 3, the title compound was prepared
from tetrachlorogermane by four steps. See the references
for the steps from tetrachlorogermane to dibutylgermane
[9]. The last step, chlorination of dibutylgermane, was per-
formed by the method reported by Kunai and co-workers
[10] as follows: under a nitrogen atmosphere, dibutylger-
mane (12.5 g, 66.2 mmol) was added to a mixture of CuCl2
(19.5 g, 145 mmol), CuI (0.42 g, 2.2 mmol), and Et2O
(260 mL) at 0 ꢁC. After being stirred for an hour, the reac-
tion mixture was warmed to room temperature and stirred
for 3 h. The resultant mixture was filtered through celiteꢂ.
After evaporation of the filtrate, the residual oil was diluted
with dry pentane (50 mL) again, filtered through celiteꢂ,
4.2.3. 2-Methyl-3-tributylgermyl-1-propanol (3c)
IR (neat) 3327 (br s, OH), 2956, 2924, 1464, 1030 cmꢀ1
;
1H NMR (CDCl3) d 0.52 (dd, J = 13.8, 9.6 Hz, 1H), 0.70–
0.76 (m, 6H), 0.82 (dd, J = 13.8, 4.8 Hz, 1H), 0.89 (t,

518
K. Miura et al. / Journal of Organometallic Chemistry 692 (2007) 514–519
J = 7.0 Hz, 9H), 0.95 (d, J = 6.6 Hz, 3H), 1.28–1.35 (m,
12H), 1.53 (br s, 1H), 1.71–1.83 (m, 1H), 3.35 (dd,
J = 10.3, 6.9 Hz, 1H), 3.44 (dd, J = 10.3, 5.6 Hz, 1H);
13C NMR (CDCl3) d 13.20 (CH2 · 3), 13.75 (CH3 · 3),
16.86 (CH2), 19.46 (CH3), 26.65 (CH2 · 3), 27.44
(CH2 · 3), 33.17 (CH), 70.79 (CH2). Anal. Calc. for
C16H36GeO: C, 60.61; H, 11.44. Found: C, 60.31; H,
11.37%.
Bu, 44). Anal. Calc. for C16H34GeO2: C, 58.05; H, 10.35.
Found: C, 58.10; H, 10.39%.
4.2.8. 4-(Tributylgermyl)octane (3h)
Bp 200 ꢁC (1 Torr, bath temp.). IR (neat) 2956, 2924,
1
2856, 1464 cmꢀ1; H NMR (CDCl3) d 0.67–0.73 (m, 6H),
0.85–0.91 (m, 15H), 0.97–1.06 (m, 1H), 1.20–1.42 (m,
22H); 13C NMR (CDCl3) d 12.16 (CH2 · 3), 13.76
(CH3 · 3), 14.12 (CH3), 14.48 (CH3), 22.22 (CH2), 23.08
(CH2), 25.67 (CH), 26.85(CH2 · 3), 27.67 (CH2 · 3),
30.71 (CH2), 31.41 (CH2), 33.51 (CH2); MS m/z (relative
intensity) 301 (M+ – Bu, 5.4), 299 (M+ – Bu – 2, 4.0),
297 (M+ – Bu – 4, 2.9), 189 (100). Anal. Calc. for
C20H44Ge: C, 67.25; H, 12.42. Found: C, 67.16; H, 12.79%.
4.2.4. 1-(Tributylgermyl)undecane (3d)
Bp 180 ꢁC (1.3 Torr, bath temp.). IR (neat) 2956, 2924,
1
2854, 1464 cmꢀ1; H NMR (CDCl3) d 0.65–0.71 (m, 8H),
0.86–0.94 (m, 12H), 1.12–1.52 (m, 30H); 13C NMR
(CDCl3) d 11.86 (CH2), 12.49 (CH2 · 3), 13.79 (CH3 · 3),
14.12 (CH3), 22.71 (CH2), 25.23 (CH2), 26.67 (CH2 · 3),
27.54 (CH2 · 3), 29.32 (CH2), 29.38 (CH2), 29.67 (CH2),
29.68 (CH2), 29.74 (CH2), 31.95 (CH2), 33.71 (CH2); MS
m/z (relative intensity) 343 (M+ – Bu, 33), 341 (M+ – 2 –
Bu, 21), 339 (M+ – 4 – Bu, 17), 57 (100). Anal. Calc. for
C23H50Ge: C, 69.19; H, 12.62. Found: C, 69.29; H, 12.71%.
