Molecular Crystals with Moving Parts: Synthesis, Characterization, and Crystal Packing of Molecular Gyroscopes with Methyl-Substituted Triptycyl Frames

Article abstract of DOI:10.1021/jo035517i

We report a highly convergent synthesis for the preparation of molecular gyroscopes consisting of para-phenylene rotors linked by triple bonds to methyl-substituted triptycenes acting as pivots and encapsulating frames. The desired 1,4-bis[2-(2,3,6,7,12,1

Full text of DOI:10.1021/jo035517i

Molecu la r Cr ysta ls w ith Movin g P a r ts: Syn th esis,
Ch a r a cter iza tion , a n d Cr ysta l P a ck in g of Molecu la r Gyr oscop es
w ith Meth yl-Su bstitu ted Tr ip tycyl F r a m es
Carlos E. Godinez,† Gerardo Zepeda,‡ Christopher J . Mortko,† Hung Dang,† and
Miguel A. Garcia-Garibay*,†
Department of Chemistry and Biochemistry, University of California, Los Angeles,
Los Angeles, California 90095-1569, and Departamento de Quimica Organica,
Escuela Nacional de Ciencias Biologicas, IPN, Mexico, D.F. 11340
mgg@chem.ucla.edu
Received October 14, 2003
We report a highly convergent synthesis for the preparation of molecular gyroscopes consisting of
para-phenylene rotors linked by triple bonds to methyl-substituted triptycenes acting as pivots
and encapsulating frames. The desired 1,4-bis[2-(2,3,6,7,12,13-hexamethyl-10-alkyl-9-triptycyl)-
ethynyl]benzenes were prepared from 2,3-dimethyl-1,3-butadiene using Diels-Alder cycloadditions
and Pd(0)-catalyzed coupling as the key reactions. The main challenge in the synthesis came about
in the preparation of 9-alkynyl-triptycenes by Diels-Alder reaction of benzynes and 9-alkynyl-
2,3,6,7-tetramethylanthracenes. These reactions occurred with chemical yields and regioselectivities
that were strongly influenced by steric and electronic effects of substituents at C10 of the anthracene
core. Anthracenes with methyl, propyl, and phenyl substituents were utilized to complete the
synthesis of their corresponding molecular gyroscopes, and their solid-state structures were
determined by single-crystal X-ray diffraction analysis. Examination of these results indicated that,
as expected, the bulky triptycyl groups encourage crystallization motifs that create more free volume
around the phenylene rotor, as needed to facilitate fast gyroscopic motion in the solid state.
In tr od u ction
materials built with molecules that are structurally
programmed to undergo rapid motions in the solid
state.5,6 In particular, we have suggested a new class of
electrooptic materials with dipolar units that can reorient
in the presence of external fields7 and which may find a
wide range of applications in the field of photonics.8 The
desired solids rely on molecular architectures possessing
rigid, encapsulating structures capable of supporting
highly mobile parts even in a close-packed environment
(Figure 1). By form and function, these molecules re-
semble macroscopic compasses and gyroscopes, with the
designation of choice depending on their state of motion
and whether they have a permanent dipole that can
reorient in the presence of external electromagnetic
It has been suggested that supramolecular interactions
and the solid-state behavior in organic compounds are
ultimately determined by information contained in their
molecular structures.1,2 With that in mind, solid-state
organic chemists have made progress toward the design
of specific packing arrangements3 and the reliable design
of chemical reactions in crystals.4 With a similar premise,
we recently began to explore the design of solid-state
† University of California, Los Angeles.
‡ Escuela Nacional de Ciencias Biologicas, IPN.
(1) Lehn, J .-M. Supramolecular Chemistry. Concepts and Perspec-
tives; VCH: Weinheim, 1995; Chapter 2.
(2) Garcia-Garibay, M. A. Curr. Opin. Solid State Mater. Sci. 1998,
3/ 4, 399-406.
(3) (a) Braga, D.; Desiraju, G. R.; Miller, J . S.; Price, S. L. Crys-
tEngComm 2002, 4, 500-509. (b) Desiraju, G. R. Acc. Chem. Res. 2002,
35, 565-573. (c) Hollingsworth, M. D. Science 2002, 295, 2410-2413.
(d) Desiraju, G. R. Curr. Opin. Solid State Mater. Sci. 1997, 2, 451-
455. (e) Su, D.; Wang, X.; Simard, M.; Wuest, J . D. Supramol. Chem.
1995, 61, 171-178. (f) Stang, P. J .; Olenyuk, B. Acc. Chem. Res. 1997,
30, 502-518. (g) Leininger, S.; Olenyuk, B.; Stang, P. J . Chem. Rev.
2000, 100, 853-907. (h) Moulton, B.; Zaworotko, M. J . Chem. Rev.
2001, 101, 1629-1658. (i) Zaworotko, M. J . Angew. Chem., Int. Ed.
2000, 39, 3052-3054. (j) Barton, T. J .; Bull, L. M.; Klemperer, W. G.;
Loy, D. A.; McEnaney, B.; Misono, M.; Monson, P. A.; Pez, G.; Scherer,
G. W.; Vartuli, J . C.; Yaghi, O. M. Chem. Mater. 1999, 11, 2633-2656.
(k) Eddaoudi, M.; Moler, D. B.; Li, H.; Chen, B.; Reineke, T. M.;
O’Keeffe, M.; Yaghi, O. M. Acc. Chem. Res. 2001, 34, 319-330.
(4) (a) Garcia-Garibay, M. A. Acc. Chem. Res. 2003, 36, 491-498.
(b) Campos, L. M.; Ng, D.; Yang, Z.; Dang, H.; Martinez, H. L.; Garcia-
Garibay, M. A. J . Org. Chem. 2002, 67, 3749-3754. (c) Papaefstathiou,
G. S.; Kipp, A. J .; MacGillivray, L. R. Chem. Commun. 2001, 2462-
2463. (d) MacGillivray, L. R.; Reid, J . L.; Ripmeester, J . A. J . Am.
Chem. Soc. 2000, 122, 7817-7818. (e) Gamlin, J . N.; J ones, R.;
Leibovitch, M.; Patrick, B.; Scheffer, J . R.; Trotter, J . Acc. Chem. Res.
1996, 29, 203-209. (f) Toda, F. Acc. Chem. Res. 1995, 28, 480-486.
(5) (a) Dominguez, Z.; Dang,, H.; Strouse, M. J .; Garcia-Garibay, M.
A. J . Am. Chem. Soc. 2001, 124, 2398-2399. (b) Dominguez, Z.; Dang,
H.; Strouse, M. J .; Garcia-Garibay, M. A. J . Am. Chem. Soc. 2001, 124,
7719-7727.
(6) For leading reviews addressing molecular motion in crystals,
please see: (a) Gavezzoti, A.; Simonetta, M. In Organic Solid State
Chemistry; Desiraju, G., Ed.; Elsevier: Amsterdam, 1987; pp 391-
432. (b) Gavezzotti, A. Mol. Cryst. Liq. Cryst. 1988, 156A, 25-33. (c)
Dunitz, J .; Maverick, E. F.; Trueblood, K. N. Angew. Chem., Int. Ed.
Engl. 1988, 27, 880-895. (d) Horii, F.; Kaji, H.; Ishida, H.; Kuwabara,
K.; Masuda, K.; Tai, T. J . Mol. Struct. 1998, 441, 303-311.
(7) A similar concept based on reorienting units mounted on surfaces
has recently been proposed: (a) Vacek, J .; Michl, J . Proc. Natl. Acad.
Sci. U.S.A. 2001, 98, 5481-5486. (b) Clarke, L. I.; Horinek, D.; Kottas,
G. S.; Varaksa, N.; Magnera, T. F.; Hinderer, T. P.; Horansky, R. D.;
Michl, J .; Price, J . C. Nanotechnology 2002, 13, 533-540.
(8) (a) Salech, B. E. A.; Teich, M. C. Fundamentals of Photonics;
Wiley-Interscience: New York, 1991. (b) Setian, L. Applications in
Electrooptics; Prentice Hall: New York, 2001. (c) Kasap, S. O.
Optoelectronic and Photonics: Principles and Practices; Prentice
Hall: New York, 2001. (d) Weber, M. J . Handbook of Optical Materials;
CRC Press: Boca Raton, 2002.
10.1021/jo035517i CCC: $27.50 © 2004 American Chemical Society
Published on Web 02/06/2004
1652
J . Org. Chem. 2004, 69, 1652-1662

Molecular Crystals with Moving Parts
SCHEME 1
SCHEME 2
F IGURE 1. (a) Schematic analogies between a macroscopic
gyroscope and simple molecules built with a diethynylphe-
nylene linked to two bulky triptycene groups. (b) Idealized
representation of a crystal lattice built with “molecular
gyroscopes”.
Using various aromatic groups as potential rotors, we
recently reported a simple synthetic approach for the
synthesis of simple triptycene-based compounds (Scheme
1).10 A detailed analysis of the X-ray structure of the
phenylene-containing compound 1 revealed a dense
packing arrangement where the protuberant triptycenes
of one molecule fill in the cavities around the central
phenylene of its close neighbors in the crystal lattice.10
Not surprisingly, the phenylene group of each molecule
experiences aromatic π,π-stacking and edge-to-face in-
teractions with triptycenes from neighboring molecules,
and these contacts prevent the desired gyroscopic motion
in the solid state. To change this packing motif for one
where free volume is created around the central phe-
nylene rotor, we reasoned that bulky substituents along
the periphery of the triptycene rings should help separate
adjacent molecules, thus creating the desired cavity
(Scheme 1). Although bulky R-groups or bridging chains
at positions 2, 3, 6, 7, 12, and 13 of each triptycene, as
shown in Figure 1a, would be highly desirable, we
decided to explore and establish a suitable synthetic
method with the hexamethyl-substituted “molecular
gyroscope” 2 (R ) Me, R1 ) H) as the target. We describe
here studies of a highly convergent synthetic strategy
fields. The structures of these molecules consist of a 1,4-
diethynylphenylene with its two ends linked to triaryl-
methanes9 or triptycenes.10 Ideally, fast rotation of the
central phenylene is facilitated by the nearly frictionless
motion about alkyne-aryl single bonds11 and by the
shielding provided by the bulky framework of the triph-
enylmethane or triptycene groups. Crystals built with
these molecules have been ideally designed to have a
rigid component that maintains the integrity and rigidity
of the lattice and a mobile component that maintains a
state of motion under suitable temperatures and experi-
mental conditions. To convey the contrasting dynamic
behavior of the two components in a graphic manner, we
represent rigid parts in blue color and moving parts in
red.
