Electrochemical dimerization of phenacyl bromides N-acylhydrazones - A new way to 1-N-acylamino-2,5-diaryl-pyrroles

Article abstract of DOI:10.1016/j.tet.2004.07.092

Cathodic reduction of phenacyl bromides N-acyl hydrazones lead to dimeric 1,4-diaryl-1,4-butanedione di-N-acylhydrazones, which give the corresponding 1-N-acylamino-2,5-diarylpyrroles in good yields. Graphical Abstract.

Full text of DOI:10.1016/j.tet.2004.07.092

Tetrahedron 60 (2004) 10787–10792
Electrochemical dimerization of phenacyl bromides
N-acylhydrazones—a new way to
1-N-acylamino-2,5-diaryl-pyrroles
Belen Batanero,a Michail N. Elinsonb and Fructuoso Barbaa,
*
a
´
´
Department of Organic Chemistry, University of Alcala, Campus Universitario, 28871 Alcala de Henares Madrid, Spain
bN. D Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky pr. 47, 119991 Moscow, Russian Federation
Received 8 June 2004; revised 22 July 2004; accepted 29 July 2004
Available online 29 September 2004
Abstract—Cathodic reduction of phenacyl bromides N-acyl hydrazones lead to dimeric 1,4-diaryl-1,4-butanedione di-N-acylhydrazones,
which give the corresponding 1-N-acylamino-2,5-diarylpyrroles in good yields.
q 2004 Published by Elsevier Ltd.
1. Introduction
synthesis.9 We have prepared electrochemically in such
manner several classes of compounds such as 4-aryl-2-
methylfurans,10 imidazo[2,1-b][1,3,4]-oxadiazines,11
[1,3]oxathiolan-5-ones,12 tetrahydrofuran-2-ols,13 3-
chloro-1,4-disubstituted-2(1H)-quinolinones.14
1-Aminopyrroles and N-substituted-1-aminopyrroles are a
class of useful intermediates in organic chemistry which
possess a wide range of the properties expected for N,N-
disubstituted hydrazines.1 Furthermore, 1-N-carbalkoxya-
minopyrroles undergo efficient Diels–Alder reaction with
electron deficient olefins.2 Some 1-N-substitutedaminopyr-
roles and their derivatives have shown antibacterial
activity.3 1-N-Aminoacetamido-2,5-dialkylpyrroles have
exhibited analgesic and anesthetic properties.4 1-N-Carbalk-
oxyaminopyrroles have been used in synthesis of anxiolytic
agents.5 Systems based on the reaction of iron salts with
heterocyclic hydrazines have been used in photothermo-
graphic processes.6
Several years ago, we reported the cathodic reduction of
phenacyl bromide semicarbazones leading to the dimeric
semicarbazones which were converted into either 1,4-
diaryl-1,4-butanediones and 2,5-diarylfuranes15 or 3,6-
diarylpyridazines.16
In the present study we wish to report a facile and
convenient way to 1-N-acylamino-2,5-diarylpyrroles start-
ing from phenacyl bromides 1a–f, which first were
converted into phenacyl bromide N-acylhydrazones 2a–f.
The electrochemical reduction of phenacyl bromide N-
acylhydrazones led to the dimeric 1,4-diaryl-1,4-butane-
dione di-N-acylhydrazones 3a–f. Heating of dimers 3a–f
gave the corresponding 1-N-acylamino-2,5-diarylpyrroles
4a–f. Our syntheses are summarized in Scheme 1.
Recent advances in electroorganic chemistry have provided
organic chemists with a new versatile synthetic device of a
great promise.7 Despite the long history of electroorganic
chemistry, most of the electroorganic reactions that could
provide product selectivity have been developed within the
last twenty five years.8 Research of various applications has
spread gradually to cover many areas of fundamental and
industrial organic chemistry.
