Copper(I)-promoted regioselective α-tricyanoethenylation of N-methylpyrroles

Article abstract of DOI:10.1055/s-2008-1067178

The reaction of N-methylpyrroles with tetracyanoethylene (TCNE) has been studied in various solvents (DMSO, acetone, THF). A highly efficient protocol for the copper(I)-promoted regioselective α-tricyanoethenylation of N-methylpyrroles has been developed. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2008-1067178

PAPER
2631
Copper(I)-Promoted Regioselective a-Tricyanoethenylation of
N-Methylpyrroles
a
-Tricyanoethenyl
l
ation
o
a
N
-Methyl
dpyrroles islav N. Drichkov, Lyubov’ N. Sobenina, Tamara I. Vakul’skaya, Igor’ A. Ushakov, Al’bina I. Mikhaleva,
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, 1 Favorsky St., Irkutsk 664033,
Russian Federation
Fax +7(3952)419346; E-mail: boris_trofimov@irioch.irk.ru
Received 11 April 2008; revised 30 April 2008
CN
Abstract: The reaction of N-methylpyrroles with tetracyanoethyl-
TCNE
+
R
N
R
ene (TCNE) has been studied in various solvents (DMSO, acetone,
THF). A highly efficient protocol for the copper(I)-promoted regi-
oselective a-tricyanoethenylation of N-methylpyrroles has been de-
veloped.
N
Me
CN
Me
NC
1a–e
2a–e
NC
CN
CN
NC
CN
Key words: N-methylpyrroles, TCNE, tricyanoethenylation, cop-
per(I) bromide, regioselectivity
NC
+
+
R
R
N
N
Me
Me
Conjugated organic molecules containing simultaneously
donor and acceptor moieties are important components of
many electronic devices including nonlinear optical
(NLO), photoelectric, and photo- and electrolumines-
cent.1 Among these systems, heterocyclic compounds
such as pyrrole derivatives bearing electron-withdrawing
groups (e.g. tricyanoethenyl) are considered to be espe-
cially promising.2 Due to the strong solvatochromic prop-
erties caused by the donating–withdrawing interaction,
these materials can be used as model compounds for the
design of dyes possessing pronounced NLO characteris-
tics, which are used for the preparation of novel materials
with special electrooptical features such as frequency
doubling or wave mixing.3
3a–e
4b–e
R = H (a), Ph (b), 4-MeC6H4 (c), 4-MeOC6H4 (d), 4-ClC6H4 (e)
Scheme 1
The aim of this work is to investigate the reaction of N-
methylpyrroles with TCNE as well as to develop a method
for the selective introduction of the tricyanoethenyl moi-
ety into the N-methylpyrrole ring.
Our experiments have shown that 1-methyl-1H-pyrrole
(1a) reacts with TCNE in acetone and tetrahydrofuran
(r.t., 1 h) to afford a mixture of 2- and 3-isomers 2a/3a (ra-
tio 30:70 in acetone, 17:83 in THF) (Scheme 1). However,
in dimethyl sulfoxide the 2-isomer 2a predominates, its
content in the reaction mixture is 85% (Table 1).
Tricyanoethenyl derivatives of NH-pyrroles show photo-
sensitive effects and exhibit electroconductivity.4 The
substitution of hydrogen atom in the NH-pyrrole group for
other substituents can dramatically change the properties
of the compounds obtained, which is explained, firstly, by
the absence of a hydrogen bond affecting the electronic
and spatial structure of the molecules.
Under analogous condition 2-aryl-N-methylpyrroles 1b–e
and pyrrole 1a react with TCNE nonselectively to deliver
mixtures of 5-, 3- and 4-(tricyanoethenyl)pyrroles (2b–e,
3b–e, and 4b–e, respectively) (Scheme 1).
As can be seen from Table 1, the ratio of the tricyanoethe-
nylation products depends on the solvent. In dimethyl
sulfoxide, tricyanoethenylation of the pyrroles 1b–e oc-
curs mainly at positions 3 and 5 of the pyrrole nucleus to
give 3- and 5-(tricyanoethenyl)pyrroles 3b–e and 2b–e,
respectively. These compounds were separated by column
chromatography and characterized.
