Diverse synthetic approach for sulfur and nitrogen-containing spiroheterocycles from dimedone and their pharmacological evaluation

Article abstract of DOI:10.1080/00397911.2019.1650281

Novel spiro(3-hydroxy-5,5-dimethyl)-1,5’-(2’-substituated[1,3,4]-oxadiazole/thiadiazolo[3,2-c] thiazolines and 3-hydroxy-5,5-dimethyl-spiro[cyclohex-2-ene-thiazolo/thiazino[3,2-b]-s-tetrazine were prepared from previously reported hydrazone, semicarbazone, carbazone, and spiro-s-tetrazine intermediates derived from dimedone precursor. All the newly synthesized heterocycles have been characterized by analytical and spectral (¹H NMR and ^hC NMR) data and screened their in vitro antibacterial activity against gram negative bacteria Escherichia coli and gram positive bacteria Staphylococcus aureus. Some of the compounds showed moderate to good activities towards the bacteria chosen.

Full text of DOI:10.1080/00397911.2019.1650281

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: https://www.tandfonline.com/loi/lsyc20
Diverse synthetic approach for sulfur and
nitrogen-containing spiroheterocycles from
dimedone and their pharmacological evaluation
Prajna Parimita Mohanta, Sankarshan Sahu, Poulomi Majumdar & Ajaya
Kumar Behera
To cite this article: Prajna Parimita Mohanta, Sankarshan Sahu, Poulomi Majumdar &
Ajaya Kumar Behera (2019): Diverse synthetic approach for sulfur and nitrogen-containing
spiroheterocycles from dimedone and their pharmacological evaluation, Synthetic Communications,
DOI: 10.1080/00397911.2019.1650281
To link to this article: https://doi.org/10.1080/00397911.2019.1650281
View supplementary material
Published online: 09 Aug 2019.
Submit your article to this journal
Article views: 2
View Crossmark data
Full Terms & Conditions of access and use can be found at
https://www.tandfonline.com/action/journalInformation?journalCode=lsyc20

R
SYNTHETIC COMMUNICATIONSV
https://doi.org/10.1080/00397911.2019.1650281
Diverse synthetic approach for sulfur and nitrogen-
containing spiroheterocycles from dimedone and their
pharmacological evaluation
Prajna Parimita Mohanta, Sankarshan Sahu, Poulomi Majumdar, and Ajaya
Kumar Behera
1Organic Synthesis Laboratory, School of Chemistry, Sambalpur University, Burla, India
ABSTRACT
ARTICLE HISTORY
Received 21 January 2019
Novel spiro(3-hydroxy-5,5-dimethyl)-1,5’-(2’-substituated[1,3,4]-oxadia-
zole/thiadiazolo[3,2-c] thiazolines and 3-hydroxy-5,5-dimethyl-spiro[-
cyclohex-2-ene-thiazolo/thiazino[3,2-b]-s-tetrazine were prepared
from previously reported hydrazone, semicarbazone, carbazone, and
spiro-s-tetrazine intermediates derived from dimedone precursor. All
the newly synthesized heterocycles have been characterized by ana-
KEYWORDS
Dimedone; hydrazone;
semicarbazone; thiosemicar-
bazone; spiro-s-tetrazine
h
lytical and spectral (1H NMR and C NMR) data and screened their in
vitro antibacterial activity against gram negative bacteria Escherichia
coli and gram positive bacteria Staphylococcus aureus. Some of the
compounds showed moderate to good activities towards the bac-
teria chosen.
GRAPHICAL ABSTRACT
X
S
HO
HO
NNHC R
X
N
N
R
O
O
H
S
N
S
N
HN
HN
HO
HO
NH
N
N
H
N
H
Introduction
Spiro heterocycles containing nitrogen, oxygen, and sulfur have numerous applications
in the field of agriculture, pharmacy, and industries. In fact, they are used as antifungal
agents,[1] pesticides,[2] laser dyes,[3] and electroluminescent devices.[4] The syntheses of
CONTACT Ajaya Kumar Behera
ajaykumar.behera@yahoo.com
Organic Synthesis Laboratory, School of
Chemistry, Sambalpur University, Jyoti Vihar, Burla, Odisha 768019, India.
Supplemental data for this article can be accessed on the publisher’s website.
ß 2019 Taylor & Francis Group, LLC