2. Results and discussion
Acylhydrazones 2a–f were obtained in nearly quantative
yields using a modified known procedure.17 Electroreduc-
tion of 2a–f was accomplished in a divided cell on the
mercury cathode. The first step in this process apparently
involves two-electron cleavage of the carbon–bromine bond
with the formation of anion A and bromide anion (Scheme
2).18 Subsequent nucleophilic attack of anion A on the
molecule of starting substrate 2a–f lead to dimeric
Among them the cathodic reduction of a-halocarbonyl
compounds has proved to be a very good tool in organic
Keywords: Phenacyl bromides; Acylhydrazones; Electrochemical dimer-
ization; Cyclization; Substituted pyrroles; Isomeric amides; Restricted
rotation.
* Corresponding author. Tel.: C34-91-885-46-17; fax: C34-91-885-46-
86; e-mail: fructuoso.barba@uah.es
0040–4020/$ - see front matter q 2004 Published by Elsevier Ltd.
doi:10.1016/j.tet.2004.07.092

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B. Batanero et al. / Tetrahedron 60 (2004) 10787–10792
Scheme 1. (i) HC, MeOH/H2O; (ii) electrochemical dimerization; Hg-cathode, solvent–DMF, supporting electrolyte LiClO4, divided cell; (iii) DMF reflux 1 h,
or AcOH/EtOH, reflux 4 h.
compounds 3a–f (Table 1). Similar dimers were obtained
earlier by reduction of phenacyl bromides semicarbazones
in a divided cell.15,16 Further heating of 3a–c in refluxing
dimethylformamide (method A, Table 1) resulted in the
formation of cyclic pyrroles 4a–c in good yield. In contrast
to 3a–c, dimers 3d–f were stable in boiling dimethylforma-
mide. It should be mentioned that dimers of phenacyl
bromides semicarbazones, that is, 1,4-diaryl-1,4-butane-
dione disemicarbazones in boiling dimethylformamide were
converted into 3,6-diarylpyridazines.16 Cyclization of 3d–f
Scheme 2.

B. Batanero et al. / Tetrahedron 60 (2004) 10787–10792
Table 1. Synthesis of 1-N-acylamino-2,5-diarylpyrroles
10789
N-Acyl hydrazones
Di-N-acyl hydrazones
Yield (%)a
Method of cyclization
Pyrrole
Yield (%)a
2a
2b
2c
2d
2e
2f
3a
3b
3c
3d
3e
3f
69
64
62
81
85
82
A and B
A and B
A and B
B
B
B
4a
4b
4c
4d
4e
4f
73 and 71
76 and 72
63 and 65
87
78
72
a
Isolated yields.
into the corresponding pyrroles 4a–f was achieved in good
yields by refluxing in the mixture of acetic acid/ethanol
(1:1) (method B, Table 1). Dimers 3a–c were also
transformed into pyrroles 4a–c using method B.
The (Z)-structures of 4d–f main isomer were established by
NOE experiments which show the close proximity of the
amide proton and the methyl group (Table 3). For 4a–c the
1H NMR spectra show a single absorption for the NH,
olefinic, and methyl protons due to the rapid interconversion
of the Z and E isomers. This could be because conjugation
between the carbonyl group and the benzene ring weakens
the double bond character of the carbon–nitrogen bond.
The 1H NMR and 13C NMR spectra of pyrroles 4d–f showed
the presence of two isomers for each compound (Scheme 3).
The ratio of isomers depends on the solvent (Table 2). It is
known that in a few cases single bond rotation is so slow that
(E)- and (Z)-isomers can be detected on the NMR time scale
even where no double bond exists,19 for example,
thioamides and certain amides,20 because resonance gives
the single bond some double bond character and slows
rotation.21
As to our knowledge only one 1-N-acylamino-2,5-diaryl-
pyrrole, namely 1-N-acetylamino-2,5-diphenylpyrrole is
known in the chemical literature.22,23 In both cases it was
synthesized by action of acetyl anhydride on 1-amino-2,5-
diphenylpyrrole.
3. Conclusion
Thus the electrochemical dimerization of phenacyl
bromides N-acylhydrazones into dimeric 1,4-diaryl-1,4-
butanedione di-N-acylhydrazones and further cyclization of
dimers gives 1-N-acylamino-2,5-diarylpyrroles in good
yields. This constitutes a facile and efficient method for
the transformation of phenacyl bromides into 1-N-acyl-
amino-2,5-diarylpyrroles, which are convenient and useful
intermediates for organic chemistry and synthesis of
pharmacology active agents.
