Synthesis and structure of 2,6,14- and 2,7,14-trisubstituted triptycene derivatives

Article abstract of DOI:10.1021/jo061067t

A series of 2,6,14- and 2,7,14-trisubstituted triptycene derivatives were efficiently synthesized and their structures were determined by NMR, MS spectra, and X-ray analysis. These trisubstituted triptycenes are potential building blocks for constructing novel receptors and synthetic molecular machines.

Full text of DOI:10.1021/jo061067t

Synthesis and Structure of 2,6,14- and
2,7,14-Trisubstituted Triptycene Derivatives
Chun Zhang†,‡ and Chuan-Feng Chen*,†
Center for Molecular Science, Institute of Chemistry, Chinese
Academy of Sciences, Beijing 100080, China, and Graduate
School, Chinese Academy of Sciences, Beijing 100049, China
cchen@iccas.ac.cn
ReceiVed May 25, 2006
A series of 2,6,14- and 2,7,14-trisubstituted triptycene
derivatives were efficiently synthesized and their structures
were determined by NMR, MS spectra, and X-ray analysis.
These trisubstituted triptycenes are potential building blocks
for constructing novel receptors and synthetic molecular
machines.
FIGURE 1. (a) Two views of the crystal structure of compound 2b;
(b) crystal packing of 2b viewed along the a-axis. Hydrogen atoms
are omitted for clarity.
shown to be useful building blocks in constructing molecular
devices and synthetic molecular machines.7
Recently, we8 were interested in the development of new
supramolecular systems based on triptycene. Consequently,
some of triptycene derivatives with unique structure and
properties are needed. Herein we report the efficient synthesis
of a series of 2,6,14- and 2,7,14-trisubstituted triptycene
derivatives, which are potential building blocks for constructing
novel receptors and synthetic molecular machines.
Triptycene1 and its derivatives are a class of interesting
compounds with three-dimensional rigid frameworks. They have
been found to have unique electrochemical and photochemical
properties,2 interesting reactivities,3 potential pharmaceutical
properties,4 and attractive applications in supramolecular chem-
istry5 and materials science.6 Moreover, they have also been
2,6,14-Trinitrotriptycene and 2,7,14-trinitrotriptycene were
first synthesized as byproducts in 19739 by the reaction of
triptycene and acetyl nitrate in the presence of acetic anhydride
and glacial acetic acid. Recently, MacLachlan et al.10 reported
that the nitration of triptycene with concentrated HNO3 gave
† Institute of Chemistry, Chinese Academy of Sciences.
‡ Graduate School, Chinese Academy of Sciences.
(1) Bartlett, P. D.; Ryan, M. J.; Cohen, S. G. J. Am. Chem. Soc. 1942,
64, 2649-2653.
(2) (a) Satrijo, A.; Swager, T. M. Macromolecules 2005, 38, 4054-4057.
(b) Perepichka, D. F.; Bendikov, M.; Meng, H.; Wudl, F. J. Am. Chem.
Soc. 2003, 125, 10190-10191. (c) Beyeler, A.; Belser, P. Coord. Chem.
ReV. 2002, 230, 28-38. (d) Korth, O.; Wiehe, A.; Kurreck, H.; Ro¨der, B.
Chem. Phys. 1999, 246, 363-372. (e) Norvez, S.; Barzoukas, M. Chem.
Phys. Lett. 1990, 165, 41-44.
(6) (a) Long, T. M.; Swager, T. M. J. Am. Chem. Soc. 2002, 124, 3826-
3827. (b) Long, T. M.; Swager, T. M. J. Am. Chem. Soc. 2003, 125, 14113-
14119. (c) Zhu, Z.; Swager, T. M. J. Am. Chem. Soc. 2002, 124, 9670-
9671. (d) Yang, J.-S.; Swager, T. M. J. Am. Chem. Soc. 1998, 120, 5321-
5322. (e) Yang, J.-S.; Swager, T. M. J. Am. Chem. Soc. 1998, 120, 11864-
11873. (f) Yang, J.-S.; Lin, C.-S.; Hwang, C.-Y. Org. Lett. 2001, 3, 889-
892. (g) Norvez, S. J. Org. Chem. 1993, 58, 2414-2418.
