Synthesis, spectral, and antimicrobial evaluation of some new 8-membered phosphorus heterocyclic compounds

Article abstract of DOI:10.1007/s00044-010-9425-z

Synthesis of 9-substituted-8, 9 10, 11-tetrahydro- 7H-7, 11-diaza-9λ⁵-phosphacycloocta [d,e] naphthalene- 9-sulfides/selenides (4-13) was accomplished in three steps. 1,8-diamino naphthalene (2) was reacted with tris (bromomethyl) phosphine (1)

Full text of DOI:10.1007/s00044-010-9425-z

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2011) 20:962–967
DOI 10.1007/s00044-010-9425-z
ORIGINAL RESEARCH
Synthesis, spectral, and antimicrobial evaluation of some
new 8-membered phosphorus heterocyclic compounds
•
Arigala Uma Ravi Sankar Sanapalli Subba Reddy
•
•
Gangireddygari Chandra Sekhar Reddy
•
Mudamala Veera Narayana Reddy
Chamarthi Naga Raju
Received: 10 December 2009 / Accepted: 2 September 2010 / Published online: 17 September 2010
ꢀ Springer Science+Business Media, LLC 2010
Abstract Synthesis of 9-substituted-8, 9 10, 11-tetrahy-
dro-7H-7, 11-diaza-9k5-phosphacycloocta [d,e] naphtha-
lene-9-sulfides/selenides (4–13) was accomplished in three
steps. 1,8-diamino naphthalene (2) was reacted with tris
(bromomethyl) phosphine (1) in the presence of triethyl-
amine in dry tetrahydrofuran (THF) under N2 atmosphere
to form the corresponding intermediate (3). It was con-
verted to the corresponding sulfide (4) and selenide (5) by
the reaction with sulfur and selenium, respectively. The
intermediates 4 and 5 were reacted with two achiral alco-
hols and two achiral amines to obtain the title compounds
(6–13). The structures of the title compounds were estab-
lished by elemental analysis and spectral data (IR, 1H, 13C,
31P NMR, and FAB mass). The antimicrobial activity of
these compounds was evaluated and they exhibited sig-
nificant activity.
Introduction
Organophosphate moiety is an important pharmacophore in
agricultural and pharmaceutical chemistry (Demir et al.,
1996). Phosphocin/phosphepin and their related derivatives
containing this group represent an important class of pes-
ticides, antibiotics, herbicides and antiviral agents (Vasu
Goverdhana Reddy et al., 2002). Some of them are well
known for their insecticidal activities (Schrader, 1957) and
are known to degrade hydrolytically and enzymatically to
non-toxic residues. Discovery of their fungicidal properties
also promotes developing chemically—the new chiral
phosphorus ligands play vital role in asymmetric synthesis
of—various intermediates in organic synthesis (Chi and
Zhang, 2002; Reetz and Mehler, 2000; Ojima, 2000;
Nayori, 1994; Li et al., 2001). Keeping in view the
importance of eight-membered organophosphorus hetero-
cyclic compounds, we herein report the synthesis and
spectral characterization and antimicrobial activity of the
novel heterocyclic compounds containing achiral alcohols
and achiral amines.