The procedure uses inexpensive reagents, it is easily carried
out, and the work up is very simple.
4. Experimental
Scheme 3.
The electrolyses were carried out using an Amel potentiostat
Model 552 with electronic integrator Amel Model 721.
Mass spectra (EI, ionizing voltage 70 eV) were determined
using a Hewlett–Packard Model 5988A mass-selective
detector equipped with a Hewlett–Packard Ms Chem
Station. IR spectra of the compounds were recorded as
dispersions in KBr on a Perkin–Elmer Model 583
Table 2. Ratio of isomer in 1-N-acetylamino-2,5-diarylpyrrolesa
1-N-Acetyl-
aminopyrrole
CDCl3
Acetone-d6
DMSO-d6
4d
4e
4f
4:3
2:1
6:5
5:1
7:1
7:2
7:1
10:1
6:1
1
spectrometer. H and 13C NMR spectra for 2a–f and 3a–f
a
1HMR data at 25 8C.
were recorded in CDCl3 on Varian Unity 300 (300 MHz)
spectrometer, for 4a–f on Varian Unity 500-PLUS
(500 MHz) spectrometer with tetramethylsilane (TMS) as
the internal standard. All melting points were measured on a
Reichert Thermovar microhot stage apparatus and are
uncorrected.
Table 3. 1H NMR characteristic signals in CDCl3 for isomers of 1-N-
acetylamino-2,5-diarylpyrrolesa
1-N-Acetyl-
aminopyrrole
NH
CH]
CH3
4d
4e
4f
7.77; 8.29
7.77; 8.26
7.64; 8.11
6.35; 6.41
6.32; 6.61
6.25; 6.30
1.89; 1.38
1.92; 1.36
1.90; 1.39
4.1. General procedure for the preparation of phenacyl
bromides N-acylhydrazones 2a–f
a
Signals of minor isomer in italics.
Phenacyl bromides (20 mmol) were slowly added in solid

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B. Batanero et al. / Tetrahedron 60 (2004) 10787–10792
state (1a as a solution in 20 ml of MeOH) to a solution of
hydrazone (40 mmol) and 2 ml of 5% HCl in 60 ml of a
mixture of MeOH/H2O under rapid stirring below 5 8C. The
stirring was maintained for 24 h to complete the reaction.
The quantitatively precipitated solid was isolated by
filtration. The precipitate was washed consequently with
chloroform and hexane (2a–c) or with hexane only (2d–f)
and used for the next reaction without further purification.
4.2. General procedure for the electrochemical
dimerization of phenacyl bromides N-acylhydrazones
3a–f
Anhydrous lithium perchlorate (10 mmol) was dissolved in
40 ml of dry dimethylformamide. 20 ml of this solution was
placed in the cathode compartment and the other 20 ml in
the anode compartment of the divided (porous glass
diaphragm) electrolytic cell. Then the corresponding
phenacyl bromide hydrazone (5 mmol) was added to the
cathode compartment. For prevention of the accumulation
of electrogenerated acid, anhydrous sodium carbonate (3 g)
was placed in the anode compartment. The electrolyses
were carried out under controlled cathodic potential at
K1 V versus SCE. The charge consumed was 1 F/mol in all
cases. At the end of the electrolysis, the cathodic solution
was poured onto ice water (150 ml). In the case of 3d–f the
cathodic solution was evaporated under reduced pressure up
to 10 ml before this operation. After 12 h, the precipitated
solid isolated by filtration was washed with chloroform and
used for the next reaction without further purification.
Analytically pure samples of 3a–f were obtained by
crystallization from dimethylsulphoxide–methanol.
