A new class of sulfur-linked bis-1,2,3-selenadiazoles, 1,2,3-thiadiazoles, and 2H-diazaphospholes

Article abstract of DOI:10.1002/hc.20425

Novel sulfur-linked bis-heterocycles, bis-1,2,3-selenadiazoles 4, 1,2,3-thiadiazoles 5, and 2H-diazaphospholes 1, were synthesized from bis(2-oxo-2-phenylethanone)sulfide 2 by adopting a simple and well-versed methodology.

Full text of DOI:10.1002/hc.20425

Heteroatom Chemistry
Volume 19, Number 3, 2008
A New Class of Sulfur-Linked
Bis-1,2,3-selenadiazoles, 1,2,3-Thiadiazoles,
and 2H-diazaphospholes
Venkatapuram Padmavathi, Konda Mahesh, Dandu Rangayapalle
Chinna Venkata Subbaiah, and Adivireddy Padmaja
Department of Chemistry, Sri Venkateswara University, Tirupati 517 502, India
Received 8 September 2006; revised 25 July 2007
selenium is part of a functional group, namely,
ABSTRACT: Novel sulfur-linked bis-heterocycles,
SeH and SeO3H, it tends to be more toxic than
their sulfur analogs [2]. But when selenium is part
of a ring system, the toxicity of sulfur and selenium
does not differ widely. This paves the way toward
bis-1,2,3-selenadiazoles 4, 1,2,3-thiadiazoles 5, and
2H-diazaphospholes 7, were synthesized from bis(2-
oxo-2-phenylethanone)sulfide 2 by adopting a simple
ꢀ
C
and well-versed methodology. 2008 Wiley Periodicals,
the development of selenium-containing drugs like
Inc. Heteroatom Chem 19:261–265, 2008; Published online
75Se-selenomethionine used in pancreatic scan-
in Wiley InterScience (www.interscience.wiley.com). DOI
ning [3]. Some arylsulfonyl-1,2,3-selenadiazoles
10.1002/hc.20425
and arylsulfonyl-1,2,5-selenadiazoles exhibit an-
timicrobial activity [4] Besides, sulfur-containing
heterocycles such as thiadiazoles are well known for
INTRODUCTION
their pronounced biological activity [4d,5]. In view
of our successful results toward the development of
a variety of heterocycles of this type [6], herein we
wish to report bis-heterocycles incorporating 1,2,3-
selenadiazole, thiadiazole, and 2H-diazaphosphole
moieties.
The chemistry of compounds having α-
ketomethylene group has evoked considerable
interest because of their utility as building blocks
for the development of heterocyclic ring systems.
A number of heterocyclic compounds containing
nitrogen and sulfur exhibit a variety of biological
activities. The concept of isosteric exchange is a tool
for modifying the activity of biologically important
molecules. One such isosteric pair constitutes
sulfur and selenium. The medicinal applications
of isosterism have been reviewed by Schatz [1].
Substitution of selenium for oxygen and sulfur in
chemotherapeutically active compounds is impeded
by the toxic nature of selenium. In general, when
RESULTS AND DISCUSSION
The general synthetic pathway is depicted in
Scheme 1. Bis(2-oxo-2-phenyl-ethane)sulfide 2 was
taken as a substrate to prepare bis-heterocycles.
In fact, 2 was obtained by the reaction of 2
equivalents of phenacyl bromide 1 with 1 equiv-
alent of Na2S in methanol. Treatment of 2 with
semicarbazide hydrochloride gave bis(1-phenyl-
ethanonesemicarbazone)sulfide 3. The compound 3
displayed bands in the region 3208–3484 (NHCO
and CONH2) and 1635–1650 cm−1 (C N) corre-
Correspondence to: Venkatapuram Padmavathi; e-mail:
vkpuram2001@yahoo.com.
Contract grant sponsor: Department of Science and Technology
(DST) New Delhi, India.
