The preparation of 1,3-dizincapropanes via a boron-zinc transmetallation

Article abstract of DOI:10.1016/S0022-328X(97)00746-8

The reaction of 1,3-diethylborylpropane and the corresponding 3-mercurio derivatives were prepared by hydroboration of the allylic precursor and were treated with diethylzinc leading to the corresponding 1,3-bimetallic reagents which, based on their sharp

Full text of DOI:10.1016/S0022-328X(97)00746-8

Journal of Organometallic Chemistry 562 (1998) 133–139
The preparation of 1,3-dizincapropanes via a boron–zinc
transmetallation
Appana S. Bhanu Prasad, Holger Eick, Paul Knochel *
Fachbereich Chemie der Philipps-Uni6ersita¨t Marburg, 35032 Marburg, Germany
Received 25 September 1997
Abstract
The reaction of 1,3-diethylborylpropane and the corresponding 3-mercurio derivatives were prepared by hydroboration of the
allylic precursor and were treated with diethylzinc leading to the corresponding 1,3-bimetallic reagents which, based on their sharp
NMR signals, were tentatively considered as eight-membered rings. Their reaction with reactive electrophiles like allylic bromides
or propargyl bromide, benzoyl chloride and ethyl propiolate in the presence of CuCN·2LiCl provided the desired 1,3-adducts in
fair to good yields. These sensitive 1,3-dimetallics proved not to be suited for reactions with less reactive organic electrophiles, and
hydride-transfer reactions were observed. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Zinc; Boron; Transmetallation
1. Introduction
2. Results and discussion
1,3-Dimetallic compounds of main group elements
are useful building blocks for the preparation of metal-
lacyclic transition metal complexes [1]. Applications of
these dimetallic species for organic synthesis has been
less frequent due to the difficult preparation of these
organometallics. Thus, the reaction of 1,3-dibromo-
propane with various metals including lithium, magne-
sium or zinc affords cyclopropane as the major reaction
product and 1,3-dimetallic compounds can only be
obtained in modest yields [2]. Recently, we reported the
preparation of 1,3-dizincapropanes 1a-b [3] using a
boron–zinc exchange reaction [4]. Herein, we wish to
report some of the aspects of the reactivity of 1a-b
toward organic electrophiles as well as the preparation
and reactivity of the corresponding mixed 1,3-bimetallic
of zinc and mercury (2).
The reaction of allylic zinc bromides 3a-b [5] with
diethylthiophenylborane (4) [6] furnishes the allylic di-
ethylboranes 5a-b. The sensitive organoboranes can be
isolated in pure form by distillation under reduced
pressure (53–67%). The hydroboration of 5a-b with
diethylborane [4] gives the expected 1,3-diethylboryl-
propane derivatives 6a-b in 82–85% yield as a clear oil.
Similarly, the hydroboration of diallylmercury (7) [7]
with diethylborane [4,8] at −30°C affords the mixed
1,3-bimetallic of mercury and boron (8) (Scheme 1).
The 1,3-bimetallic 8 was directly used for the prepa-
ration of 2 since all attempts to purify this compound
led to decomposition. The 1,3-diboron derivatives (6a-
b) and 8 undergo a smooth boron–zinc exchange reac-
tion by treatment with Et2Zn (four equivalents, neat,
0°C, 0.5 h) leading, after removal of the excess Et2Zn
by vacuum, to the crude 1,3-dizincapropanes 1a-b,
1
which are obtained as sole products as shown by H-
and 13C-NMR analysis (see Scheme 2 and Section 4).
Based on NMR experiments as well as on the exten-
sive studies of Bickelhaupt on the structural behavior of
* Corresponding author.
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(97)00746-8

134
A.S. Bhanu Prasad et al. / Journal of Organometallic Chemistry 562 (1998) 133–139
Scheme 1.
1,5-, 1,6- and 1,7-dizincaalkanes [9], we favor an eight-
membered cyclic structure for 1a-b, as well as for 2,
rather than an open-chain polymeric structure (–
ZnCH2CH2CH2–)n or ((CH2)3Hg–(CH2)3–Zn)n, since
the 13C-NMR spectra of 1b shows a sharp set of signals
with two signals for carbon C(1), C(2) and C(3), which
can be explained assuming the existence of cis and trans
isomers, respectively cis-1b and trans-1b, in an approx-
imate ratio of 46:54 (Scheme 3).