4.1.1. Phenacyl bromide N-(4-methylbenzoyl)hydrazone
2a. Yield 6.09 g (92%), mp 133–134 8C. 1H NMR (CDCl3):
d 2.34 and 2.41 (s, 3H), 4.34 and 4.42 (s, 2H), 7.15–7.80 (m,
9H), 9.03 and 9.18 (bs, 1H). IR: 3469, 3299, 3028, 1655,
1535, 1468, 1272, 1178, 831, 770. Anal. Calcd for
C16H15BrN2O: C, 58.02; H, 4.56; Br, 24.12; N, 8.46.
Found: C, 57.83; H, 4.65; Br, 23.89; N, 8.37.
4.1.2. 4-Chlorophenacyl bromide N-(4-methylbenzoyl)-
hydrazone 2b. Yield 6.87 g (94%), mp 144–146 8C. H
1
NMR (CDCl3): d 2.36 and 2.42 (s, 3H), 4.36 and 4.44 (s,
2H), 7.20–7.80 (m, 8H), 9.11 and 9.25 (bs, 1H). IR: 3466,
3154, 3009, 1646, 1506, 1455, 1280, 1129, 995, 830, 752.
Anal. Calcd for C16H14BrClN2O: C, 52.56; H, 3.86; Br,
21.85; Cl, 9.70; N, 7.66. Found: C, 52.37; H, 3.72; Br,
21.89; Cl, 9.53; N, 7.51.
4.2.1. 1,4-Diphenyl-1,4-butanedione di-N-(4-methyl-
benzoyl)hydrazone 3a. Yield 0.87 g (69%), mp 192–
194 8C. 1H NMR (DMSO-d6): d 2.38 (s, 6H), 3.12 (s,
4H,), 7.20–7.80 (m, 18H,), 10.82 (bs, 2H). IR: 3336, 3249,
1651, 1524, 1471, 1274, 1116, 918, 829, 744, 692. Anal.
Calcd for C32H30N4O2: C, 76.47; H, 6.02; N, 11.15. Found:
C, 76.21; H, 5.92; N, 10.97.
4.1.3. 4-Methoxyphenacyl bromide N-(4-methyl-
benzoyl)hydrazone 2c. Yield 6.57 g (91%), mp 118–
120 8C. H NMR (CDCl3): d 2.35 and 2.41 (s, 3H), 3.82
1
and 3.86 (s, 3H), 4.32 and 4.41 (s, 2H), 6.90–7.80 (m, 8H),
9.15 and 9.36 (bs, 1H). IR: 3467, 3153, 2995, 1640, 1609,
1455, 1249, 1174, 829, 751. Anal. Calcd for C17H17BrN2O2:
C, 56.52; H, 4.74; Br, 22.12; N, 7.75. Found: C, 56.63; H,
4.85; Br, 21.89; N, 7.53.
4.2.2. 1,4-Di-(4-chloro)phenyl-1,4-butanedione di-N-(4-
methylbenzoyl)hydrazone 3b. Yield 0.91 g (64%), mp
219–221 8C. H NMR (DMSO-d6): d 2.37 (s, 6H), 3.12 (s,
4H,), 7.20–7.85 (m, 16H), 10.72 (bs, 2H). IR: 3466, 3232,
1647, 1521, 1487, 1271, 1091, 833, 744, 669. Anal. Calcd
for C32H28Cl2N4O2: C, 67.25; H, 4.94; Cl, 12.41; N, 9.80.
Found: C, 67.11; H, 4.82; Cl, 12.18; N, 9.67.
1
4.1.4. Phenacyl bromide N-acetylhydrazone 2d. Yield
4.49 g (88%), mp 126–128 8C. 1H NMR (CDCl3): d 2.41 (s,
3H), 4.29 (s, 2H,), 7.41 (m, 3H), 7.75 (m, 2H), 9.35 (bs, 1H).
IR: 3466, 3199, 3044, 1669, 1553, 1260, 1119, 1003, 776,
690. Anal. Calcd for C10H11BrN2O: C, 47.08; H, 4.35; Br,
31.32; N, 10.98. Found: C, 47.22; H, 4.39; Br, 31.13; N,
10.72.
