untitled


European	Journal	of	Chemistry	2	(2)	(2011)	260‐265	

	
European	Journal	of	Chemistry	

ISSN	2153‐2249	(Print)	/	ISSN	2153‐2257	(Online)		2011	EURJCHEM	
DOI:10.5155/eurjchem.2.2.260‐265.263	

	
	

	

	

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

	 	 	

Tin(II)chloride	catalyzed	synthesis	of	pyranoquinolines,	phenanthridinone	and	
phenanthridine	derivatives	

Lingaiah	Nagarapu*,	Rajashaker	Bantu	and	Ravinder	Goud	Puligoundla	

Organic	Chemistry	Division‐II,	Indian	Institute	of	Chemical	Technology,	Hyderabad‐500607,	India	

*Corresponding	author	at:	Organic	Chemistry	Division‐II,	Indian	Institute	of	Chemical	Technology,	Hyderabad‐500607,	India.	Tel.:	+91.40.27191509;		
fax:	+91.40.27193382.	E‐mail	address:	lnagarapuiict@yahoo.com	(L.	Nagarapu).	

	
	

	 	

	 	 	
ARTICLE	INFORMATION	 	 ABSTRACT
Received:	27	August	2010	
Received	in	revised	form:	07	October	2010	
Accepted:	30	October	2010	
Online:	30	June	2011	

KEYWORDS	

	 A	simple,	efficient	and	cost‐effective	method	 for	 the	synthesis	of	 tetrahydropyranoquinoline
derivatives	by	a	one‐pot	condensation	of	aromatic	aldehyde,	aromatic	amine	and	3,4‐dihydro‐
2H‐pyran	respectively	in	the	presence	of	tin(II)chloride	(SnCl2.2H2O)	has	been	described.	

Synthesis	
Tetrahydropyranoquinolines	
3,4‐Dihydro‐2H‐pyran	
Tin(II)chloride	
Phenanthridine	
Phenanthridinone	

	
1.	Introduction	
	

Tetrahydroquinoline	 derivatives	 are	 important	 class	 of	
natural	 products	 and	 exhibit	 variety	 of	 biological	 activities,	
such	 as	 psychotropic,	 antiallergic,	 antiinflamatory	 and	
estronegic	 [1‐4].	 The	 pyrano	 tetrahydroquinolines	 are	 also	
found	 in	 several	 alkaloids	 [5‐7]	 such	 as	 veprisine,	 flindersine	
and	 oricine.	 The	 imino	 Diels‐Alder	 reaction	 provides	 a	 useful	
entry	to	the	preparation	of	tetrahydroquinolines	derivatives	[8‐
10].	 Imines	derived	from	aromatic	amines	act	as	heterodienes	
and	 undergo	 imino	 Diels‐Alder	 reaction	 with	 various	
dienophiles.	 Some	 improved	 procedures	 have	 been	 reported	
for	 the	 reaction	 of	 3,4‐dihydro‐2H‐pyran	 (DHP)	 with	 aniline	
using	BF3.OEt2	[11],	GdCl3	[12],	InCl3	[13],	LiClO4	[14],	ZrCl4	[15],	
TMSCl	 [16],	 I2	 [17],	 SbCl3	 [18],	 SbCl3‐HPA	 [19],	 PMA	 [20],	
CF3CO2H	[21].	

Recently,	 SnCl2.2H2O	 has	 emerged	 as	 catalyst	 in	 various	
organic	 transformations,	 including	 synthesis	 of	 bisindolyl‐
methanes	 [22],	 conjugate	 addition	 of	 indoles	 to	 ,‐unsatu‐
rated	 ketones	 [23],	 the	 Paal‐Knorr	 synthesis	 of	 pyrroles	 [24],	
the	 Fischer	 synthesis	 of	 indole	 [25],	 and	 the	 synthesis	 of	 β‐
acetamido	ketones	and	β‐acetamido	ketoesters	[26].	In	view	of	
its	 inherent	 properties	 such	 as	 environmental	 compatibility,	
reusability,	 greater	 selectivity,	 operational	 simplicity,	 non‐
corrosiveness,	 low	 cost	 and	 ease	 of	 isolation,	 we	 wish	 to	
describe	 our	 results	 on	 SnCl2.2H2O	 catalyzed	 one‐pot	
condensation	 of	 quinoline	 derivatives	 with	 aryl	 aldehydes,	
aromatic	 anilines,	 and	 3,4‐dihydro‐2H‐pyran	 at	 room	
temperature	(Scheme	1).	

