Microwave-assisted synthesis and diabetic/antioxidant assessments of 1,3,2-benzothiazaphosphole-3(2H)-carbothioamide- and -diazaphosphole-3(2H)-dicarbothioamide 2-oxide derivatives

Article abstract of DOI:10.1007/s00706-016-1721-y

Abstract: Environmentally friendly synthesis of 1,3,2-benzothiazaphosphole-3(2H)-carbothioamide and -diazaphosphole-3(2H)-dicarbothioamide 2-oxides or the carboxamide 2-oxide analogs was reported. The targets were accomplished via a two step process: (1) preparation of the substrates 2-phenyl-2,3-dihydro-1H-1,3,2-benzothiazaphosphole 2-oxide and -1,3,2-benzodiazaphosphole 2-oxide; (2) exploiting these two phospholes in reactions with various saturated and unsaturated isothiocyanates and some isocyanate analogs in dry DMF/pyridine under microwave irradiation thereby isolating the target compounds in 85–95?% yields. Based upon computer-assisted molecular model (CAMM), new compounds were screened for their antidiabetic and antioxidant properties and many of them exhibited moderate to high in vivo and in vitro diabetic and/or antioxidant potencies. Graphical abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s00706-016-1721-y

Monatsh Chem
DOI 10.1007/s00706-016-1721-y
ORIGINAL PAPER
Microwave-assisted synthesis and diabetic/antioxidant
assessments of 1,3,2-benzothiazaphosphole-3(2H)-carbothioamide-
and -diazaphosphole-3(2H)-dicarbothioamide 2-oxide derivatives
Wafaa M. Abdou1 Mohamed S. Bekheit1 Reham F. Barghash1
•
•
Received: 5 November 2015 / Accepted: 28 February 2016
Ó Springer-Verlag Wien 2016
Abstract Environmentally friendly synthesis of 1,3,2-
benzothiazaphosphole-3(2H)-carbothioamide and -diaza-
phosphole-3(2H)-dicarbothioamide 2-oxides or the
carboxamide 2-oxide analogs was reported. The targets
were accomplished via a two step process: (1) preparation
of the substrates 2-phenyl-2,3-dihydro-1H-1,3,2-benzothi-
azaphosphole 2-oxide and -1,3,2-benzodiazaphosphole
2-oxide; (2) exploiting these two phospholes in reactions
with various saturated and unsaturated isothiocyanates and
some isocyanate analogs in dry DMF/pyridine under
microwave irradiation thereby isolating the target com-
pounds in 85–95 % yields. Based upon computer-assisted
molecular model (CAMM), new compounds were screened
for their antidiabetic and antioxidant properties and many
of them exhibited moderate to high in vivo and in vitro
diabetic and/or antioxidant potencies.
Keywords 1,3,2-Benzothiazaphosphole-3(2H)-
carbothioamide 2-oxides Á Benzodiazaphosphole-3(2H)-
dicarbothioamide 2-oxides Á Computer-assisted molecular
model Á Antidiabetic evaluation Á Antioxidant evaluation
Introduction
Diabetes mellitus is a metabolic disorder characterized by
chronic hyperglycemia with disturbances of carbohydrate,
fat, and protein metabolism. A worldwide survey has
reported that diabetes mellitus affects nearly 10 % of the
population [1]. The disease results from defects in insulin
secretion, insulin action, or both [2]. The epidemic diabetes
is accelerating in the developing world, with an increasing
proportion of affected people in younger age groups.
Recent reports described type-2 diabetes being diagnosed
in children and adolescents [3–5].
Graphical abstract
There are many classes of antidiabetic agents available
and these drugs have different mechanisms of action and
variable efficacy. However, many patients undergoing
diabetic treatment suffer from associated serious side
effects [6], emphasizing that the need for new antidiabetic
agents with improved efficacy and reduced side effects is
still a challenge.
Organophosphorus heterocycles have become notably
recognized for their diverse applications in pharmaceutical
systems [7, 8]. On the other hand, heterocyclic systems
containing phosphorus atom have considerable attention
due to the large variety of interesting pharmacological
properties [8–10]. Organophosphorus compounds (OPCs)
have been known to serve as both hyperglycemic and
hypoglycemic agents in different concentrations. As such
an increase in blood glucose and decrease in glycogen in
various constituents of the brain of rats were observed after
Electronic supplementary material The online version of this
article (doi:10.1007/s00706-016-1721-y) contains supplementary
material, which is available to authorized users.
& Wafaa M. Abdou
wabdou@intouch.com;
wabdou@link.net
1
Chemical Industries Division, National Research Centre,
Elbohouth St., Dokki, Cairo 12622, Egypt
123

W. M. Abdou et al.
treatment with malathion [11]. In another report, glycogen
levels had decreased in the liver of rats when treated with
dichlorofos [12]. Furthermore, diisopropyl phosphorofluo-
ridate has the ability to reduce the glucose level in rats [13].
In the same context, phosphites and phosphonates exhib-
ited potent antioxidant effects, and are acting as both
primary and secondary antioxidants [14, 15].
Scheme 1
SH
S
Cl
Cl
O
THF
r.t.
P
P
Ph
+
Ph
N
H
NH2
1
2
3
7
3'
O
S
13 P
N
DMF / pyridine
MW
1'
+
X
C N Y
3
5
4
6'
In sequel, the work herein was designed to synthesize
new 1,3,2-thiaza/dicarbothioamide 2-oxides or the car-
boxamide 2-oxide analogs and to bioassay their
antidiabetic and antioxidant activities. The optimized
pharmacological evaluation of new OPCs based on the
prospective predicted potency was carried out using the
computer-assisted molecular modeling (CAMM) [16, 17].
This study is a part of our continuous interest in synthesis
of a wide range of heterocycle-phosphor ester systems for
biological screening programs [18–23].
X
C
N
H
Y
-
4a 4e
-
5a 5e
Time
/min
Product 5
X
Yield
/%
Entry
Isothio-/isocyanate 4
Cmp
5a
Y
S
S
C
C
N
N
Me (4a)
Et (4b)
S
S
Me
Et
1
2
4
4
91
93
5b
(4c)
3
4
5
6
6
6
5c
5d
5e
S
S
O
95
90
92
S
S
C
N
a
a
(4d)
(4e)
C
N
O
C
N
Results and discussion
Chemistry
executing the previous reaction in the presence of 1 cm3 of
H2O2, the yield of 3 is enhanced to 72 %. On the other
hand, when the reaction was carried out under oxygen free
condition, only the phosphole (and not the phosphole
oxide) is obtained (see experimental section).
In the last few years, the application of microwave irradi-
ation in synthetic organic chemistry has become more and
more interesting. Microwave-assisted synthesis offers a
versatile and a facile pathway for a large variety of syn-
theses. Thus, a large number of organic reactions were
preferably carried out under microwave irradiation due to
higher yields, short reaction times and friendly conditions
of this process [24].