4.2.3. 1,4-Di-(4-methoxy)phenyl-1,4-butanedione di-N-
(4-methylbenzoyl)hydrazone 3c. Yield 0.87 g (62%), mp
215–217 8C. H NMR (DMSO-d6): d 2.37 (s, 6H), 3.05 (s,
1
4H,), 3.76 (s, 6H), 6.80–7.80 (m, 16H), 10.61 (bs, 2H). IR:
3473, 3261, 1651, 1608, 1498, 1257, 1176, 1022, 829, 747.
Anal. Calcd for C34H34N4O2: C, 72.58; H, 6.09; N, 9.96.
Found: C, 72.31; H, 5.91; N, 9.78.
4.1.5. 4-Chlorophenacyl bromide N-acetylhydrazone 2e.
Yield 5.38 g (93%), mp 146–148 8C. H NMR (CDCl3): d
1
4.2.4. 1,4-Diphenyl-1,4-butanedione di-N-acetylhydra-
zone 3d. Yield 0.71 g (81%), mp 192–194 8C. H NMR
2.40 (s, 3H), 4.27 (s, 2H,), 7.37 (d, 2H, JZ8.7 Hz), 7.68 (d,
2H, JZ8.7 Hz), 9.43 (bs, 1H). IR: 3468, 3189, 3081, 1669,
1599, 1378, 1336, 1094, 1009, 834. Anal. Calcd for
C10H10BrClN2O: C, 41.48; H, 3.48; Br, 27.60; Cl, 12.24;
N, 9.67. Found: C, 41.32; H, 3.55; Br, 27.38; Cl 12.05; N,
9.46.
1
(DMSO-d6): d 1.99 and 2.15 (s, 6H), 2.89 and 2.92 (s, 4H,),
7.30–7.60 (m, 10H), 10.75 (bs, 2H). IR: 3428, 3227, 1658,
1459, 1383, 1128, 1006, 862, 769, 687. Anal. Calcd for
C20H22N4O2: C, 68.55; H, 6.33; N, 15.99. Found: C, 68.41;
H, 6.25; N, 15.78.
4.1.6. 4-Methoxyphenacyl bromide N-acetylhydrazone
2f. Yield 4.84 g (85%), mp 133–135 8C. 1H NMR (CDCl3):
d 2.40 (s, 3H), 3.82 (s, 3H), 4.27 (s, 2H,), 6.91 (d, 2H, JZ
8.8 Hz), 7.81 (d, 2H, JZ8.8 Hz), 9.38 (bs, 1H). IR: 3467,
3153, 2995, 1640, 1609, 1455, 1249, 1174, 829, 751. Anal.
Calcd for C11H13BrN2O2: C, 46.34; H, 4.60; Br, 28.02; N,
9.82. Found: C, 46.17; H, 4.55; Br, 27.88; N, 9.56.
4.2.5. 1,4-Di-(4-chloro)phenyl-1,4-butanedione di-N-
acetylhydrazone 3e. Yield 0.89 g (85%), mp 242–244 8C.
1H NMR (DMSO-d6): d 1.97 and 2.13 (s, 6H), 2.89 and 2.91
(s, 4H,), 7.30–7.55 (m, 8H), 10.73 (bs, 2H). IR: 3446, 3235,
1668, 1533, 1490, 1322, 1091, 1011, 845, 668. Anal. Calcd
for C20H20Cl2N4O2: C, 57.29; H, 4.81; Cl, 16.91; N, 13.36.
Found: C, 57.11; H, 4.91; Cl, 16.76; N, 13.15.

B. Batanero et al. / Tetrahedron 60 (2004) 10787–10792
10791
4.2.6. 1,4-Di-(4-methoxy)phenyl-1,4-butanedione di-N-
acetylhydrazone 3f. Yield 0.84 g (82%), mp 210–212 8C.
1H NMR (DMSO-d6): d 1.98 and 2.14 (s, 6H), 2.83 and 2.85
(s, 4H,), 3.77 (s, 6H), 6.90–7.80 (m, 8H), 10.67 (bs, 2H). IR:
3447, 3222, 1651, 1513, 1334, 1258, 1102, 1029, 833, 668.