Keywords 1, 8-diamino naphthalene Á
Tris (bromomethyl) phosphine Á Phosphocins Á
Antimicrobial activity
Materials and methods
General procedure
A. Uma Ravi Sankar (&)
Department of Nano-Materials, Graduate School
of Science and Technology, Shizuoka University,
Hamamatsu 432-8561, Japan
Melting points were determined in open capillary tubes on
a Mel-temp apparatus and were uncorrected. Micro-anal-
ysis was performed on Heraeus Vario EL III Carlo Ebra
1108. IR Spectra were recorded in as KBr discs on a
e-mail: ravi_aregala@yahoo.co.in
1
Nicolet 380 FT-IR spectrophotometer. H and 13C NMR
A. Uma Ravi Sankar Á S. Subba Reddy Á
G. Chandra Sekhar Reddy Á M. Veera Narayana Reddy Á
C. Naga Raju
Department of Chemistry, Sri Venkateswara University,
Tirupati 517 502, India
spectra were recorded on a Bruker AMX 400 MHz spec-
1
trometer operating at 400 MHz for H, 100 MHz for 13C,
and 161.9 MHz for 31P. The compounds were dissolved in
123

Med Chem Res (2011) 20:962–967
963
1
DMSO-d6. The H and 13C and chemical shifts were ref-
methane (0.78 g, 0.005 mol) in 10 ml of dry THF was
added drop wise at 10–15ꢁC after completion of the addi-
tion, the reaction temperature raised to room temperature
and continued stirring until the magnesium metal was
dissolved to form bromo methyl magnesium bromide. It is
further reacted with PBr3 to form tris (bromo methyl)
phosphine and magnesium bromide salt. The magnesium
bromide salt was separated by filtration under N2 atmo-
sphere and the solvent was distilled off to get tris (bro-
momethyl) phosphine (1) (Chance et al., 1967).
erenced to tetramethylsilane and 31P chemical shifts to
85% H3PO4. Mass spectra were recorded on a Jeol SX 102
DA/600 Mass spectrometer using Argon/Xenon (6 keV,
10 mA) as the FAB gas.
Chemistry
The preparation of tris (bromomethyl) phosphine (1),
compounds 3–5 and synthetic route for the preparation of
the title compounds 6–13 is depicted in Scheme 1.
Synthesis of 9-bromomethyl-7, 8, 10, 11-tetrahydro-7,
11, diaza-9k5-9-phospha-cycloocta [d, e] naphthalene-
9-oxide (3)
Preparation of tris (bromomethyl) phosphine (1)
Because of the sensitivity of the reagents and products to
moisture and oxygen, all manipulations were performed in
an anhydrous inert nitrogen atmosphere. In a dry 100 ml
three necked round bottomed flask fitted with dropping
funnel, a reflux condenser attached to a calcium chloride
tube, an inlet for dry nitrogen and a thermometer reaching
close to the bottom in the flask were placed magnesium
turnings (0.12 g, 0.005 mol) and dry THF (5.0 ml). The
reaction mixture was kept under stirring and dibromo
To a cooled (5ꢁC) and stirred solution of 1, 8-diamino-
naphthalene (2, 0.69 g, 0.005 mol) and triethyl amine
(1.01 g, 0.01 mol) in 10 ml of dry THF under nitrogen gas,
a solution of tris (bromomethyl) phosphine (1, 1.35 g,
0.005 mol) in 10 ml of dry THF was added over a period of
20 min. After completion of the addition, the temperature
of the reaction mixture was raised to room temperature and
stirred for 1 h to form the intermediate 3. The progress of
the reaction was judged by the TLC analysis. After
Scheme 1 Reagents and
ii
i
+ 3 Mg
Br
Br
3 Br-CH2 MgBr
(Br-CH2)3P + 3Mg Br2
conditions: (i) N2/THF,
10–15ꢁC; (ii) PBr3, rt; (iii) N2
atm/THF, Et3N, rt; (iv) S/Se,
THF, reflux, 2 h; (v) THF, Et3N,
30–35ꢁC
3
1
H
NH2
N
iii
CH2
+ (Br-CH2)3P
P
Br
+ 2Et3 NHBr
NH2
N
H
3
2
1
iv
6
H
H
N
8
N7
4
3
R
R
v
CH2
R'
7a
P
CH2
P
Br
11
N
12
H-R'
N
H
10
H
1
6-9: R = S
10-13: R = Se
4: R = S
5: R = Se
Compd.
6/10
R'
Compd.
R'
CH2OH
H
CH3
O
8/12
N
CH3
CH3
CH3
H
CH3
O
7/11
9/13
N
C6H5
C6H5
123

964
Med Chem Res (2011) 20:962–967
Antimicrobial activity
completion of the reaction, the triethylamine HBr salt was
removed by filtration and the concentration of filtrate
yielded the crude product which was subjected to the next
reaction without further purification.