(9) Analogous structures have been proposed as pinwheel receptors
for metal ion recognition in solution: Raker, J .; Glass, T. E. Tetrahe-
dron 2001, 57, 10233-10240.
(10) Godinez, C. E.; Zepeda, G.; Garcia-Garibay, M. A. J . Am. Chem.
Soc. 2002, 124, 4701-4707.
(11) (a) Saebo, S.; Almolof, J .; Boggs, J . E.; Stark, J . G. J . Mol. Struct.
(THEOCHEM) 1989, 200, 361-373. (b) Sipachev, V. A.; Khaikin, L.
S.; Grikina, O. E.; Nikitin, V. S.; Traettberg, M. J . Mol. Struct. 2000,
523, 1-22.
J . Org. Chem, Vol. 69, No. 5, 2004 1653

Godinez et al.
SCHEME 3 a
SCHEME 4 a
a
Conditions: (a) 90 °C, C6H6; (b) S/I2 decalin, Ph2O; (c) NaOH;
(d) NaOCl, NaOH.
that required a thorough investigation of the Diels-Alder
reaction between substituted anthracenes and benzynes
to form the desired triptycenes. Once the preparation of
the ethynyl triptycenes was optimized, we completed the
synthesis of compounds with methyl, propyl, and phenyl
substituents at the bridgehead position of the two trip-
tycyl units (Scheme 2, R ) Me, R1 ) Me, Pr, Ph). Finally,
our expectations regarding the role of substituents at the
peripheral position of the triptycene groups was con-
firmed by X-ray structure analysis of the R1 ) Ph and
R1 ) Pr derivatives.
a
Conditions: (a) 115 °C, EtOH, press. bottle; (b) KOH, EtOH,
O2; (c) Sno, HCl; (d) LiAlH4 or R1MgBr; (d) CuBr2/C6H5Cl or Br2/
CCl4; (e) KOH, Bu4Nl, PhH, reflux; (f) 2-methylbut-3-yne-2-ol,
Pd(Ph3P)2Cl2, piperidine, reflux.
Resu lts a n d Discu ssion
A desirable synthetic sequence for the preparation of
molecular gyroscopes with hexasubstituted triptycene
frames should be succint, highy convergent, and have
many opportunities for structural variation and func-
tionalization. On the basis of our recent experience,2,10
we envisioned a procedure that involves a double-Pd(0)-
catalyzed coupling reaction between para-arylene halides
and 2 equiv of the 9-ethynyl hexamethyl tripycene 3 as
previously reported for the synthesis of the parent rotor
1 (Scheme 2). Although installation of the terminal
alkyne in 3 could be achieved from a number of two-
carbon synthons at the bridgehead position of an hex-
amethyl triptycene, retrosynthetic analysis suggested a
highly convergent approach based on Diels-Alder reac-
tions through protected alkynyl anthracene 4 and 4,5-
dialkylbenzyne 5. Ideally, the substituted anthracene 4
and 4,5-dialkyl anthranilic acid 6 should provide all the
alkyl groups in molecular gyroscope 2 from the same 2,3-
dialkyl-1,3-butadiene (Scheme 2).
As a starting point, we targeted the synthesis of the
hexamethyl-substituted rotor 2 (R ) Me, R1 ) H, Scheme
1). We made this choice knowing that 2,3-dimethyl-1,3-
butadiene as a starting material would also give us ready
access to a large number of 2,3-dialkyl-1,3-butadiene
derivatives by dialkylation of the tetramethylene dianion,
as reported by Bender and Mu¨llen.12 We developed a
simple method for the synthesis of 4,5-dimethylanthra-
nilic acid 6b (Scheme 3) from 2,3-dimethylbutadiene and
maleic anhydride and took advantage of literature pro-
cedures for the preparation of 9-alkynyl-2,3,6,7-tetram-
ethylanthracenes 4a -e13 (Scheme 4).
The preparation of 3,4-dimethyl-anthranilic14 acid from
2,3-dimethyl-1,3-butadiene was carried out by a minor
modification of the method used by Hess and co-workers
for the synthesis of 2-amino-4(3H)-quinazolinones.15 Rather
than preparing 3,4-dimethylphthalimide 7 from 3,4-
dimethylphthalic anhydride and ammonia, we prepared
it by direct Diels-Alder reaction between 2,3-dimethylb-
utadiene and maleimide at 80 °C in benzene, followed
by aromatization with yellow sulfur and I2 in a mixture
of decaline and diphenyl ether at 182 °C (Scheme 3).
Phthalimide 7 was treated with 1 N KOH to give
phthalamic acid 8 in quantitative yield, and in the final
step, a Hoffman rearrangement in the presence of NaOCl
and NaOH yielded the desired anthranilic acid 6b in 84%
yield after purification by column chromatography. At-
tempts to carry out the hydrolysis and Hoffman rear-
rangement in a single pot to avoid the isolation of 7
resulted in a substantial drop in the final yield to only
52%, and this procedure was ultimately avoided.
The synthesis of acetone-protected 9-alkynyl tetram-
ethylanthracenes 4a -e started with a Diels-Alder reac-
tion between 2,3-dimethylbutadiene and benzoquinone.
The protected alkynes are significantly easier to handle
as compared to the unprotected terminal alkynes, which
are known to polymerize readily.16 Optimum yields of the
corresponding tetrahydroanthraquinone (>90%) were
obtained when the reaction was carried out with 4 equiv
of the diene in a pressure tube in ethanol at 105 °C for
(14) The first reported synthesis of 4,5-dimethyl anthranilic acid 5
starts from 3,4-dimethylaniline and exploits an intramolecular Friedel-
Crafts reaction to install the ortho-carboxylic acid: Baker, R.; Schaub,
R. E.; J oseph, P. J .; McEvoy, F. J .; Williams, J . H. J . Org. Chem. 1951,
17, 149-156.
(15) Hess, H. J .; Cronin, T. H.; Scriabine, A. J . Med. Chem. 1968,
11, 130-136.
Su bstitu ted An th r a cen es a n d An th r a n ilic Acid s.
(12) Bender, D.; Mu¨llen, K. Chem. Ber. 1988, 121, 1187-1197.
(13) (a) Morgan, G. T.; Coulson, E. A. J . Chem. Soc. 1931, 2323-
2331. (b) Hinshaw, J . C. Org. Prep. Proc. Int. 1972, 4, 211-213.
1654 J . Org. Chem., Vol. 69, No. 5, 2004

Molecular Crystals with Moving Parts
SCHEME 5
28 h. A quantitative aromatization reaction in this case
was carried out by autoxidation of the tetrahydroan-
thraquinone in ethanolic KOH with bubbling O2 to yield
2,3,6,7-teramethylanthraquinone. A convenient trans-
formation of the intermediate anthraquinone to 2,3,6,7-
tetramethylanthrone 9 was accomplished in 82% isolated
yield by a Clemensen reduction with Sno and HCl.17
Anthrone 9 is a very important intermediate because it
allows the introduction of numerous substituents (R1) at
C9 of the desired anthracene core by nucleophilic addition
followed by acid-catalyzed dehydration and aromatiza-
tion. While simple LiAlH4 addition followed by treatment
with HCl gives rise to tetramethylanthracene 10a , the
addition of MeMgBr, PrMgBr, HexMgBr, and PhMgBr
followed by dehydration lead to formation of the 9-sub-
stituted anthracenes 10b-e in 80-90% yield with some
of the anthrone recovered. It should be pointed out that
anthrone 9 and anthracene 10a are highly insoluble and
very difficult to handle and purify. In contrast, an-
thracenes 10b-d have a higher solubility and are much
easier to manipulate.
The installation of the acetone-protected acetylene
group in anthracenes 4a -e was carried out by C10-
bromination followed by Sonogashira coupling with 2-me-
thylbut-3-yne-2-ol.18,19 The bromination of 10a was com-
plicated by its low solubility and had to be carried out
with CuBr2 in refluxing chlorobenzene.20 Bromoan-
thracene 11a was obtained in 85% yield with some
unreacted starting material and some 9,10-dibromoan-
thracene. Compounds 11b-e were obtained in nearly
quantitative yields by slow addition of diluted Br2 to
solutions of 10b-e, respectively, in CCl4. Standard
Sonogashira conditions were used to prepare the alkynyl-
substituted anthracenes 4a-e from the bromoanthracenes
11a -e and 2-methylbut-3-yne-2-ol. Although purification
of 11a from unreacted starting material and the dibromo
compound had been essentially impossible, the purifica-
tion of 4a by column chromatography was satisfactory.
Compounds 4b-e were isolated, purified, and character-
ized with relative ease.
P r ep a r a tion of Eth yn yl Tr ip tycen es by Diels-
Ald er Ad d ition of Ben zyn es to 9-Alk yn yl An th r a -
cen es. Our initial studies of the Diels-Alder reaction
begun with formation of the alkynyl-substituted trip-
tycene 3a from dimethyl anthranilic acid 6b and alkynyl-
substituted tetramethylanthracene 4a (Scheme 5). The
reaction was carried out by simultaneous slow addition
of dimethyl anthranilic acid 6b and iso-amyl nitrite into
a refluxing solution of anthracene 4a in dimethoxyethane
as reported by Friedman.21 The total consumption of
anthracene 4a required up to 5 equiv of the relatively
expensive anthranilic acid 6b. Unfortunately, 1H and 13C
NMR analysis of the reaction mixture revealed products
formed by benzyne addition not only across the 9,10-
position to yield the desired alkynyl triptycene 3a , but
also products across the 1,4-position of the anthracene
core to yield the undesired naphthobenzobarrelene 12a
(Scheme 5). The desired triptycene 3a has an average
C3v symmetry and was easily identified in the reaction
mixture by its relatively simple 1H NMR spectrum, which
included two sets of methyl signals from the aromatic
triptycene core at 2.14 and 2.11 ppm, a signal from the
two methyls of the protected alkyne at 1.89 ppm, two
aromatic singlets at 7.10 and 7.35 ppm, and the charac-
teristic bridgehead hydrogen at 5.15 ppm. Signals cor-
responding to 12a reflected its lower symmetry, including
six nonequivalent aromatic methyl signals (2.22, 2.25,
2.34, 2.39, 2.44, and 2.49 ppm), a singlet with twice the
intensity assigned to the methyl groups of the protected
acetylene (1.82 ppm), and two nonequivalent bridgehead
hydrogens at 4.68 and 5.20 ppm. High-resolution mass
spectral analysis confirmed the isomeric nature of the
two compounds as well as their expected mass. The ratio
of 3a :12a was 50:50, and their separation by chromato-
graphic and fractional crystallization procedures turned
out to be exceedingly difficult, giving rise to very low
isolated yields.
