An efficient route for the synthesis of 3-(4-bromophenyl)-2-phenyl-3,4- dihydro-2 H-benzo[ e ][,32,]oxazaphosphinine, its P-chalcogenides and metal complexes

Article abstract of DOI:10.1080/10426507.2012.717143

2-[(4-bromophenylamino)-methyl]-phenol (1) gave substantially pure 3-(4-bromophenyl)-2-phenyl-3,4-dihydro-2H-benzo[e][1,3,2]- oxazaphosphinine (2) on cyclization with phenyldichlorophosphine in toluene at 0 °C. Reaction of 2 with H₂O₂ in dichloromethane gave selectively 3. P-chalcogenides (4 and 5) were prepared by reacting 2 with elemental S and Se powder in toluene, whereas the tungsten pentacarbonyl complex 6 was prepared by reacting 2 with [W(CO)₅(CH₃CN)] in tetrahydrofuran at 25°C. Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional figures.

Full text of DOI:10.1080/10426507.2012.717143

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An Efficient Route for the
Synthesis of 3-(4-Bromophenyl)-2-
Phenyl-3,4-Dihydro-2H-Benzo[E]
[,32,]Oxazaphosphinine, its P-
Chalcogenides and Metal Complexes
Davender Kumar Shukla a , Manju Rani a & Arif Ali Khan a
a University School of Basic & Applied Sciences, Guru Gobind Singh
Indraprastha University , Dwarka Campus, New Delhi , India
Accepted author version posted online: 09 Aug 2012.Published
online: 22 Jul 2013.
To cite this article: Davender Kumar Shukla , Manju Rani & Arif Ali Khan (2013) An Efficient Route for
the Synthesis of 3-(4-Bromophenyl)-2-Phenyl-3,4-Dihydro-2H-Benzo[E][,32,]Oxazaphosphinine, its P-
Chalcogenides and Metal Complexes, Phosphorus, Sulfur, and Silicon and the Related Elements, 188:8,
1088-1094, DOI: 10.1080/10426507.2012.717143
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Phosphorus, Sulfur, and Silicon, 188:1088–1094, 2013
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2012.717143
AN EFFICIENT ROUTE FOR THE SYNTHESIS OF
3-(4-BROMOPHENYL)-2-PHENYL-3,4-DIHYDRO-2H-
BENZO[E][1,3,2]OXAZAPHOSPHININE, ITS
P-CHALCOGENIDES AND METAL COMPLEXES
Davender Kumar Shukla, Manju Rani, and Arif Ali Khan
University School of Basic & Applied Sciences, Guru Gobind Singh Indraprastha
University, Dwarka Campus, New Delhi, India
GRAPHICAL ABSTRACT
Ar
N
P
H O , DCM
2
2
O
Ar
N
P
-80 °C, 2h
O
Ph
Ar
(3)
S, Se, Toluene
110 °C, 5h
O
Ph
N
(2)
Ph
P
O
X
X= S (4), Se (5)
Abstract 2-[(4-bromophenylamino)-methyl]-phenol (1) gave substantially pure 3-(4-
bromophenyl)-2-phenyl-3,4-dihydro-2H-benzo[e][1,3,2]- oxazaphosphinine (2) on cyclization
with phenyldichlorophosphine in toluene at 0 ◦C. Reaction of 2 with H2O2 in dichloromethane
gave selectively 3. P-chalcogenides (4 and 5) were prepared by reacting 2 with elemental S
and Se powder in toluene, whereas the tungsten pentacarbonyl complex 6 was prepared by
reacting 2 with [W(CO)5(CH3CN)] in tetrahydrofuran at 25 ◦C.
Supplementary materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental
files: Additional figures.
Keywords 2H-benzo[e][1,3,2]oxazaphosphinine; phenyldichlorophosphine; p-chalcogenides;
cyclization; heterocycles
INTRODUCTION
Many important medicines, dyes, and insecticides are found in the series of hetero-
cyclic compounds, called oxazines,1 thiazines,2 and oxazaphosphinine.3 They are mainly
Received 11 May 2012; accepted 27 July 2012.
The authors are thankful to CSIR, New Delhi, for proving financial support.
Address correspondence to Arif Ali Khan, University School of Basic & Applied Sciences, Guru Gobind
Singh Indraprastha University, Dwarka sector-16C, New Delhi 110078, India. E-mail: khanaarif@hotmail.com
1088