(7) (a) Iwamura, H.; Mislow, K. Acc. Chem. Res. 1988, 21, 175-182.
(b) Kelly, T. R.; Bowyer, M. C.; Bhaskar, K. V.; Bebbington, D.; Garcia,
A.; Lang, F.; Kim, M. H.; Jette, M. P. J. Am. Chem. Soc. 1994, 116, 3657-
3658. (c) Kelly, T. R.; Silva, R. A.; Silva, H. D.; Jasmin, S.; Zhao, Y. J.
Am. Chem. Soc. 2000, 122, 6935-6949. (d) Godinez, C. E.; Zepeda, G.;
Garcia-Garibay, M. A. J. Am. Chem. Soc. 2002, 124, 4701-4707. (e)
Annunziata, R.; Benaglia, M.; Cinquini, M.; Raimondi, L.; Cozzi, F. J.
Phys. Org. Chem. 2004, 17, 749-751.
(8) (a) Zhu, X. Z.; Chen, C. F. J. Am. Chem. Soc. 2005, 127, 13158-
13159. (b) Zong, Q. S.; Chen, C. F. Org. Lett. 2006, 8, 211-214. (c) Han,
T.; Chen, C. F. Org. Lett. 2006, 8, 1069-1072. (d) Zong, Q. S.; Zhang, C.;
Chen, C. F. Org. Lett. 2006, 8, 1859-1862. (e) Zhu, X. Z.; Chen, C. F.
Chem.sEur. J. 2006, 12, 5603-5609. (f) Gong, K. P.; Zhu, X. Z.; Zhao,
R.; Xiong, S. X.; Mao, L. Q.; Chen, C. F. Anal. Chem. 2005, 77, 8158-
8165.
(3) (a) Marks, V.; Nahmany, M.; Gottlieb, H. E.; Biali, S. E. J. Org.
Chem. 2002, 67, 7898-7901. (b) Lu, J.; Zhang, J.; Shen, X.; Ho, D. M.;
Pascal, R. A., Jr. J. Am. Chem. Soc. 2002, 124, 8035-8041. (c) Iiba, E.;
Hirai, K.; Tomioka, H.; Yoshioka, Y. J. Am. Chem. Soc. 2002, 124, 14308-
14309. (d) Spyroudis, S.; Xanthopoulou, N. J. Org. Chem. 2002, 67, 4612-
4614. (e) Spyroudis, S.; Xanthopoulou, N. Tetrahedron Lett. 2003, 44,
3767-3770. (f) Zhu, X. Z.; Chen, C. F. J. Org. Chem. 2005, 70, 917-924.
(4) (a) Hua, D. H.; Tamura, M.; Huang, X.; Stephany, H. A.; Helfrich,
B. A.; Perchellet, E. M.; Sperfslage, B. J.; Perchellet, J.-P.; Jiang, S.; Kyle,
D. E.; Chiang, P. K. J. Org. Chem. 2002, 67, 2907-2912. (b) Perchellet,
E. M.; Magill, M. J.; Huang, X.; Brantis, C. E.; Hua, D. H.; Perchellet,
J.-P. Anti-Cancer Drugs 1999, 10, 749-766. (c) Yang, W.; Perchellet, E.
M.; Tamura, M.; Hua, D. H.; Perchellet, J. P. Cancer Lett. 2002, 188, 73-
83.
(5) (a) Marc Veen, E.; Postma, P. M.; Jonkman, H. T.; Spek, A. L.;
Feringa, B. L. Chem. Commun. 1999, 1709-1710. (b) Yang, J.-S.; Liu,
C.-P.; Lee, G.-H. Tetrahedron Lett. 2000, 41, 7911-7915. (c) Yang, J.-S.;
Lee, C.-C.; Yau, S.-L.; Chang, C.-C.; Lee, C.-C.; Leu, J.-M. J. Org. Chem.