At the same time, substitution on the nitrogen atom of the
pyrrole ring frequently influences the regioselectivity of
tricyanoethenylation. For example, tricyanoethenylation
of 1-propyl-2-(2-thienyl)-1H-pyrrole with tetracyanoeth-
ylene (TCNE) furnishes three compounds, 3-, 4-, and 5-
(tricyanoethenyl)pyrroles, the former predominates.2 It
has been reported that selective tricyanoethenylation of N-
methylpyrrole with TCNE in acetone proceeds through
position 2 of the pyrrole ring.5 However, as shown here,
this reaction leads to a mixture of 2- and 3-(tricyanoethe-
nyl)pyrroles, where the latter prevail.
4-(Tricyanoethenyl)pyrroles 4b–e were formed in minor
quantities and characterized only by NMR techniques.
During the reaction of pyrroles 1b–e with TCNE in tet-
rahydrofuran, the relative amount of 4-(tricyanoethe-
nyl)pyrroles 4b–e increases, while the content of 5-
(tricyanoethenyl)pyrroles 2b–e decreases. Noteworthy is
that in this solvent under analogous conditions the tricya-
noethenylation occurs slower than in dimethyl sulfoxide
and is accompanied by a strong resinification making iso-
lation of the reaction products difficult.
SYNTHESIS 2008, No. 16, pp 2631–2635
x
x.
x
x
.
2
0
0
8
Advanced online publication: 17.07.2008
DOI: 10.1055/s-2008-1067178; Art ID: Z08708SS
© Georg Thieme Verlag Stuttgart · New York

2632
V. N. Drichkov et al.
PAPER
Table 1 1H NMR Monitoring of the Reaction of Pyrroles 1a–e with
Table 2 Tricyanoethenylation Using TCNE with Copper(I) Bro-
TCNE (r.t., 1 h)
mide/Lithium Bromide in Tetrahydrofuran
Entry
Pyrrole
Solvent
Product mix (%)
CN
TCNE
R
N
R
N
1
2
3
4
CuBr, LiBr
THF
Me
CN
Me
NC
1
2
1a
1a
1a
1b
1b
1b
1c
1c
1d
1d
1e
1e
acetone
DMSO
THF
0
0
0
30
85
17
29
53
15
50
18
39
12
45
17
70
15
83
43
37
40
37
57
57
19
40
25
–
1a–e
2a–e
–
Product
2a
R
Yield (%)
3
–
H
91
89
88
91
89
4
acetone
DMSO
THF
12
0
16
10
16
6
2b
Ph
5
2c
4-MeC6H4
6
28
6
2d
4-MeOC6H4
4-ClC6H4
7
DMSO
THF
2e
8
12
0
12
5
9
DMSO
THF
To elucidate the reaction mechanism in the presence of
the copper(I) bromide/lithium bromide system we carried
out ESR studies, taking N-methylpyrrole 1a as an exam-
ple. It has been found that with the addition of copper(I)
bromide and lithium bromide to a solution of TCNE in tet-
rahydrofuran the mixture turns brown and the ESR spec-
trum shows an unresolved singlet with a g factor of 2.0028
and width of 0.51 mT, the intensity of which increases
over 30 minutes. The value of the g factor practically cor-
responds to the g factor of radical anion of TCNE, but the
signal observed is not amenable to resolution, while its
width is significantly lower than the total width of the sig-
nal assigned to the radical anion of TCNE.
10
11
12
0
69
15
22
DMSO
THF
0
37
Thus, tricyanoethenylation of N-methylpyrroles repre-
sents a nonselective reaction. Particular emphasis is
placed upon the unusually high sensitivity of the ratio of
isomers to the nature of the solvent. This fact correlates
well with a radical ion mechanism for the reaction,6 i.e.
with the formation of strongly and variously solvated rad-
ical cation of the pyrrole and radical anion of tetracyano-
ethylene. Since the solvents used are strong donors, they
react primarily with the pyrrole radical cation, not only re-
distributing the electron density on the pyrrole ring, but
also sterically shielding certain positions of the pyrrole
ring.