4.2.9. 1-Tributylgermyl-2-(trimethylsiloxy)cyclohexane (3i,
single isomer)
Bp 230 ꢁC (1 Torr, bath temp.). IR (neat) 2956, 2925,
1
2871, 1738, 1252 cmꢀ1; H NMR (CDCl3) d 0.10 (s, 9H),
0.65–0.75 (m, 6H), 0.89 (t, J = 6.9 Hz, 9H), 1.13–1.81 (m,
21H), 4.03–4.06 (m, 1H); 13C NMR (CDCl3) d 0.68
(CH3 · 3), 12.13 (CH2 · 3), 13.80 (CH3 · 3), 20.94 (CH2),
23.78 (CH2), 26.93 (CH2 · 3), 27.64 (CH2), 27.71
(CH2 · 3), 33.28 (CH), 35.05 (CH2), 70.31 (CH); MS m/z
4.2.5. 1-Butoxy-2-(tributylgermyl)ethane (3e)
Bp 130 ꢁC (2 Torr, bath temp.). IR (neat) 2956, 2925,
2854, 1107 cmꢀ1 1H NMR (CDCl3) d 0.68–0.74 (m, 6
;
H), 0.85–0.94 (m, 12H), 1.05–1.12 (m, 2H), 1.28–1.44 (m,
14H), 1.50–1.60 (m, 2H), 3.39 (t, J = 6.6 Hz, 2H), 3.45–
3.51 (m, 2 H); 13C NMR (CDCl3) d 12.67 (CH2 · 3),
13.74 (CH3 · 3), 13.94 (CH3), 14.21 (CH2), 19.46 (CH2),
26.56 (CH2 · 3), 27.41 (CH2 · 3), 32.03 (CH2), 68.65
(CH2), 70.07 (CH2); MS m/z (relative intensity) 289 (M+
– Bu, 13), 287 (M+ – 2 – Bu, 9.5), 285 (M+ – 4 – Bu,
6.9), 261 (100). Anal. Calc. for C18H40GeO: C, 62.64; H,
11.68. Found: C, 62.52; H, 11.76%.
(relative intensity) 277 (M+ – Bu – C6H10, 47), 275 (M+
–
2 – Bu – C6H10, 32), 273 (M+ – 4 – Bu – C6H10, 25), 73
(100). Anal. Calc. for C21H46GeOSi: C, 60.74; H, 11.16.
Found: C, 60.68; H, 11.10%.
4.2.10. 1-Methyl-2-(tributylgermylmethyl)cyclopentane
(6a, cis:trans = 3:1)
Bp 220 ꢁC (1 Torr, bath temp.). IR (neat) 2954, 2924,
1
2870, 1462 cmꢀ1; H NMR (CDCl3) d 0.62–0.95 (m, 20H)
including 0.80 (d, J = 9.2 Hz), 0.88 (t, J = 7.0 Hz), and
0.94 (d, J = 6.1 Hz), 1.01–1.36 (m, 16H), 1.45–1.95 (m,
4H); 13C NMR (CDCl3) for the major isomer d 13.09
(CH3 · 3), 13.51 (CH2), 13.80 (CH2 · 3), 14.85 (CH3),
22.63 (CH2), 26.77 (CH2 · 3), 27.57 (CH2 · 3), 32.33
(CH2), 33.07 (CH2), 38.39 (CH), 40.25 (CH), for the minor
isomer d 13.13 (CH3 · 3), 13.80 (CH2 · 3), 17.59 (CH2),
18.72 (CH3), 23.13 (CH2), 26.77 (CH2 · 3), 27.57
(CH2 · 3), 34.22 (CH2), 34.92 (CH2), 44.38 (CH), 45.09
(CH); MS m/z (relative intensity) for the major isomer
285 (M+ – Bu, 23), 283 (M+ – Bu – 2, 15), 281 (M+ – Bu
– 4, 14), 55 (100), for the minor isomer 285 (M+ – Bu,
17), 283 (M+ – Bu – 2, 10), 281 (M+ – Bu – 4, 12), 55
(100). Anal. Calc. for C19H40Ge: C, 66.89; H, 11.82.
Found: C, 66.59; H, 11.90%.