The difficult separation of the two addition products
and the need to improve the yield of the desired alkynyl
triptycene encouraged us to investigate the effect of
9-alkynyl and/or 10-alkyl substituents on the tetram-
ethylanthracene core with compounds 4b-e and 10b-
e. In the case of anthracene 4a , it appeared that
activation at positions C1 and C4 by the methyl substit-
uents at positions C2 and C3 along with deactivation at
9,10-positions by the electron-withdrawing alkyne group
may have contributed to the results listed in the first
(16) (a) Dumitrscu, S.; Grigora, M.; Surpateanu, G. Rev. Roumaine
Chim. 1984, 29, 447-456. (b) Michel, R. H. J . Polym. Sci. A 1966, 5,
920-926. (c) Simionescu, C. I.; Dumitrscu, S.; Grigora, M.; Negulescu,
I. J . Macromol. Sci. Chem. 1979, A13, 203-218.
(17) (a) Pakush, J .; Ru¨chardt, C. Chem. Ber. 1990, 123, 2147-2151.
(b) Meyer, K. H. Organic Syntheses; Wiley: New York, 1941; Collect.
Vol. I, pp 60-61.
(18) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett.
1975, 4467-4470.
(19) Pugh, C.; Percec, V. Polymer Bull. 1990, 23, 177-184.
(20) Nonhebel, D. C. J . Chem. Soc. 1963, 1216-1220.
(21) Friedman, L.; Logullo, F. M. J . Org. Chem. 1969, 34, 3089-
3092.
J . Org. Chem, Vol. 69, No. 5, 2004 1655

Godinez et al.
TABLE 1. Regioselectivity of Ad d ition in th e Diels-Ald er Rea ction of Sever a l An th r a cen es a n d Ben zyn esa
triptycene
(9,10-adduct)
naphthobarrelene
(1,4-adduct)
entry
anthraceneb
R
R1
R2
aac
R3
1
2
3
4
5
6
7
8
9
10
11
12
13
4a
Me
H
H
H
H
H
Me
Me
Pr
Hex
Hex
Ph
Ph
Me
Pr
HMBd
HMBd
H
6b
6b
6b
6a
6a
6a
6a
6a
6a
6a
6a
6b
6b
Me
Me
Me
H
H
H
H
H
H
H
3a , 50
3a (H)e, 100
17a , 100
15a , 50
15b, 92
17b, 94
17c, 90
15d , 80
17d , 86
15e, 55
17e, 85
3b, 92
12a , 50
12a (H)e, 0
18a , 0
4a (H)e
10a
4a
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
HMBd
HMBd
H
16a , 50
16b, 8
18b, 6
18c, 10
16d , 20
18d , 14
16e, 45
18e, 15
12b, 6
4b
10b
10c
4d
10d
4e
10e
4b
4c
H
HMBd
H
HMBd
H
H
Me
Me
HMBd
HMBd
3c, 96
12c, 4
a
Product ratios were determined by 1H NMR integration of bridgehead hydrogens and/or aromatic methyl groups. bSubstituted
anthracenes. cAnthranilic acids. dHMB ) 3-hydroxy-3-methyl-1-butynyl. e4a (H), 3a (H), and 12a (H) refer to the analogues of 4a , 3a , and
12a , respectively, without the aromatic methyl groups.
entry of Table 1. To test this, we first analyzed the
outcome of reactions of the nonmethylated alkynyl an-
thracene 4a (H) and tetramethyl anthracene 10a , respec-
tively, with 4,5-dimethyl anthranilic 6b (Table 1, entries
2 and 3). We determined the regioselectivity of addition
P r ep a r a tion of Molecu la r Gyr oscop es by P d (0)-
Ca ta lyzed Cou p lin g of Alk yn yltr ip tycen es a n d 1,4-
Diiod oben zen e. Once substituents and conditions had
been optimized to give the desired triptycenes, reactions
were scaled up with 2,3,6,7,9-pentamethylanthracene
10b and 9-propyl-2,3,6,7-tetramethyl anthracene 4c with
dimethyl anthranilic acid 6b to prepare alkynyl trip-
tycenes 3b and 3c (Scheme 6). As expected, the selectivity
of addition was excellent (Table 1, entries 12 and 13),
and their purification reasonably simple. Samples of the
9-phenyl derivative 15e with one of the aromatic rings
lacking the two methyl groups were also prepared and
carried to the final molecular gyroscope (12H,13H)-2e
(Scheme 6). To complete the synthesis of molecular
gyroscopes 2b and 2c and (12H,13H)-2e (from now on
referred to as 2eH), it only remained to deprotect the
terminal alkynes by hydroxide catalysis followed by a
double Pd(0)-catalyzed coupling reaction with 1,4-diiodo-
benzene as illustrated in Scheme 6. Initially, reactions
were explored in one pot by in situ deprotection and
double Pd(0)-catalyzed coupling reaction using the condi-
tions reported by Percec et al. for the synthesis of oligo-
(akynylarylenes).19 Later, we discovered that overall
reaction yields are improved by a stepwise deprotection
and coupling procedure. The terminal alkynes 3bH, 3cH,
and 15eH were obtained in essentially quantitative yields
by elimination of acetone from 3b, 3c, and 15e with KOH
and NBu4I in refluxing benzene (Scheme 6). The double-
coupling reaction was subsequently carried out under
reflux with 0.9 equiv of para-diiodophenylene in the
presence of 20% PdCl2(PPh3)2 in deoxygenated piperidine.
Analysis of the reaction mixtures revealed the desired
molecular gyroscopes along with small amounts of alkyne
dimers formed by oxidative coupling of two terminal
alkynes. While purification of compounds 2c and 2eH
was possible by column chromatography, we were unable
to purify 2b from its corresponding alkyne dimer, which
was formed as a side product.
1
on these and subsequent reactions by simple H NMR
integration of the bridgehead signals corresponding to
the triptycene and naphthobenzobarrelenes in the region
of 4.3-5.3 ppm, as well as aromatic methyl signals in
the region of 2.0-2.6 ppm. The results shown in entries
2 and 3 confirmed our suspicions regarding the combined
role of methyl and alkynyl susbtituents on the reactivity
of anthracene benzynophiles. Neither a single alkyne
substituent in 4a (H) nor the four methyl groups in 10a
are sufficient to cause the formation of the corresponding
naphthobarrelenes 12a (H) or 18a . The results in entry
4 helped verify that the parent benzyne, from anthranilic
acid 6a , reacts with anthracene 4a in the same manner
as dimethyl benzyne from 6b, giving a 50:50 mixture of
regioisomers 15a and 16a . This result suggested that the
effect of substituents on the anthracene core could be
evaluated using the cheaper anthranilic acid as a ben-
zyne precursor (entries 5-11).
Reaction selectivities were explored with 2,3,6,7-tet-
ramethylanthracenes with various 10-alkyl substituents
(R1 ) Me, Pr, Hex, and Ph), either with (10b-e) or
without (4b-e) the alkyne substituent at C9. The results
in entries 5-11 show that the selectivity of addition can
be influenced by a combination of electronic and steric
effects. The highest selectivity for 9,10-addition was
observed with a methyl group at C9 (entries 5 and 6) and
the lowest with a phenyl substituent (entries 10 and 11).
A comparison of results with anthracenes 4 and 10
indicates that methyl, propyl, and hexyl substituents at
C9 have a dominating influence on the selectivity of
addition as compared to the alkyne group at C10. While
weakly deactivating phenyl and alkynyl substituents
have additive effects, giving a 55:45 ratio of 9,10- (15e)
and 2,4-addition (16e) products (entry 10), a single
phenyl group at C9 increased the selectivity of 17e:18e
to 85:15 (entry 11). Assuming similar electronic effects,
differences in selectivity between methyl, propyl, and
hexyl reveal a deleterious steric influence which, in the
case of 4d , leads to the formation of the undesirable 2,4-
adduct 16d in up to 20% (entry 8).
Characterization of the three compounds was carried
out by standard spectroscopic techniques and confirmed
the expected structures. Notably, with molecular masses
that range from 826.45 to 894.4 amu, the three molecular
gyroscopes give rise to relatively strong parent ion signals
under electron impact ionization with a high-resolution
mass detector (EI-HRMS). Although alkyne stretching
1656 J . Org. Chem., Vol. 69, No. 5, 2004

Molecular Crystals with Moving Parts
SCHEME 6 a
a
Referred to as 2eH in the text.
bands expected near 2200 cm-1 in the FTIR spectra were
too weak to be observed, strong aliphatic and aromatic
signals are consistent with the anticipated structures.
1
The H NMR spectra of 2b, 2c, and 2eH are character-
ized by the time-average symmetries of their triptycyl
and phenylene groups.
Molecular gyroscopes 2b, 2c, and 2eH are white solids
with remarkably different solubilities. While 2c is highly
soluble in a large number of solvents, including aliphatic
and aromatic hydrocarbons, the per-methyl-substituted
2b and phenyl derivative 2eH are sparingly soluble in
hot halogenated solvents such as tetrachloroethane,
chlorobenzene, and bromobenzene. No melting can be
observed in any of the three compounds, and the onset
of thermal decomposition occurs above 350 °C. Despite
numerous attempts using a wide range of solvents and
conditions, we were unable to obtain diffraction-quality
crystals of molecular gyroscope 2b, perhaps due to the
presence of small amounts of the alkyne dimer. Fortu-
nately, single crystals of 2c and 2eH were obtained from
bromobenzene and meta-xylene, respectively, and were
investigated by X-ray diffraction.