2000, 65, 871-877. (d) Yang, J.-S.; Liu, C.-P.; Lin, B. C.; Tu, C. W.; Lee,
G. H. J. Org. Chem. 2002, 67, 7343-7354.
(9) Shigeru, T.; Ryusei, K. J. Am. Chem. Soc. 1973, 95, 4976-4986.
10.1021/jo061067t CCC: $33.50 © 2006 American Chemical Society
Published on Web 07/28/2006
6626
J. Org. Chem. 2006, 71, 6626-6629

SCHEME 1
SCHEME 2
the 2,6,14-trinitrotriptycene in 33% yield as the sole isolated
product. Following the same nitration condition as above, we
found that by increasing the reactive temperature and prolonging
the reactive time not only 2,6,14-trinitrotriptycene 2a was
obtained in 64% yield, but also 2,7,14-trinitrotriptycene 2b could
be isolated in 21% yield (Scheme 1). Compared with that of
diazonium ions are easily prepared by the reaction of an aniline
with nitrous acid generated in situ from a nitrite salt. Conse-
quently, the triaminotriptycenes could be considered as useful
precursors for the preparation of other trisubstituted triptycene
derivatives.
As shown in Scheme 2, when compound 3a was treated with
the aqueous solution of sodium nitrite and concentrated sulfuric
acid, the trihydroxytriptycene 4a could be obtained in 75% yield.
Treating compound 3a with a solution of sodium nitrite in
concentrated hydrobromic acid and water and then with CuBr
gave tribromotriptycene 5a in 68% yield. Similarly, triiodo-
triptycene 6a was synthesized in 71% yield by the reaction of
the diazonium salt derived from 3a with KI. Compounds 4a,
1
compound 2a, H NMR spectrum of compound 2b shows a
very simple splitted mode of aromatic protons and much
different shifts for the two bridgehead protons. Moreover, 11
signals for the aromatic carbons of 2a were observed while 13
C
NMR spectrum of 2b shows only 6 signals for the aromatic
carbons. These observations are all consistent with the C3
symmetric structure of 2b.
The structure of 2,7,14-trinitrotriptycene 2b was further
determined by its X-ray single-crystal analysis. Single crystals
of 2b suitable for X-ray diffraction were obtained by slow
evaporation of a CH2Cl2/hexane solution. As shown in Figure
1a, the three nitro groups in 2b are positioned in the same
direction, and one of the benzene rings is a little distorted.
Moreover, it was found that 2b could pack into microporous
networks (Figure 1b), in which multiple N-O‚‚‚H-C hydrogen
bonds and π-π stacking interactions played an important role
(Supporting Information).
The trinitrotriptycenes could be easily reduced by Raney Ni
in the presence of hydroazine to afford the corresponding
triaminotriptycenes in almost quantitative yields. It was known
that the aryl diazonium salts are the most broadly useful
substrates for nucleophilic aromatic substitution, and aryl
1
5a, and 6a were all characterized by the H NMR, 13C NMR,
and MS spectra, respectively.
Under the same conditions as above, compounds 4b, 5b, and
6b were synthesized in 81%, 62%, and 80% yields, respectively,
by the aromatic substitution via diazonium ions derived from
the triaminotriptycene 3b (Scheme 3). Compounds 4b, 5b, and
6b all showed six signals for the aromatic carbons and two
signals for the bridgehead carbons in their 13C NMR spectra.
Consequently, they all have the C3 symmetric structure, in which
the three substituted groups are positioned in the same direction.
We further obtained the single crystals of 6b suitable for X-ray
analysis from vapor diffusion of n-pentane into dichloromethane
solution. As expected, its crystal structure (Figure 2) shows the
same results as those in solution. Moreover, it was found that
compound 6a could also pack into a microporous structure by
the multiple I‚‚‚I and C-I‚‚‚π interactions11 (Supporting
Information).