COMPLEXES OF SUBSTITUTED OXAZAPHOSPHININES
1089
found in the polycyclic divisions in which other rings, such as the benzene ring, are fused
to the oxazines, thiazine, or oxazaphosphinine rings. Cyclophosphamide containing an ox-
azaphosphinine is a proven alkylating antitumor agent against a broad spectrum of human
cancers including slow-growing solid tumors.4 Organophosphorus heterocycles containing
oxygen and nitrogen in a six-membered ring also have high antitumor activity,5 significant
bioactivity, and outstanding medicinal properties. Therefore, the clinical significance and
the unique conformational and stereochemical aspects of oxazaphosphinines have attracted
much interest in drug design and synthesis.6
Among previous reported processes, Reddy et al.7 has reported the synthesis
of oxazaphosphinine oxides by condensation of 2-[[4-(2-hydroxy-benzylamino)-
phenylamino]methyl]phenol with phosphorousoxychloride. Reddy et al.8 presented the
synthesis and chemoselective ring openining of benzoxazaphosphonones with N-sodium
salt of amino heterocyclics. Keglevich et al.9 has demonstrated the synthesis of substituted
dibenzo[c,e][1,2]oxaphosphorine under microwave conditions in presence of ZnCl2.
Recently, Wagner et al.10 has reported the spectral assignment of Phenanthrene derivatives
based on 6H-dibezo[c,e][1,2]oxaphosphinine 6-oxides by NMR and quantum calculations.
They have discussed the complex P–C and P–H coupling pattern and compared with the
derivatives possessing different chemical environments around the phosphorus atom.
RESULT AND DISCUSSION
The synthesis of benzoxazaphosphinine involves, cyclization of 2-[(4-
Bromophenylamino)-methyl]-phenol11 (1) with Phenyldichlorophosphine in presence of
◦
triethylamine in dry toluene at 0 C to afford 3-(4-Bromophenyl)-2-phenyl-3,4-dihydro-
2H-benzo[e][1,3,2]-oxazaphosphinine (2) (Scheme 1). The P-oxide12 derivative 3 was
selectively prepared by reacting 2 with hydrogen peroxide (H2O2) in dry dichloromethane
Ar
O
N
(E)
H
Ar-NH2
H
MeOH
25 °C
OH
OH
NaBH4
0 °C
Ar
H
HN
Ar
N
P
PhPCl2
Toluene
0 °C
O
Ph
OH
(2)
(1)
Where Ar = 4-BrC6H4
Scheme 1

1090
D. K. SHUKLA ET AL.
Ar
O
N
P
H O , DCM
2
2
Ar
N
P
-80 °C, 2h
O
Ph
Ar
(3)
S, Se, Toluene
110 °C, 5h
O
Ph
N
(2)
Ph
P
O
X
X= S (4), Se (5)
Scheme 2
◦
at −80 C (Scheme 2). The P-chalcogens13 4 and 5 were prepared by reacting 3-(4-
Bromophenyl)-2-phenyl-3,4-dihydro-2H-benzo[e][1,3,2]oxazaphosphinine with elemental
◦
sulfur and selenium powder in dry toluene at 110 C, respectively (Scheme 2). Tung-
sten pentacarbonyl complex 6 was prepared by reacting 2 with [W(CO)5CH3CN] in
tetrahydrofuran at 25 ◦C and purified by recrystallization with diethyl ether (Scheme 3).
All the compounds exhibited characteristic IR absorption bands for P O, P S,
and P Se functional groups in the normal region 1251.7, 673.1, and 584.4 cm−1 show-
ing that they are not involved in hydrogen bonding. Characteristic absorption bands for
P–O–(Car) and (P)–O–C(ar) stretching vibrations were observed in the region 999–935
and 1190–1150 cm−1 respectively.14 Tungsten pentacarbonyl complex shows character-
istic absorption bands for –CO stretching vibrations in the region 1928.7, 1996.2, and
2077.2 cm−1
.
1
In the H NMR spectra, the aromatic protons resonated as multiples in the re-
gion 6.87–7.85. Methylene protons resonate as multiplets at δ 4.09–4.83 indicating their
nonequivalence and coupling with phosphorus in the six-membered chair-like conforma-
tion of the benzoxazaphosphinine system. The 13C NMR chemical shifts were interpreted
based on comparison with carbon chemical shifts, additivity rules and intensity of the
signals and coupling with phosphorus. Carbon bonded to endocyclic oxygen gave signals
at 151.7–149.1. The methylene chemical shift appears in region 59.3–45.5. The carbonyl
carbons of W(CO)5 were appears in the region 195.1–198.9. The remaining carbon shifts
were observed in the expected regions.
31P NMR chemical shifts for benzoxazaphosphinine, P O, P S, and P Se were
observed at 112.8, 13.4, 76.7, and 82.4 respectively. Coupling constants [1J31P-77Se and
1J183W-31P] of 826.7 and 326.7 Hz respectively are within the usual ranges found.13 GC–MS
of all the compounds exhibited molecular (M+) and characteristic daughter ion peaks at
Ar
Ar
N
N
P
W(CO) CH CN, THF
5
3
Ph
P
25 °C, 6 h
O
Ph
O
W(CO)5
(2)
(6)
Scheme 3