X-r a y Str u ctu r es. Diffraction data from crystals of
molecular gyroscopes 2c and 2eH were acquired at 100
K. Compounds 2c and 2eH were obtained as colorless
prisms from bromobenzene and meta-xylene, respectively.
The main crystallographic parameters of the two crystal
structures are listed in Table 1, and crystallographic
information files (CIF) have been included in Supporting
Information.
As crystals of the phenyl-substituted molecular gyro-
scope 2eH first became available, its molecular and
crystal structures were first analyzed. The structure was
solved in the space group P1-bar with two independent
molecular halves and one molecule of meta-xylene in the
asymmetric unit. Application of the inversion center
dictated by the space group gives rise to two distinct
molecular structures (molecules I and II) and two mol-
ecules of meta-xylene per unit cell (Figure 2). The two
structures of 2eH are very similar to each other with the
planes of the triptycyl rings in a staggered conformation,
as given by dihedral angles close to ca. 60° (Figure 2a).
As required by their crystallographic and molecular
F IGURE 2. (a) ORTEP diagram of the two crystallographi-
cally independent molecules of rotor 2eH (molecules I and II)
with thermal ellipsoids at the 50% probability level. (b) Partial
packing diagram of rotor 2eH (space group P1-bar) illustrating
a layer of molecules II with the meta-xylene molecules (in light
blue) near the central phenylene. Close π-π stacking interac-
tions between phenyl substituents at the bridgehead position
between neighboring rotor molecules (shown in magenta) can
also be appreciated.
inversion center, the two structures have the planes of
the nonmethylated rings (labeled A and A′ in Figure 2a)
anti to each other. The planes of the bridgehead phenyl
groups (ring B) of molecules I and II make very similar
dihedral angles with the plane of ring A (32.0 and 32.6°,
respectively), and the most significant difference between
the two structures is the conformation of their central
J . Org. Chem, Vol. 69, No. 5, 2004 1657

Godinez et al.
F IGURE 3. Space-filling models from the X-ray structure of
molecular gyroscope 2eH illustrating the local arrangement
between the phenylene group of molecules I and II and the
closest two molecules of meta-xylene.
TABLE 2. Ma in Cr ysta llogr a p h ic P a r a m eter s for
Molecu la r Rotor s 2eH a n d 2ca
empirical formula
C
70H54-C8H10
C
68H66-2C6H5Br
(2eH)
(2c)
formula weight
crystal system
space group
Z
1001.29
triclinic
P1-bar
1197.23
triclinic
P1-bar
2
2
size, mm3
0.3 × 0.2 × 0.1
colorless prisms
100(2)
0.40 × 0.39 × 0.08
a
a
color, habit
temperature, K
colorless prisms
100(2)
F IGURE 4. (a) ORTEP diagram of rotor 2c with thermal
ellipsoids drawn at the 50% probability level. (b) Partial view
of the packing arrangement illustrating the desired spacing
between molecules of 2c and their arrangement in layers that
run in a direction that is 105° from their long molecular axis.
The location of bromobenzene molecules in light blue and
orange around the central phenylene (in red) is also shown.
unit cell dimensions
a, Å
b, Å
c, Å
10.672(3)
13.741(4)
20.206(6)
109.772(7)
99.286(6)
2739.1(14)
1.214
9.4694(11)
16.0213(18)
21.933(3)
81.887(2)
78.878(2)
3231.9(6)
1.230
â, deg
γ, deg
V, Å3
∼6.7-7.5 Å. Not surprisingly, the separation of adjacent
molecules creates large cavities that are filled by the
meta-xylene molecules and the local environment around
the central phenylene groups of molecules I and II is
significantly different (Figure 3). While the phenylene
group of molecule I is “sandwiched” between two mol-
ecules of meta-xylene in a parallel cofacial interaction
with an interplanar distance of only 3.78 Å, the phenyl-
ene group of molecule II has a nonparallel, C-H-π, edge-
on relationship with the two molecules of meta-xylene.
It can also be appreciated in Figure 3 that the two meta-
xylene molecules are related in each case by the crystal-
lographic inversion symmetry at the center of molecules
I and II. An additional feature of the packing structure
is a π-π stacking interaction between the bridgehead
phenyl groups of adjacent molecular gyroscopes, which
are illustrated in magenta color in Figure 2b.
Although polycrystalline samples of molecular gyro-
scope 2c were obtained easily from a variety of solvents,
X-ray-quality samples could be systematically obtained
by slow evaporation from dilute bromobenzene solutions.
The structure was solved in the centrosymmetric space
group P1-bar with one molecular gyroscope and two
molecules of bromobenzene per asymmetric unit, which
corresponds to two molecules of 2c and four molecules
of bromobenzene per unit cell (Figure 4). The ORTEP
diagram of molecular gyroscope 2c, from data acquired
at 100 K, is illustrated in Figure 4a with thermal
Dc, Mg/m3
total reflections
15788
20966
14764
independent reflections 10677
[R(int) ) 0.0385] [R(int) ) 0.0236]
0.0493
0.1109
R1 [I > 2σ(I)]
wR2 (all data)
0.0595
0.1912
a
X-ray-quality single crystals for 2eH were grown from meta-
xylene. Crystals of 2c were grown from bromobenzene. Solvents
of crystallization were observed in both cases.
phenylene (ring C). The dihedral angles formed by the
planes of ring C and ring A are 23.2° for molecule I and
56.7° for molecule II. Both molecular structures present
deviations from linearity. The twofold symmetry axes of
the central phenylene (ring C) and bridgehead phenyl
groups (rings B) do not coincide with each other or with
a vector given by the two bridgehead carbons of the two
triptycenes. The magnitude of these deviations ranges
between 2 and 10°. The packing structure of 2eH has all
the molecules in the crystal aligned in the same direction
(Figure 2b). Although four peripheral methyl groups on
each triptycene allows for some interdigitation to occur
in the packing structure of 2eH (Figure 2), some of the
desirable features in Scheme 1 are realized. The close
interdigitation between nearest neighbors previously
observed in crystal of the parent triptycyl rotor (com-
pound 1) was modified into a packing structure that
separates the phenylene groups of adjacent molecules by
1658 J . Org. Chem., Vol. 69, No. 5, 2004

Molecular Crystals with Moving Parts
ellipsoids drawn at the 50% probability level. The rela-
tively large size and the direction of the long axis of the
thermal ellipsoids of the central phenylene, as compared
to those of the static triptycene carbons, suggest rela-
tively wide amplitude librations consistent with the
postulated gyroscopic motion.22 When viewed down the
molecular long axis, the two triptycyl groups adopt a
staggered conformation (60°) that is analogous to that
determined for molecular gyroscope 2eH. The plane of
the central phenylene is almost coincident with one of
the three triptycene planes, as given by a dihedral angle
of 4.4°. As previously noted in the case of 2eH, the
structure of 2c also deviates from linearity as the two
triptycene groups are pushed slightly above and below
with respect to the plane of the central phenylene as a
result of a small bending of the two alkyne bonds.
Remarkably, the packing structure of 2c is essentially
the same as the one proposed in our original design
(Scheme 1 and Figure 4b). The methyl groups on the
periphery of the two triptycenes prevent interdigitation
between adjacent molecular rotors, thus creating rela-
tively large cavities between them. As expected for a
relatively rigid rod, all the molecules in a crystal are
oriented in the same direction. Translation of molecular
rotors at an angle of 105.5° with respect to their molec-
ular long axes results in the formation of layers that are
segregated from each other by the propyl groups at the
two bridgehead positions. The local environment around
the central phenylene of each molecular rotor is shared
by six bromobenzene molecules, which pack in pairs, with
a face-to-edge interaction between their aromatic rings.
has a lower average symmetry with only four methyl
groups in each triptycene. Single-crystal X-ray analysis
of 2c and 2e(H) revealed the desired packing structures
with adjacent molecular gyroscopes being separated by
the peripheral methyl groups. Although the free volume
generated around the central phenylene was filled by
solvent molecules included during crystallization, pre-
2
liminary H NMR dynamic measurements indicate that
gyroscopic motion in crystals of 2c occurs with a very low
rotational barrier. In addition, preliminary analysis of
the atomic displacement parameters of 2c with the
THMA14C program of Trueblood and Maverick,22 as
implemented by Ferrugia,23 suggested a librational mo-
tion about the 1,4-phenylene axis with an amplitude of
98.7 (°)2 at 100 K. Assuming a twofold flipping model in
a symmetric periodic potential and a simple approxima-
tion that involves small excursions, one may calculate a
rotational barrier of only 3.3 kcal/mol. These and other
results illustrating a relatively efficient gyroscopic motion
will be reported in a subsequent paper.
Exp er im en ta l Section
Reagents and solvents were obtained from Aldrich Chemical
Co. and from Fisher and were of the highest purity available.
Anhydrous ether and THF were freshly by distilled from Na
still kept under an argon atmosphere. The 1H(13C) NMR
spectra were obtained on a Bruker NMR spectrometer operat-
ing at 500 MHz for 1H and at 125 MHz for 13C in CDCl3 or
C2D2Cl4 with TMS as an internal standard. IR spectra were
acquired on a Perkin-Elmer Paragon 1000 FT-IR instrument.
Gas chromatography analyses (GC) were recorded on a Hewlett-
Packard 5890 Series II capillary instrument equipped with a
flame ionization detector. Melting points were determined with
a Fisher-J ohns melting point apparatus and were not cor-
rected. Samples and 4,5-dimethylanthranilic acid 6b ,13,14
2,3,6,7-tetramethyl-9-anthrone 9, and 2,3,6,7-tetramethylan-
thracene 10a 11,12 were prepared by the sequence of reactions
shown in Schemes 4 and 5 using procedures reported in the
literature. Their physical properties and spectroscopic data
were in full agreement with those reported earlier.