Anal. Calcd for C22H26N4O4: C, 64.38; H, 6.38; N, 13.65.
Found: C, 64.17; H, 6.36; N, 13.49.
4.3.4. 1-N-Acetylamino-2,5-diphenylpyrrole 4d. Mp 206–
208 8C. 1H NMR (CDCl3) two isomers: d 1.38 and 1.89 (s,
3H), 6.35 and 6.41 (s 2H), 7.27–7.45 (m, 10H), 7.77 and
8.29 (bs, 1H). 13C NMR (CDCl3): d 18.7, 20.0, 108.1, 108.2,
127.3, 127.4, 127.7, 128.0, 128.4, 128.7, 128.9, 129.9,
130.8, 131.6, 135.7, 136.3, 169.6, 174.3. MS m/z (relative
intensity) EI: 276 (MC, 100), 233(39), 218(26), 204(12),
130(65), 115(17), 102(58), 77(32), 63(18). IR: 3463, 3184,
3028, 1668, 1543, 1449, 1270, 965, 756, 619. Anal. Calcd
for C18H16N2O: C, 78.24; H, 5.84; N, 10.14. Found: C,
78.13; H, 5.81; N, 9.95.
4.3. General procedure for the cyclization of di-N-
acylhydrazones 3a–f
Cyclization. Method A. The di-N-acylhydrazones 3a–c
(1 mmol) were refluxed 1 h in 4 ml of dry dimethylforma-
mide, then the solvent was evaporated under reduced
pressure and the residue was crystallized from ethanol or
chloroform–hexane. Isolated yields are presented in
Table 1.
4.3.5. 1-N-Acetylamino-2,5-di(4-chlorophenyl)pyrrole
4e. Mp 280–282 8C. 1H NMR (CDCl3) two isomers: d
1.36 and 1.92 (s, 3H), 6.32 and 6.41 (s, 2H), 7.35–7.40 (m,
8H), 7.77 and 8.26 (bs, 1H). 13C NMR (CDCl3): d 18.5,
20.9, 108.5, 108.7, 128.2, 128.8, 129.0, 129.1, 129.3, 129.4,
133.5, 134.3, 135.7, 136.6, 169.8, 174.5. MS m/z (relative
intensity) EI: 346 (MCC2, 63), 344 (MC, 100), 303(23),
301(28), 288(18), 286(25), 164(30), 130(57), 101(14),
75(12). IR: 3445, 3248, 3015, 1674, 1596, 1484, 1096,
1008, 828, 764. Anal. Calcd for C18H14Cl2N2O: C, 62.62;
H, 4.09; Cl, 20.54; N, 8.11. Found: C, 62.53; H, 3.98; Cl,
20.43; N, 7.95.
Cyclization. Method B. The di-N-acylhydrazones 3a–f
(1 mmol) were refluxed 1 h in 4 ml of a mixture of AcOH/
EtOH (1:1), then the solvent was evaporated under reduced
pressure and the residue was crystallized from ethanol or
chloroform–hexane. Isolated yields are presented in
Table 1.
4.3.6. 1-N-Acetylamino-2,5-di(4-methoxyphenyl)pyrrole
4f. Mp 220–222 8C. 1H NMR (CDCl3) two isomers: d 1.39
and 1.90 (s, 3H), 3.81 (s, 6H), 6.25 and 6.30 (s, 2H), 6.89 (m,
4H), 7.35 (m, 4H), 7.64 and 8.11 (bs, 1H). 13C NMR
(CDCl3): d 18.7, 21.0, 55.3, 107.2, 113.8, 114.2, 123.3,
123.5, 124.4, 128.1, 129.1, 129.4, 134.9, 135.6, 169.7,
174.5. MS m/z (relative intensity) EI: 336 (MC, 63), 321(4),
293(43), 278(57), 160(13), 132(80), 117(24), 102(10),
89(33), 63(14). IR: 3461, 3132, 2931, 1682, 1611, 1503,
1251, 1179, 1034, 836. Anal. Calcd for C20H20N2O3: C,
71.41; H, 5.99; N, 8.33. Found: C, 71.32; H, 6.04; N, 8.17.
