As shown in Scheme 1 (method B, 50 °C was chosen as
an optimized reaction temperature for this study), the one-
pot synthesis involves two stages from the starting material
2,3,6,7-tetrabromonaphthalene dianhydride (2):9 first the
reaction of 2 with 3 equiv of Na2(i-mnt)10 (i-mnt = 1,1-
dicyanoethene-2,2-dithiolate) was performed in DMF at
50 °C for 1 h, and then one (R1NH2 and R2NH2, R1 = R2,
3 equiv vs 2) or two types of amines (R1NH2 and R2NH2,
R1 ¼ R2, 1.5:1.5 equiv vs 2) were added to the above
solution and further stirred for 6 h at 50 °C, affording the
target NDI-DTYM2 derivatives.
Scheme 2. Proposed Reaction Process of the One-Pot Synthesis
Compounds 1aꢀi (Table 1) not only highlight the
efficiency and excellent functional group tolerance of the
one-pot synthesis (method B) but also provide promising
n-type organic materials. Compound 1a has been reported
previously,4a and its optimum OTFT devices exhibited
electron mobilities as high as 0.55ꢀ1.2 cm2 Vꢀ1 sꢀ1 in
ambient.5 NDI-DTYM2 derivatives 1bꢀi are newly devel-
oped compounds. As shown in Table 1 (entries 1 and 2),
both methods A and B are applicable to the synthesis of
symmetrically N-substituted compounds 1a and 1b that
bear the N-alkyl chains and N-benzyl groups, respectively,
but the yield achieved by method B is much higher than
that obtained by method A (28% vs 18%4a for 1a, and
29% vs 11% for 1b). Compound 1c, bearing two N-(2-
aminoethyl)-3,4,5-tris (dodecyloxy)benzamide moieties,
could not be obtained by method A due to the complex
reactions involved (entry 3). The implementation of meth-
od A for the synthesis of 1d (a symmetrically N-substituted
compound with 4-ter-butylphenyl N-groups) is also un-
successful, giving only a trace amount of product (entry 4).
Compounds 1e and 1f could not be prepared by method A
due to their acid-sensitive N-substituents (entries 5 and 6).
Similar to 1f, when trying to synthesize other unsymme-
trically N-substituted compounds by method A, the results
were so disappointing that we obtained only a trace of the
target compounds (Table 1, entries 7ꢀ9, 1gꢀi). Fortu-
nately, the one-pot synthetic method B is very efficient for
the synthesis of both symmetrically N-substituted NDI-
DTYM2 derivatives (Table 1, entries 1ꢀ5, 1aꢀe, R1 = R2)
and unsymmetrically N-substituted ones (Table 1, entries
6ꢀ9, 1fꢀi, R1 ¼ R2) with moderate yields of 28ꢀ55% and
13-21%, respectively.
in DMF affords the core-expanded naphthalene dianhy-
dride (Scheme 2, 6),12 and then an imidization reaction of 6
and amine (R1NH2 and R2NH2) gives the target NDI-
DTYM2 derivatives (1). This mild imidization reaction
that can operate at low temperature (rt to 50 °C) is fairly
scarce for the synthesis of rylene and related diimides.13
Compounds 1aꢀi obtained by the one-pot synthesis
1
were characterized by mass spectroscopy, H/13C NMR
spectra, elemental analysis, andIRspectra. All compounds
except 1d are well soluble in common organic solvents.
Thermogravimetric analysis (TGA), UVꢀvis absorption
spectra, and cyclic voltammetry (CV) were carried out to
evaluate the thermal, optical, and electrochemical proper-
ties of the new compounds 1bꢀi (see Table S1 and Figures
S2ꢀ5 for details). 1d exhibits the highest onset decomposi-
tion temperature (Td) of 476 °C, and 1i shows the second-
ary Td value of 399 °C, which are both higher than those of
symmetrically N-substituted NDI-DTYM2 derivatives
that bear swallow-tail N-alkyl chains (370ꢀ389 °C).4 The
results demonstrate that the thermal stability of NDI-
DTYM2 derivatives largely depends on the feature of the
N-substituent withthe orderofbis(N-phenyl) > N-phenyl,
N0-alkyl > bis(N-alkyl). Compounds 1bꢀi showed similar
absorption spectra and cyclic voltammograms with com-
parable peak values for their end absorptions and redox
curves (Figures S3ꢀ5). This is due to the electronic decou-
pling of the NDI-DTYM2 core and the N-substituent.6
Compounds 1bꢀi have comparable low-lying LUMO
levels of ꢀ4.29 to ꢀ4.36 eV calculated from the CV results
using ferrocene (ꢀ4.8 eV to vacuum) as an internal stan-
dard (see Table S1 for details), and this is crucial for
realizing electron carrier injection and conduction with
ambient stability.14
Encouraged by these results, we started to study the
reaction process of the one-pot synthesis. As shown in
Scheme 2, the one-pot operation is successful when we first
carried out the reaction of 2 and Na2(i-mnt) in DMF, but it
failed when the reaction of 2 with amine (R1NH2 and
R2NH2) in DMF was first performed.11 A proposed me-
chanism for this one-pot synthesis is that the nucleophilic
aromatic substitution (SNAr) reaction of 2 with Na2(i-mnt)
(12) Only bilateral core-expanded naphthalene dianhydride 6 was
detected by mass spectrometry (Figure S1) during the SNAr reaction; the
unilateral core-expanded compound 5 was not detected probably due to
its much higher reactivity with Na2(i-mnt) than 2.
(13) (a) Zheng, Q.; Huang, J.; Sarjeant, A.; Katz, H. E. J. Am. Chem.
Soc. 2008, 130, 14410. (b) Tambara, K.; Ponnuswamy, N.; Hennrich, G.;
Pantos, G. D. J. Org. Chem. 2011, 76, 3338. (c) Yuan, Z.; Li, J.; Xiao, Y.;
Li, Z.; Qian, X. J. Org. Chem. 2010, 75, 3007.
(9) (a) Gao, X.; Qiu, W.; Yang, X.; Liu, Y.; Wang, Y.; Zhang, H.; Qi,
T.; Liu, Y.; Lu, K.; Du, C.; Shuai, Z.; Yu, G.; Zhu, D. Org. Lett. 2007, 9,
€
€
3917. (b) Roger, C.; Wurthner, F. J. Org. Chem. 2007, 72, 8070.
(10) Hatchard, W. R. J. Org. Chem. 1964, 29, 660.
(11) The reaction of 2 and amine (R1NH2 and R2NH2) in DMF gene-
rates 2,3,6,7-tetrabromo-4,8-N(R1),N0(R2)carbamoyl-naphthalene-1,5-
diacarboxylic acid (Scheme 2, 4; see ref 9a for details), which is difficult
to further react with Na2(i-mnt) in DMF even at a much elevated
temperature due to its weak reactivity.
(14) (a) Jones, B. A.; Facchetti, A.; Wasielewski, M. R.; Marks, T. J.
J. Am. Chem. Soc. 2007, 129, 15259. (b) Usta, H.; Facchetti, A.; Marks,
T. J. Acc. Chem. Res. 2011, 44, 501.
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Org. Lett., Vol. 14, No. 1, 2012