Synthesis and antimicrobial activities of a new class of 6-arylbenzimidazo[1,2-c]quinazolines

Article abstract of DOI:10.1590/S0103-50532010000100009

A series of 6-arylbenzimidazo[1,2-c]quinazoline compounds (11-20) were synthesised by the condensation of 2-(o-aminophenyl)benzimidazole with different arylaldehydes, followed by oxidative cyclisation of the resulting 2-o-arylideneaminophenylbenzimidazoles (1-10). All the products were characterized via IR, ¹H NMR, ¹³C NMR, MS and elemental analysis. The antimicrobial activities of all 6-arylbenzimidazo [1,2-c]quinazolines against three Gram-positive (S. aureus, B. subtilis, S. pyogenes), three Gram-negative (S. typhimurium, E. coli, K. pneumonia) bacteria and three fungal strains (A. niger, C. albicans, T. viridae) were evaluated. Among the compounds tested 13, 19 and 20 showed most potent inhibitory action against test organisms.

Full text of DOI:10.1590/S0103-50532010000100009

J. Braz. Chem. Soc., Vol. 21, No. 1, 49-57, 2010.
Printed in Brazil - ©2010 Sociedade Brasileira de Química
0103 - 5053 $6.00+0.00
Synthesis and Antimicrobial Activities of a New Class of
6-Arylbenzimidazo[1,2-c]quinazolines
Rondla Rohini,a Kanne Shanker,a P. Muralidhar Reddyb and Vadde Ravinder*,a
aDepartment of Chemistry, Kakatiya University, Warangal-506 009, A.P., India
bDepartment of Chemistry, National Dong Hwa University, Hualien, Taiwan
Uma série de compostos 6-arilbenzimidazo[1,2-c]quinazolina (11-20) foram sintetizados pela
condensação do 2-(o-aminofenil)benzimidazol com diferentes arilaldeídos seguida pela ciclização
oxidativa dos 2-o-arilidenoaminofenilbenzimidazol (1-10). Todos os produtos foram caracterizados
por espectroscopia no infravermelho (IR), ressonância magnética nuclear de prótons e de carbono,
(RMN 1H e RNN 13C), de massas (MS) e análise elementar. A atividade antimicrobial de todos os
6-arilbenzimidazo[1,2-c]quinazolina foi testada com três linhagens de bactérias Gram-positivas (S.
aureus, B. subtilis e S. pyogenes), três Gram-negativas (S. typhimurium, E. coli e K. pneumonia)
e de três linhagens de fungos (A. niger, C. albicans e T. viridae). Dos compostos testados, o 13, o
19 e o 20 mostraram-se ser os mais potentes inibidores contra os organismos testados.
A series of 6-arylbenzimidazo[1,2-c]quinazoline compounds (11-20) were synthesised by
the condensation of 2-(o-aminophenyl)benzimidazole with different arylaldehydes, followed
by oxidative cyclisation of the resulting 2-o-arylideneaminophenylbenzimidazoles (1-10). All
1
the products were characterized via IR, H NMR, 13C NMR, MS and elemental analysis. The
antimicrobial activities of all 6-arylbenzimidazo [1,2-c]quinazolines against three Gram-positive
(S. aureus, B. subtilis, S. pyogenes), three Gram-negative (S. typhimurium, E. coli, K. pneumonia)
bacteria and three fungal strains (A. niger, C. albicans, T. viridae) were evaluated. Among the
compounds tested 13, 19 and 20 showed most potent inhibitory action against test organisms.
Keywords: 6-Arylbenzimidazo[1,2-c]quinazolines, synthesis, antibacterial activity, antifungal
activity
Introduction
quinazoline compounds have been well-recognized for their
pharmacological properties, such as anti-inflammatory,13,14
antihypertensive,15 anti-HIV,16 bronco-dilatory,17 anti-
allergic,18 anti-cancer,19-21 anticonvulsant,22,23 antihelmintic,24
analgesic,25 antimalarial26 and antimicrobial27 activities.
Literature survey reveals that, benzimidazo [1,2-c]
quinazoline derivatives also show various biological
activities,23,28-30 such as anticancer, antiviral, antimicrobial,
anti-inflammatory and anticonvulsants.However, search is
continuously on to identify a more potent lead molecule as
these molecules are developing resistance over a period.
Basedontheimportanceofthesemolecules,ourattentionwas
attracted towards synthesis of novel quinazoline derivatives
in order to find more potent biologically active molecules.
Hence, we report here the synthesis and characterization
of new 6-arylbenzimidazo[1,2-c]quinazoline compounds
(11-20). In addition, the antimicrobial activities of all
synthesized quinazolines against different bacteria and
Heterocycles have a central position in medicinal as
well as in organic chemistry1-3 and considerable attention
has been focused on their syntheses. Nitrogen heterocycles
in particular exhibit diverse biological and pharmacological
activities4-6 due in part to the similarities with many natural
and synthetic molecules with known biological activity.7
Moreover, benzimidazoles and quinazolines are of the most
extensively studied classes of heterocyclic compounds, and
have received much attention from synthetic organic as
well as medicinal chemists, because of the diverse range
of their biological activities8,9 and their applications in
several areas as materials in electronics, in electrochemistry
as anticorrosive agents, as polymers or optical materials
and fluorescent tags in DNA sequencing.10-12 In general,
*e-mail: ravichemku@rediffmail.com

50
Synthesis and Antimicrobial Activities of a New Class of 6-Arylbenzimidazo[1,2-c]quinazolines
J. Braz. Chem. Soc.
fungi were evaluated. Among the compounds tested some
of quinazolines were found to be superior in inhibiting all
the bacterial and fungal strains.
