Synthesis of unsymmetrical pyrrolo[3,2-b]pyrrole-2,5-diones and bis(quinazolin-4-on-2-yls) by double-anion-capture reactions of unsymmetrical oxaldi(arylimidoyl) dichlorides

Article abstract of DOI:10.1055/s-2006-942460

Unsymmetrical pyrrolo[3,2-b]pyrrole-2,5-diones and bis(quinazolin-4-on-2- yls) were prepared by one-pot cyclisations of unsymmetrical oxaldi(arylimidoyl) dichlorides. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2006-942460

PAPER
2507
Synthesis of Unsymmetrical Pyrrolo[3,2-b]pyrrole-2,5-diones and
Bis(quinazolin-4-on-2-yls) by Double-Anion-Capture Reactions of
Unsymmetrical Oxaldi(arylimidoyl) Dichlorides
Synthesisof
U
a
nsymmetri
l
k
rolo[3,2-
b
]py
o
rrole-2,5-dionesan
H
d
Bis(quinazolin-
e
4-on-2-yls)lmholz,a Rita Schroeder,a Peter Langer*b,c
a
b
c
Institut für Biochemie, Universität Greifswald, Soldmannstr. 16, 17487 Greifswald, Germany
Institut für Chemie, Universität Rostock, Albert-Einstein-Str. 3a, 18059 Rostock, Germany
Leibniz-Institut für Katalyse, Universität Rostock e. V., Albert-Einstein-Str. 29a, 18059 Rostock, Germany
Fax +49(381)4986412; E-mail: peter.langer@uni-rostock.de
Received 16 January 2006; revised 13 March 2006
Ar
Ar
Ar
R
O
O
Abstract: Unsymmetrical pyrrolo[3,2-b]pyrrole-2,5-diones and
bis(quinazolin-4-on-2-yls) were prepared by one-pot cyclisations of
unsymmetrical oxaldi(arylimidoyl) dichlorides.
N
O
O
N
R
O
O
R
N
N
Keywords: cyclisations, N-heterocycles, imidoyl chlorides, oxalyl
R
O
O
Ar
Ar
Ar
derivatives, pigments
A
C
B
C6H13
Pyrrolo[3,4-c]pyrrole-1,4-diones A, studied in detail by
Gompper and coworkers,1 are of considerable relevance
in the field of material sciences and have been used as key
building blocks of photo- and electroluminescent conju-
gated polymers D and dendritic structures.2 The isomeric
pyrrolo[3,2-b]pyrrole-2,5-diones C represent promising
pigment dyes3 and can be regarded as aza-analogues of
pulvinic dilactones B (Figure 1). The parent pulvinic
acids represent natural pigments isolated from lichens and
fungi.4 Pyrrolo[3,2-b]pyrrole-2,5-diones exhibit pigment
properties and a number of syntheses of symmetrical
derivatives have been reported.5,6 This includes, for
example, a three-step synthesis starting with (N-phenyl-
acetyl)acetic acid amino ester5a or a one-step approach us-
ing pulvinic acid (autoclave reaction, 140–180 °C).5b In
the course of our program directed to the development of
new cyclisation reactions7 of oxalic acid bis(imidoyl)
dichlorides,8 we have reported a versatile approach to
symmetrical pyrrolo[3,2-b]pyrrole-2,5-diones by one-pot
cyclisation (‘double-anion-capture reaction’) of ester eno-
lates with oxaldi(imidoyl) dichlorides.9 Recently, we have
extended our methodology and reported the first synthesis
of unsymmetrical oxalic acid bis(imidoyl) dichlorides.10
These new and important building blocks were success-
fully employed to the synthesis of unsymmetrical pyrro-
lo[3,2-b]pyrrole-2,5-diones.10a Herein, we report full
details of this study. In addition, we report the synthesis of
unsymmetrical bis(quinazolin-4-on-2-yls)11 based on
‘double-anion-capture reactions’ of methyl 2-aminoben-
zoate with oxaldi(imidoyl) dichlorides.
O
N
C6H13
N
O
C6H13
C6H13
n
D
Figure 1 Pyrrolo[3,4-c]pyrrole-1,4-diones and pyrrolo[3,2-b]pyr-
role-2,5-diones
The reaction of ethyl 2-chloro-2-oxoacetate with a num-
ber of anilines 1 gave the known12 ethyl 2-oxo-2-(aryl-
amino)acetates 2 (Scheme 1). The reaction of 2 with a
variety of anilines afforded the unsymmetrical oxala-
mides 3a–j (42–83%). Reflux of a toluene solution of ox-
alamides 3 with phosphorus pentachloride furnished, after
recrystallisation from n-heptane, the unsymmetrical oxal-
ic acid bis(imidoyl) dichlorides 4a–j (23–77%). The lith-
ium diisopropylamide mediated reaction of bis(imidoyl)
dichlorides 4 with various ethyl arylacetates 5 gave the
unsymmetrical pyrrolo[3,2-b]pyrrole-2,5-diones 6a–u
(Table 1). For all products, acceptable yields were ob-
tained, except for 6u. Pyrrolo[3,2-b]pyrrole-2,5-diones 6
exhibit a low solubility in organic solvents which is, in
fact, an important feature of pigment dyes. The products
were recrystallised from dimethyl sulfoxide or N,N-di-
methylformamide. The 13C NMR measurements required
long acquisition times.
All pyrrolo[3,2-b]pyrrole-2,5-diones 6 represent orange-
coloured pigment dyes. Similar to the symmetrical deriv-
atives,9 the UV–Vis absorptions were mainly influenced
by the aryl groups attached to the carbon atoms of the pyr-
rolo[3,2-b]pyrrole-2,5-dione core structure. Absorptions
in the range of lmax = 345–349 nm were observed for de-
rivatives containing a phenyl group (Ar3 = Ph). A batho-
chromic effect (ca. 15 nm) was observed for pyrrolo[3,2-
b]pyrrole-2,5-diones containing a p-tolyl group (Ar3 = p-
SYNTHESIS 2006, No. 15, pp 2507–2514
x
x.
x
x
.
2
0
0
6
Advanced online publication: 04.07.2006
DOI: 10.1055/s-2006-942460; Art ID: T00606SS
© Georg Thieme Verlag Stuttgart · New York

2508
F. Helmholz et al.
PAPER
Table 1 Products and Yields
3,4
a
a
b
b
b
c
6
a
b
c
d
e
f
Ar1
Ar2
Ar3
3 (%)a
4 (%)a
6 (%)a
54
54
35
30
21
28
33
25
32
46
31
32
30
32
28
26
38
42
35
27
10
UV–Vis (log e)/nm
347 (4.28)
361 (4.31)
347 (4.34)
383 (4.32)
361 (4.33)
349 (4.27)
363 (4.26)
347 (4.33)
361 (4.34)
349 (4.32)
362 (4.35)
347 (4.32)
361 (4.33)
383 (4.31)
346 (4.31)
361 (4.22)
347 (4.35)
361 (4.33)
345 (4.32)
346 (4.34)
357 (4.37)
C6H5
2-(MeO)C6H4
2-(MeO)C6H4
4-(MeO)C6H4
4-(MeO)C6H4
4-(MeO)C6H4
2,4-Me2C6H3
2,4-Me2C6H3
3,5-Me2C6H3
3,5-Me2C6H3
1-Naphthyl
C6H5
78,b 70c
60
C6H5
4-MeC6H4
C6H5
C6H5
85,d 85e
56
C6H5
4-(MeO)C6H4
4-MeC6H4
C6H5
C6H5
C6H5
63
56
65
42
65
65
56
59
c
g
h
i
C6H5
4-MeC6H4
C6H5
d
d
e
C6H5
C6H5
4-MeC6H4
C6H5
j
C6H5
e
k
l
C6H5
1-Naphthyl
4-MeC6H4
C6H5
f
4-MeC6H4
4-MeC6H4
4-MeC6H4
4-MeC6H4
4-MeC6H4
4-(MeO)C6H4
4-(MeO)C6H4
4-(MeO)C6H4
4-(MeO)C6H4
4-(O2N)C6H4
4-(MeO)C6H4
4-(MeO)C6H4
4-(MeO)C6H4
3,5-Me2C6H3
3,5-Me2C6H3
2,4-Me2C6H3
2,4-Me2C6H3
3,5-Me2C6H3
3,5-Me2C6H3
4-(MeO)C6H4
f
m
n
o
p
q
r
s
4-MeC6H4
4-(MeO)C6H4
C6H5
f
g
g
h
h
i
51
60
50
83
77
65
57
23
4-MeC6H4
C6H5
4-MeC6H4
C6H5
i
t
4-MeC6H4
4-MeC6H4
j
u
a Yields of isolated products. For the synthesis of 3a–j and 4a–j, see ref. 10b.