Con clu sion
The synthesis of molecular gyroscopes with methyl
substituents at positions 2, 3, 6, 7, 12, and13 of the
triptycene core has been accomplished by a highly
convergent strategy. The reported procedure involves 12
equiv of 2,3-dimethyl-1,3-butadiene, 2 equiv of acetylene,
and 1 equiv of 1,4-diiodobenzene put together in only 13
steps by using Diels-Alder and Pd(0)-catalyzed coupling
reactions as the key transformations. Dimethyl anthra-
nilic acid 6b and tetramethyl-alkynyl anthracenes 4a -e
were prepared in four steps and ∼75% yield and six steps
and 53% yield, respectively, from 2,3-dimethyl-1,3-buta-
diene. We discovered that the Diels-Alder reaction of
9-alkynyl anthracenes and benzynes proceeds in chemical
yields and regioselectivities that are highly dependent
on the nature of the C-10 anthracene substituents. A
detailed analysis of this reaction indicated that electronic
and steric factors play important roles, and the best
results were obtained with the smaller electron-donating
methyl and propyl substituents at C10. The syntheses
of molecular gyroscopes 2b, 2c, and 2e(H), with methyl,
phenyl, and propyl substituents at the bridgehead posi-
tion, respectively, were completed. These compounds
were isolated in overall yields that depended on their
solubility and those of their triptycene precursors. While
molecular gyroscopes 2b and 2c possess six methyl
groups at each of their two triptycenes, compound 2e(H)
X-r a y Str u ctu r e Deter m in a tion . X-ray quality single
crystals of compounds 2eH (C70H54-C8H10) and 2c (C68H66-
-
2C6H5Br) were grown by slow evaporation from meta-xylene
and bromobenzene, respectively. A prism with approximate
dimensions was used for X-ray crystallographic analyses. The
X-ray intensity data were measured at either 298 or 100 K on
a
Bruker SMART 1000 CCD-based X-ray diffractometer
system equipped with a Mo-target X-ray tube (λ ) 0.71073 Å)
operated at 2250 W power. The detector was placed at a
distance of 4.986 cm from the crystal. A total of 1321 frames
were collected with a scan width of 0.3° in ω, with an exposure
time of 30 s/frame. The total data collection time was ca. 18
h. The frames were integrated with the Bruker SAINT
software package using a narrow-frame integration algorithm.
Analysis of the data showed negligible decay during the data
collection. The structure was refined on the basis of the
respective space groups, using the Bruker SHELXTL (Version
5.3) Software Package.
2,3,6,7,9-P en ta m eth yla n th r a cen e (10b). A flame-dried
three-neck 500 mL round-bottom flask was charged with
2,3,6,7-tetramethylanthrone (1.00 g, 3.99 mmol) and 200.0 mL
of anhydrous THF. The mixture was brought to reflux while
stirring. Upon reflux, 10.0 mL of 3 M CH3MgBr (30.0 mmol)
was added slowly. After the addition was complete, the
reaction was refluxed for 30 min. The reaction was quenched
with 30 mL of 0.1 M HCl and the product extracted twice with
ether. The combined ethereal extracts were washed with brine
(22) (a) Dunitz, J . D.; Maverick, E. F.; Trueblood, K. N. Angew.
Chem., Int. Ed. Engl. 1988, 27, 880-895. (b) Schomaker, V.; Trueblood,
K. N. Acta Crystallogr. 1998, B54, 507-514. (c) Dunitz, J . D. Mol.
Cryst. Liq. Cryst. Incorporating Nonlinear Opt. 1988, 156 (PtA), 11.
(23) Ferrugia, L. J . J . Appl. Cryst. 1999, 32, 837-838.
J . Org. Chem, Vol. 69, No. 5, 2004 1659

Godinez et al.
and dried over anhydrous magnesium sulfate. Removal of the
solvent under reduced pressure left residue that was
crystalline solid: mp 228-231 °C; 1H NMR (CDCl3) δ 8.23 (s,
1H), 7.74 (s, 2H), 7.57 (m, 2H), 7.52 (m, 1H), 7.40 (m, 2H),
7.32 (s, 2H), 2.44 (s, 6H), 2.31 (s, 6H); 13C NMR (CDCl3) δ
139.4, 135.0, 134.7, 134.4, 131.3, 130.5, 129.1, 128.3, 128.1,
127.1, 125.4, 123.8, 20.6, 20.2; IR (KBr) 3006, 2915, 1670, 1594,
1460, 1004, 891, 698 cm-1; HRMS (EI) calcd for C24H22
310.1722, found 310.1720.
9-Br om o-2,3,6,7-tetr a m eth yla n th r a cen e (11a ). Anthra-
cene 10a (2.3 g, 9.8 mmol) was dissolved in 55 mL of
chlorobenzene and followed by addition of CuBr2 (5.8 g, 26
mmol). The reaction mixture was heated to reflux for 1 h. The
crude product was washed with saturated NaHCO3 (3 × 15
mL), dried over anhydrous MgSO4, and concentrated under
vacuum. The crude product was 95% pure based on GC
analysis and used as obtained: mp 190-194 °C; 1H NMR
(CDCl3) δ 8.17 (s, 2H), 8.11 (s, 1H), 7.64 (s, 2H), 2.49 (s, 6H),
2.43 (s, 6H); 13C NMR (CDCl3) δ 137.1, 135.3, 131.1, 129.4,
127.3, 126.9, 126.8, 124.3, 20.7, 20.0; IR (KBr) 3009, 2970,
2914, 1638, 1458, 1266, 1004, 893, 859 cm-1; HRMS (EI) calcd
for C18H17Br 312.0514, found 312.0516.
10-Br om o-2,3,6,7,9-p en ta m eth yla n th r a cen e (11b). The
procedure described for the preparation of 11a was applied to
0.50 g of anthracene 10b (2.10 mmol) in 40.0 mL of CCl4 and
0.32 g of bromine (2.10 mmol) dissolved in 5.0 mL of CCl4.
The product 11b (0.51 g, 77%) was obtained as a pale yellow
powder: mp 240-241 °C; 1H NMR (CDCl3) δ 8.26 (s, 1H), 7.98
(s, 1H), 2.99 (s, 3H), 2.48 (s, 6H), 2.50 (s, 12H); 13C NMR
(CDCl3) δ 136.41, 135.03, 129.78, 129.09, 127.08, 127.19
124.02, 118.50, 20.53, 20.46, 14.23; IR (film) 3000, 2924, 2853,
1463, 1377 cm-1; HRMS (EI) calcd for C19H19Br 326.0870,
found 326.0670.
a
adsorbed on silica gel. Chromatography with a 95:5 solution
of hexanes/methylene chloride gave 10b as a light yellow
powder (0.75 g) in 76% yield: mp 199-200 °C; 1H NMR
(CDCl3) δ 8.09 (s, 1H), 8.01 (s, 2H), 7.72 (s, 2H), 3.05 (s, 3H),
2.53 (s, 6H), 2.48 (s, 6H); 13C NMR (CDCl3) δ 137.7, 134.3,
130.6, 129.1, 127.8, 127.3, 123.7, 122.6, 20.9, 20.2, 13.8; IR
(KBr) 3003, 2965, 2930, 2912, 1639, 1446, 1028, 998, 892, 857
cm-1; HRMS (EI) calcd for C19H20 248.1565, found 248.1572.
9-P r op yl-2,3,6,7-tetr a m eth yla n th r a cen e (10c). A flame-
dried three-neck 500 mL round-bottom flask was charged with
Mg turnings (1.52 g, 62.5 mmol). 1-Bromopropane (10.02 g,
81.46 mmol) was dissolved in 75 mL of anhydrous ether and
added dropwise to Mg via addition funnel. Upon formation of
the Grignard reagent, 2,3,6,7-tetramethylanthrone (1.4 g, 5.6
mmol) was suspended in 200 mL of ether and added slowly at
room temperature. The bright yellow mixture was refluxed for
10 min. The crude product was quenched with 30 mL of ice-
cold water followed by 10 mL of concentrated H2SO4 suspended
in 20 g of ice. The product was washed with water (3 × 50
mL) and brine (3 × 30 mL), dried over anhydrous MgSO4, and
concentrated under reduced pressure. The crude mixture was
suspended in 325 mL of hot hexanes and filtered to afford 0.95
g of 10c (88% yield based on 77% conversion of anthrone). The
recrystallized product from ethyl acetate afforded fine green
needles: mp 170-172 °C; 1H NMR (CDCl3) δ 8.05 (s, 1H), 7.94
(s, 2H), 7.68 (s, 2H), 3.49 (t, J ) 7.7 Hz, 3H), 2.49 (s, 6H), 2.41
(s, 6H), 1.83 (s, J ) 7.7, 2H), 1.14 (t, J ) 7.7 Hz); 13C NMR
(CDCl3) δ 14.6, 20.0, 20.9, 24.3, 29.8, 122.6, 123.3, 127.8, 128.5,
130.6, 132.4, 134.1, 134.6; IR (KBr) 3000, 2949, 2862, 1443,
999, 890, 854 cm-1; HRMS (EI) calcd for C21H24 276.1878,
found 276.1877.
9-P r opyl-10-br om o-2,3,6,7-tetr am eth ylan th r acen e (11c).
The procedure described for the preparation of 11a was applied
to 0.93 g of 2,3,6,7-tetramethyl-9-propylanthracene 10c (3.4
mmol) in 57 mL of CCl4 and 0.48 g of bromine (3.0 mmol) in
5 mL of CCl4. The product was washed with NaHCO3 (3 × 30
mL), NaHSO3 (2 × 30 mL), and brine (2 × 30 mL), dried over
MgSO4, and concentrated under vacuum to afford 1.1 g (91%
yield) of a greenish solid. The product was recrystallized from
EtOAc to afford 11c as fine needles: mp 204 °C dec; 1H NMR
(CDCl3) δ 8.27 (s, 2H), 7.95 (s, 2H), 3.49 (t, J ) 7.7 Hz, 2H),
2.51 (s, 12H), 1.82 (s, J ) 7.7 Hz, 2H), 1.15 (t, J ) 7.7 Hz,
3H); 13C NMR (CDCl3) δ 136.3, 135.0, 133.2, 129.2, 129.1,
127.2, 123.7, 118.6, 30.0, 24.4, 20.5, 20.4, 14.6; IR (KBr) 3050,
9-Hexyl-2,3,6,7-tetr a m eth yla n th r a cen e (10d ). A flame-
dried three-neck 500 mL round-bottom flask was charged with
Mg turnings (0.95 g, 39.1 mmol). 1-Bromohexane (7.29 g, 44.2
mmol) was dissolved in 100 mL of Et2O and added dropwise
to Mg via addition funnel. Upon formation of Grignard reagent,
2,3,6,7-tetramethylanthrone (1.01 g, 4.03 mmol) suspended in
50 mL ether was added slowly to Grignard reagent at room
temperature. The greenish mixture was refluxed for 10 min.