In the second stage, compound 3 was subjected to
reactions with various isothiocyanates 4a–4d and the iso-
cyanate analog 4e in dimethylformamide (DMF)
containing a catalytic amount of pyridine to obtain the
target compounds 5a–5e in excellent yields ([90 %). The
second step of the methodology was completed under
microwave (MW) irradiation within 4–6 min. Compounds
5a–5e were formed via a direct conjugate addition of the
phosphole 2-oxide 3 with the hard electrophiles, isothio-
and isocyanates 4a–4d/4e [28–30].
Motivated by the aforementioned findings, the synthesis
of substituted 1,3,2-thiazaphosphole 2-oxides 5a–5e was
accomplished through two step process (Scheme 1). The
required 1,3,2-thiazaphosphole 2-oxide 3 was prepared by
a slight modification to the procedures reported in the lit-
erature [25, 26]. While in the first method [25] the
P(V) phosphonyl dichloride was used in a general proce-
dure to prepare about thirty phosphole 2-oxide derivatives,
in the second procedure [26] phosphole analogs, e.g. 1,3-
dihydro-1,3,2-benzodiazaphosphole 2-oxide were obtained
from the reaction of parent diamine and P(III) diphenyl
phenylphosphonite. However, in our experiment we treated
2-aminobenzenethiol (1) with dichlorophenylphosphine (2)
in tetrahydrofuran (THF) at room temperature (r.t.) to
afford 3 in 61 % yield (Scheme 1). Compound 3 is com-
patible with the previously reported data [25] (see Figs. 1,
2). The oxidation of the expected phosphole to its oxide
form in the previous reaction is attributed to the presence of
fortuitous water [26] and the affinity of P(III) to oxygen to
establish the more stable P(V) form [27]. However,
1,3,2-Benzothiazaphosphole-3(2H)-carbothioamide
2-oxides 5a–5d and carboxamide 5e exhibited IR absorption
bands for P=O, C=S (or C=O, 5e), and NH in the regions
1196-1180, 1222-1149 (5e: 1728,) and 3423-3348 cm-1
,
respectively. The NH proton gave
a
singlet at
d = 10.55 ppm while the methyl protons (NMe) resonated
at 3.35 ppm as a singlet in the 1H NMR spectrum of 5a. In its
13C NMR spectrum, the C(S) and P–C(10) appeared as two
doublets at d = 186.4 ppm (2JPC = 11.3 Hz) and
1
130.4 ppm (d, JPC = 122 Hz), while the methyl-carbon
showed a doublet at 30.9 ppm (4JPC = 4.2 Hz, Me–N) ppm.
The remaining carbon resonances were observed in the
expected region. 31P NMR signals of 5a–5e were observed in
the region 51.6–56.8 ppm [31].
123

Microwave-assisted synthesis and diabetic/antioxidant assessments of 1,3,2-…
Fig. 1 Mass spectrum of compound 3
Fig. 2 Infrared chart of compound 3
1
We also conducted the same reaction with 1,3,2-ben-
zodiazaphosphole 2-oxide (7), which was obtained as
previously mentioned to 3, under microwave irradiation to
give 1,3,2-benzodiazaphosphole-1,3(2H)-dicarbothioamide
2-oxides 8a–8d and carboxamide 8e in[85 % yield. In this
case, the reaction between 7 and the isothio-4a–4d/iso-
cyanates 4e was completed when only two moles of 4 were
used in the reaction (Scheme 2).
ions. The H NMR spectrum of 8a showed broad charac-
teristic signal at 12.56 ppm for the two NH protons and two
singlets at 3.24, 3.45 ppm assigned to the two methyl
protons. Its 13C NMR spectrum had among others, a dou-
blet (1JPC = 155 Hz) centered at 130.8 ppm assigned to P–
C(10) moiety and only one doublet (2JPC = 8.7 Hz) at
188.2 ppm due to the two C(S) moieties due to the sym-
metry of the molecule.
The structural elucidation of 8 was straightforward,
since the EI-MS data of 8a–8e showed correct molecular
In a systemic study equivalent amounts of 3 and
allylisothiocyanate (9) were reacted under the same
123

W. M. Abdou et al.
Scheme 2
H
N
NH2
NH2
Cl
Cl
O
THF
r.t.
P
P
Ph
+
Ph
N
H
7
2
6
H
N
Y
Y
C
N
1
N
X
4
7
3'
O
DMF / pyridine
MW
3
+
7
X C N Y
P
1'
5'
-
4a 4e
X
N
H
C
-
8a 8e
Time
/min
Product 8
X
Yield
/%
Entry
Isothio-/isocyanate 4
Cmp
Y
S
S
C
C
N
N
Me (4a)
Et (4b)
8a
8b
S
S
Me
Et
1
2
5
5
88
92
Fig. 3 Structure 12
(4c)
3
4
8c
8d
S
S
S
S
C
N
7
7
7
86
91
91
a
a
(4d)
(4e)
C
N
groups in the 1H and 13C NMR spectral data confirmed the
assigned structure 10, 2-phenyl-N-[(1E)-prop-1-en-1-yl]-
1,3,2-benzothiazaphosphole-3(2H)-carbothioamide 2-ox-
ide, and ruled out the other alternative structure like 11
(Scheme 3).
O
C
N
5
8e
O
In a similar fashion, 2-phenyl-N,N0-bis[(1E)-prop-1-en-
1-yl]-1H-1,3,2-benzodiazaphosphole-1,3(2H)-dicarbothio-
amide 2-oxide (12, 86 % yield) was obtained from the
reaction of 7 with two moles of allylisothiocyanate (9)
using the same reaction conditions Fig. 3.
Scheme 3
It is noteworthy that in a blank experiment, benzothiaza-
3 and benzodiazaphosphole 2-oxide 7 were recovered
practically unchanged when a solution of each in DMF/
pyridine was subjected to MW irradiation for 7 min. Fur-
thermore, in a parallel experiment, the phosphole 2-oxides
3 and 7 were allowed to react with methyl isothiocyanate
4a, as a representative example, in DMF solution con-
taining pyridine under thermal condition for &8 h (TLC).
After the usual working up, products 5a and 8a were
obtained in 56 and 46 % yields.
Structures of all synthesized compounds were confirmed
1
by H, 13C, 31P NMR, and MS data as well as IR spectra.
reaction conditions to give a product for which structure 10
was assigned for the following reasons. The 1H NMR
spectrum of 10 showed the methyl protons as a doublet
(JHH = 8.1 Hz) at 2.04 ppm and the NH proton as a broad
signal at 10.75 ppm. On the other hand, the methylene
Biological activity spectra prediction
Prospective biological activity spectra for the molecular
structures 5a–5e, 8a–8e, 10, 12, and the substrates 3 and
7 were predicted in the early stage of the investigation.