2
P. P. MOHANTA ET AL.
spiroheterocycles put forth an interesting synthetic challenge to organic chemists due to
its structural rigidity and complexity which increases the affinity towards proteins by
reducing the loss of conformational entropy.[5] Hence, a molecule with spiro-center
could be a good starting point for any synthetic method to generate diversified complex
spiroheterocycles and very useful to any drug discovery program.[6] Often, the deter-
mination of the pharmacological properties,[7–9] reduction of side-effects of drugs,[10] or
development of the technical characteristics of materials[11,12] occurs by incorporating
the sulfur-containing rings into the structure of compounds. Thiazole and thiazolidi-
none scaffold have featured as antibacterial,[13,14] antifungal,[13,15] antimicrobial,[16] anti-
inflammatory,[17] antitubercular,[18] and antiviral[19] agents. It has been extensively
reported that presence of arylazo, sulfamoylphenylazo, or phenylhydrazono moieties at
different positions of the thiazolidone ring enhance the antimicrobial activity and its
antibacterial activity may be due to its inhibitory activity of enzyme Mur B which is act-
ing as precursor during the biosynthesis of peptidoglycan.[20] Compounds containing
1,3,4-oxadiazole motif have been evaluated as antimicrobial, antitubercular, anticonvul-
sant, anticancer, antidiabetic activity and activity against snake venom.[21–30] Indeed,
1,2,4,5-tetrazine skeleton possesses a wide range of biological and pharmaceutical activ-
ities such as antimalarial, analgesic, antiinflammatory, antibacterial, antifungal, antiviral
and antitumor activity.[31–36] Thus, the exploration for novel spiro heterocyclic analogs
from the enolised dimedone precursor[37] continues to our area of research by incorpo-
rating various bioactive heterocyclic moieties into the spiro framework expecting the
enhancement in the biological activity. In our continuing interest in synthesizing spiro
heterocycles, herein, novel spiro thiazolidinone and its annulated spiro oxadiazolo/thia-
diazolo [3,2-c] thiazolines have been synthesized from their previously reported imine
functionalized compounds of dimedone. Further, the synthesis of spiro thiazolo/thia-
zino-s-tetrazine has also been explored via known spiro-s-tetrazine intermediate of
dimedone. The newly synthesized spiro thiazolidinone, respective spiro oxadiazolo/thia-
diazolo [3,2-c] thiazolines and spiro thiazolo/thiazino-s-tetrazine were characterized by
1
1H NMR and 13C NMR spectra. In addition, the H NMR spectra of earlier reported
hydrazone, semicarbazone, carbazone, and spiro-s-tetrazine are recorded for structural
elucidation.
Results and discussion
An acid-catalyzed condensation was performed by taking dimedone 1 and benzoyl
hydrazine, semicarbazide, thiosemicarbazide, and 4-phenyl thiosemicarbazide to afford
the respective hydrazone 3 (a: X ¼ O, R ¼ Ph), semicarbazone (b: X ¼ O; R ¼ NH2), thi-
osemicarbazone (c: X ¼ S; R ¼ NH2) and phenylthiosemicarbazone (d: X ¼ S;
1
R ¼ NHPh) as per the reported procedure (Scheme 1).[38] The H NMR spectrum of 3a
(X ¼ O, R ¼ Ph) reveals a sharp singlet at d 0.83 corresponding to six protons of gem
methyl groups at C-5. Another two singlets along with a broad singlet centered at d
5.04, 5.6, and 8.1 (exchangeable with D2O) are assignable to olefinic proton at C-2, ben-
zamido NH, and enolic OH proton at C-3, respectively. Two separate multiplets appear-
ing in the range of d 2.07–2.2 and 2.30–2.33 correspond to two protons of each
methylene groups at C-4 and C-6. Besides, two multiplets at d 7.12–7.26 and 7.62–7.66

R
SYNTHETIC COMMUNICATIONSV
3
X
X
X
HO
NNHC R
NNHC R
R
CHNN
O
O
RC:XNHNH2
RC:XNHNH2
X
MeOH/AcOH,
reflux, 5 h
MeOH/AcOH,
reflux, 5 h
3 (a-d)
3a: X = O, R = Ph
1
2 (a-d)
3b: X = O, R = NH2
3c: X = S, R = NH2
3d: X = S, R = NHPh
Scheme 1. Synthetic route for compounds 3a–d.
X
S
S
HO
NNHC R
O
HO
HO
HSCH2COOH
DMF, 130oC-135oC, 8 h
X
N
N
Conc. H2SO4
NHC R
N
R
3 (a-d)
4 (a-d)
X
5 (a-d)
a: X = O, R = Ph
b: X = O, R = NH2
c: X = S, R = NH2
d: X = S, R = NHPh
Scheme 2. Synthetic route for compounds 5(a–d).
are assigned to two and three phenyl protons. These spectral data are well compatible
to the formation of monobezamidoimino derivative 3a. In compound 3b and 3c, two
broad singlets are appeared at d 6.74 and 6.62 for terminal –NH2, respectively. A mutip-
let at d 7.39–7.56 and a broad singlet at d 8.07 are assignable to the phenyl protons and
phenyl amino proton in compound 3d (X ¼ S; R ¼ NHPh).Thus, the mono hydrazone
and carbazone derivatives 3a–d produced from dimedone instead of the expected bis
hydrazone and carbazone derivatives 2a–d conclude the existence of its enol form.[39]
The hydrazone/semicarbazone/thiosemicarbazone derivatives of dimedone 3a–d are
refluxed with equimolar amount of thioglycolic acid in methanol to afford spiro thiazo-
lidinone derivatives 4a–d (Scheme 2). The IR spectrum of 4a (X ¼ O; R ¼ Ph) shows
two carbonyl stretching frequencies at 1726 and 1664 cmꢀ1 corresponding to carbonyl
1
function of thiazolidinone moiety and the carbonyl group of benzamido unit. The H
NMR spectrum of 4a (X ¼ O; R ¼ Ph) shows two separate pronounced singlets centered
at d 1.12 and 3.71 corresponding to respective six protons of two methyl groups at C-5
and methylene protons of S–CH2–CO unit of thiazolidinone ring. The benzamido –NH
proton and enolic proton exchangeable with D2O appear as broad singlets at d 8.02 and
9.69, respectively. The three distinct multiplets centered at d 2.52–2.63, 2.67–2.8, and
7.25–7.49 are attributed to two protons of each methylene group at C-4, C-6, one ole-
finic proton, C-2, and five phenyl protons, respectively, which are in accordance with
the proposed spiro product 4a. In fact, in compound 4b (X ¼ O; R ¼ NH2) and 4c
(X ¼ S; R ¼ NH2) two characteristic broad singlets exchangeable with D2O at d 7.96 and
8.13 are attributable to terminal NH2, respectively. One broad singlet appears in the
downfield region at d 8.16 for phenyl amino proton and a mutiplet at d 7.32–7.56 is
assignable to the phenyl protons in compound 4d (X ¼ S; R ¼ NHPh).

