Synthesis of tetramers of 1,3-adamantane derivatives

Article abstract of DOI:10.1016/S0040-4039(01)01825-1

Novel tetramers of 1,3-adamantane and 5,7-dibutyl-1,3-adamantane were synthesized by the coupling reaction of 3-bromo-1,1′-biadamantane or 3-bromo-5,5′,7,7′-tetrabutyl-1,1′-biadamantane with sodium in n-octane or with magnesium in diethyl ether. Although

Full text of DOI:10.1016/S0040-4039(01)01825-1

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 42 (2001) 8645–8647
Synthesis of tetramers of 1,3-adamantane derivatives
Takashi Ishizone,* Hiroyuki Tajima, Shinichi Matsuoka and Seiichi Nakahama
Department of Organic and Polymeric Materials, Graduate School of Science and Engineering, Tokyo Institute of Technology,
2-12-1 Ohokayama, Meguro-ku, Tokyo 152-8552, Japan
Received 31 August 2001; revised 27 September 2001; accepted 28 September 2001
Abstract—Novel tetramers of 1,3-adamantane and 5,7-dibutyl-1,3-adamantane were synthesized by the coupling reaction of
3-bromo-1,1%-biadamantane or 3-bromo-5,5%,7,7%-tetrabutyl-1,1%-biadamantane with sodium in n-octane or with magnesium in
diethyl ether. Although the former 1,3-adamantane tetramer showed poor solubility in organic solvents, the latter tetrameric
5,7-dibutyl-1,3-adamantane was readily soluble in THF, chloroform and benzene and was successfully characterized by NMR, IR,
SEC and elemental analyses. © 2001 Elsevier Science Ltd. All rights reserved.
Adamantane (tricyclo[3.3.1.13,7]decane) is a highly sym-
metrical (Td symmetry) cage compound and shows
good chemical and thermal stability, and various func-
tional groups can be introduced on the tertiary bridge-
head carbon under suitable reaction conditions.1,2
Interestingly, adamantane can be thought of as a large
carbon atom because of the tetrahedral location of four
methine carbons and the direction of four bridgehead
CꢀH bonds. Therefore, 1,1%-biadamantane (1) can be
considered as a large analog of ethane, and higher
oligo(1,3-adamantane)s having flexible cage–cage bond-
ing corresponding to propane, butane, pentane and so
on. It also should be pointed out that the structure of
the diamond involves the framework of oligo(1,3-
adamantane)s in its lattice, since adamantane can be
recognized as the repeating unit of the diamond, as
shown in Fig. 1. To the best of our knowledge,
although the dimeric adamantane 1 was synthesized
long ago via the Wurtz coupling reaction of 1-bro-
moadamantane,1 no higher oligomers have been
obtained. In this communication, we report the first
successful synthesis of tetrameric 1,3-adamantane
showing good solubility in organic solvents by intro-
ducing flexible butyl substituents on the framework.
afforded a mixture of 3-bromo-1,1%-biadamantane (2)3
and 3,3%-dibromo-1,1%-biadamantane (3).1,4 Column
chromatography (silica gel, hexane/CH2Cl2=9/1, v/v)
of the reaction mixture gave 2 in 58% and 3 in 40%
yield. The isolated monobromide 2 was subsequently
reacted with sodium in n-octane under reflux conditions
to form a proposed tetramer of adamantane 4, via the
bridgehead coupling reaction. An off-white solid was
obtained in good yield after the usual workup of the
reaction mixture. By assuming the complete removal of
bromine from 2, the yield of product was almost quan-
titative. After Soxhlet extraction with THF, the reduced
dimer 1 was recovered in 42% yield from the product
as a soluble fraction. The residue of white powder
Figure 1. Structure of poly(1,3-adamantane) in diamond lat-
tice.
The synthesis of 1,3-adamantane tetramer is depicted in
Scheme 1. The bromination of 1 with Br2 in CCl4
b
54%
a
58%
Br
Keywords: 5,7-dibutyl-1,3-adamantane tetramer; coupling reaction;
bridgehead carbon; 3-bromo-5,5%,7,7%-tetrabutyl-1,1%-biadamantane;
solubility.
* Corresponding author. Fax: +81-3-5734-2887; e-mail: tishizon@
polymer.titech.ac.jp
1
2
4
Scheme 1. Reagents and conditions: (a) Br2, CCl4, 30°C, 72 h;
(b) Na, n-octane, reflux, 12 h.
0040-4039/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(01)01825-1