1
c
ꢀ
2008 Wiley Periodicals, Inc.
sponding to a semicarbazone moiety. The H NMR
261

262 Padmavathi et al.
SCHEME 1
spectrum of 3a showed a sharp singlet at 3.95 ppm
for methylene protons and two broad singlets at
9.89 and 6.62 ppm for NH and NH2, respectively,
that disappeared on deuteration. Oxidative cycliza-
tion of 3 with SeO2 in AcOH gave bis(4-phenyl-1,2,3-
selenadiazole-5-yl)sulfide 4. On the other hand, the
Hurd–Mori reaction of 3 with SOCl2 produced bis(4-
phenyl-1,2,3-thiadiazole-5-yl)sulfide 5. The IR spec-
tra of 4 and 5 exhibited bands around 1420–1440
(N N) and 675–720 cm−1 (C Se/S). A multiplet cor-
responding to aromatic protons in the 1H NMR spec-
tra of 4 and 5 was observed in the region 7.20–7.93
ppm. Thus, the absence of a singlet due to a methy-
lene group and broad singlets due to NH and NH2
confirmed their formation. Similarly, the reaction of
2 with 2 equivalents of phenylhydrazine gave bis(1-
phenylethanonephenylhydrazone)sulfide 6. The ab-
sorption bands present in the IR spectra of 6 in
the region 3285–3300 and 1632–1639 cm−1 were as-
signed to NH and C N functional groups, respec-
to −10◦C [7] resulted in bis(2,5-diphenyl-2H-1,2,3-
diazaphosphole-4-yl)sulfide 7. The 1H NMR spec-
trum of 7a displayed a multiplet at 7.12–7.72 ppm
due to aromatic protons. The structures of 4, 5, and
7 were further ascertained by 13C NMR spectra. The
31P NMR spectra of 7 displayed a signal between
−209 and −211 ppm due to the di-coordinated phos-
phorous of 2H-diazaphospholes.
The lead compounds 4, 5, and 7 were tested
for antimicrobial activity at three different con-
centrations 25, 75, and 100 µg per disk. The
compounds were evaluated for antibacterial activ-
ity against Staphylococcus aureus, Bacillus subtilis
(Gram-positive bacteria), and Escherichia coli and
Klebsiella pneumoniae (Gram-negative bacteria) on
nutrient agar plates at 37◦C for 24 h using Gen-
tamycin as a reference drug. The antifungal activ-
ity was screened against Fusarium solani, Curvu-
laria lunata, Asperigillus niger, and Cunninghemella
elegans using Nystatin (25 µg per disk) as a standard
drug. Fungal cultures were grown on potato dextrose
broth at 25◦C for 3 days. Then, the spore suspension
was adjusted to 106 pores mL−1 (fungi) at 0.1 and
0.2 mg mL−1 concentration by using the Vincent and
Vincent method [8].
1
tively. The H NMR spectrum of 6a displayed two
singlets at 2.31 ppm due to methylene protons. Apart
from this, a broad singlet was observed at 9.89 ppm
due to NH that was disappeared on deuteration.
Heterocyclization of 6 with PCl3 in Et3N at −5◦C
Heteroatom Chemistry DOI 10.1002/hc

A New Class of Sulfur-Linked Bis-1,2,3-selenadiazoles, 1,2,3-Thiadiazoles, and 2H-Diazaphospholes 263
All the compounds possessed moderate to high
tallization from aqueous methanol: bis(1-phenyl-
ethanonesemicarbazone)sulfide (1.67 g, 62%): mp
66–68◦C; bis(1-p-tolyl-ethanonesemicarbazone)sul-
fide (2.02 g, 68%): mp 82–84◦C; bis(1-p-chloro-
phenyl-ethanonesemicarbazone)sulfide (2.4 g, 71%):
mp 76–78◦C.
antibacterial activity toward both Gram-positive and
Gram-negative bacteria. In general, all the com-
pounds showed more activity against Gram-positive
bacteria when compared to Gram-negative bacte-
ria. It was also observed that compounds having
diazaphosphole moiety exhibited comparatively
high-antibacterial activity than other compounds.
The results revealed that majority of the synthe-
sized compounds showed various degrees of in-
hibition against the tested microorganisms. The
compounds having diazaphophole moiety exhib-
ited high-antibacterial activity against both Gram-
positive (36–39 mm) and Gram-negative (24–32 mm)
bacteria than the other compounds. The compounds
having selenadiazole and thiadiazole units displayed
moderate activity against both the bacteria (18–
23 mm).
All the test compounds effectively inhibit ger-
mination against tested fungi at higher concentra-
tions. It was observed that there was no marked
difference in antifungal activity of compounds hav-
ing 1,2,3-selenadiazole and 1,2,3-thiadiazole units.
Further bioassay studies on these compounds are in
progress.