4
P. P. MOHANTA ET AL.
H
11
10
H
N
H
N
S
N
S
S
HN
9
HN
8
NH
NH
HO
O
O
7
2
3
1
NH2NHCSNHNH2
NH2NHCSNHNH2
EtOH, 3 h
NH
HN
N
N
H
X
N
H
5
H
4
6
EtOH, 3 h
7
1
6
Scheme 3. Synthetic pathway for the preparation of spiro-s-tetrazine 7.
The 13C NMR spectrum of 4a gives characteristic signals at d 196.40, 150.73, and
147.64 for respective carbon attached to –OH group, carbonyl carbon of thiazolidinone
ring and amidic carbonyl carbon. Signals at d 135.78, 128.79, 128.22, and 127.84 are
attributed to the aromatic carbons of the phenyl ring. The olefinic carbon appears at d
107.04, whereas the spiro carbon resonates at d 50.74. The other five signals are featured
to quaternary carbon, three methylene carbons, and methyl carbon at d 41.99, 37.73,
32.46, 29.37, and 27.38. In compounds 4b, 4c, and 4d, signals at d 141.43, 181.38, and
176.42 along with a bunch of signals between d 127.54 and 136.18 are arise due to
–CONH2, –CSNH2, –CSNH–, and aromatic carbons, respectively.
The spiro heterocycles 4a–d on treatment with cold conc. H2SO4 undergoes dehydra-
tive cyclization to form spiro oxadiazolo/thiazolo[3,2-c]thiazoline derivatives 5a–d
(Scheme 2). The disappeance of ꢀ(C ¼ O)str and (N–H)str in the IR region of and
appearance of ꢀ(C ¼ N)str at 1600 cmꢀ1 occurred after the formation of compound 5a
1
(X ¼ O; R ¼ Ph). In the H NMR spectrum of 5a, the disappearance of a singlet for two
methylene protons at d 3.71 of thiazolidinone moiety and appearance of new distinct
singlet at d 7.05 for S–CH ¼ C– unambiguously suggest the annulation of thiazoline
with oxadiazole moiety. Similarly, the olefinic protons of thiazolidinone moiety appear
at d 6.13, 5.82, and 6.85 for 5b (X ¼ O; R ¼ NH2), 5c (X ¼ S; R ¼ NH2) and 5d (X ¼ S;
R ¼ NHPh), respectively. In 13C NMR spectrum of 5a, signals at d 194.67, 156.45,
153.45, 114.38, and 97.42 are attributed to carbon attached to –OH group, azomethaine
carbon, –N–C–O– carbon, olefinic carbon of cyclohexene unit and S–CH ¼ carbon.
Signals at d 51.16, 45.95, 42.28, 39.87, 34.38, and 30.97 are assigned to spiro carbon,
quarternary carbon, methylene crbons, carbon attached to S-atom of thiazole ring and
methyl carbons, respectively. Azomethaine carbon in 5b and 5c appear at d 141.78 and
153.38 in downfield region. In 5d, phenyl carbons appear at d 147.95, 131.74, 121.02,
119.56, and 115.84.
Dimedone 1 on condensation with thiocarbohydrazide yielded similar type of enol-
ised mono spiro-s-tetrazine intermediate 7 (Scheme 3). The IR spectrum of the struc-
ture 7 shows two characteristic peaks at 3184 cmꢀ1 and 1222 cmꢀ1 corresponding to
1
ꢀ(N–H)str and ꢀ(C ¼ S)str, respectively. The H NMR spectrum of 7 displays three
broad singlets at d 5.28, 8.6, and 9.5 assignable to two protons at N-7 and N-11, two
protons at N-8, and N-10 and enolic OH proton(exchangeable with D2O), respectively.
Besides, a sharp singlet at d 6.05 is corresponding to olefinic proton at C-2. Moreover,
appearance of two singlets at d 0.98 and 1.09 for three protons of each methyl groups
at C-5 and two separate multiplets centered at d 2.18–2.43 and 2.81–3.02 are attributed
to each methylene protons at C-4 and C-6, respectively, to confirm the formation of
spiro-s-tetrazine derivative 7. It is further evident from its EI-MS spectrum, which gives
[M þ 1] peak at m/z 229.

