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European	Journal	of	Chemistry	6	(4)	(2015)	410‐416	

	

European	Journal	of	Chemistry	
ISSN	2153‐2249	(Print)	/	ISSN	2153‐2257	(Online)		2015	Atlanta	Publishing	House	LLC	‐	All	rights	reserved	‐	Printed	in	the	USA	

http://dx.doi.org/10.5155/eurjchem.6.4.410‐416.1312	

	
	

	

	

European	Journal	of	Chemistry	
Journal	webpage:	www.eurjchem.com	 	

	 	 	

Alum	[KAl(SO4)2·12H2O]	catalyzed	microwave	assisted	synthesis	of		
5‐arylidine‐2‐(methylthio)‐thiazolone	derivatives	in	water	

Santosh	Jadhav	1,	Mahesh	Shioorkar	1,	Omprakash	Chavan	2,	Aniket	Sarkate	3,	
Devanand	Shinde	3	and	Rajendra	Pardeshi	4,*	

1	Department	of	Chemistry,	Vivekanand	College,	Aurangabad,	MS,	431001,	India	
2	Department	of	Chemistry,	Barwale	College,	Jalna,	MS,	431203,	India	
3	Department	of	Chemical	Technology,	Dr.	Babasaheb	Ambedkar	Marathwada	University,	Aurangabad,	MS,	431001,	India	
4	Department	of	Chemistry,	Sant	Ramdas	College,	Ghansawangi,	Jalna,	MS,	431203,	India	

*	Corresponding	author	at:	Department	of	Chemistry,	Sant	Ramdas	College,	Ghansawangi,	Jalna,	MS,	431203,	India.		
Tel.:	+91.240.2403308.	Fax:	+91.240.2400413.	E‐mail	address:	rajendrakpardeshi@gmail.com	(R.	Pardeshi).	

	
	

	 	

	 	 	

ARTICLE	INFORMATION	 	 ABSTRACT	

	
DOI:	10.5155/eurjchem.6.4.410‐416.1312	

Received:	22	August	2015	
Received	in	revised	form:	14	September	2015	
Accepted:	19	September	2015	
Published	online:	31	December	2015	
Printed:	31	December	2015	

	 An	efficient	and	environmentally	benign	method	has	been	developed	 for	 the	synthesis	of	5‐
arylidine‐2‐(methylthio)‐thiazolones	 derivatives	 using	 Alum	 [KAl(SO4)2·12H2O]	 catalyst	 and
triethyl	 amine	 in	water	 under	microwave	 irradiation.	 This	 green	 transformation	 generated
one	 C‐S	 and	 one	 C‐C	 bond,	 condensation	 and	 S‐methylation.	 Notable	 advantages	 for	 the
present	 protocol	 include,	 short	 reaction	 time,	 cleaner	 reaction	 profile	 and	 easy	 isolation	 of
product	by	microwave	irradiation	technique	using	green	catalyst	and	solvent.	

KEYWORDS	
Alum	
Water	
Aldehyde	
Rhodanine	
Triethyl	amine	
Microwave‐assisted	synthesis	

Cite	this: Eur.	J.	Chem.	2015,	6(4),	410‐416

	
1.	Introduction	
	

In	 recent	 years,	 development	 of	 atom	 economical	 and	
environmentally	benign	chemical	technologies	has	become	an	
important	 goal	 in	 the	 synthetic	 chemistry;	 [1‐3]	 in	 impro‐
vation,	 organic	 chemist	 have	 developed	 an	 eco‐friendly	
methods	such	as	use	of	microwave,	ultrasound,	grinding,	ball	
mill	reaction	and	so	on.	The	use	of	microwave	energy	is	one	of	
the	 eco‐friendly	 methods	 to	 accelerate	 the	 organic	 reactions	
which	attract	attention	of	many	researchers	and	have	number	
of	 advantages	 such	 as	 short	 reaction	 time,	 easy	 work‐up	
procedure,	 no	 side	 product	 and	 high	 yield.	 Hence,	 among	
various	 green	methodologies,	 Microwave	 irradiation	method	
mostly	 used	 and	 found	 promising	 in	 organic	 synthesis	 [4‐6].	
Alum	(KAl(SO4)2·12H2O),	which	is	used	for	prominent	organic	
transformations,	 for	 example	 the	 Beginelli	 reaction	 [7]	
synthesis	of	coumarins,	 [8]	and	also	used	for	 the	synthesis	of	
1,8‐dioxo‐octahydroxanthenes	 [9],	 isoquinolonic	 acids	 [10],	
trisubstituted	 dimidazoles	 [11],	 1H‐spiro[isoindoline‐1,2’‐
quinazoline]‐3,4’(3H)‐diones	 [12],	 1,3,4‐oxadiazoles	 [13],	 and	
1,5‐benzodiazepines	 [14].	Use	of	water	as	a	 reaction	medium	

results	 in	 increase	 the	 rate	 and	 selectivity	 of	 many	 organic	
reactions	[15‐19].	In	addition	to	using	of	green	solvent	with	or	
without	combination	of	microwave	irradiation	reactions	were	
performed	 and	 found	 reduced	 reaction	 time	 compared	 to	
conventional	method	[20‐28].	

The	rhodanine	scaffold	is	central	part	of	biologically	active,	
pharmaceutically	 important	 compounds	 with	 various	 appli‐
cation	 and	 uses	 such	 as	 anti‐microbial	 [29‐32],	 anti‐diabetic	
[33,34],	anti‐malarial	[35],	anti‐fungal	[36],	anti‐inflammatory	
[37],	 anti‐tubercular	 [38,39],	 anti‐HIV	 [40,41],	 inhibitors	 of	
chikungunya	 virus	 [42‐44],	 anti‐cancer	 and	 anti‐leukotriene	
therapy	 [45,46].	 Previously	 reported	 synthetic	 methods	 [47‐
56];	 these	 synthetic	 approaches,	 however,	 suffer	 from	
disadvantages	such	as	using	hazardous	solvent	and	or	catalyst,	
low	 yield,	 lack	 of	 selectivity,	 and	 complicated	 workup	 in	
procedures,	 use	 of	 hazardous	 chemical	 compounds	 and	 are	
expensive.	 To	 convey	 these	 difficulties,	 it	 is	 essential	 to	
develop	a	simple	and	eco‐friendly	method	for	the	synthesis	of	
(Z)‐5‐substituted(aryl/hetero‐aryl)‐2‐(methylthio)‐thiazolo‐
nes.		

	



Jadhav	et	al.	/	European	Journal	of	Chemistry	6	(4)	(2015)	410‐416	 411	
 

	

 
Scheme	1	

	
	

	
	

Figure	1.	Plausible	mechanism	for	the	synthesis	of	functionalized	thiazolidinones.
	