Bis(1-phenyl-ethanonesemicarbazone)sulfide (3)
A mixture of 2 (1.0 mmol), semicarbazide hydrochlo-
ride (2.4 mmol), and sodium acetate (2.4 mmol) in
20 mL of ethanol was refluxed for 1–2 h. It was
concentrated, cooled, and poured onto crushed ice.
The separated solid was filtered, washed with wa-
ter, and dried and purified by recrystallization from
methanol.
Bis(1-phenyl-ethanonesemicarbazone)sulfide (3a).
White solid, yield: 68%, mp 101–103◦C. IR(KBr) ν:
1685, 1571 (NHCO), 1635 (C N), 3482, 3215 (NH
and NH2). 1H NMR (DMSO-d6): δ 3.95 (s, 4H, S-CH2),
6.62 (s, 4H, NH2), 7.32–7.83 (m, 10 arom. H), 9.89
(bs, 2H, NH).
Bis(1-p-tolyl-ethanonesemicarbazone)sulfide (3b).
White solid, yield: 62%, mp 111–113◦C. IR(KBr) ν:
1690, 1568 (NHCO), 1642 (C N), 3478, 3210 (NH
and NH2). 1H NMR (DMSO-d6): δ 2.45 (s, 3H, CH3),
3.92 (s, 4H, S-CH2), 6.60 (s, 4H, NH2), 7.62–7.82 (m,
8 arom. H), 9.43 (bs, 2H, NH).
EXPERIMENTAL
Melting points were determined in open capillaries
on a Mel-Temp apparatus and are uncorrected. The
purity of the compounds was checked by TLC (silica
gel H, British Drug House (BDH), ethyl acetate–
hexane (0.5:2)). The IR spectra were recorded on a
Thermo Nicolet IR 200 FT-IR spectrometer as KBr
pellets, and the wave numbers are given in cm−1.
The 1H NMR spectra were recorded in CDCl3/DMSO-
d6 on a Varian EM-360 spectrometer. The 13C NMR
spectra were run on a Varian VXR spectrometer op-
erating at 75.5 MHz with CDCl3 as solvent. All chem-
ical shifts are reported in ppm from TMS as an inter-
nal standard. Microanalyses were performed using
Perkin-Elmer 240C elemental analyzer. The starting
compounds, phenacyl bromides, were prepared as
per the procedure reported earlier [9].
Bis(1-p-chlorophenyl-ethanonesemicarbazone)sulfide
(3c). White solid, yield: 72%, mp 122–124◦C.
IR(KBr) ν: 1695, 1574 (NHCO), 1650 (C N), 3484,
1
3208 (NH and NH2). H NMR (DMSO-d6): δ 3.99
(s, 4H, S-CH2), 6.66 (s, 4H, NH2), 7.38–7.93 (m, 10
arom. H), 9.71 (bs, 2H, NH).
Bis(4-phenyl-1,2,3-selenadiazole-5-yl)sulfide (4)
The compound bis(1-phenyl-ethanonesemicarba-
zone)sulfide 2 (1 mmol) was dissolved in glacial
acetic acid (10 mL) and warmed gently with stir-
ring. To this, selenium dioxide (2 mmol) was added
portionwise during a period of 20 min at 60–70◦C,
and stirring was continued for 4–5 h. The reac-
tion mixture was cooled and poured onto crushed
ice. The separated solid was collected by filtration,
washed with saturated sodium bicarbonate solution
followed by water and dried. The resultant solid
was purified by column chromatography (silica gel,
hexane–ethyl acetate (2:1)).
Bis(2-oxo-2-phenyl-ethane)sulfide (2)
A solution of sodium sulfide (1.1 mmol) in methanol
(25 mL) was taken and stirred at 0–10◦C. To this,
phenacyl bromide 1 (1 mmol) in methanol (30 mL)
was added dropwise while stirring over a period of
30–40 min. The stirring was continued for an addi-
tional period of 3 h, maintaining the same tempera-
ture. The separated solid was collected by filtration,
washed with water, dried and purified by recrys-
Bis(4-phenyl-1,2,3-selenadiazole-5-yl)sulfide (4a).