These 1,3-bimetallics of zinc display a low reactivity
toward organic electrophiles like most organozinc com-
pounds. However, after transmetallation to the corre-
sponding copper–zinc compounds by adding the
trophiles (tosyl cyanide [10], benzaldehyde) was ob-
served showing that 1a-b play the role of a hydride
donor.
The 1,3-bimetallic of zinc and mercury has a similar
chemical behavior and reacts in the presence of
CuCN·2LiCl [11] with allylic halides, benzoyl chloride,
nitrostyrene, ethyl propiolate and 3-iodo-2-cyclohexen-
1-one [12] affording the expected polyfunctional
diorganomercurials (13a–e) in 40–58% yield (Scheme
5).
As a synthetic application, we have examined the
performance of cyclization reactions using bisfunctional
electrophiles. Thus, the reaction of 1b with 1,4-di-
bromo-2-butyne (14) [13,14] in the presence of
CuCN·2LiCl affords the sensitive 1,2-bis(exo-
methylene)cyclopentane (15) in 48% yield (Scheme 6).
terahydrofuran
(THF)
soluble
copper
salt
CuCN·2LiCl, the reaction with reactive electrophiles
like allylic halides furnishes the expected allylated prod-
ucts 9a–d in 84–88% yield. With propargyl bromide,
the formation of the 1,3-bisallenylated product (10) is
obtained in 48% yield. Unsaturated electrophiles like
ethyl propiolate provide the bisMichael adduct (11) in
40% yield. Finally, the reaction of 1a-b with benzoyl
chloride in the presence of CuCN·2LiCl furnishes the
1,5-diketone (12a-b) in 38–40% yield (Scheme 4). Reac-
tions with other classes of electrophiles like aldehydes,
less reactive acid chlorides or enones did not lead to the
desired 1,3-adducts. Reduction of several of these elec-
3. Conclusion
We have prepared several 1,3-bimetallic compounds
of zinc and mercury and have reacted them with or-
ganic electrophiles in the presence of a copper catalyst
leading to 1,3-disubstituted products in good to moder-
ate yield. A new access method to polyfunctional
diorganomercurials was developed and a new cycliza-
tion to a bis(exo-methylene)cyclopentane was per-
formed. The limited stability of the bis-metallic reagents
1a-b and 2 did not allow further extension of the scope
of these quenching reactions.
Scheme 2.
Scheme 3.

A.S. Bhanu Prasad et al. / Journal of Organometallic Chemistry 562 (1998) 133–139
135
Scheme 4.
4. Experimental
allylic borane 5a, which was characterized by NMR
spectroscopy (11.8 g, 107 mmol, 67% yield). H-NMR
1
All reactions were carried out under argon atmo-
sphere using standard Schlenk techniques. THF was
distilled from sodium benzoquinone immediately before
use. Diethylthiophenylborane (4) [6], diallylmercury (7)
[7], allylzinc bromide [5], 3-iodo-2-cyclohexen-1-one
[12], 1,4-dibromo-2-butyne [14], ethyl (2-bro-
momethyl)acrylate [15] were prepared according to the
literature procedures.
(CDCl3, 200 MHz): l 5.77–5.98 (m, 1H), 4.70–4.95 (m,
2H), 2.00–2.20 (s, br, 2H), 1.00–1.25 (m, 4H), 0.70–
1.00 (m, 6H). 13C-NMR (CDCl3, 50 MHz): l 135.8,
113.5, 34.0 (br), 19.5 (br), 7.8.
