Chemistry of phosphorus ylides 31: Reaction of azidocoumarin with active phosphonium ylides, synthesis and antitumour activities of chromenones

Article abstract of DOI:10.1007/s12039-013-0496-5

The reaction of 4- azidochromen-2-one (1) with the nucleophilic phosphacumulene ylides 2, 8, and 12 afforded the new heterocyclic triazoles, triazepines, aziridine, pyrrolone containing a coumarin moiety. Cycloaddition reactions took place first to give triazoline 3 and 9. The triazolines rearranged to the triazepines 4, 10, and 13 accompanied by elimination of triphenylphosphine leading to the phosphorus-free triazepines 5, 11, and moreover, aziridine 6 was produced via nitrogen extrusion from the triazoline 3, followed by ring expansion to the pyrrolone 7. On the other hand, the reaction of the azidocoumarin 1 with the phosphallene yield 15 behaves differently and afforded the triazine 17 and azetone 18. The antitumour activity of compounds 3, 4, 6, and 11 was evaluated, in vitro, against (breast: MCF-7 and liver: HPEG2) human solid tumour cell lines. They showed values closed to that recorded by the reference drug doxorubicin. Indian Academy of Sciences.

Full text of DOI:10.1007/s12039-013-0496-5

c
J. Chem. Sci. Vol. 125, No. 6, November 2013, pp. 1419–1428. ꢀ Indian Academy of Sciences.
Chemistry of phosphorus ylides 31: Reaction of azidocoumarin
with active phosphonium ylides, synthesis and antitumour activities
of chromenones
SOHER S MAIGALI, MANSOURA A ABD-EL-MAKSOUD and FOUAD M SOLIMAN∗
Department of Organometallic and Organometalloid Chemistry, National Research Centre,
Dokki, Cairo, Egypt
e-mail: solimanfma2@yahoo.com
MS received 26 April 2012; revised 21 November 2012; accepted 7 December 2012
Abstract. The reaction of 4- azidochromen-2-one (1) with the nucleophilic phosphacumulene ylides 2, 8,
and 12 afforded the new heterocyclic triazoles, triazepines, aziridine, pyrrolone containing a coumarin moiety.
Cycloaddition reactions took place first to give triazoline 3 and 9. The triazolines rearranged to the triazepines
4, 10, and 13 accompanied by elimination of triphenylphosphine leading to the phosphorus-free triazepines
5, 11, and moreover, aziridine 6 was produced via nitrogen extrusion from the triazoline 3, followed by ring
expansion to the pyrrolone 7. On the other hand, the reaction of the azidocoumarin 1 with the phosphallene
yield 15 behaves differently and afforded the triazine 17 and azetone 18. The antitumour activity of compounds
3, 4, 6, and 11 was evaluated, in vitro, against (breast: MCF-7 and liver: HPEG2) human solid tumour cell lines.
They showed values closed to that recorded by the reference drug doxorubicin.
Keywords. Phosphacumulenes; phosphallene ylide; triazoles; triazepines; triazine-phosphanylidenes
and antitumour activity.
1. Introduction
the development of effective clinical anticancer and
anti HIV drugs.
Coumarin and its derivatives are found in many plants
and exhibit various biological activities.1 They have
long been recognized to possess antiinflammatory,
antioxidant, antiallergic, hepatoprotective, antithrom-
botic, antiviral and anticarcinogenic activities.2–5 More-
over, coumarins have important effects in plant bio-
chemistry and physiology, acting as enzyme inhibitors
and precursor of toxic substances. In addition, these
compounds are involved in the actions of plant growth
hormones and growth regulators, the control of respi-
ration, photosynthesis as well as defense against infec-
tion.2,6 In recent years nitrogen heterocycles containing
a coumarin nucleus have received increasing attention
due to their potential biological properties and conside-
rable effects have been undertaken to exploit synthetic
routes to these compounds.4–9 The biological impor-
tance of coumarin and triazole prompted us to syn-
thesize new triazole derivatives containing coumarin
backbone, which would be favourable in achieving
some specificity of pharmacological action in view of
2. Experimental
2.1 Chemistry
Melting points were determined with an electrother-
mal digital melting point apparatus (Electro-thermal
Engineering Ltd., Essex, United Kingdom). The IR
spectra were recorded in KBr disks on a Pye Uni-
cam SP 3300 and Shimadzu FT IR 8101 PC Infrared
Spectrophotometers (Pye Unicam Ltd. Cambridge,
England and Shimadzu, Tokyo, Japan, respectively).
1H and 13C spectra were obtained from a Jeol ECA
500 MHz NMR Spectrometer (Tokyo, Japan) using
deuterated dimethylsulphoxide (d6-DMSO) as a sol-
vent and (TMS) as an internal reference at 500 and
125 MHz, respectively and 31P NMR spectra were
obtained from a Jeol ECA 500 MHz NMR spectrome-
ter at 200 MHz. Mass spectra (EI-MS) were obtained
at 70 eV with A Finnigan MAT SSQ 7000 spectro-
meter (England). Elemental analyses (C, H, N) results
were recorded with Elementar Vario EL Germany
∗For correspondence
1419

1420
Soher S Maigal et al.
When the reaction of (N-phenyliminovinylidene)-
(Germany), phosphorus was measured by spectrophoto-
metric methods and all of them agreed satisfactory with triphenylphosphorane 2 (377 mg, 1 mmol,) and 4-
the calculated values. The reported yields are of pure azidochromen-2-one 1 (187 mg, 1 mmol), was repeated
isolated materials obtained by column chromatography in boiling toluene (40 mL) for 8 h, evolution of N2
silica gel 60 (Merck).
bubbles was observed. Toluene was distilled off under
reduced pressure and the residue was subjected to
silica gel column chromatography using petroleum
ether (60–80◦C)/ ethyl acetate as eluent (65:35, v/v), to
give two products 6 and 7.