The effects observed are likely to be interpreted as fol-
lows. When it is considered that the appearance of a nar-
row ESR signal in the system TCNE/CuBr/LiBr/THF is
caused by electron transfer from copper(I) to TCNE, then
one can conclude that the unresolved signal observed is
assigned to the complex of TCNE radical anion with cop-
per(II). The ESR spectrum of the studied system shows no
typical signal for divalence copper that can be explained
by the formation of the binuclear complex where antifer-
romagnetic interaction between copper ions can be real-
ized.8 Addition of the corresponding amount of N-
methylpyrrole 1a to this mixture leads to the rapid disap-
pearance of the ESR signal.
We have assumed that the introduction of additional re-
ducing agent (stronger than pyrrole) to the reaction mix-
ture could prevent the formation of the pyrrole radical
cation and, at the same time, retain the conditions for the
generation of radical anion TCNE. In this case, one should
expect the enhancement of the selectivity in the tricyano-
ethenylation, since the latter is dictated mainly by the at-
tack of the tricyanoethenyl radical anion (or the product of
its decyanation7) on the neutral molecule of pyrrole. Salts
of copper(I) appear to be such reducing agents. This as-
sumption is in good agreement with the known data that
TCNE reacts with transition metal ions in a low valence
state to provide the radical anion of TCNE.7
It seems likely that in the reaction mixture exists an equi-
librium between the [TCNE–·]2·[CuIIBr]2 complex and
2+
the very active tricyanoethenyl sp2 radical formed due to
its decyanation.7 The addition of N-methylpyrrole to the
system TCNE/CuBr/LiBr/THF involves the selective at-
tack of this radical at the a-position of the pyrrole ring to
furnish the more stable radical intermediate A (unlike the
attack at the b-position). Then the hydrogen radical is
cleaved from the a-position of the pyrrole ring to give pyr-
role 2a and reduce copper(II) to copper(I) (Scheme 2).
Indeed, N-methyl-substituted pyrroles react with TCNE in
the presence of the tetrahydrofuran-soluble copper(I) bro-
mide/lithium bromide system (LiBr is employed to in-
crease the solubility of CuBr) regioselectively to afford
exclusively the tricyanoethenylation products through the
a-position of the pyrrole ring, N-methyl-5-(tricyanoethe-
nyl)pyrroles 2a–e, which were isolated in 88–91% yields
(Table 2).
In conclusion, we have described a simple and efficient
protocol for the copper(I)-promoted regioselective a-tri-
cyanoethenylation of N-methylpyrroles to give N-methyl-
Synthesis 2008, No. 16, 2631–2635 © Thieme Stuttgart · New York

PAPER
a-Tricyanoethenylation of N-Methylpyrroles
2633
1H NMR (400 MHz, CDCl3): d = 3.96 (s, 3 H, NMe), 6.42 (dd,
J = 4.7, 2.5 Hz, 1 H, H4), 7.15 (dd, J = 2.5, 1.7 Hz, 1 H, H5), 7.58
(dd, J = 4.7, 1.7 Hz, 1 H, H3).
13C NMR (100 MHz, CDCl3): d = 37.4 (NMe), 81.9 [=C(CN)2],
112.6 (C4), 113.2 (2 CN), 113.3 (CN), 123.7 (C3), 125.0 (C2),
127.2 [(CN)C=], 137.2 (C5).
NC
NC
CN
CN
CuIBr
NC
NC
CN
CN
2+
[CuIIBr]2
1
/
2
– [CuIIBr(CN)]
2
NC
NC
CuI
CuII
Anal. Calcd for C10H6N4: C, 65.93; H, 3.32; N, 30.75. Found: C,
66.04; H, 3.42; N, 30.63.
CN
NC
CN
1a
CN
N
– H+
H
N
CN
CN
CN
1-Methyl-3-(tricyanoethenyl)-1H-pyrrole (3a)
Yield: 120 mg (66%, method C); mp 186–188 °C.
Me
Me
2a
A
IR (KBr): 2216 cm–1 (CN).
Scheme 2
1H NMR (400 MHz, CDCl3): d = 3.77 (s, 3 H, NMe), 6.76 (dd,
J = 3.2, 1.7 Hz, 1 H, H4), 7.01 (dd, J = 3.2, 1.6 Hz, 1 H, H5), 7.61
(dd, J = 1.7, 1.6 Hz, 1 H, H2).