R
SYNTHETIC COMMUNICATIONSV
5
O
S
N
HN
ClCH2COOH
HO
HO
N
CH3COONa, EtOH, 7 h
N
H
8
Ph
S
N
PhCOCH2Br
EtOH, 6 h
HN
N
N
H
H
N
S
HN
HO
9
NH
N
H
S
N
7
BrCH2CH2Br
EtOH, 6 h
HN
HO
HO
N
N
H
10
S
N
HN
BrCH2CH2CH2Br
EtOH, 6 h
N
N
H
11
Scheme 4. Synthetic pathway for the preparation of compound 8–11.
The equimolar mixture of the spiro-s-tetrazine 7 with chloroacetic acid/anhydrous
sodium acetate, phenacylbromide, 1,2-dibromoethane and 1,3-dibromopropane in etha-
nol was refluxed to afford 8–11, respectively, in good yield (Scheme 4).
The IR spectrum of 8 shows a carbonyl stretching frequency at 1732 cmꢀ1 indicating
the installation of thiozolidinone moiety in spiro-s-tetrazine framework. Disappearance
of the broad singlet at d 8.6 of two protons at N-8 and N-10 and appearance of a char-
1
acteristic sharp singlet d 3.23 corresponding to S–CH2–CO– protons occur in the H
NMR spectrum after formation of compound 8. The 13 C NMR spectrum of compound
8 shows four signals at d 189.59, 158.96, 147.35, and 113.22 assignable to the carbon
attached to –OH group, carbonyl carbon, azomethaine carbon, and olefinic carbon of
cyclohexene moiety, respectively. The spiro carbon, quarternary carbon, two methylene
carbons, one methylene carbon of thiazolidinone ring, and methyl carbons appear sig-
nals at d 55.83, 48.05, 45.25, 38.19, 34.87, and 30.17. The appearance of a distinct singlet
at d 7.09 for compound 9 is assignable to –S–CH ¼ proton. In the 13C NMR spectrum
of the same compound, signals at d 190.59, 148.76, 138.61, 132.42, 126.20, 124.01, and
122.63 are attributed to carbon attached to –OH group, –N–C–S– carbon and phenyl
carbons. The olefinic carbon of cyclohexene moiety, spiro carbon, quarternary carbon,
¼C–S– carbon, two methylene carbons, and methyl carbons show signals at d 113.72,
1
55.82, 49.45, 46.05, 37.85, 35.97, and 31.87, respectively. The H NMR spectrum of 10
shows two separate characteristics triplets centered at d 2.45 and 3.55 assignable to
S–CH2 and N–CH2 protons. In the 13C NMR spectrum of compound 10, the signals at
d 188.78, 148.68, and 112.25 are observed due to carbon attached to –OH group,

6
P. P. MOHANTA ET AL.
α
CHAr
O
O
β
H
ClCH2COOC2H5, EtOH
S
N
S
S
N
N
HN
ArCHO, EtOH
Piperidine, 5 h
pyridine
HN
HN
HO
HO
HO
NH
N
N
N
H
ArCHO, Piperidine, 7 h
N
N
H
H
7
8
12(a-d)
Ar= C6H5, p- MeOC6H4, p-ClC6H4, p-NO2C6H4
Scheme 5. Synthetic pathway for the preparation of compound 12(a–d).
–N–C–S– carbon and olefinic carbon of cyclohexene ring. The spiro carbon, quarter-
nary carbon, N–CH2 carbon, two methylene carbons of cyclohexene unit, S–CH2 car-
bon, and methyl carbons resonate at d 55.79, 54.76, 47.45, 44.95, 38.17, 31.87, and
1
30.01, respectively. In H NMR spectrum of compound 11, three distinct mutiplets at d
1.62–1.68, 2.11–2.19, and 2.72–2.82 arise due to three different methylene protons
besides other signals as observed in 10. In upfield region, one extra methylene carbon
appearing at d 33.89 for compound 11 along with other usual signals is agreeable to the
proposed structure.
Further, the synthesis of 12a–d was explored either by one pot-three component reac-
tion of 7, ethylchloroacetate and arylaldehyde in presence of piperidine or by condensa-
tion of 8 with arylaldehyde in presence of piperidine in ethanol (Scheme 5).
The bathochromic shift in the carbonyl stretching frequency from 1732 to 1718 cmꢀ1
in the IR spectrum of 12a (Ar ¼ C6H5) ensures the insertion of exo-olefinic double
bond in conjugation of the carbonyl function. Appearance of a new sharp singlet at d
1
8.15 and a multiplet at d 6.95–7.40 for exo-olefinic and phenyl protons in the H NMR
spectrum of 12a (Ar ¼ C6H5) suggest the formation of the benzylidene derivative. In
13C NMR spectrum, the same compound display signals at d 192.85, 161.47, 149.20, and
134.71 due to the presence of carbon attached to –OH group, carbonyl carbon,
–N–C–S– carbon and exo-olefinic carbon, respectively. The signals for phenyl carbons
at d 133.07, 131.38, 128.72, and 126.4 and other characteristic signals in 13C NMR at d
115.38, 106.20, 55.97, 49.02, 47.15, 36.01, and 32.07 assignable to two a, b-carbons, spiro
carbon, quarternary carbon, two methylene carbons, and methyl carbons, respectively,
add to the conformity of the proposed structure. The analytical and spectral data of ary-
lidene derivative 12a formed by two methods are superimposable. Similarly, singlets
1
appear at d 7.63, 7.71, and 7.96 for exo-olefinic protons in the H NMR spectra of 12b
(Ar ¼ C6H5OMe), 12c (Ar ¼ C6H4Cl) and 12d (Ar ¼ C6H4NO2) in addition to the other
usual signals. In 13C NMR spectra of 12b, 12c, and 12d the exo-olefinic carbons show
signals at d 134.71, 134.84, and 135.14, respectively.
The spectral analyses conclude that the –NH–CS–NH– fragment of s-tetrazine moi-
ety undergoes thione ꢀ thiol tautomerism to generate ambident nucleophile for attack-
ing nucleophilic centers of chloroacetic acid, phenacyl bromide, dibromoethane, and
dibromopropane for cyclization. The analytical and spectral data of these five deriva-
tives 8–12 available in supporting information are compatible with the pro-
posed structures.