4.2.6. Cyclohexyl 3-(tributylgermyl)propanoate (3f)
Bp 230 ꢁC (1 Torr, bath temp.). IR (neat) 2927, 2858,
1
1732 (C@O), 1454, 1200 cmꢀ1; H NMR (CDCl3) d 0.69–
0.75 (m, 6H), 0.89 (t, J = 7.0 Hz, 9H), 0.96–1.02 (m, 2H),
1.23–1.50 (m, 18H), 1.69–1.90 (m, 4H), 2.26–2.32 (m,
2H), 4.71–4.78 (m, 1H); 13C NMR (CDCl3) d 7.71 (CH2),
12.25 (CH2 · 3), 13.72 (CH3 · 3), 23.79 (CH2 · 2), 25.41
(CH2), 26.57 (CH2 · 3), 27.35 (CH2 · 3), 30.47 (CH2),
31.66 (CH2 · 2), 72.43 (CH), 174.66 (C); MS m/z (relative
intensity) 261 (M+ – Bu –C6H10, 54), 259 (M+ – 2 – Bu –
C6H10, 44), 257 (M+ – 4 – Bu – C6H10, 32). Anal. Calc.
for C21H42GeO2: C, 63.19; H, 10.61. Found: C, 63.18; H,
10.76%.
4.2.7. Methyl 3-(tributylgermyl)propanoate (3g)
Bp 130 ꢁC (2 Torr, bath temp.). IR (neat) 2956, 2923,
4.2.11. 1,1-Bis(methoxymethyl)-3-methyl-4-
(tributylgermylmethyl)cyclopentane (6b, cis:trans = 4:1)
Bp 250 ꢁC (1 Torr, bath temp.). IR (neat) 2954, 2924,
1
2856, 1741 (C@O), 1464, 1205 cmꢀ1; H NMR (CDCl3) d
0.68–0.76 (m, 6H), 0.89 (t, J = 6.8 Hz, 9H), 0.97–1.04 (m,
2H), 1.32 (br s, 12H), 2.32–2.49 (m, 2H), 3.67 (s, 3H);
13C NMR (CDCl3) d 7.68 (CH2), 12.22 (CH2 · 3), 13.72
(CH3 · 3), 26.56 (CH2 · 3), 27.33 (CH2 · 3), 29.92 (CH2),
51.54 (CH3), 175.62 (C); MS m/z (relative intensity) 275
(M+ – Bu, 100), 273 (M+ – 2 – Bu, 78), 271 (M+ – 4 –
1
2871, 1458, 1113 cmꢀ1; H NMR (CDCl3) d 0.35–0.95 (m,
20H), 1.15–1.34 (m, 14H), 1.53–1.78 (m, 2.4H), 1.89–2.08
(m, 1.6H), 3.17 (s, 2.4H), 3.24 (br s, 1.6H), 3.33 (s, 6H);
13C NMR (CDCl3) for the major isomer d 13.00
(CH2 · 3), 13.41 (CH2), 13.76 (CH3 · 3), 15.81 (CH3),

K. Miura et al. / Journal of Organometallic Chemistry 692 (2007) 514–519
519
[2] (a) J. Pietruszka, in: I. Fleming (Ed.), Science of Synthesis, vol. 4,
Thieme, Stuttgart, Germany, 2001, p. 159 (Chapter 4.4.4);
(b) K. Oshima, in: M. Moloney (Ed.), Science of Synthesis, vol. 5,
Thieme, Stuttgart, Germany, 2002, p. 9 (Chapter 5.1.1);
(c) A.J. Clark, in: M. Moloney (Ed.), Science of Synthesis, vol. 5,
Thieme, Stuttgart, Germany, 2002, p. 205 (Chapter 5.2.1).
[3] (a) M.A. Brook, Silicon in Organic, Organometallic, and Polymer
Chemistry, Wiley Interscience, New York, 2000, p. 401;
(b) A.G. Davies, Organotin Chemistry, Wiley-VCH, Weinheim, 2004,
p. 54.
26.68 (CH2 · 3), 27.49 (CH2 · 3), 37.79 (CH), 39.09 (CH),
39.28 (CH2), 39.79 (CH2), 46.33 (C), 59.16 (CH3 · 2),
77.46 (CH2), 78.79 (CH2), for the minor isomer d 13.07
(CH2 · 3), 13.76 (CH3 · 3), 16.51 (CH2), 17.78 (CH3),
26.68 (CH2 · 3), 27.49 (CH2 · 3), 41.34 (CH2), 41.94
(CH2), 43.16 (CH), 43.97 (CH), 45.06 (C), 59.16
(CH3 · 2), 78.05 (CH2 · 2); MS m/z (relative intensity) for
the major isomer 373 (M+ – Bu, 59), 371 (M+ – Bu – 2,
48), 369 (M+ – Bu – 4, 37), 45 (100), for the minor isomer
373 (M+ – Bu, 36), 371 (M+ – Bu – 2, 25), 369 (M+ – Bu
– 4, 20), 45 (100). Anal. Calc. for C23H48GeO2: C, 64.36;
H, 11.27. Found: C, 64.54; H, 11.27%.