2.1a Reaction of (N-phenyliminovinylidene)triphenyl-
phosphorane 2 with 4-azido chromen-2-one (1): A
solution of (N-phenyliminovinylidene) triphenylphos-
phorane 210 (377 mg, 1 mmol) in 20 mL of tetrahy-
drofuran, was added drop by drop with stirring at 2.1e 4-[2-(Phenylimino)-3-(triphenyl-λ5-phosphany-
room temp, to a solution of 4-azidochromen-2-one 111 lidene)aziridin-1-yl]-2H–chromen 2-one (6): Yield,
(187 mg, 1 mmol) in 20 mL of tetrahydrofuran (THF). 321 mg (60 %), pale yellow crystals, m.p.: 132–134 ◦C,
The reaction mixture was stirred for 10 h during which IR (KBr,ꢀν, cm−1): 1648 (C=O, lactone), 1600 (C=N),
the colour changed from white to pink (the progress 1526 (C=P), 1439, 1392 (P-aryl). 1H NMR (500 MHz,
13
of the reaction was monitored by TLC). THF was dis- d6-DMSO, δ, ppm) 6.93–7.74 (m, 25H, Ar H);
C
tilled off under reduced pressure and the residue was NMR (125 MHZ , d6-DMSO, δ, ppm): 164.35 (C=N),
chromatograp◦hed on silica gel column using petroleum 159.65 (C=O, lactone), 153.83 (C=P); 31P NMR: δ
ether (60–80 C): ethyl acetate (50:50, v/v) as eluent. 9.74 ppm.13 MS m/z 508 [M-CO]+. Analysis for
Three products 3, 4 and 5 were isolated along with C35H25N2O2P (536.5): Calcd. C, 78.35; H, 4.70; N,
triphenylphosphine (m.p. and mixed m.p. 78 ◦C).
5.22; P, 5.77. Found: C, 78.83; H, 4.95; N, 5.02; P, 6.00.
2.1f 3-(Phenylimino)-2-(triphenyl-λ5-phosphanyli-
dene)-2,3-dihydrochromeno[4,3-d]pyrrol-4-(1H)-one
(7): Yield, 107 mg (20 %), colourless crystals, m.p.:
271–273 ◦C. IR (KBr,ꢀν, cm−1): 3423 (NH), 1738
(C=O, lactone), 1597 (C=N), 1565 (C=P), 1493, 1465
2.1b 4-[5-(Phenylimino)-4-(triphenyl-λ5-phosphany-
lidene)-4,5-dihydro-1H-1,2,3-triazol-1-yl]-2H-chromen-
2-one (3): Yield, 214 mg (38 %), pink crystal, m.p.:
231–233◦C, Analysis for C35H25N4O2P(564.5): Calcd.
C, 74.46; H, 4.46; N, 9.92; P, 5.49. Found: C, 74.64; H,
4.55; N, 9.89; P, 5.99.
1
(P-aryl). H NMR (500 MHz, d6-DMSO, δ, ppm):
6.88–7.56 (m, 24H, Ar H), 10.99 (s, 1H, NH, exchange-
able with D2O). MS m/z 537 [M+H]+: Analysis for
C35H25N2O2P(536.5): Calcd. C, 78.35; H, 4.70; N,
5.22; P, 5.77. Found: C, 78.14; H, 4.79; N, 5.32; P, 5.40.
2.1c 5-(Phenylimino)-4-(triphenyl-λ5-phosphanylidene)-
4,5-dihydrochromeno[4,3-d][1,2,-3]triazepine-6(1H)
one (4): Yield, 118 mg (21%), colorless crystal,
m.p.: 331–333 ◦C, IR (KBr,ꢀν, cm−1): 3445 (NH), 1699
(C=O, lactone), 1601 (C=N), 1524 (C=P), 1438, 1390
(P-aryl). 1H NMR (500 MHZ , d6-DMSO, δ, ppm): 6.93
(s, 1H, NH, exchangeable with D2O), 7.32–7.83 (m,
24H, Ar H); 13C NMR (125 MHZ , d6-DMSO, δ, ppm):
162.03 (C=N), 157.9 (C=O, lactone), 153.30 (C=P).31P
NMR: δ 30.33 ppm.12 MS m/z 535 [M-N2]+. Analysis
for C35H25N4O2P(564.5): Calcd. C, 74.46; H, 4.46; N,
9.92; P, 5.49. Found: C,74.03; H, 4.65; N, 9.84; P, 5.49.
2.1g Reaction of (2-oxovinylidene)triphenylphospho-
rane 8 with 4-azidochromen-2-one (1): A mixture of
(2-oxovinylidene)triphenylphosphorane 814 (302 mg,
1 mmol), and 4-azidochromen-2-one 1 (187 mg,
1 mmol), in toluene (40 mL) was refluxed for 8 h
during which the colour changed to pale yellow. The
precipitate was filtered off and the residue crystallized
from ethanol to give 9. The resulting liquor was dis-
tilled off and the residue was subjected to silica gel
column chromatography using petroleum ether (60–
80 ◦C)/ethyl acetate as eluent (30:70, v/v), to give two
products 10 and 11 in addition to triphenylphosphine
(m.p. and mixed m.p. 78 ◦C).