attributable to nC=N provides a strong evidence for the
condensation and also confirms the formation of the
azomethines 1-10.35 The oxidative cyclisation of compounds
1-10 to 11-20 were accompanied by the disappearance of the
absorptionmaximaat3150-3300cm-1,whichareascribedtothe
vibrationsofNHgroupofthebenzimidazolering;atthesame
time the appearance of a new maximum at 1360-1388 cm-–1,
which is characteristic for benzimidazoquinazoline ring with
a tertiary nitrogen atom, appears.23,36
Results and Discussion
Chemistry
The condensation of o-phenylenediamine with
anthranilic acid was carried out in presence of
polyphosphoric acid at 250 °C for 4 h to obtain the known
1
The H NMR spectra of the compound A as well as
its derivatives have been recorded in CDCl3/DMSO-d6
using TMS as internal standard. In the spectra of
2-(o-aminophenyl) benzimidazole (A), signals at d 6.4 and
d 8.25 ppm were appeared corresponding to free amino
and imidazolyl protons respectively.33,35 The aromatic
protons of various environments present in all compounds
appeared as multiplets in the range of d 6.84-8.81 ppm.35,37
1H NMR spectra of compounds 1-10 contain signals
corresponding to CH=N protons in the range of d 8.07-
8.29 ppm suggesting the condensation of aromatic
aldehydes with compound A. However, in the spectra of
1-10 compounds the disappearance of signals at d 6.4 ppm
which is due to NH2 protons of compound A supports the
involvement of aminogroup in condensation and confirms
the formation of azomethines. Finally, in the spectra of
11-20 compounds disappearance of signals corresponding
to –NH of imidazolyl ring and CH=N protons supports the
benzimidazoquinazoline ring structure.23, 36
o
2-(o-aminophenyl) benzimidazole (A) (mp 214 C).31
The target compounds were prepared by using the
reaction sequence in Scheme 1. Initially, we synthesised
ten new 2-o-arylideneaminophenylbenzimidazoles
(1-10) via the condensation between 2-(o-aminophenyl
benzimidazole(A) and various arylaldehydes.
At last, we prepared 6-arylbenzimidazo [1,2-c]
quinazolines (11-20) through oxidative cyclisation32 of
2-o-arylideneaminophenylbenzimidazoles (1-10).
IR spectra of compound A showed absorption band at
3350 cm-1 assigned to aminophenyl ring and in the case
of compounds A and 1-10 two absorption bands in the
region 3150-3300 cm-1 and 1420 cm-1 were assigned to –
NH stretching and bending vibrations of imidazolyl ring,
respectively.33,34 The absence of aminophenyl ring absorption
at 3350 cm-1 and appearance of a strong intensity band in the
IRspectraofcompounds(1-10)intherangeof1610-1650cm-1
Scheme 1. Synthesis of 6-arylbenzimidazo[1,2-c]quinazolines (11-20).

Vol. 21, No. 1, 2010
Rohini et al.
51
13C NMR spectra of all the compounds contain
signals in the range of d 141.1-171.2 ppm confirming the
presence of carbon, which is doubly bonded to nitrogen.
The aromatic carbons of various environments present
in all the compounds appeared as signals in the range of
Bacillus subtilis, Streptococcus pyogenes (Gram positive)
and Salmonella typhimurium, Escherichia coli, Klebsiella
pneumonia (Gram negative) bacterial strains using
ampicillin as standard. The antifungal activity was
investigated against Aspergillus niger, Candida albicans,
Trichoderma viridae fungal strains using ketoconazole as
standard. Preliminary screening of target compounds and
standard drugs were performed at fixed concentrations of
1000 µg mL-1. Inhibition was recorded by measuring the
diameter of the inhibition zone at the end of 48 h for bacteria
and 72 h for fungi. Each experiment was repeated thrice
and the average of the three independent determinations
was recorded. Screening results are summarized in Table 1.
Among the compounds tested 13 was found to exhibit good
activity against all bacterial and fungal strains. Furthermore,
the most potent activity was observed in 19 and 20 against
all bacterial and fungal strains when compared to respective
standard drugs ampicillin and ketoconazole. The minimum
inhibitory concentration39 of these quinazolines (13, 19 and
20) was also verified by the liquid dilution method in which
the effectiveness was observed at lower concentrations. The
detailed antibacterial and antifungal preliminary screening
methods are given in supplementary material.
1
d 103.2-156.2 ppm.37 The H and 13C NMR spectra
(Figure S2 and Figure S3) of compound 20 are given in
supplementary material.
All the compounds (except 2 and 12) showed a single
peak in ESI–MS suggesting the molecular formulae of
the azomethines and quinazolines. Compounds, 2 and 12
exhibited molecular ion peaks (M+) at m/z 391, (M+2) at
m/z 393 and (M+) at m/z 389, (M+2) at m/z 391 respectively,
which is due to the isotopic abundance of bromine. The
FAB mass spectrum of compound 20 shows a molecular ion
peak (M+) at m/z 296 (65.1%), which confirms the proposed
formula (C19H12N4). The peaks have been observed at m/z
values 218 (40.3%), 193 (52.2%), 192 (100%), 180 (74.8%)
and 76 (24.4%), which indicate the fragmentation pattern
and their intensity gives an idea about the abundance and
stability of the fragments. The mass fragmentation pattern
(Scheme S1) of compound 20 as assigned on the basis of
mass spectra (Figure S3) is presented in supplementary
material.
Determination of minimum inhibitory concentration (MIC)
The minimum inhibitory concentration of 13, 19 and 20
against S. aureus, B. subtilis, S. pyogenes, S. typhimurium,
E. coli, K. pneumonia (bacterial strains), Aspergillus
niger, Candida albicans, Trichoderma viridae (fungal
strains) were determined by liquid dilution method. Stock
solutions of test samples with 2.5, 5, 10, 15, 20, 25, 30,
Biological study
Antimicrobial activity
Theinvitroantimicrobialactivitywascarriedoutbycup-
platemethod.38Allthesynthesizedquinazolineswerescreened
for antibacterial activity against Staphylococcus aureus,
Table 1. Zone of inhibition of newly synthesized 6-arylbenzimidazo[1,2-c]quinazolines (11-20) against different bacteria and fungi
Compound
Zone of inhibition (mm)
Gram-negative bacteria
(1000 µg mL-1)
Gram-positive bacteria
S. aureus
Fungi
B. subtilis S. pyogenes S. typhimurium
E. coli
18
K. pneumonia
A. niger
21
C. albicans
T. viridae
11
12
13
14
15
16
17
18
19
20
Std
20
21
50
19
22
18
16
15
55
52
48a
18
20
45
14
18
14
18
10
45
48
39a
13
15
48
15
13
15
15
12
52
50
35a
15
15
45
12
16
12
15
10
50
46
45a
16
18
50
15
12
16
18
13
52
50
45a
16
15
48
13
10
12
15
9
9
12
46
13
9
19
18
48
49
21
16
18
15
20
16
13
12
13
50
48
41b
19
18
9
11
50
55
50
51
40b
51
50
40a
45b
a Ampicillin; b Ketoconazole

52
Synthesis and Antimicrobial Activities of a New Class of 6-Arylbenzimidazo[1,2-c]quinazolines
J. Braz. Chem. Soc.
35, 40, 45 and 50 µg mL-1 concentrations were prepared
with appropriate solvent. The solutions of standard drugs,
ampicillin and ketoconazole were prepared in the same
concentrations. Inoculums of the bacterial and fungal
culture were also prepared. To a series of tubes containing
1 mL each of quinazoline compound solution with different
concentrations and 0.2 mL of the inoculum was added.