COMPLEXES OF SUBSTITUTED OXAZAPHOSPHININES
1091
their respective expected m/z values. A dominant isotopic effect was observed for all the
compounds because of having bromine atom. A pattern of +1 and +2 molecular mass was
observed in mass fragments.
EXPERIMENTAL
All commercially available reagents were used after suitable purification and re-
crystallization. Melting points are uncorrected. Fourier Transform Infra Red (FTIR) spectra
were obtained using KBr pellets on Shimadzu FTIR-8700. Carbon, hydrogen, and nitrogen
(CHN) were analyzed on a EURO EA 3000 Elemental analyzer. 1H, 13C, and 31P NMR spec-
tra were recorded on a Bruker AV300 MHz spectrophotometer at 300, 75, and 121.5 MHz
respectively in CDCl3 solution with TMS as internal and 85% Phosphoric acid as external
standard. The chemical shifts are reported in ppm. Chemical shifts are designated using
the following abbreviations: s = singlet, d = doublet, t = triplet, and m = multiplet. Mass
spectra were recorded on Agilent/ Shimadzu GCMS QP2010plus instrument, equipped
with flame ionization detector (FID) system and fused-silica capillary columns (30 m,
0.25 mm i.d., film thickness 0.25 μm, Restek, France), Rtx-5 (95% dimethyl/5% diphenyl
polysiloxane). All solvents were distilled and purified by standard procedures. TLC was
performed on plates coated with silica gel 60 with F254 indicator; column chromatography
was carried out on silica gel 60 (60–120 mesh).
Synthesis of 2-[(4-Bromophenylamino)-methyl]-phenol (1)11
2-[(4-Bromo-phenylamino)-methyl]-phenol was prepared by reacting salicyldehyde
(12.2 g, 0.10 mole) with p-bromoaniline (17.2 g, 0.10 mole) in methanol at room tempera-
ture. The mixture was stirred at 25 ◦C for 60 min and poured into ice water. The separated
product was collected by filtration and recrystallized with methanol. The re-crystallized
Schiff base was dissolved in methanol; sodium borohydride (9.5 g, 0.25 mol) was added
lot wise at 0 ◦C over a period of 30 min. The contents were further stirred for 3 h at 25 ◦C.
The solvent was removed under vacuum, added water to precipitate the product. Filter the
crystallized product and wash with water to get crude product. The crude product thus
obtained was recrystallized with methanol to get 1 as white crystalline solid. Yield 22.5 g
(81.0%), mp 125–126 ◦C.
Synthesis of 3-(4-Bromophenyl)-2-phenyl-3,
4-dihydro-2H-benzo[e][1,3,2]- oxazaphosphinine (2)
Under a nitrogen atmosphere, solution of phenyldichlorophosphine (0.36 g, 2 mmol)
in dry toluene (20 mL) was added drop wise to a cooled (0 ◦C) solution of 2-[(4-
Bromophenylamino)-methyl]-phenol (0.56 g, 2 mmol) and triethylamine (0.58 mL, 4 mmol)
in dry toluene (40 mL). After addition, the reaction mixture was stirred for an additional 2 h
at 20 ◦C. The salt thus formed was removed by separation under nitrogen and the solvent
was removed under reduced pressure to obtain semi solid product. The product thus ob-
tained was purified by low temperature column chromatography (SiO2, 0 ◦C, Hexane: THF;
98:2). Evaporation of the solvents of the second fraction and re-crystallization from diet◦hyl
◦
ether at 5 C yielded 2 as white crystalline solid. Yield 0.27 g (36%); mp 118–119 C.
31P NMR (121.5 MHz, CDCl3): δ 112.8; FTIR (cm−1) 979.8, 1153.4 (P–O–Caromatic); 1H
NMR (300 MHz, CDCl3): δ 4.26–4.49 (m, 2H, ArCH2N), 6.68–7.67 (m, 13H, aromatic);
13C NMR (75 MHz, CDCl3): δ 45.7, 114.7, 121.2, 121.4, 122.2, 125.6, 127.6, 128.3, 128.8,
129.0, 129.4, 130.0, 130.8, 132.1, 132.3; GC–MS m/z: 383.00, Mass fragments, 199.95