b Prepared from ethyl 2-oxo-2-(phenylamino)acetate and o-anisidine.
c Prepared from ethyl 2-oxo-2-(o-methoxyphenyl)acetate and aniline.
d Prepared from ethyl 2-oxo-2-(phenylamino)acetate and p-anisidine.
e Prepared from ethyl 2-oxo-2-(p-methoxyphenyl)acetate and aniline
Tol, lmax = 361–363 nm). A significant bathochromic ef- In conclusion, we have reported the synthesis of unsym-
fect (ca. 36 nm) was observed for derivatives 6d and 6n metrical pyrrolo[3,2-b]pyrrole-2,5-diones and
containing the electron-donating p-methoxyphenyl group bis(quinazolin-4-on-2-yls) by one-pot cyclisations of un-
[Ar3 = p-(MeO)C6H4, lmax = 383 nm]. As expected, the in- symmetrical oxaldi(arylimidoyl) dichlorides.
fluence of the aryl groups attached to the nitrogen atoms
was very low.
All solvents were dried by standard methods and all reactions were
carried out under an inert atmosphere using oven-dried (150 °C)
The synthesis of unsymmetrical bis(quinazolin-4-on-2-
glassware. Tetrahydrofuran was freshly distilled from sodium. The
yls) by reaction of bis(imidoyl) dichlorides with methyl 2-
1H and 13C NMR spectra (1H NMR: 200 MHz or 300 MHz, 13C
aminobenzoate (7) was next studied. The triethylamine-
NMR: 50 MHz or 75 MHz) were recorded in the indicated deuter-
mediated reaction of 7 with unsymmetrical bis(imidoyl)
dichlorides afforded the novel unsymmetrical
bis(quinazolin-4-on-2-yls) 8a–f (Scheme 2, Table 2). The
ated solvents. The multiplicities of the 13C NMR signals were deter-
mined with the DEPT 135 technique. Mass spectral data were
obtained using the electron ionisation (70 eV) or the chemical ioni-
formation of the latter can be explained by 2:1 condensa- sation technique (CI, H2O). For preparative-scale chromatography,
silica gel (Merck, 60–200 mesh) was used. Melting points were
measured on a Dr. Tottoli apparatus (Büchi) and are uncorrected.
Microanalyses were performed at the microanalytical laboratory of
the University of Greifswald.
tion of 7 with 4c to give an open-chain intermediate A and
subsequent cyclisation by attack of the nitrogen atoms
onto the ester groups.
Synthesis 2006, No. 15, 2507–2514 © Thieme Stuttgart · New York

PAPER
Synthesis of Unsymmetrical Pyrrolo[3,2-b]pyrrole-2,5-diones and Bis(quinazolin-4-on-2-yls)
2509
Ar1NH2
Table 2 Products and Yields
EtO
O
O
O
Cl
O
1
4
i
8
a
b
c
d
e
f
Ar1
Ar2
8 (%)a
NAr1
EtO
i
H
4-(MeO)C6H4
4-(MeO)C6H4
4-MeC6H4
3,5-Me2C6H3
4-MeC6H4
2,4-Me2C6H3
2,4-Me2C6H3
C6H5
18
54
74
22
79
21
2
f
Ar2NH3
ii
k
h
b
d
4-(MeO)C6H4
4-(MeO)C6H4
3,5-Me2C6H3
H
Ar2N
Cl
Cl
NAr1
iii
Ar2N
O
O
C6H5
NAr1
H
a Yields of isolated products.
4a–j
3a–j
O
Ar3
Synthesis of Unsymmetrical Pyrrolo[3,2-b]pyrrole-2,5-diones
(6); General Procedure
iv
2
OEt
5
A THF solution of LDA was prepared by addition of n-BuLi (5.15
mL, 7.92 mmol, solution in n-hexane) to a THF solution (6.1 mL)
of diisopropylamine (1.22 mL, 8.71 mmol) at 0 °C. After stirring for
30 min, a THF solution (33 mL) of the ester 5 (6.60 mmol) was add-
ed. The solution was stirred for 1 h at 0 °C. The mixture was cooled
to –78 °C and a THF solution (18 mL) of the oxalic acid bis(imi-
doyl) dichloride 4 (3.00 mmol) was slowly added. The solution was
warmed to 20 °C during 14 h and was stirred for 36 h at 20 °C. The
mixture was poured into an aqueous solution of NH4Cl (5 M, 300
mL). The addition of Et2O (200 mL) resulted in the formation of a
precipitate, which was washed with Et2O, dried in vacuo and recrys-
tallised from DMF. For some products, DMSO was used. The prod-
ucts 6 were obtained as orange solids. For compounds 6p,r,t the
peaks of some quaternary carbons were very small.
OEt
Ar1
N
Ar3
O
Ar3
NHAr2
Ar1HN
O
O
Ar3
N
O
Ar3
Ar2
EtO
6a–u
Scheme 1 Synthesis of unsymmetrical pyrrolo[3,2-b]pyrrole-2,5-
diones 6a–u. Reagents and conditions: i) Et3N, THF, 0 °C → 20 °C;
ii) toluene, reflux, 6–8 h; iii) PCl5, toluene, reflux, 1 h; iv) 1. LDA (2.3
equiv), THF; 2. 5 (2.6 equiv), 0 °C, 1 h; 3. 4 (1.0 equiv), 78 °C → 20
°C, 14 h, then 20 °C, 36 h.
1-(2-Methoxyphenyl)-3,4,6-triphenylpyrrolo[3,2-b]pyrrole-2,5-
dione (6a)
Starting
with
N-(o-methoxyphenyl)-N¢-phenyloxaldiimidoyl
dichloride (1.0 mmol) and ethyl phenylacetate (2.2 mmol), 6a
(54%) was isolated as an orange solid; mp 316 °C.
O
IR (KBr): 974 (m), 1169 (m), 1253 (m), 1415 (m), 1445 (m), 1513
(s), 1597 (m), 1654 (s), 1731 (s) cm–1.
1H NMR (200 MHz, CDCl3): d = 3.78 (s, 3 H, OCH3), 6.74 (t, J =
6.0 Hz, 1 H, Ar), 6.78 (t, J = 6.0 Hz, 1 H, Ar), 7.03–7.25 (m, 17 H,
Ar).
13C NMR (50 MHz, CDCl3): d = 55.5, 104.7, 104.9, 114.0, 126.0,
126.6, 127.3, 127.4, 127.6, 127.6, 128.0, 128.1, 128.7, 129.8, 133.6,
145.2, 145.7, 158.8, 170.6, 170.8.