Further 3.8 mL of the sterile water was added to each of
the test tubes. These test tubes were incubated for 24 h and
observed for the presence of turbidity. This method was
repeated by changing quinazoline compounds with standard
drug ampicillin (in case of bacteria) and with ketoconazole
(in case of fungi) for comparison.The minimum inhibitory
concentration at which no growth was observed was taken
as the MIC values. Comparison of MIC values (in µg mL-1)
of quinazolines and standard drugs against different
bacteria and fungi are presented in Figure 1. From these
results, it is evident that 13 (MIC range 5-20 µg mL-1),
19 and 20 compounds (MIC range 2.5-15 µg mL-1) are
showing superior activity when compared to ampicillin
and ketoconazole towards inhibiting all tested bacterial
and fungal strains.
Conclusions
Quinazolines and related derivatives are classes of
heterocyclic compounds contain the pyrimidine nucleus
in their structures. Literature survey reveals that a
variety of antimicrobial agents contains quinazoline
moiety and also fused quinazoline ring systems such
as benzimidazoloquinazolines, indoloquinazolines
and many other. In a search for new fused quinazoline
systems with potential biological activities, we planned to
prepare new 6-arylbenzimidazo[1,2-c]quinazolines, from
2-(o-aminophenyl) benzimidazole and various aldehydes
as starting compounds. We have chosen six bacterial and
three fungal strains for microbial studies of these entire
quinazoline compounds. From this study it is evident
that all quinazoline compounds are showing moderate
to good activity towards inhibiting all tested bacterial
Table 2 . MIC values potent 6-arylbenzimidazo[1,2-c]quinazolines (13, 19 and 20) and standard drugs
Compound
Range of concentration (µg mL-1)
Gram-negative bacteria
Gram-positive bacteria
S.aureus
Fungi
B. subtilis S. pyogenes S. typhimurium
E. coli
15
K. pneumonia
A. niger
10
C. albicans
T. viridae
13
19
20
Std
10
2.5
5
15
15
10
20a
20
10
15
25a
10
5
5
20
5
15
10
10
2.5
2.5
10
10a
10
5
10
15
25b
15
10a
15a
10a
15b
20b
a Ampicillin; b Ketoconazole
Figure 1. Comparison of MIC values (in µg mL-1) of quinazolines and standard drugs against different bacteria and fungi.

Vol. 21, No. 1, 2010
Rohini et al.
53
and fungal strains. Furthermore, the most potent activity
was observed in (13, 19 and 20) against all bacterial and
fungal strains when compared to respective standard drugs
ampicillin and ketoconazole. A possible explanation for
this result is that the biological activity of compounds
may be depending on the basic skeleton of molecule as
well as on the nature of substituents. Hence we conclude
that the most potent activity of 13, 19 and 20 compounds
may be due to the presence of heterocyclic isoquinolyl,
pyridyl and nitro substituted aryl groups at C6 position of
the benzimidazo[1,2-c]quinazoline moiety.
added the appropriate aldehyde (2 mmol) and 2-3 drops
of acetic acid. The resultant mixture was refluxed under
heat (40-55 °C) for 2 h after which the compound was
obtained. The product was filtered and recrystalized from
a dichloromethane-methanol mixture.
Procedure for preparation of 6-arylbenzimidazo[1,2-c]
quinazolines[BIQ-Ar] (11-20)
All the 6-arylbenzimidazo[1,2-c]quinazolines (11-20)
were prepared from azomethines 1-10 through oxidative
cyclisation method reported by Davis and Mann.32 Powdered
potassium permanganate (1.5 equiv.) was added to a
solution of the azomethyne compound (1-10) in 50-75 mL
of acetone. The mixture was boiled (40-80 °C) under
reflux for 30 min. It was then filtered hot, and an equal
volume of hot water added to the filtrate. The quinazolines
(11-20) rapidly separated, and was collected by filtration
and recrystalized from dimethylformamide. All the
synthesized compounds were characterized as given below.
Experimental
Analar grade reagents and freshly distilled solvents were
usedthroughouttheinvestigations. Compoundswerechecked
for their purity by TLC using Merck 60 F254 silica gel plates
and spots were located by iodine vapors. Micro analytical (C,
N, H) data was obtained by using a Perkin-Elmer 2400 CHN
elemental analyzer. The IR spectra were recorded in KBr
1
pellets on Perkin-Elmer-283 spectrophotometer. H NMR
spectrawereacquiredat400MHzand13CNMRwasacquired
at 67.93 MHz on a Bruker NMR spectrometer. FAB mass
spectra were recorded on a Finnigan-MAT 1020 instrument.
An ion trap mass spectrometer (Agilent Series LC/MSDTrap
SL) equipped with an electrospray ionization (ESI) source
was used for MS analyses. Hot air oven (Instrument and
Equipment Pvt. Ltd., Mumbai), incubator (Instrument and
Equipment Pvt. Ltd., Mumbai), laminar airflow unit (Clas
laminar technologies Pvt. Ltd. Secunderabad), autoclave
(Medica Instrument Mfg. Co., Mumbai) were used in the
presentinvestigations.OrganismslikeStaphylococcusaureus,
Bacillus subtilis, Streptococcus pyogenes (Gram positive),
Salmonella typhimurium, Escherichia coli, Klebsiella
pneumonia (Gram negative) bacteria and Aspergillus niger,
Candida albicans, Trichoderma viridae fungi were used in
the present investigations.
2-(o-Aminophenyl)benzimidazole [BIPhNH2] (A)
Yield 82%; mp 213-214oC (lit. 214oC);31 IR nmax/cm-1:
3350 (NH2), 3300 (NH); H NMR (400 MHz, CDCl3) d
6.4 (s, 2H, NH2), 6.5–7.7 (m, 8H, Ar-H), 8.25 (s, 1H, NH);
13C NMR (67.93 MHz, CDCl3) d 113.1, 114.2, 116.2, 119.3,
121.5, 123.2, 130.3, 141.5. 145.2, 154.1 (13C,Ar-C).Anal.