2.1d 5-(Phenylimino)chromeno[4,3-d][1,2,3]triazepin-
6-(5H)-one (5): Yield,◦ 45 mg (15 %), colorless
crystal, m.p.: 220–222 C, IR (KBr,ꢀν, cm−1): 1730
1
(C=O, lactone), 1600 (C=N). H NMR (500 MHz,
d6-DMSO, δ, ppm): 7.22–7.78 (m, 9H, Ar H), 8.75 (s,
1H, azomethine); MS m/z 301[M-H]+, 273[M-N2]+,
245[M-(N2+CO)]+, 229[M-(N2+CO2)]+. Analysis for
C17H10N4O2(302.2): Calcd. C, 67.55; H, 3.33; N, 18.53.
Found: C, 67.36; H, 3.02; N, 18.72.
2.1h 3-(2-Oxo-2H-chromen-4-yl)-5-(triphenyl-λ5-phos-
phanylidene)-3,5-dihydro-4H-1,2,3-triazol-4-one (9):
Yield, 195 mg (40 %), colourless crystals m.p.: 252–
254 ◦C. IR, (KBr,ꢀν, cm−1): 1718 (C=O, lactone), 1645

Reaction of azidocoumarine and antitumor activities
1421
1
(C=O), 1597 (C=P), 1433, 1395 (P-aryl). H NMR (C=O, lactone), 1597 (C=P), 1480 (P-aryl), 1240
(500 MHz, d6-DMSO, δ, ppm): 7.08–8.30 (m, 20H, Ar (C=S).1H NMR (500 MHz, d6-DMSO, δ, ppm): 7.15–
H) 13C NMR (125 MHZ , d6-DMSO, δ, ppm): 164.10 7.79 (m, 19H, Ar H), 8.37 (s, 1H, NH, exchangeable
(C=O, triazole), 161.40 (C=O, lactone), 154.30 (C=P). with D2O); 13C NMR (125 MHZ , d6-DMSO, δ, ppm):
31P NMR: δ 11.57 ppm. MS m/z = 461 [M-N2]+. 207.53 (C=S), 160.74 (C=O, lactone), 153.73 (C=P);
Analysis for C29H20N3O3P(489.4): Calcd. C, 71.16; H, 31P NMR: δ 13.40 ppm. MS m/z = 477[M-N2]+.
4.12; N, 8.58; P, 6.33. Found: C, 71.64; H, 4.06; N, Analysis for C29H20N3O2PS(505.5): Calcd. C, 68.90;
8.90; P, 6.40.
H, 3.99; N, 8.31; P, 6.13; S, 6.34. Found: C, 68.70; H,
3.44; N, 8.33; P, 6.44; S, 6.05.
2.1i 4-(Triphenyl-λ5-phosphanylidene)-1,4-dihydro-
chromeno[4,3-d][1,2,3]triazepine-5,6-dione(10): Yield,
146 mg (30 %), colourless crystals, M.p.: 228–230 ◦C.
IR (KBr,ꢀν,cm−1): 3425 (NH), 1721 (C=O, lactone),
1647 (C=O, triazepine), 1600 (C=P), 1486, 1482
(P-aryl).1H NMR (500 MHz, d6-DMSO, δ, ppm): 7.37–
7.73 (m, 19H, Ar H), 11.28 (s, 1H, NH, exchangeable
with D2O); 13C NMR (125 MHz, d6-DMSO, δ, ppm):
178.80 (C=O, triazepine), 161.20 (C=O, lactone),
157.40 ppm (C=P); 31P NMR: δ 16.39 ppm. MS m/z =
488[M-H]+. Analysis for C29H20N3O3P (489.4): Calcd.
C, 71.16; H, 4.12; N, 8.58; P, 6.33. Found: C, 71.66; H,
4.16; N, 8.14; P, 6.03.
2.1m 5-Thioxochromeno[4,3-d][1,2,3]triazepin-6(5H)-
one (14): Yield: 65 mg (27 %), colorless crystals,
M.p.: 147–149 ◦C. IR (KBr,ꢀν, cm−1): 1732 (C=O, lac-
1
tone), 1610 (C=N), 1270 (C=S). H NMR (500 MHz,
d6-DMSO, δ, ppm): 7.27–7.57 (m, 4H, Ar H); 8.65
(s, 1H, CH, azomethine); 13C NMR (125 MHz, d6-
DMSO, δ, ppm): 206.96 (C=S), 163.03 (C=N), 159.89
(C=O, lactone). MS m/z 242 [M]+. Analysis for
C11H5N3O2S(243.2): Calcd. C, 54.32; H, 2.07; N,
17.28; S, 13.18. Found: C, 54.02; H, 2.09; N, 17.54;
S, 13.44.
2.1n Interaction of hexaphenylcarbodiphosphorane
(15) with 4-azidochromen-2-one (1): To a solution of
4-azidochromen-2-one 1 (187 mg, 1 mmol), in 20 mL
THF was added, hexaphenylcarbodiphosphorane 15,15
(536 mg, 1 mmol) in 20 mL THF. The reaction mix-
ture was stirred at room temp for 12 h during which the
colour change from colourless to yellow then brown,
and N2 gas was evolved. THF was distilled off under
reduced pressure and the remained residue was chro-
matographed on silica gel using petroleum ether (60–
80◦C): ethyl acetate as an eluent (60:40, v/v), to
give 17, 18 together with triphenylphosphine (m.p. and
mixed m.p. 78 ◦C).