4.1.2. Preparation of (2-butylallyl)borane (5b)
The same procedure as described for 5a was applied
using zinc foil (6.86 g, 92 mmol), 2-bromomethylhexene
(11.33 g, 64 mmol) and diethylthiophenylborane (4)
(11.40 g, 64 mmol). The crude product was purified
rapidly with fast distillation by heating the reaction
flask to 100°C. This product was redistilled carefully
furnishing the desired product (5b) (8.51 g, 49 mmol,
4.1. General experimental procedure
4.1.1. Preparation of allyl(diethyl)borane (5a)
A 250 ml three-necked flask equipped with a mag-
netic stirrer, an argon inlet, an addition funnel and a
thermometer was charged with cut zinc foil (10.5 g, 160
mmol), THF (8 ml) and 1,2-dibromoethane (900 mg,
4.8 mmol). The flask was briefly heated to activate the
zinc foil. The reaction mixture was treated with chloro-
trimethylsilane (290 mg, 2.7 mmol) and cooled after 5
min to 0°C. Allyl bromide (19.4 g, 160 mmol) in THF
(70 ml) was added slowly in order to keep the tempera-
ture below 8°C. After the end of the addition, the
reaction mixture was stirred for 1 h and the resulting
allylzinc bromide was ready to use [5]. Gas chromatog-
raphy analysis of hydrolyzed and iodolyzed reaction
aliquots (containing an internal standard like decane)
allow a yield estimate of ca. 80%. This zinc reagent was
treated with diethylthiophenylborane (4) [6] (28.5 g, 160
mmol) at 0°C. The reaction mixture was allowed to
warm to 25°C and the solvent was distilled off by
treating with an oil bath to 150°C, the fractions at
110–115°C were collected and contained the sensitive
1
53% yield). H-NMR (CDCl3, 300 MHz): l 4.58–4.77
(m, 1H), 4.37–4.58 (m, 1H), 2.04–2.25 (m, 2H), 1.88 (t,
2H, J=7.3 Hz), 1.27–1.42 (m, 4H), 1.16 (q, 4H, J=
7.7 Hz), 0.90 (t, 3H, J=7.6 Hz), 0.85–0.92 (m, 6H).
13C-NMR (CDCl3, 75.5 MHz): l 149.1, 109.5, 38.6,
37.0 (br), 30.1, 22.6, 20.0 (br), 14.0, 8.2.
4.1.3. Preparation of 1,3-bis(diethylboryl)propane (6a)
Diethylborane was prepared by mixing commercially
available BH3 ·Me2S and Et3B in the ratio 1:2. The
resulting solution can be stored in the refrigerator for
several weeks [8]. Diethylborane (12 mmol) was cooled
to 0°C and diethylallylborane (5a) (1.32 g, 12 mmol)
was added. The reaction mixture was stirred for 2 h at
25°C and the unreacted boranes and methyl sulfide was
evaporated at 0°C under vacuum (0.1 mmHg). The
air-sensitive 1,3-diborane (6a) was characterized only
by NMR spectroscopy. 1H-NMR (CDCl3, 200 MHz): l
1.46–1.58 (m, 2H), 1.12–1.24 (m, 12H), 0.85–0.95 (t,

136
A.S. Bhanu Prasad et al. / Journal of Organometallic Chemistry 562 (1998) 133–139
Scheme 5.
12H). 13C-NMR (CDCl3, 50 MHz): l 31.5 (br), 19.2
(br), 18.9, 8.2.
(CDCl3, 300 MHz): l 1.94 (q, 2H, J=8 Hz), 1.27 (t,
2H, J=8 Hz), 1.17 (q, 4H, J=8 Hz), 1.05 (t, 2H, J=8
Hz), 0.91 (t, 6H, J=8 Hz). 13C-NMR (CDCl3, 75.5
MHz): l 48.2, 34.0 (br), 23.6, 18.9 (br), 8.2.
4.1.4. Preparation of
1,3-bis(diethylboryl)-2-butylpropane (6b)
4.1.6. Preparation of 1,5-dizincacyclooctane (1a)
The product 6b was prepared using the same proce-
dure as for 6a with the allylic borane 5b (2.14 g, 12.9
mmol) and diethylborane (12.9 mmol) resulting in the
formation of 6b as a clear liquid after evaporation of
the solvents. This sensitive material was characterized
only by NMR spectroscopy. 1H-NMR (CDCl3, 300
MHz): l 1.00–1.40 (m, 19H), 0.78–1.00 (m, 15H).
13C-NMR (CDCl3, 75.5 MHz): l 40.8, 37.6 (br), 32.5,
30.2, 23.0, 19.9 (br), 14.2, 8.3.
The 1,3-diboron derivative 6a (5 mmol) was treated
neat with Et2Zn (2.0 ml, 20 mmol) and the reaction
mixture was stirred for 0.5 h at 0°C and the excess
Et2Zn was removed by vacuum (3 h, 0.1 mmHg fol-
lowed by 1 h at 25°C and 0.1 mmHg). The resulting
crude 1a is a gray oil containing small amounts of zinc
powder. The dizinc reagent can be stored at 0°C for 24
h with little decomposition. This sensitive material was
characterized by NMR spectroscopy and used crudely
1
for the next step (reaction with electrophiles). H-NMR
4.1.5. Preparation of bis(3-diethylborylpropyl)mercury
(8)
(THF-d8, 300 MHz): l 1.82 (m, 4H), 0.22 (m, 8H).
13C-NMR (THF-d8, 75.5 MHz): l 27.7, 22.4.