Found: C, 74.65; H, 5.32; N, 20.05. Calc. for C13H11N3:
C, 74.62; H, 5.30; N, 20.08%. MS (ESI): (M+)m/z at 209.
1
2-([2-(1H-Benzo[d]imidazol-2-yl)phenyl]iminomethyl)
phenol (1)
Yield 81%; mp 288-290 °C; IR nmax/cm-1: 3420, 3300,
1650, 1590, 1575, 1130;1H NMR (400 MHz, CDCl3) d 6.83
(t, 1H, Ar, J 7.4Hz), 6.95-7.38 (m, 9H, Ar), 7.63-7.95 (m,
2H, Ar), 8.25 (s, 1H, CH=N), 8.89 (s, 1H, imidazolyl-NH)
10.22 (s, 1H,-OH); 13C NMR (67.93 MHz, CDCl3) d 114.3,
117.2, 118.4, 123.5, 126.4, 131.5, 132.2, 133.6, 136.5,
141.2, 142,6, 143.8, 146.3, 163.7, 167.5 (20C,Ar-C);Anal.
Found: C, 76.65; H, 4.81; N, 13.40. Calc. for C20H15N3O:
C, 76.66; H, 4.82; N, 13.41%. MS (ESI): (M+) m/z at 313.
Preparation of 2-(o-aminophenyl)benzimidazole
[BIPhNH2] (A)
2-(o-aminophenyl) benzimidazole (A) was prepared by
reacting orthophenylenediamine (OPD) with anthranillic
acid in freshly prepared polyphosphoric acid (PPA) acid
at 250 °C for 4 h.
2-([2-(1H-Benzo[d]imidazol-2-yl)phenyl]iminomethyl)-4-
bromophenol (2)
Yield 79%; mp 318-320 °C; IR nmax/cm-1: 3425, 3300,
1630, 1610, 1580, 1100;1H NMR (400 MHz, CDCl3) d 6.82
(t, 1H,Ar, J 7.4 Hz), 6.85 (S, 1H,Ar), 6.92-7.46 (m, 7H,Ar),
7.62 -7.94 (m, 2H, Ar), 8.21 (s, 1H, CH=N), 8.86 (s, 1H,
-NH), 10.21 (s, 1H, -OH); 13C NMR (67.93 MHz, CDCl3)
d 107.5, 114.1, 118.2, 123.5, 126.2, 130.5, 131.2, 132.2,
136.5, 141.1, 142,8, 143.5, 146.3, 154.48, 158.5, 167.1
Procedure for preparation of mono-2-o-(arylideneamino)
phenyl benzimidazoles (1-10)
To a hot stirred solution of 2-(o-aminophenyl)
benzimidazole (A) (2 mmol) in ethanol (20 mL) were

54
Synthesis and Antimicrobial Activities of a New Class of 6-Arylbenzimidazo[1,2-c]quinazolines
J. Braz. Chem. Soc.
(20C, Ar-C); Anal. Found: C, 61.20; H, 3.56; N, 10.71.
Calc. for C20H14BrN3O: C, 61.24; H, 3.60; N, 10.71%. MS
(ESI): (M+) m/z (%) 391, (M+2) m/z at 393.
Found: C, 70.60; H, 4.25; N, 11.70. Calc. for C21H15N3O3 :
C, 70.58; H, 4.23; N, 11.76%. MS (ESI): (M+)atm/z 357.
4-([2-(1H-Benzo[d]imidazol-2-yl)phenyl]iminomethyl)-
2,6-dimethylphenol (7)
2-([2-(1H-Benzo[d]imidazol-2-yl)phenyl]iminomethyl)-
4-nitrophenol (3)
Yield 78%; mp 211-213 °C; IR nmax/cm-1: 3425, 3300,
2958, 1645, 1608, 1575, 1130; 1H NMR (400MHz, CDCl3)
d 2.30 (s, 6H, Ar-CH3), 6.61 (S, 2H, Ar), 6.83 (t, 1H, Ar,
J 7.4 Hz), 7.06-7.41 (m, 5H, Ar), 7.62 -7.93 (m, 2H, Ar),
8.07 (s, 1H, CH=N), 8.85 (s, 1H, -NH), 10.21(s, 1H,
-OH); 13C NMR (67.93 MHz, CDCl3) d 15.7 (2C, -CH3),
114.1, 123.4, 126.2, 127.4, 128.3, 132.2, 136.3, 141.1,
146.6, 152.8, 171.2 (20C, Ar-C); Anal. Found: C, 77.44;
H, 5.60; N, 12.29. Calc. for C22H19N3O: C, 77.40; H, 5.61;
N, 12.31%. MS (ESI): (M+)atm/z 341.
Yield 81%; mp 255-257 °C; IR nmax/cm-1: 3420, 3300,
1635, 1608, 1590, 1525, 1345, 1130, 850; 1H NMR
(400 MHz, CDCl3) d 6.82 (t, 1H,Ar, J 7.4 Hz), 7.05-7.41(m,
6H,Ar), 7.60 (s, 1H,Ar), 7.63-7.95 (m, 2H,Ar), 8.01(d, 1H,
J 7.7 Hz), 8.29 (s, 1H, CH=N), 8.85 (s, 1H, -NH), 10.45 (s,
1H, -OH); 13C NMR (67.93 MHz, CDCl3) d 114.4, 118.1,
119.2, 123.1, 124.3, 126.2, 131.2, 132.2, 136.5, 141.1,
143.5, 146.5, 164.8, 170.2 (20C, Ar-C); Anal. Found: C,
67.01; H, 3.95; N, 15.58. Calc. for C20H14N4O3 : C, 67.03;
H, 3.94; N, 15.63%. MS (ESI): (M+)m/z at 358.
N1-[(E)-1-(3,5-Dimethoxyphenyl)methylidene]-2-(1H-
benzo[d]imidazol-2-yl) aniline (8)
2-([2-(1H-Benzo[d]imidazol-2-yl)phenyl]iminomethyl)-4-
methoxyphenol (4)
Yield 75%; mp 228-230 °C; IR nmax/cm-1: 3300, 1635,
1600, 1580, 1246,1130, 1035; 1H NMR (400 MHz, CDCl3)
d 3.90 (s, 6H, -OCH3), 6.46 (S, 1H, Ar), 6.82 (t, 1H, Ar,
J 7.4 Hz), 6.85 (S, 2H, Ar), 7.08-7.45 (m, 5H, Ar), 7.62-
7.94 (m, 2H, Ar), 8.14 (s, 1H, CH=N), 8.89 (s, 1H,- NH);
13C NMR (67.93 MHz, CDCl3) d 55.2 (2C, -OCH3), 103.9,
108.1, 114.0, 114.2, 123.6, 127.3, 131.2, 132.2, 134.3,
141.1, 146.6, 162.3, 168.3 (20C, Ar-C); Anal. Found: C,
73.92; H, 5.35; N, 11.76. Calc. for C22H19N3O2: C, 73.93;
H, 5.36; N, 11.76%. MS (ESI): (M+)at m/z 357.