	
Present	study	 is	outcome	of	our	continuous	efforts	which	

establish	new	green	combination	of	 triethyl	amine	and	water	
as	 catalyst	 and	 solvent.	 They	 have	 become	 an	 increasingly	
attractive	 synthetic	 tool	 because	 of	 their	 green	 credentials	
such	as	convergence,	atom‐economy,	energy	and	cost	savings,	
with	minimal	waste	 [57].	 Present	 study	 is	 in	 continuation	 of	
our	 research	 interest	 as	 searching	 of	 new	 and	 facile	 green	
synthetic	protocols	[58‐63].	
	
2.	Experimental		
	
2.1.	Instrumentation	
	

Melting	 points	 were	 recorded	 on	 SRS	 Optimelt	 melting	
point	apparatus	and	are	uncorrected.	The	IR	spectra	were	run	
for	KBr	discs	on	a	FT‐IR	Bruker	(νmax	in	cm‐1)	and	1H	NMR	and	
13C	 NMR,	 were	 recorded	 on	 a	 400	 MHz,	 NMR	 instrument	
Bruker	(Avance)	DMSO‐d6	as	solvent.	Mass	spectra	were	taken	
with	 Micromass‐QUATTRO‐II	 mass	 spectrometer.	 Chemical	
shifts	are	given	in	parts	per	million	(δ‐scale)	and	the	coupling	
constants	 are	given	 in	hertz.	 Silica	 gel‐G	plates	 (Merck)	were	
used	for	thin	layer	chromatography	analysis	with	a	mixture	of	
(10%	chloroform:methyl	alcohol)	as	eluent.	Elemental	analysis	
was	 performed	 on	 a	 Perkin	 Elmer	 2400	 Series	 II	 Elemental	
CHNS	analyzer.	Microwave	reactions	have	been	carried	out	in	
a	MicroSYNTH	Lab	station	of	Ethusi	Milestone.	
	
2.2.	Synthesis	
	
2.2.1.	General	method	for	synthesis	of	(Z)‐5‐(benzylidine)‐2‐
thioxothiazolidin‐4‐one	(3)	
	

In	 a	 small	 round	 bottom	 flask,	 rhodanine	 1	 (1	 mmol),	
aldehyde	2	 (1	mmol),	 alum	10	mol%	 in	minimum	amount	of	
water	 were	 added,	 reaction	 mixture	 was	 subjected	 to	
microwave	irradiation	(800	Watt	at	100	°C)	for	8‐10	min.	The	
progress	 of	 reaction	 was	 monitored	 by	 thin	 layer	 chroma‐
tography(ethyl	 acetate:n‐hexane;	3:7,	v:v)	 after	 completion	of	
reaction,	 the	 reaction	 mixture	 poured	 into	 ice‐cold	 water,	

precipitate	was	filtered	and	wash	with	water	dried,	purified	by	
recrystallization	 in	 ethyl	 alcohol	 as	 solvent,	 yield	 89‐98%	
(Scheme	1	and	Figure	1).	

(Z)‐5‐Benzylidene‐2‐thioxothiazolidin‐4‐one	 (3a):	 Color:	
Yellow	 crystal.	 Yield:	 90%.	 M.p.:	 203‐205	 °C.	 FT‐IR	 (KBr,	 ν,	
cm1):	 1236	 (N‐C=S),	 1690	 (N‐C=O),	 1585(N‐H),	 2050	 (Ar‐H),	
1735.	1H	NMR	(400	MHz,	DMSO‐d6,	δ,	ppm):	7.50‐7.64	(m,	5H,	
Ar‐H),	7.65	(s,	1H,	=CH),	13.85	(s,	1H,	N‐H).	13C	NMR	(100	MHz,	
DMSO‐d6,	 δ,	 ppm):	 193.5,	 168.3,	 143.5,	 135.7,	 129.02,	 128.7,	
128.4,	128.2,	127.03,	116.2.	MS	(ESI,	m/z):	222	[M+H]+.	

(Z)‐5‐(4‐Chlorobenzylidene)‐2‐thioxothiazolidin‐4‐one	(3b):	
Color:	Yellow	crystal.	Yield:	91%.	M.p.:	130‐132	°C.	FT‐IR	(KBr,	
ν,	cm1):	1230	(N‐C=S),	1695	(N‐C=O),	1589	(N‐H),	3025	(Ar‐H),	
1120	(C‐F).	1H	NMR	(400	MHz,	DMSO‐d6,	δ,	ppm):	7.38‐7.70	(d,	
4H,	Ar‐H),	7.72	(s,	1H,	=CH),	13.93	(s,	1H,	N‐H).	13C	NMR	(100	
MHz,	 DMSO‐d6,	 δ,	 ppm):	 193.5,	 168.3,	 143.5,	 133.7,	 129.02,	
128.7,	128.4,	128.2,	127.03,	116.5.	MS	(ESI,	m/z):	255	[M+H]+.	

(Z)‐5‐(4‐Fluorobenzylidene)‐2‐thioxothiazolidin‐4‐one	 (3c):	
Color:	Yellow	crystal.	Yield:	90%.	M.p.:	225‐227	°C.	FT‐IR	(KBr,	
ν,	cm1):	1230	(N‐C=S),	1694	(N‐C=O),	1580	(N‐H),	3025	(Ar‐H),	
1125	(C‐F).	1H	NMR	(400	MHz,	DMSO‐d6,	δ,	ppm):	7.65	(d,	4H,	
Ar‐H),	7.72(s,	1H,	=CH),	13.90(s,	1H,	N‐H).	13C	NMR	(100	MHz,	
DMSO‐d6,	 δ,	 ppm):	 193.5,	 168.3,	 163.5,	 143.7,	 116.02,	 130.7,	
130.4,	130.2,	115.03,	115.2.	MS	(ESI,	m/z):	239	[M+H]+.	

(Z)‐5‐(4‐Nitrobenzylidene)‐2‐thioxothiazolidin‐4‐one	 (3d):	
Color:	Yellow	crystal.	Yield:	98%.	M.p.:	254‐256	°C.	FT‐IR	(KBr,	
ν,	 cm1):	 1230	 (N‐C=S),	 1505(‐N=O,	 asymmetric),	 1339	 (N=O,	
symmetric).	1H	NMR	(400	MHz,	DMSO‐d6,	δ,	ppm):	7.76	(s,	1H,	
=CH),	 8.06	 (d,	 4H,	 Ar‐H),	 13.95	 (s,	 1H,	 N‐H).	 13C	 NMR	 (100	
MHz,	 DMSO‐d6,	 δ,	 ppm):	 193.5,	 168.2,	 147.5,	 143.7,	 141.02,	
129.7,	129.4,	123.2,	123.03,	116.5.	MS	(ESI,	m/z):	266	[M+H]+.	