8646
T. Ishizone et al. / Tetrahedron Letters 42 (2001) 8645–8647
d
c
b
a
C4H9
CH2CH2CH2CH3
C4H9
C4H9
C4H9
C4H9
Br
3
2
1
4
7
b
c, d
42%
b
97%
a
48%
e
60%
f
6
5
Br
96%
48%
4
3
2
C4H9
C4H9
Br
C4H9
C4H9
9
5
6
7
8
d
c
b
a
d' c' b' a'
a' b' c' d'
H3CH2CH2CH2C
d
c
b
a
C4H9
C4H9
CH2CH2CH2CH3 CH2CH2CH2CH3
CH2CH2CH2CH3
10
3
10
3
11
13 12
11
C4H9
11
12
4
5
2
1
9
2
1
4
5
9
8
14
7
7
e
11%
8
14
13
6
6
Br
2
11
4
3
10
3
9
4
9
10
2
C4H9
C4H9
C4H9
C4H9
C4H9
12
10
Scheme 2. Reagents and conditions: (a) C4H9MgBr, CH2Cl2, reflux, 12 h; (b) Br2, 105°C, 5 h; (c) silver triflate, 2,2-dimethylbutane,
0°C, 3 h; (d) C4H9MgBr, Et2O, rt, 12 h; (e) Mg, Et2O, reflux, 48 h; (f) Br2, CCl4, 30°C, 72 h.
(ꢀ54%), which was unfortunately insoluble in any
organic solvents, could be identified as 4 by the IR
spectroscopy and the elemental analysis.5 However, the
poor solubility of 4 precluded its complete characteriza-
tion by NMR spectroscopy and size exclusion chro-
matography (SEC) measurement.
that all four sp3 carbon signals attributed to the butyl
group were split into two signals showing the same
intensities. This is probably due to the small difference
in the chemical shifts of the butyl substituents on either
the inner or outer adamantane framework of the tetra-
mer. Thus, we have succeeded in the synthesis of a
thermally-stable9 tetrameric 1,3-adamantane derivative
bearing solubility-enhancing butyl groups. Unfortu-
nately, crystals suitable for an X-ray analysis of 12 have
not yet been obtained. The resulting 5,7-dibutyl-1,3-
adamantane tetramer 12 possesses two terminal
methine carbons capable of further chemical modifica-
tions (bromination and coupling reaction) and opens
up a synthetic pathway to novel higher oligomers hav-
ing well-defined nano-architecture.
We then introduced two butyl substituents into the
adamantane repeating unit to increase the solubility of
the oligomeric products, and a series of oligo(5,7-
dibutyl-1,3-adamantane)s was synthesized as shown in
Scheme 2. The introduction of a butyl substituent on
the bridgehead carbon of the adamantyl skeleton was
achieved in 48% yield by the reaction of 1-bromo-
adamantane and butylmagnesium bromide in
dichloromethane as previously reported.6 The resulting
1-butyladamantane (5) was brominated with Br2 to
afford 1-bromo-3-butyladamantane (6) in 96% yield.
After treating 6 with silver triflate in 2,2-dimethylbu-
tane,7 butylmagnesium bromide in diethyl ether was
added to the reaction mixture to give 1,3-dibutyl-
adamantane (7) in 42% yield. The reaction of 7 with Br2
gave 1-bromo-3,5-dibutyladamantane (8) in 97% yield.
The magnesium-mediated coupling reaction of 8 in
diethyl ether8 and the following recrystallization pro-
vided a symmetrical dimer, 3,3%,5,5%-tetrabutyl-1,1%-
biadamantane (9) in 60% yield. The bromination of 9
with Br2 under diluted conditions in CCl4 and column
chromatography (silica gel, hexane) afforded a mono-
bromide (10) in 48% yield along with a dibromide (11)4
in 43% yield. The resulting monobromide 10 was then
allowed to react with magnesium in diethyl ether under
reflux condition to give a tetramer of dibutyladaman-
tane 12. It is suggested from the NMR and SEC
analyses that the coupling reaction smoothly proceeded
and the bromide was completely consumed to give a
mixture of the reduced dimer 9 and the tetramer 12.
The tetramer, soluble in benzene, chloroform and THF,
was successfully obtained in 11% yield after repeated
recrystallization from diethyl ether, and the isolation of
Acknowledgements
This work was partially supported by the Tokuyama
Foundation.
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5. Selected data for 2: off-white solid, mp 147–148°C, 1H
NMR (CDCl3, 300 MHz): 1.53–1.70 (m, 18H), 1.98 (bs,
3H), 2.16–2.33 (m, 8H); 13C NMR (CDCl3, 75 MHz): 29.0,
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1
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1
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1
mp 73–74°C, H NMR (CDCl3, 300 MHz): 0.90 (t, 12H,
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37.9 (C1), 40.6 (C2), 42.0 (C4), 44.8 (Cd), 47.2 (C7); IR