The computer assisted molecular modeling (CAMM)
program (PASS, 2012.1 version, IBMC, Moscow, Russia)
was adopted for designing the structures in silico [16, 17].
The spectrum for a substance is a list of the biological
activity types for which the probability to be revealed
(Pa) and the probability not to be revealed (Pi) are cal-
culated. Pa and Pi values are independent and their
values vary from 0 to 1 (Supplementary Material,
1
protons (2H) present in the H NMR spectrum of 9 as a
doublet (JHH = 8.1 Hz) at 4.27 ppm were absent in the
spectrum of 10. Instead, each of the exocyclic methine
protons (2H) in 10 appeared differently. That of proton
(a) appeared as a doublet of quartet (dq, JHH = 8.1,
4.2 Hz) at 4.18 ppm while the other proton (b) showed a
doublet of doublet (JHH = 12.0 Hz, E-form) at 6.33 ppm.
These data were also confirmed in the 13C NMR spectrum.
The presence of the AB system and the lack of signals due
to the methylene (–CH2) and the methylidene (=CH2)
123

Microwave-assisted synthesis and diabetic/antioxidant assessments of 1,3,2-…
Table 1 Blood glucose levels of diabetic rats treated with synthesized phosphole 2-oxide derivatives 5a–5e, 8a–8e, 10, 12, and glibenclamide
(Z)
Compound 20 lg/cm3
FGBa/initial mg/10 cm3
FGBb/final mg/10 cm3
Inhibition/%
Potency/%
Normal cont.
96.54 5.3
414.64 6.3
326.17 13.9
332.22 9.4
342.33 11.4
356.47 9.3
385.26 4.7
316.58 8.7
312.87 7.4
336.21 3.9
354.66 8.6
396.71 10.6
322.62 5.1
313.51 4.8
380.67 10.8
118.33 4.5
477.36 9.9
150.67 5.9
163.44 5.1
166.97 8.6
176.47 3.9
206.54 6.2
132.1 8.8
–
–
Diabetic cont
–
–
5a
5b
5c
5d
5e
8a
8b
8c
8d
8e
10
12
Z
68.44
65.76
65.02
63.03
56.73
72.32
70.54
66.83
64.25
58.87
67.17
71.45
71.32
95.96
92.20
91.16
88.37
79.54
101.40
98.90
93.70
90.08
82.54
94.18
100.18
100
140.62 6.4
158.34 5.6
170.67 10.6
196.33 1.82
156.69 10.3
136.28 8.1
136.88 3.6
a
After 24 h
b
After 21 days
appendix 1). By default, in PASS, Pa = Pi value is
chosen as a threshold, therefore all compounds with
Pa [ Pi are suggested to be active.
The study indicated that the main expected biological
activity of the designed compounds were the antidiabetic
and antioxidant activities, which they had in common.
Antidiabetic activity
Type-2 diabetes mellitus (non-insulin dependent diabetes
mellitus, NIDDM) is a much more prevalent form of reg-
ular diabetes and is responsible for 90 % of the disease
prevalence [32–34]. Therefore, experimental animal model
representing type-2 diabetes, streptozotocin (STZ) diabetic
rats, is used to assess the antidiabetic efficacy of the tested
compounds. This animal model develops most of the bio-
chemical and pathological symptoms associated with type-
2 diabetes in humans [35].
Fig. 4 % Potency of the tested phospholes vs. FBG of diabetic rats
displayed in Fig. 4. Glibenclamide drug (Z) was used as a
reference standard.
A significant diminution of FBG level was observed in
respect to the diabetic rats, but there was no significant
alteration of FBG level to the control. FBG level of all
animals before treatment was within the normal range
whereas FBG level was significantly elevated after 24 h
of STZ injection with respect to the control level.
Data in Table 1 shows that 8a, 8b, 12 exhibited greater
extent of hypoglycemic activity when compared with the
remaining compounds or the reference drug. However,
most of the tested compounds displayed moderated effi-
Accordingly, the antidiabetogenic effect of synthesized
thiazaphospholes 5a–5e, 10, and diazaphospholes 8a–8e
and 12 has been investigated at a dose of 20 mg/kg. The
tested compounds were evaluated in DMSO solution on
STZ-induced diabetic rats in time duration dependent
fashion. After 7 and 21 days of administration with DMSO
solution of the tested compounds, the fasting blood glucose
(FBG) level was collected from the animal of all groups,
and was measured by single touch glucometer [36]. The
results presented in Table 1, while the percentage potency
of the tested phospholes vs. FBG of diabetic rats was
cacy:
5a [ 10 [ 8c [ 5b [ 5c [ 8d [ 5d [ 8e [ 5e.
The highest activity of 8a might be due to the presence of
two of N–C(S)–N moieties along with a small alkyl group
such as methyl fragment substituent at the thiocyanate
motif. On the other hand, the presence of the phenyl
123

W. M. Abdou et al.
% Inhibition
Table 2 Antioxidant activity assay (ABTS) of all new phosphole 2-oxides 5a–5e, 8a–8e, 10, and 12
Comp
Absorb.
% Inhibition
Comp
Absorb.
Control/ABTS
0.57
0.0
8a
8b
8c
8d
8e
10
12
0.12
78.95
84.56
84.03
36.84
50.87
89.65
89.12
Ascorbic acid
0.068
0.14
88.07
75.44
85.26
82.28
21.05
36.84
0.088
0.091
0.36
5a
5b
5c
5d
5e
0.084
0.101
0.45
0.28
0.059
0.062
0.36
fragment as
dramatically.
a
substituent reduced the potency
Table 3 Assay results for bleomycin/DNA damage
Comp
Absorb.
Comp
Absorb.
Toxicity of the promised product
Ascorbic acid
0.021
0.031
0.022
8c
10
12
0.026
5b
8b
0.0914
0.0188
For determination of lethal dose (LD50) of 8a, single
gradual increasing doses were administered to various
groups of normal albino mice. The number of dead animals
in each group was determined after 48 h of compound
administration and LD50 was calculated. LD50 of 8a was
found to be 1578 mg/kg b.w. for mice. Using the conver-
sion equation [37], LD50 for rats was found to be 1096 mg/
kg b.w. Based on this toxicity study, the orally therapeutic
dose for subsequent in vivo study was chosen to be 20 mg/
kg b.w. (*1/50 of LD50), which is very far below LD50.