R
SYNTHETIC COMMUNICATIONSV
7
Antimicrobial activity
The synthesized compounds were screened for their antibacterial activity in vitro against
gram positive bacteria Staphylococcus aureus and gram negative bacteria Escherichia coli
by Disk diffusion method using Kanamycin sulfate as standard. The antimicrobial sus-
ceptibility test discs were prepared using Muller Hinton Agar which utilize in the
Bauer–Kirby method[40] for rapidly growing aerobic organisms. The American test cul-
ture center (ATCC) standardized antibiotic discs[41] were used for the standard drug.
The spiro heterocylic derivatives impregnated filter paper disks were prepared by using
different concentration of compounds in DMSO to determine the minimal inhibitory
concentration (MIC). The lowest concentration (400 mg/ml) inhibiting growth of the
organism was recorded as the MIC. The zone of inhibition was measured in mm. The
zones of inhibition of the standard drug and the synthesized compounds were summar-
ized in Table S39 (Supplemental Materials). Running control with pure DMSO only
which was used as solvent has shown no effect. Most of the compounds showed moder-
ate activities towards the bacteria chosen. Compounds such as 5d, 9, 10, and 12b
showed pronounced activities as compared to the standard drugs used. The results con-
firmed that the antibacterial activity of the synthesized compounds increase after inser-
tion of the thiadiazole and oxadiazole units into the spiro-thiazolidinone scaffold. In
case of spiro-s-tetrazine derivatives, the activity also enhances after incorporation of
thiazole and thiazolidinone moieties. But, the compound having methoxy substituent
has better activity as compared to the chloro substituent.
Conclusion
The successful exploration for diverse spiro heterocycles of hydrazone, semicarbazone,
thiosemicarbazones, and s-tetrazine has been carried out from dimedone precursor. The
developed protocols were further extended by incorporating the oxadiazole, thiadiazole
moiety in spirothiazolidinone scaffold and thiazole, thiazine moiety in spiro-s-tetrazine
framework, respectively. Screening of all the synthesized compounds for their antibac-
terial activity against gram negative bacteria E. coli and gram positive bacteria S. aureus
was performed. Some of them exhibits moderate to good activities and few are found
very active against the same microorganism.
Experimental
General procedure for preparation of hydrazone/semicarbazone/
thiosemicarbazone derivatives of dimedone (3a–d)
To a solution of dimedone 1 (0.01 mol) and benzoyl hydrazine/semicarbazide/thiosemi-
carbazide/4-phenyl thiosemicarbazide (0.01 mol) in methanol, 10 drops of acetic acid
were added and the reaction mixture was refluxed for 5 h. The completion of the reac-
tion was monitored using TLC. Then, it was concentrated, cooled and poured into satu-
rated ice cold solution of sodium bicarbonate. The precipitate 3a–d thus obtained was
filtered, dried and recrystallized from methanol.

8
P. P. MOHANTA ET AL.
General procedure for preparation of 9,9-dimethyl-7-hydroxy-4-(N-substituated)-3-
oxo-1-thia-4-aza-spiro-[4,5]dec-6-ene (4a–d)
The solution of hydrazone/semicarbazone/thiosemicarbazone derivative of dimedone 3a
(0.001 mol) and thioglycolic acid (0.001 mol) in DMF (5 mL) was refluxed at 130ꢁ–135ꢁ
C for 8 h. The completion of the reaction was monitored using TLC. Subsequently, the
reaction mixture was cooled and poured into ice cold water. The compound 4a–d thus
obtained was filtered, dried and recrystallized from ethanol.
General procedure for preparation of spiro(3-hydroxy-5,5-dimethyl)-1,5’-(2’-
substituated[1,3,4]-oxadiazole/thiadiazolo[3,2-c] thiazolines (5a–d)
Slurry of the spiro derivative 4a–d (0.001 mol) with conc. H2SO4 was prepared and kept
overnight on ice bath. Afterward, the reaction mixture was poured into ice cold water.
The solution was neutralized with few drops of liquor ammonia and the precipitate
5a–d thus obtained was filtered, dried, and recrystallized from rectified spirit.
Preparation of 3-hydroxy-5,5-dimethyl-7,8,10,11-tetraazaspiro[5,5]-undec-2-ene-9-
thione (7)
Dimedone 1 (0.01 mol) in ethanol (3 mL) was stirred by adding the solution of thiocar-
bohydrazide (0.01 mol) in hot water (20 mL) dropwise.[42] Stirring was further continued
for 3 h. The completion of the reaction was checked using TLC, and it was kept over-
night. The brown solid thus obtained was filtered and washed with hot water several
times, dried, and crystallized from ethanol to get the desired compound 7.
General procedure for preparation of 3-hydroxy-5,5-dimethyl-spiro[cyclohex-2-
ene-thiazolo/thiazino[3,2-b]-s-tetrazine(8–12)
A mixture of compound 7 (0.001 mol) and chloroacetic acid/ethylchloroacetate/1,2-
dibromoethane/1,3-dibromopropane/phenacyl bromide (0.001 mol) in ethanol (5 mL)
was refluxed for 6–7 h. The product formation was checked using TLC. The reaction
mixture was cooled and poured into cold water. The solid thus separated out was fil-
tered, dried and recrystallized from ethanol to get the desired compounds 8–12.
Acknowledgments
The authors thank FIST-DST for providing infrastructural research facility and SAIF, IIT,
Chennai for recording NMR and Mass spectra.
Funding
The authors thank UGC (DRS-SAP), New Delhi for financial support. One of the authors, P.P.
Mohanta, is thankful to UGC for granting UGC-BSR Fellowship for Ph.D. program.