Red solid, yield: 65%, mp 130–132◦C. IR (KBr) ν: 712
1
(C Se), 1437 (N N). H NMR (DMSO-d6): δ 7.32–
Heteroatom Chemistry DOI 10.1002/hc

264 Padmavathi et al.
7.56 (10H, m, Harom). 13C NMR (DMSO-d6): δ 145.5
(C-5), 154.6 (C-4), 127.4, 128.9, 132.2, 134.7 (aro-
matic carbons). Anal. Calcd for C16H10N4SSe2
(448.26): C, 42.87; H, 2.25; N, 12.50. Found: C, 42.98;
H, 2.20; N, 12.62.
Calcd for C18H14N4S3 (382.53): C, 56.52; H, 3.69; N,
14.65. Found: C, 56.38; H, 3.65; N, 14.60.
Bis(4-p-chlorophenyl-1,2,3-thiadiazole-5-yl)sulfide
(5c). White solid, yield: 76%, mp 168–170◦C.
IR(KBr) ν: 714 (C S), 1436 (N N). 1H NMR
(DMSO-d6): δ 7.58–7.90 (m, 8 arom. H); 13C NMR
(DMSO-d6): δ 141.5 (C-5), 152.7 (C-4), 126.3, 127.7,
131.9, 133.3 (aromatic carbons). Anal. Calcd for
C16H8Cl2N4S3 (423.37): C, 45.39; H, 1.90; N, 13.23.
Found: C, 45.31; H, 1.99; N, 13.32.
Bis(4-p-tolyl-1,2,3-selenadiazole-5-yl)sulfide (4b).
Red solid, yield: 71%, mp 126–128◦C. IR (KBr) ν:
699 (C Se), 1432 (N N). 1H NMR (DMSO-d6): δ 2.25
(s, 6H, CH3), 7.21–7.63 (m, 8 arom. H).13C NMR
(DMSO-d6): δ 26.7 (Ar-CH3), 144.8 (C-5), 154.3 (C-4),
126.1, 128.4, 132.9, 133.5 (aromatic carbons). Anal.
Calcd for C18H14N4SSe2 (476.32): C, 45.39; H, 2.96;
N, 11.76. Found: C, 45.54; H, 3.00; N 11.73.
Bis(1-phenyl-ethanonephenylhydrazone)sulfide (6)
To a solution of bis(2-oxo-2-phenyl-ethane)sulfide
2 (1 mmol) in ethanol (15 mL), phenylhydrazine
(2.2 mmol) was added and refluxed for 2–3 h. The
reaction mixture was concentrated and cooled. The
solid separated was filtered, washed with water,
dried, and purified by recrystallizition from ethanol.
Bis(4-p-chlorophenyl-1,2,3-selenadiazole-5-yl)-
sulfide (4c). Red crystals, yield: 62%, mp 138–
140◦C. IR(KBr) ν: 719 (C Se), 1439 (N N). 1H NMR
(DMSO-d6): δ 7.41–7.93 (m, 8 arom H). 13C NMR
(DMSO-d6): δ 146.3 (C-5), 155.1 (C-4), 125.4, 128.1,
131.5, 133.9 (aromatic carbons). Anal. Calcd for
C16H8Cl2N4SSe2 (517.15): C, 37.16; H, 1.56; N, 10.83.
Found: C, 37.04; H, 1.51; N, 10.94.
Bis(1-phenyl-ethanonephenylhydrazone)sulfide (6a).
White solid, yield: 69%, mp 112–114◦C. IR(KBr) ν:
1635 (C N), 3285 (NH). 1H NMR (DMSO-d6): δ 2.31
(s, 4H, S-CH2), 7.32–7.83 (m, 20 arom. H), 9.89 (bs,
2H, NH).
Bis(4-phenyl-1,2,3-thiadiazole-5-yl)sulfide (5)
Bis(1-p-tolyl-ethanonephenylhydrazone)sulfide (6b).
White solid, yield 77%, mp 121–124◦C. IR(KBr) ν:
1632 (C N), 3290 (NH). 1H NMR (DMSO-d6): δ 2.21
(s, 6H, CH3), 2.35 (s, 4H, S-CH2), 7.62–7.81 (m, 18
arom. H), 9.75 (bs, 2H, NH).
To a well-cooled solution of bis(1-phenyl-ethanone-
semicarbazone)sulfide 2 (1 mmol) in dichloro-
methane (20 mL), an excess of thionyl chloride
(9 mL) was added portionwise while stirring and the
mixture was allowed to attain room temperature.