Antioxidant evaluation
The studied compounds were screened for their antioxidant
activity using ABTS method which was reported by Lissi
et al. [38]. The assay employed here is one of several
assays that depends on measuring the consumption of
stable free radicals, i.e., evaluates the free radical scav-
enging activity of the investigated compounds 5a–5e, 8a–
8e, 10, and 12. The methodology assumes that the con-
sumption of the stable free radicals (X-) will be
determined by reactions as follows:
Fig. 5 The flow of the antioxidant activity of new compounds 5a–5e,
8a–8e, 10, and 12
acid as shown in Table 2. Compounds 5b, 8b, 8c, 10, and
12 displayed high antioxidant effects, while compounds 5a,
5c, and 8a showed moderate antioxidant activity. On the
other hand, compounds 5d, 5e, 8d, and 8e showed only a
weak potency. Compounds 10 and 12 exhibited the highest
potency compared with other compounds.
XH þ YÀ ! YH þ XÀ
Bleomycin-dependent DNA damage assay
The rate and/or the extent of the process measured in terms
of the decrease in X- concentration would be related to the
ability of the added compounds to trap free radicals. The
decrease in color intensity of the free radical solution due
to the scavenging of the free radicals by the antioxidant
material is measured calorimetrically at a specific wave-
length. The assay employed the radical cation derived from
The bleomycin is a family of glycopeptide antibiotics that
is used routinely as antitumor agent. The bleomycin assay
was adopted for assessing the pro-oxidant effects of food
antioxidant. The antitumor/antibiotic bleomycin binds iron
ions and DNA. The bleomycin-iron complex degrades
DNA that, on heating with thiobarbituric acid (TBA),
yields a pink chromogen. Upon the addition of a suit-
able reducing agent, the antioxidant competes with DNA
and diminishes the chromogen formation [39].
2,20-azinobis(3-ethylbenzothiazoline-6-sulfonic
acid,
ABTS) as stable free radical to assess antioxidant potential
of the investigated compounds.
The protective activity against DNA damage induced by
bleomycin-iron complex was examined to show the
Some of the corresponding phosphole 2-oxide deriva-
tives displayed antioxidant activity compared to ascorbic
123

Microwave-assisted synthesis and diabetic/antioxidant assessments of 1,3,2-…
mechanism of action of the potent compounds 5b, 8b, 8c,
10, and 12. Data in Table 3 shows that compounds 10 and
12 exhibited highest protection against DNA damage
induced by the bleomycin-ion complex, which indicated
diminishing chromogen formation between damaged DNA
and phosphorus molecules.
spectra were recorded with tetramethylsilane as internal
standard in DMSO-d6. Chemical shifts (d) are given in
ppm. The mass spectra were performed at 70 eV on an MS-
50 Kratos (A.E.I.) spectrometer provided with a data sys-
tem [spectrometer (Kratos, UK)]. Elemental analyses were
carried out at the Microanalysis Laboratory, Cairo
University, Cairo, Egypt, using elementary Analysen-sys-
teme GmbH-vario EL III Element Analyzer, Germany. The
appropriate precautions in handling moisture-sensitive
compounds were observed. The purity of all new samples
was verified by microchemical analysis (C/H/N/S) and
spectroscopy. Solvents were dried by standard techniques,
TLC: Merck 0.2 mm silica gel 60 F254 analytic aluminum
plates. The microwave oven used is a Milestone Italy
(model: StartSynth, Reactor: Pack2B Basic Single Vessel
Kit).
By comparing the results obtained for the antioxidant
properties of the compounds reported in this study with
their structures, the flow of the structure activity relation-
ships (SARs) was displayed in Fig. 5. Finally, the
phosphole 2-oxides 10 and 12 are more potent than
ascorbic acid, which may be attributable to the presence of
exocyclic unsaturated moiety other than the phosphole
motif.
Conclusion
Preparation of phosphole 2-oxides 3 and 7
A mixture of 3.75 g 2-aminobenzenethiol (1, 30 mmol)
and 3.9 g dichlorophenylphosphine (0.01 mmol) in 30 cm3
THF (98 %) was stirred at r.t. for 30 min. After removal of
the solvent, the residue was collected and crystallized from
EtOH to afford 2-phenyl-3H-l,3,2-benzothiazaphosphole
2-oxide (3) as white substance (4.6 g, 61 %). M.p.: 190 °C
(Ref. [40] 190 °C).
Similarly, the reaction between 3.24 g benzene-1,2-
diamine (6, 30 mmol) and 3.9 g dichlorophenyl phosphine
(2, 30 mmol) in 30 cm3 THF, under the conditions
described above, afforded 1,3-dihydro-2-phenyl-1,3,2-ben-
zodiazaphosphole 2-oxide (7) as orange substance (4.1 g,
60 %). M.p.: 275 °C (Ref. [26] 275 °C).
When the above reactions (preparation of 3 or 7) were
carried out in THF solution containing 1 cm3 H2O2 using
the same amounts at r.t. for &10–15 min (TLC), the
substrates 3 and 7 were obtained after the usual working
up., as sole reaction products. Yields: 3 (72 %), 7 (75 %).
On the other hand, when the reaction of quantitative
amounts of 1 and 2 in THF solution was carried out under
oxygen free condition, only the corresponding 1,3,2-
benzothiazaphosphole (and not the phosphole oxide) is
obtained: m.p.: 148 °C (Ref. [26] 148 °C).
In conclusion, the present investigation afforded an effi-
cient, and environmentally benign methodology toward the
synthesis of 1,3,2-benzothiazaphosphole-3(2H)-carbothio-
amide-, -diazaphosphole-3(2H)-dicarbothioamide 2-oxides
and some of their carboxamide analogs. The process
involved the reactions of 1,3,2-benzothiaza- and 1,3,2-
benzodiazaphosphole 2-oxides with a variety of saturated
and unsaturated isothio and isocyanates under microwave-
assisted condition. The notable advantages of this proce-
dure are: (1) general applicability of nucleophiles with hard
electrophilic isothiocyanates, (2) almost quantitative yields
of the products (85–95 %), (3) very short reaction time, (4)
operational simplicity, (5) less solvent-consuming and
catalyst-free conditions, (6) the present methodology
showed that the phosphole ring is tenable under the used
reaction conditions. Furthermore, type-2 diabetes mellitus
(non-insulin dependent diabetes mellitus, NIDDM) and
antioxidant evaluation of the products showed that the
diazaphosphole-3(2H)-carbothioamide 2-oxides displayed
higher potency compared with the thiazaphosphole-coun-
terparts. This observation indicates that increasing nitrogen
atoms in the phosphole ring enhanced the pharmacological
activity.
Preparation of carbothioamide 2-oxides 5a–5d, 10 and
carboxamide 5e
Experimental
2-Phenyl-2,3-dihydro-1,3,2-benzothiazaphosphole 2-oxide
(3, 0.4 g, 1.6 mmol) in 5 cm3 dry DMF was placed, with a
magnetic stirring bar, into a microwave quartz vessel.
Isothiocyanates: methyl, ethyl, cyclohexane, phenyl isoth-
Melting points were determined with open capillary tube
on an Electrothermal (variable heater) melting point
apparatus and were corrected. IR spectra were recorded on
a JASCO FT-IR 6100 using KBr disk (JASCO, Japan).