(Z)‐5‐(4‐Hydroxybenzylidene)‐2‐thioxothiazolidin‐4‐	 one	
(3e):	Color:	Yellow	crystal.	Yield:	90%.	M.p.:	264‐266	°C.	FT‐IR	
(KBr,	ν,	cm1):	1175	(N‐C=S),	1712	(N‐C=0),	1605	(N‐H),	3160	
(OH).	 1H	NMR	(400	MHz,	DMSO‐d6,	δ,	ppm):	5.32	(s,	1H,	OH),	
7.63	 (d,	4H,	Ar‐H),	7.70	 (s,	1H,	S=CH),	13.90	 (s,	1H,	N‐H).	 13C	
NMR	(100	MHz,	DMSO‐d6,	δ,	ppm):	193.5,	168.3,	157.5,	143.7,	
130.02,	 130,	 127.4,	 115.8,	 115.03,	 116.2.	MS	 (ESI,	m/z):	 238	
[M+H]+.	



412	 Jadhav	et	al.	/	European	Journal	of	Chemistry	6	(4)	(2015)	410‐416	
	

	

 
	

Scheme	2
	
	
(Z)‐5‐(4‐Methoxybenzylidene)‐2‐thioxothiazolidin‐4‐one	

(3f):	Color:	Yellow	crystal.	Yield:	90%.	M.p.:	246‐248	°C.	FT‐IR	
(KBr,	ν,	cm1):	1189	(N‐C=S),	1715	(N‐C=0),	1605	(N‐H),	1160	
(O‐CH3).	 1H	NMR	 (400	MHz,	DMSO‐d6,	 δ,	 ppm):	 3.82	 (s,	 3H,	 ‐
CH3),	7.63	(d,	4H,	Ar‐H),	7.70	(s,	1H,	S=CH),	13.90	(s,	1H,	N‐H).	
13C	 NMR	 (100	 MHz,	 DMSO‐d6,	 δ,	 ppm):	 193.2,	 168.5,	 143.7,	
169,	130.6,	130,	127.2,	116.2,	114.3,	114,	55.3.	MS	(ESI,	m/z):	
252	[M+H]+.	

(Z)‐5‐(4‐methylbenzylidene)‐2‐thioxothiazolidin‐4‐one	(3g):	
Color:	Yellow	crystal.	Yield:	90%.	M.p.:	220‐222	°C.	FT‐IR	(KBr,	
ν,	cm1):	1190	(N‐C=S),	1685	(N‐C=0),	1580	(N‐H),	3040	(Ar‐H).	
1H	NMR	(400	MHz,	DMSO‐d6,	 δ,	ppm):	2.37	 (s,	3H,	CH3),	7.51	
(d,	 4H,	 Ar‐H),	 7.68	 (s,	 1H,	 =CH),	 13.81	 (s,	 1H,	N‐H).	 13C	NMR	
(100	 MHz,	 DMSO‐d6,	 δ,	 ppm):	 193.5,	 168.3,	 143.5,	 136.7,	
133.02,	128.7,	128.4,	127.8,	127.08,	116.2,	21.3.	MS	(ESI,	m/z):	
236	[M+H]+.	

(Z)‐5‐(3‐Methoxybenzylidene)‐2‐thioxothiazolidin‐4‐	 one	
(3h):	Color:	Yellow	crystal.	Yield:	90%.	M.p.:	226‐229	°C.	FT‐IR	
(KBr,	 ν,	 cm1):	1213(N‐C=S),	 1685	 (N‐C=O),	1585	 (N‐H),	3150	
(Ar‐H),	 1165	 (O‐CH3).	 1H	NMR	 (400	MHz,	DMSO‐d6,	 δ,	 ppm):	
3.82	(s,	3H,	OCH3),	7.08‐7.65	(m,	4H,	Ar‐H	+	1H,	=CH),	13.83	(s,	
1H,	N‐H).	13C	NMR	(100	MHz,	DMSO‐d6,	δ,	ppm):	193.5,	168.1,	
160,	143.2,	135.7,	129.3,	120,	116.2,	55.2.	MS	(ESI,	m/z):	252	
[M+H]+.	

(Z)‐5‐(3‐Methylbenzylidene)‐2‐thioxothiazolidin‐4‐one	 (3i):	
Color:	Yellow	crystal.	Yield:	92%.	M.p.:	217‐219	°C.	FT‐IR	(KBr,	
ν,	cm1):	1190	(N‐C=S),	1685	(N‐C=0),	1580	(N‐H),	3040	(Ar‐H).	
1H	NMR	(400	MHz,	DMSO‐d6,	δ,	ppm):	2.48	(s,	3H,	CH3),	7.36‐
7.62	 (m,	 4H,	 Ar‐H),	 7.68(s,	 1H,	 =CH),	 13.81	 (s,	 1H,	 N‐H).	 13C	
NMR	(100	MHz,	DMSO‐d6,	δ,	ppm):	193.5,	168.5,	143.5,	138.7,	
135.02,	128.8,	128.3,	126.4,	125.2,	116.03,	21.2.	MS	(ESI,	m/z):	
236	[M+H]+.	

(Z)‐5‐(3‐Fluorobenzylidene)‐2‐thioxothiazolidin‐4‐one	 (3j):	
Color:	Yellow	crystal.	Yield:	90%.	M.p.:	199‐201	°C.	FT‐IR	(KBr,	
ν,	cm1):	1232	(N‐C=S),	1695	(N‐C=O),	1589	(N‐H),	3028	(Ar‐H),	
1130	 (C‐F).	 1H	NMR	 (400	MHz,	 DMSO‐d6,	 δ,	 ppm):	 7.38‐7.70	
(m,	4H,	Ar‐H),	7.71	 (s,	1H,	=CH),	13.83	 (s,	1H,	N‐H).	 13C	NMR	
(100	 MHz,	 DMSO‐d6,	 δ,	 ppm):	 193.5,	 168.3,	 162.5,	 143.7,	
136.02,	130.7,	124.4,	116.2,	114.03,	113.2.	MS	(ESI,	m/z):	239	
[M+H]+.	

(Z)‐5‐(2,4‐Dichlorobenzylidene)‐2‐thioxothiazolidin‐4‐	one	
(3k):	Color:	Yellow	crystal.	Yield:	90%.	M.p.:	231‐233	°C.	FT‐IR	
(KBr,	ν,	cm1):	1230	(N‐C=S),	1716	(N‐C=O),	1590	(N‐H),	3265	
(Ar‐H).	1H	NMR	(400	MHz,	DMSO‐d6,	δ,	ppm):	6.63	(s,	1H,	Ar‐
H),	7.68	(d,	2H,	Ar‐H),	7.85	(s,	1H,	=CH),	13.95	(s,	1H,	NH).	13C	
NMR	(100	MHz,	DMSO‐d6,	δ,	ppm):	193.5,	168.3,	143.5,	135.7,	
131.02,	130.7,	128.4,	126.2,	125.03,	115.3.	MS	(ESI,	m/z):	289	
[M+H]+.	