2.1j Chromeno[4,3-d][1,2,3]triazepine-4,6-dione (11):
Yield, 34 mg (15 %), colourless crystals, M.p.: 157–
◦
159 C. IR (KBr,ꢀν, cm−1): 1719 (C=O, lactone), 1653
1
(C=O, triazepine), 1601 (C=N). H NMR (500 MHz,
d6-DMSO, δ, ppm): 7.44–7.67 (m, 5H, Ar H); 13C
NMR (125 MHZ , d6-DMSO, δ, ppm): 186.28 (C=O,
triazepine), 163.27 (C=N), 159.33, (C=O, lactone). MS
m/z = 227 [M]+; 199 [M-N2]+; 171 [M-N2, CO]+; 155
[M-N2, CO2]+. Analysis for C11H5N3O3(227.1): Calcd.
C, 58.16; H, 2.22; N, 18.50. Found: C, 58.16; H, 2.44;
N, 18.94.
2.1k Reaction (2-thioxovinylidene)triphenylphospho-
rane (12) with 4-azidochromen-2-one (1): A solution
of (2-thioxovinylidene)triphenylphosphorane 12 (318 mg,
1 mmol) was added to solution of 4-azidochromen-2-
one 1 (187 mg, 1 mmol), in toluene (40 mL). The
reaction mixture was boiled for 10 h during which the
colour was changed from colourless to dark brown.
Toluene was distilled off and the residue was subjected
to silica gel column chromatography using petroleum
2.1o 4-(1,1,1-Triphenyl-λ5-phosphan-1-ylidene)-1,4-
dihydro-5H-chromeno[4,3-d][1,2,-3]triazin-5-one (17):
Yield, 184 mg (40 %), golden yellow crystals, m.p.:
250–252 ◦C, IR (KBr, ꢀν, cm−1): 3208 (NH), 1641
(C=O, lactone), 1546 (C=P), 1484, 1435 (P-
aryl). 1H NMR (500 MHz, d6-DMSO, δ, ppm):
7.25–7.57 (m, 20H, Ar H+ NH); 31P NMR δ
29.79 ppm.16–18 MS m/z = 462 [M+H]+. Analysis
for C28H20N3O2P(461.4): Calcd. C, 72.88; H, 4.37; N,
9.11; P, 6.71. Found: C, 72.72; H, 4.12; N, 9.15; P, 6.82.
◦
ether (60–80 C)/ ethyl acetate as an eluent (70:30,
v/v), to give two products 13, 14 and triphenylphos-
phine (m.p. and mixed m.p. 78 ◦C).
2.1p 2-(Triphenyl-λ5-phosphanylidene)-1,2-dihydro-
3H-chromeno[4,3-d]azet-3-one (18): Yield, 129 mg
(30 %), colourless crystals, m.p.: 132–134◦C. IR
(KBr,ꢀν, cm−1): 3374 (NH), 1695 (C=O, lactone), 1597
(C=P), 1485, 1437 (P-aryl). 1H NMR (500 MHz,
2.1l 5-Thioxo-4-(triphenyl-λ5-phosphanylidene)-4,5-
dihydrochromeno[4,3-d][1,2,3]-triazepin-6(1H)-one (13):
Yield, 277 mg (55 %), pale brown crystals, m.p.:
243–245 ◦C, IR (KBr,ꢀν, cm−1) : 3367 (NH), 1696

1422
Soher S Maigal et al.
d6-DMSO, δ, ppm): 7.25–7.57 (m, 20H, Ar H + NH). optical density. The IC50 values (the concentrations of
31P NMR: δ 13.45 ppm.19–21 MS m/z = 433 [M]+. thymoquinone required to produce 50% inhibition of
Analysis for C28H20NO2P (433.4): Calcd. C, 77.59; H, cell growth). The experiment was repeated 3 times for
4.65; N, 3.23; P, 7.15. Found: C, 77.40; H, 4.20; N, each cell line.
3.15; P, 6.99.
3. Results and discussion
2.2 Biological screening in vitro cytotoxicity
3.1 Chemistry
2.2a Chemicals: All the chemicals and reagents
As a continuation of our investigations into the
used in this study were of analytical grade and pur-
synthesis of new heterocyclic compounds using
chased from (Sigma Chemical Co., St. Louis, Mo,
active phosphacumulenes and phosphallene,23–28 4-
azidochromen-2-one 1 was selected for the synthesis of
USA): These were used in cryopreservation of cells.
the new triazolo-coumarin derivatives.
2.2b Cells culture: The cells of MCF-7 human
breast cancer and HEPG2 liver carcinoma were main-
tained and grown in RPMI-1640 medium supplemented
with 10% heat inactivated fetal bovine serum (Sigma
Chemical Co., St. Louis, Mo, USA), penicillin and
streptomycin at 37◦C in humidified atmosphere con-
taining 5% CO2.
When compound 1 was allowed to react with
(N-phenyliminovinylidene)triphenylphosphorane 2 in
THF at room temperature, the reaction results in
the formation of three products. A pink crystalline
compound 3 was obtained as a major product.