(10) Chong, J. H.; MacLachlan, M. J. Inorg. Chem. 2006, 45, 1442-
1444.
J. Org. Chem, Vol. 71, No. 17, 2006 6627

SCHEME 3
General Method for Synthesis of Triaminotriptycenes 3a and
3b. To a solution of compound 3a or 3b (1.0 g, 2.6 mmol) in THF
(20 mL) was added hydrazine monohydrate (1.5 mL) and Raney
Ni (∼1.0 g). After heating at 60 °C until all hydrazine was
quenched, the mixture was cooled to room temperature and then
filtered. The filtrate was concentrated by rotary evaporation to
remove the solvent, and the product as a white solid was obtained
in quantitative yield.
Compound 3a: mp 290-292 °C (lit. 279-283 °C10). 1H NMR
(300 MHz, CDCl3): δ 3.47 (s, 6H), 5.01 (s, 1H), 5.04 (s, 1H),
6.21-6.26 (m, 3H), 6.69-6.73 (m, 3H), 7.04-7.07 (m, 3H). 13C
NMR (75 MHz, DMSO): δ 51.3, 52.5, 108.2, 108.5, 109.8, 110.2,
122.9, 123.3, 133.2, 134.1, 145.3, 145.5, 147.0, 147.8. EI-MS: m/z
299 (M+).
Compound 3b: mp 152-154 °C. 1H NMR (300 MHz, CDCl3):
δ 3.40 (s, 6H), 4.97 (s, 1H), 5.05 (s, 1H), 6.23 (dd, J ) 7.7, 2.1
Hz, 3H), 6.70 (d, J ) 7.7 Hz, 3H), 7.03 (d, J ) 2.1 Hz, 3H). 13C
NMR (75 MHz, CDCl3): δ 51.5, 54.5, 110.9, 111.7, 123.4, 137.3,
143.4, 146.4. HRMS calcd for C20H17N3, [M]+ 299.1422; found,
299.1418.
General Method for Synthesis of Trihydroxytriptycenes 4a
and 4b. To a solution of 3a or 3b (0.6 g, 2.0 mmol) in concentrated
sulfuric acid (2 mL) and water (10 mL) cooled in an ice-salt bath
was added dropwise a solution of sodium nitrite (0.4 g, 7.0 mmol)
in water (5 mL) for over 10 min. After being stirred for 20 min,
the mixture was slowly added into the refluxing solution of
concentrated sulfuric acid (10 mL) and water (15 mL) over 30 min.
The mixture was refluxed for another 2 h, cooled, and then extracted
with ether (30 mL × 3). The combined extracts were washed with
water (20 mL × 2), dried over anhydrous sodium sulfate, and
concentrated to remove the solvent. The residue was subjected to
chromatography on silica gel with dichloromethane/petroleum ether
(1:2) as eluent to give the product as a pale yellow solid.
Compound 4a: yield, 75%; mp > 300 °C. 1H NMR (300 MHz,
acetone-d6): δ 5.23 (s, 2H), 5.04 (s, 1H), 6.36-6.40 (m, 3H), 6.89-
6.91 (m, 3H), 7.11-7.16 (m, 3H). 13C NMR (75 MHz, acetone-
d6): 52.2, 53.2, 109.9, 110.1, 111.1, 111.3, 123.6, 123.9, 136.5,
137.3, 147.8, 148.5, 154.6, 154.8. HRMS calcd for C20H14O3, [M]+
302.0943; found, 302.0941.
In summary, we have provided an efficient method for the
synthesis of a series of both 2,6,14- and 2,7,14-trisubstituted
triptycene derivatives in reasonable yields, which could be
potential building blocks for constructing novel receptors and
synthetic molecular machines, and studies on them are undergo-
ing.