13C NMR (100 MHz, CDCl3): d = 37.4 (NMe), 80.3 [=C(CN)2],
110.8 (C4), 112.4 (CN), 112.9 (CN), 113.8 (CN), 117.1 (C3), 126.9
(C5), 131.4 (C2), 133.7 [(CN)C=].
2-(tricyanoethenyl)pyrroles in excellent yields. This rep-
resents a useful addition to the growing applications of
donor–acceptor systems in preparative organic chemistry
and the manufacture of materials for advanced technolo-
gies.
Anal. Calcd for C10H6N4: C, 65.93; H, 3.32; N, 30.75. Found: C,
65.71; H, 3.46; N, 30.89.
IR spectra were measured on a Bruker IFS-25 spectrophotometer
(KBr pellets, 400–4000 cm–1). 1H NMR and 13C NMR spectra were
recorded on a Bruker DPX 400 instrument in CDCl3 using HMDS
1-Methyl-2-phenyl-5-(tricyanoethenyl)-1H-pyrrole (2b)
Yield: 230 mg (89%, method D); 75 mg (29%, method A); mp 148
°C.
1
as an internal standard. The concerted application of H-1H 2D
homonuclear experiments COSY and NOESY and also 1H-13C 2D
heteronuclear experiments HSQC and HMBC were used for the dis-
tinction of the carbon and proton resonances in all cases. ESR spec-
tra were recorded on a Radiopan SE/X-2547 spectrometer,
equipped with magnetometer and high frequency meter at r.t. in an
argon atmosphere.
IR (KBr): 2212 cm–1 (CN).
1H NMR (400 MHz, CDCl3): d = 3.85 (s, 3 H, NMe), 6.56 (d,
J = 4.6 Hz, 1 H, H3), 7.43 (m, 2 H, CHAr-2,6), 7.51 (m, 3 H,
CHAr-3,4,5), 7.61 (d, J = 4.6 Hz, 1 H, H4).
13C NMR (100 MHz, CDCl3): d = 35.8 (NMe), 79.7 [=C(CN)2],
113.0 (CN), 113.6 (CN), 113.7 (CN), 114.8 (C3), 124.1 (C4), 126.6
[(CN)C=], 128.2 (C5), 129.2 (CAr-3,5), 129.5 (CAr-2,6), 129.6
(CAr-1), 130.3 (CHAr-4), 150.4 (C2).
2-Aryl-1-methyl-1H-pyrroles 1a–e were prepared from 2-aryl-1H-
pyrroles and MeI via a published procedure.9
Reaction of Pyrroles 1a–e with TCNE; General Procedures for
Methods A–C
Anal. Calcd for C16H10N4: C, 74.40; H, 3.90; N, 21.69. Found: C,
74.22; H, 4.05; N, 21.51.
A soln of TCNE (128 mg, 1 mmol) in solvent [DMSO (method A),
THF (method B), acetone (method C)] (2 mL) was added to a soln
of pyrrole 1a–e (1 mmol) in the corresponding solvent (3 mL) at r.t.
The mixture was stirred for 1 h and then it was diluted with brine
(50 mL), extracted with CH2Cl2 (5 × 20 mL), and the extract dried
(MgSO4). The residue after removing the solvent was analyzed (1H,
13C NMR) and purified by column chromatography (silica gel,
Et2O–hexane, 1:1) to give pure products 2a–e and 3a–e. Com-
pounds 4b–e were found in the reaction mixture and identified only
by their NMR spectra. Their spectral characteristics are given be-
low.
1-Methyl-2-phenyl-3-(tricyanoethenyl)-1H-pyrrole (3b)
Yield: 93 mg (36%, method A); mp 148 °C.
IR (KBr): 2217 cm–1 (CN).
1H NMR (400 MHz, CDCl3): d = 3.50 (s, 3 H, NMe), 6.81 (d,
J = 3.5 Hz, 1 H, H5), 7.17 (d, J = 3.5 Hz, 1 H, H4), 7.28 (m, 2 H,
CHAr-2,6), 7.55 (m, 3 H, CHAr-3,4,5).
13C NMR (100 MHz, CDCl3): d = 35.3 (NMe), 83.2 [=C(CN)2],
109.2 (C4), 112.5 (CN), 112.8 (CN), 113.2 (CN), 115.4 (C3), 125.8
(C5), 128.1 (CAr-1), 128.7 (CAr-3,5), 130.6 (CAr-2,6), 130.9 (CAr-4),
135.0 [(CN)C=], 143.2 (C5).