It was formulated as 4-[5-(phenylimino)-4-(triphenyl-
λ5-phosphanylidene)-4,5-dihydro-1H-1,2,3-triazol-1-yl]-
2H-chromen-2-one 3. Besides, 5-(phenylimino)-4-
(triphenyl-λ5-phosphanylidene)4,5-dihydrochromeno
[4,3-d][1,2,3]triazepin-6(1H)one 4, 5-(phenylimino)-
2.2c In-vitro cytotoxicity assay: For in vitro short
term cytotoxicity evaluation of prepared compounds,
MCF-7 and HEPG2 cells were plated a concentration of
5 × 104–105 cells per well, in complete culture medium
in 96 – well flat-bottomed culture plates (Falcon) for
24 h to assure total attachment. Then various concen-
tration of test compounds were added to the cell sus-
pended in 0.10 ml of phosphate buffered saline (FBS)
(0.20 M, pH 7.4), the control cells without the test com-
pounds were also cultured, then the plate was incu-
bated for 24 h at 40◦C and 72 h at 37◦C, in a humidi-
fied 5% CO2 atmosphere. Cell survival was evaluated at
the end of the incubation period with sulphorhodmine-
B (SRB) colorimetric assay according to Skehan
et al.22 This test is based on the sensitivity of the human
tumour cell lines to thymoquinone was determined by
the SRB assay. SRB is a bright pink aminoxanthrene
dye with two sulphonic groups. It is a protein stains that
binds to the amino groups of intracellular proteins under
mildly acidic conditions to provide a sensitive index of
cellular protein content. After incubation, media were
removed and 50 μl of 0.4% SRB dissolved in 1%
acetic acid solution well were. The wells were then
washed 4 times with 1% acetic acid. The absorbance
was determined photometrically at 564 nm with ELISA
microplate reader (Meter tech. ꢀ 960, USA).
chromeno[4,3-d][1,2,3]triazepin-6-(5H)-one
5
and
triphenylphosphine were isolated from this reaction as
minor products. The reaction can be visualized as a
1,3-dipolar cycloaddition of the bifunctional 4-azido-
chromen-2-one 1 to the nucleophilic phosphorane 2, to
form the triazoline 3. Due to the reactivity of position
3 in the triazoline 3, it undergoes ring expansion29,30 to
the corresponding phosphanylidene triazepine 4. Triph-
enylphosphine is a good leaving group, so Hoffmann
degradation31 of compound 4 afforded the triazepine
5 and triphenylphosphine. Compounds 3–5 were iden-
1
tified by H, 13C, 31P NMR, MS and IR spectra which
1
are in agreement with the proposed structures. The H
NMR of the phosphanylidene triazolyl chromenone
3 showed the H-3 proton as a singlet at δ 6.6 ppm.
The 13C NMR of compound 3, showed signals at δ
164.26 (C=N), 159.56 (C=O, lactone) and 153.88 ppm
(C=P). In the 31P NMR of 3 a signal was observed at
δ 9.74 ppm which is in agreement with a phosphorane
on a 5-membered ring system12,32,33, and in the mass
spectrum, the M+ was found at m/z = 564 (3.13%).
The IR spectrum of compound 3 showed bands at
ꢀν 1664 (C=O, lactone), 1598 (C=N), 1557 (C=P),
1494, 1488 cm−1 (P-aryl).34 The most important
features in the spectroscopic data of the phosphanyli-
1
dene triazepine 4, is that the H NMR spectrum lack
the presence of H-3 proton which appeared in the
starting material 1 at δ 6.22 ppm, and showed the
presence of NH group at δ 6.93, exchangeable with
2.2d Calculation: The percentage of cell survival
was calculated as follows. Survival fraction = OD
(treated cells) / OD (control cells) where (OD) is the

Reaction of azidocoumarine and antitumor activities
1423
D2O. Moreover, a signal at δ 30.33 ppm was observed phosphine from 10 leads to chromeno[4,3-d] [1,2,3]
in its 31P NMR spectrum. When 4-azidochromen- triazepine-4,6-dione 11.
2-one 1 was reacted with (N-phenyliminovinyli-
In addition, the reaction of the azide 1 with (2-
dene)triphenylphosphorane 2, in dry boiling toluene thioxovinylidene)triphenylphosphorane 12 was per-
for 8 h, N2 gas was evolved, and 4-[2-(phenylimino)- formed in boiling toluene for 10 h. The reaction
3-(triphenyl-λ5-phosphanylidene)aziridin-1-yl]-2H-
proceeded with the formation of 5-thioxo-4-(triphenyl-
chromen-2-one 6 and 3- (phenylimino)-2-(triphenyl-λ5-
phosphanylidene)-2,3-dihydrochromeno-[4,3-d]pyrrol-
4(1H)-one 7 were isolated. The triazoline 3, was
formed first by an intermolecular 1,3-dipolar cycload-
dition of the azide 1 to the phosphorane 2, followed by
nitrogen extrusion and ring contraction to the aziridine
6. Formation of aziridines from triazolines is well-
known.35 Rearrangement of the aziridine 6, resulted in
the formation of the pyrrolone 736 (scheme 1).
λ5-phosphanylidene)-4,5-dihydrochromeno[4,3-d][1,2,3]
triazepin-6(1H)-one 13 and 5-thioxochromeno [4,3-
d][1,2,3] triazepin-6(5H)-one 14. Cycloaddtion of the
azide 1 and the thiophosphacumulene 12 gave the phos-
phanylidene triazepine 13, followed by elimination of
triphenylphosphine in order to give the triazepinone 14
(scheme 2).
Furthermore, a novel approach to triazinone and
azetone by an intermolecular [2+3]-addition of the
allylic phosphonium ylide, namely, hexaphenylcar-
bodiphosphorane 15 to the azidocoumarine 1 was
described, too. In this case, two products namely, 4-(1,-
1,1-triphenyl-λ5-phosphan-1-ylidene)-1,4-dihydro-5H-
chromeno[4,3-b][1,2,3]triazin-5-one 17 and 2-(triphen-
yl-λ5-phosphanylidene)-1,2-dihydro-3H-chromeno[4,
3-b]azet-3-one 18 were isolated. The most important
features in the spectroscopic data of the triazinone 17
and azetone 18, is that they show only one signal in
When the reaction of the azide 1 with (2-oxovinyli-
dene)triphenylphosphorane 8 was carried out in boil-
ing toluene for 8 h, three products were formed.