OMe
NH2
O
N
2
Ar1
N
i
7
N
Ar1
N
Cl
N
N
Ar2
+
Cl
Ar2
O
MS (EI, 70 eV): m/z (%) = 471 (100) [M+], 472 (38), 222 (11), 89
(43).
8a–f
4b,d,f,h,i,k
UV–Vis (log e): lmax = 347 (4.28) nm.
Anal. Calcd for C31H22O3N2: C, 79.13; H, 4.71; N, 5.95. Found: C,
74.43; H, 4.96; N, 5.33.
Ar1
CO2Me
HN
N
1-(2-Methoxyphenyl)-4-phenyl-3,6-di-(p-tolyl)pyrrolo[3,2-
b]pyrrole-2,5-dione (6b)
N
NH
MeO2C
Starting
with
N-(o-methoxyphenyl)-N¢-phenyloxaldiimidoyl
Ar2
dichloride (1.0 mmol) and ethyl (4-methylphenyl)acetate (2.2
A
mmol), 6b (55%) was isolated as an orange solid; mp 320 °C.
Scheme 2 Synthesis of unsymmetrical bis(quinazolin-4-on-2-yls).
Reagents and conditions: i) Et3N (3.0 equiv), THF, 68 °C, 36 h.
IR (KBr): 975 (m), 1169 (m), 1252 (m), 1414 (m), 1513 (s), 1611
(m), 1646 (m), 1731 (s) cm–1.
1H NMR (200 MHz, CDCl3): d = 2.28 (s, 6 H, 2 × CH3), 3.79 (s, 3
H, OCH3), 6.77–7.24 (m, 17 H, Ar).
Synthesis 2006, No. 15, 2507–2514 © Thieme Stuttgart · New York

2510
F. Helmholz et al.
PAPER
13C NMR (50 MHz, CDCl3): d = 21.3, 21.3, 55.5, 105.0, 114.0,
125.2, 125.2, 126.0, 126.8, 127.2, 127.4, 128.3, 128.3, 128.6, 129.3,
133.8, 137.96, 138.03, 144.6, 158.7, 170.7, 171.0.
MS (EI, 70 eV): m/z (%) = 498 (100) [M+], 499 (37), 469 (6), 103
(16).
1-(2,4-Dimethylphenyl)-3,4,6-triphenylpyrrolo[3,2-b]pyrrole-
2,5-dione (6f)
Starting with 4c (3 mmol) and ethyl phenylacetate (6.6 mmol), 6f
(28%) was isolated as an orange solid; mp 265–266 °C.
IR (KBr): 695 (m), 1412 (m), 1501 (m), 1654 (m), 1734 (m) cm–1.
UV–Vis (log e): lmax = 361 (4.31) nm.
1H NMR (200 MHz, CDCl3): d = 2.11 (s, 3 H, CH3), 2.32 (s, 3 H,
CH3), 6.93–7.24 (m, 18 H, Ar).
Anal. Calcd for C33H26O3N2: C, 79.50; H, 5.26; N, 5.62. Found: C,
79.17; H, 5.47; N, 5.68.
13C NMR (50 MHz, CDCl3): d = 17.9, 21.1, 104.96, 105.02, 126.0,
127.29, 127.32, 127.5, 127.8, 127.9, 128.1, 128.6, 129.2, 129.9,
130.7, 131.6, 133.7, 136.1, 138.9, 144.9, 146.4, 170.5, 170.6.
MS (EI, 70 eV): m/z (%) = 468 (100) [M+], 439 (52), 219 (15), 89
(31), 28 (21).
1-(4-Methoxyphenyl)-3,4,6-triphenylpyrrolo[3,2-b]pyrrole-2,5-
dione (6c)
Starting with 4b (2.0 mmol) and ethyl phenylacetate (4.4 mmol), 6c
(35%) was isolated as an orange solid; mp 271 °C.
UV–Vis (log e): lmax = 349 (4.27), 264 (4.16) nm.
IR (KBr): 975 (m), 1169 (m), 1178 (m), 1254 (m), 1415 (m), 1513
(s), 1649 (s), 1727 (s), 3437 (s) cm–1.
1H NMR (200 MHz, DMSO-d6): d = 3.75 (s, 3 H, OCH3), 6.86 (d,
J = 6.0 Hz, 2 H, Ar), 7.07–7.30 (m, 17 H, Ar).
1-(2,4-Dimethylphenyl)-4-phenyl-3,6-di(p-tolyl)pyrrolo[3,2-
b]pyrrole-2,5-dione (6g)
Starting with 4c (3.0 mmol) and ethyl (4-methylphenyl)acetate (6.6
mmol), 6g (33%) was isolated as an orange solid; mp. 277–278 °C.
13C NMR (50 MHz, CDCl3): d = 55.5, 104.7, 104.9, 114.0, 126.0,
126.6, 127.3, 127.4, 127.57, 127.61, 128.0, 128.1, 128.7, 129.8,
133.6, 145.2, 145.7, 158.8, 170.6, 170.8.
IR (KBr): 1176 (m), 1265 (m), 1410 (m), 1511 (m), 1649 (m), 1733
(m) cm–1.
MS (EI, 70 eV): m/z (%) = 470 (100) [M+], 455 (7), 222 (11), 89
(41).
1H NMR (200 MHz, CDCl3): d = 2.11 (s, 3 H, CH3), 2.24 (s, 3 H,
CH3), 2.27 (s, 3 H, CH3), 2.33 (s, 3 H, CH3), 6.83–7.03 (m, 13 H,
Ar), 7.13–7.16 (m, 3 H, Ar).
13C NMR (50 MHz, CDCl3): d = 17.9, 21.1, 21.30, 21.32, 105.0,
105.1, 125.1, 125.3, 126.0, 127.2, 127.3, 127.9, 128.3, 128.6, 128.6,
129.1, 129.7, 130.9, 131.6, 133.8, 136.1, 137.8, 138.1, 138.7, 144.3,
145.8, 170.7, 170.8.
UV–Vis (log e): lmax = 347 (4.34) nm.
Anal. Calcd for C31H22O3N2: C, 79.13; H, 4.71; N, 5.95. Found: C,
76.73; H, 5.42; N, 5.85.
1,3,6-Tris(4-methoxyphenyl)-4-phenylpyrrolo[3,2-b]pyrrole-
2,5-dione (6d)
MS (EI, 70 eV): m/z (%) = 496 (100) [M+], 468 (32), 467 (35), 233
Starting with 4b (2.0 mmol) and ethyl (4-methoxyphenyl)acetate
(4.4 mmol), 6d (30%) was isolated as an orange solid; mp 281 °C.
(10), 102 (20), 28 (38).
UV–Vis (log e): lmax = 363 (4.26), 264 (4.19) nm.
IR (KBr): 978 (m), 1031 (m), 1173 (s), 1251 (s), 1298 (m), 1411
(m), 1441 (m), 1514 (s), 1605 (s), 1648 (s), 1724 (s), 3438 (m) cm–1.
1H NMR (200 MHz, DMSO-d6): d = 3.70 (s, 3 H, OCH3), 3.71 (s, 3
H, OCH3), 3.76 (s, 3 H, OCH3), 6.66–6.71 (m, 4 H, Ar), 6.90–7.15
(m, 10 H, Ar), 7.30–7.32 (m, 3 H, Ar).
1-(3,5-Dimethylphenyl)-3,4,6-triphenylpyrrolo[3,2-b]pyrrole-
2,5-dione (6h)
Starting with 4d (3.0 mmol) and ethyl phenylacetate (6.6 mmol), 6h
(25%) was isolated as an orange solid; mp 287–288 °C.