	

	
Scheme	1	

	
2.	Experimental	
	
2.1.	Materials	and	methods	
	

All	 the	 commercial	 reagents	 and	 solvents	 were	 used	
without	 further	 purification	 unless	 otherwise	 stated.	 Melting	
points	were	recorded	on	a	Buchi	535	melting	point	apparatus	
and	are	uncorrected.	All	the	reactions	were	monitored	by	thin	
layer	chromatography	performed	on	precoated	silica	gel	60F254	
plates	 (Merck).	 Compounds	 were	 visualized	 with	 UV	 light	 at	
254	nm	and	365	nm,	I2	and	heating	plates	after	dipping	in	2%	
phosphomolybdic	 acid	 in	 15%	 aq.	 H2SO4	 solution.	 IR	 spectra	
were	 recorded	 on	 a	 Perkin‐Elmer	 683	 or	 a	 1310	 FT‐IR	
spectrometers	with	KBr	pellets.	1H	NMR	spectra	were	recorded	
on	 BRUKER	 AMX	 300	 spectrometers	 using	 tetramethylsilane	
(TMS)	as	an	internal	standard.	Mass	spectra	were	recorded	on	
a	 VG	 Micromass	 7070H	 and	 a	 Finnigan	 Mat	 1020B	 mass	
spectrometers	operating	at	70	eV.			
	



Nagarapu	et	al.	/	European	Journal	of	Chemistry	2	(2)	(2011)	260‐265	 261	
 

 
 

2.2.	General	reaction	procedure	for	synthesis	of	tetrahyro‐
quinolines	
	

To	 a	 suspension	 of	 SnCl2.2H2O	 (46	 mg,	 0.2	 mmol),	
acetonitrile	 (2.5	 mL)	 and	 anhydrous	 Na2SO4	 (150	 mg)	 were	
added	 a	 solution	 of	 benzalehyde	 (212	 mg,	 2.0	 mmol)	 in	
acetonitrile	 (2.5	 mL)	 and	 a	 solution	 of	 aniline	 (205	 mg,	 2.2	
mmol)	 in	acetonitrile	(2.5	mL)	at	room	temperature	(r.t.).	The	
mixture	was	stirred	for	5	min	at	r.t.	Then	3,4‐dihydro‐2H‐pyran	
(218	mg,	2.6	mmol)	was	added	and	the	mixture	stirred	for	the	
period	 of	 time	 as	 mentioned	 in	 the	 Table	 2.	 Thin	 layer	
chromatography	 (TLC)	 monitored	 (ethyl	 acetate:hexane,	 2:8)	
completion	 of	 the	 reaction,	 it	 was	 quenched	 with	 H2O	 and	
extracted	 with	 CH2Cl2	 (2	 x	 25	 mL)	 and	 dried	 (Na2SO4).	 The	
solvent	 was	 evaporated	 and	 the	 crude	 residue	 obtained	 was	
purified	 by	 column	 chromatography	 (silica	 gel;	 ethyl	
acetate:hexane,	 10:90)	 to	 give	 pure	 tetrahydropyrano‐
quinolines	4	and	5	(503	mg,	95%).	
	
2.3.	Spectral	data	of	some	of	the	representative	compounds	
	
2.3.1.	5‐(4‐Nitro‐phenyl)‐3,4,4a,5,6,10b‐hexahydro‐2H‐
pyrano[3,2‐c]quinoline	(Table	2,	entry	d)		
	

Cis	 isomer:	 M.p.:	 164‐165	 oC.	 Rf	 (20%	 EtOAc/n‐hexane):	
0.5.	 IR	(KBr)	(νmax,	cm‐1):	3374	(N‐H),	3040,	2923,	2855,	1515,	
1345,	 1068,	 759.	 1H	 NMR	 (300	MHz,	 CDCl3,	 ):	 1.17‐1.59	 (m,	
4H),	2.16‐2.24	(m,	1H),	3.41	(dt,	J	=	2.9	Hz,	9.5	Hz,	1H),	3.61	(dd,	
J	=	3.2	Hz,	11.9	Hz,	1H),	 3.81	 (s,	 1H),	 4.68	 (d,	 J	=	2.2	Hz,	1H),	
5.31	(d,	J	=	5.8	Hz,	1H),	6.61	(d,	J	=	8.1	Hz,	1H),	6.81	(t,	J	=	7.3	
Hz,	1H),	7.07	(t,	J	=	7.3	Hz,	1H),	7.42	(d,	J	=	8.1	Hz,	1H),	7.64	(d,	J	
=	 8.8	 Hz,	 2H),	 8.26	 (d,	 J	 =	 8.8	 Hz,	 2H).	 MS	 (ESI,	 m/z):	 311	
([M+H])+.	Anal.	Calcd.	for	C18H18N2O3:	C,	69.66;	H,	5.85;	N,	9.03;	
O,	15.47.	Found:	C,	69.64;	H,	5.84;	N,	9.00%.	