Crude product was transferred to a 1000 mL Erlenmeyer flask,
cooled in an ice bath, and quenched with 25 mL of ice-cold
water followed by 5 ml of concentrated H2SO4 suspended in
25 g of ice. Product was washed with water (3 × 30 mL) and
brine (2 × 30 mL), dried over MgSO4, and concentrated under
vacuum. The crude product was suspended on 100 mL of hot
hexanes and filtered to afford 0.67 g of product (52% yield).
The recrystallized product from methylene chloride afforded
10d as fine green needles: mp 146-148 °C; 1H NMR (CDCl3)
δ 8.05 (s, 1H), 7.93 (s, 2H), 7.68 (s, 2H), 3.50 (t, J ) 7.5 Hz,
2H), 2.49 (s, 6H), 2.44 (s, 6H), 1.77 (quintet, J ) 7.5 Hz, 2H),
1.58 (quintet, J ) 7.5 Hz, 2H), 1.40 (m, 4H), 0.91 (t, J ) 7.2
Hz, 3H); 13C NMR (CDCl3) δ 134.7, 134.2, 132.8, 130.7, 128.4,
127.9, 123.4, 122.7, 31.8, 31.2, 30.0, 27.8, 22.7, 21.0, 20.1, 14.1;
2949, 2862, 1447, 1006, 854 cm-1; HRMS (EI) calcd for C21H23
Br 354.0983, found 354.0969.
-
9-Hexyl-10-br om o-2,3,6,7-tetr am eth ylan th r acen e (11d).
A 25 mL three-neck round-bottom flask, fitted with an addition
funnel and a magnetic stir bar, was charged with 10 mL of
CCl4 and 9-hexyl-2,3,6,7-tetramethylanthracene 10d (0.11 g,
0.36 mmol). The suspension was heated to dissolve the
anthracene and cooled to room temperature. A solution of
bromine (1.0 mL in CCl4) was added dropwise at room
temperature in ca. 5 min. The product was washed with
NaHSO3 (2 × 15 mL), NaHCO3 (2 × 10 mL), and brine (2 ×
15 mL), dried over NaSO4, and concentrated under vacuum
to afford 0.143 g (100% yield) of 11d as a greenish white
solid: mp 132-135 °C dec; 1H NMR (CDCl3) δ 8.23 (2H), 7.90
(s, 2H), 3.45 (t, J ) 7.6 Hz, 2H), 2.47 (s, 12H), 1.75 (quintet, J
) 7.6 Hz, 2H), 1.57 (quintet, J ) 7.6 Hz, 2H), 1.38 (m, 4H),
0.91 (t, J ) 7.1 Hz, 3H); 13C NMR (CDCl3) δ 136.2, 134.9, 133.3,
129.1, 129.0, 127.2, 123.6, 118.5, 31.6, 31.0, 29.7, 27.9, 22.5,
20.3, 20.2, 14.0; IR (KBr) 3057, 3026, 2912, 2844, 1469, 1457,
1006, 854 cm-1; HRMS (MALDI) calcd for C24H29Br 396.1653,
found 396.1459.
IR (KBr) 3049, 3003, 2912, 2844, 1454, 1025, 889, 858 cm-1
;
HRMS (MALDI) calcd for C24H30 318.2348, found 318.2344.
9-P h en yl-2,3,6,7-tetr a m eth yla n th r a cen e (10e). A three-
neck 250 mL round-bottom flask was charged with Mg
turnings (0.75 g, 31.5 mmol), bromobenzene (4.0 g, 26.0 mmol)
was dissolved in 10 mL of ether and added dropwise to Mg
via addition funnel. Upon formation of the Grignard reagent,
2,3,6,7-tetramethylanthrone suspended in 40 mL of ether was
gradually added to the refluxing mixture. The bright yellow
mixture was refluxed for 4 h. The crude product was trans-
ferred to a 500 mL Erlenmeyer flask, cooled in an ice bath,
and quenched with ice and NH4Cl (aq). The product was
extracted with ether (3 × 50 mL). The combined organic layers
were washed with brine until neutral, dried with MgSO4, and
concentrated under vacuum to afford 10e as a light orange
crystalline solid. The crude product was purified via flash
chromatography in hexanes to afford 1.02 g (82% yield) of a
10-Br om o-2,3,6,7-tetr am eth yl-9-ph en ylan th r acen e (11e).
A 250 mL three-neck round-bottom flask was charged with
anthracene 10e (1.20 g, 3.87 mmol) and 77 mL of CCl4. A
solution of bromine (21.9 mL 0.36 M, 7.8 mmol) in CCl4 was
added dropwise at room temperature and allowed to stand for
3 h. The precipitate was collected by filtration and washed with
dilute NaOH (50 mL) to afford 11e as a white-greenish solid.
1660 J . Org. Chem., Vol. 69, No. 5, 2004

Molecular Crystals with Moving Parts
The filtrate was concentrated under vacuum, dissolved in
ether, washed with dilute NaOH (3 × 20 mL), dried over
MgSO4, and concentrated under vacuum to afford 1.48 g (96%)
J ) 7.0 Hz, 3H); 13C NMR (CDCl3) δ 135.8, 134.9, 134.8, 131.5,
128.0, 126.3, 123.8, 112.4, 31.9, 31.7, 31.2, 29.9, 28.1, 22.7, 20.8,
20.5, 14.l; IR (KBr) 3332, 3048, 2916, 2204, 1464, 854 cm-1
HRMS (EI) calcd for C29H36O 400.2766, found 399.2682.
;
1
of 11e as a white solid: mp >230 °C dec; H NMR (CDCl3) δ
8.29 (s, 2H) 7.55 (m, 3H), 7.36 (m, 2H), 7.29 (s, 2H), 2.49 (s,
6H), 2.31 (s, 6H); 13C NMR (CDCl3) δ 139.0, 136.9, 135.3, 135.2,
131.2, 129.9, 129.1, 128.4, 127.4, 126.6, 126.0, 119.9, 20.6, 20.3;
IR (KBr) 3053, 2972, 2913, 2853, 2729, 1595, 1462, 1442, 1330,
860, 694, 584 cm-1; HRMS (EI) calcd for C24H21Br 388.0827,
found 388.0833.
10-(3-Hydr oxy-3-m eth yl-1-bu tyn yl)-2,3,6,7-tetr am eth yl-
9-p h en yla n th r a cen e (4e). A three-neck 25 mL round-bottom
flask was charged with substituted bromoanthracene 11e
(0.052 g, 0.13 mmol) and (PPh3)2PdCl2 (0.014 g, 0.020 mmol)
and dissolved in 10 mL of degassed piperidine. 2-Methyl-3-
butyn-2-ol (0.14 mL, 0.12 g, 1.43 mmol) was added at once via
syringe. The reaction flask was heated at 82 °C in an oil bath
for 66 h. Piperidine was removed under vacuum and the crude
product purified by flash column chromatography, 93:7 hex-
anes/ethyl acetate, to afford 4e as a light orange solid 0.048 g
(92% yield): mp >230 °C dec; 1H NMR (CDCl3) δ 8.31 (s, 2H),
7.59 (m, 3H), 7.42 (dd, J ) 1.6, 8.2 Hz, 2H), 7.36 (s, 2H), 2.54
(s, 6H), 2.36 (s, 6H), 1.94 (s, 6H); 13C NMR (CDCl3) δ 138.9,
136.1, 135.9, 135.0, 131.2 131.0, 128.6, 128.2, 127.2, 125.9,
125.4, 113.6, 104.3, 79.6, 66.2, 31.5, 20.5, 20.3; IR (KBr) 3569,
9-(3-Hyd r oxy-3-m eth yl-1-bu tyn yl)-2,3,6,7-tetr a m eth y-
la n th r a cen e (4a ). A solution of 1.20 g (3.83 mmol) of
bromoanthracene 11a and 1.92 g (22.8 mmol) of 2-methyl-3-
butyn-2-ol in 50 mL of degassed piperidine was stirred at 80
°C, and 0.80 g of PdCl2(Ph3)2 (1.14 mmol, 30 mol %) was added.
After 40 h, the reaction was complete and the solvent was
evaporated under reduced pressure. The residue was dissolved
in ether and washed three times with a saturated solution of
NH4Cl and twice with deionized water. The ether layer was
dried over anhydrous MgSO4, and the solvent was removed
under reduced pressure. The residue was chromatographed
(silica 95%:5% hexanes/ethyl acetate) to give 0.914 g of 4a in
76% yield. The product was obtained as a pale yellow solid:
3430, 3053, 2977, 2913, 2217, 1462, 1372, 868, 702 cm-1
HRMS (EI) calcd for C29H28O 392.2140, found 392.2134.
;
Gen er a l P r oced u r e for Diels-Ald er Rea ction s be-
tw een Su bstitu ted An th r a cen es 12a -e a n d Ben zyn es 5a
a n d 5b (Ta ble 1). A three-neck 250 mL round-bottom flask
equipped with a condenser and two addition funnels was
charged with (ca. 0.1 g) of the anthracene and 25 mL of
benzene and the resulting solution brought to reflux. One
addition funnel was loaded with 5 equiv of the anthranilic acid
in 60 mL of DME and the other with 5 equiv of iso-amyl nitrite
dissolved in 60 mL of benzene. The solutions of anthranilic
and iso-amyl nitrite were added simultaneously and dropwise.
