peripheral substituents. However, there has been no report
on HATN and HAT derivatives possessing simultaneously
both donor-acceptor substituents, probably because of the
lack of practical synthetic methods. Here, in this paper we
report an expedient synthesis and mesomorphic behavior of
the donor-acceptor 3,7,11-trialkoxy-2,6,10-tricyano-1,4,5,8,9,-
12-hexaazatriphenylene (HATCNORn). Further, single-
crystal X-ray structural determinations have been possible
for the 3,7,11-trimethoxy-2,6,10-tricyano-1,4,5,8,9,12-hexaaza-
triphenylene (HATCNOR1); this shows HAT-HAT π-com-
plexation in the solid state.
Scheme 2. Synthesis of HATCNOR1,6
It has been reported that 5,6-disubstituted pyrazine-2,3-
carbonitrile undergo selective substitution of only one nitrile
group with alcohols, giving 5,6-disubstituted 3-alkoxypyra-
zine-2-carbonitrile. We thus anticipated that the difunction-
alized donor-acceptor (HATCNORn) might be similarly
synthesized from the regioselective substitution of the readily
available 1,4,5,8,9,12-hexaazatriphenylene hexacarbonitrile,
HATCN, with alcohols (Scheme 1).10
analysis and 13C NMR spectrum confirmed the substitution
of three methoxy groups in HATCNOR1.
The single methoxy peak in the 1H NMR spectrum
corresponded to this symmetrical structure. The high regio-
selectivity of the substitution reaction could be attributed to
the electron-donating nature of the methoxy group that
deactivates the adjacent positions toward further nucleo-
philic addition; hence the nitrile groups at the 3,7,11-positions
in HATCN were the most readily substituted (Scheme 3).
Reaction of HATCN with n-hexanol under similar condi-
tions gave 3,7,11-trihexyloxy-2,6,10-tricyano-1,4,5,8,9,12-
hexaazatriphenylene (HATCNOR6). We thus have devel-
oped a clean and practical protocol for the synthesis of
HATCNORn.
Scheme 1
HATCNOR1 yielded yellow triclinic crystals from aceto-
nitrile. Interestingly, the X-ray structure of HATCNOR1
revealed rigorous stacking and HAT-HAT π-complexation
in the solid state. This stands in contrast to the electron-
deficient HAT derivatives, which like most of the hitherto
known electron-deficient aromatic heterocycles13-17 are
predisposed to avoid self-π-overlap in the solid state. Also,
π-complexation in the solid state has been previously
achieved via the interplanar hydrogen bond for HAT-
hexaamide.18 The introduction of three methoxy groups in
HATCNOR1 has dramatic consequences upon the stability
of the resulting π-complexation of these compounds in the
solid state. We believe that the presence of methoxy groups
in the electron-deficient HAT nucleus has over-ridden the
avoidance of π-complexation. The molecules are packed in
a staggered ABAB layer arrangement with one of the
molecular centers offset from the stacking axis. The mean
The starting material, HATCN, was originally reported
as a black solid,11 and more recently as a yellow orange solid
after rigorous purification.12 We first studied the reaction of
the yellowish-orange HATCN12 with methanol in refluxing
acetonitrile. The reaction proceeds to give a complex mixture
of products that was found difficult to purify. At this point
we felt that most of the unwanted compounds from the
reaction were obtained from the impurities present in the
previously reported yellowish-orange HATCN. Therefore,
we have attempted to undertake further purification of
HATCN. Our approach involved dissolving the yellowish-
orange HATCN12 in acetonitrile, followed by dropwise
addition into water to give a pale-yellowish suspension.
HATCN as a stable pale-yellowish solid was obtained after
centrifuging the suspension. The purified HATCN was
reacted with methanol in refluxing acetonitrile, and this gave
easily separable HATCNOR1 in 40% yield (Scheme 2). It
was found advantageous to use the freshly purified HATCN
whereby the reaction proceeded more cleanly. Elemental
(13) Phillips, D. C.; Ahmed, F. R.; Barnes, W. H. Acta Crystallogr. 1960,
13, 365.
(14) Clearfield, A.; Sims, M. J.; Singh, P. Acta Crystallogr., Sect. B 1972,
28, 350.
(15) Huiszoon, C.; van der Waal, W. B.; van Egmond, A. B.; Harkema,
S. Acta Crystallogr., Sect. B 1972, 28, 3415.
(10) Kojima, T.; Nagasaki, F.; Ohtsuka, Y. J. Heterocycl. Chem. 1980,
17, 455.
(16) Nishigaki, S.; Yoshioka, H.; Nakatsu, K. Acta Crystallogr., Sect. B
1978, 34, 875.
(11) Kanakarajan, K.; Czarnik, A. W. J. Org. Chem. 1986, 51, 5241.
(12) Rademacher, J. T.; Kanakarajan, K.; Czarnik, A. W. Synthesis 1994,
378.
(17) Huiszoon, C. Acta Crystallogr., Sect. B 1976, 32, 998.
(18) Beeson, J. C.; Fitzgerald, L. J.; Gallucci, J. C.; Gerkin, R. E.;
Rademacher, J. T.; Czarnik, A. W. J. Am. Chem. Soc. 1994, 116, 4621.
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Org. Lett., Vol. 7, No. 19, 2005