IR (KBr): 1733 (s), 1652 (s), 1597 (m), 1497 (m), 1407 (m), 773
(m), 694 (m) cm–1.
1H NMR (200 MHz, CDCl3): d = 2.11 (s, 6 H, 2 × CH3), 7.09–7.25
(m, 18 H, Ar).
13C NMR (50 MHz, CDCl3): d = 21.0, 105.0, 105.1, 123.7, 126.0,
127.3, 127.4, 127.5, 128.1, 128.2, 128.67, 128.73, 129.8, 130.0,
133.1, 133.6, 138.3, 145.2, 145.5, 170.4, 170.6.
13C NMR (50 MHz, DMSO-d6): d = 55.2, 55.5, 55.6, 104.6, 104.8,
113.1, 113.2, 114.0, 120.6, 120.7, 125.9, 126.8, 127.2, 127.3, 128.7,
131.2, 133.8, 143.8, 144.4, 158.7, 159.4, 170.8, 171.1.
MS (EI, 70 eV): m/z (%) = 530 (100) [M+], 515 (8), 222 (9), 119
(18).
UV–Vis (log e): lmax = 383 (4.32), 264 (4.43) nm.
1-(4-Methoxyphenyl)-4-phenyl-3,6-di(p-tolyl)pyrrolo[3,2-
b]pyrrole-2,5-dione (6e)
MS (EI, 70 eV): m/z (%) = 468 (100) [M+], 440 (16), 219 (12), 89
(34).
Starting with 4b (2.0 mmol) and ethyl (4-methylphenyl)acetate (4.4
mmol), 6e (21%) was isolated as an orange solid; mp 286 °C.
UV–Vis (log e): lmax = 347 (4.33), 264 (4.19) nm.
Anal. Calcd for C32H24O2N2: C, 82.03; H, 5.16; N, 5.98. Found: C,
81.95; H, 5.48; N, 6.12.
IR (KBr): 976 (m), 1109 (m), 1251 (m), 1414 (m), 1513 (s), 1612
(m), 1650 (s), 1733 (s), 3438 (m) cm–1.
1H NMR (200 MHz, DMSO-d6): d = 2.22 (s, 3 H, CH3), 2.24 (s, 3
H, CH3), 3.75 (s, 3 H, OCH3), 6.86–7.01 (m, 10 H, Ar), 7.12–7.21
(m, 4 H, Ar), 7.31 (t, J = 3.3 Hz, 3 H, Ar).
1-(3,5-Dimethylphenyl)-4-phenyl-3,6-di(p-tolyl)pyrrolo[3,2-
b]pyrrole-2,5-dione (6i)
Starting with 4d (3.0 mmol) and ethyl (4-methylphenyl)acetate (6.6
mmol), 6i (32%) was isolated as an orange solid; mp 250–251 °C.
IR (KBr): 1730 (s), 1647 (s), 1611 (m), 1512 (m), 1407 (m) cm–1.
1H NMR (200 MHz, CDCl3): d = 2.11 (s, 6 H, 2 × CH3), 2.27 (s, 3
H, CH3), 2.29 (s, 3 H, CH3), 6.84–7.15 (m, 16 H, Ar).
13C NMR (50 MHz, DMSO-d6): d = 21.3, 21.4, 105.0, 114.0,
125.16, 125.21, 126.0, 126.8, 127.2, 127.4, 128.27, 128.34, 128.6,
129.7, 133.8, 138.0, 138.1, 144.6, 158.7, 170.7, 171.0.
MS (EI, 70 eV): m/z (%) = 498 (100) [M+], 483 (5), 236 (7), 206 (6),
102 (23).
13C NMR (50 MHz, CDCl3): d = 21.0, 21.2, 21.3, 105.1, 105.2,
123.6, 125.2, 125.4, 126.0, 127.2, 128.1, 128.3, 128.6, 129.7, 129.9,
133.2, 133.8, 138.0, 138.2, 144.5, 170.6, 170.8.
UV–Vis (log e): lmax = 361 (4.33), 264 (4.31) nm.
MS (EI, 70 eV): m/z (%) = 496 (100) [M+], 467 (12), 102 (23).
Synthesis 2006, No. 15, 2507–2514 © Thieme Stuttgart · New York

PAPER
Synthesis of Unsymmetrical Pyrrolo[3,2-b]pyrrole-2,5-diones and Bis(quinazolin-4-on-2-yls)
2511
UV–Vis (log e): lmax = 361 (4.34), 264 (4.35) nm.
IR (KBr): 977 (m), 1168 (m), 1252 (m), 1301 (w), 1415 (m), 1514
(s), 1612 (m), 1653 (s), 1735 (s), 3437 (m) cm–1.
Anal. Calcd for C34H28O2N2: C, 82.23; H, 5.68; N, 5.64. Found: C,
82.44; H, 5.86; N, 5.69.
1H NMR (200 MHz, CDCl3): d = 2.27 (s, 6 H, 2 × CH3), 2.33 (s, 3
H, CH3), 3.79 (s, 3 H, OCH3), 6.77–7.09 (m, 16 H, Ar).
1-(Naphthalen-1-yl)-3,4,6-triphenylpyrrolo[3,2-b]pyrrole-2,5-
dione (6j)
Starting with 4e (3.0 mmol) and ethyl phenylacetate (6.6 mmol), 6j
(46%) was isolated as an orange solid; mp 274–275 °C.
13C NMR (50 MHz, CDCl3): d = 21.1, 21.3, 55.6, 104.7, 104.8,
114.0, 125.2, 125.3, 125.9, 126.8, 127.4, 128.2, 128.3, 129.2, 129.7,
129.8, 131.3, 137.2, 138.0, 144.8, 145.1, 158.7, 170.9, 171.1.
MS (EI, 70 eV): m/z (%) = 512 (100) [M+], 528 (14), 497 (11), 496
(10), 236 (10), 102 (36).
IR (KBr): 970 (m), 1168 (m), 1270 (m), 1416 (s), 1497 (m), 1596
(m), 1655 (s), 1732 (s) cm–1.
1H NMR (200 MHz, CDCl3): d = 6.76–7.50 (m, 19 H, Ar), 7.84–
7.89 (m, 3 H, Ar).
13C NMR (50 MHz, CDCl3): d = 19.4, 47.6, 105.2, 105.4, 122.9,
125.0, 125.8, 126.1, 126.5, 127.0, 127.3, 127.4, 127.6, 127.8, 128.0,
128.2, 128.3, 128.7, 129.0, 129.2, 129.8, 129.9, 130.6, 130.9, 133.7,
134.2, 145.3, 146.7, 170.5, 170.8.
MS (EI, 70 eV): m/z (%) = 491 (100) [M + H]+, 242 (11), 241 (11),
192 (10), 89 (49).
UV–Vis (log e): lmax = 361 (4.33) nm.
1,3,6-Tris(4-methoxyphenyl)-4-p-tolylpyrrolo[3,2-b]pyrrole-
2,5-dione (6n)
Starting with 4f (3.0 mmol) and ethyl (4-methoxyphenyl)acetate
(6.6 mmol), 6n (32%) was isolated as an orange solid; mp 299 °C.
IR (KBr): 977 (m), 1033 (m), 1110 (w), 1172 (s), 1251 (s), 1298 (s),
1409 (s), 1442 (m), 1514 (s), 1606 (s), 1651 (s), 1730 (s), 3147 (m),
3436 (m) cm–1.
UV–Vis (log e): lmax = 349 (4.32), 294 (4.08) nm.