Trans	isomer:	M.p.:	136‐137	oC.	Rf	(20%	EtOAc/n‐hexane):	
0.45.	IR	(KBr)	(νmax,	cm‐1):	3377	(N‐H),	3070,	2929,	2852,	1517,	
1344,	 1080,	 750.	 1H	 NMR	 (300	MHz,	 CDCl3,	 ):	 1.20‐1.49	 (m,	
4H),	2.11‐2.22	(m,	1H),	3.44	(dt,	J	=	2.9	Hz,	9.5	Hz,	1H),	3.77	(dd,	
J	=	3.2	Hz,	1.9	Hz,	1H),	4.04	(s,	1H),	4.39	(d,	J	=	2.9	Hz,	1H),	4.85	
(d,	J	=	10.2	Hz,	1H),	6.56	(d,	J	=	7.3	Hz,	1H),	6.74	(t,	J	=	7.3	Hz,	
1H),	7.11	(t,	J	=	7.3	Hz,	1H),	7.23	(d,	J	=	8.8	Hz,	1H),	7.64	(d,	J	=	
8.8	 Hz,	 2H),	 8.26	 (d,	 J	 =	 8.8	 Hz,	 2H).	 MS	 (ESI,	 m/z):	 311	
([M+H])+.	Anal.	Calcd.	for	C18H18N2O3:	C,	69.66;	H,	5.85;	N,	9.03;	
O,	15.47.	Found:	C,	69.66;	H,	5.84;	N,	9.01%.		
	
2.3.2.	5‐(2,4‐Dichloro‐phenyl)‐3,4,4a,5,6,10b‐hexahydro‐2H‐
pyrano[3,2‐c]quinoline	(Table	2,	entry	e)	
	

Cis	 isomer:	 M.p.:	 132‐134	 oC.	 Rf	 (20%	 EtOAc/n‐hexane):	
0.5.	 IR	(KBr)	(νmax,	cm‐1):	3374	(N‐H),	3040,	2923,	2855,	1515,	
1345,	 1068,	 759.	 1H	 NMR	 (300	MHz,	 CDCl3,	 ):	 1.39‐1.57	 (m,	
4H),	2.18‐2.38	(m,	1H),	3.42	 (dt,	 J	=	3.0	Hz,	11.3	Hz,	1H),	3.58	
(dd,	J	=	3.7	Hz,	11.3	Hz,	1H),	5.01	(d,	J	=	2.2	Hz,	1H),	5.26	(d,	J	=	
5.2	Hz,	1H),	6.55	(d,	J	=	6.8	Hz,	1H),	6.77	(t,	J	=	7.5	Hz,	1H),	7.03	
(t,	J	=	7.5	Hz,	1H),	7.27	(d,	J	=	8.3	Hz,	1H),	7.64	(m,	2H),	7.62	(d,	J	
=	 8.3	 Hz,	 2H).	 MS	 (ESI,	 m/z):	 334	 ([M+H])+.	 Anal.	 Calcd.	 for	
C18H17Cl2NO:	C,	64.68;	H,	5.13;	Cl,	21.21;	N,	4.19;	O,	4.79.	Found:	
C,	64.66;	H,	5.14;	N,	4.18%.	

Trans	 isomer:	 Thick	 syrup.	 Rf	 (20%	 EtOAc/n‐hexane):	
0.45.	IR	(KBr)	(νmax,	cm‐1):	3374	(N‐H),	3040,	2923,	2855,	1515,	
1345,	 1068,	 759.	 1H	 NMR	 (300	MHz,	 CDCl3,	 ):	 1.39‐1.57	 (m,	
4H),	2.18‐2.38	(m,	1H),	3.63	 (dt,	 J	=	3.0	Hz,	11.3	Hz,	1H),	3.92	
(dd,	J	=	3.7	Hz,	11.3	Hz,	1H),	4.37	(d,	J	=	3.7	Hz,	1H),	5.09	(d,	J	=	
8.3	Hz,	1H),	6.49	(d,	J	=	6.8	Hz,	1H),	6.69	(t,	J	=	7.5	Hz,	1H),	7.05	
(t,	 J	 =	 8.3	 Hz,	 1H),	 7.24	 (m,	 3H),	 7.39‐7.45	 (m,	 2H).	 MS	 (ESI,	
m/z):	 334	 ([M+H])+.	 Anal.	 Calcd.	 for	 C18H17Cl2NO:	 C,	 64.68;	 H,	
5.13;	Cl,	21.21;	N,	4.19;	O,	4.79.	Found:	C,	64.68;	H,	5.12;	N,	4.20.		
		