The compounds 4–13 were screened by disc diffusion
method (Umamaheswari Devi et al., 2000; Colle et al., 1989)
for their antimicrobial activity against the fungi, Aspergillus
niger and Helminthosporium oryzae and bacteria, Esche-
richia coli and Staphylococcus aureus by comparing with
standard fungicide Griseofulvin and standard bactericide
penicillin at three different concentrations (100, 50, and
25 ppm) and the results are presented in Tables 5 and 6.
Synthesis of 9-bromomethyl-8, 9, 10, 11-tetrahydro-
7H-7, 11-diaza-9k5-phospha-cycloocta [d,e]
naphthalene 9-sulfide/selenide (4/5)
The intermediate 3 in THF was cooled to 5ꢁC, sulfur
powder/selenium metal was added to it and heated slowly
up to gentle reflux with stirring and continued for 2 h for
the completion of the reaction as indicated by TLC anal-
ysis. The solvent was removed in a rota-evaporator and the
residue was extracted with ethyl acetate. The extract after
drying over anhydrous MgSO4 was removed in a rota-
evaporator. The obtained crude products (4 and 5) were
purified by column chromatography (hexane-ethylacetate
2:1) to yield 4 (59%) and 5 (70%) with m.p. 180–182ꢁC
and 156–158ꢁC, respectively.
Results and discussion
Preparation of a few eight-membered phosphonate het-
erocyclic compounds such as 9-substituted-8, 9, 10,
11-tetrahydro-7H-7,11-diaza-9k5-phosphacycloocta [d,e]
naphthalene-9-sulfides/selenides (6–13) was accomplished
in three steps. The synthetic route (Scheme 1) involves the
cyclization of equimolar quantities of 1,8-diamino naph-
thalene (2) with tris (bromomethyl) phosphine (1) in the
presence of triethylamine in dry tetrahydrofuran (THF)
under N2 atmosphere to form the corresponding PIII inter-
General procedure for the preparation of (6–13)
mediate
9-bromomethyl-8,9,10,11-tetrahydro-7H-7,11-
To the intermediate 4 in dry THF, two chiral alcohols
(( )sec-butanol, ( )1-phenyl ethanol) and two chiral
amines (( )1-phenylethyl amine, ( )2-amino-1-butanol)
were added in the presence of triethylamine at 10–15ꢁC
over a period of half an hour. After the addition, temper-
ature of the reaction mixture was slowly raised to 30–35ꢁC
and continued stirring. The progress of the reaction was
monitored by the TLC analysis. After completion of the
reaction, solvent was removed, and the resulting crude
products were recrystallized from 2-propanol to obtain
pure sulfur-based compounds of 6–9. The same procedure
was adopted for the preparation of selenium-based phos-
phorus compounds 10–13.
diaza-9-phospha-cycloocta [d,e] naphthalene (3). It was
converted to the corresponding sulfide (4) and selenide (5)
by the reaction with hydrogen peroxide, sulfur, and sele-
nium, respectively. The compounds 4 and 5 further reacted
with two achiral alcohols and two chiral amines in the
presence of triethylamine in dry tetrahydrofuran to form
the corresponding title compounds (6–13) (Scheme 1).
The physical, elemental analyses, IR, and 31P NMR data
of the compounds 4–13 are given in Table 1. Compounds
4–13 exhibited characteristic P=S/Se stretching frequencies
in the region 757–780 (P=S) and 617–635 (P=Se) cm-1
Characteristic absorption bands for P–C(aliphatic) and N–H
.
Table 1 Physical, IR, and 31P NMR spectral data of the compounds 4–13
Compounds Molecular
formula
m.p. ꢁC
Yield Elemental analysis % found (Calcd.)