R
SYNTHETIC COMMUNICATIONSV
9
References
[1] Hejiao, H.; Huijuan, G.; Erwei, L.; Xingzhong, L.; Yuguang, Z.; Yongsheng, C.
Decaspirones F ꢀ I Bioactive Secondary Metabolites from the Saprophytic Fungus
Helicoma viridis. J. Nat. Prod. 2006, 69, 1672–1675. DOI: 10.1021/np0603830.
€
[2] Lindell, S.; Sanft, U.; Thonessen, M. T. Int. Pat 2001, WO/2001/011968 (App. PCT/
EP2000/007851).
[3] Kreuder, W.; Yu, N.; Salbeck, J. Int. Pat 1999, WO/1999/040655 (App. CT/EP1999/
000441).
[4] Lupo, D.; Salbeck, J.; Schenk, H.; Stehlin, T.; Stern, R.; Wolf, A. US Pat 2008, 5840217.
(App. USPTO: 08/417390).
[5] Campoy, A. V.; Todd, M. J.; Freire, E. HIV-1 Protease Inhibitors: Enthalpic versus
Entropic Optimization of the Binding Affinity. Biochemistry 2000, 39, 2201–2207. DOI:
10.1021/bi992399d.
[6] Maloo, P.; Roy, T. K.; Sawant, D. M.; Pardasani, R. T.; Salunkhe, M. M. A Catalyst-Free,
One-Pot Multicomponent Synthesis of Spiro-Benzimidazoquinazolinones via
a
Knoevenagel–Michael-Imine Pathway: A Microwave Assisted Approach. RSC Adv. 2016,
6, 41897–41906. DOI: 10.1039/C6RA05322J.
[7] Yue, D.; Larock, R. C. Synthesis of 2,3-Disubstituted Benzo[b]Thiophenes via Palladium-
Catalyzed Coupling and Electrophilic Cyclization of Terminal Acetylenes. J. Org. Chem.
2002, 67, 1905–1909. DOI: 10.1021/jo011016q.
[8] McDonald, F. E.; Burova, S. A.; Huffman, L. G. Sulfur-Alkyne Cyclizations for Formation
of Dihydrothiophenes and Annulated Thiophenes. Synthesis 2000, 2000, 970–974. DOI:
10.1055/s-2000-6294.
[9] Tolstikova, T. G.; Davydova, V. A.; Shul’ts, E. E.; Vafina, G. F.; Safarova, G. M.; Zarudii,
F. A.; Lazareva, D. N.; Tolstikov, G. A. Khim.-Farm. Zh 1990, 24, 27.
[10] Kita, Y.; Kirihara, M.; Sekihachi, J-i.; Okunaka, R.; Sasho, M.; Mohri, S-i.; Honda, T.;
Akai, S.; Tamura, Y.; Shimooka, K-o. Synthetic Antracyclines: Regiospecific Toal Synthesis
of D-Ring Thiophene Analogues of Daunomycin. Chem. Pharm. Bull. 1990, 38,
1836–1843. DOI: 10.1248/cpb.38.1836.
[11] Ohba, Y.; Murakami, Y.; Sone, T.; Awano, H. Synthesis of New Type Benzo[b]Thiophene
Fused Quinones and Their Tetracyanoquinodimethane Derivatives. J. Heterocycl. Chem
1997, 34, 781–787. DOI: 10.1002/jhet.5570340313.
[12] Deng, X.; Liebeskind, L. S. A Contribution to the Design of Molecular Switches: Novel
Acid-Mediated Ring-Closing-Photochemical Ring-Opening of 2,3-Bis(Heteroaryl)Quinines
(Heteroaryl) Thienyl, Furanyl, Pyrrolyl). J. Am. Chem. Soc. 2001, 123, 7703–7704. DOI:
10.1021/ja0106220.
[13] Bharti, S. K.; Nath, G.; Tilak, R.; Singh, S. K. Synthesis, anti-Bacterial and anti-Fungal
Activities of Some Novel Schiff Bases Containing 2,4-Disubstituted Thiazole Ring. Eur. J.
Med. Chem. 2010, 45, 651–660. DOI: 10.1016/j.ejmech.2009.11.008.
[14] Khalil, A. M.; Berghot, M. A.; Gouda, M. A. Synthesis and Antibacterial Activity of Some
New Thiazole and Thiophene Derivatives. Eur. J. Med. Chem. 2009, 44, 4434–4440. DOI:
10.1016/j.ejmech.2009.06.002.
[15] Jaish, L.; Srivastava, S. K. Synthesis and Antimicrobial Activity of Some New N-Methyl-
Piperazinylthiadiazoles and Their Azetidinones. J. Sci. Ind. Res. 2001, 60, 331–335.
[16] Gouda, M. A.; Berghot, M. A.; El-Ghani, G. E.; Abd Khalil, A. M. Synthesis and
Antimicrobial Activities of Some New Thiazole and Pyrazole Derivatives Based on 4,5,6,7-
Tetrahydrobenzothiophene Moiety. Eur. J. Med. Chem. 2010, 45, 1338–1345. DOI: 10.1016/j.
ejmech.2009.12.020.
[17] Giri, R. S.; Thaker, H. M.; Giordano, T.; Williams, J.; Rogers, D.; Sudersanam, V.; Vasu,
K. K. Design, Synthesis and Characterization of Novel 2-(2,4-Disubstituted-Thiazole-5-yl)-
3-Aryl-3H-Quinazoline-4-One Derivatives as Inhibitors of NF-jB and AP-1 Mediated
Transcription Activation and as Potential anti-Inflammatory Agents. Eur. J. Med. Chem.
2009, 44, 2184–2189. DOI: 10.1016/j.ejmech.2008.10.031.

