Organometallic C-N coupling between N,N′-dichloro-p-benzoquinone diimine and Grignard reagents and its application to synthesis of polyanilines

Article abstract of DOI:10.1016/S0040-4039(01)01872-X

A new C-N coupling reaction between N,N′-dichloro-p-benzoquinone diimines and aryl Grignard reagents has been developed. The new method gives N,N′-diaryl-p-benzoquinone diimines in 50-88% isolated yield. The obtained new compounds are regarded as oligomeric model compounds for pernigraniline-type polyaniline, and their chemical behavior has been investigated. New polyaniline-type polymers have been prepared by applying the developed C-N coupling reaction.

Full text of DOI:10.1016/S0040-4039(01)01872-X

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 42 (2001) 8653–8656
Organometallic CꢀN coupling between
N,N%-dichloro-p-benzoquinone diimine and Grignard reagents and
its application to synthesis of polyanilines
Takakazu Yamamoto,* Ismayil Nurulla† and Asako Ushiro
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
Received 9 August 2001; revised 13 September 2001; accepted 5 October 2001
Abstract—A new C–N coupling reaction between N,N%-dichloro-p-benzoquinone diimines and aryl Grignard reagents has been
developed. The new method gives N,N%-diaryl-p-benzoquinone diimines in 50–88% isolated yield. The obtained new compounds
are regarded as oligomeric model compounds for pernigraniline-type polyaniline, and their chemical behavior has been
investigated. New polyaniline-type polymers have been prepared by applying the developed C–N coupling reaction. © 2001
Elsevier Science Ltd. All rights reserved.
Organometallic coupling reaction between C–X (X=
halogen) and C–M (M=MgX, Li, SnR3, SiR3, etc.)
compounds has long been studied,1–3 and the effects of
transition metal complex catalysts for the coupling
reaction have been demonstrated. However, in contrast
to extensive studies on the C–C coupling reaction, only
limited attention has been paid to similar C–N coupling
reactions between N–X and C–M compounds. In the
course of our studies on electrically conducting
polyanilines2 and the organometallic synthesis of p-con-
jugated polymers,3 we considered the possibility of
obtaining polyanilines, PANs, by organometallic cou-
pling between N,N%-dichloro-p-benzoquinone diimines
and aromatic diGrignard reagents, and reported that
this type of polycondensation actually gave polyanili-
nes.4 However, basic studies on the organometallic
C–N coupling have not been reported. Herein we
report the results of basic studies on the C–N coupling
reaction and the chemical properties of the obtained
organic compounds (Scheme 1).
N,N%-Dichloro-p-benzoquinone diimine with methyl
substituents was prepared according to the following
1
oxidation reaction and characterized by H NMR spec-
troscopy and elemental analysis;5 preparation of N,N%-
dichloro-p-benzoquinone
without
the
methyl
substituents in an analogous manner was previously
reported.6
By using the methyl-substituted (1b) and non-substi-
tuted (1a) N,N%-dichloro-p-benzoquinone diimines, we
carried out the C–N coupling reactions, which are
outlined in Scheme 2.
For example, the C–N coupling reaction of the Grig-
nard reagent of o-bromotoluene with 1b was carried
Scheme 1.
Keywords: N,N%-dichloro-p-benzoquinone diimine; C–N coupling; polymers; nickel complex.
* Corresponding author. Tel.: +81-45-924-5220; fax: +81-45-924-5276; e-mail: tyamamot@res.titech.ac.jp
† Visiting researcher from the Department of Chemistry, Xin Jiang University, PR China.
0040-4039/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(01)01872-X