Yield 80%; mp 285-287 °C; IR nmax/cm-1: 3425, 3300,
1638, 1605, 1585, 1246, 1128, 1035;1H NMR (400 MHz,
CDCl3) d 3.90 (s, 3H, OCH3), 6.48 (s, 1H, Ar), 6.83 (t, 1H,
Ar, J 7.4 Hz), 6.84-7.65 (m, 8H, Ar), 7.94 (d, 1H, Ar, J 7.3
Hz), 8.16 (s, 1H, CH=N), 8.85 (s, 1H, -NH), 10.22 (s, 1H,
-OH); 13C NMR (67.93 MHz, CDCl3) d 56.1, (1C, -OCH3),
114.0, 121.5, 122.4, 123.5, 126.2, 130.5, 131.1, 132.4,
141.1, 142,3, 146.8, 153.2, 153.6, 167.5 (20C,Ar-C),Anal.
Found: C, 73.42; H, 5.01; N, 12.25. Calc.for C21H17N3O2 :
C, 73.45; H, 4.99; N, 12.24 %. MS (ESI): (M+) atm/z 343.
N1-[(E)-1-(1-Isoquinolyl)methylidene]-2-(1H-benzo[d]
imidazol-2-yl)aniline (9)
3-([2-(1H-Benzo[d]imidazol-2-yl)phenyl]iminomethyl)
benzoic acid (5)
Yield 81%; mp 254-256 °C; IR nmax/cm-1: 3300, 1640,
1610, 1580, 1130; 1H NMR (400 MHz, CDCl3) d 6.83 (t,
1H, Ar, J 7.4 Hz), 7.06-8.21 (m, 13H, Ar), 8.72 (d, 1H, J
5.25 Hz), 8.89 (s, 1H, -NH); 13C NMR (67.93 MHz, CDCl3)
d 114.0 114.2, 121.6, 123.4, 125.6, 127.3, 128.8, 132.6,
135.6, 141.8, 146.8, 157.2, 168.4 (23C,Ar-C);Anal. Found:
C, 79.25; H, 4.60; N, 16.05. Calc. for C23H16N4: C, 79.29;
H, 4.63; N, 16.08%. MS (ESI): (M+) atm/z 348.
Yield 76%; mp 226-228 °C; IR nmax/cm-1: 3535, 3300,
3215,1685, 1635, 1580, 1130;1H NMR (400 MHz, CDCl3)
d 6.83 (t, 1H, Ar, J 7.4 Hz), 7.05-8.20 (m, 12H, Ar), 8.82
(s, 1H, -NH), 11.31 (s, 1H, -COOH); 13C NMR (67.93
MHz, CDCl3) d 114.1, 114.4, 123.5, 126.2, 129.2, 130.5,
130.8, 132.0, 133.1, 141.1, 143.5, 146.8, 167.1, 170.2
(21C, Ar-C), Anal. Found: C, 73.85; H, 4.49; N, 12.32.
Calc. for C21H15N3O2: C, 73.89; H, 4.43; N, 12.31%.
MS (ESI): (M+)atm/z 341.
N1-[(E)-1-(3-Pyridyl)methylidene]-2-(1H-benzo[d]
imidazol-2-yl)aniline (10)
3-([2-(1H-Benzo[d]imidazol-2-yl)phenyl]iminomethyl)-4-
hydroxybenzoic acid (6)
Yield 79%; mp 230-232 °C; IR nmax/cm-1: 3300, 1640,
1610, 1585, 1130; 1H NMR (400 MHz, CDCl3) d 6.82 (t,
1H, Ar, J 7.4 Hz), 7.05-7.48 (m, 6H, Ar), 7.63 (d, 1H, Ar,
J 7.3 Hz), 7.75-8.62 (m, 4H, Ar), 8.65 (s, 1H, Ar), 8.89 (s,
1H, -NH); 13C NMR (67.93 MHz, CDCl3) d 113.4, 114.1,
121.5, 123.4, 126.3, 128.3, 130.3, 136.5, 141.8, 143,6,
146.5, 151.6, 152.8, 165.6 (19 C, Ar-C); Anal. Found: C,
76.50; H, 4.72; N, 18.75. Calc. for C19H14N4: C, 76.49; H,
4.73; N, 18.78%. MS (ESI): (M+)atm/z 298.
Yield 79%; mp 315-317 °C; IR nmax/cm-1: 3535, 3425,
3300, 3215,1680, 1640, 1585, 1128; 1H NMR (400 MHz,
CDCl3) d 6.83 (t, 1H, Ar, J 7.4 Hz), 7.02-8.13 (m, 11H,
Ar), 8.89 (s, 1H, -NH), 10.21 (s, 1H, -OH), 11.42 (s, 1H,
-COOH); 13C NMR (67.93 MHz, CDCl3) d 113.6, 114.0,
114.3, 123.4, 124.5, 126.2, 127.5, 132.8, 136.4, 141.1,
142,3, 144.5, 146.1, 166.2, 166.7, 168.8 (21C,Ar-C);Anal.

Vol. 21, No. 1, 2010
Rohini et al.
55
2-Benzo[4,5]imidazo[1,2-c]quinazolin-6-ylphenol (11)
Yield 82%; mp 300-302 °C; IR nmax/cm-1: 3425, 1621,
1585, 1529, 1457, 1380, 773, 741, 732; H NMR (400
12.30. Calc. for C21H15N3O2: C, 73.89; H, 4.43; N, 12.31%.
MS (ESI): (M+)atm/z 341.