10
P. P. MOHANTA ET AL.
[18] Shiradkar, M.; Venkata, G.; Kumar, S.; Dasai, V.; Tatikonda, S.; Chakravarthy, A. K.;
Shah, R. Clubbed Triazoles: A Novel Approach to Antitubercular Drugs. Eur. J. Med.
Chem. 2007, 42, 807–816. DOI: 10.1016/j.ejmech.2006.12.001.
[19] Eiichi, A.; Koichiro, N.; Akihiko, S.; Jeffrey-Tri, N.; Koushi, H.; Yoshio, H.; Shingo, N.;
Tooru, K.; Yoshio, H.; Yoshiaki, K. Synthesis and Antiviral Property of
Allophenylnorstatine-Based HIV Protease Inhibitors Incorporating D-Cysteine Derivatives
as P2/P3 Moieties. Bioorg. Med. Chem. Lett. 2007, 17, 4213–4217.
[20] Jain, A. K.; Vaidya, A.; Ravichandran, V.; Kashaw, S. K.; Agrawal, R. K. Recent
Developments and Biological Activities of Thiazolidinone Derivatives: A Review. Bioorg.
Med. Chem. 2012, 20, 3378–3395. DOI: 10.1016/j.bmc.2012.03.069.
[21] Zhou, L.; Wang, P.-Y.; Zhou, J.; Shao, W.-B.; Fang, H.-S.; Wu, Z.-B.; Yang, S.
Antimicrobial Activities of Pyridinium-Tailored Pyrazoles Bearing 1,3,4-Oxadiazole
Scaffolds. J. Saudi Chem. Soc. 2017, 21, 852–860. DOI: 10.1016/j.jscs.2017.04.005.
[22] Girish, R. B.; Nandakumar, K. Vasorelaxant Effect in Rat Aortic Rings through Calcium
Channel Blockage: A Preliminary in Vitro Assessment of a 1,3,4-Oxadiazole Derivative.
Chem.-Biol. Interact. 2009, 181, 377–387. DOI: 10.1016/j.cbi.2009.07.014.
[23] Aboraia, A. S.; Abdel-Rahman, H. M.; Mahfouz, N. M.; EL-Gendy, M. A. Novel 5-(2-
Hydroxyphenyl)-3-Substituted-2,3-Dihydro-1,3,4-Oxadiazole-2-Thione Derivatives: Promising
Anticancer Agents. Bioorg. Med. Chem. 2006, 14, 1236–1246. DOI: 10.1016/j.bmc.2005.09.053.
[24] Ke, S.; Li, Z.; Qian, X. 1,3,4-Oxadiazole-3(2H)-Carboxamide Derivatives as Potential Novel
Class of Monoamine Oxidase (MAO) Inhibitors: Synthesis, Evaluation, and Role of Urea
Moiety. Bioorg. Med. Chem. 2008, 16, 7565–7572. DOI: 10.1016/j.bmc.2008.07.026.
[25] Shingalapur, R. V.; Hosamani, K. M.; Keri, R. S.; Hugar, M. H. Derivatives of
Benzimidazole Pharmacophore: Synthesis, Anticonvulsant, Antidiabetic and DNA
Cleavage Studies. Euro. J. Med. Chem. 2010, 45, 1753–1759. DOI: 10.1016/j.ejmech.2010.
01.007.
[26] Manjunatha, K.; Poojary, B.; Lobo, P. L.; Fernandes, J.; Sucheth, N. Synthesis and
Biological Evaluation of Some 1,3,4-Oxadiazole Derivatives. Euro. J. Med. Chem. 2010, 45,
5225–5233. DOI: 10.1016/j.ejmech.2010.08.039.
ꢀ
[27] Flipo, M.; Desroses, M.; Lecat-Guillet, N.; Dirie, B.; Carette, X.; Leroux, F.; Piveteau, C.;
Demirkaya, F.; Lens, Z.; Rucktooa, P.; et al. Ethionamide Boosters: Synthesis, Biological
Activity, and Structure-Activity Relationships of a Series of 1,2,4-Oxadiazole EthR
Inhibitors. J. Med. Chem. 2011, 54, 2994–3010. DOI: 10.1021/jm200076a.
[28] Spink, E.; Ding, D.; Peng, Z.; Boudreau, M. A.; Leemans, E.; Lastochkin, E.; Song, W.;
Lichtenwalter, K.; O’Daniel, P. I.; Testero, S. A.; et al. Structure-Activity Relationship for
the Oxadiazole Class of Antibiotics. J. Med. Chem. 2015, 58, 1380–1389. DOI: 10.1021/
jm501661f.
[29] Suresh Kumar, G. V.; Rajendraprasad, Y.; Mallikarjuna, B. P.; Chandrashekar, S. M.;
Kistayya, C. Synthesis of Some Novel 2-Substituted-5-[Isopropylthiazole] Clubbed 1,2,4-
Triazole and 1,3,4-Oxadiazoles as Potential Antimicrobial and Antitubercular Agents. Eur.
J. Med. Chem 2010, 45, 2063–2074. DOI: 10.1016/j.ejmech.2010.01.045.
ꢁ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
[30] Karabanovich, G.; Zemanova, J.; Smutny, T.; Szekely, R.; Sarkan, M.; Centarova, I.; Vocat,
ꢁ
ꢀ
ꢀ
ꢁ
ꢁ
A.; Pavkova, I.; Conka, P.; Nemecek, J.; et al. Development of 3,5-Dinitrobenzylsulfanyl-
1,3,4-Oxadiazoles and Thiadiazoles as Selective Antitubercular Agents Active against
Replicating and Nonreplicating Mycobacterium tuberculosis. J. Med. Chem. 2016, 59,
2362–2380. DOI: 10.1021/acs.jmedchem.5b00608.
[31] Werbel, L. M.; Mcnamara, D. J.; Colbry, N. L.; Johnson, J. L.; Degnan, M. J.; Whitney, B.
Synthesis and Antimalarial Effects of N,N-Dialkyl-6-(Substituted Phenyl)-1,2,4,5-Tetrazin-
3-Amines. J. Heterocycl. Chem. 1979, 16, 881–894. DOI: 10.1002/jhet.5570160511.
[32] Kigasawa, K.; Hiiragi, M.; Wagatsuma, N.; Kohagizawa, T.; Inoue, H. JP Patent 1979, 54,
579.
[33] Sauer, J.; Boulton, A. J. Ed. Elsevier: Oxford 1996, 6, 901.