2.3.3.	5‐(3‐Methoxy‐phenyl)‐3,4,4a,5,6,10b‐hexahydro‐2H‐
pyrano[3,2‐c]quinoline	(Table	2,	entry	f)		
	

Cis	isomer:	Thick	syrup;	Rf	(20%	EtOAc/n‐hexane):	0.5.	IR	
(KBr)	 (νmax,	cm‐1):	 3374	 (N‐H),	 3040,	 2923,	 2855,	 1515,	 1345,	
1068,	 759.	 1H	 NMR	 (300	 MHz,	 CDCl3,	 ):	 1.31‐1.68	 (m,	 4H),	
2.09‐2.18	(m,	1H);	3.67	(m,	1H),	3.81	(s,	3H),	4.64	(d,	J	=	2.2	Hz,	
1H),	5.27	(d,	J	=	5.2	Hz,	1H),	6.54	(d,	J	=	8.3	Hz,	1H),	6.78	(t,	J	=	
11.3	Hz,	1H),	7.04	(t,	J	=	7.5	Hz,	3H),	7.24	(d,	J	=	7.5	Hz,	1H),	7.37	
(d,	1H).	MS	(ESI,	m/z):	296	([M+H])+.	Anal.	Calcd.	for	C19H21NO2:	
C,	77.26;	H,	7.17;	N,	4.74;	O,	10.83.	Found:	C,	77.23;	H,	7.17;	N,	
4.75%.	

Trans	isomer:	M.p.:	99‐100	oC;	Rf	(20%	EtOAc/n‐hexane):	
0.48.	IR	(KBr)	(νmax,	cm‐1):	3374	(N‐H),	3040,	2923,	2855,	1515,	
1345,	 1068,	 759.	 1H	 NMR	 (300	MHz,	 CDCl3,	 ):	 1.37‐1.55	 (m,	
4H),	2.09‐2.21	(m,	1H),	3.69	(dt,	J	=	3.0	Hz,	9.8	Hz,	1H),	3.79	(s,	
3H),	4.09	(dd,	J	=	3.7	Hz,	11.3	Hz,	1H),	4.34	(d,	J	=	2.2	Hz,	1H),	
4.67	(d,	J	=	10.5	Hz,	1H),	6.48	(d,	J	=	7.5	Hz,	1H),	6.65	(t,	J	=	8.3	
Hz,	1H),	6.81	(dd,	 J	=	3.7,	8.3	Hz,	1H),	6.94	(d,	 J	=	8.3	Hz,	2H),	
7.04	(dt,	J	=	1.51,	7.5	Hz,	1H),	7.16	(dd,	J	=	1.5,	7.5	Hz,	1H),	7.24	
(dd,	 J	 =	 1.5,	 7.5	 Hz,	 1H).	 MS	 (ESI,	 m/z):	 296	 ([M+H])+.	 Anal.	
Calcd.	for	C19H21NO2:	C,	77.26;	H,	7.17;	N,	4.74;	O,	10.83.	Found:	
C,	77.25;	H,	7.18;	N,	4.74%.	
	
2.3.4.	9‐Isopropyl‐5‐phenyl‐3,4,4a,5,6,10b‐hexahydro‐2H‐
pyrano[3,2‐c]quinoline	(Table	2,	entry	i)	
	

Cis	 isomer:	 M.p.:	 108‐109	 oC.	 Rf	 (20%	 EtOAc/n‐hexane):	
0.5.	 IR	(KBr)	(νmax,	cm‐1):	3374	(N‐H),	3040,	2923,	2855,	1515,	
1345,	1068,	759.	1H	NMR	(300	MHz,	CDCl3,	):	1.22	(s,	3H),	1.26	
(s,	3H),	1.41‐1.58	(m,	4H),	2.09‐2.15	(m,	1H),	2.83	(m,	1H),	3.38	
(dt,	 J	=	3.6	Hz,	15.2	Hz,	1H),	3.57	(dd,	J	=	3.7	Hz,	11.3	Hz,	1H),	
3.71	(s,	1H),	4.65	(d,	J	=	2.2	Hz,	1H),	5.29	(d,	J	=	6.5	Hz,	1H),	6.55	
(d,	 J	=	8.0	Hz,	1H),	6.93	(dd,	J	=	2.2,	8.0	Hz,	1H),	7.25‐7.41	(m,	
6H).	MS	(ESI,	m/z):	308	([M+H])+.	Anal.	Calcd.	for	C21H25NO:	C,	
82.04;	 H,	 8.20;	 N,	 4.56;	 O,	 5.20.	 Found:	 C,	 82.05;	 H,	 8.22;	 N,	
4.55%.	