NMR spectra were measured with a JEOL E.C.A-500 MHz
(13C: 125.7 MHz, H: 500 MHz, 31P: 202.4 MHz) spec-
trometer (JEOL, Japan). 31P NMR spectra were recorded
with H3PO4 (85 %) as external reference. 1H and 13C NMR
iocyanate
(4a–4d),
allylisothiocyanate
(9),
or
phenylisocyanate (4e) (1.6 mmol) was added, followed
by addition of few drops of pyridine. The reaction mixture
was heated in the microwave reactor at 140 °C for the
suitable hold time (4–6 min). After the completion of the
reaction (TLC), the product mixture was allowed to cool
1
123

W. M. Abdou et al.
2
down, poured into ice-water, and acidified with conc. HCl.
The resulting residue was crystallized from suitable solvent
to afford the corresponding products 5a–5d, 10, and 5e.
C(30,50)), 127.9 (d, JPC = 12.4 Hz, C(20,60)), 125.5 (d,
4JPC = 4.0 Hz, C(5)), 123.7 (d, JPC = 3.8 Hz, C(6)),
4
3
4
117.7 (d, JPC = 8.8 Hz, C(4)), 54.2 (d, JPC = 2.8 Hz,
CH-chex), 39.7, 25.4, 24.2 (3 s, CH2-chex) ppm; 31P NMR
(202.4 MHz, DMSO-d6): d = 56.2 ppm; IR (KBr):
N-Methyl-2-phenyl-1,3,2-benzothiazaphosphole-3(2H)-
carbothioamide 2-oxide (5a, C14H13N2OPS2)
Recrystallization from EtOH afforded a white substance.
m = 3348 (NH), 1194 (P=O), 1149 (C=S) cm-1; MS (EI,
ꢀ
70 eV): m/z (%) = 388 (M?, 60), 246 (100).
1
Yield 0.47 g (91 %); m.p.: 177 °C; H NMR (500 MHz,
DMSO-d6): d = 3.35 (s, 3H, Me–N), 6.96–7.63 (m, 9H,
N,2-Diphenyl-1,3,2-benzothiazaphosphole-3(2H)-carbo-
thioamide 2-oxide (5d, C19H15N2OPS2)
Recrystallization from MeCN afforded a straw yellow
H-Ph, H-Ar), 10.55 (br, 1H, HN) ppm; 13C NMR
2
(125.7 MHz, DMSO-d6): d = 186.4 (d, JPC = 11.3 Hz,
C=S), 140.3 (d, JPC = 14.5 Hz, C(9)), 131.7 (d,
2
1
substance. Yield 0.55 g (90 %); m.p.: 165 °C; H NMR
4
2JPC = 12.8 Hz, C(8)), 131.6 (d, JPC = 4.1 Hz, C(40)),
(500 MHz, DMSO-d6): d = 7.11–7.77 (m, 14H, H-Ph,
130.4 (d, 1JPC = 122 Hz, P–C(10)), 129.8 (d,
3JPC = 10.4 Hz, C(7)), 129.5 (d, 3JPC = 10.3 Hz,
H-Ar), 10.50 (br, 1H, HN) ppm; 13C NMR (125.7 MHz,
2
DMSO-d6): d = 184.8 (d, JPC = 11.4 Hz, C = S), 143.2
(d, JPC = 14.4 Hz, C(9)), 132.2 (d, JPC = 14.8 Hz,
2
2
2
C(30,50)), 129.4, 128.6 (2d, JPC = 12.4 Hz, C(20,60)),
4
125.7 (d, JPC = 3.8 Hz C(5)), 123.8 (d, JPC = 3.8 Hz,
4
4
C(8)), 131.2 (d, JPC = 4.9 Hz, C(40)), 130.4 (d,
3
C(6)), 117.7 (d, JPC = 8.8 Hz, C(4)), 30.9 (d,
3
1JPC = 148 Hz, P–C(10)), 130.0 (d, JPC = 10.4 Hz,
4JPC = 4.2 Hz, Me–N) ppm; 31P NMR (202.4 MHz,
C(7)), 128.3 (d, JPC = 8.5 Hz, C(30,50)), 129.4, 128.6 (d,
3
4
DMSO-d6): d = 52.4 ppm; IR (KBr): m = 3423 (NH),
2JPC = 12.2 Hz, C(20,60)), 125.5 (d, JPC = 4.0 Hz, C(5)),
ꢀ
1195 (P=O), 1154 (C=S) cm-1; MS (EI, 70 eV): m/z
(%) = 320 (M?, 62), 246 (100).
4
123.8 (d, JPC = 3.8 Hz, C(6)), 117.3 (d, JPC = 8.8 Hz,
3
4
C(4)), [138.4 (d, JPC = 3.8 Hz, C(1a)), 127.1, 125.5,
122.0 (C(2a–6a)] ppm; 31P NMR (202.4 MHz, DMSO-d6):
N-Ethyl-2-phenyl-1,3,2-benzothiazaphosphole-3(2H)-
carbothioamide 2-oxide (5b, C15H15N2OPS2)
Recrystallization from MeCN afforded a white substance.
ꢀ
d = 56.8 ppm; IR (KBr): m = 3423 (NH), 1190 (P=O),
1192 (C=S) cm-1; MS (EI, 70 eV): m/z (%) = 382 (M?,
48), 246 (100).