Experimental Section
Synthesis of Trinitrotriptycenes 2a and 2b. To triptycene 1
(2.5 g, 10 mmol) was added concentrated HNO3 (100 mL) and the
mixture was heated at 75 °C for 24 h. The brown solution was
cooled to room temperature, then poured into H2O (1000 mL) and
stirred. The precipitate was collected, washed with cooled water,
and then dried in air. The crude products were separated by column
chromatography on silica gel with dichloromethane/petroleum ether
(1:1) as eluent to afford the white solids 2a (2.5 g) and 2b (0.82
g).
Compound 2a: yield, 64%; mp 178-180 °C (lit. 173-17610
or 180 °C9). 1H NMR (300 MHz, CDCl3): δ 5.82 (s, 1H), 5.84 (s,
1H), 7.62-7.67 (m, 3H), 8.03-8.07 (m, 3H), 8.32-8.34 (m, 3H).
Compound 2b: yield, 21%; mp > 300 °C. 1H NMR (300 MHz,
CDCl3): δ 5.80 (s, 1H), 5.84 (s, 1H), 7.62 (d, J ) 8.2 Hz, 3H),
8.05 (dd, J ) 8.2, 2.2 Hz, 3H), 8.34 (d, J ) 2.2 Hz, 3H). 13C NMR
(75 MHz, CDCl3): δ 53.1, 53.6, 119.5, 122.5, 125.0, 144.7, 146.3,
148.8. EI-MS: m/z 389 (M+). Anal. Calcd for C20H11N3O6: C,
61.70; H, 2.85; N, 10.79. Found: C, 61.84; H, 2.95; N, 10.53.
(11) (a) Metrangolo, P.; Neukirch, H.; Pilati, T.; Resnati, G. Acc. Chem.
Res. 2005, 38, 386-395. (b) Pigge, F. C.; Vangala, V. R.; Swenson, D. C.
Chem. Commun. 2006, 2123-2125.
FIGURE 2. The crystal structure of compound 6b.
6628 J. Org. Chem., Vol. 71, No. 17, 2006

Compound 4b: yield, 81%; mp > 300 °C. 1H NMR (300 MHz,
acetone-d6): δ 5.23 (s, 1H), 5.24 (s, 1H), 6.39 (dd, J ) 7.9, 2.4
Hz, 3H), 6.93 (d, J ) 7.9 Hz, 3H), 7.12 (d, J ) 2.4 Hz, 3H). 13C
NMR (75 MHz, acetone-d6): δ 51.2, 54.1, 110.3, 111.6, 123.3,
138.0, 147.1, 154.5. HRMS calcd for C20H14O3, [M]+ 302.0943;
found, 302.0944.
hydrochloric acid (5 mL) and water (10 mL) cooled in an ice-salt
bath was added dropwise a solution of sodium nitrite (0.4 g, 7.0
mmol) in water (5 mL) for over 10 min. After the mixture was
stirred for another 20 min, potassium iodide (2.5 g, 15.0 mmol) in
water (5 mL) was added dropwise over 30 min. The mixture was
heated at 80 °C for 2 h, cooled, and then extracted with dichlo-
romethane (30 mL × 3). The combined extracts were washed with
saturated sodium bisulfate (20 mL × 2), dried over anhydrous
sodium sulfate, and concentrated to remove the solvent. The residue
was subjected to chromatography on silica gel with dichloromethane
and petroleum ether (1:4) as eluent to give the product as a white
solid.
General Method for Synthesis of Tribromotriptycenes 5a and
5b. To a solution of 3a or 3b (1.0 g, 3.6 mmol) in concentrated
hydrobromic acid (3 mL) and water (10 mL) cooled in an ice-salt
bath was added dropwise a solution of sodium nitrite (0.8 g, 12.6
mmol) in water (5 mL) for over 10 min. After being stirred for 20
min, the mixture was slowly added into the refluxing mixture of
CuBr (2.2 g, 15.0 mmol) and concentrated hydrobromic acid (5
mL) over 30 min. The mixture was refluxed for another 2 h, cooled,
and then extracted with dichloromethane (30 mL × 3). The
combined extracts were washed with water (20 mL × 2), dried
over anhydrous sodium sulfate, and concentrated to remove the
solvent. The residue was subjected to chromatography on silica
gel with dichloromethane and petroleum ether (1:10) as eluent to
give the product as a white solid.