%
IR cm-1
NH P=S/Se P–Calip
31P NMR
ppm
C
H
N
4
C13H14BrN2PS
180–182 59
45.72 (45.80) 4.14 (4.18)
40.23 (40.31) 3.64 (3.70)
61.03 (61.10) 6.90 (6.95)
65.90 (65.98) 6.04 (6.08)
8.20 (8.25)
3,315 776
3,348 624
3,379 769
3,388 780
734
739
745
710
714
716
758
747
756
736
42.18
82.45
41.06
45.54
46.21
44.82
83.17
86.29
84.94
87.16
5
C
C
C
C
C
C
C
C
C
13H14BrN2PSe 156–158 70
7.20 (7.25)
8.35 (8.41)
7.30 (7.35)
6
17H23N2OPS
21H23N2OPS
21H24N3PS
172–174 65
154–156 55
145–147 60
154–156 52
142–144 62
175–177 59
162–164 62
182–184 65
7
8
66.10 (66.15) 6.34 (6.37) 11.01 (11.05) 3,399 765
57.28 (57.35) 6.61 (6.65) 12.50 (12.56) 3,382 757
9
16H22N3OPS
17H23N2OPSe
21H23N2OPSe
21H24N3PSe
16H22N3OPSe
10
11
12
13
53.55 (53.60) 6.06 (6.10)
58.70 (58.80) 5.40 (5.45)
58.84 (58.90) 5.64 (5.68)
7.33 (7.38)
6.52 (6.56)
9.80 (9.85)
3,404 628
3,359 621
3,312 617
50.23 (50.30) 5.80 (5.84) 10.96 (11.02) 3,406 635
123

Med Chem Res (2011) 20:962–967
965
stretching vibrations were observed in the region 710–758
1
the region 135.5–135.8 ppm. C-8 & C-10 which are
directly linked to phosphorus experienced coupling with it
and appeared as doublet in the region d 54.21–55.26
(J = 126–132 Hz). All the carbons of achiral alcohols and
amines resonated in the expected region (Quin and
Verkade, 1994). The 31P NMR chemical shifts of the title
compounds (4–13) appeared in the range of 41.06–
87.16 ppm as expected (Quin and Verkade, 1994), further
mass spectral data of the compounds 6 and 10 were rep-
resented as typical examples (Table 4, Scheme 2).
and 3,275–3,406 cm-1, respectively (Thomas, 1974). H
NMR chemical shifts for, aromatic protons of the naphthyl
ring of the 6–13 complex multiplets in the region
6.12–7.76 ppm (Silverstein and Webster, 1998). The N–H
proton resonated as a broad singlet at d 4.85–5.30. The
other aliphatic protons of 6–13 were observed in the
expected region (Table 2). 13C NMR chemical shifts for
aromatic carbons were observed in the expected region
(Table 3). C-1 & C-6 were observed in the range of
109.4–110.1 ppm. Chemical shifts for C-2 & C-5 and C-3
& C-4 were observed in the regions 124.6–124.9 and
119.6–119.9 ppm, respectively. C-3a & C-7a carbons res-
onated in the region 136.2–136.7 and 113.19–113.10 ppm,
respectively. C-6a & C-11a which are present in similar
chemical and magnetically same environment resonated in
Biological activity
The Whatman No.1 filter paper disc method (Umamahes-
wari Devi et al., 2000; Colle et al., 1989) was employed for
Table 2 1H NMR spectral data of the compounds 4–13
Compounds
Ar–H
NH
P–CH2–R
4
5
6
6.48–7.35 (m, 6H)
6.12–7.49 (m, 6H)
6.24–7.53 (m, 6H)
4.93 (br s)
5.02 (br s)
4.95 (br s)
3.7 (m, 4H, CH2–P(S)), 3.3 (s, 2H, CH2 Br)
3.9 (m, 4H, CH2–P(Se)), 3.28 (s, 2H, CH2 Br)
3.4 (m, 4H, CH2–P(S)), 3.8 (s, 2H, CH2–O), 3.1 (m, 1H, OCH), 1.42 (m, 2H, CH (CH3)