1
Yield 0.5 g (93 %); m.p.: 163 °C; H NMR (500 MHz,
DMSO-d6): d = 1.52 (t, 3H, JHH = 6.6 Hz, MeC–N), 3.60
(q, 2H, JHH = 6.6 Hz, H2C–N), 7.33–7.64 (m, 9H, H-Ph,
H-Ar), 9.89 (br, 1H, HN) ppm; 13C NMR (125.7 MHz,
DMSO-d6): d = 185.8 (d, 2JPC = 12.1 Hz, C=S), 140.2 (d,
N,2-Diphenyl-1,3,2-benzothiazaphosphole-3(2H)-carbox-
amide 2-oxide (5e, C19H15N2 O2PS)
Recrystallization from cyclohexane afforded a pale yellow
1
0.54 g (92 %); m.p.: 75 °C; H NMR (500 MHz, DMSO-
2
2JPC = 12.5 Hz, C(9)), 131.7 (d, JPC = 14.8 Hz, C(8)),
d6): d = 7.29–7.48 (m, 14H, H-Ph, H-Ar), 10.24 (br, 1H,
4
1
131.4 (d, JPC = 4.4 Hz, C(40)), 130.4 (d, JPC = 143 Hz,
HN) ppm; 13C NMR (125.7 MHz, DMSO-d6): d = 145.2
(d, JP–C = 8.8 Hz, C=O), 138.3 (d, JPC = 13.4 Hz,
3
2
2
P–C(10)), 129.8 (d, JPC = 10.4 Hz, C(7)), 129.8 (d,
3JPC = 8.4 Hz,
C(30,50)),
2JPC = 12.4 Hz, C(20,60)), 125.7 (d, JPC = 3.8 Hz C(5)),
129.4,
4
128.3
(d,
C(9)), 135.2 (d, JPC = 14.8 Hz, C(8)), 133.5 (d,
4
2
1JPC = 128 Hz, P-C(10)), 131.2 (d, JPC = 4.6 Hz, C(40)),
4
123.7 (d, JPC = 3.8 Hz, C(6)), 117.7 (d, JPC = 8.8 Hz,
3
3
130.0 (d, JPC = 10.4 Hz, C(7)), 129.8 (d, JPC = 8.4 Hz,
3
4
C(4)), 39.7 (d, JPC = 4.3 Hz, CH2–N), 17.3 (s, Me) ppm;
2
C(30,50)), 128.9 (d, JPC = 12.5 Hz, C(20,60)), 125.5 (d,
31P NMR (202.4 MHz, DMSO-d6): d = 51.6 ppm; IR
4JPC = 4.0 Hz, C(5)), 123.2 (d, JPC = 3.8 Hz, C(6)),
4
-1
3
4
ꢀ
(KBr): m = 3426 (NH), 1187 (P=O), 1212 (C=S) cm
;
117.3 (d, JPC = 8.8 Hz, C(4)), [138.1 (d, JPC = 3.4 Hz,
C(1a)), 127.3, 124.7, 121.4 (C(2a-6a)] ppm; 31P NMR
(202.4 MHz, DMSO-d6): d = 54.4 ppm; IR (KBr):
MS (EI, 70 eV): m/z (%) = 334 (M?, 58), 246 (100).
N-Cyclohexyl-2-phenyl-1,3,2-benzothiazaphosphole-
m = 3407 (NH), 1728 (C=O), 1186 (P=O) cm-1; MS (EI,
ꢀ
3(2H)-carbothioamide 2-oxide (5c, C19H21N2OPS2)
70 eV): m/z (%) = 366 (M?, 65), 246 (100).
Recrystallization from pentane afforded a straw yellow
substance. Yield 0.59 g (95 %); m.p.: 63 °C; 1H NMR
(500 MHz, DMSO-d6): d = 0.99–1.96 (m, 10H, H2C-c-
hex), 3.38 (m, 1H, H-chex), 7.24–7.85 (m, 9H, H-Ph,
H-Ar), 10.70 (br, 1H, HN) ppm; 13C NMR (125.7 MHz,
DMSO-d6): d = 188.6 (d, 2JPC = 12.8 Hz, C=S), 139.6 (d,
2-Phenyl-N-[(1E)-prop-1-en-1-yl]-1,3,2-benzothiazaphos-
phole-3(2H)-carbothioamide 2-oxide
(10, C16H15N2OPS2)
Recrystallization from CHCl3 afforded a pale yellow
1
substance. Yield 0.52 g (88 %); m.p.: 195 °C; H NMR
2
2JPC = 12.6 Hz, C(9)), 131.3 (d, JPC = 14.8 Hz, C(8)),
(500 MHz, DMSO-d6): d = 2.04 (d, 3H, JHH = 8.1 Hz,
Me), 4.18 (dq, 1H, JHH = 8.1, 4.2 Hz, Ha), 6.33 (dd, 1H,
JHH = 12.0 Hz, Hb), 7.06–7.63 (m, 9H, H-Ph, H-Ar),
10.75 (br, 1H, HN) ppm; 13C NMR (125.7 MHz, DMSO-
4
4
130.5 (d, JPC = 4.6 Hz, C(40)), 129.3 (d, JPC = 3.8 Hz,
1
C(6)), 129.7 (d, JPC = 148 Hz, P–C(10)), 129.4 (d,
3JPC = 10.4 Hz, C(7)), 128.3 (d, 3JPC = 8.3 Hz,
123

Microwave-assisted synthesis and diabetic/antioxidant assessments of 1,3,2-…
2
1
d6): d = 179.4 (d, JPC = 11.6 Hz, C=S), 140.6 (d,
4JPC = 4.8 Hz, C(40)), 130.4 (d, JPC = 143 Hz, P–C(10)),
2JPC = 12.2 Hz, C(9)), 137.4 (d, JPC = 3.8 Hz, N–C=C, 129.5 (2d, 3JPC = 8.5 Hz, C(30,50)), 124.7 (d,
4
2
exocyclic), 133.6 (d, JPC = 12.8 Hz, C(8)), 131.7 (d,
3
4JPC = 3.8 Hz C(5,6)), 118.4 (d, JPC = 8.8 Hz, C(4,7)),
4JPC = 4.6 Hz, C(40)), 129.4 (d, JPC = 10.4 Hz, C(7)), 38.7 (d, 4JPC = 4.4 Hz, 2 CH2–N), 18.3 (s, 2 Me) ppm; 31
P
3
128.3 (d, 3JPC = 8.3 Hz, C(30,50)), 127.9 (d, NMR (202.4 MHz, DMSO-d6): d = 53.7 ppm; IR (KBr):
1JPC = 148 Hz,
P–C(10)),
129.4,
126.8
(d,
m = 3436–3389 (2 NH), 1196 (P=O), 1208, 1228 (2 C=S)
cm-1; MS (EI, 70 eV): m/z (%) = 404 (M?, 39), 228
(100).
ꢀ
2JPC = 12.6 Hz, C(20,60)), 125.5 (d, JPC = 4.0 Hz,
4
4
C(5)), 123.5 (d, JPC = 3.8 Hz, C(6)), 120.4 (d,
3JPC = 10.8 Hz, C(4)), 110.7 (s, CHMe), 14.5 (s, Me)
N,N0-Dicyclohexyl-2-phenyl-1H-1,3,2-benzodiazaphosp-
hole-1,3(2H)-dicarbothioamide 2-oxide
(8c, C26H33N4OPS2)
ppm; 31P NMR (202.4 MHz, DMSO-d6): d = 51.2 ppm;
-1
;
ꢀ
IR (KBr): m = 3367 (NH), 1220 (C=S), 1180 (P=O) cm
MS (EI, 70 eV): m/z (%) = 346 (M?, 62), 246 (100).