Cycloaddition of the azide 1 and the phosphorane 8,
afforded 3-(2-oxo-2H-chromen-4-yl)-5- (triphenyl-λ5-
phosphanylidene)-3,5-dihydro-4H-1,2,-3-triazol-4-one
9. Ring enlargement of 9 gave 4-(triphenyl-λ5-
phosphanylidene)-1,4-dihydrochromeno-[4,3-d]-[1,2,
3]triazepine-5,6-dione (10). Elimination of triphenyl-
PPh3
N
N
N-Ph
N
N
O
N
O
HN
PPh3
Ph3P-C-C-N-Ph
+
THF/room temp.
2
N-Ph
O
O
3
4
+
N
N
N
N
N
N
N-Ph
+
Ph3P
O
O
O
O
1
5
Ph3P
N-Ph
PPh3
N-Ph
N
O
HN
Toluene
boiling
+ N2
+
O
O
O
6
7
Scheme 1. Formation of compounds 3–7.

1424
Soher S Maigal et al.
PPh3
N
N
O
N
N
O
N
O
HN
PPh3
Ph3P=C=C=O
+
8
O
O
O
9
10
+
N
N
N
N
N
O
N
O
Ph3P
+
O
O
O
1
11
N
N
N
O
N
N
HN
PPh3
Ph3P=C=C=S
S
S
Toluene, boiling
12
+
O
O
O
14
13
Ph3P
+
Scheme 2. Formation of compounds 9–14.
PPh3
N
N
HN
N
N
PPh3
Ph3P=C-PPh3
-Ph3P
N
O
PPh3
15
O
O
O
-N2
17
16
N
N
N
H
N
PPh3
O
O
+
N2
+
Ph3P
O
O
1
18
Scheme 3. Formation of 17 and 18.

Reaction of azidocoumarine and antitumor activities
1425
their 31P NMR at δ 29.79 and δ 13.45 ppm, respectively.
The reaction proceeds by intermolecular cycloaddition,
producing the intermediate phosphanylidene- triaza-
phosphol chromenone 16. Since triphenylphosphine is
a good leaving group, so fragmentation and rearrange-
ment of 16 occurs with the formation of the triazinone
17 and triphenylphosphine. The latter triazinone 17
can loose nitrogen to give the azetone 18 (scheme 3).
Generation of azetes from 1,2,3-triazine derivatives
has been previously observed.37,38 [Physical and spec-
troscopic data are provided in the experimental
section].
Table 1. Effect of the tested compounds on MCF-7 tumuor
cell lines.
Compound
IC50 (μg /ml)
Doxorubicin (st.)
3
4
6
2.97
3.89
4.50
9.22
16.5
11
phine treatment.41–45 Based on these considerations four
of the newly synthesized compounds were screened for
their in vitro cytotoxic and growth inhibitory activities
against human breast carcinoma cell line (MCF-7) and
3.2 Cytotoxic assay
Cancer diseases are a serious threat to health and human carcinoma(HEPG2) liver cell lines, in compari-
development of mankind and the research for effec- son with the activity of the utilized anticancer Doxoru-
tive anticancer agents are important. Considerable bicin (DXR) as a reference drug. However, the cyto-
progress has been made in recent years in the field toxic activities of the tested compounds were expressed
of drug development against different types of cancer. as the median growth inhibitory concentration (IC50)
Moreover, chemotherapy is a major approach for both which is the dose that reduces survival to 50 %. The
localized and metastasized cancers39 and for many screening results are compiled in table 1. According
years coumarin-related compounds have proved to be to the American National Cancer Institute guidelines22
a significant therapeutic potential.40 On the other hand, drugs with IC50 < 30 are active.
it is well-known that compounds containing triph-
From table 1, it is evident that most of the tested
enylphosphine moiety are part of a class of lipophilic compounds show antitumour activities with IC50 values
cationic molecules that accumulate preferentially in ranging from 3.89 to 16.5 μg/mL and reaching strong
mitochondria and inhibit the growth of human and correlation that of DXR (IC50: 2.97 μg/mL) in the case
rodent carcinoma cells in vitro and in animal models. of compound 3 (IC50: 3.89 μg/mL). It is clear from
It shows remarkable activity in a panel of cancer cell the data that the comparison of the cytotoxicity against
line as well as in mouse model of human breast can- MCF-7 cells (figure 1) of prepared compounds has
cer. Moreover, triphenylphosphine-treated mice showed shown that the cells killing potency follows the order
significantly decreased tumour growth. No toxicities or 3 > 4 > 6 > 11. This may be attributable to presence
organ damage were observed following triphenylphos- of the phosphanylidene-triazolyl moiety in its mole-
Figure 1. The surviving fraction as a function of drug concentration for the
reference compared particularly with the other compounds (MCF-7).

1426
Soher S Maigal et al.
cell line. The IC50 after short time exposure was 4.18,
6.10, 6.18 and 14.30 μg/mL for compounds 3, 4, 6
and 11, respectively i.e., the cell killing potency follows
the order, 3 > 4 > 6 > 11 (table 2).
Table 2. Effect of the tested compounds on HEPG2
tumour cell lines.