Diallylmercury (7) [7] (420 mg, 1.5 mmol) was dis-
solved in dry ether and cooled at −30°C in a Schlenk
tube protected from light (wrapped in aluminium foil).
Diethylborane (5 mmol) was added dropwise and the
reaction mixture was allowed to warm to r.t. and was
stirred for 1.5 h. Excess diethylborane was pumped off
at 0°C (0.1 mmHg) resulting in the formation of the
sensitive 1,3-dimetallic 8, which was used directly for
the next step (preparation of 2). It was only character-
ized by 1H- and 13C-NMR spectroscopy. 1H-NMR
4.1.7. Preparation of 1,5-dizinca-3,7-dibutylcyclooctane
(1b)
This product was prepared as described for 1a using
the 1,3-diborane derivative 6b (464 mg, 1.97 mmol) and
Et2Zn (0.79 ml, 7.88 mmol). The crude product 1b was
used directly for further transformations (reactions with
electrophiles). It was characterized only by NMR spec-
1
troscopy. H-NMR (THF-d8, 500 MHz): l 2.10–2.20
(m, 2H), 1.10–1.35 (m, 12H), 0.80–0.95 (m, 6H), 0.30–
0.55 (m, 8H). 13C-NMR (THF-d8, 125 MHz): l 49.2,
48.5, 39.0, 38.6, 32.1, 31.6, 31.6, 31.3, 24.5, 15.0.
4.1.8. Preparation of 1-zinca-5-mercuriocyclooctane (2)
The crude mercury compound 8 prepared in the
quantities as described above was treated with Et2Zn
Scheme 6.

A.S. Bhanu Prasad et al. / Journal of Organometallic Chemistry 562 (1998) 133–139
137
(0.6 ml, 6 mmol) at 0°C and was stirred for 0.5 h. The
excess of Et2Zn was removed by vacuum (0°C, 0.1
mmHg, 2 h and 25°C, 2 h) providing the crude zinc
reagent 2 which was used directly for further transfor-
mations. This sensitive material was characterized by
obtained using ethyl (2-bromomethyl)acrylate [15] (3.26
g, 16.9 mmol). The crude product was purified by flash
chromatography (hexanes:ether, 19:1). IR (neat): 2982
(s), 2934 (vs), 1719 (vs), 1632 (s), 940 (s), 883 (s) cm−1
.
1H-NMR (CDCl3, 300 MHz): l 6.08 (s, 2H), 5.48 (s,
2H), 4.13 (q, 4H, J=7.1 Hz), 2.20–2.30 (m, 4H),
1.37–1.47 (m, 5H), 1.21–1.31 (m, 12 H), 0.83–0.90 (m,
3H). 13C-NMR (CDCl3, 75.5 MHz): l 167.0, 141.2,
123.8, 60.2, 36.6, 32.7, 32.0, 28.8, 28.5, 22.7, 13.9, 13.8.
EI-MS: 324 (M+, 3), 278 (13), 250 (72), 221 (26), 193
(34), 177 (57), 80 (100). CH-Anal. Calc. for C19H32O4
(324.46): C, 70.34; H, 9.94. Found: C, 70.12; H, 9.68%.
1
NMR spectroscopy. H-NMR (THF-d8, 300 MHz): l
2.59 (m, 2H), 1.05 (t, 2H, J=10.0 Hz), 0.20 (t, 2H,
J=10.0 Hz). 13C-NMR (THF-d8, 75.5 MHz): l 49.2,
29.2, 18.8.
4.1.9. Typical procedure for the reaction of a
1,3-dimetallic reagent (1a or 1b) with an electrophile.
Preparation of 2,8-dibromo-1,8-nonadiene (9c)
The 1,3-bimetallic reagent 1a prepared from the 1,3-
diboron derivative 6a (0.88 g, 4.9 mmol) was treated
with Et2Zn (2.0 ml, 20 mmol) as described above. The
resulting 1,3-dizinc reagent 1a was diluted in THF (8
ml) cooled to −60°C and a solution of CuCN (890 mg,
10 mmol) and LiCl (850 mg, 20 mmol) in THF (12 ml)
was added, followed after 5 min with 2,3-dibromo-
propene (2.93 g, 16.7 mmol). The reaction mixture was
allowed slowly to warm to 25°C and stirred for 0.5 h.