After addition was completed, the crude product was concen-
trated under vacuum and passed through a plug of silica gel
using a 25:75 v/v mixture of hexanes and CH2Cl2. The resulting
mixture was analyzed by 1H NMR to determine the ratio of
addition products resulting from 9,10- and 1,4-addition.
9-(3-Hyd r oxy-3-m eth yl-1-bu tyn yl)-2,3,6,7,10,12,13-h ep -
ta m eth yltr ip tycen e (3b). The general procedure for the
preparation and in situ reaction of benzyne described above
was carried out with anthracene 4b (0.49 g, 1.48 mmol), 4,5-
dimethylanthranilic acid 6b (1.23 g, 7.42 mmol, 5 equiv) and
isoamyl nitrite (0.87 g, 1.00 mL, 7.42 mmol, 5 equiv). The crude
product was chromatographed on silica gel using a mixture of
diethy1 ether and hexanes in a 20:80 v/v ratio to yield 0.46 g
of 3b (72% yield) as a colorless solid: mp 340-343 °C; 1H NMR
(CDCl3) δ 7.41 (s, 3H), 7.08 (s, 3H), 2.35 (s, 3H), 2.18 (s, 9H),
2.17 (s, 9H), 1.94 (s, 6H); 13C NMR (CDCl3) δ 144.3, 143.2,
133.2, 132.2, 132.6 123.4, 122.0, 97.4, 77.8, 65.9, 51.1, 47.0,
32.2, 19.6, 13.3; IR (KBr) 3441, 2971, 2922, 1469, 1454, 1384,
1293, 1259, 1164, 1019, 885, 856, 632 cm-1; HRMS (EI) calcd
for C32H34O 434.2610, found 434.2613.
9-Eth yn yl-2,3,6,7,10,12,13-h eptam eth yltr iptycen e (3bH).
Triptycene 3b (0.15 g, 0.35 mmol) was dissolved in 5 mL of
toluene at room temperature. To this solution were added K2-
CO3 (0.048 g, 0.35 mmol) and 18-crown-6 (0.069 g, 0.26 mmol).
The mixture was brought to reflux while stirring under argon.
After 24 h at this temperature, the reaction was cooled to room
temperature and diluted with Et2O (20 mL) and H2O (10 mL).
The aqueous layer was extracted with ether (3 × 10 mL). The
ether layers were combined, washed with brine (20 mL), and
dried over anhydrous MgSO4. The solvent was removed under
reduced pressure. The residue was chromatographed on silica
gel (100% hexanes) to give 0.1236 g of 3bH in 95% yield as a
colorless solid: mp 76-77 °C; 1H NMR (CDCl3) δ 7.50 (s,3H),
7.09 (s, 3H), 3.29 (s, 1H), 2.36 (s, 3H), 2.19 (s, 9H), 2.18 (s,-
9H); 13C NMR (CDCl3) δ 144.2, 142.9, 133.0, 132.6, 123.1,122.0,
80.0, 79.5, 51.3, 47.1, 19.6, 19.4, 13.3; IR (KBr) 3308, 3016,
2970, 2939, 2921, 2864, 2126, 1460, 1404, 1384, 1299, 1263,
1241, 1019, 993, 902, 886, 857, 657, 631 cm-1; HRMS (EI) calcd
for C29H28 379.2191, found 376.2192.
1
mp 221-223 °C; H NMR (CDCl3) δ 8.17 (s, 2 H), 8.14 (s, 1
H), 7.68 (s, 2 H), 2.50 (s, 6 H), 2.45 (s, 6 H), 1.90 (s, 6 H); 13C
NMR (CDCl3) δ 136.53, 135.19, 131.61, 130.08, 127.41, 125.29,
125.16, 113.42, 104.15, 79.44, 66.29, 31.90, 20.81, 20.23; IR
(KBr) 3350, 2976, 2914, 2202, 1458, 1458,1342, 1231, 1138,
953, 891 cm-1; HRMS (EI) calcd for C23H24O 316.1827, found
316.1930.
10-(3-Hyd r oxy-3-m eth yl-1-bu tyn yl)-2,3,6,7,9-p en ta m e-
th yla n th r a cen e (4b). The procedure used for the preparation
of 4a was applied to 0.55 g of bromoanthracene 11b (1.69
mmol), 0.85 g of 2-methyl-3-butyn-2-ol (10.1 mmol), and 0.36
g of PdCl2(Ph3)2 (0.51 mmol, 30 mol %) to give 0.55 g of 4b
(96% yield). The product was obtained as a pale yellow solid:
1
mp 158-159 °C; H NMR (CDCl3) δ 8.23 (s, 1 H), 7.97 (s, 2
H), 3.02 (s, 3 H), 2.50 (s, 6 H), 2.49 (s, 6 H), 1.87 (s, 6 H); 13C
NMR (CDCl3) δ 135.7, 135.0, 131.3, 129.3, 128.5, 126.0, 123.9,
112.1, 103.8, 79.8, 66.2, 31.8, 20.7, 20.4, 14.1; IR (KBr) 3345,
2979, 2913, 2360, 2350, 2203, 1461, 1372, 1224, 1213, 1164,
11.38, 1028, 991, 950, 876, 851 cm-1; HRMS (EI) calcd for
C
24H26O 330.1984, found 330.1984.
9-P r op yl-10-(3-h yd r oxy-3-m eth yl-1-bu tyn yl)-2,3,6,7-tet-
r a m et h yla n t h r a cen e (4c). The procedure used for the
preparation of 4a was applied to 0.91 g of 11c (2.56 mmol),
0.71 g of 2-methyl-3-butyn-2-ol (8.44 mmol), and 0.20 g of
PdCl2(PPh3)2 (0.28 mmol) to give 0.69 g of 4c as a pale orange
solid (75% yield): mp 225-226 °C dec; 1H NMR (CDCl3) δ 8.23
(s, 2H), 7.95 (s, 2H), 3.50 (t, J ) 7.7 Hz, 2H), 2.50 (s, 12H),
2.28 (s, 1H), 1.85 (s, 6H), 1.81 (sext, J ) 7.7 Hz), 1.14 (t, J )
7.7 Hz, 3H); 13C NMR (CDCl3) δ 135.8, 135.0, 134.6, 131.5,
128.1, 126.3, 123.9, 112.4, 104.0, 79.9, 66.3, 31.9, 30.1, 24.5,
20.8, 20.5, 14.7; IR (KBr) 3347, 3050, 2963, 2942, 2202, 1461,
1367, 1006, 876 cm-1; HRMS (EI) calcd for C26H30O 358.2297,
found 358.2307.
9-Hexyl-10-(3-h yd r oxy-3-m eth yl-1-bu tyn yl)-2,3,6,7-tet-
r a m eth yla n th r a cen e (4d ). A 25 mL pear-shaped round-
bottom flask was charged with 9-bromo-10-hexyl-2,3,6,7-
tetramethylanthracene 11d (0.11 g, 0.27 mmol), (PPh3)2PdCl2
(0.035 g, 0.050 mmol), 3.5 mL of degassed piperidine, and
2-methyl-3-butyn-2-ol (0.087 g, 1.03 mmol). The mixture was
flushed with argon for 5 min, transferred to an oil bath at 90
°C, and heated for 22 h. The crude reaction mixture was
diluted in 50 mL of Et2O, washed with H2O (3 × 15 mL) and
brine (2 × 10 mL), dried over anhydrous NaSO4, and concen-
trated. The reaction product was purified via flash column
chromatography (40:60 CH2Cl2/hexanes) to afford 4d as a pale
1
yellow solid (0.064 g, 59% yield): mp 172-173 °C; H NMR
(CDCl3) δ 8.22 (s, 2H), 7.92 (s, 2H), 3.49 (t, J ) 7.8 Hz, 2H),
2.48 (s, 12H), 2.43 (s, 1H), 1.85 (s, 6H), 1.75 (quintet, J ) 7.8
Hz, 2H), 1.57 (quintet, J ) 7.8 Hz, 2H), 1.39 (m,4H), 0.92 (t,
1,4-Bis{2-[9-(2,3,6,7,10,12,13-h ep t a m et h ylt r ip t ycyl)]-
eth yn yl}ben zen e (2b). Triptycene 3bH (0.001 g, 0.03 mmol)
J . Org. Chem, Vol. 69, No. 5, 2004 1661

Godinez et al.
was dissolved in 2.0 mL of degassed piperidine. While the
solution of 3bH was stirred, a solution of 1,4-diiodobenzene
(0.0044 g, 0.013 mmol) and Pd(PPh3)2Cl2 (0.0056 g, 0.011
mmol, 40 mol %) in 1 mL of hot degassed piperidine was added
slowly. The reaction was heated at 80 °C for 12 h. Upon
completion, the solvent was removed under reduced pressure.
The crude mixture was dissolved in 20 mL of benzene and
washed three times with 3 mL of saturated ammonium
chloride and twice with 3 mL of deionized water. The benzene
layers were combined and the aqueous layers extracted with
5 mL of benzene. The benzene layer was dried with anhydrous
MgSO4. The residue was chromatographed in silica gel using
hexanes as the eluant to give 0.010 g of 2b mixed with 1,4-
[9-(2,3,6,7,10,12,13-heptamethyltriptycyl)]-1,3-butadyine. At-
tempts to separate 2b from the 1,3-butadyine were unsuccess-
ful, and only small amounts of pure sample were obtained for
partial analysis: 1H NMR (CDCl3) δ 7.97 (s, 4H), 7.56 (s, 6H),
7.11 (s, 6H), 2.38 (s, 6H), 2.20 (s, 18H), 2.19 (s, 18H); IR (KBr)
3014, 2923, 2854, 1602, 1458, 1404, 1376, 1300, 1261, 1237,
1179, 1134, 1115, 1072, 1019, 992, 898, 883, 854, 833, 805,
744, 697, 629, 616, 556, 541, 490, 465 cm-1; HRMS (EI) calcd
for C64H58 826.4538, found 826.4484.