CH2CH3), 1.22 (m, 3H, CH(CH3) CH2 CH3), 0.91 (m, 3H, CH(CH3) CH2CH3)
7
8
6.32–7.76 (m, 11H)
6.42–7.35 (m, 11H)
5.13 (s)
5.25 (s)
3.48 (m, 4H, CH2P(S)), 3.98 (m, 1H, OCH (CH3) Ph), 1.27 (s, 3H, OCH (CH3) Ph)
3.38 (m, 4H, CH2P(S)), 3.31 (m, 2H, –CH2–NH–), 4.2 br s, 1H NH–CH (CH3) Ph), 2.59
(m, 1H NH–CH (CH3) Ph), 1.19 (s, 3H, NH–CH(CH3) Ph)
9
6.49–7.49 (m, 6H)
5.17 (s)
5.21 (s, 1H, CH2OH), 3.35 (m, 4H, CH2P(S)), 4.16 br, s, 1H, NH–CH (CH2OH),
CH2CH3), 2.70 (m, 1H, NH–CH(CH2OH), CH2 CH3), 3.59 (m, 2H, CH (CH2OH)
CH2CH3), 1.21 (m, 2H, CH (CH2OH), CH2CH3), 0.92 (m, 3H, CH(CH2OH) CH2CH3
10
11
12
13
6.26–7.59 (m, 6H)
6.45–7.73 (m, 11H)
6.43–7.65 (m, 11H)
5.05 (br s)
4.98 (br s)
5.30 (br s)
4.85 (br s)
3.3 (m, 4H, CH2P(Se)), 3.6 (s, 2H–CH2–O), 3.1 (m, 1H, O–CH), 1.45 (m, 2H,CH (CH3)
CH2 CH3), 1.21 (m, 3H, –CH(CH3) CH2CH3), 0.92 (m, 3H, CH (CH3) CH2 CH3)
3.49 (m, 4H, CH2P(Se)), 3.5 (s, 2H, CH2–O), 3.96 (m, 1H, O–CH(CH3) Ph), 1.28 (s,
3H, O–CH– (CH3) Ph)
3.39 (m, 4H, CH2 P(Se)), 3.31 (m, 2H–CH2–NH–), 4.3 (br, s, 1H, NH–CH(CH3) Ph)
2.57 (m, 1H, NH–CH (CH3) Ph), 1.19 (s, 3H, NH–CH (CH3) Ph)
6.52–7.64
(m, 6H)
5.22 (s, 1H, CH2OH), 3.34 (m, 4H, CH2P(Se)), 4.16 (br, s, 1H, NH–CH(CH2OH)
CH2CH3), 2.71 (m, 1H, NH–CH(CH2OH) CH2CH3), 3.58 (m, 2H, CH(CH2OH)
CH2CH3), 1.21 (m, 2H, CH(CH2OH) CH2–CH3), 0.94 (m, 3H, CH, CH2OH CH2CH3)
Table 3 13C NMR spectral data of the compounds 6, 9, 10, and 13
Compounds C-1 & C-2 & C-3 & C-3a C-7a C-6a & C-10 & C-8
C-11a
P–CH2– OCH/– CH– –CH– CH– CH–
CH2– CH2–
C-6
C-5
C-4
NH/O
NH–CH CH2– CH3
CH3
CH3
OH
6
109.9 124.6 119.9 136.1 113.1 135.6
110.1 124.7 119.8 136.4 113.1 135.7
110.1 124.6 119.6 136.2 113.1 135.5
110.1 124.9 119.6 136.7 113.1 135.8
55.2
(d, 1JP–C = 132 Hz)
54.2
(d, 1JP–C = 126 Hz)
55.1
(d, 1JP–C = 130 Hz)
69.5
54.5
69.3
54.7
75.9
59.2
75.9
59.8
33.0
33.7
33.5
33.9
19.7
–
9.7
–
9
9.5
9.4
9.8
72.5
–
10
13
21.1
–
54.7 (d,
1JP–C = 128 Hz)
72.9
Chemical shifts in ppm J (Hz) given in parenthesis
123

966
Med Chem Res (2011) 20:962–967
Table 4 Mass spectral data of the compounds 6 and 10
Compounds m/z (% relative abundance)
Table 5 Antibacterial activity of compounds 4–13
Compounds
Zone of inhibition (%)
Escherichia coli
334[M•?, 17], 277 (41), 261 (21), 247 (14), 219 (100),
184 (11), 155 (31), 126 (28), 73 (36)
Staphylococcus aureus
6
100
50
25
100
50
25
10
381[M•?, 19], 324 (31), 308 (33), 294 (29), 266 (100),
184 (13), 155 (19), 126 (30)
4
10
12
14
8
5
6
3
4
9
8
8
6
8
7
7
3
-
13
9
11
8
9
–
8
7
5
8
7
7
8
5
–
5
6
10
9
13
10
11
12
14
12
10
11
12
12
9
the in vitro study of antibacterial and antifungal effects
against Escherichia coli, Staphylococcus aureus, Asper-
gillus niger, and Helminthosporium oryzae. The inhibitory
effects of compounds 4–13 against these organisms are
given in Tables 5 and 6.