After stirring for 2–3 h, the excess thionyl chlo-
ride was decomposed with cold saturated sodium
carbonate solution. The organic layer was sepa-
rated, washed with water, and dried over anhydrous
Na2SO4. The solvent was removed in vacuo. The re-
sultant solid was purified by column chromatogra-
phy (silica gel, hexane–ethyl acetate, (2:0.5)).
Bis(1-p-chlorophenyl-ethanonephenylhydrazone)-
sulfide (6c). White solid, yield: 75%, mp 135–
1
137◦C. IR(KBr) ν 1639 (C N), 3300 (NH). H NMR
(DMSO-d6): δ 2.40 (s, 4H, S-CH2), 7.52–7.93 (m, 18
arom. H), 9.71 (bs, 2H, NH).
Bis(2,5-diphenyl-2H-1,2,3-diazaphosphole-4-yl)
sulfide (7)
Bis(4-phenyl-1,2,3-thiadiazole-5-yl)sulfide (5a).
White solid, yield: 65%, mp 146–148◦C. IR (KBr)
To a well-cooled solution of phosphorus trichloride
(3 mmol) in dry ether (15 mL) under nitrogen atmo-
sphere maintained at –5 to –10◦C, the compound 6
(1 mmol) in dry ether (10 mL) was added dropwise
and stirred well. To this, triethylamine (1.2 mmol)
was added and stirring was continued for 3–4 h. The
ethereal layer was separated, washed with sodium
bicarbonate solution, water and dried over anhy-
drous Na2SO4. The solvent was removed in vacuo.
The resulting solid was purified by column chro-
matography (silica gel, hexane–ethyl acetate (2:1)).
1
ν: 677 (C S), 1432 (N N). H NMR (DMSO-d6): δ
7.42–7.86 (m, 10 arom H). 13C NMR (DMSO-d6): δ
142.7 (C-5), 152.3 (C-4), 125.5, 127.3, 131.4, 133.6
(aromatic carbons). Anal. Calcd for C16H10N4S3
(354.48): C, 54.21; H, 2.84; N, 15.81. Found: C,
54.33; H, 2.90; N, 15.75.
Bis(4-tolyl-1,2,3-thiadiazole-5-yl)sulfide
(5b).
White solid, yield: 74%, mp 152–154◦C. IR(KBr) ν:
683 (C S), 1422 (N N). 1H NMR (DMSO-d6): δ 2.35
(6H, s, CH3), 7.20–7.45 (m, 8 arom. H). 13C NMR
(DMSO-d6): δ 25.4 (Ar-CH3), 140.3 (C-5), 151.6 (C-4),
125.8, 126.6, 129.2, 132.4 (aromatic carbons). Anal.
Bis(2,5-diphenyl-2H-1,2,3-diazaphosphole-4-yl)-
sulfide (7a). White solid, yield: 64%, mp 166–
Heteroatom Chemistry DOI 10.1002/hc

A New Class of Sulfur-Linked Bis-1,2,3-selenadiazoles, 1,2,3-Thiadiazoles, and 2H-Diazaphospholes 265
168◦C. IR(KBr) ν: 1629 (C N). 1H NMR (DMSO-d6):
[3] Lathorp, K. A.; Harpet, P. V.; Malkinson, F. D.
δ 7.12–7.72 (m, 20 arom. H). 13C NMR (DMSO-d6):
δ 146.3 (C-5), 159.7 (C-4, Jcp = 54 Hz), 115.1, 118.5,
128.6, 129.0, 129.3, 130.8, 131.2, 134.7 (aromatic
carbons). Anal. Calcd for C28H20N4P2S (506.50): C,
66.40; H, 3.98; N, 11.06. Found: C, 66.32; H, 3.92; N,
11.16.
Strahlen 6 Therupie [Sanderb] 1968, 67, 436–443.
[4] (a) Hunt, D. E.; Pittillo, R. F. Antimicrob Agents
Chemother 1966, 551–554; (b) Shealy, Y. F.; Clayton,
J. D.; Dixon, D. J E.; Dulmadge, A.; Pittillo, R. F.;
Hunt, D. E. Bio Chem Pharmacol 1966, 15, 1610–
1614; (c) Bayoumy, B. E.; Abd-Alla, M. A.; Ahmed,
A. N. Bull Pharm Sci 1986, 9, 66; (d) Bayoumy, B. E.;
Sayed, I.; Lech, S. Bull Pol Acad Sci Chem 1991, 39,
449–454.