(Z)‐5‐(2,4‐Dimethoxybenzylidene)‐2‐thioxothiazolidin‐4‐one	
(3l):	Color:	Yellow	crystal.	Yield:	95%.	M.p.:	270‐272	°C.	FT‐IR	
(KBr,	 ν,	 cm1):	 1235	 (N‐C=S),	 1720	 (N‐C=O),	 1590	 (N‐H),	
3265(Ar‐H),	 1168	 (O‐CH3).	 1H	 NMR	 (400	 MHz,	 DMSO‐d6,	 δ,	
ppm):	3.86	(s,	6H,	OCH3),	6.64	(s,	1H,	Ar‐H),	7.64	(d,	2H,	Ar‐H),	
7.80	(s,	1H,	=CH),	13.95	(s,	1H,	NH).	13C	NMR	(100	MHz,	DMSO‐
d6,	 δ,	 ppm):	 193.5,	 168.3,	 143.5,	 135.7,	 129.02,	 128.7,	 126.4,	
106.2,	107.03,	98.2,	55.02,	56.01.	MS	(ESI,	m/z):	282	[M+H]+.	

(Z)‐5‐(2‐Chlorobenzylidene)‐2‐thioxothiazolidin‐4‐	 one	
(3m):	Color:	Yellow	crystal.	Yield:	92%.	M.p.:	179‐181	°C.	FT‐

IR	(KBr,	ν,	cm1):	1233(N‐C=S),	1695	(N‐C=O),	1590	(N‐H),	850	
(C‐Cl),	 3072	 (Ar‐H).	 1H	 NMR	 (400	 MHz,	 DMSO‐d6,	 δ,	 ppm):	
7.52‐7.75	(m,	4H,	Ar‐H	+	1H,	=CH),	13.96	(s,	1H,	N‐H).	13C	NMR	
(100	 MHz,	 DMSO‐d6,	 δ,	 ppm):	 193.5,	 168.3,	 143.5,	 134.7,	
133.02,	127.7,	126.4,	126.2,	127.03,	116.2.	MS	(ESI,	m/z):	255	
[M+H]+.	

(Z)‐5‐(Thiophen‐2‐ylmethylene)‐2‐thioxothiazolidin‐4‐	one	
(3n):	Color:	Yellow	grey	crystals.	Yield:	90%.	M.p.:	230‐233	°C.	
FT‐IR	(KBr,	ν,	cm1):	1235(N‐C=S),	1690	(N‐C=O),	1590	(N‐H),	
3072	(Ar‐H),	668	(C‐S).	1H	NMR	(400	MHz,	DMSO‐d6,	δ,	ppm):	
7.51	 (s,	 1H,	 =CH),	 7.60‐8.10	 (m,	 3H,	 thiophenyl),	 8.07	 (s,	 1H,	
NH).	 13C	 NMR	 (100	 MHz,	 DMSO‐d6,	 δ,	 ppm):	 193.5,	 168.3,	
143.5,	 137.5,	 129.08,	 129,	 128.2,	 122.2.	 MS	 (ESI,	m/z):	 227	
[M+H]+.	

(Z)‐5‐(Furan‐2‐ylmethylene)‐2‐thioxothiazolidin‐4‐	 one	
(3o):	 Color:	 Brownish	 yellow	 crystals.	 Yield:	 89%.	M.p.:	 223‐
225	°C.	FT‐IR	(KBr,	ν,	cm1):	1235(N‐C=S),	1690	(N‐C=O),	1594	
(N‐H),	3070	(Ar‐H),	660	(C‐O).	1H	NMR	(400	MHz,	DMSO‐d6,	δ,	
ppm):	7.53	(s,	1H,	=CH),	7.62‐8.10	(m,	3H,	thiophenyl),	8.12	(s,	
1H,	NH).	 13C	NMR	(100	MHz,	DMSO‐d6,	δ,	ppm):	193.5,	168.3,	
143.5,	 135.7,	 129.02,	 128.7,	 128.4,	 128.2,	 127.03,	 116.2.	 MS	
(ESI,	m/z):	211	[M+H]+.	
	
2.2.2.	General	method	for	synthesis	of	(Z)‐5‐(argio	
methylene)‐2‐(methylthio)	thiazol‐4(5H)‐one	(5)	
	
2.2.2.1.	Microwave	irradiation	method	
	

To	 a	 suspension	 of	 5‐arylidine	 rhodanine	 3	 (1	 mmol),	
methyl	 iodide	4	(1.2	mmol)	and	 triethyl	amine	(1.2	mmol)	 in	
water	 (2‐3	mL)	 shake	 well	 and	 then	 placed	 in	 MicroSYNTH,	
mixture	 was	 subjected	 to	 microwave	 irradiation	 (800	W)	 at	
40‐50	 °C	 for	 3‐4	 min,	 reaction	 mixture	 were	 cool	 at	 room	
temperature.	The	progress	of	reaction	was	monitored	by	thin	
layer	chromatography	(10%	chloroform:methyl	alcohol).	After	
completion	 of	 reaction	 solid	 was	 filtered,	 the	 residue	 was	
washed	with	water	to	afford	crude	product	was	recrystallized	
by	ethanol	to	give	yield	83‐96%	(Scheme	2	and	Figure	1).	
	
2.2.2.2.	Conventional	stirring	method	
	

In	 a	 small	 round	 bottom	 flask	 5‐arylidine	 rhodanine3	 (1	
mmol),	 methyl	 iodide	 4	 (1.2	 mmol)	 and	 triethyl	 amine	 (1.2	
mmol)	 in	 water	 (2‐3	 mL),	 the	 mixture	 was	 stirred	 at	 room	
temperature	 for	 60‐90	 min.	 The	 progress	 of	 reaction	 was	
monitored	 by	 thin	 layer	 chromatography	 (10%	 chloroform‐
methyl	 alcohol).	 After	 completion	 of	 reaction,	 solid	 was	
filtered,	 the	 residue	 was	 washed	 with	 water	 to	 afford	 crude	
product	was	 recrystallized	by	ethanol	 to	give	yield	 range	70‐
80%.	All	the	product	are	well	characterized	by	the	comparison	
of	 their	 spectral	 data	 (IR,	 1H	 NMR,	 13C	 NMR	 and	 physical	
properties	with	those	reported	in	literature)	[56].	

(Z)‐5‐Benzylidene‐2‐(methylthio)thiazol‐4(5H)‐one	 (5a):	
Color:	 Yellow	 solid.	 Yield:	 90%.	 M.p.:	 146‐147	 °C	 (Lit:	 [56]).	
FT‐IR	(KBr,	ν,	cm1):	3027	(CH‐Ar)	(aryl),	1696	(C=O)	(Amide),	
1606(C=N),	 1590	 (C=C),	 1160(C‐S),	 985	 (C‐N).	 1H	NMR	 (400	
MHz,	 DMSO‐d6,	 δ,	 ppm):	 2.83(s,3H,	 S‐CH3),	 7.44‐7.76	 (m,	 5H,	
Ar‐CH),	 7.96	 (s,	 1H,	 =CH).	 13C	 NMR	 (100	 MHz,	 DMSO‐d6,	 δ,	



Jadhav	et	al.	/	European	Journal	of	Chemistry	6	(4)	(2015)	410‐416	 413	
 

ppm):	 162.2	 (C2),	 166.9	 (C4),	 132.0	 (C5),	 151.8	 (C6),	 125.6‐
136.3	(C7‐C12),	14.6	(C14).	MS	(ESI,	m/z):	236	[M+H]+.	