Selective Synthesis of Pyrroles 2a–e; General Procedure for
Method D
Anal. Calcd for C16H10N4: C, 74.40; H, 3.90; N, 21.69. Found: C,
74.21; H, 3.72; N, 21.75.
CuBr (144 mg, 1 mmol) and LiBr (174 mg, 2 mmol) were added to
a soln of TCNE (128 mg, 1 mmol) in THF (17 mL) and the resulting
mixture was stirred until homogeneous (10 min). Then the soln was
added to a soln of pyrrole 1a–e (1 mmol) in THF (2 mL). The mix-
ture was stirred for 1 h and then diluted with brine (100 mL). The
precipitated residue was filtered off, dried, and washed with CH2Cl2
(40 mL). The solvent was removed under reduced pressure and res-
idue was purified by flash chromatography (silica gel, CH2Cl2) to
afford pure pyrroles 2a–e.
1-Methyl-2-phenyl-4-(tricyanoethenyl)-1H-pyrrole (4b)
1H NMR (400 MHz, CDCl3): d = 3.72 (s, 3 H, NMe), 7.03 (d,
J = 2.2 Hz, 1 H, H3), 7.36 (m, 2 H, CHAr-2,6), 7.54 (m, 3 H, CHAr-
3,4,5), 7.71 (d, J = 2.2 Hz, 1 H, H5).
13C NMR (100 MHz, CDCl3): d = 36.0 (NMe), 79.2 [=C(CN)2],
108.2 (C3), 112.5 (CN), 112.7 (CN), 113.5 (CN), 117.0 (C4), 128.7
(CAr-3,5), 129.3 (CAr-2,6), 129.4 (CAr-1), 130.6 (CAr-4), 133.7 (C5),
133.5 [(CN)C=], 139.9 (C2).
1-Methyl-2-(tricyanoethenyl)-1H-pyrrole (2a)
Yield: 166 mg (91%, method D); 111 mg (61%, method A); mp 148
°C.
IR (KBr): 2216 cm–1 (CN).
1-Methyl-2-(4-methylphenyl)-5-(tricyanoethenyl)-1H-pyrrole
(2c)
Yield: 240 mg (88%, method D); 76 mg (28%, method A); mp 182
°C.
Synthesis 2008, No. 16, 2631–2635 © Thieme Stuttgart · New York

2634
V. N. Drichkov et al.
PAPER
IR (KBr): 2218 cm–1 (CN).
13C NMR (100 MHz, CDCl3): d = 35.2 (NMe), 55.5 (OMe), 82.8
[=C(CN)2], 109.1 (C4), 112.6 (CN), 112.9 (CN), 113.3 (CN), 114.7
(CAr-3,5), 115.6 (C3), 119.9 (CAr-1), 125.6 (C5), 132.3 (CAr-2,6),
135.1 [(CN)C=], 143.4 (C2), 161.7 (CAr-4).
1H NMR (400 MHz, CDCl3): d = 2.43 (s, 3 H, CArMe), 3.84 (s, 3 H,
NMe), 6.55 (d, J = 4.7 Hz, 1 H, H3), 7.26–7.33 (m, 4 H, CHAr-2,3,5,6),
7.61 (d, J = 4.7 Hz, 1 H, H4).
Anal. Calcd for C17H12N4O: C, 70.82; H, 4.20; N, 19.43. Found: C,
71.12; H, 4.38; N, 19.28.
13C NMR (100 MHz, CDCl3): d = 21.5 (CArMe), 35.8 (NMe), 78.7
[=C(CN)2], 113.1 (CN), 113.6 (CN), 113.8 (CN), 114.7 (C3), 124.2
(C4), 126.2 [(CN)C=], 126.6 (CAr-1), 128.3 (C5), 129.4 (CAr-3,5),
129.9 (CAr-2,6), 140.8 (CAr-4), 150.8 (C2).