1
MHz, DMSO-d6) d 6.65 (d, 1H, Ar, J 8.2 Hz), 6.81 (d,
1H, Ar, J 8.4 Hz), 6.83 (t, 1H, Ar, J 7.4 Hz), 7.15-7.85 (m,
8H, Ar), 8.75 (dd, 1H, J 6.9, 2.5 Hz), 10.29 (s, 1H, -OH);
13C NMR (67.93 MHz, DMSO-d6) d 112.4, 116.7, 120.3,
121.5, 122.4, 125.8, 129.3, 131.5, 132.7, 139.2, 143.6,
152.5, 159.2, 161.4 (20 C, Ar-C); Anal. Found: C, 77.18;
H, 4.19; N, 13.51. Calc. for C20H13N3O: C, 77.16; H, 4.21;
N, 13.50%. MS (ESI): (M+) atm/z 311.
3-Benzo[4,5]imidazo[1,2-c]quinazolin-6-ylbenzoic acid
(15)
Yield 75%; mp 238-240 °C; IR nmax/cm-1: 3535, 1685,
1
1621, 1585, 1529, 1457, 1380, 773, 741, 732; H NMR
(400 MHz, DMSO-d6) d 6.64 (d, 1H, Ar, J 8.2 Hz), 6.82
(d, 1H, Ar, J 8.4 Hz), 6.83 (t, 1H, Ar, J 7.4 Hz), 7.21-8.31
(m, 7H, Ar), 8.63 (s, 1H, Ar), 8.75 (dd, 1H, J 6.9, 2.5 Hz),
11.34 (s, 1H, -COOH); 13C NMR (67.93 MHz, DMSO-d6)
d 111.6, 114.6, 120.9, 122.8, 124.6, 126.3, 129.7, 131.8,
132.5, 142.6, 143.1, 152.1, 157.8, 167.2 (21C,Ar-C);Anal.
Found: C, 74.31; H, 3.85; N, 12.39. Calc. for C21H13N3O2:
C, 74.33; H, 3.86; N, 12.38%. MS (ESI): (M+)atm/z 339.
2-Benzo[4,5]imidazo[1,2-c]quinazolin-6-yl-4-
bromophenol (12)
Yield 75%; mp 330-332 °C; IR nmax/cm-1: 3425, 1621,
1
1610, 1524, 1459, 1378, 775, 744, 739; H NMR (400
MHz, DMSO-d6) d 6.65 (d, 1H, Ar, J 8.2 Hz), 6.81 (d,
1H, Ar, J 8.4 Hz), 6.82 (t, 1H, Ar, J 7.4 Hz), 7.15-7.56
(m, 6H, Ar), 7.75 (s, 1H, Ar), 8.75 (dd, 1H, J 6.9, 2.5 Hz),
10.30 (s, 1H, -OH); 13C NMR (67.93 MHz, DMSO-d6) d
111.4, 118.2, 120.1, 121.5, 122.3, 125.8, 130.7, 131.5,
132.6, 133.2, 145.6, 146.5, 152.8, 154.5, 161.2 (20 C,
Ar-C); Anal. Found: C, 61.55; H, 3.12; N, 10.75. Calc. for
C20H12BrN3O: C, 61.56; H, 3.10; N, 10.77%. MS (ESI): at
m/z (M+)389, (M+2) 391.
3-Benzo[4,5]imidazo[1,2-c]quinazolin-6-yl-4-
hydroxybenzoic acid (16)
Yield 78%; mp 342-344 °C; IR nmax/cm-1: 3535, 3425,
1680, 1621, 1585, 1529, 1457, 1388, 773, 740, 738;
1H NMR (400 MHz, DMSO-d6) d 6.65 (d, 1H, Ar, J 8.2
Hz), 6.81 (d, 1H, Ar, J 8.4 Hz), 6.83 (t, 1H, Ar, J 7.4 Hz),
7.20-8.15 (m, 6H, Ar), 8.49 (s, 1H, Ar), 8.75 (dd, 1H, J
6.9, 2.5 Hz), 10.21 (s, 1H, -OH), 11.30 (s, 1H, -COOH);
13C NMR (67.93 MHz, DMSO-d6) d 112.6, 117.7, 120.5,
121.7, 122.5, 128.7, 131.8, 135.5, 143.5, 143.2, 152.5,
161.3, 162.8, 165.2 (21C, Ar-C); Anal. Found: C, 70.95;
H, 3.70; N, 11.80. Calc. for C21H13N3O3: C, 70.98; H, 3.69;
N, 11.82%. MS (ESI): (M+)atm/z 355.
2-Benzo[4,5]imidazo[1,2-c]quinazolin-6-yl-4-nitrophenol
(13)
Yield 76%; mp 241-243 °C; IR nmax/cm-1: 3425, 1640,
1605, 1580, 1520, 1459, 1385, 851, 775, 745, 749, 690;
1H NMR (400 MHz, DMSO-d6) d 6.64 (d, 1H,Ar, J 8.2 Hz),
6.82 (d, 1H, Ar, J 8.4 Hz), 6.83 (t, 1H, Ar, J 7.4 Hz), 7.21-
8.15 (m, 6H, Ar), 8.45 (s,1H,Ar), 8.74 (dd, 1H, J 6.9, 2.5
Hz), 10.29 (s, 1H, -OH); 13C NMR (67.93 MHz, DMSO-d6)
d 112.4, 118.3, 120.6, 121.7, 124.8, 125.4, 126.8, 130.7,
132.3, 138.4, 143.6, 145.4, 152.1, 163.2, 164.5 (20C,
Ar-C); Anal. Found: C, 67.42; H, 3.40N, 15.71. Calc. for
C20H12N4O3: C, 67.41; H, 3.39N, 15.72%. MS (ESI): (M+)
at m/z 356.
4-Benzo[4,5]imidazo[1,2-c]quinazolin-6-yl-2,6-
dimethylphenol (17)
Yield 71%; mp 208-210 °C; IR nmax/cm-1: 3425, 2958,
1680, 1621, 1585, 1529, 1457, 1388, 773, 741, 739;
1H NMR (400 MHz, DMSO-d6) d 2.31 (s, 6H, -CH3), 6.64
(d, 1H, Ar, J 8.2 Hz), 6.82 (d, 1H, Ar, J 8.4 Hz), 6.83 (t,
1H, Ar, J 7.4 Hz), 7.20-7.53 (m, 6H, Ar), 8.74 (dd, 1H, J
6.9, 2.5 Hz), 10.21 (s, 1H, -OH); 13C NMR (67.93 MHz,
DMSO-d6) d 15.6 (2C, -CH3), 112.8, 114.5, 121.9, 122.4,
124.6, 126.5, 128.7, 133.5, 145.1, 151.1, 152.5, 158.2,
(20C, Ar-C); Anal. Found: C, 77.86; H, 5.01; N, 12.35.