Recrystallization from MeOH afforded a pale yellow
1
Preparation of carbothioamide 2-oxides 8a–8d, 12 and substance. Yield 0.76 g (86 %); m.p.: 166 °C; H NMR
carboxamide 8e
Benzodiazaphosphole 2-oxide 7 (0.4 g, 1.75 mmol) and
two molar equivalent (3.5 mmol) of the isothiocyanates
(500 MHz, DMSO-d6): d = 1.09–1.66 (m, 2 9 10H, H2-
C-chex), 3.78–3.81 (m, 2 9 1H, H-chex), 7.25–7.77 (m,
9H, H-Ph, H-Ar), 12.52 (br, 2 9 1H, 2 HN) ppm; 13C
4a–4d, 9 or isocyanate 4e (3.5 mmol) in 7 cm3 dry DMF NMR (125.7 MHz, DMSO-d6): d = 192.2 (d,
2
were caused to react under the MW irradiation (5–7 min)
under the same previous reaction conditions. After the
completion of the reaction (TLC), the product mixture was
allowed to cool down, poured into ice-water, and acidified
with conc. HCl. The resulting residue was crystallized from
2JPC = 10.4 Hz, 2 C = S), 133.6 (d, JPC = 11.8 Hz,
3
C(8,9)), 131.6 (d, JPC = 8.6 Hz, C(20,60)), 130.8 (d,
1
4JPC = 4.6 Hz, C(40)), 130.3 (d, JPC = 163 Hz, P–
3
C(10)), 128.8 (d, JPC = 8.2 Hz, C(30,50)), 124.5 (d,
3
4JPC = 4.0 Hz, C(5,6)), 119.6 (d, JPC = 8.8 Hz, C(4,7)),
suitable solvent to give the corresponding products 8a–8d, 57.4 (d, 4JPC = 2.8 Hz, N–CH–chex), 39.7, 25.4, 24.2 (3 s,
12, and 8e.
CH2–chex) ppm; 31P NMR (202.4 MHz, DMSO-d6):
ꢀ
d = 52.1 ppm; IR (KBr): m = 3413–3945 (2 NH), 1194
N,N0-Dimethyl-2-phenyl-1H-1,3,2-benzodiazaphosphole-
1,3(2H)-dicarbothioamide 2-oxide (8a, C16H17N4OPS2)
Recrystallization from CHCl3 afforded a yellow substance.
(P=O), 1146, 1210 (2 C=S) cm-1; MS (EI, 70 eV):
m/z (%) = 512 (M?, 37), 228 (100).
1
Yield 0.57 g (88 %); m.p.: 289 °C; H NMR (500 MHz,
N,N0-Diphenyl-2-phenyl-1H-1,3,2-benzodiazaphosphole-
DMSO-d6): d = 3.24, 3.45 (2s, 2 9 3H, 2 Me–N),
7.22–7.88 (m, 9H, H-Ph, H-Ar), 12.56 (br, 2 9 1H, 2 Recrystallization from MeOH afforded a yellow substance.
1,3(2H)-dicarbothioamide 2-oxide (8d, C26H21N4OPS2)
1
HN) ppm; 13C NMR (125.7 MHz, DMSO-d6): d = 188.2 Yield 0.79 g (91 %); m.p.: 265 °C; H NMR (500 MHz,
2
2
(d, JPC = 11.8 Hz, 2 C = S), 133.3 (d, JPC = 14.5 Hz, DMSO-d6): d = 7.26–7.90 (m, 19H, m, H-Ph, H-Ar),
2
C(8,9)), 131.8 (d, JPC = 12.4 Hz, C(20,60)), 131.5 (d,
12.02 (br, 2 9 1H, 2 HN) ppm; 13C NMR (125.7 MHz,
4JPC = 4.9 Hz, C(40)), 130.8 (d, JPC = 155 Hz, P–C(10)), DMSO-d6): d = 188.8 (d, JPC = 11.8 Hz, 2 C=S), 133.4
1
2
129.8 (d, 3JPC = 10.4 Hz, C(30,50)), 124.4 (d,
2
(d, JPC = 11.8 Hz, C(8,9)), 131.2 (d, JPC = 12.6 Hz,
2
4JPC = 3.5 Hz C(5,6)), 119.7 (d, JPC = 8.8 Hz, C(4,7)), C(20,60)), 130.7 (d, JPC = 4.6 Hz, C(40)), 130.3 (d,
3
4
32.9 (d, JPC = 4.2 Hz, 2 Me–N) ppm; 31P NMR 1JPC = 160.4 Hz, P–C(10)), 129.8 (d, JPC = 8.2 Hz,
4
3
4
(202.4 MHz, DMSO-d6): d = 54.4 ppm; IR (KBr):
C(30,50)), 124.1 (d, JPC = 4.0 Hz, C(5,6)), 119.6 (d,
4
3JPC = 8.8 Hz, C(4,6)), [137.8 (d, JPC = 3.8 Hz, C(1a)),
ꢀ
m = 3374–3350 (2 NH), 1182 (P=O), 1154, 1201 (2 C=S)
cm-1; MS (EI, 70 eV): m/z (%) = 376 (M?, 43), 228 125.6, 124.8, 122.3, 120.6 (C(2a–6a)] ppm; 31P NMR
(100).
(202.4 MHz, DMSO-d6): d = 53.8 ppm; IR (KBr):
ꢀ
m = 3431 (2 NH), 1190 (P=O), 1213, 1175 (2 C=S)
N,N0-Diethyl-2-phenyl-1H-1,3,2-benzodiazaphosphole-
1,3(2H)-dicarbothioamide 2-oxide (8b, C18H21N4OPS2)
Recrystallization from CHCl3 afforded a yellow substance.
cm-1; MS (EI, 70 eV): m/z (%) = 500 (M?, 25), 228
(100).
1
Yield 0.64 g (92 %); m.p.: 234 °C; H NMR (500 MHz,
N,N0-Diphenyl-2-phenyl-1H-1,3,2-benzodiazaphosphole-
DMSO-d6): d = 1.29, 1.41 (2t, 2 9 3H, J = 7.8 Hz, 2 1,3(2H)-dicarboxamide 2-oxide (8e, C26H21N4O3P)
MeC–N), 3.56–3.69 (m, 2 9 2H, 2 H2C-N), 7.21-7.72 (m, Recrystallization from MeOH afforded a yellow substance.
1
9H, H-Ph, H-Ar), 12.21 (br, 2 9 1H, 2 HN) ppm; 13C Yield 0.73 g (91 %); m.p.: 157 °C; H NMR (500 MHz,
NMR (125.7 MHz, DMSO-d6): d = 188.8 (d, DMSO-d6): d = 7.20–7.87 (m, 19H, H-Ph, H-Ar), 11.80
2
2JPC = 10.9 Hz, 2 C=S), 134.2 (d, JPC = 12.5 Hz,
(2br, 2 9 1H, HN) ppm; 13C NMR (125.7 MHz, DMSO-
2
2
C(8,9)), 131.3 (d, JPC = 12.3 Hz, C(20,60)), 131.4 (d,
d6): d = 150.3 (d, JPC = 10.2 Hz, 2 C=O), 134.6 (d,
123

W. M. Abdou et al.
2
1JPC = 154.4 Hz, P–C(10), 131.6 (d, JPC = 14.8 Hz,
After removal of the volatile materials under vacuum, the
residual substance was crystallized from EtOH to give,
practically unchanged 3 or 7 (TLC, m.p., mixed m.ps, and
comparative IR spectra).
