Synthesis of phosphonic acid containing thiadiazole

Article abstract of DOI:10.1002/hc.20395

A series of phosphonic acid, 1,3,4-thiadiazol-2-amine-N-alkyl have been synthesized by the reaction of 2-amine thiadiazole, different aldehydes (or ketone), and phosphorous acid via the melting method or the solvent method. These compounds have been chara

Full text of DOI:10.1002/hc.20395

Heteroatom Chemistry
Volume 19, Number 2, 2008
Synthesis of Phosphonic Acid Containing
Thiadiazole
Hairong Hu, Chuanfang Zhu, and Juan Fu
Department of Chemistry, Central China Normal University, Wuhan 430079,
People’s Republic of China
Received 22 December 2006; revised 30 May 2007
have been developed and applied in the rare metal
ABSTRACT: A series of phosphonic acid, 1,3,4-
thiadiazol-2-amine-N-alkyl have been synthesized by
the reaction of 2-amine thiadiazole, different aldehy-
des (or ketone), and phosphorous acid via the melt-
ing method or the solvent method. These compounds
extraction [5], corrosion inhibition of metals, etc.
Heterocyclic compounds, especially those con-
taining nitrogen, sulfur, or oxygen can form a com-
plex film on the metal surface due to the pres-
ence of lone-pair of electrons and/or aromatic rings
[6]. These compounds include benzotriazole [7,8],
thioimidazole [9], pyrimidines [10], etc. Thus, they
are often used to protect metals from corrosion
[11,12]. It is known that phosphonic acids contain-
ing heterocycle are effective inhibitors for metals
[13–15].
1
have been characterized by IR, H NMR, 31P NMR,
and elemental analysis. Results showed that com-
pounds were reacted via the solvent method in better
ꢀ
C
yields. 2008 Wiley Periodicals, Inc. Heteroatom Chem
19:140–143, 2008; Published online in Wiley InterScience
(www.interscience.wiley.com). DOI 10.1002/hc.20395
Corrosion inhibition by phosphonic acids and
heterocyclic compounds prompted us to prepare a
new kind of compound with a high-effective inhibi-
tion for metal corrosion. In this paper, a series of
phosphonic acids containing heterocycle were syn-
thesized by different methods.
INTRODUCTION
Corrosion inhibitors are widely used in industry to
reduce the corrosion rate of metals, which is caused
due to the contact with aggressive environments.
Their protective action is based on the formation
of a metal–inhibitor complex film on the metal sur-
face. Many phosphonic acids have been used as wa-
ter treatment reagents [1,2]. As early as 1970, phos-
phonate was successfully used as a reagent in the
water treatment of the brewery by Hass Geffers Co-
logue [3]. In addition, phosphonic acids may act as
inhibitors for metal dissolution due to the chelating
action and the formation of a physical blocking bar-
rier on the metal surface. Many kinds of phosphonic
acid including EDTMP, HDTP, NTP, and HEDP [4],
RESULTS AND DISCUSSION
Phosphonic acids containing heterocycle were syn-
thesized (Scheme 1) by the reaction of 2-amine thia-
diazole, different aldehydes (or ketone), and phos-
phorous acid via different methods.
Phosphorous acid reacted with 2-amine thiadi-
azole and aldehydes (formaldehyde and butyralde-
hyde) in the presence of concentrated hydrochlo-
ric acid by boiling the solution to afford a and b
(Scheme 2) in 21–26% yields. The color of solid a and
b is khaki. The structures of a and b have been char-
acterized spectroscopically, and their data are listed
in Table 2. The gross formula, C3H6N3O3SP, of a was
confirmed by the mass spectrum, which exhibited
Correspondence to: Chuanfang Zhu; e-mail: cfzhuch@126.com.
2008 Wiley Periodicals, Inc.
c
ꢀ
140