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T. Yamamoto et al. / Tetrahedron Letters 42 (2001) 8653–8656
Table 1. UV–vis data of the C–N coupling products
Compounds
umax (nm)
In CF3COOH
In DMF
2
3
4
5
484
615
601
724
750
302, 452
310, 457
319, 492
perniglaniline-type aniline oligomers.8b,9 In CF3COOH
the absorption peak shifted to a longer wavelength in
accord with protonation data previously reported for the
pernigraniline-type oligomers.8b,9 Treatment of 2–5 with
an aqueous solution of hydrazine under a nitrogen
atmosphere afforded white solids of the corresponding
reduced products, similar to the cases of the chemical
reduction of aniline oligomers and polymers with oxi-
dized structures.2a,8 Quantitative yield was observed for
the reduction of 3. The 1H NMR spectrum of the reduced
Scheme 2. Reagents and conditions: (a) THF under reflux,
NiCl2(dppp).
1
product showed an N–H peak at about l 5; H NMR
data of the reduction products of 3 (CDCl3, 400 MHz):
l 6.8–7.2 (m, 10H), 5.05 (br, 2H, NH), 2.26 (s, 6H), 2.22
(s, 6H). The p–p* absorption band of 2–5 in the range
of 484–492 nm (cf. Table 1) disappeared in the reaction
with hydrazine, and the rate of the reaction obeyed the
first-order rate law with respect to the concentration of
the pernigraniline-type starting compound. The IR spec-
tra of the reduced product showed a sharp w(N–H) peak
at about 3500 cm−1. Electrochemical reduction behavior
of an analogous quinodiimine-type compound (N,N%-
diphenyl-p-phenylenediimine) in aqueous media has been
reported.10
out as follows. To a solution of o-bromotoluene (1.63
g, 10.0 mmol) in 10 mL of dry THF was added magnesium
(0.27 g, 11 mmol). After stirring the reaction mixture
under reflux for 2 h to form the Grignard reagent,
dichloro[bis(1,3 - diphenylphosphino)propane]nickel(II),
NiCl2(dppp) (30 mg, 0.05 mmol) and a solution of 1b (0.81
g, 4.0 mmol) in 10 mL of THF were added. After the
reaction mixture was refluxed for 4 h under N2, the solvent
was removed by evaporation. The obtained residue was
washed with diluted hydrochloric acid (about 1 M) and
water. The product was purified by column chromatog-
raphy on SiO2 using CHCl3 as an eluent. After drying
under vacuum, a red powder of analytically pure 3 was
obtained; yield=0.76 g (60%). Other C–N coupling
products 2, 4 and 5 were prepared analogously in isolated
yields of 88, 50 and 52%, respectively. The basicity of the
coupling products seemed not high; however, the prod-
ucts were partly protonated with diluted hydrochloric
acid and were lost during the washing with diluted
hydrochloric acid, and the crude yield of the product
seemed higher. Actually, neutralization of the washed
solution of 3 with NH4OH and extraction with hexane
indicated that 40% yield of 3 was included in the extract,
as proved by 1H NMR spectroscopy; therefore, the C–N
coupling is considered to give the product in high crude
yield. All the compounds were characterized by IR and
1H NMR spectroscopy and elemental analysis.5 The C–N
coupling reaction proceeded even without the Ni catalyst;
however, in this case the yield was lower (e.g. 40% for
3).7 Similar pernigraniline-type oligomers of aniline have
been prepared via different reaction routes.8 However, the
present method can provide a wider variety of pernigrani-
line-type aniline dimers with various combinations of
reactants, and is applicable to the preparation of new
polyanilines as described below.
As described above, we previously reported the polycon-
densation of 1a with the diGrignard reagent of p-dibro-
mobenzene in the presence of NiCl2(dppp).4 We now
report preparation of polyanilines by C–N coupling of
1a and 1b with 2,5-dihalothiophenes, as depicted in
Scheme 3. The polycondensation was carried out by using
1.0 mmol of 1a or 1b and 1.0 mmol of the diGrignard
reagent of 2,5-dihalothiophenes in the presence of 0.03
mmol of NiCl2(dppp) in 10 mL of THF under reflux.
After 24 h, the reaction mixture was poured into diluted
hydrochloric acid. After neutralization with aqueous
ammonium, the polymer was separated by filtration,
washed with water and MeOH, and dried under vacuum.
The obtained pernigraniline-type polymers seemed to be
partly reduced to give emeraldine-type polymers on
washing the polymer with hydrochloric acid, aqueous
ammonia and methanol. IR (e.g. appearance of the
w(N–H) peak at about 3350 cm−1), 1H NMR and
elemental analytical data5 supported this view. The yield
of polymers was about 60%. It is known that pernigrani-
line-type polymers and oligomers are reduced to stable
emeraldine-type compounds in aqueous media under
various conditions.8,10 PThDMAN and PHThDMAN
were partly (about 30 and 50%, respectively)
Table 1 summarizes optical data of 2–5. The UV–vis
absorption peaks of 2–5 appear near those of the reported