1092
D. K. SHUKLA ET AL.
(43.5), 201.95 (40.6), 303.10 (39.0), 382.05 (93.7), 383.05 (32.8), 384.05 (100.0), 385.00
(33.4); Elemental analysis Calculated for C19H15BrNOP: C, 59.40; H, 3.94; N, 3.65. Found:
C, 59.38; H, 3.87; N, 3.57.
Synthesis of 3-(4-Bromophenyl)-2-phenyl-3,4-dihydro-benzo[e][1,3,2]-
oxazaphosphinine-2-oxide (3)
Under a nitrogen atmosphere, To a precooled dichloromethane solution of 3-
(4-Bromophenyl)-2-phenyl-3,4-dihydro-2H-benzo[e][1,3,2]oxazaphosphinine (0.79 g,
2 mmol) at −80 ◦C, H2O2 solution (0.34 mL, 3 mmol) was added drop wise and stirring was
continued for 30 min at −80 ◦C and 1 h at 25 ◦C. The solvent was removed under reduced
pressure and the product was separated by low-temperature column chromatography
◦
(SiO2, 0 C, Hexane: THF; 98:2). Evaporation of the solvents of the second fraction and
◦
re-crystallization from diethyl ether at 5 C yielded 3 as off white crystalline material.
Yield 0.60 g (74%); mp 124–125 ◦C. 31P NMR (121.5 MHz, CDCl3): δ 13.4; FTIR (cm−1
)
1
1251.7 (P O); H NMR (300 MHz, CDCl3): δ 4.50–4.69 (m, 2H, ArCH2N), 7.05–7.62
(m, 13H, aromatic); 13C NMR (75 MHz, CDCl3): δ 51.1, 118.9, 124.3, 124.8, 125.6,
126.7, 128.5, 128.7, 129.5, 130.6, 131.5, 131.7, 132.2, 132.7, 149.5; GC-MS m/z: 399.00,
Mass fragments, 77.05 (28.5), 167.10 (49.7), 243.00 (20.8), 244.00 (100.0), 398.95
(79.2), 399.95 (51.8), 400.95 (75.6), 401.95 (16.0); Elemental analysis Calculated for
C19H15BrNO2P: C, 57.02; H, 3.78; N, 3.50. Found: C, 57.00; H, 3.73; N, 3.41.
Synthesis of 3-(4-Bromophenyl)-2-phenyl-3,4-dihydro-benzo[e][1,3,2]-
oxazaphosphinine-2-sulfide (4)
Under a nitrogen atmosphere, solution of 3-(4-Bromophenyl)-2-phenyl-3,4-dihydro-
2H-benzo[e][1,3,2]oxazaphosphinine (0.39 g, 1 mmol) and elemental sulfur (0.32 g,
◦
10 mmol) in toluene 20 mL was heated at 110 C for 5 h. The resulting dark brown
solution was filtered hot under nitrogen and concentrated under reduced pressure. The
crude product thus obtained was separated by low-temperature column chromatography
◦
(SiO2, 0 C, Hexane: THF; 98:2). Evaporation of the solvents of the second fraction and
◦
re-crystallization from diethyl ether at 5 C yielded 4 as yellow crystalline solid. Yield
0.20 g (48%); mp 116–117 ◦C. 31P NMR (121.5 MHz, CDCl3): δ 73.7; FTIR (cm−1) 673.1
(P S); 1H NMR (300 MHz, CDCl3): δ 4.52–4.81 (m, 2H, ArCH2N), 7.04–7.88 (m, 13H,
aromatic); 13C NMR (75 MHz, CDCl3): δ 51.9, 119.2, 119.3, 124.1, 126.7, 127.5, 127.6,
128.4, 128.6, 129.4, 131.4, 131.5, 132.1, 132.6, 149.3; GC–MS m/z: 414.9, Mass frag-
ments, 199.85 (18.3), 303.05 (42.7), 381.90 (100.0), 382.95 (22.8), 383.95 (93.1), 384.95
(20.8), 414.90 (18.9), 416.90 (19.0); Elemental analysis Calculated for C19H15BrNOPS: C,
54.82; H, 3.63; N, 3.36. Found: C, 54.36; H, 3.73; N, 3.38.
Synthesis of 3-(4-Bromophenyl)-2-phenyl-3,4-dihydro-benzo[e][1,3,2]-
oxazaphosphinine-2-selenide (5)
Under a nitrogen atmosphere, solution of 3-(4-Bromophenyl)-2-phenyl-3,4-dihydro-
2H-benzo[e][1,3,2]oxazaphosphinine (0.39 g, 1 mmol) and elemental selenium powder
◦
(0.79 g, 10 mmol) in toluene (20 mL) was heated at 110 C for 5 h. The resulting dark
brown solution was filtered while hot under nitrogen and concentrated under reduced
pressure. The crude product thus obtained was purified by re-crystallization from diethyl