Synthesis of Phosphonic Acid Containing Thiadiazole 141
CH at δ = 8.32 ppm, CHP at δ = 4.68 ppm, NH at δ
= 4.47 ppm, OH at δ = 2.45 ppm, Ar H at δ = 7.23,
7.60 ppm. Moreover, the 31P NMR of c showed sig-
nals at 12.42. Its mass spectrum showed a molecular
ion peak, as the base peak at m/z 271.
EXPERIMENTAL
Melting points were determined with a model X4
apparatus and were uncorrected. MS were measured
on a Finnigan Trace MS spectrometer. 1H NMR spec-
tra and 31P NMR spectra were recorded on a Varian
Mercury 400 spectrometer, and resonance is given
in ppm (δ) relative to TMS. IR was measured on a
Perkin-Elmer Spectrum-2000 Fourier infrared spec-
trum apparatus. Elemental analysis was recorded on
a Vario EL III elemental analysis instrument.
SCHEME 1
Preparation of a and b
SCHEME 2
A mixture of 2-amine thiadiazole (0.05 mol) and
phosphorous acid (0.05 mol) in concentrated hy-
drochloric acid (5 mL) was stirred and heated. Alde-
hyde (0.06 mol) was added dropwise at 80◦C. The
mixture was refluxed for 2–4 h. The solution was al-
lowed to cool to room temperature and was neutral-
ized by 20% NaOH to pH 2–3. The precipitate was
removed by filtration. The precipitated solid was re-
crystallized from acetic acid/water to obtain a and b.
the molecular ion at m/z 195. The IR spectrum of
a revealed peaks at 3395 cm−1 (N H), 1218 cm−1
(P O), 2678 cm−1 (P OH), and 1666 cm−1 (C N).
The 1H NMR spectrum exhibited a multiplet at 4.21
4.42 (m, 1H, NH), a doublet at 3.91 (d, 2H, CH2P),
and two kinds of singlet at 7.92 (s, 1H, CH) and
2.49 (s, 2H, OH). The 31P NMR spectrum showed a
singlet peak: δP 8.12.
Compounds c–l (Scheme 3) were obtained in
tetramethylenesulfone solvent at 170◦C–180◦C by
equimolecular addition of reactants. Furthermore,
c–l were also prepared by the reaction of phospho-
rous acid, 2-amine thiadiazole, and aldehydes (or
ketone) without solvent at 190◦C–200◦C.
Preparation of c–l
Method A (Solvent Method). Tetramethylene-
sulfone (20 mL) was added in a three-necked flask
and heated. Phosphorous acid (0.05 mol), 2-amine
thiadiazole (0.05 mol), and toluene-p-sulfonic acid
(0.02 mol) were added at 80◦C. Aldehyde (or ketone)
(0.06 mol) was then added dropwise to the mixture.
When the addition was complete, the reactant was
stirred at 120◦C for 10 min. The mixture was heated
to 170–180◦C and kept for 30 min and then cooled.
Water was added. The solid product was collected by
filtration and recrystallized from acetic acid/water to
yield c–l.
The results are listed in Table 1. The structures
1
of the products were confirmed by IR, H NMR, 31P
NMR, MS, and elemental analysis, and their data are
listed in Table 2. Compound c (taken as a represen-
tative example) gave correct elemental analyses, and
the IR spectrum of c showed the absorption bands of
NH at 3400 cm−1, Ph C at 3044 cm−1, P O at 1243
cm−1, P OH at 2560 cm−1, C N at 1690 cm−1, and
1
C C at 1450 cm−1. Its H NMR revealed signals of
Method B (Melting Method). To a mixture of
2-amine thiadiazole (0.05 mol), phosphorous acid
(0.05 mol), and toluene-p-sulfonic acid (0.02 mol)
was slowly added aldehyde (or ketone) (0.06 mol).
The reaction mixture was heated to 190–200◦C for
30 min and then cooled. The solid was washed by
water. The product so obtained was collected by
filtration and recrystallized from acetic acid/water
to yield c–l.
SCHEME 3
Heteroatom Chemistry DOI 10.1002/hc