After the usual work-up, the resulting crude oil ob-
tained after evaporation of the solvents was purified by
flash chromatography using hexanes:ether (19:1) afford-
ing the desired product (9c) (1.16 g, 4.1 mmol, 84%
yield) as a yellowish oil. IR (neat): 2938 (s), 1630 (s),
4.1.10.3. Preparation of 5-butyl-2,8-dibromo-1,8-nona-
diene (9d). Compound 9d (1.41 g, 4.2 mmol, 87% yield)
was obtained using 2,3-dibromopropene (3.83 g, 19.2
mmol). The crude product was purified by flash chro-
matography (hexanes:ether, 19:1). IR (neat): 2928 (vs),
1
1629 (vs), 1456 (w), 885 (vs) cm−1. H-NMR (CDCl3,
300 MHz): l 5.56 (s, 2H), 5.37 (s, 2H), 2.41 (t, 4H,
J=7.6 Hz), 1.47–1.57 (m, 4H), 1.34–1.45 (m, 1H),
1.21–1.34 (m, 6H), 0.89 (t, 3H, J=6.7 Hz). 13C-NMR
(CDCl3, 75.5 MHz): l 135.0, 116.3, 38.7, 35.1, 32.8,
31.4, 28.6, 23.0, 14.1. EI-MS: 259, 257 (M+ –Br, 1), 177
(14), 137 (17), 95 (99), 81 (100), 67 (61). CH-Anal. Calc.
for C13H22Br2 (338.12): C, 46.18; H, 6.56. Found: C,
46.24; H, 6.63%.
1
885 (s), 734 (w) cm−1. H-NMR (CDCl3, 300 MHz): l
5.55 (m, 2H), 5.38 (m, 2H), 2.44 (t, 4H, J=7.3 Hz),
1.58 (q, 4H, J=7.5 Hz), 1.22–1.38 (m, 2H). 13C-NMR
(CDCl3, 75.5 MHz): l 134.5, 116.4, 41.2, 27.5, 27.0.
EI-MS: 203 (M+ –Br, 3), 201, 121 (29), 82 (11), 81
(100), 79 (19), 67 (18). CH-Anal. Calc. for C9H14Br2
(282.02): C, 38.33; H, 5.00. Found: C, 38.28; H, 5.04%.
4.1.10.4. Preparation of 5-butyl-1,2,7,8-nonatetraene
(10). Compound 10 (0.34 g, 1.93 mmol, 40% yield) was
obtained using propargyl bromide (4.09 g, 19.5 mmol).
The crude product was purified by flash chromatogra-
phy (hexanes) affording a sensitive compound that did
not give a correct elementary analysis and did not show
the molecular peak in mass spectrometric analysis.
However, clean 1H- and 13C-NMR spectra could be
obtained. IR (neat): 2926 (vs), 1956 (s), 1440 (m), 841
4.1.10. Analytical data of products 9a-b, 9d, 10, 11,
12a-b prepared according to the typical procedure
(Scheme 4)
1
(s) cm−1. H-NMR (CDCl3, 300MHz): l 5.02 (q, 2H,
J=7.1 Hz), 4.58–4.65 (m, 4H), 1.97–2.07 (m, 4H),
1.49 (sept, 1H, J=6.1 Hz), 1.21–1.39 (m, 6H), 0.83–
0.95 (m, 3H). 13C-NMR (CDCl3, 75.5 MHz): l 209.2,
87.8, 73.9, 37.9, 32.6, 32.2, 28.8, 22.9, 13.9. EI-MS: 147
(M+ –C2H5, 5), 133 (15), 122 (47), 105 (54), 91 (68), 79
(74), 41 (100).