Calc. for C22H17N3O: C, 77.86; H, 5.05; N, 12.38%. MS
(ESI): (M+)at m/z 339.
2-Benzo[4,5]imidazo[1,2-c]quinazolin-6-yl-4-
methoxyphenol (14)
Yield 81%; mp 300-302 °C; IR nmax/cm-1: 3425, 1638,
1615, 1575, 1465, 1380, 1245, 1038, 770, 742, 739;
1H NMR (400 MHz, DMSO-d6) d 3.91 (s, 3H, Ar-OCH3),
6.65 (d, 1H, Ar, J 8.2 Hz), 6.82 (d, 1H, Ar, J 8.4 Hz), 6.83
(t, 1H, Ar, J 7.4 Hz), 6.98-7.53 (m, 7H, Ar), 8.76 (dd, 1H,
J 6.9, 2.5 Hz), 10.29 (s, 1H, -OH); 13C NMR (67.93 MHz,
DMSO-d6) d 56.3 (1C, -OCH3), 112.3, 119.6, 121.7, 122.7,
124.8, 127.8, 130.7, 131.2, 137.2, 143.6, 152.2, 155.6,
160.3 (20C, Ar-C); Anal. Found: C, 73.85; H, 4.41; N,
6-(3,5-Dimethoxyphenyl)benzo[4,5]imidazo[1,2-c]
quinazoline (18)
Yield 75%; mp 235-237 °C; IR nmax/cm-1: 1645, 1605,
1528, 1456, 1246, 1380, 1038, 773, 741, 732; 1H NMR (400
MHz, DMSO-d6) d 3.90 (s, 6H, -OCH3), 6.54 (s, 1H, Ar),
6.65 (d, 1H, Ar, J 8.2 Hz), 6.81 (d, 1H, Ar, J 8.4 Hz), 6.83
(t, 1H, Ar, J 7.4 Hz), 7.20-7.51 (m, 4H, Ar), 7.68 (s, 2H,

56
Synthesis and Antimicrobial Activities of a New Class of 6-Arylbenzimidazo[1,2-c]quinazolines
J. Braz. Chem. Soc.
Ar), 8.75 (dd, 1H, J 6.9, 2.5 Hz); 13C NMR (67.93 MHz,
DMSO-d6) d 55.4 (2C, -OCH3), 103.5, 104.7, 112.3,
120.3, 124.3, 126.9, 131.3, 133.4, 141.2, 143.8, 152.2,
155.2, 165.2 (20C, Ar-C); Anal. Found: C, 74.34; H, 4.83;
N, 11.80. Calc. for C22H17N3O2: C, 74.35; H, 4.82;
N, 11.82%. MS (ESI): (M+)at m/z 355.
8. Zhang, Y.; Chen, Z.; Lou, Y.; Yu, Y.; Eur. J. Med. Chem. 2009,
44, 448.
9. Ishida, T.; Suzuki, T.; Hirashima, S.; Mizutani, K.;Yoshida,A.;
Ando, I.; Ikeda, S.; Adachi, T.; Hashimoto, H.; Bioorg. Med.
Chem. Lett. 2006, 16, 1859.
10. Herget, T.; Freitag, M.; Morbitzer, M.; Kupfer, R.; Stamminger,
T.; Marschall, M.; Antimicrob. Agents Chemother. 2004, 48,
4154.
6-(1-Isoquinolyl)benzo[4,5]imidazo[1,2-c]quinazoline (19)
Yield 72%; mp 274-276 °C; IR nmax/cm-1: 1631, 1610,
11. Hranjec, M.; Karminski-Zamola G.; Chemistry in Industry 2008,
57, 299.
1
1585, 1529, 1457, 1380, 773, 741, 732; H NMR (400
MHz, DMSO-d6) d 6.64 (d, 1H, Ar, J 8.2Hz), 6.82 (d, 1H,
Ar, J 8.4 Hz), 6.83 (t, 1H, Ar, J 7.4 Hz), 7.21-8.51 (m, 9H,
Ar), 8.72 (d, 1H, J 5.25 Hz), 8.74 (dd, 1H, J 6.9, 2.5 Hz);
13C NMR (67.93 MHz, DMSO-d6) d 114.2, 116.5, 120.3,
121.5, 123.3, 126.6, 133.3, 136.2, 138.4, 141.2, 145.2,
152.2, 153.1, 153.8 (23C, Ar-C); Anal. Found: C, 79.72;
H, 4.05; N, 16.18. Calc. for C23H14N4: C, 79.75; H, 4.07;
N, 16.17%. MS (ESI): (M+)at m/z 346.
12. Chan, K. P.; Yang, H.; Hay, A. S.; J. Polymer Sci. 1996, 34,
1923.
13. Kumar, A.; Rajput, C. S.; Eur. J. Med. Chem. 2009, 44, 83.
14. Spasov, A. A.;Yozhitsa, I. N.; Bugaeva, L. I.;Anisimova, V. A.;
Pharm. Chem. J. 1999, 33, 232.
15. Alexandre, F.; Berecibar, A.; Wrigglesworth, R.; Besson, T.;
Tetrahedron 2003, 59, 1413.
16. Alagarsamy, V.; Giridhar, R.; Yadav, M. R.; Revathi, R.;
Ruckmani, K.; Clercq, E. D.; Indian J. Pharm. Sci. 2006, 68,
532.
6-(3-Pyridyl)benzo[4,5]imidazo[1,2-c]quinazoline (20)
Yield 73%; mp 244-246 °C; IRnmax/cm-1: 1635, 1610,
17. Jindal, D. P.; Bhatti, R. S.; Ahlawat, S.; Gupta, R.; Eur. J. Med.
Chem. 2002, 37, 419.
1
1580, 1530, 1457, 1380, 775, 742, 731; H NMR (400
MHz, DMSO-d6) d 6.65 (d, 1H, Ar, J 8.2 Hz), 6.82 (d,
1H, Ar, J 8.4 Hz), 6.83 (t, 1H, Ar, J 7.4 Hz), 7.11-8.12
(m, 7H, Ar), 8.61 (dd, 1H, J 6.9, 2.5 Hz) 8.95 (s, 1H, Ar);
13C NMR (67.93 MHz, DMSO-d6 ) d 113.5, 119.6, 120.7,
123.3, 126.2, 130.3, 132.6, 137.2, 142.2, 146.7, 149.4,
150.1, 152.1 (19C, Ar-C); Anal. Found: C, 77.01; H, 4.05;
N, 18.90. Calc. for C19H12N4: C, 77.01; H, 4.08; N, 18.91%.