1H NMR (200 MHz, CDCl3): d = 2.33 (s, 3 H, CH3), 3.74 (s, 6 H, 2
× OCH3), 3.79 (s, 3 H, OCH3), 6.62–6.66 (m, 4 H, Ar), 6.78–6.81
(m, 2 H, Ar), 7.00–7.10 (m, 10 H, Ar).
13C NMR (50 MHz, CDCl3): d = 21.1, 55.2, 55.5, 68.0, 104.5, 104.6,
113.1, 113.1, 114.0, 120.7, 120.8, 125.8, 126.8, 127.3, 129.3, 131.2,
131.3, 137.2, 144.1, 144.2, 155.3, 158.7, 159.4, 171.0, 171.2.
1-(Naphthalen-1-yl)-4-phenyl-3,6-di(p-tolyl)pyrrolo[3,2-b]pyr-
role-2,5-dione (6k)
Starting with 4e (3.0 mmol) and ethyl (4-methylphenyl)acetate (6.6
mmol), 6k (31%) was isolated as an orange solid; mp 346–347 °C.
IR (KBr): 972 (m), 1168 (m), 1183 (m), 1269 (m), 1413 (s), 1512
(s), 1611 (m), 1649 (s), 1732 (s) cm–1.
1H NMR (200 MHz, CDCl3): d = 2.11 (s, 3 H, CH3), 2.28 (s, 3 H,
CH3), 6.60 (d, J = 7.0 Hz, 2 H, Ar), 6.72 (d, J = 7.0 Hz, 2 H, Ar),
6.92 (d, J = 7.0 Hz, 2 H, Ar), 7.06 (d, J = 6.0 Hz, 2 H, Ar), 7.18–
7.34 (m, 7 H, Ar), 7.46–7.49 (m, 2 H, Ar), 7.84–7.92 (m, 3 H, Ar).
13C NMR (50 MHz, CDCl3): d = 21.1, 21.4, 105.3, 105.4, 123.0,
124.8, 125.1, 125.2, 125.8, 126.1, 126.5, 126.9, 127.3, 128.0, 128.2,
128.3, 128.7, 128.9, 129.1, 129.8, 130.7, 131.1, 133.8, 134.2, 137.8,
138.2, 144.7, 146.1, 170.7, 171.0.
MS (EI, 70 eV): m/z (%) = 544 (100) [M+], 560 (14), 528 (13), 252
(5), 119 (16).
UV–Vis (log e): lmax = 383 (4.31) nm.
1-(3,5-Dimethylphenyl)-3,6-diphenyl-4-(p-tolyl)pyrrolo[3,2-
b]pyrrole-2,5-dione (6o)
Starting with 4g (3.0 mmol) and ethyl phenylacetate (6.6 mmol), 6o
(28%) was isolated as an orange solid; mp 301–302 °C.
IR (KBr): 974 (m), 1166 (m), 1208 (m), 1260 (m), 1414 (m), 1494
(m), 1515 (m), 1598 (m), 1652 (s), 1733 (s) cm–1.
1H NMR (200 MHz, CDCl3): d = 2.11 (s, 3 H, CH3), 2.17 (s, 3 H,
CH3), 2.32 (s, 3 H, CH3), 6.70–7.30 (m, 17 H, Ar).
MS (EI, 70 eV): m/z (%) = 519 (100) [M + H]+, 520 (42), 206 (6),
103 (17).
UV–Vis (log e): lmax = 362 (4.35) nm.
13C NMR (50 MHz, CDCl3): d = 21.1, 105.0, 123.7, 125.9, 127.4,
127.5, 128.0, 128.1, 128.3, 129.3, 129.9, 130.0, 131.1, 133.1, 136.6,
137.3, 138.3, 145.4, 170.7.
Anal. Calcd for C36H26O2N2: C, 83.38; H, 5.05; N, 5.40. Found: C,
83.42; H, 5.42; N, 5.10.
MS (EI, 70 eV): m/z (%) = 483 (100) [M + H]+, 89 (41).
1-(4-Methoxyphenyl)-3,6-diphenyl-4-(p-tolyl)pyrrolo[3,2-
b]pyrrole-2,5-dione (6l)
UV–Vis (log e): lmax = 346 (4.31) nm.
Starting with 4f (3.0 mmol) and ethyl phenylacetate (6.6 mmol), 6l
(32%) was isolated as an orange solid; mp 315 °C.
1-(3,5-Dimethylphenyl)-3,4,6-tri(p-tolyl)pyrrolo[3,2-b]pyrrole-
2,5-dione (6p)
Starting with 4g (3.0 mmol) and ethyl (4-methylphenyl)acetate (6.6
IR (KBr): 976 (m), 1169 (m), 1254 (s), 1301 (m), 1417 (m), 1446
(m), 1513 (s), 1644 (s), 1727 (s), 3438 (m) cm–1.
1H NMR (200 MHz, CDCl3): d = 2.33 (s, 3 H, CH3), 3.79 (s, 3 H,
OCH3), 6.76–6.79 (d, J = 7.0 Hz, 2 H, Ar), 7.01–7.26 (m, 16 H, Ar).
13C NMR (50 MHz, CDCl3): d = 21.1, 55.5, 104.66, 104.73, 114.0,
125.9, 126.6, 127.4, 127.5, 127.6, 128.0, 128.1, 129.2, 129.8, 129.9,
131.1, 137.3, 145.3, 145.7, 158.8, 170.7, 170.8, 206.9.
mmol), 6p (26%) was isolated as an orange solid; mp 308–309 °C.
IR (KBr): 3131 (m), 1733 (s), 1651 (s), 1611 (m), 1515 (m), 1403
(s), 1260 (w), 1166 (w), 815 (m) cm–1.
1H NMR (200 MHz, CDCl3): d = 2.11 (s, 3 H, CH3), 2.17 (s, 3 H,
CH3), 2.28 (s, 6 H, 2 × CH3), 2.33 (s, 3 H, CH3), 6.70 (s, 1 H, Ar),
6.82–7.08 (m, 14 H, Ar).
13C NMR (50 MHz, CDCl3): d = 20.5, 21.0, 21.1, 21.2, 21.3, 104.9,
105.1, 123.6, 125.3, 125.5, 125.9, 128.0, 128.2, 128.6, 129.2, 129.8,
129.9, 130.0, 131.0, 136.5, 137.2, 137.9, 138.2.
MS (EI, 70 eV): m/z (%) = 484 (100) [M+], 500 (3), 221 (s), 205 (4),
89 (24).
UV-Vis (log e): lmax = 347 (4.32) nm.
MS (EI, 70 eV): m/z (%) = 511 (27) [M +H]+, 103 (8), 32 (23).
1-(4-Methoxyphenyl)-3,4,6-tri(p-tolyl)pyrrolo[3,2-b]pyrrole-
2,5-dione (6m)
UV–Vis (log e): lmax = 361 (4.22), 264 (4.25) nm.
Starting with 4f (3.0 mmol) and ethyl (4-methylphenyl)acetate (6.6
mmol), 6m (30%) was isolated as an orange solid; mp 344 °C.
Synthesis 2006, No. 15, 2507–2514 © Thieme Stuttgart · New York

2512
F. Helmholz et al.
PAPER
1-(2,4-Dimethylphenyl)-4-(4-methoxyphenyl)-3,6-diphenylpyr-
rolo[3,2-b]pyrrole-2,5-dione (6q)
MS (EI, 70 eV): m/z (%) = 526 (100) [M+], 102 (14), 32 (11), 28
(44).
Starting with 4h (3.0 mmol) and ethyl phenylacetate (6.6 mmol), 6q
(38%) was isolated as an orange solid; mp 288–289 °C.