(Z)‐5‐(4‐Chlorobenzylidene)‐2‐(methylthio)thiazol‐4	 (5H)‐
one	 (5b):	 Color:	 Yellow	 solid.	 	 Yield:	 91%.	 M.p.:	 161‐163	 °C	
(Lit:	 [56]).	 FT‐IR	 (KBr,	 ν,	 cm1):	 3020	 (CH‐Ar),	 1716	 (C=O),	
1583	(C=C),	1465	(C=N),	1155	(C‐S),	979	(C‐N).	1H	NMR	(400	
MHz,	DMSO‐d6,	δ,	ppm):	2.82	(s,	3H,	S‐CH3),	7.41‐7.73	(m,	4H,	
Ar‐CH),	 7.98	 (s,	 1H,	 =CH).	 13C	 NMR	 (100	 MHz,	 DMSO‐d6,	 δ,	
ppm):	 162.2	 (C2),	 166.9	 (C4),	 132.3	 (C5),	 151.6	 (C6),	 137.9	
(C7),	 128.5	 (C8),	 128	 (C9),	 134.1	 (C10),	 128	 (C11),	 128.9	
(C12),	14.6	(C14).	MS	(ESI,	m/z):	271[M+H]+.	

(Z)‐5‐(4‐Fluorobenzylidene)‐2‐(methylthio)thiazol‐4	 (5H)‐
one	(5c):	Color:	Yellow	solid.	Yield:	90%.	M.p.:	142‐144	°C	(Lit:	
[56]).	 FT‐IR	 (KBr,	 ν,	 cm1):	 3012	 (CH‐Ar),	 1710	 (C=O),	 1597	
(C=C),	1490	(C=N),	1156	(C‐S),	975	(C‐N).	1H	NMR	(400	MHz,	
DMSO‐d6,	 δ,	 ppm):	 2.83	 (s,	 3H,	 S‐CH3),	 7.44‐7.76	 (m,	 4H,	 Ar‐
CH),	7.95	(s,	1H,	=CH).	13C	NMR	(100	MHz,	DMSO‐d6,	δ,	ppm):	
162.2	(C2),	166.9	(C4),	132.4	(C5),	151.5	(C6),	130.1	(C7),	130	
(C8),	 115	 (C9),	 161.8	 (C10),	 152	 (C11),	 130.2	 (C12),	 14.6	
(C14).	MS	(ESI,	m/z):	254	[M+H]+.	

(Z)‐2‐(Methylthio)‐5‐(4‐nitrobenzylidene)thiazol‐4	(5H)‐one	
(5d):	 Color:	 Orange	 solid.	 Yield:	 96%.	 M.p.:	 163‐165	 °C	 (Lit:	
[56]).	 FT‐IR	 (KBr,	 ν,	 cm1):	 3016	 (CH‐Ar),	 1695	 (C=O),	 1590	
(C=C),	1590	 (C=N),	1156(C‐S),	971	 (C‐N).	 1H	NMR	(400	MHz,	
DMSO‐d6,	δ,	ppm):	2.81	(s,	3H,	S‐CH3),	2.95(s,	1H,	=CH),	7.96‐
8.20	 (m,	 4H,	 Ar‐CH).	 13C	 NMR	 (100	MHz,	 DMSO‐d6,	 δ,	 ppm):	
162.3	(C2),	166.9	(C4),	132.4	(C5),	151.7	(C6),	140.8	(C7),	129	
(C8),	123	(C9),	146.8	(C10),	123	(C11),	130	(C12),	14.5	(C14).	
MS	(ESI,	m/z):	281	[M+H]+.	

(Z)‐5‐(4‐Hydroxybenzylidene)‐2‐(methylthio)thiazol‐4(5H)‐
one	(5e):	Color:	Yellow	solid.	Yield:	88%.	M.p.:	123‐125	°C	(Lit:	
[56]).	 FT‐IR	 (KBr,	 ν,	 cm1):	 3416	 (OH),	 3005	 (CH‐Ar),	
1690(C=O),	1595	(C=C),	1608	(C=N),	1165	(C‐S),	998	(C‐N).	1H	
NMR	(400	MHz,	DMSO‐d6,	δ,	ppm):	2.78	(s,	3H,	S‐CH3),	5.47	(s,	
1H,	OH),	7.43‐7.75	(m,	4H,	Ar‐CH),	7.99	(s,	1H,	=CH).	13C	NMR	
(100	 MHz,	 DMSO‐d6,	 δ,	 ppm):	 162.3	 (C2),	 166.8	 (C4),	 132.5	
(C5),	151.9	(C6),	127.8	(C7),	130	(C8),	115	(C9),	156.8	(C10),	
115	 (C11),	 130	 (C12),	 14.3	 (C14).	 MS	 (ESI,	 m/z):	 252.00	
[M+H]+.	

(Z)‐5‐(4‐Methoxybenzylidene)‐2‐(methylthio)thiazol‐4(5H)‐
one	(5f):	Color:	Yellow	solid.	Yield:	90%.	M.p.:	162‐164	°C	(Lit:	
[56]).	 FT‐IR	 (KBr,	 ν,	 cm1):	 3008	 (CH‐Ar),	 1705	 (C=O),	 1578	
(C=C),	1458	(C=N),	1160	(C‐S),	973	(C‐N).	1H	NMR	(400	MHz,	
DMSO‐d6,	δ,	ppm):	2.82	(s,	3H,	S‐CH3),	2.86	(s,	3H,	O‐CH3),	7.43‐
7.76	 (m,	 4H,	 Ar‐CH),	 7.96	 (s,	 1H,	 =CH).	 13C	 NMR	 (100	 MHz,	
DMSO‐d6,	 δ,	 ppm):	 162.3	 (C2),	 166.6	 (C4),	 132.3	 (C5),	 152.2	
(C6),	 127.2	 (C7),	 130	 (C8),	 114.3	 (C9),	 159.3	 (C10),	 114.7	
(C11),	 130	 (C12),	 14.2	 (C14),	 54.7	 (C15).	MS	 (ESI,	m/z):	 266	
[M+H]+.	