MS (ESI): (M+) atm/z 296.
18. Sircar, J. C.; Capiris, T.; Kesten, S. J.; Herzig, D. J.; J. Med.
Chem. 1981, 24, 735.
19. Zhang, Y.; Chen, Z.; Lou, Y.; Yu, Y.; Eur. J. Med. Chem. 2009,
44, 448.
20. Rashood, S. T. A.; Aboldahab, I. A.; Nagi, M. N.; Abouzeid,
L. A.; Aziz, A. A. M. A.; Hamide, S. G. A.; Youssef, K. M.;
Obaid, A. M. A.; Subbagh, H. I. E.; Bioorg. Med. Chem. 2006,
14, 8608.
21. Hennequin, L. F.; Allen, J.; Breed, J.; Curwen, J.; Fennell, M.;
Green, T. P.; Brempt, C. L.; Morgentin, R.; Norman, R. A.;
Oliver, A.; Otterbein, L.; Ple, P. A.; Warin, N.; Costello, G.;
J. Med. Chem. 2006, 49, 6465.
Supplementary Information
Spectral data of compounds are available free of charge
at http://jbcs.sbq.org.br, as pdf file.
22. Hori, M.; Iemura, R.; Hara, H.; Ozaki,A.; Sukamoto, T.; Ohtaka,
H.; Chem. Pharm. Bull. 1990, 38, 681.
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Received: April 15, 2009
Web Release Date: October 9, 2009

J. Braz. Chem. Soc., Vol. 21, No. 1, S1-S3, 2010.
Printed in Brazil - ©2010 Sociedade Brasileira de Química
0103 - 5053 $6.00+0.00
Synthesis and Antimicrobial Activities of a New Class of
6-Arylbenzimidazo[1,2-c]quinazolines
Rondla Rohini,a Kanne Shanker,a P. Muralidhar Reddyb and Vadde Ravindera*
aDepartment of Chemistry, Kakatiya University, Warangal-506 009, A.P., India
bDepartment of Chemistry, National Dong Hwa University, Hualien, Taiwan
Antibacterial activity
1000 µg mL-1. The plates were allowed to stand for 1 h in
order to facilitate the diffusion of the drug solution. Then
the plates were incubated at 37 °C for 48 h. The zones of
inhibition against all the microorganisms were measured
in millimeters.
Antibacterial testing was performed by cup plate
method.38 Nutrient broth was prepared by dissolving
peptone (0.5%), yeast extract (0.15%), beef extract (0.15%),
sodium chloride (0.36%), and monopotassium phosphate
(0.13%) in distilled water (100 mL). The pH of the solution
was adjusted to 7.2 by adding sodium hydroxide solution
(4%) and the resulting solution was autoclaved for 20 min at
15 psi. One day prior to the experiment, the cultures against
Staphylococcus aureus, Bacillus subtilis, Streptococcus
pyogenes, Salmonella typhimurium, Escherichia coli
and Klebsiella pneumonia were inoculated in nutrient
broth (inoculation medium) and incubated overnight at
37 °C. Nutrient agar medium was prepared by dissolving
peptone (1%), yeast extract (0.6%), beef extract (0.5%),
and sodium chloride (0.5%) in distilled water. The pH of
the solution was adjusted to 7.2 by adding 4% aqueous
sodium hydroxide solution. Agar (2.4%) was then added
and the whole solution was autoclaved for 20 min at 15 psi.
Preliminary screening for ten quinazolines was performed
at fixed concentrations of 1000 µg mL-1. Inoculation
medium containing 24-hours grown culture was added
aseptically to the nutrient medium and mixed thoroughly
to get the uniform distribution. This solution was poured
(25 mL in each dish) into Petri dishes and then allowed to
attain room temperature. Thereafter, six millimeter wide
bores were made on the agar using a borer. The solutions
of test samples were added into each of the bores using
a sterile tip with micropipette. Ampicillin was used as
the standard and DMSO as the solvent control. The test
samples and the standard were tested at a concentration of
Antifungal activity
The antifungal activity of quinazoline compounds
were tested against the pathogenic fungi Aspergillus niger,
Candida albicans, Trichoderma viridae by cup-plate
method.38 Nutrient agar medium was prepared by the same
method as explained under evaluation of antibacterial
activity. One and half day prior to the experiment, the
fungal cultures of Aspergillus niger, Candida albicans and
Trichoderma viridae prepared in the inoculation medium
were incubated at 37 °C for 36 h. The fungal medium was
prepared by dissolving peptone (0.5%), sodium chloride
(0.36%), monopotassium phosphate (0.13%), and glucose
(2%) in distilled water (100 mL). The pH of the solution
was adjusted to 7.2 by adding sodium hydroxide solution
(4%) and the resulting solution was autoclaved for 20 min
at 15 psi. This was cooled to 45-50 °C with gentle shaking.
One and half day, grown cultures were added aseptically
to this medium and mixed thoroughly to get uniform
distribution. The solutions of the test samples and standard
were evaluated for antifungal activity by cup-plate method
at a concentration of 1000 µg. The zone of inhibition was
measured in millimeter for the particular test sample with
each organism at 72 h interval. Ketoconazole was used as
the standard.
*e-mail: ravichemku@rediffmail.com

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Synthesis and Antimicrobial Activities of a New Class of 6-Arylbenzimidazo[1,2-c]quinazolines
J. Braz. Chem. Soc.
Figure S1. 1H NMR spectrum of 6-(3-pyridyl)benzo[4,5]imidazo[1,2-c]quinazoline (20).
Figure S2. 13C NMR spectrum of 6-(3-pyridyl)benzo[4,5]imidazo[1,2-c]quinazoline (20).

Vol. 21, No. 1, 2010
Rohini et al.
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Figure S3. FAB mass spectrum of 6-(3-pyridyl)benzo[4,5]imidazo[1,2-c]quinazoline (20).
N
N
N
H
N
N
m/z 193
m/z 218
N
N
N
N
m/z 296
N
N
N
N
m/z 192
m/z 180
m/z 76
Scheme S1. FAB mass fragmentation pattern of 6-(3-pyridyl)benzo[4,5]imidazo[1,2-c]quinazoline (20).