Trans	 isomer:	 M.p.:	 95‐98	 oC.	Rf	 (20%	 EtOAc/n‐hexane):	
0.48.	IR	(KBr)	(νmax,	cm‐1):	3374	(N‐H),	3040,	2923,	2855,	1515,	
1345,	1068,	759.	1H	NMR	(300	MHz,	CDCl3,	):	1.22	(s,	3H);	1.27	
(s,	3H),	1.41‐1.58	(m,	4H),	2.09‐2.15	(m,	1H),	2.83	(m,	1H),	3.38	
(dt,	 J	=	3.6	Hz,	15.2	Hz,	1H),	3.57	(dd,	J	=	3.7	Hz,	11.3	Hz,	1H),	
3.69	(s,	1H),	4.33	(d,	 J	=	2.2	Hz,	1H),	4.64	(d,	 J	=	10.2	Hz,	1H),	
6.55	(d,	J	=	8.3	Hz,	1H),	7.02	(dd,	J	=	2.2,	8.0	Hz,	1H),	7.31‐7.44	
(m,	6H).	MS	(ESI,	m/z):	308	([M+H])+.	Anal.	Calcd.	for	C21H25NO:	
C,	82.04;	H,	8.20;	N,	4.56;	O,	5.20.	Found:	C,	82.04;	H,	8.19;	N,	
4.58%	

	

2.3.5.	5‐(4‐Bromo‐phenyl)‐9‐isopropyl‐3,4,4a,5,6,10b‐
hexahydro‐2H‐pyrano[3,2‐]quinoline	(Table	2,	entry	j)	
	

Cis	 isomer:	 M.p.:	 104‐105	 oC.	 Rf	 (20%	 EtOAc/n‐hexane):	
0.5.	 IR	(KBr)	(νmax,	cm‐1):	3368	(N‐H),	2936,	2860,	1493,	1067,	
818.	 1H	 NMR	 (300	MHz,	 CDCl3,	 ):	 1.21	 (s,	 3H),	 1.25	 (s,	 3H),	
1.42‐1.59	 (m,	 2H),	 2.02‐2.13	 (m,	 1H),	 2.74‐2.88	 (m,	 1H),	 3.32	
(dt,	 J	=	2.9	Hz,	10.9	Hz,	2H),	3.52	(dd,	J	=	3.6	Hz,	10.9	Hz,	2H),	
4.92	(d,	J	=	2.18	Hz,	1H),	5.22	(d,	J	=	5.0	Hz,	1H),	6.45	(d,	J	=	8.0	
Hz,	1H),	6.92	(dd,	J	=	2.1	Hz,	8.0	Hz,	1H),	7.22‐7.30	(m,	3H),	7.40	
(d,	 J	=	8.7	Hz,	2H),	7.69	(d,	J	=	8.7	Hz,	1H).	MS	(ESI,	m/z):	386	
([M+H])+.	 Anal.	 Calcd.	 for	 C21H24BrNO:	 C,	 65.29;	 H,	 6.26;	 Br,	
20.68;	N,	3.63;	O,	4.14.	Found:	C,	65.26;	H,	6.26;	N,	3.61%.	

Trans	 isomer:	 M.p.:	 94‐95	 oC.	Rf	 (20%	 EtOAc/n‐hexane):	
0.45.	IR	(KBr)	(νmax,	cm‐1):	3368	(N‐H),	2936,	2860,	1493,	1067,	
818.	 1H	 NMR	 (300	MHz,	 CDCl3,	 ):	 1.94	 (s,	 3H),	 1.23	 (s,	 3H),	
1.39‐1.54	 (m,	 2H),	 2.02‐2.13	 (m,	 1H),	 2.72‐2.82	 (m,	 1H),	 3.62	
(dt,	J	=	2.1,	11.65	Hz,	2H),	4.04	(dd,	J	=	2.1,	11.6	Hz,	2H),	4.30	(d,	
J	=	2.1	Hz,	1H),	4.60	(d,	J	=	10.9	Hz,	1H),	6.45	(d,	J	=	8.0	Hz,	1H),	
6.95	(dd,	J	=	2.1,	8.0	Hz,	1H),	7.01‐7.02	(d,	J	=	2.18,	2H),	7.28	(d,	



262	 Nagarapu	et	al.	/	European	Journal	of	Chemistry	2	(2)	(2011)	260‐265	
	
J	=	 8.01	Hz,	 2H),	 7.48	 (d,	 J	=	 8.7	 Hz,	 1H).	MS	 (ESI,	m/z):	 386	
([M+H])+.	 Anal.	 Calcd.	 for	 C21H24BrNO:	 C,	 65.29;	 H,	 6.26;	 Br,	
20.68;	N,	3.63;	O,	4.14.	Found:	C,	65.28;	H,	6.27;	N,	3.65%.	