R
SYNTHETIC COMMUNICATIONSV
11
[34] (a) Eremeev, A. V.; Tikhomirov, D. A.; Tyusheva, V. A.; Liepins, F. Khim. Geterotsikl.
Soedin 1978, 753. (b) Eremeev, A. V.; Tikhomirov, D. A.; Zidermane, A. U.S.S.R 1980,
686, 336.
[35] Rao, G. W.; Hu, W. X. Synthesis, Structure Analysis, and Antitumor Activity of 3,6-
Disubstituted-1,4-Dihydro-1,2,4,5-Tetrazine Derivatives. Bioorg. Med. Chem. Lett. 2006,
16, 3702–3705. DOI: 10.1016/j.bmcl.2006.04.066.
[36] Xu, F.; Yang, Z.; Jiang, J.; Pan, W.; Yang, X.; Wu, J.; Zhu, Y.; Wang, J.; Shou, Q.; Wu, H.
Synthesis, Antitumor Evaluation and Molecular Docking Studies of [1,2,4]Triazolo [4,3-
b][1,2,4,5]Tetrazine Derivatives. Bioorg. Med. Chem. Lett. 2016, 26, 3042–3047. DOI: 10.
1016/j.bmcl.2016.05.007.
[37] Clayden, J.; Greeves, N.; Warren, S.; Wothers, P. Organic Chemistry. Oxford University
Press: New York, pp 523.
[38] El Ashry, E. S. H.; Labib, G. H.; Shaban, M.; El Sayed, F. Reaction of Hydrazines with
Dimedone. Ind. J. Chem. B 1978, 16, 871–875.
[39] Majumdar, P.; Mohanta, P. P.; Behera, R. K.; Behera, A. K. Chemistry of Dimedone for
Synthesis of Oxygen-, Nitrogen-, and Sulfur- Containing Heterocycles from 2-(3-Hydroxy-
5,5-Dimethylcyclohex-2-Enylidene)Malononitrile. Synth. Commun. 2013, 43, 899–914.
DOI: 10.1080/00397911.2011.614713.
[40] Longeon, A.; Guyot, M.; Vacelet, J. Araplysillins-I and-II: Biologically Active
Dibromotyrosine Derivatives from the sponge Psammaplysilla arabica. Expermentia 1990,
46, 548. DOI: 10.1007/BF01954262.
[41] Kobayachi, J.; Tsuda, M.; Agemi, K.; Shigemori, H.; Ishibashi, M.; Sasaki, T.; Mikami, Y.
Purealidins B and C, New Bromotyrosine Alkaloids from the Okinawan Marine Sponge
Psammaplysilla purea. Tetrahedron 1991, 47, 6617. DOI: 10.1016/S0040-4020(01)82314-0.
[42] Lamon, R. W. Monohydrazones of Thiocarbohydrazide. Occurrence of 1,4,5,6-Tetrahydro-
3(2H)-s-Tetrazinethione Structures. J. Org. Chem. 1969, 34, 756–758. DOI: 10.1021/
jo01255a068.