UV–Vis (log e): lmax = 346 (4.34) nm.
IR (KBr): 975 (m), 1179 (m), 1253 (m), 1299 (m), 1416 (m), 1444
(w), 1512 (s), 1654 (s), 1732 (s) cm–1.
1-(4-Methoxyphenyl)-4-(4-nitrophenyl)-3,6-di(p-tolyl)pyrro-
lo[3,2-b]pyrrole-2,5-dione (6u)
Starting with 4j (2.0 mmol) and ethyl (4-methylphenyl)acetate (4.4
mmol), 6u (10%) was isolated as an orange solid; mp 297–298 °C.
1H NMR (200 MHz, CDCl3): d = 2.11 (s, 3 H, CH3), 2.31 (s, 3 H,
CH3), 3.78 (s, 3 H, OCH3), 6.77–7.15 (m, 17 H, Ar).
IR (KBr): 977 (w), 1172 (m), 1249 (m), 1301 (m), 1343 (m), 1411
(m), 1513 (s), 1610 (m), 1640 (m), 1734 (m) cm–1.
1H NMR (200 MHz, CDCl3): d = 2.27 (s, 3 H, CH3), 2.31 (s, 3 H,
CH3), 3.79 (s, 3 H, OCH3), 6.77–7.08 (m, 12 H, Ar), 7.28 (d, J = 7.0
Hz, 2 H, Ar), 8.10 (d, J = 7.0 Hz, 2 H, Ar).
13C NMR (50 MHz, CDCl3): d = 21.3, 21.4, 55.6, 105.1, 106.4,
114.0, 114.1, 124.0, 124.6, 124.9, 125.5, 126.4, 127.5, 128.3, 128.5,
128.7, 129.7, 129.9, 138.5, 139.0, 139.2, 142.7, 145.5, 145.7, 158.9,
170.1, 170.3.
13C NMR (50 MHz, CDCl3): d = 17.9, 21.1, 55.5, 104.7, 104.9,
114.0, 126.6, 126.7, 127.3, 127.4, 127.5, 127.6, 127.8, 128.0,
128.06, 128.10, 129.2, 129.8, 130.8, 131.6, 136.1, 138.8, 145.4,
146.3, 158.7, 170.6, 170.8.
MS (EI, 70 eV): m/z (%) = 498 (100) [M+], 500 (100), 472 (15), 222
(23), 89 (40).
UV–Vis (log e): lmax = 347 (4.35) nm.
1-(2,4-Dimethylphenyl)-4-(4-methoxyphenyl)-3,6-di(p-
tolyl)pyrrolo[3,2-b]pyrrole-2,5-dione (6r)
MS (EI, 70 eV): m/z (%) = 544 (100) [M + H]+, 529 (15), 514 (38),
Starting with 4h (3.0 mmol) and ethyl (4-methylphenyl)acetate (6.6
103 (16), 28 (49).
mmol), 6r (42%) was isolated as an orange solid; mp 315–316 °C.
UV–Vis (log e): lmax = 357 (4.37) nm.
IR (KBr): 977 (m), 1032 (w), 1177 (m), 1252 (s), 1299 (m, 1416
(m), 1513 (s), 1611 (m), 1653 (s), 1733 (s) cm–1.
1H NMR (200 MHz, CDCl3): d = 2.11 (s, 3 H, CH3), 2.24 (s, 3 H,
CH3), 2.27 (s, 3 H, CH3), 2.32 (s, 3 H, CH3), 3.79 (s, 3 H, OCH3),
6.77–7.10 (m, 15 H, Ar).
13C NMR (50 MHz, CDCl3): d = 17.9, 21.1, 21.3, 21.3, 55.6, 104.8,
104.9, 113.9, 125.2, 125.3, 126.9, 127.3, 127.4, 127.9, 128.27,
128.32, 129.1, 129.7, 131.0, 131.5, 136.2, 137.7, 137.9, 138.7,
144.8, 145.7, 158.6, 170.8, 171.0.
Synthesis of Bis(quinazolin-4-on-2-yls) 8a–f; General Proce-
dure
A toluene solution (10 mL) of the oxaldiimidoyl dichloride (1.0
mmol), 2-aminobenzoate (2.0 mmol) and of Et3N (2.0 mmol) was
stirred under reflux until the oxaldiimidoyl dichloride could not be
detected anymore by TLC (ca. 72 h). The precipitated Et3NHCl was
filtered off and washed with hot toluene. The filtrate was concen-
trated in vacuo. Addition of MeOH to the residue resulted in precip-
itation of a solid. The latter was separated and washed with a small
amount of MeOH to give a greyish-white solid.
MS (EI, 70 eV): m/z (%) = 526 (100) [M+], 497 (23), 235 (5), 102
(10), 28 (22).
N-(4-Methoxyphenyl)-N¢-(3,5-dimethylphenyl)bis(quinazolin-
4-on-2-yl) (8a)
UV–Vis (log e): lmax = 361 (4.33) nm.
Starting with N-(4-methoxyphenyl)-N¢-(3,5-dimethylphenyl)oxal-
diimidoyl dichloride (0.335 g, 1.0 mmol) and methyl 2-aminoben-
zoate (0.302 g, 2.0 mmol), 8a (0.03 g, 18%) was isolated as a
colourless solid; mp 240–241 °C.
1-(3,5-Dimethylphenyl)-4-(4-methoxyphenyl)-3,6-diphenylpyr-
rolo[3,2-b]pyrrole-2,5-dione (6s)
Starting with 4i (3.0 mmol) and ethyl phenylacetate (6.6 mmol), 6s
(35%) was isolated as an orange solid; mp 267–268 °C.
IR (KBr): 695 (m), 776 (m), 1180 (m), 1249 (m), 1292 (m), 1333
(m), 1378 (m), 1468 (m), 1510 (m), 1562 (m), 1578 (m), 1609 (m),
1694 (s) cm–1.
1H NMR (300 MHz, CDCl3): d = 2.20 (s, 6 H, 2 × CH3), 3.77 (s, 3
H, OCH3), 6.77–7.16 (m, 7 H, Ar), 7.50–7.58 (m, 2 H, Hetar), 7.76–
7.84 (m, 4 H, Hetar), 8.24 (t, 2 H, Hetar).
13C NMR (75 MHz, CDCl3): d = 20.9 (2 × CH3), 55.4 (OCH3),
113.7, 121.6, 121.8, 126.9, 127.2, 127.3, 127.6, 127.8, 128.2, 130.9,
131.2, 134.1, 134.8, 138.3, 146.3, 146.4, 147.9, 148.0, 160.0 (Ar,
Hetar), 161.2, 161.4 (C=O, NCN).
IR (KBr): 973 (m), 1031 (m), 1162 (m), 1208 (m), 1252 (s), 1301
(m), 1444 (m), 1513 (s), 1653 (s), 1731 (s) cm–1.
1H NMR (200 MHz, CDCl3): d = 2.11 (s, 6 H, 2 × CH3), 3.78 (s, 3
H, OCH3), 6.71–6.84 (m, 4 H, Ar), 7.03–7.21 (m, 13 H, Ar).
13C NMR (50 MHz, CDCl3): d = 21.0, 55.5, 105.0, 114.0, 123.6,
127.4, 127.6, 128.0, 128.3, 128.7, 129.8, 130.0, 133.1, 138.3, 158.8.
MS (EI, 70 eV): m/z (%) = 498 (100) [M+], 220 (4), 89 (27), 28 (9).
UV–Vis (log e): lmax = 345 (4.32) nm.
MS (EI, 70 eV): m/z (%) = 499 (100) [M+], 500 (29), 243 (30), 216
(26), 86 (37).