	
2.3.6.	9‐Fluoro‐5‐phenyl‐3,4,4a,5,6,10b‐hexahydro‐2H‐
pyrano[3,2‐c]quinoline	(Table	2,	entry	k)	
	

Cis	 isomer:	 M.p.:	 158‐159	 oC.	 Rf	 (20%	 EtOAc/n‐hexane):	
0.5.	 1H	NMR	 (300	MHz,	 CDCl3,	):	 1.37‐1.55	 (m,	 4H),	 2.14	 (m,	
1H),	 3.42	 (dt,	 J	=	3.02	Hz,	11.3	Hz,	 1H),	 3.60	 (dd,	 J	=	3.02	Hz,	
11.3	Hz,	1H),	3.70	(br	s,	1H,),	4.63	(d,	J	=	3.0	Hz,	1H),	5.23	(d,	J	=	
6.0	Hz,	1H),	6.45‐6.49	(d,	J	=	4.5	Hz,	1H),	6.78	(dt,	J	=	3.0	Hz,	8.3	
Hz,	1H),	7.08‐7.12	(dd,	J	=	3.0	Hz,	8.3	Hz,	1H),	7.24‐7.39	(m,	5H).	
MS	 (ESI,	 m/z):	 284	 ([M+H])+.	 Anal.	 Calcd.	 for	 C18H18FNO:	 C,	
76.30;	H,	6.40;	F,	6.71;	N,	4.94;	O,	5.65.	Found:	C,	76.29;	H,	6.40;	
N,	4.91%.	

Trans	 isomer:	 M.p.:	 82‐84	 oC.	Rf	 (20%	 EtOAc/n‐hexane):	
0.48.	1H	NMR	(300	MHz,	CDCl3,	):	1.31‐1.50	(m,	2H),	1.57‐1.68	
(m,	 1H),	 1.75‐1.87	 (m,	 1H),	 2.07	 (m,	 1H),	 3.71	 (dt,	 J	=	2.2	Hz,	
11.3	Hz,	1H),	3.91	(br	s,	1H),	4.08	(dd,	J	=	3.7	Hz,	10.5	Hz,	1H),	
4.31	(d,	J	=	2.2	Hz,	1H),	4.64	(d,	J	=10.5	Hz,	1H),	6.39‐6.44	(2d,	J	
=	4.5	Hz,	1H),	6.81(dt,	J	=	3.0	Hz,	8.3	Hz,	1H),	6.88‐6.92	(dd,	J	=	
3.0	 Hz,	 9.0	 Hz,	 1H),	 7.24‐7.39	 (m,	 5H).	 MS	 (ESI,	 m/z):	 284	
([M+H])+.	Anal.	Calcd.	for	C18H18FNO:	C,	76.30;	H,	6.40;	F,	6.71;	
N,	4.94;	O,	5.65.	Found:	C,	76.29;	H,	6.41;	N,	4.95%.	
	
2.3.7.	2‐Fluoro‐6‐(4‐fluoro‐phenyl)‐5,6a,7,8,9,10a‐
hexahydro‐6H‐phenanthridin‐10‐one	(Table	2,	entry	o)	
	

Cis	 isomer:	 M.p.:	 120‐121	 oC.	 Rf	 (20%	 EtOAc/n‐hexane):	
0.5.	1H	NMR	(300	MHz,	CDCl3,	):	1.56‐1.94	(m,	3H),	2.26‐2.36	
(m,	2H),	2.58‐2.74	 (m,	2H),	4.36‐4.40	 (m,	1H),	4.64	 (d,	 J	=	3.1	
Hz,	1H),	6.40‐6.46	(m,	2H),	6.72‐6.81	(t,	J	=	7	 .8	Hz,	1H),	7.32‐
7.34	 (m,	 4H).	 MS	 (ESI,	 m/z):	 314	 ([M+H]).	 Anal.	 Calcd.	 for	
C19H17F2NO:	C,	72.83;	H,	5.47;	F,	12.13;	N,	4.47;	O,	5.11.	Found:	
C,	72.80;	H,	5.46;	N,	4.45%.	

Trans	isomer:	M.p.:	114‐115	oC.	Rf	(20%	EtOAc/n‐hexane):	
0.45.	1H	NMR	(300	MHz,	CDCl3,	):	1.68‐1.79	(m,	2H),	1.99‐2.30	
(m,	 2H),	 2.38‐2.45	 (m,	 2H),	 2.69‐2.77	 (m,	 2H),	 4.36‐4.42	 (m,	
1H),	4.54	(d,	J	=	2.0	Hz,	1H),	6.50‐6.55	(m,	2H),	6.79‐6.81	(t,	J	=	
8.3	 Hz,	 1H),	 7.21‐7.32	 (m,	 4H).	 MS	 (ESI,	 m/z):	 314	 ([M+H])+.	
Anal.	Calcd.	for	C19H17F2NO:	C,	72.83;	H,	5.47;	F,	12.13;	N,	4.47;	
O,	5.11.	Found:	C,	72.85;	H,	5.47;	N,	4.45%.	
	