4.1.10.1. 2,8-Dicarbethoxy-1,8-nonadiene (9a). Com-
pound 9a (1.23 mg, 4.57 mmol, 88% yield) was ob-
tained using ethyl (2-bromomethyl)acrylate [15] (3.49 g,
18.1 mmol). The crude product was purified by flash
chromatography (hexanes:ether, 19:1). IR (neat): 3104
(w), 2982 (s), 2934 (vs), 1719 (vs), 1632 (s), 1179 (vs, br)
1
cm−1. H-NMR (CDCl3, 200 MHz): l 6.04 (s, 2H),
4.1.10.5. Preparation of (E),(E)-1,7-dicarbethoxy-4-
butyl-1,6-heptadiene (11). Compound 11 (540 mg, 2.25
mmol, 40% yield) was obtained using ethyl propiolate
(1.65 g, 16.8 mmol) and the 1,3-diboron derivative 6b
(1.01 g, 5.6 mmol), and performing the reaction at
−15°C for 3 h. The crude product was purified by flash
chromatography (hexanes:ether, 8:1). IR (neat): 2982
(s), 1722 (vs), 1655 (s), 1368 (s), 1268 (s, br), 1044 (s),
980 (m) cm−1. 1H-NMR (CDCl3, 300 MHz): l 6.81 (dt,
2H, J=15.6 and 9.0 Hz), 5.71 (dt, 2H, J=15.7 and 1.5
Hz), 4.06 (q, 4H, J=7.1 Hz), 2.12 (q, 4H, J=7.4 Hz),
5.42 (s, 2H), 4.11 (q, 4H, J=7.1 Hz), 2.21 (t, 4H,
J=7.2 Hz), 1.29–1.45 (m, 6H), 1.21 (t, 6H, J=7.1
Hz). 13C-NMR (CDCl3, 50 MHz): l 167.1, 140.8, 124.0,
60.3, 31.6, 28.6, 28.0, 14.0. EI-MS: 268 (M+, 4), 223
(30), 194 (83), 149 (42), 148 (40), 121 (100), 81 (97).
CH-Anal. Calc. for C15H24O4 (268.35): C, 67.14; H,
9.01. Found: C, 66.85; H, 9.17%.
4.1.10.2. 5-Butyl-2,8-dicarbethoxy-1,8-nonadiene (9b).
Compound 9b (1.32 g, 4.07 mmol, 84% yield) was

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A.S. Bhanu Prasad et al. / Journal of Organometallic Chemistry 562 (1998) 133–139
1.53 (q, 2H, J=7.4 Hz), 1.16 (t, 6H, J=7.1 Hz).
13C-NMR (CDCl3, 75.5 MHz): l 165.9, 147.5, 121.6,
59.7, 30.9, 25.9, 13.8. EI-MS: 240 (M+, 8), 195 (51),
166 (44), 121 (27), 98 (31), 93 (63), 81 (100). CH-Anal.
Calc. for C13H20O4 (240.30): C, 69.98; H, 8.39. Found:
C, 69.76; H, 8.39%.
anes:ether, 19:1) yielding the compound 13a as an oil
(300 mg, 56% yield). IR (neat): 2924 (s), 1717 (s), 1630
1
(m), 1160 (s), 861 (m) cm−1. H-NMR (CDCl3, 200
MHz): l 6.05 (s, 2H), 5.44 (s, 2H), 4.13 (q, 4H, J=7.2
Hz), 2.24 (t, 4H, J=6 Hz), 1.72–1.86 (m, 4H), 1.36–
1.48 (m, 4H), 1.23 (t, 4H, J=7 Hz), 0.99 (t, 6H, J=7.2
Hz). 13C-NMR (CDCl3, 50 MHz): l 167.8, 141.6, 124.5,
60.9, 44.3, 34.5, 32.1, 28.8, 14.6. EI-MS: 512 (M+, 0.1),
510 (M+, 0.1), 357 (2), 200 (0.6), 156 (49), 155 (66), 127
(51), 109 (88), 81 (100). CH-Anal. Calc.: C, 42.30; H,
5.93. Found: C, 42.26; H, 6.16%.
4.1.10.6. Preparation of 1,5-diphenyl-1,5-pentadione
(12a). Compound 12a (560 mg, 2.22 mmol, 42% yield)
was obtained using benzoyl chloride (1.80 g, 12.8
mmol) and the 1,3-diboron derivative 6a (0.96 g, 5.33
mmol). The crude product was purified by flash chro-
matography (hexanes:ether, 9:1). The product was ob-
tained as a white solid (m.p. 61°C). IR (KBr): 3064 (w),
4.1.11.2.
Preparation
of
bis(4-phenyl-4-
oxobutyl)mercury (13b). Compound 13b (510 mg, 58%
yield) was obtained by the reaction of the 1,3-bimetallic
2 (2.5 mmol) with benzoyl chloride (490 mg, 3.5 mmol)
at −10°C for 6 h. The crude product was purified by
flash chromatography (hexanes:ether, 9:1) yielding the
compound 13b as a solid (m.p. 77°C). IR (neat): 2929
2970 (w), 1679 (vs), 1281 (s), 730 (s), 688 (s) cm−1
.