(Z)‐5‐(4‐Methylbenzylidene)‐2‐(methylthio)thiazol‐4	(5H)‐
one	(5g):	Color:	Yellow	solid.	Yield:	89%.	M.p.:	173‐175	°C	(Lit:	
[56]).	 FT‐IR	 (KBr,	 ν,	 cm1):	 3025	 (CH‐Ar),	 1705	 (C=O),	 1595	
(C=C),	1475	(C=N),	1162	(C‐S),	978	(C‐N).	1H	NMR	(400	MHz,	
DMSO‐d6,	δ,	ppm):	2.79	(s,	3H,	CH3),	2.89	(s,	3H,	S‐CH3),	7.51‐
7.79	 (m,	 4H,	 Ar‐CH),	 7.91	 (s,	 1H,	 =CH).	 13C	 NMR	 (100	 MHz,	
DMSO‐d6,	 δ,	 ppm):	 162.2	 (C2),	 166.9	 (C4),	 132.2	 (C5),	 152.7	
(C6),	 132	 (C7),	 127.8	 (C8),	 128.7	 (C9),	 137.3	 (C10),	 128.7	
(C11),	 127.8	 (C12),	 14	 (C14),	 20.9	 (C15).	MS	 (ESI,	m/z):	 250	
[M+H]+.	

(Z)‐5‐(3‐Methoxybenzylidene)‐2‐(methylthio)thiazol‐4(5H)‐
one	(5h):	Color:	Yellow	solid.	Yield:	90%.	M.p.:	164‐166	°C	(Lit:	
[56]).	 FT‐IR	 (KBr,	 ν,	 cm1):	 3010	 (CH‐Ar),	 1710	 (C=O),	 1570	
(C=C),	1458	(C=N),	1158	(C‐S),	975	(C‐N).	1H	NMR	(400	MHz,	
DMSO‐d6,	δ,	ppm):	2.81	(s,	3H,	S‐CH3),	7.71	(s,	3H,	O‐CH3),	7.44‐
7.76	 (m,	 4H,	 Ar‐CH),	 7.98	 (s,	 1H,	 =CH).	 13C	 NMR	 (100	 MHz,	
DMSO‐d6,	 δ,	 ppm):	 162.6	 (C2),	 166.9	 (C4),	 132.5	 (C5),	 152.7	
(C6),	 135	 (C7),	 113	 (C8),	 160	 (C9),	 113	 (C10),	 128.7	 (C11),	
120.2	 (C12),	 13.8	 (C14),	 55.2	 (C15).	 MS	 (ESI,	 m/z):	 266	
[M+H]+.	

(Z)‐5‐(3‐Methylbenzylidene)‐2‐(methylthio)thiazol‐4	(5H)‐
one	(5i):	Color:	Yellow	solid.	Yield:	89%.	M.p.:	176‐178	°C	(Lit:	

[56]).	 FT‐IR	 (KBr,	 ν,	 cm1):	 3010	 (CH‐Ar),	 1705	 (C=O),	 1568	
(C=C),	1462(C=N),	1156	 (C‐S),	975	 (C‐N).	 1H	NMR	(400	MHz,	
DMSO‐d6,	 δ,	 ppm):	 2.83	 (s,	 3H,	 S‐CH3),	 2.41	 (s,	 3H,	 Ar‐CH3),	
7.10‐7.40	(m,	3H,	Ar‐CH),	7.16	(s,	1H,	Ar‐CH),	7.98	(s,	1H,	=CH).	
13C	NMR	(100	MHz,	DMSO‐d6,	δ,	ppm):	162.6	(C2),	166.9	(C4),	
132.5	 (C5),	152.7	 (C6),	135	 (C7),	125.3	 (C8),	138	 (C9),	128.2	
(C10),	 127.9	 (C11),	 124.8	 (C12),	 13.8	 (C14),	 21.6	 (C15).	 MS	
(ESI,	m/z):	250	[M+H]+.	

(Z)‐5‐(3‐Fluorobenzylidene)‐2‐(methylthio)thiazol‐4	 (5H)‐
one	(5j):	Color:	Yellow	solid.	Yield:	90%.	M.p.:	144‐146	°C	(Lit:	
[56]).	 FT‐IR	 (KBr,	 ν,	 cm1):	 3012	 (CH‐Ar),	 1705	 (C=O),	 1595	
(C=C),	1468	(C=N),	1160	(C‐S),	976	(C‐N).	1H	NMR	(400	MHz,	
DMSO‐d6,	 δ,	 ppm):	 2.80	 (s,	 3H,	 S‐CH3),	 7.51‐7.77	 (m,	 3H,	 Ar‐
CH),	8.05	(s,	1H,	Ar‐CH),	7.96	(s,	1H,	=CH).	13C	NMR	(100	MHz,	
DMSO‐d6,	δ,	ppm):	162.3	(C2),	166.2	(C4),	132.1	(C5),	152	(C6),	
135.6	 (C7),	 113.3	 (C8),	 162	 (C9),	 114.2	 (C10),	 129.9	 (C11),	
124.2	(C12),	13.9	(C14).	MS	(ESI,	m/z):	254	[M+H]+.	

(Z)‐5‐(2,4‐Dichlorobenzylidene)‐2‐(methylthio)thiazol‐4	
(5H)‐one	 (5k):	Color:	 Yellow	solid.	 Yield:	 90%.	M.p.:	 164‐166	
°C	 (Lit:	 [56]).	 FT‐IR	 (KBr,	 ν,	 cm1):	 3020	 (CH‐Ar),	 1690(C=O),	
1585(C=C),	1490	 (C=N),	1168	 (C‐S),	965	 (C‐N).	 1H	NMR	(400	
MHz,	DMSO‐d6,	δ,	ppm):	2.83	(s,	3H,	S‐CH3),	7.72	(s,	2H,	Ar‐CH),	
8.01	(s,	1H,	=CH),	7.46	(s,	1H,	=CH).	13C	NMR	(100	MHz,	DMSO‐
d6,	δ,	ppm):	162.3	(C2),	166.7	(C4),	132.4	(C5),	152	(C6),	131.9	
(C7),	137.3	(C8),	128	(C9),	124.2	(C10),	126	(C11),	130	(C12),	
13.9	(C14).	MS	(ESI,	m/z):	305	[M+H]+.		

(Z)‐5‐(2,	 4‐Dimethoxybenzylidene)‐2‐(methylthio)thiazol‐
4(5H)‐one	(5l):	Color:	Yellow	solid.	Yield:	91%.	M.p.:	173‐175	
°C	 (Lit:	 [56]).	 FT‐IR	 (KBr,	 ν,	 cm1):	 3011	 (CH‐Ar),	 1690(C=O),	
1570	(C=C),	1475	(C=N),	1160	(C‐S),	960	(C‐N).	1H	NMR	(400	
MHz,	DMSO‐d6,	δ,	ppm):	2.81	(s,	3H,	S‐CH3),	3.86	(s,	6H,	O‐CH3),	
6.60	(s,	1H,	Ar‐CH),	8.05	(s,	2H,	Ar‐CH),	8.20	(s,	1H,	=CH).	13C	
NMR	 (100	 MHz,	 DMSO‐d6,	 δ,	 ppm):	 162.7	 (C2),	 166.8	 (C4),	
132.4	(C5),	152	(C6),	107.9	(C7),	142.7	(C8),	97.8	(C9),	160.2	
(C10),	 105.9	 (C11),	 130	 (C12),	 14	 (C14).	MS	 (ESI,	m/z):	 296	
[M+H]+.	