2.3.8.	12‐(2,4‐Dichloro‐phenyl)‐2,3,4a,11,12,12a‐hexahydro‐
1H‐4‐oxa‐11‐aza‐chrysene	(Table	2,	entry	q)	
	

Cis	 isomer:	 M.p.:	 164‐165	 oC.	 Rf	 (20%	 EtOAc/n‐hexane):	
0.5.	1H	NMR	(300	MHz,	CDCl3,	):	1.38‐1.56	(m,	3H),	2.28‐2.36	
(m,	1H),	2.41‐2.51(m,	1H),	3.20‐3.32	(m,	1H),	3.47‐3.53	(m,	1H),	
5.04	(d,	J	=	2.2	Hz,	1H),	5.37	(d,	J	=	5.8	Hz,	1H),	7.17‐7.21	(d,	J	=	
8.0	Hz,	1H),	7.28‐7.45	(m,	3H),	7.64‐7.72	(m,	2H),	7.86‐7.94	(m,	
3H).	MS	(ESI,	m/z):	384	([M+H])+.	Anal.	Calcd.	for	C22H19Cl2NO:	
C,	68.76;	H,	4.98;	Cl,	18.45;	N,	3.64;	O,	4.16.	Found:	C,	68.76;	H,	
4.95;	N,	3.63%.	

Trans	 isomer:	 Thick	 syrup;	 Rf	 (20%	 EtOAc/n‐hexane)	
0.45.	1H	NMR	(300	MHz,	CDCl3,	):	1.25‐1.51	(m,	4H),	2.23‐2.26	
(m,	1H);	2.37(m,	1H),	3.69‐3.73	(m,	1H),	3.93‐3.39	(m,	1H),	4.52	
(d,	 J	=	3.7	Hz,	1H),	5.24	 (d,	 J	=	9.0	Hz,	1H),	7.21‐7.26	 (m,	3H),	
7.32‐7.48	(m,	4H),	7.62‐7.64	(d,	J	=	8.3	Hz,	1H),	7.72‐7.75(d,	J	=	
9.0	 Hz,	 1H).	 MS	 (ESI,	 m/z):	 384	 ([M+H])+.	 Anal.	 Calcd.	 for	
C22H19Cl2NO:	C,	68.76;	H,	4.98;	Cl,	18.45;	N,	3.64;	O,	4.16.	Found:	
C,	68.75;	H,	4.99;	N,	3.65%.	
	
2.3.9.	12‐(2‐Chloro‐phenyl)‐2,3,4a,11,12,12a‐hexahydro‐1H‐
4‐oxa‐11‐aza‐chrysene	(Table	2,	entry	r)	
	

Cis	 isomer:	 M.p.:	 152‐154	 oC.	 Rf	 (20%	 EtOAc/n‐hexane):	
0.5.	 1H	NMR	 (300	MHz,	 CDCl3,	):	 1.21‐1.59	 (m,	 3H),	 2.48	 (m,	
1H),	 3.29‐3.36	 (m,	 1H),	 3.52‐3.61	 (m,	 1H),	 4.29‐4.30	 (m,	 1H),	

5.18	 (d,	 J	=	2.6	Hz,	1H),	5.45	 (d,	 J	=	6.4	Hz,	1H),	7.17‐7.35	(m,	
2H),	7.37‐7.45	(m,	5H),	7.48‐7.54	(m,	2H),	7.93	(d,	J	=	2.07	Hz,	
1H).	MS	(ESI,	m/z):	350	([M+H])+.	Anal.	Calcd.	 for	C22H20ClNO:	
C,	75.53;	H,	5.76;	Cl,	10.13;	N,	4.00;	O,	4.57.	Found:	C,	75.53;	H,	
5.74;	N,	4.01%.	

Trans	 isomer:	 Thick	 syrup.	 Rf	 (20%	 EtOAc/n‐hexane):	
0.48.	1H	NMR	(300	MHz,	CDCl3,	):	1.20‐1.65	(m,	3H),	2.29	(m,	
1H),	 3.36‐3.55	 (m,	 1H),	 3.63‐3.64	 (m,	 1H),	 4.19‐4.60	 (m,	 1H),	
4.61	(d,	J	=	3.6	Hz,	1H),	5.31	(d,	J	=	10.9	Hz,	1H),	6.67‐7.46	(m,	
6H),	 7.62‐7.78	 (m,	 4H).	 MS	 (ESI,	 m/z):	 350	 ([M+H])+.	 Anal.	
Calcd.	 for	 C22H20ClNO:	 C,	 75.53;	 H,	 5.76;	 Cl,	 10.13;	 N,	 4.00;	 O,	
4.57.	Found:	C,	75.55;	H,	5.75;	N,	4.04%.	
	