1-(3,5-Dimethylphenyl)-4-(4-methoxyphenyl)-3,6-di(p-
tolyl)pyrrolo[3,2-b]pyrrole-2,5-dione (6t)
Starting with 4i (3.0 mmol) and ethyl (4-methylphenyl)acetate (6.6
mmol), 6t (27%) was isolated as an orange solid.
UV–Vis (log e) = 305 (4.12), 284 (4.24), 276 (4.23), 224 (4.77), 206
(4.81), 203 (4.81) nm.
IR (KBr): 800 (m), 821 (m), 976 (m), 1034 (m), 1164 (m), 1181 (m),
1252 (s), 1301 (m) 1407 (m), 1514 (s), 1610 (m), 1652 (s), 1732 (s)
cm–1.
N-(4-Tolyl)-N¢-(4-methoxyphenyl)bis(quinazolin-4-on-2-yl)
(8b)
Starting with N-(4-tolyl)-N¢-(4-methoxyphenyl)oxaldiimidoyl
dichloride (0.321 g, 1.0 mmol) and methyl 2-aminobenzoate (0.302
g, 2.0 mmol), 8b was isolated (0.26 g, 54%) as a colourless solid;
mp 269 °C.
1H NMR (200 MHz, CDCl3): d = 2.11 (s, 6 H, 2 × CH3), 2.28 (s, 3
H, CH3), 2.30 (s, 3 H, CH3), 3.79 (s, 3 H, OCH3), 6.70–7.07 (m, 15
H, Ar).
13C NMR (50 MHz, CDCl3): d = 20.5, 21.0, 21.2, 21.3, 55.6, 105.0,
105.1, 114.0, 123.6, 125.2, 125.46, 125.51, 126.8, 127.4, 128.0,
128.2, 128.3, 128.6, 129.7, 129.9, 130.0, 133.2, 138.0, 138.2, 158.7,
170.7, 171.1.
IR (KBr): 696 (w), 775 (m), 829 (w), 1026 (w), 1176 (w), 1195 (m),
1254 (s), 1303 (m), 1332 (m), 1378 (m), 1468 (m), 1511 (s), 1563
(m), 1588 (m), 1608 (m), 1691 (s) cm–1.
Synthesis 2006, No. 15, 2507–2514 © Thieme Stuttgart · New York

PAPER
Synthesis of Unsymmetrical Pyrrolo[3,2-b]pyrrole-2,5-diones and Bis(quinazolin-4-on-2-yls)
2513
1H NMR (300 MHz, CDCl3): d = 2.31 (s, 3 H, CH3), 3.77 (s, 3 H,
OCH3), 6.79–7.16 (m, 8 H, Ar), 7.50–7.56 (m, 2 H, Hetar), 7.78–
7.82 (m, 4 H, Hetar), 8.22–8.27 (m, 2 H, Hetar).
IR (KBr): 695 (m), 753 (w), 775 (m), 829 (w), 1026 (m), 1174 (m),
1195 (m), 1254 (s), 1301 (m), 1331 (m), 1376 (m), 1468 (m), 1511
(s), 1563 (m), 1588 (m), 1607 (m), 1691 (s) cm–1.
13C NMR (75 MHz, CDCl3): d = 21.2 (CH3), 55.4 (OCH3), 113.8,
121.7, 126.9, 127.16, 127.22, 127.85, 127.89, 128.2, 129.4, 130.9,
131.8, 134.8, 139.8, 146.4, 147.9, 148.0, 160.0 (Ar, Hetar), 161.2,
161.4 (C=O, NCN).
1H NMR (300 MHz, CDCl3): d = 3.77 (s, 3 H, OCH3), 6.81–7.37 (m,
9 H, Ar), 7.49–7.58 (m, 2 H, Hetar), 7.77–7.82 (m, 4 H, Hetar),
8.20–8.27 (m, 2 H, Hetar).
13C NMR (75 MHz, CDCl3): d = 55.4 (OCH3), 113.9, 121.6, 121.7,
126.9, 127.20, 127.23, 127.8, 127.9, 128.24, 128.29, 128.35, 128.7,
129.6, 129.7, 130.8, 134.6, 134.8, 134.9, 146.3, 146.4, 147.7, 147.9,
160.0 (Ar, Hetar), 161.1, 161.9 (C=O, NCN).
MS (EI, 70 eV): m/z (%) = 486 (15) [M+], 91 (42), 90 (64).
UV–Vis (log e) = 284 (4.26), 226 (4.76), 203 (4.79) nm.
Anal. Calcd for C30H22N4O3 (486.53): C, 74.06; H, 4.56; N, 11.52.
Found: C, 73.95; H, 4.78; N, 10.92.
MS (EI, 70 eV): m/z (%) = 472 (100) [M+], 224 (27), 195 (30), 77
(38).
N-(4-Tolyl)-N¢-(2,4-dimethylphenyl)bis(quinazolin-4-on-2-yl)
(8c)
Anal. Calcd for C29H20N4O3 (472.50): C, 73.71; H, 4.26; N, 11.86.
Found: C, 73.23; H, 4.39; N, 11.38.
Starting with N-(4-tolyl)-N¢-(2,4-dimethylphenyl)oxaldiimidoyl
dichloride (0.321 g, 1.0 mmol) and methyl 2-aminobenzoate (0.302
g, 2.0 mmol), 8c (0.36 g, 74%) was isolated as a colourless solid;
mp 262 °C.
N-Phenyl-N¢-(3,5-dimethylphenyl)bis(quinazolin-4-on-2-yl) (8f)
Starting with N-phenyl-N¢-(3,5-dimethylphenyl)oxaldiimidoyl
dichloride (3.05 g, 10.0 mmol) and methyl 2-aminobenzoate (3.02
g, 20.0 mmol), 8f was isolated (1.00 g, 21%) as a colourless solid;
mp 234 °C.
IR (KBr): 697 (m), 778 (m), 817 (m), 1198 (m), 1259 (m), 1289(m),
1310 (m), 1333 (m), 1380 (m), 1469 (m), 1510 (m), 1563 (m), 1586
(s), 1607 (m), 1698 (s) cm–1.
1H NMR (300 MHz, CDCl3): d = 2.08 (s, 3 H, CH3), 2.26 (s, 3 H,
CH3), 2.32 (s, 3 H, CH3), 6.86–7.26 (m, 7 H, Ar), 7.47–7.56 (m, 2
H, Hetar), 7.64–7.78 (m, 4 H, Hetar), 8.21–8.29 (m, 2 H, Hetar).
13C NMR (75 MHz, CDCl3): d = 18.3 (CH3), 21.1 (CH3), 21.2
(CH3), 119.7, 121.6, 121.7, 125.3, 127.05, 127.15, 127.2, 127.7,
127.8, 128.0, 128.1, 128.2, 128.3, 129.0, 129.35, 129.40, 129.7,
131.8, 132.1, 132.2, 134.69, 134.74, 137.4, 139.5, 139.9, 146.3,
146.5, 147.4, 147.8 (Ar, Hetar), 160.9, 161.6 (C=O, NCN).
IR (KBr): 694 (m), 775 (m), 1184 (w), 1243 (w), 1264 (m), 1289
(m), 1332 (m), 1376 (m), 1469 (m), 1562 (m), 1586 (m), 1693 (s)
cm–1.
1H NMR (300 MHz, CDCl3): d = 2.17 (s, 3 H, CH3), 2.20 (s, 3 H,
CH3), 6.76–7.36 (m, 8 H, Ar), 7.50–7.57 (m, 2 H, Hetar), 7.77–7.82
(m, 4 H, Hetar), 8.21–8.27 (m, 2 H, Hetar).