(Z)‐5‐(2‐Chlorobenzylidene)‐2‐(methylthio)thiazol‐4	 (5H)‐
one	 (5m):	 Color:	 Yellow	 solid.	 Yield:	 90%.	 M.p.:	 171‐173	 °C	
(Lit:	 [56]).	 FT‐IR	 (KBr,	 ν,	 cm1):	 3015	 (CH‐Ar),	 1716	 (C=O),	
1580	(C=C),	1465	(C=N),	1156	(C‐S),	976	(C‐N).	1H	NMR	(400	
MHz,	DMSO‐d6,	δ,	ppm):	2.81	(s,	3H,	S‐CH3),	7.25‐7.45	(m,	4H,	
Ar‐CH),	 7.99	 (s,	 1H,	 C	 =CH).	 13C	NMR	 (100	MHz,	DMSO‐d6,	 δ,	
ppm):	162.3	(C2),	166.4	(C4),	132.2	(C5),	152	(C6),	132.9	(C7),	
134	(C8),	128.3	(C9),	129.2	(C10),	125.9	(C11),	127	(C12),	14	
(C14).	MS	(ESI,	m/z):	271	[M+H]+.	

(Z)‐2‐(Methylthio)‐5‐(thiophen‐2‐ylmethylene)thiazol‐	 4	
(5H)‐one	 (5n):	Color:	 Yellow	solid.	Yield:	88%.	M.p.:	 151‐153	
°C	 (Lit:	 [56]).	FT‐IR	 (KBr,	ν,	 cm1):	3018	(CH‐Ar),	1695	(C=O),	
1580	(C=C),	1490	(C=N),	1162	(C‐S),	972	(C‐N).	1H	NMR	(400	
MHz,	DMSO‐d6,	δ,	ppm):	2.80	(s,	3H,	S‐CH3),	6.90‐8.14	(m,	3H,	
Ar‐CH),	 7.90	 (s,	 1H,	 =CH).	 13C	 NMR	 (100	 MHz,	 DMSO‐d6,	 δ,	
ppm):	 161.3	 (C2),	 166.3	 (C4),	 137.4	 (C5),	 151.8	 (C6),	 136.8	
(C7),	 130	 (C9),	 27.8	 (C10),	 128.9	 (C11),	 14	 (C13).	 MS	 (ESI,	
m/z):	242	[M+H]+.	

(Z)‐5‐(Furan‐2‐ylmethylene)‐2‐(methylthio)thiazol‐4	 (5H)‐
one	(5o):	Color:	Yellow	solid.	Yield:	83%.	M.p.:	161‐164	°C	(Lit:	
[56]).	 FT‐IR	 (KBr,	 ν,	 cm1):	 3016	 (CH‐Ar),	 1695	 (C=O),	
1586(C=C),	1490	 (C=N),	1168	 (C‐S),	972	 (C‐N).	 1H	NMR	(400	
MHz,	DMSO‐d6,	δ,	ppm):	2.81	(s,	3H,	S‐CH3),	6.86‐8.17	(m,	3H,	
Ar‐CH),	 7.93	 (s,	 1H,	 =CH).	 13C	 NMR	 (100	 MHz,	 DMSO‐d6,	 δ,	
ppm):	 161.3	 (C2),	 166.3	 (C4),	 137.5	 (C5),	 151.8	 (C6),	 150.8	
(C7),	 110	 (C9),	 112	 (C10),	 142.9	 (C11),	 13.9	 (C13).	MS	 (ESI,	
m/z):	226	[M+H]+.	
	
3.	Results	and	discussion		
	

The	 series	 of	 reactions	 were	 performed	 to	 optimizing	
reaction	 condition	 in	 various	 acid,	 base	 catalysts	 with	
combination	 of	 different	 solvents	 at	 40	 and	 100	 °C	
programmed	(800	Watt).	

	



414	 Jadhav	et	al.	/	European	Journal	of	Chemistry	6	(4)	(2015)	410‐416	
	

	
Table	1.	Optimization	reaction	condition	for	the	synthesis	of	compound	3	by	microwave	irradiation	*.	
Entry	 Base	/	Acid	 Solvent	 Time	(min)	 Yield	(%)	
1	 Sodium	acetate	 Neat 12 00
2	 Sodium	acetate	 Water 10 52
3	 Sodium	acetate	 Ethanol	 10	 48	
4	 Sodium	acetate	 Acetic	acid	 10	 93	
5	 Et3N	 Water	 10	 35	
6	 Et3N	 EtOH	 10	 30	
7	 Et3N	 Acetonitrile 10 46
8	 Et3N	 PEG 10 48
9	 MontmorriloniteK10	 Water 10 86
10	 MontmorriloniteK10	 Ethanol 10 63
11	 	 MontmorriloniteK10	 Acetonitrile 10 56
12	 MontmorriloniteK10	 PEG 10 72
13	 Alum	 Water 8 98
14	 Alum	 Ethanol	 10	 68	
15	 Alum	 Acetonitrile	 10	 60	
16	 Alum	 PEG 10 76
*	Reaction	condition:	(Microwave	assisted)	rhodanine	(1	mmol),	aldehyde	(1	mmol)	and	alum	(10	mol%)	in	water	at	100	°C,	800	Watt.	
	
	
Table	2.	Microwave	assisted	synthesis	of	compound	3.	

Entry	 Compound	 Ar Time	(min) M.p.	(°C) Yield	(%)	*
1	 3a	 Benzyl	 2	 203‐205	 90	
2	 3b	 4‐Chlorobenzyl 3 130‐132 91	
3	 3c	 4‐Flurobenzyl 3 225‐227 90	
4	 3d	 4‐Nitrobenzyl 2 254‐256 98	
5	 3e	 4‐Hydroxybenzyl 4 264‐266 90	
6	 3f	 4‐Methoxybenzyl 3 246‐248 90	
7	 3g	 4‐Methylbenzyl 3 220‐222 90	
8	 3h	 3‐Methoxybenzyl 3 226‐229 90	
9	 3i	 3‐Methylbenzyl	 3	 217‐219	 92	
10	 3j	 3‐Flurobenzyl	 3	 199‐201	 90	
11	 3k	 2,4‐Dichlorobenzyl	 3	 231‐233	 90	
12	 3l	 2,4dimethoxybenzyl 3 270‐272 95	
13	 3m	 2‐Chlorobenzyl 3 179‐181 92	
14	 3n	 2‐Thiophenyl 3 230‐233 90	
15	 3o	 2‐Furyl 3 223‐225 89	
*	Isolated	yield	after	purification	by	MeOH‐CHCl3.	
	