1H-NMR (CDCl3, 300 MHz): l 7.88–8.02 (m, 4H),
7.32–7.54 (m, 6H), 3.08 (t, 4H, J=7.0 Hz), 2.12–2.21
(q, 2H, J=7.0 Hz). 13C-NMR (CDCl3, 75.5 MHz): l
199.6, 136.7, 132.9, 128.4, 127.9, 37.4, 18.7. EI-MS: 252
(M+, 12), 133 (18), 120 (29), 105 (100), 77 (49), 51 (10).
CH-Anal. Calc. for C17H16O2 (252.12): C, 80.93; H,
6.39. Found: C, 80.74; H, 6.50%.
(s), 1681 (s), 1206 (m), 742 (m) cm−1 1H-NMR
.
(CDCl3, 300 MHz): l 7.86– 7.90 (m, 8H), 7.36–7.46
(m, 12H), 2.91 (t, 4H, J=7 Hz), 2.09–2.24 (m, 4H),
0.98 (t, 4H, J=7.2 Hz). 13C-NMR (CDCl3, 75.5 MHz):
l 201.1, 137.2, 132.8, 128.5, 128.1, 43.5, 42.7, 24.2.
EI-MS: 496 (M+, 0.3), 494 (M+, 0.2), 202 (1), 147
(94), 105 (100), 77 (53), 28 (4). CH-Anal. Calc.: C,
48.52; H, 4.49. Found: C, 48.23; H, 4.35%.
4.1.10.7. Preparation of 1,5-diphenyl-3-butyl-1,5-penta-
dione (12b). Compound 12b (600 mg, 1.93 mmol, 38%
yield) was obtained using benzoyl chloride (2.14 g, 15.2
mmol) and starting from the 1,3-diboron derivative 6b
(1.20 g, 5.1 mmol). The crude product was purified by
flash chromatography (hexanes:ether, 6:1). IR (neat):
3063 (w), 2929 (s), 1769 (m), 1684 (vs), 1597 (m), 1449
4.1.11.3.
Preparation
of
bis(5-nitro-4-
phenylpentyl)mercury (13c). Compound 13c (315 mg,
51% yield) obtained by the reaction of i-nitrostyrene
(313 mg, 2.1 mmol) with the 1,3-bimetallic 2 (1.5
mmol). Reaction conditions were 0°C, 12 h. The crude
product was purified by flash chromatography (hex-
anes:ether, 5:1). IR (neat): 2921 (s), 1551 (s), 1494 (s),
(s), 753 (s), 690 (vs) cm−1 1H-NMR (CDCl3, 300
.
MHz): l 7.86–7.94 (m, 4H), 7.32–7.50 (m, 6H), 2.86–
3.10 (m, 4H), 2.67 (sept, J=6.5 Hz, 1H), 1.32–1.43 (m,
2H), 1.12–1.31 (m, 4H), 0.78 (t, 3H, J=7.1 Hz).
13C-NMR (CDCl3, 75.5 MHz): l 199.9, 137.1, 132.9,
128.5, 128.1, 43.0, 33.8, 31.2, 29.0, 22.7, 13.9. EI-MS:
308 (M+, 1), 189 (34), 105 (100), 77 (44). CH-Anal.
Calc. for C21H24O2 (308.42): C, 81.78; H, 7.84. Found:
C, 81.88; H, 7.93%.
1
1453 (s), 764 (s), 702 (s) cm−1. H-NMR (CDCl3, 200
MHz): l 7.07–7.24 (m, 10H), 4.43 (m, 8H), 3.35–3.42
(m, 2H), 1.52–1.59 (m, 8H), 0.87–0.90 (m, 4H). 13C-
NMR (CDCl3, 50 MHz): l 138.7, 127.9, 126.5, 126.4,
80.0, 43.1, 42.3, 37.5, 25.0. EI-MS: 586 (M+, 0.2), 584
(M+, 0.1), 192 (10), 145 (95), 131 (100), 77 (11).
CH-Anal. Calc.: C, 45.17; H, 4.82; N, 4.78. Found: C,
44.91; H, 4.90; N, 4.96%.
4.1.11. Typical procedure for the reaction of the
1,3-bimetallic of mercury and zinc (2) with electrophiles
in the presence of CuCn ·2LiCl
4.1.11.1. Preparation of bis(5-carbethoxy-5-hex-
enyl)mercury (13a). The 1,3-bimetallic 2, prepared as
described above, was dissolved in THF (5 ml). A solu-
tion of CuCN (270 mg, 3 mmol) and LiCl (250 mg, 6
mmol) in THF (3 ml) was added at −78°C. The
reaction mixture was warmed up to 0°C and cooled
4.1.11.4. Preparation of (E)-bis(5-carbethoxy-4-pen-
tenyl)mercury (13d). Compound 13d (450 mg, 53%
yield) was obtained by the reaction of ethyl propiolate
(340 mg, 3.5 mmol) with the bimetallic 2 (2.5 mmol).