4
C(8,9)), 130.5 (d, JPC = 3.9 Hz, C(40)), 127.8 (d,
2
3JPC = 8.1 Hz, C(30,50)), 127.9 (d, JPC = 12.2 Hz,
4
C(20,60)), 125.5 (d, JPC = 4.0 Hz, C(5,6)), 120.6 (d,
3JPC = 8.8 Hz, C(4,7)), [138.4 (d, JPC = 3.8 Hz, 2
4
C(1a)), 128.4, 127.6, 127.1, 125.6, 124.4, 122.0, 118.6
(C(2a–6a)] ppm; 31P NMR (202.4 MHz, DMSO-d6):
Experimental animals
ꢀ
d = 54.1 ppm; IR (KBr): m = 3425, 3400 (2 NH), 1738,
Experimental albino mice (weighing 20–25 g) were
obtained from the Animal House of Ophthalmology Insti-
tute, Giza, Egypt. They were kept under observation for
2 weeks in the department animal house to exclude any
inter-current infection. They were supplied standard diet
and tap water ad libitum, and maintained under suit-
able living conditions in good aerated cages at natural daily
12 h dark-light cycle and at r.t. 20–25 °C. All international
principles and local regulations concerning the care and the
use of laboratory animals were considered during the
pharmacological screening.
1727 (2 C=O), 1194 (P=O) cm-1; MS (EI, 70 eV):
m/z (%) = 468 (M?, 65), 228 (100).
2-Phenyl-N,N0-bis[(1E)-prop-1-en-1-yl]-1H-1,3,2-benzodi-
azaphosphole-1,3(2H)-dicarbothioamide 2-oxide
(12, C20H21N4OPS2)
Recrystallization from MeOH afforded a straw yellow
1
substance. Yield 0.63 g (86 %); m.p.: 212 °C; H NMR
(500 MHz, DMSO-d6): d = 2.01, 2.23 (2d, 2 9 3H,
JHH = 8.4 Hz, 2 MeN), 4.15, 4.26 (2 dq, 2 9 1H,
JHH = 8.4, 4.3 Hz, Ha), 6.21, 6.45 (2dd, 2 9 1H,
JHH = 12.8, Hb), 7.06–7.63 (m, 9H, H-Ph, H-Ar), 10.90
(br, 2 9 1H, 2 HN) ppm; 13C NMR (125.7 MHz, DMSO-
Antidiabetes evaluation
2
d6): d = 192.3 (d, JPC = 12.4 Hz, 2 C=S), 137.4 (d,
Diabetes was induced in rats (15 groups, 6 rats in each
group) by the intraperitoneal (i.p.) injection of streptozocin
(STZ) at a dose of 20 mg/kg (b.w.) dissolved in freshly
prepared phosphate buffer. Seven days after the injection,
the blood glucose levels were measured. Each animal with
a blood glucose concentration level above 250 mg/100 cm3
was considered to be diabetic and used in the experiments.
To prevent the hypoglycemia, which occurred during the
24 h following the STZ administration, 15 % glucose
solution was orally given to the antidiabetic rats. In all
experiments, rats were fasted for 6 h prior to STZ injection.
The tested samples 5a–5e, 8a–8e, 10, 12, and gliben-
clamide (Z) were dissolved DMSO (100 mg/100 cm3) and
administered orally (2 mM) solution using a gastric gauge
needle. Blood glucose levels were determined after the
administration of the tested samples to check the antidia-
betic activity of the compounds. Fasting blood glucose level
was measured after 7th and 21st day from the animals of all
these groups. The blood was collected from the tips of the
tail reins and measured using single touch glucometer.
These data were expressed in terms of milligram per
100 cm3 of blood and the results are displayed in Table 1.
2JPC = 14.8 Hz, 2 N–C=C, exocyclic), 136.4 (d,
1JPC = 158 Hz, P–C(10)), 134.6 (d, JPC = 14.8 Hz,
2
2
C(8,9)), 132.8 (d, JPC = 12.8 Hz, C(20,60)), 131.7 (d,
4JPC = 3.9 Hz, C(40)), 128.3 (d, JPC = 8.1 Hz, C(30,50)),
3
4
124.5 (d, JPC = 4.0 Hz, C(5,6), C(6)), 120.4 (d,
3JPC = 10.8 Hz, C(4,7)), 110.7 (s, 2 CHMe), 14.5 (s, 2
Me) ppm; 31P NMR (202.4 MHz, DMSO-d6):
d = 54.4 ppm; IR (KBr): = 3411, 3383 (2 NH), 1205,
1180 (2 C=S), 1190 (P=O) cm-1; MS (EI, 70 eV):
m/z (%) = 428 (M?, 62), 228 (100).
Parallel thermal experiment
A stirred mixture of equivalent amounts of benzothi-
azaphosphole 2-oxide 3 (or benzodiazaphosphole 2-oxide
7) and methyl isothiocyanates 4a in 10 cm3 DMF, was
followed by adding few drops of pyridine. The reaction
mixture was heated under reflux for 6-8 h (TLC). After
removal of the volatile materials under vacuum, the residual
substance was crystallized from the proper solvent to give
the corresponding products 5a or 8a in 56 and 46 % yields
(TLC, m.p., mixed m.ps, and comparative IR spectra).
AðcontrolÞ À BðtestÞ
% Inhibition =
 10:
Blank experiment
AðcontrolÞ
Toxicity study and determination of LD50
A sample of 0.2 g benzothiazaphosphole 2-oxide (3,
0.8 mmol) or 0.2 g benzodiazaphosphole 2-oxide (7,
0.87 mmol) in 5 cm3 dry DMF was placed, with a mag-
netic stirring bar into the MW-quartz vessel, followed by
addition of few drops of pyridine. The reaction mixture was
heated in the MW reactor at 140 °C for 7 min hold time.
LD50 of the studied compound 8b was determined as
described by Olfert et al. [37]. In this experiment, six
groups each of 8 male albino mice weighing 20–25 g were
used. One group serves as control and other groups of mice
123

Microwave-assisted synthesis and diabetic/antioxidant assessments of 1,3,2-…
were orally administered the tested compound by gastric
tube in gradual increasing doses (400, 500, 600, 800, and
1000 mg/kg b.w.). After 48 h of administration, the num-
ber of dead animals in each group, the mean of dead
animals in two successive doses (z) and the constant factor
between two successive doses (d) were recorded and LD50
was calculated as follow: LD50 = Dm-R (z 9 d)/n, where
Dm = the largest dose which kills all animals, z = mean of
dead animals between two successive records, d = the
constant factor between two successive doses, n = number
of animals in each group, R = the sum of (z 9 d).
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