[4] (a) B. Kopping, C. Chatgilialoglu, M. Zehnder, B. Giese, J. Org.
Chem. 57 (1992) 3994;
(b) C. Chatgilialoglu, Acc. Chem. Res. 25 (1992) 188;
(c) . A related work:C. Chatgilialoglu, M. Guerra, A. Guerrini, G.
Seconi, J. Org. Chem. 57 (1992) 2427.
[5] (a) S. Tanaka, T. Nakamura, H. Yorimitsu, H. Shinokubo, K.
Oshima, Org. Lett. 2 (2000) 1991;
4.3. Competitive reaction of alkenes 2b and 2d
(b) T. Nakamura, S. Tanaka, H. Yorimitsu, H. Shinokubo, K.
Oshima, C.R. Acad. Sci. Paris, Chimie 4 (2001) 461.
[6] W.P. Neumann, J. Pedain, Tetrahedron Lett. (1964) 2461.
[7] (a) K. Miura, H. Saito, S. Uchinokura, A. Hosomi, Chem. Lett.
(1999) 659;
Under a nitrogen atmosphere, Et3B (1.0 M in hexane,
0.025 mL, 0.025 mmol) and dry air (2.5 mL) were added
to a solution of 1-undecen-3-ol (2b, 86 mg, 0.51 mmol), 1-
undecene (2d, 76 mg, 0.49 mmol) and Bu2GeClH (1a,
129 mg, 0.58 mmol) in hexane (1 mL) at 0 ꢁC. After being
stirred for 5 min, the resultant mixture was warmed to
room temperature and stirred for 5 h. After then, the mix-
ture was treated with BuLi (1.60 M in hexane, 0.75 mL,
1.2 mmol) and stirred for 10 min. The mixture was poured
into saturated aqueous NH4Cl (10 mL). The extract with t-
BuOMe (3 · 10 mL) was dried over Na2SO4 and evapo-
rated. Purification of the crude product by silica gel column
chromatography gave 1-tributylgermyl-3-undecanol (3b,
54 mg, 0.13 mmol, 26%) and 1-(tributylgermyl)undecane
(3d, 87 mg, 0.22 mmol, 44%).
(b) K. Miura, D. Wang, Y. Matsumoto, N. Fujisawa, A. Hosomi, J.
Org. Chem. 68 (2003) 8730;
(c) K. Miura, D. Wang, Y. Matsumoto, A. Hosomi, Org. Lett. 7
(2005) 503;
(d) K. Miura, D. Wang, A. Hosomi, Synlett (2005) 406;
(e) K. Miura, D. Wang, A. Hosomi, J. Am. Chem. Soc. 127 (2005)
9366.
[8] For radical reduction and addition of haloalkanes using 1a and 1b,
see: K. Miura, K. Ootsuka, A. Hosomi, Synlett (2005) 3151.
[9] (a) J. Satge, Ann. Chim. 6 (1961) 519;
(b) K. Mochida, I. Miyagawa, Bull. Chem. Soc. Jpn. 56 (1983)
1875.
[10] For the last step, see: J. Ohshita, Y. Toyoshima, A. Iwata, H. Tang,
A. Kunai, Chem. Lett. (2001) 886.
[11] It is known that Et3B-dry air effectively initiates homolytic hydrog-
ermylation and hydrostannylation under mild conditions. See Ref. [5]
and references therein. For this reason, we selected Et3B-dry air as
radical initiator.
[12] The butylation was performed only for the ease of isolation and
characterization of the hydrogermylation products in the
atmosphere.
Acknowledgements
This work was partly supported by Grants-in-Aid for Sci-
entific Research from the Ministry of Education, Culture,
Sports, Science, and Technology, Government of Japan.
[13] The successful addition to less reactive internal alkenes under solvent-
free conditions seems only due to rate-acceleration of the intermo-
lecular reaction by increased concentration of the reactants.
[14] Bond dissociation enthalpies of C–M bond in Me4M are ca. 340
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