7
8
10
11
13
10
19
10
12
10
7
9
9
7
10
10
8
10
10
6
11
12
6
13
Penicillina
5
9
Antibacterial activity
8
8
a
Antibacterial activity of all the title compounds 4–13 was
assayed (Umamaheswari Devi et al., 2000) against the
growth of Staphylococcus aureus (gram ?ve) and Esche-
richia coli (gram -ve) at concentrations (100, 50, and
25 ppm) (Table 5). Highlight is that majority of the com-
pounds exhibited high activity against both the bacteria,
Standard antibacterial compound
and the compounds 6 and 12 were more effective than that
of the standard compound. Penicillin was tested as a
standard reference compound to compare the activity of
these compounds.
Scheme 2 Mass fragmentation
of compound 6
H
N
H
N
S
P
+
CH2
N
+
P
H
S
H
N
P
N
N
S
m/z 261 (21)
H
+
m/z 219 (100)
O
.
H
-
C4H9O
m/z 277 (41)
.
.
-
C7H15O
-
C4H9
+
.
H
.
N
P
N
-
C13H14N2PS
S
+
O
O
H
.
m/z 73 (36)
-
-
C7H16SOP
N2
C5H11SOP
m/z 334 M+ , (17)
-
.
H
N
-
C7H16SOP
+
.
+
N
N
H
m/z 184 (11)
NH
+
m/z 126 (28)
m/z 155 (31)
123

Med Chem Res (2011) 20:962–967
967
Acknowledgments The authors express their thanks to Prof.
C. Devendranath Reddy and Dr. C. Suresh Reddy, Department of
Chemistry, Sri Venkateswara University, Tirupati, India for encour-
agement and helpful discussion and the Directors, I.I.Sc. Bangalore
and CDRI, Lucknow, India, for the analytical and spectral data.
Table 6 Antifungal activity of compounds 4–13
Compounds
Zone of inhibition (%)
Aspergillus niger
Helminthosporium oryzae
100
50
25
100
50
25
4
9
10
14
13
10
9
5
6
3
4
9
8
8
6
8
7
4
6
–
13
9
11
8
9
–
8
7
5
8
7
7
6
5
–
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13
10
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Antifungal activity
The compounds 4–13 (Table 6) were screened for their
antifungal activity against Aspergillus niger and Helmin-
thosporium oryzae species along with standard fungicide
Griseofulvin. Disc diffusion method (Colle et al., 1989)
was followed for screening the compounds at three dif-
ferent concentrations (100, 50, and 25 ppm).
It is gratifying to observe that all the compounds 4–13
were exhibited higher antifungal activity when compared
with that of reference compound. The highlight is that all
the compounds exhibited very high activity against fungi
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Conclusion
In summary, we have successfully synthesized new class of
phosphorus-based heterocyclic compounds by employing
simple three step synthetic protocol. Many of these novel
analogs showed comparable to better inhibitory activity
than the standard drugs.
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