13C NMR (75 MHz, CDCl3): d = 21.0 (2 × CH3), 121.6, 121.7,
127.2, 127.3, 127.6, 127.8, 128.22, 128.25, 128.5, 129.5, 129.6,
129.7, 131.2, 134.1, 134.6, 134.8, 134.9, 138.3, 146.3, 147.6, 147.7
(Ar, Hetar), 161.19, 161.21 (C=O, NCN).
MS (EI, 70 eV): m/z (%) = 484 (19) [M+], 282 (48), 121 (31), 107
(100).
MS (EI, 70 eV): m/z (%) = 470 (100) [M+], 420 (95), 387 (42), 268
(27), 77 (37).
UV–Vis (log e) = 304 (4.15), 287 (4.20), 207 (4.80), 204 (4.80) nm.
Anal. Calcd for C30H22N4O2 (470.53): C, 76.58; H, 4.71; N, 11.91.
Found: C, 76.15; H, 4.55; N, 11.67.
Anal. Calcd for C31H24N4O2 (484.56): C, 76.77; H, 4.99; N, 11.56.
Found: C, 76.61; H, 5.03; N, 11.24.
N-(4-Methoxyphenyl)-N¢-(2,4-dimethylphenyl)bis(quinazolin-
4-on-2-yl) (8d)
Acknowledgment
Starting with N-(4-methoxyphenyl)-N¢-(2,4-dimethylphenyl)oxal-
diimidoyl dichloride (0.335 g, 1.0 mmol) and methyl 2-aminoben-
zoate (0.302 g, 2.0 mmol), 8d was isolated (0.11 g, 22%) as a
colourless solid; mp 297 °C.
Financial support by the Deutsche Forschungsgemeinschaft is gra-
tefully acknowledged.
References
IR (KBr): 617 (w), 697 (w), 777 (w), 828 (m), 1033 (w), 1110 (w),
1172 (w), 1197 (m), 1256 (s), 1306 (m), 1332 (m), 1380 (m), 1468
(m), 1509 (s), 1563 (m), 1586 (m), 1609 (m), 1690 (m) cm–1.
1H NMR (300 MHz, CDCl3): d = 2.10 (s, 3 H, CH3), 2.26 (s, 3 H,
CH3), 3.77 (s, 3 H, OCH3), 6.80–7.35 (m, 7 H, Ar), 7.49–7.57 (m, 2
H, Hetar), 7.63–7.81 (m, 4 H, Hetar), 8.21–8.31 (m, 2 H, Hetar).
13C NMR (75 MHz, CDCl3): d = 18.4 (CH3), 21.1 (CH3), 55.4
(OCH3), 113.5, 114.4, 121.6, 121.7, 127.0, 127.1, 127.26, 127.34,
127.7, 127.8, 128.0, 128.1, 128.2, 131.8, 132.1, 134.7, 134.8, 137.4,
139.9, 146.3, 146.4, 147.6, 147.8, 159.9 (Ar, Hetar), 160.9, 161.7
(C=O, NCN).
(1) (a) Closs, F.; Gompper, R. Angew. Chem., Int. Ed. Engl.
1987, 26, 552; Angew. Chem. 1987, 99, 564. (b) Closs, F.;
Gompper, R.; Nöth, H.; Wagner, H.-U. Angew. Chem., Int.
Ed. Engl. 1988, 27, 842; Angew. Chem. 1988, 100, 875.
(c) Casser, L.; Iqbal, A.; Rochat, A. C. Eur. Patent Appl., EP
98808, 1983.
(2) (a) Beyerlein, T.; Tieke, B. Macromol. Rapid Commun.
2000, 21, 182. (b) Beyerlein, T.; Tieke, B.; Forero-Lenger,
S.; Brütting, W. Synth. Met. 2002, 130, 115.
(3) Herbst, W.; Hunger, K. Industrial Organic Pigments; VCH:
Weinheim, 1993, 550.
MS (EI, 70 eV): m/z (%) = 500 (100) [M+], 377 (59), 249 (60), 225
(32).
(4) (a) Rao, Y. S. Chem. Rev. 1976, 76, 625. (b) Pattenden, G.
Prog. Chem. Nat. Prod. 1978, 35, 133. (c) Knight, D. W.
Contemp. Org. Synth. 1994, 1, 287. (d) Schweppe, M.
Handbuch der Naturfarbstoffe; ecomed Verlagsgesellschaft:
Landsberg, 1992, 185. (e) Schweppe, M. Handbuch der
Naturfarbstoffe; ecomed Verlagsgesellschaft: Landsberg,
1992, 525.
(5) (a) Fürstenwerth, H. Ger. Offen., DE 3525109A1, 1987;
Chem. Abstr. 1987, 106, 103815f. (b) Rochat, A. C.; Iqbal,
A.; Pfenninger, J.; Casser, L. Eur. Patent Appl., EP 016309,
Anal. Calcd for C31H24N4O3 (500.56): C, 74.38; H, 4.83; N, 11.19.
Found: C, 74.15; H, 4.62; N, 10.65.
N-Phenyl-N¢-(4-methoxyphenyl)bis(quinazolin-4-on-2-yl) (8e)
Starting
with
N-phenyl-N¢-(4-methoxyphenyl)oxaldiimidoyl
dichloride (0.307 g, 1.0 mmol) and methyl 2-aminobenzoate (0.302
g, 2.0 mmol), 8e was isolated (0.37 g, 79%) as a colourless solid;
mp 238 °C.
Synthesis 2006, No. 15, 2507–2514 © Thieme Stuttgart · New York

2514
F. Helmholz et al.
PAPER
1984. (c) Solberg, Y. Z. Naturforsch., C 1977, 32, 292.
bis(imidoyl) dichlorides, see: Price, C. C.; Velzen, B. J. Org.
Chem. 1947, 12, 386. (c) See also: Wuckelt, J.; Döring, M.;
Langer, P.; Beckert, R.; Görls, H. J. Org. Chem. 1999, 64,
365.
(6) (a) Stachel, H.-D. Arch. Pharm. Ber. Dtsch. Pharm. Ges.
1962, 295, 735. (b) Mukai, T.; Konno, A.; Kumagai, T.;
Satake, K. Chem. Lett. 1985, 1809. (c) Stachel, H.-D.;
Schorp, M.; Maier, L.; Dandl, K. Liebigs Ann. Chem. 1994,
1121.
(7) Review: Langer, P.; Döring, M. Eur. J. Org. Chem. 2002,
221.
(8) Lindauer, D.; Beckert, R.; Döring, M.; Fehling, P.; Görls, H.
J. Prakt. Chem. 1995, 337, 143.
(10) (a) Langer, P.; Helmholtz, F.; Schröder, R. Synlett 2003,
2389. (b) Helmholz, F.; Schroeder, R.; Langer, P. Z.
Naturforsch., B 2005, 60, 1192. (c) See also: Käpplinger,
C.; Beckert, R.; Koci, J.; Braunerova, G.; Waisser, K.; Görls,
H. Heterocycles 2003, 60, 2457.
(11) For symmetrical derivatives, see: Langer, P.; Wuckelt, J.;
Döring, M.; Görls, H. Eur. J. Org. Chem. 2001, 1503.
(12) Langer, P.; Schroeder, R. Eur. J. Org. Chem. 2004, 1025.
(9) (a) For the reaction of arylacetates, see: Langer, P.;
Wuckelt, J.; Döring, M. J. Org. Chem. 2000, 65, 729. (b)
For the reaction of diethyl malonate with symmetrical
Synthesis 2006, No. 15, 2507–2514 © Thieme Stuttgart · New York