T. Ishizone et al. / Tetrahedron Letters 42 (2001) 8645–8647
8647
(KBr) 1320, 1466, 2836, 2893, 2926, 2952 cm−1. For 10:
colorless liquid, 1H NMR (CDCl3, 300 MHz): 0.91 (t,
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1.95 (m, 4H), 2.06 (bs, 3H, CH ); 13C NMR (CDCl3, 75
MHz): 14.24 and 14.32 (Ca,a%), 23.7 and 23.8 (Cb,b%),
24.98 and 25.05 (Cc,c%), 29.7 (C12), 33.6 (C10) 35.1 (C13),
38.17 (C3), 38.25 (C8), 39.0 (C2), 40.7 (C9), 41.8 (C11),
43.2 (C1), 43.6 (Cd), 44.6 (Cd%), 45.3 (C7), 47.0 (C14),
47.1 (C6), 53.5 (C4), 70.2 (C5); IR (neat) 735, 839 (C-Br),
1174, 1321, 1348, 1450, 2845, 2896, 2928 cm−1. For 12:
off-white solid, mp 206–207°C, 1H NMR (CDCl3, 300
MHz): 0.88–0.94 (2t, 24H, CH3, J=7 Hz), 0.98–1.30 (m,
88H), 1.44 (s, 8H), 2.06 (bs, 2H, terminal CH); 13C NMR
(CDCl3, 75 MHz): 14.20 and 14.22 (Ca,a%), 23.9 and 24.0
(Cb,b%), 25.1 and 25.2 (Cc,c%), 30.0 (C12), 33.1 (C6), 33.7
and 34.0 (C3 and C10), 35.3 (C13), 38.41 and 38.44 (C1
and C5), 38.7 (C8), 40.3 (C4), 40.7 (C2), 41.1 (C9), 42.0
(C11), 44.7 and 45.1 (Cd,d%), 46.7 (C7), 47.2 (C14); IR
(KBr) 1341, 1446, 1483, 2856, 2897, 2926, 2952 cm−1
.
Anal calcd for C72H122 (987.8): C, 87.55; H, 12.45; found:
C, 87.83; H, 12.17.
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temperatures for 10% weight loss occurred at 404 and
383°C, respectively.