142 Hu, Zhu, and Fu
TABLE 1 Preparation of Phosphonic Acid, 1,3,4-Thiadiazol-2-Amine-N-Alkyl a–l
R1
R2
Formula
Yield (%) Solvent (Melting)
MP (◦C)
a∗
b∗
c
d
e
f
g
h
i
H
H
H
H
H
H
H
H
H
H
C3H6N3O3SP
C6H12N3O3SP
C9H10N3O3SP
C9H10N3O4SP
C10H12N3O4SP
C9H10N3O4SP
C9H8N3O3SPCl2
C9H9N3O3SPCl
C9H11N4O3SP
C9H9N3O3SPBr
C9H9N4O5SP
21
26
187–188
169–170
254–256
>300
152–154
288–290
232–234
167–169
296–298
142–144
264–266
216–217
n-C3H7
Ph
72 (50)
79 (52)
82 (55)
67 (42)
65 (32)
66 (37)
81 (56)
70 (40)
73 (44)
60 (37)
p-OHC6H4
p-OCH3C6H4
o-OHC6H4
m, p-ClC6H3
p-ClC6H4
p-NH2C6H4
o-BrC6H4
m-NO2C6H4
Ph
j
k
l
H
H
CH3
C10H12N3O3SP
TABLE 2 The Elemental Analyses, IR, MS, 1H NMR, and 31P NMR Data of Phosphonic Acid, 1,3,4-Thiadiazol-2-Amine-N-Alkyl
a–l
Anal. %, (calc.)
IR(cm−1
)
MS (m/z)
195
1H NMR (δ, ppm)
31P NMR (δ, ppm)
a
b
c
d
e
f
C, 18.35 (18.46); 3395, 1218,
H, 2.96 (3.08); 2678, 1666
N, 21.42 (21.54)
7.92 (s, 1H, CH), 4.21–4.42 (m, 1H, NH),
2.49 (s, 2H, OH), 3.91 (d, 2H, CH2P)
8.12
C, 30.26 (30.40); 3420, 1231,
H, 4.95 (5.06); 2586, 1675
N, 17.59 (17.72)
237
271
287
301
287
340
305
286
349
316
285
7.96 (s, 1H, CH), 4.24 (d, 1H, NH), 2.49 (s,
2H, OH), 3.61–3.83 (m, 1H, CHP)
19.05
12.42
13.46
10.60
23.37
21.15
12.88
16.76
14.38
17.88
13.72
C, 39.71 (39.85); 3400, 3044,
H, 3.55 (2.69); 1243, 2560,
N, 15.38 (15.50) 1690, 1450
C, 37.75 (37.63); 3500, 3040,
H, 3.39 (3.48); 1240, 2591,
N, 14.55 (14.63) 1688, 1438
C, 39.81 (39.87); 3400, 3059,
H, 3.93 (3.99); 1210, 2560,
N, 13.89 (13.95) 1665, 1447
C, 37.80 (37.63); 3411, 3032,
H, 3.40 (3.48); 1250, 2650,
N, 14.58 (14.63) 1655, 1452
C, 31.81 (31.76); 3408, 3032,
H, 2.30 (2.35); 1245, 2680,
N, 12.43 (12.35) 1674, 1460
C, 35.40 (35.35); 3415, 3051,
H, 3.20 (3.27); 1252, 2670,
N, 13.81 (13.75) 1670, 1463
C, 37.74 (37.62); 3380, 3039,
H, 3.9 1 (3.85); 1210, 2596,
N, 19.49 (19.58) 1695, 1435
C, 30.91 (30.86); 3430, 3046,
H, 2.81 (2.86); 1245, 2623,
N, 12.03 (12.00) 1670, 1457
C, 34.22 (34.17); 3415, 3035,
H, 2.81 (2.85); 1218, 2691,
N, 17.68 (17.72) 1680, 1459
C, 41.96 (42.11); 3427, 3080,
H, 4.08 (4.21); 1221, 2742,
8.32 (s, 1H, CH), 4.68 (d, 1H, CHP), 4.47 (d,
1H, NH), 2.45 (s, 2H, OH), 7.23–7.60 (m, 5H,
Ar H)
8.52 (s, 1H, CH), 4.38 (d, 1H, CHP), 2.44 (s,
2H, P OH), 5.20 (s, H, Ar OH), 6.91–7.54
(m, 4H, Ar H)
8.48 (s, 1H, CH), 5.18 (d, 1H, CHP), 2.43 (s,
2H, P OH), 3.60 (s, 3H, OCH3), 7.11–7.46
(m, 4H, Ar H)
8.11 (s, 1H, CH), 4.58 (d, 1H, CHP), 2.44 (s,
2H, P OH), 5.25 (s, H, Ar OH), 7.16–7.46
(m, 4H, Ar H)
8.23 (s, 1H, CH), 5.06 (d, 1H, CHP), 4.45 (d,
1H, NH), 2.45 (s, 2H, P OH), 6.71–7.26 (m,
3H, Ar H)
8.46 (s, 1H, CH), 4.96 (d, 1H, CHP), 4.43 (d,
1H, NH), 2.45 (s, 2H, P OH), 6.95–7.48 (m,
4H, Ar H)
8.15 (s, 1H, CH), 4.79 (d, 1H, CHP), 4.52 (s,
2H, NH2), 2.43 (s, 2H, P OH), 6.88–7.54 (m,
4H, Ar H)
8.65 (s, 1H, CH), 5.21 (d, 1H, CHP), 4.42 (d,
1H, NH), 2.45 (s, 2H, P OH), 7.13–7.68 (m,
4H, Ar H)
g
h
i
j
k
l
8.85 (s, 1H, CH), 4.97 (d, 1H, CHP), 4.48 (d,
1H, NH), 2.50 (s, 2H, P OH), 7.98–8.43 (m,
4H, Ar H)
8.52(s, 1H, CH), 1.87(d, 3H, CH3), 4.47 (d,
1H, NH), 2.45 (s, 2H, P OH), 7.55–7.88 (m,
5H, Ar H)
N, 14.61(14.74)
1657, 1471
Heteroatom Chemistry DOI 10.1002/hc

Synthesis of Phosphonic Acid Containing Thiadiazole 143
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Heteroatom Chemistry DOI 10.1002/hc