COMPLEXES OF SUBSTITUTED OXAZAPHOSPHININES
1093
ether at 5 ◦C yielded 5 as orange crystalline solid. Yield 0.19 g (42%); mp 132—133 ◦C.
31P NMR (121.5 MHz, CDCl3): δ 82.4 (s, 1JP-Se = 876.7 Hz); FTIR (cm−1) 584.4 (P Se);
1H NMR (300 MHz, CDCl3): δ 4.39–4.83 (m, 2H, ArCH2N), 6.88–7.85 (m, 13H, aromatic);
1H –Depth: δ 51.7 (s, 2H, ArCH2N); 13C NMR (75 MHz, CDCl3): δ 51.8, 119.2, 119.3,
124.1, 124.3, 126.8, 127.8, 128.3, 128.5, 129.3, 131.6, 131.8, 132.0, 132.9, 149.9; GC-MS
m/z: 463.0, Mass fragments, 199.95 (30.4), 202.00 (27.9), 303.15 (39.1), 382.10 (100.0),
383.15 (23.6), 384.10 (94.1), 385.15 (23.9), 463.05 (5.2); Elemental analysis Calculated
for C19H15BrNOPSe: C, 49.27; H, 3.26; N, 3.02. Found: C, 49.16; H, 3.23; N, 3.01.
Synthesis of 3-(4-Bromophenyl)-2-phenyl-3,4-dihydro-benzo[e][1,3,2]-
oxazaphosphinine-W(CO)5 complex (6)
Under a nitrogen atmosphere, solution of 3-(4-Bromophenyl)-2-phenyl-3,4-dihydro-
2H-benzo[e][1,3,2]oxazaphosphinine (0.38 g, 1 mmol) ◦and W(CO)5CH3CN (0.40 g,
1.1 mmol) in 20 mL tetrahydrofuran was stirred at 25 C for 6 h. The resulting dark
brown solution was filtered under nitrogen and concentrated under reduced pressure. The
crude product thus obtained was separated by low-temperature column chromatography
(SiO2, 0 ◦C, Hexane: diethyl ether; 98:2). Evaporation of the solvents of the second frac-
tion and re-crystallization from diethyl ether at 5 ◦C yielded 6 as off white crystalline solid.
Yield 0.54 g (76%); mp 112–113◦C. 31P NMR (121.5 MHz, CDCl3): δ 125.5 (s, 1JP-W
=
326.7 Hz); FTIR (cm−1) 1928.7, 1996.2, and 2077.2 (CO); 1H NMR (300 MHz, CDCl3): δ
4.09–4.67, (m, 2H, ArCH2N), 6.75–7.67 (m, 13H, aromatic); 13C NMR (75 MHz, CDCl3):
δ 51.7, 119.6, 121.3, 121.8, 121.9, 123.1, 127.4, 128.3, 128.9, 130.6, 130.8, 132.9, 140.7,
141.4, 146.4, 151.6, 195.2, 195.3, 198.5, 198.9; GC-MS m/z: 383.00, Mass fragments,
77.05 (22.1), 107.00 (21.0), 122.05 (21.5), 155.00 (21.2), 157.00 (20.5), 199.90 (100.0),
201.90 (98.7), 306.00 (43.1), 308.00 (43.9), 382.05 (37.2), 383.05 (78.3), 384.05 (49.9),
385.05 (75.5); Elemental analysis Calculated for C24H15BrNO6PW: C, 40.71; H, 2.14; N,
1.98. Found: C, 40.37; H, 2.10; N, 1.89.
CONCLUSION
Triethylamine promoted low-temperature cyclization of 2-[(4-Bromophenylamino)-
methyl]-phenol with Phenyldichlorophosphine gave substantially pure 3-Aryl-2-phenyl-
3,4-dihydro-2H-benzo[e][1,3,2] oxazaphosphinine, 2-oxide, P-chalcogenides, and tun-
gusten complex on further reaction with DMSO, elemental S and Se powders and with
W(CO)5. These novel heterocycles contain exocyclic C–O–P=X and endocyclic O–P–N
bond systems are not reported so far and are likely to posses remarkable stability and
biological activity, which ultimately have better prospects in the medicinal world.
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