9-P r op yl-10-(2-m eth yl-3-bu tyn e-2-ol)-2,3,6,7,12,13-h ex-
a m eth yltr ip tycen e (3c). The general procedure for the
preparation and in situ reaction of benzyne described above
was carried out with anthracene 4c (0.30 g, 0.84 mmol), 4,5-
dimethylanthranillic acid 6b (1.18 g, 7.14 mmol), and isoamyl
nitrite (0.93 g, 7.94 mmol) to afford 0.058 g of 3c as a white
solid (15% isolated yield): mp 283.9-286.4 °C; 1H NMR
(CDCl3) δ 1.38 (t, J ) 7.7 Hz, 3H) 1.90 (s, 6H), 2.14 (s, 18H),
2.17 (m, 2H), 2.83 (m, 2H), 7.09 (s, 3H, Ar), 7.38 (s, 3H, Ar);
13C NMR (CDCl3) δ 143.7, 143.7, 132.6, 132.2, 123.3, 123.2,
97.5, 77.9, 65.8, 51.5, 51.3, 32.1, 30.4, 19.7, 19.4, 18.5, 15.9;
IR (KBr) 3321, 3011, 2959, 2863, 2243, 1465, 1159, 1141, 949,
864 cm-1; HRMS (EI) calcd for C34H38O 462.2923, found
462.2926.
preparation and in situ reaction of benzyne described above
was carried out with anthracene 4e (1.03 g, 2.32 mmol),
anthranilic acid 6a (3.27 g, 23.8 mmol), and iso-amyl nitrite
(2.97 g, 25.4 mmol). The crude product was concentrated under
vacuum and passed through a plug of silica gel using a 25:75
v/v mixture of hexanes/CH2Cl2. The pretreated crude mixture
was further chromatographed, 60:40 hexanes/CH2Cl2, to afford
0.104 g (8% isolated yield) of 15e as a white solid: mp 305-
307 °C; 1H NMR (CDCl3) δ 8.11 (dd, J ) 0.97, 8.3 Hz, 2H),
7.72 (dd, J ) 1.1, 7.4 Hz, 1H), 7.65 (t, J ) 8.3 Hz), 7.54 (m,
1H), 7.48 (s, 2H), 7.07(s, 2H), 7.05 (dd, J ) 1.1, 7.6 Hz, 1H),
7.02 (td, J ) 1.1, 7.4 Hz, 1H), 6.92 (td, J ) 1.1, 7.6 Hz, 1H),
2.17 (s, 6H), 2.09 (s, 6H), 1.92 (s, 6H); 13C NMR (CDCl3) δ
146.63, 145.43, 143.51, 143.41, 136.33, 132.65, 132.62, 131.50,
128.28, 127.05, 125.53, 124.81, 124.80, 123.91, 123.49, 121.74,
98.12, 77.56, 65.82, 58.30, 52.14, 32.06, 19.67, 19.40; IR (KBr)
3576, 3062, 2980, 2917, 2241, 1456, 1169, 954, 743, 712, 632
cm-1; HRMS (EI) calcd for C35H32 468.2453, found 468.2457.
9-(E t h yn yl)-2,3,6,7-t et r a m et h yl-10-p h en ylt r ip t ycen e
(15eH). A three-neck 25 mL round-bottom flask was charged
with triptycene 15c (0.054 g, 0.14 mmol), (Bu)4NI (0.15 g, 0.41
mmol), and KOH (0.0901 g, 1.61 mmol) followed by 5 mL of
benzene. The mixture was transferred to an oil bath and
heated at 68 °C for 7 h. The crude product was diluted in 20
mL of benzene, washed with dilute HCl (3 × 10 mL) and brine
(3 × 10 mL), dried over anhydrous MgSO4, and concentrated
under vacuum to afford 0.068 g of 15eH (83% yield) as a white
1
solid: mp >200 °C dec; H NMR (CDCl3) δ,8.34 (s, 2H), 7.54
(m, 3H), 7.36 (m, 2H), 7.32 (s, 2H), 3.98 (s, 1H), 2.48 (s, 6H),
2.30 (s, 6H); 13C NMR (CDCl3) δ 138.94, 136.52, 136.49, 135.85,
131.85, 131.08, 128.64, 128.30, 127.38, 126.00, 125.49, 113.16,
87.46, 81.21, 20.44, 20.43; IR (KBr) 3282, 3006, 2910, 2100,
1447, 1004, 889, 651, 604 cm-1; HRMS (EI) calcd for C26H22
334.1722, found 334.1720.
1,4-Bis{2-[9-(2,3,6,7-tetr a m eth yl-10-p h en yltr ip tycyl)]-
eth yn yl}ben zen e [(12H,13H)-2e]. A three-neck 25 mL round-
bottom flask was charged ethynyltriptycene 14a (0.083 g, 0.20
mmol), 1,4-diiodobenzene (0.029 g, 0.088 mmol), (PPh3)2PdCl2
(0.014 g, 0.020 mmol), and 7 mL of argon-flushed piperidine.
The mixture was transferred to an oil-bath and heated to 90
°C for 48 h. The crude mixture was diluted in 100 mL benzene,
washed with dilute HCl, dried over anhydrous MgSO4, and
concentrated under vacuum. The crude product was chromato-
graphed, 90:10 hexanes/CH2Cl2, to afford 0.025 g of 2eH as a
9-P r opyl-2,3,6,7,12,13-h exam eth yl-10-eth yn yltr iptycen e-
(3cH). A three-neck 25 mL round-bottom flask was charged
with 5.0 mL of benzene followed by trypticene 3c (0.17 g, 0.36
mmol), (Bu)4NI (0.35 g, 0.95 mmol), and KOH (0.40 g, 7.13
mmol). The mixture was heated to 80 °C for 24 h. The crude
mixture was diluted in 50 mL of ether, washed with H2O (3 ×
20 mL) and brine (2 × 20 mL), dried over anhydrous MgSO4,
and concentrated under vacuum. The crude product was
purified via flash column chromatography (100% hexanes) to
afford 3cH as a white solid 0.098 g (67% yield): mp 297-299
1
1
white solid (32% yield): mp >400 °C dec; H NMR (CDCl3) δ
°C; H NMR (CDCl3) δ 7.47 (s, 3H), 7.10 (s, 3H), 3.26 (s, 1H),
2.83 (m, 2H), 2.15 (m, 20H), 1.30 (t, J ) 7.4 Hz, 3H); 13C NMR
(CDCl3) δ 143.4, 132.4, 132.0, 123.4, 123.2, 80.2, 79.6, 51.61,
51.58, 30.4, 19.8, 19.4, 18.6, 16.0; IR (KBr) 3298, 3018, 2959,
2243, 1465, 864, 731 647 cm-1; HRMS (EI) calcd for C31H32
404.2504; found 404.2502.
8.16 (d, J ) 7.7 Hz, 4H), 7.99 (s, 4H), 7.91 (dd, J ) 1.0, 7.4
Hz, 2H), 7.68 (t, J ) 7.7 Hz), 7.66 (s, 4H), 7.56 (t, J ) 7.7 Hz,
2H), 7.13 (s, 4H), 7.11 (d, J ) 7.9 Hz, 2H), 7.08 (td, J ) 1.0,
7.4 Hz, 2H), 6.97 (td, J ) 1.2, 7.9 Hz, 2H), 2.22 (s, 12H), 2.12
(s, 12H); 13C NMR (CDCl3) δ 146.78, 143.66, 143.62, 136.45,
132.93, 132.84, 132.31, 131.63, 128.42, 127.20, 125.75, 125.02,
125.01, 124.12, 123.74, 123.50, 122.02, 92.71, 87.01, 58.52,
53.19, 19.81, 19.51; IR (KBr) 3015, 2922, 2853, 2234, 1456,
787, 738, 641, 544 cm-1; HRMS (EI) calcd for C70H54 894.4226,
found 894.4263.
1,4-Bis{2-[9-(10-p r op yl-2,3,6,7,12,13-h exa m eth yltr ip ty-
cyl)]-eth yn yl}ben zen e (2c). A 25 mL three-neck round-
bottom flask was charged with 4-[9-(2,3,6,7-tetramethyl-10-
propyl)triptycyl]ethyne 3cH (0.07 g, 0.17 mmol), 1,4-
diiodobenzene (0.027 g, 0.082 mmol), (PPh3)2PdCl2 (0.024 g,
0.034 mmol, 9 mol %), and 5.0 mL of degassed piperidine. The
reaction mixture was kept under an argon atmosphere and
heated to 85 °C for 2 days. The crude product was suspended
in 100 mL of CH2Cl2 and filtered. The filtrate was washed with
hexanes. The filtrate was purified via flash column chroma-
tography 20:80 CH2Cl2/hexanes (v/v) to give 0.035 g (47%) of
2c as a white solid: mp >460 °C (dec); 1H NMR (CDCl3) δ
7.96 (s, 4H), 7.56 (s, 6H), 7.14 (s, 6H), 2.88 (m, 4H), 2.21 (m,
4H), 2.19 (s, 18H), 2.18(s, 18H), 1.41 (t, J ) 7.3 Hz, 6H); 13C
NMR (CDCl3) δ 143.9, 133.0, 132.1, 132.4, 132.3, 123.6, 123.4,
92.1, 87.3, 52.3, 51.7, 30.5, 19.8, 19.6, 18.6, 16.0; IR (KBr) 3011,
2959, 2915, 1465, 860, 835, 628 cm-1; HRMS(EI) calcd for
Ack n ow led gm en t. This work was supported by
NSF Grants DMR9988439 and DMR0307028. Instru-
mentation support for X-ray (CHE9871332) and Solid
State NMR (DMR9975975) by the NSF is also acknowl-
edged. We thank Prof. Emily Maverick for help with
ongoing analysis of crystallographic atomic displace-
ment parameters.
Su p p or tin g In for m a tion Ava ila ble: Spectral data for all
new compounds and CIF files for rotors 2c and 2eH. This
material is available free of charge via the Internet at
http://pubs.acs.org.
C
68H66 882. 882.5165; found 882.5177.
9-(3-Hyd r oxy-3-m eth yl-1-bu tyn yl)-2,3,6,7-tetr a m eth yl-
10-p h en yltr ip tycen e (15e). The general procedure for the
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1662 J . Org. Chem., Vol. 69, No. 5, 2004