2-(4-Methoxyphenyl)-1-methyl-4-(tricyanoethenyl)-1H-pyr-
role (4d)
1H NMR (400 MHz, CDCl3): d = 3.69 (s, 3 H, NMe), 3.85 (s, 3 H,
OMe), 6.98 (m, 3 H, H3, CHAr-3,5), 7.28 (m, 2 H, CHAr-2,6), 7.65
(d, J = 2.0 Hz, 1 H, H5).
Anal. Calcd for C17H12N4: C, 74.98; H, 4.44; N, 20.58. Found: C,
74.68; H, 4.62; N, 20.45.
1-Methyl-2-(4-methylphenyl)-3-(tricyanoethenyl)-1H-pyrrole
(3c)
Yield: 87 mg (32%, method A); mp 167 °C.
IR (KBr): 2217 cm–1 (CN).
13C NMR (100 MHz, CDCl3): d = 36.2 (NMe), 55.5 (OMe), 79.7
[=C(CN)2], 108.3 (C3), 112.7 (CN), 113.1 (CN), 113.9 (CN), 114.4
(CAr-3,5), 117.4 (C4), 122.0 (CAr-1), 130.5 (CAr-2,6), 133.1
[(CN)C=], 134.0 (C5), 140.1 (C2), 160.4 (CAr-4).
1H NMR (400 MHz, CDCl3): d = 2.47 (s, 3 H, CArMe), 3.49 (s, 3 H,
NMe), 6.80 (d, J = 3.3 Hz, 1 H, H5), 7.16 (m, 3 H, H4, CHAr-2,6),
7.33 (m, 2 H, CHAr-3,5).
13C NMR (100 MHz, CDCl3): d = 21.5 (CArMe), 35.2 (NMe), 83.0
[=C(CN)2], 109.4 (C4), 112.4 (CN), 112.8 (CN), 113.2 (CN), 115.3
(C3), 125.0 (CAr-1), 125.6 (C5), 129.9 (CAr-3,5), 130.7 (CAr-2,6),
135.1 [(CN)C=], 141.2 (CAr-4), 143.5 (C2).
2-(4-Chlorophenyl)-1-methyl-5-(tricyanoethenyl)-1H-pyrrole
(2e)
Yield: 261 mg (89%, method D); 94 mg (32%, method A); mp 170–
172 °C.
IR (KBr): 2216 cm–1 (CN).
1H NMR (400 MHz, CDCl3): d = 3.83 (s, 3 H, NMe), 6.54 (d,
J = 4.6 Hz, 1 H, H3), 7.38 (m, 2 H, CHAr-2,6), 7.61 (m, 2 H,
CHAr-3,5), 7.59 (d, J = 4.6 Hz, 1 H, H4).
Anal. Calcd for C17H12N4: C, 74.98; H, 4.44; N, 20.58. Found: C,
75.15; H, 4.82; N, 20.44.
13C NMR (100 MHz, CDCl3): d = 35.8 (NMe), 80.8 [=C(CN)2],
112.8 (CN), 113.5 (2 CN), 114.5 (C3), 123.9 (C4), 126.8 [(CN)C=],
128.1 (CAr-1), 128.2 (C5), 129.6 (CAr-3,5), 130.7 (CAr-2,6), 136.7
(CAr-4), 148.8 (C2).
1-Methyl-2-(4-methylphenyl)-4-(tricyanoethenyl)-1H-pyrrole
(4c)
1H NMR (400 MHz, CDCl3): d = 2.40 (s, 3 H, CArMe), 3.70 (s, 3 H,
NMe), 7.00 (d, J = 2.2 Hz, 1 H, H3), 7.29 (m, 2 H, CHAr-2,6), 7.31
(m, 2 H, CHAr-3,5), 7.69 (d, J = 2.2 Hz, 1 H, H5).
Anal. Calcd for C16H9ClN4: C, 65.65; H, 3.10; Cl, 12.11; N, 19.14.
Found: C, 65.28; H, 3.17; Cl, 12.04; N, 19.37.
13C NMR (100 MHz, CDCl3): d = 21.5 (CArMe), 36.4 (NMe), 79.3
[=C(CN)2], 108.9 (C3), 112.6 (2 CN), 113.3 (CN), 117.2 (C4),
126.4 (CAr-1), 129.5 (CHAr-3,5), 130.0 (CHAr-2,6), 133.3 (C5),
133.4 [(CN)C=], 141.0 (CAr-4), 138.9 (C2).