Bis[2-phenyl(5-p-tolyl-2H-1,2,3-diazaphosphole-4-
yl)sulfide (7b). White solid, yield: 67%, mp 152–
154◦C. IR(KBr) ν: 1638 (C N). 1H NMR (DMSO-d6):
δ 2.31 (s, 6H, –CH3), 7.10–7.68 (m, 18 arom. H). 13C
NMR (DMSO-d6): δ 25.4 ( CH3), 145.9 (C-5), 156.8
(C-4, Jcp = 53 Hz), 114.7, 116.3, 129.1, 129.8, 130.4,
131.2, 132.5, 135.2 (aromatic carbons). Anal. Calcd
for C30H24N4P2S (534.55): C, 67.41; H, 4.53; N, 10.48.
Found: C, 67.50; H, 4.58; N, 10.57.
[5] (a) Gil, D. L.; Wilkinson, C. F. Pestic Biochem Physiol
1976, 6, 338–449; (b) Lewis, G. S.; Nelson, P. H. J Med
Chem 1979, 22, 1214–1218; (c) Lee, V. J.; Curran,
W. V. Eur Patent 1988, 252, 474; Chem Abstr 1988,
108, 204627t; (d) Patil, B. M; Badami, B. V.; Puranik,
G. S. Indian J Heterocycl Chem 1994, 3, 193–196;
(e) Kenji, T.; Takashi, S.; Osami, S.; Yoshitaka, T.;
Kazyhiro, T. J P Appl 96/ 278, 948 (1996); Chem Abstr
1998, 128, 257436z.
[6] (a) Bhaskar Reddy, D.; Somasekhar Reddy, A.;
Padmavathi, V. Phosphorus Sulfur Silicon 1997,
122, 143–150; (b) Bhaskar Reddy, D.; Ramana Reddy,
M. V.; Padmaja, A.; Padmavathi, V. Indian J Hetero-
cycl Chem 1998, 7, 259–262; (c) Bhaskar Reddy, D.;
Ramana Reddy, M. V.; Padmavathi, V. Heteroatom
Chem 1999, 10, 17–23; (d) Bhaskar Reddy, D.;
Bis[2-phenyl(5-p-chlorophenyl-2H-1,2,3-diaza-
phosphole-4-yl)sulfide (7c). White solid, yield: 72%,
mp 175–177◦C. IR(KBr) ν: 1641 (C N). 1H NMR
(DMSO-d6): δ 7.21–7.73 (m, 18 arom. H). 13C NMR
(DMSO-d6): δ 146.4 (C-5), 157.6 (C-4, Jcp = 57 Hz),
115.4, 118.9, 128.1, 129.5, 129.9, 130.4, 131.6, 136.3
(aromatic carbons). Anal. Calcd for C28H18Cl2N4P2S
(575.39): C, 58.45; H, 3.15; N, 9.74. Found: C, 58.57;
H, 3.18; N, 9.70.
Somasekhar
Reddy,
A.;
Padmavathi,
V.;
Chandrasekhar Babu, N. Heterocycl Commun
2000, 6, 271–274; (e) Bhaskar Reddy, D.; Balaiah,
A.; Padmavathi, V.; Padmaja, A. Synth Commun
31, 2001, 3265–3272; (f) Padmavathi, V.; Ramana
Reddy, T. V.; Balaiah, A.; Audisesha Reddy, A.;
Bhaskar Reddy, D. Phosphorus Sulfur Silicon 2002,
177, 1223–1235; (g) Padmavathi, V.; Ramana Reddy,
T. V.; Audisesha Reddy, K.; Bhaskar Reddy, D. J
Heterocycl Chem 2003, 40, 149–153.
REFERENCES
[7] Luber, J.; Schmidpeter, A. Angew Chem, Int Ed Engl
1976, 15, 111–112.
[8] Vincent, J. C.; Vincent, H. W. Proc Soc Exp Biol Med
1944, 55, 162–164.
[9] Schevchuk, M. I.; Dombrovskii, A. V. Zh Obesch
Khim 1963, 33, 1135.
[1] Schatz, V. B. Medicinal Chemistry, 2nd ed.; Wiley-
Interscience: New York, 1960.
[2] Klayman, D. L.; Gunther, W. H. H. Organo Selenium
Compounds. Their Chemistry and Biology; Wiley-
Interscience: New York, 1972.
Heteroatom Chemistry DOI 10.1002/hc