Reaction conditions were −78°C, 14 h. The crude
product was purified by flash chromatography (hex-
anes:ether, 85:15). IR (neat): 2926 (s), 1719 (s), 1654 (s),
back to −78°C after
5
min. Ethyl (2-bro-
1
momethyl)acrylate [15] (410 mg, 2.1 mmol) in THF (2
ml) was added and the reaction mixture was warmed up
to 0°C and kept for 2 h. It was worked-up as usual. The
crude product obtained after evaporation of the sol-
vents was purified by flash chromatography (hex-
1267 (s), 1043 (m), 987 (m) cm−1. H-NMR (CDCl3,
200 MHz): l 6.81–6.96 (m, 2H), 5.73 (d, 2H, J=15.6
Hz), 4.10 (q, 4H, J=7.2 Hz), 1.89–2.20 (m, 8H), 1.21
(t, 6H, J=7 Hz), 0.96 (t, 4H, J=7.4 Hz). 13C-NMR
(CDCl3, 50 MHz): l 165.5, 148.9, 120.8, 59.1, 41.9,

A.S. Bhanu Prasad et al. / Journal of Organometallic Chemistry 562 (1998) 133–139
139
36.2, 26.6, 13.3. EI-MS: 484 (M+, 14), 482 (M+, 1),
Acknowledgements
202 (8), 200 (1), 141 (49), 113 (84), 68 (47), 28 (100).
CH-Anal. Calc.: C, 39.79; H, 5.43. Found: C, 39.61;
H, 5.38%.
We thank the Chemische Industrie and the DFG
(SFB 260 and Leibniz program) for generous support.
ASBP thanks the Alexander von Humboldt Founda-
tion for a fellowship. We thank Witco (Bergkamen)
for the generous gift of chemicals.
4.1.11.5.
Preparation
of
bis(3-(3-oxocyclohex-
enyl)propyl)mercury (13e). Compound 13e (200 mg,
40% yield) was obtained by the reaction of 3-iodo-2-
cyclohexenone [12] (460 mg, 2.1 mmol) and the
bimetallic 2 (1.5 mmol). Reaction conditions were −
10°C, 48 h. Purification by flash chromatography
(hexanes:ether, 1:4). IR (neat): 2926 (s), 1665 (s), 1621
References
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(s), 1252 (s), 1192 (s), 886 (s) cm−1 1H-NMR
(CDCl3, 200 MHz): l 5.80 (s, 2H), 2.14–2.30 (m, 12
H), 1.91–2.02 (m, 8H), 0.95 (t, 4H, J=7.4 Hz). 13C-
NMR (CDCl3, 50 MHz): l 199.9, 167.3, 126.3, 43.6,
43.2, 37.7, 29.9, 26.7, 23.0. EI-MS: 476 (M+, 1), 474
(M+, 1), 137 (24), 123 (11), 110 (100), 95 (11). CH-
Anal. Calc.: C, 45.52; H, 5.52; Found: C, 45.30; H,
5.65%.
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1-butyl-3,4-dimethylenecyclopentane (15)
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Compound 15 (390 mg, 2.6 mmol, 48% yield) was
obtained using the typical procedure with the 1,3-di-
boron derivative 6b (1.30 g, 5.5 mmol) and 1,4-di-
bromo-2-butyne (1.46 g, 6.9 mmol) [14]. The crude
product was purified by flash chromatography (hex-
anes) yielding a sensitive compound which was pure
1
by 95% as judged by 13C-NMR and H-NMR spec-
troscopy. IR (neat): 3440 (s, br), 2956 (vs), 2923 (vs),
1
1672 (s), 1466 (m), 894 (s) cm−1. H-NMR (CDCl3,
300 MHz): l 5.33 (s, 2H), 4.85 (s, 2H), 2.49–2.63 (m,
2H), 2.01–2.13 (m, 2H), 1.81–1.97 (m, 1H), 1.21–
1.37 (m, 6H), 0.89–0.95 (m, 3H). 13C-NMR (CDCl3,
75.5 MHz): l 148.5, 103.5, 40.7, 37.5, 34.9, 30.4, 22.9,
14.1. EI-MS: 150 (M+, 12), 107 (18), 93 (100), 91
(36), 79 (28).
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.