2-(4-Chlorophenyl)-1-methyl-3-(tricyanoethenyl)-1H-pyrrole
(3e)
Yield: 82 mg (28%, method A); mp 191 °C.
IR (KBr): 2219 cm–1 (CN).
2-(4-Methoxyphenyl)-1-methyl-5-(tricyanoethenyl)-1H-pyr-
role (2d)
1H NMR (400 MHz, CDCl3): d = 3.48 (s, 3 H, NMe), 6.82 (d,
J = 3.4 Hz, 1 H, H5), 7.16 (d, J = 3.4 Hz, 1 H, H4), 7.27 (m, 2 H,
CHAr-2,6), 7.52 (m, 2 H, CHAr-3,5).
Yield: 262 mg (91%, method D); 58 mg (20%, method A); mp 209
°C.
IR (KBr): 2218 cm–1 (CN).
13C NMR (100 MHz, CDCl3): d = 35.7 (NMe), 83.9 [=C(CN)2],
109.4 (C4), 112.6 (CN), 112.7 (CN), 113.0 (CN), 115.4 (C3), 126.0
(C5), 126.5 (CAr-1), 129.6 (CAr-3,5), 132.2 (CAr-2,6), 134.7
[(CN)C=], 137.4 (CAr-4), 141.5 (C2).
1H NMR (400 MHz, CDCl3): d = 3.82 (s, 3 H, NMe), 3.86 (s, 3 H,
OMe), 6.52 (d, J = 4.4 Hz, 1 H, H3), 7.01 (m, 2 H, CHAr-3,5), 7.37
(m, 2 H, CHAr-2,6), 7.60 (d, J = 4.4 Hz, 1 H, H4).
Anal. Calcd for C16H9ClN4: C, 65.65; H, 3.10; Cl, 12.11; N, 19.14.
Found: C, 65.44; H, 3.27; Cl, 12.24; N, 19.31.
13C NMR (100 MHz, CDCl3): d = 36.0 (NMe), 55.6 (OMe), 78.1
[=C(CN)2], 113.3 (CN), 113.7 (CN), 114.0 (CN), 114.7 (C3), 114.8
(CAr-3,5), 121.8 (CAr-1), 124.5 (C4), 126.0 [(CN)C=], 128.5 (C5),
131.1 (CAr-2,6), 150.9 (C2), 161.3 (CAr-4).
2-(4-Chlorophenyl)-1-methyl-4-(tricyanoethenyl)-1H-pyrrole
(4e)
1H NMR (400 MHz, CDCl3): d = 3.71 (s, 3 H, NMe), 7.03 (d,
J = 2.2 Hz, 1 H, H3), 7.30 (m, 2 H, CHAr-2,6), 7.44 (m, 2 H,
CHAr-3,5), 7.71 (d, J = 2.20 Hz, 1 H, H5).
Anal. Calcd for C17H12N4O: C, 70.82; H, 4.20; N, 19.43. Found: C,
71.14; H, 4.21; N, 19.23.
2-(4-Methoxyphenyl)-1-methyl-3-(tricyanoethenyl)-1H-pyr-
role (3d)
Yield: 72 mg (25%, method A); mp 190 °C.
IR (KBr): 2216 cm–1 (CN).
13C NMR (100 MHz, CDCl3): d = 36.8 (NMe), 79.8 [=C(CN)2],
109.2 (C3), 112.4 (2 CN), 113.2 (CN), 117.4 (C4), 128.3 (CAr-1),
129.4 (CAr-3,5), 130.4 (CAr-2,6), 133.3 (C5), 134.1 [(CN)C=], 135.7
(CAr-4), 138.8 (C2).
1H NMR (400 MHz, CDCl3): d = 3.49 (s, 3 H, NMe), 3.87 (s, 3 H,
OMe), 6.79 (d, J = 3.2 Hz, 1 H, H5), 7.02 (m, 2 H, CHAr-3,5), 7.15
(d, J = 3.2 Hz, 1 H, H4), 7.20 (m, 2 H, CHAr-2,6).
Acknowledgment
This work was supported by the Innovation Agency of the Russian
Federation (grant no. NSH-263.2008.3).