T. Yamamoto et al. / Tetrahedron Letters 42 (2001) 8653–8656
8655
Scheme 3.
3. (a) Yamamoto, T. Bull. Chem. Soc. Jpn. 1999, 72, 621;
(b) Yamamoto, T.; Yamamoto, A. Chem. Lett. 1977, 353.
4. Yamamoto, T.; Nurulla, I. Jpn. J. Appl. Phys. 1999, 38,
892.
soluble in DMF; they were also partly soluble in NMP
and CF3COOH. GPC data (eluent=DMF containing
0.01 M LiBr) of PThDMAN and PHThDMAN gave a
number average molecular weights of 9.2 and 9.4×103,
respectively. Since the soluble part and the insoluble
part give the same IR spectrum, the fraction with lower
molecular weights is considered to be soluble in DMF.
Cyclic voltammogram of a cast film of PHThDMAN
on a Pt plate shows an oxidation peak at 1.05 V versus
Ag+/Ag in an CH3CN solution of [NBu4]PF6 (0.10 M).
PThAN and PHThAN were slightly soluble in
CF3COOH and DMF, and determination of their
molecular weights was not possible.
5. Spectroscopic and elemental analytical data for 1b and
the C–N coupling products. 1b: 1H NMR (CDCl3; 400
MHz) l 7.27 (m, 2H, J=4.0 Hz), 2.24 (d, 6H, J=1.4
Hz). Anal. calcd for C8H8Cl2N2: C, 47.32; H, 3.97; N,
13.92; Cl, 34.80. Found: C, 47.47; H, 4.03; N, 13.95; Cl,
1
34.48%. 2: H NMR (CDCl3; 400 MHz) l 7.17 (d, 0.6H,
J=2 Hz, cis-quinoide-H), 6.94 (dd, 1.4H, J=2. 8 Hz, 10
Hz, trans-quinoide-H), 6.89 (s, 2.8H, trans-ArH), 6.84 (s,
1.2H, cis-ArH), 6.48 (dd, 1.4H, J=2.8 Hz, 10 Hz, trans-
quinoide-H), 6.23 (d, 0.6H, J=2 Hz, cis-quinoide-H),
2.30 (s, 4.2H, trans-quinoide-CH3), 2.26 (s, 1.8H, cis-
quinoide-CH3), 1.91 (s, 8.4H, trans-quinoide-CH3), 1.87
(s, 3.6H, cis-quinoide-CH3). Anal. calcd for C24H26N2: C,
84.17; H, 7.65; N, 8.18. Found: C, 84.51; H, 7.74; N,
8.17%. 3: 1H NMR (CDCl3; 400 MHz) l 7.24 (d, 2H,
J=8.0 Hz), 7.20 (t, 2H, J=8.0 Hz), 7.07 (t, 2H, J=8.0
Hz), 6.64 (d, 2H, J=8.0 Hz), 6.54 (d, 2H, J=1.6 Hz),
2.15 (d, 6H, J=1.6 Hz, CH3), 2.12 (s, 6H, CH3). Anal.
calcd for C22H22N2: C, 84.04; H, 7.05; N, 8.91. Found: C,
As described above, polyaniline-type oligomers and
polymers can be prepared by the nickel complex-pro-
moted C–N coupling reaction. The proposed polycon-
densation method is expected to give various new
polyaniline-type polymers.
References
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84.04; H, 7.16; N, 8.70%. 4: H NMR (CDCl3; 400 MHz)
l 7.18 (d, 4H, J=8.0 Hz), 6.74 (d, 4H, J=8.0 Hz), 6.68
(s, 2H), 2.37 (s, 6H, CH3), 2.12 (s, 6H, CH3). Anal. calcd
for C22H22N2: C, 84.04; H, 7.05; N, 8.91. Found: C,
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84.00; H, 7.28; N, 8.63%. 5: H NMR (CDCl3; 400 MHz)
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2H, J=8.0), 7.54–7.44 (m, 6H), 6.79 (d, 2H, J=8.0 Hz),
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7.34; N, 8.66%. PThDMAN: Anal. calcd for
((C12H10N2S)(C12H12N2S)·2H2O)n: C, 61.78; H, 5.62; N,
12.01. Found: C, 61.93; H, 5.61; N, 11.81%.
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T. Yamamoto et al. / Tetrahedron Letters 42 (2001) 8653–8656
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afford a Ni(Ar)(-Nꢁ) species, and (iii) reduction elimination
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cies, similar to the Ni-promoted C–C coupling reaction.1b
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