1
Compound 6a: yield, 71%; mp 155-157 °C. H NMR (300
MHz, CDCl3): δ 5.23 (s, 1H), 5.25 (s, 1H), 7.09 (d, J ) 7.7 Hz,
3H), 7.34 (dd, J ) 7.7, 1.5 Hz, 3H), 7.69 (d, J ) 1.5 Hz, 3H). 13
C
NMR (75 MHz, CDCl3): 52.4, 52.5, 90.5, 125.7, 125.8, 132.8,
132.9, 134.6, 143.7, 143.9, 146.5, 146.8. EI-MS: m/z 631 (M+).
Anal. Calcd for C20H11I3: C, 38.01; H, 1.75. Found: C, 38.10; H,
1.77.
1
Compound 6b: yield, 80%; mp 164-166 °C. H NMR (300
1
Compound 5a: yield, 68%; mp 127-129 °C. H NMR (300
MHz, CDCl3): δ 5.22 (s, 1H), 5.27 (s, 1H), 7.10 (d, J ) 7.7 Hz,
MHz, CDCl3): δ 5.26 (s, 1H), 5.29 (s, 1H), 7.12 (dd, J ) 7.8, 1.8
Hz, 3H), 7.20 (d, J ) 7.8 Hz, 3H), 7.49 (d, J ) 1.8 Hz, 3H). 13C
NMR (75 MHz, CDCl3): 52.6, 52.7, 119.1, 119.2, 125.3, 125.4,
127.1, 127.2, 128.47, 128.51, 143.0, 143.3, 146.4, 146.7. EI-MS:
m/z 490 (M+), 492 (M+ + 2). Anal. Calcd for C20H11Br3: C, 48.92;
H, 2.26. Found: C, 48.61; H, 2.44.
3H), 7.34 (dd, J ) 7.7, 1.5 Hz, 3H), 7.69 (d, J ) 1.5 Hz, 3H). 13
C
NMR (75 MHz, CDCl3): δ 52.3, 52.6, 90.4, 125.6, 132.9, 134.6,
144.2, 146.3. EI-MS: m/z 631 (M+). Anal. Calcd for C20H11I3: C,
38.01; H, 1.75. Found: C, 38.15; H, 1.82.
Acknowledgment. We thank the National Natural Science
Foundation of China and the Chinese Academy of Sciences for
financial support.
1
Compound 5b: yield, 62%; mp 121-123 °C. H NMR (300
MHz, CDCl3): δ 5.25 (s, 1H), 5.31 (s, 1H), 7.13 (dd, J ) 7.8, 1.8
Hz, 3H), 7.21 (d, J ) 7.8 Hz, 3H), 7.49 (d, J ) 1.8 Hz, 3H). 13C
NMR (75 MHz, CDCl3): δ 52.4, 52.8, 119.1, 125.2, 127.2, 128.6,
143.5, 146.1. EI-MS: m/z 490 (M+), 492(M+ + 2). Anal. Calcd
for C20H11Br3: C, 48.92; H, 2.26. Found: C, 48.65; H, 2.39.
General Method for Synthesis of Triiodotriptycenes 6a and
6b. To a solution of 3a or 3b (0.6 g, 2.0 mmol) in concentrated
Supporting Information Available: 1H and 13C NMR spectra
for compounds 2a,b, 3a,b, 4a,b, 5a,b, 6a,b; X-ray crystallographic
files (CIF) for 2b and 6b. This material is available free of charge
via the Internet at http://pubs.acs.org.
JO061067T
J. Org. Chem, Vol. 71, No. 17, 2006 6629