Synthesis 2008, No. 16, 2631–2635 © Thieme Stuttgart · New York

PAPER
a-Tricyanoethenylation of N-Methylpyrroles
2635
(3) (a) Ogura, K.; Yanay, H.; Miokawa, M.; Akazome, M.
Tetrahedron Lett. 1999, 40, 8887. (b) Zhao, R.; Akazome,
M.; Matsumoto, S.; Ogura, K. Tetrahedron 2002, 58,
10225. (c) Zhao, R.; Akazome, M.; Matsumoto, S.; Ogura,
K. Bull. Chem. Soc. Jpn. 2002, 75, 2359. (d) Ogura, K.;
Zhao, R.; Jiang, M.; Akazome, M.; Matsumoto, S.;
Yamaguchi, K. Tetrahedron Lett. 2003, 44, 3595.
(e) Eckert, K.; Schroder, A.; Hartmann, H. Eur. J. Org.
Chem. 2000, 1327.
(4) Trofimov, B. A.; Sobenina, L. N.; Demenev, A. P.;
Mikhaleva, A. I.; Ushakov, I. A.; Tarasova, O. A.; Smirnov,
V. I.; Petrushenko, K. B.; Vokin, A. I.; Murzina, N. M.;
Myachina, G. F. ARKIVOC 2001, (ix), 37.
(5) (a) Sausen, G. N.; Engelhardt, V. A.; Middleton, W. J. J. Am.
Chem. Soc. 1958, 80, 2815. (b) McCormac, T.; Farrell, D.
Electrochim. Acta 2001, 46, 3287.
(6) Vokin, A. I.; Vakul’skaya, T. I.; Murzina, N. M.; Demenev,
A. P.; Sobenina, L. N.; Mikhaleva, A. I.; Trofimov, B. A.
Russ. J. Org. Chem. 2000, 36, 1504.
References
(1) (a) Varanasi, P. R.; Jen, A. K.-J.; Chandrasekhar, J.;
Namboothiri, I. N. N.; Rathna, A. J. Am. Chem. Soc. 1996,
118, 12443. (b) Albert, I. D. L.; Marks, T. J.; Ratner, M. A.
J. Am. Chem. Soc. 1997, 119, 6575. (c) Takahashi, K.;
Tarutani, S. Chem. Commun. 1998, 1233. (d) Schmitt, S.;
Baumgarten, M.; Simon, J.; Hafner, K. Angew. Chem. Int.
Ed. 1998, 37, 1078. (e) Suzuki, T.; Nishida, J.; Tsuji, T.
Chem. Commun. 1998, 1331. (f) Gonzalez, M.; Martin, N.;
Segura, J. L.; Seoane, C.; Garin, J.; Ornuda, J.; Alcala, R.;
Sanchez, C.; Villicampa, B. Tetrahedron Lett. 1999, 40,
8599. (g) Skabara, P. J.; Serebryakov, I. M.; Perepichka, I. F.
J. Chem. Soc., Perkin Trans. 2 1999, 505. (h) Mikami, S.;
Sugiura, K.; Miller, J. S.; Sakata, Y. Chem. Lett. 1999, 413.
(i) Kurata, H.; Inase, M.; Oda, M. Chem. Lett. 1999, 519.
(j) Lee, B.-L.; Yamamoto, T. Macromolecules 1999, 32,
1375. (k) Hirayma, D.; Yamashiro, T.; Takimiya, K.; Aso,
Y.; Otsubo, T.; Norieda, H.; Imahori, H.; Sakata, Y. Chem.
Lett. 2000, 570. (l) Skaraba, P. J.; Serebryakov, I. M.
Macromolecules 2001, 34, 2232.
(7) Miller, J. S. Angew. Chem. Int. Ed. 2006, 45, 2508.
(8) Solomon, E. I.; Sundraham, U. V.; Machonkin, T. E. Chem.
Rev. 1996, 96, 2563.
(2) Raposo, M. M. M.; Sousa, A. M. R. C.; Kirsch, G.; Ferreira,
F.; Belsley, M.; Gomes, E. M.; Fonseca, A. M. C.
(9) Heaney, H.; Ley, S. V. J. Chem. Soc., Perkin Trans. 1 1973,
Tetrahedron 2005, 61, 11991.
499.
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