Compound
IC50 (μg/ml)
Compound 3 was the best compound, exerting a
significant cytotoxicity election (IC50: 4.18 μg/mL)
HEPG2 cells compared with Doxorubicin (IC50:
3.73 μg/mL) (figure 2).
The results show that compounds 3 and 4 are bet-
ter antitumour agents for MCF7 than HEPG2 and com-
pound 11 and compound 6 may conduct to a promising
pharmaco modulation for the discovery of new potential
drugs.
Doxorubicin (st.)
3
4
6
3.73
4.18
6.10
6.18
14.3
11
cular structure, the cytotoxic activity that may inter-
act with DNA by intercalation and inhibition of macro-
molecular biosynthesis. This inhibits the progression of
the enzyme topoisomerase II, which unwinds DNA for
transcription and otherwise stabilizes the topoisomerase
II complex after it has broken the DNA chain for repli-
cation, preventing the DNA double helix from being
resealed and thereby stopping the process of replica-
tion as act Doxorubicin,46 suppressing agent, inhibit the
formation and growth of tumours from initiated cells.47
On the other hand, substitution of the triazole moiety
with the phosphanylidene-triazepinone moiety in one
and the same structure (cf. 4, IC50: 4.5 μg/mL) also
closely related the activity of the standard. The antitu-
mour activity of the phosphanylidene-aziridine deriva-
tives 6 recorded 9.22 μg/mL. On the other side, com-
pound 11 marked 16.5 μg/mL due to the absence of
phosphanylidene moiety in their molecular structures,
and also good result. Therefore, the marked difference
in their activities can be correlated with the difference
in biological activities in different phosphorus and ring
systems.
4. Conclusion
The reaction of 4-azidochromen-2-one (1) with the
phosphacumulene ylides 2, 8, 12 and the phosphallene
ylide 15 represent an expeditious access to new hete-
rocyclic triazoles, triazepines, aziridines, pyrroles and
triazines containing a coumarin moiety. Cycloaddition
reactions took place first to give triazoline adducts like
compounds 3, 9 and triazaphosphol 16. The triazoline
rearranged to the triazepines 4, 10, and 13 accompa-
nied by elimination of triphenylphosphine leading to
the phosphorus-free triazepines 5, 11 and 14. More-
over, aziridine 6 can be eventually produced via nitro-
gen extrusion from the triazolin 3, followed by ring
expansion to the pyrrolone 7. The present evidence
contradicts claim that a singlet nitrene should be an
intermediating in the formation of the aziridine 6 and
pyrrolone 7. On the other hand, the reaction of the
azidocoumarin 1 with the active phosphallene ylide
15 behaves differently and the triazinone 17 and aze-
tone 18 were isolated. Moreover, the difference in the
nucleophilic character and reactivity of the phosphacu-
mulenes 2 > 8 > 12 was noticed.48 Therefore, the
Moreover, the same four compounds 3, 4, 6, 11
were screened for their in vitro cytotoxic and growth
inhibitory activities towards liver carcinoma (HEPG2)
Figure 2. The surviving fraction as a function of drug concentration for the
reference compared particularly with the other compounds (HEPG2).

Reaction of azidocoumarine and antitumor activities
1427
reaction course between the active phosphacumulenes 13. Schmidbauer H, Schier A, Milewski-Mahrla B and
Schubert U 1982 Chem. Ber. 115 722
and phosphallene, is rather dependant on the nature of
the reagents and the reaction conditions. The present
study reports on simple and efficient approaches for
the synthesis of new phosphorus derivatives of triazol-,
triazepin-, aziridin-, and free phosphorus triazepin
chromenone derivatives, especially azepines which rare
class of highly strained compounds.49,50
14. Bestmann H J and Sandmeier D 1975 Angew Chem.
Internt Edn 14: 634, 1976 Chem. Abstr. 84 5070s.
15. Verma S, Athale M and Bokodia M M 1981 Indian J
Chem. 20B 1096
16. Bestmann H J, Schmid G, Sandmeier D and Geismann
Ch 1980 Tetrahedron Lett. 2401.
17. Bestmann H J and Kloeters W 1977 Tetrahedron Lett.
34 79
Many of the new compounds revealed pronounced in
vitro antitumour activities when tested against human
MCF-7 and HEPG2 carcinoma cell lines. The most
promising result against breast carcinoma (MCF-7) was
recorded by the phosphanylidene-triazolyl chromenone
3. It showed IC50 value of (3.89 μg/mL) which is the
closest in value to that recorded by the reference drug
Doxorubicin (IC50: 2.97 μg/mL). Similarly, the cyto-
toxic and growth inhibitory activity of the same com-
pound 3 (IC50: 4.18 μg/mL) was very close to that of the
same reference drug (IC50: 3.73 μg/mL) against human
liver (HPG2) carcinoma cell lines. Moreover, the cyto-
toxic and growth inhibitory activity effect of mentioned
compounds is more significant on liver carcinoma than
breast carcinoma.