	
Table	3.	Optimization	reaction	condition	for	the	synthesis	of	compound	5	a.	
Entry	 Base	 Solvent	 Time	(min)	 Yield	(%)	b	
1	 K2CO3	 Neat 5 00
2	 K2CO3	 Water 4 60
3	 Na2CO3	 Neat 5 00
4	 Na2CO3	 Water	 4	 40	
5	 NMP	 Neat 5 00
6	 NMP	 Water	 4	 65	
7	 Et3N	 Neat	 5	 00	
8	 Et3N	 Water	 2	 96	
9	 Et3N	 EtOH 2 40
10	 Et3N	 EtOH:Water	(1:1) 3 58
11	 Et3N	 MeOH 3 30
12	 Et3N	 CH3CN 2 73
13	 Et3N	 CH2Cl2 2 78
14	 Et3N	 DMF 2 56
a	Reaction	condition:	5‐arylidine	rhodanine	(1	mmol),	methyl	iodide	(1.2	mmol)	and	triethyl	amine	(1.2	mmol)	in	water	(2‐3	mL)	at	40	°C.	
b	Isolated	yield	after	purification	by	recrystallization	from	ethanol.	TLC	(10%	chloroform:	methanol).	
	
	
	

In	first	model	reaction	of	chalcone	formation	of	rhodanine	
(1	mmol)	and	aryl	aldehyde	 (1	mmol)	 in	presence	of	various	
mole%	 of	 alum	 (5/10/15	 mol	 %)	 and	 minimum	 amount	 of	
different	 solvent	 (Table	 1),	 in	 finding	Alum	 (10	mol	%)	with	
water	 or	 in	 acetic	 acid‐sodium	 acetate	 (buffer	 solution)	 gave	
better	yield	(Table	1,	entry	13,	4)	among	these	alum	water	was	
proven	good	catalyst	solvent	combination	(Table	1,	entry	13).	
Thus,	 all	 example	 were	 tested	 in	 alum‐water	 and	 excellent	
yield	was	obtained	(89‐98%)	in	short	reaction	time	(Table	2).	

In	 second	model	 reaction	of	 S‐methylation	of	benzylidine	
rhodanine	 (1	mmol),	 Iodomethane	(1.2	mmol)	 in	presence	of	
triethyl	amine	(1.2	mmol)	and	water	 (2‐3	mL)	gave	excellent	
yield	in	very	less	time	of	reaction	at	40	°C	temperature,	among	

the	compared	catalyst	solvent	combination	(Table	3,	entry	8)	
this	is	due	to	triethyl	amine	water	is	best	paired	emerged	base	
catalyst‐solvent.	 Thus,	we	 decided	 all	 reaction	 carried	 out	 in	
triethyl	amine‐water.	All	example	were	tested	reasonably	good	
to	 excellent	 yields	 (83‐96%)	 could	 be	 achieved	 in	 short	
reaction	time	2‐4	min	(Table	4).	Without	solvent,	reaction	did	
not	detect	as	fruitful	one	(Table	3,	entry	7).	An	electronic	effect	
was	observed,	electron	withdrawing	groups	(Table	4,	entry	2‐
4,	 10,	 11,	 13)	 and	 unsubstituted	 aldehyde	 (Table	 4,	 entry	 1)	
were	 well	 tolerate.	 Five	 and	 six	 member	 heterocyclic	 aryl	
aldehyde	gave	corresponding	yield	(Table	4,	entry	14,	15).	

	
	



Jadhav	et	al.	/	European	Journal	of	Chemistry	6	(4)	(2015)	410‐416	 415	
 

	
Table	4.	Microwave	assisted	synthesis	of	compound	5.	

HN

S
S

O

H3C-I
Et3N, water N

SS Ar

O

3 4 5a-o

MWI 800 W, 40 oC
+

Ar

	
Entry	 Compound	 Ar	 Time	(min)	 M.p.	(°C)	 Yield	(%)	
1	 5a	 Benzyl	 2 146‐148 90	
2	 5b	 4‐Chlorobenzyl 3 161‐163	 91	
3	 5c	 4‐Flurobenzyl	 3 142‐145 90	
4	 5d	 4‐Notrobenzyl	 2 163‐165 96	
5	 5e	 4‐Hydroxybenzyl 4 123‐125	 88	
6	 5f	 4‐Methoxybenzyl	 3	 162‐164	 90	
7	 5g	 4‐Methylbenzyl	 3	 173‐175		 89	
8	 5h	 3‐Methoxybenzyl	 3	 164‐166	 90	
9	 5i	 3‐Methylbenzyl 3 176‐178	 89	
10	 5j	 3‐Flurobenzyl	 3 144‐146 90	
11	 5k	 2,4‐Dichlorobenzyl 3 164‐167 90	
12	 5l	 2,4‐Dimethoxybenzyl 3 173‐175 91	
13	 5m	 2‐Chlorobenzyl 3 171‐173 90	
14	 5n	 2‐Thiophenyl	 3 151‐153	 88	
15	 5o	 2‐Furyl	 3 161‐164 83	
	
	

Finally,	 the	 structure	 of	 compounds	 were	 substantiated	
by1H	NMR	spectra,	only	one	signal	for	the	methyne	proton	in	
the	 range	 δ	 7.81‐7.96	 ppm,	 at	 lower	 field	 values	 than	 those	
expected	 for	 the	 E‐isomers.	 This	 strongly	 indicates	 that	 the	
compounds	 have	 the	 Z‐configuration.	 IR	 spectrum	 showed	 a	
strong	 absorption	band	 at	 1690‐1698	 cm‐1	 due	 to	 a	 carbonyl	
group	of	amide.	
	 	
4.	Conclusion	
	

In	 conclusion,	 we	 have	 successfully	 developed	 an	 eco‐
friendly	synthesis	route	of	5‐substituted	(aryl/hetero‐aryl)‐2‐
(methylthio)‐thiazolones	 using	 easily	 available,	 alum	 as	
catalyst	and	water	as	green	solvent	 in	good	 to	excellent	yield	
of	 	 the	products.	Notable	advantages	for	 the	present	protocol	
include	short	 reaction	 time,	 cleaner	 reaction	profile	and	easy	
isolation	of	product	by	microwave	irradiation	technique	using	
green	 catalyst	 and	 solvent.	 An	 effort	 toward	 the	 synthesis	 of	
other	 important	 drug	molecules	with	 a	 rhodanine	moiety	 by	
microwave	 irradiation,	 ultrasonication	 method	 is	 ongoing	 in	
our	laboratory.	
	
Acknowledgements	
	

The	 authors	 are	 thankful	 to	 Principal	 and	 Head,	
Department	of	Chemistry,	Sant	Ramdas	College,	Ghansawangi,	
Dist.	 Jalna	affiliated	 to	Dr.	Babasaheb	Ambedkar	Marathwada	
University,	 Aurangabad,	 431004	 (MS),	 India	 for	 providing	
financial	assistance	for	instrument	help.	
	
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