4.3.1. 1-N-(4-Methylbenzoyl)amino-2,5-diphenylpyrrole
4a. Mp 276–278 8C. 1H NMR (CDCl3): d 2.33 (s, 3H), 6.41
(s, 2H), 7.20 (d, 2H, JZ8.1 Hz,), 7.24 (m, 2H), 7.32 (m,
4H), 7.46 (d, 2H, JZ8.1 Hz,), 7.52 (m, 4H), 8.18 (bs, 1H).
13C NMR (CDCl3): d 21.5, 108.2, 127.1, 127.3, 128.1,
128.4, 129.3, 129.5, 131.8, 134.9, 136.7, 143.0, 167.6. MS
m/z (relative intensity) EI: 352 (MC, 26), 233(9), 218(7),
194(3), 130(2), 119(100), 115(5), 102(7), 91(39), 65(12).
IR: 3449, 3219, 3015, 1654, 1532, 1304, 1287, 915, 746,
695. Anal. Calcd for C24H20N2O: C, 81.79; H, 5.72; N, 7.95.
Found: C, 81.66; H, 5.77; N, 7.82.
4.3.2. 1-N-(4-Methylbenzoyl)amino-2,5-di(4-chloro-
phenyl)pyrrole 4b. Mp 335–337 8C (dec). 1H NMR
(DMSO-d6): d 2.33 (s, 3H), 6.49 (s, 2H), 7.27 (d, 2H, JZ
8.3 Hz,), 7.41 (d, 4H, JZ8.5 Hz), 7.56 (d, 4H, JZ8.5 Hz),
7.63 (d, 2H, JZ8.3 Hz), 11.71 (bs, 1H). 13C NMR (CDCl3):
d 20.5, 107.4, 126.6, 127.8, 128.0, 128.4, 128.6, 129.6,
130.9, 133.8, 141.9, 164.9. MS m/z (relative intensity) EI:
422 (MCC2, 6), 420 (MC, 8), 303(1), 301(1), 288(1),
286(1), 267(1), 119(100), 91(25), 65(6). IR: 3481, 3209,
3009, 1648, 1528, 1483, 1285, 1090, 832, 771. Anal. Calcd
for C24H18Cl2N2O: C, 68.42; H, 4.31; Cl, 16.83; N, 6.65.
Found: C, 68.51; H, 4.39; Cl, 16.73; N, 6.51.
Acknowledgements
The Spanish Ministry of Science and Education CTQ2004-
05394/BQU financed this study. B. Batanero thanks the
Spanish Ministry of Science and Technology for the Ramon
y Cajal contract. We are also grateful to the Ministry of
Education and Science of Spain for financial support of
´
Prof. M. N. Elinson in University Alcala de Henares SAB-
2002-0039.
References and notes
4.3.3. 1-N-(4-Methylbenzoyl)amino-2,5-di(4-methoxy-
phenyl)pyrrole 4c. Mp 267–269 8C (dec). 1H NMR
(DMSO-d6): d 2.33 (s, 3H), 3.72 (s, 6H), 6.29 (s, 2H),
6.90 (d, 4H, JZ8.8 Hz), 7.27 (d, 2H, JZ8.3 Hz), 7.45 (d,
4H, JZ8.8 Hz), 7.65 (d, 2H, JZ8.3 Hz). 11.53 (bs, 1H). 13C
NMR (CDCl3): d 20.4, 59.7, 105.8, 113.3, 123.9, 126.8,
127.9, 128.3, 128.5, 128.7, 134.0, 141.8, 165.2. MS m/z
(relative intensity) EI: 412 (MC, 30), 293(16), 278(23),
235(5), 224(8), 133(9), 119(100), 91(85), 65(32). IR: 3460,
3207, 3003, 1648, 1566, 1464, 1296, 1172, 834, 772. Anal.
Calcd for C26H24N2O3: C, 75.71; H, 5.86; N, 6.79. Found:
C, 75.63; H, 5.81; N, 6.85.
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