18. Johnson A Wm 1966 Ylides chemistry in organic chem-
istry. A series of monographs, A T Blomquist (ed)
London: Academic Press
19. Bestmann H J and Zimmermann R 1972 Organic phos-
phorus compounds Vol. 3, G M Kosolapoff, L Maier
(eds), New York: John Wiley and Sons, Inc. Wiley 1973
Chem. Abstr. 78 84461x
20. Bestmann H J, Schmid G, Sandmeier D and Kisielowski
L 1977 Angew. Chem. 89 275
21. Grim S O, Mc Farlane W and Marks T J 1967 J. Chem.
Commun. 1191
22. Skehan P, Storeng R, Scudiero D, Monks A, McMahon
J, Vistica D, Warren J T, Bokesch H, Kenny S and Byod
M R 1990 J. Natl. Cancer Inst. 82 1107
23. Maigali S S, Abdel-Malek H A and Soliman F M 2010
Egypt J. Chem. 53(2) 315
24. Maigali S S, Said M M, Abd-El-Maksoud M A and
Soliman F M 2008 Monatsh. Chem. 139 495
25. Said M M, Maigali S S, Abd-El-Maksoud, M A and
Soliman F M 2008 Monatsh. Chem. 139 1299
26. Maigali S S, Abd-El-Maksoud M A and Soliman F M
2011 J. Chem. Pharm. Res. 3(4) 713
Acknowledgements
We thank the Cancer Biology Department, National
Cancer Institute, Cairo University for the pharmacologi-
cal evaluation.
27. Soliman F M, Abd-Ella I, Maigali S S and Abd-El-Naim
G 2009 J. Chem. Res. 277
28. Maigali S S, Said M M, Abd-El-Maksoud M A and
Soliman F M 2011 Arch. Pharm. Chem. 344(7) 442
29. Iddon B, Cohn O M, Scriven V, Suschitzky H and
Gallagher P T 2003 Angew. Chem. Inter. 18(12) 900
30. Laatsch H, Erns B P and Hoffmann D 2006 Liebig Ann.
1995(10) 1773
31. Nelson N and Levy R B 1979 J. Catal. 58 485
32. Birum G H and Matthews C N 1967 Chem. Commun.
137
33. Schmidpeter A, Gebler W, Zwaschka F and Sheldrich W
S 1980 Angew. Chem. 92 767 1980 Angew. Chem. Int.
Ed. Engl. 19 722
34. Williams D H and Fleming I 1987 Spectroscopic meth-
ods in organic chemistry; Berkshire, United Kingdom:
Mc Graw-Hill Book Company: Maidenhead p. 55
35. D’hooghe M, Kenis S, Vervisch K, Lategan C, Smith P
J, Chibale K and De Kimpe N 2011 Eur. J. Med. Chem.
46(2), 579
References
1. Sivakumar K, Xie F, Cash B M, Long S, Barnhill H N
and Wang Q 2004 Org. Lett. 6(24) 4603
2. kostova I, Raleva S, Genova P and Argirova R 2006
Bioorg. Chem. Appl. 1
3. Sukdolok S, Solujic S, Vukovic N, Manojlovic N
and Kristic L 2004 J. Serb. Chem. Soc. 69(5) 319
4. Al-Soud Y A, Al-Masoudi I A, Saeed B, Beifub H
and Al-Masoudi N A 2006 Chem. Heterocycl. Commun.
42(5) 583
5. Jung J-C and Park O-S 2009 Molecules 14 4090.
6. Tao L, Zhang L L, Shen S J and Han X P 2001 Chin.
Chem. Lett. 12(9) 763
7. Lutz J F and Zarafshani Z 2008 Adv. Drug Delivery Rev.
60 958
8. Shafran E A, Bakulev V A, Rozin Yu A and Shafran
Yu M 2008 Chem. Heterocyclic Comp. 44(9) 1040
9. Habib P M, Raju B R, Kavala V, Kuo C W and Yao C F
2009 Tetrahedron 65 5799
36. Hu X E 2004 Tetrahedron 60 2701
37. Chambers R D, Tamura M, Shepherd T and Ludman C J
1987 J. Chem. Soc. Chem. Commun. 1699
38. Soliman F M, Said M M and Maigali S S 2005
Heteroatom. Chem. 16(6) 476
39. Surth Y J 2003 Nat. Rev. Cancer 3 768
40. Patela M M, Malia D M and Patel S K 2010 Bioorg.
Med. Chem. Lett. 20(21) 6324
41. Manetta A, Gamboa G, Nasseri A, Podnos Y D, Emma
D, Dorion G, Rawlings L, Carpenter P M, Bustamante
10. Bestmann H J and Schmid G 1975 Ger. Offen. 2409356,
1976 Chem. Abstr. 84 31239
11. Stadlbauer W 1986 Monatsh. Chem. 117(11) 1305
12. Albright T A, Freeman W J and Schweizer E E 1975
J. Am. Chem. Soc. 97 2942

1428
Soher S Maigal et al.
A, Patel J and Rideout D 1996 Gynencol. Oncol. 60(2) 46. Fornari F A, Randolph J K, Yalowich J C, Ritke M K
203 and Gewirtz D A 1994 Mol. Pharmcol. 45(4) 649
42. Melissa M, Divya P, Yumna S, Laleh T, Jinxia D and 47. Hidalgo N, Almirante B and Pahissa A 2009 Clin. Infect.
Nouri N 2010 Plose ONE 5(10) 1 Dis. 48 1166
43. Modica-Napolitano J and Aprille J 2001 Adv. Drug 48. Bestmann H J 1977 Angew. Chem. 89(6) 361, 1977
Deliv. Rev. 49 63 Angew. Chem. Int. Ed. Engl. 16 349
44. Wang J, Yang C, Kim Y, Sreerama S and Cao Q 2007 49. Karney W L and Borden W T 1997 J. Am. Chem. Soc.
J. Med. Chem. 50 5057 119 5061
45. Kim Y, Yang C, Wang J, Wang L and Li Z 2008 J. Med. 50. Wenk H H and Sunder W 2002 Angew. Chem. 114 2873
Chem. 51 2971 2002 Angew. Chem. Int. Ed. 41 2742