2.4.	General	procedure	for	the	preparation	of	tetrahydro‐
pyrano[3,2‐c]quinolones	
	

A	mixture	of	aryl	amine	(465	mg,	5	mmol),	3,4‐dihydro‐2H‐
pyran	(100	mg,	12	mmol)	and	SnCl2.2H2O	(46	mg,	0.2	mmol)	in	
acetonitrile	 (5	 mL)	 was	 stirred	 at	 room	 temperature	 for	 the	
appropriate	 time	 (Table	 2).	 TLC	monitored	 completion	 of	 the	
reaction,	 it	was	quenched	with	H2O	and	extracted	with	CH2Cl2	
(2	 x	 25	mL)	 and	 dried	 (Na2SO4).	 The	 solvent	 was	 evaporated	
and	 the	 crude	 residue	 obtained	 was	 purified	 by	 column	
chromatography	 to	 give	 pure	 tetrahydropyrano[3,2‐
c]quinolines	12	and	13	(503	mg,	95%).	

		

2.5.	Spectral	data	of	some	of	the	representative	compounds	
	
2.5.1.	4‐(9‐Isopropyl‐3,4,4a,5,6,10b‐hexahydro‐2H‐
pyrano[3,2‐c]quinolin‐5‐yl)‐butan‐1‐ol	(Table	3,	entry	ii)	
		

Cis	isomer:	Thick	syrup;	IR	(KBr)	(νmax,	cm‐1):	3403	(N‐H),	
2923,	2853,	1506,	1458,	1265,	1089,	760.	 1H	NMR	 (300	MHz,	
CDCl3,	):	7.03	(s,	1H),	6.92	(dd,	J	=	2.2	Hz,	8.30	Hz,	1H),	6.45	(d,	
J	=	8.3	Hz,	1H),	4.43	(d,	J	=	3.0	Hz,	1H),	3.95	(dd,	J	=	3.7	Hz,	15.1	
Hz,	1H),	3.68‐3.52	 (m,	5H),	2.98	 (br	 s,	1H),	2.83‐2.74	 (m,	1H),	
2.01‐1.95	(m,	1H),	1.77‐1.41	(m,	10H),	1.23	(s,	3H),	1.21	(s,	3H).	
MS	(ESI,	m/z):	304	([M+H])+.	

Trans	isomer:	Thick	syrup.	IR	(KBr)	(νmax,	cm‐1):	3383	(N‐
H),	 2928,	 2858,	 1508,	 1459,	 1261,	 1063,	 756.	 1H	 NMR	 (300	
MHz,	 CDCl3,	):	 7.01	 (s,	 1H),	 6.91	 (m,	1H),	 6.45	 (d,	 J	=	8.3	Hz,	
1H),	 5.02	 (d,	 J	=	5.2	Hz,	 1H),	 3.90	 (m,	 1H),	3.71‐3.33	 (m,	 6H),	
2.79‐2.74	(m,	1H),	2.05‐1.95	(m,	1H),	1.73‐1.47	(m,	10H),	1.28‐
1.21	(m,	6H).	13C	NMR	(75	MHz,	CDCl3,	δ):	142.2,	137.9,	127.8,	
127.0,	120.3,	114.5,	73.9,	72.5,	67.1,	62.5,	60.6,	54.2,	49.6,	36.4,	
32.6,	29.6,	24.1,	22.6,	21.1.	MS	(ESI,	m/z):	304	([M+H])+.	
	
2.5.2.	4‐(9‐Trifluoromethoxy‐3,4,4a,5,6,10b‐hexahydro‐2H‐
pyrano[3,2‐c]quinolin‐5‐yl)‐butan‐1‐ol	(Table	3,	entry	iii)	
	

Cis	 isomer:	Thick	syrup.	 IR	(KBr)	(νmax,	cm‐1):	3428	(N‐H),	
2929,	2861,	1504,	1380,	1253,	1154,	616.	 1H	NMR	 (300	MHz,	
CDCl3,	):	6.80	(d,	J	=	2.6	Hz,	1H),	6.68	(dd,	J	=	2.6,	8.0	Hz,	1H),	
6.50	 (d,	 J	=	8.0	Hz,	1H),	4.44	 (d,	 J	=	5.4	Hz,	1H),	3.92	 (m,	1H),	
3.68‐3.48	 (m,	 3H),	 3.48	 (m,	 1H),	 2.00‐1.96	 (m,	 1H),	 1.70‐1.32	
(m,	10H);	MS(ESI)	m/z	346	([M+H])+.	

Trans	isomer:	Thick	syrup.	IR	(KBr)	(νmax,	cm‐1):	3369	(N‐
H),	 2935,	 2859,	 1502,	 1349,	 1251,	 1159,	 757.	 1H	 NMR	 (300	
MHz,	CDCl3,	):	7.06	(d,	J	=	2.2	Hz,	1H),	6.86	(dd,	J	=	2.9	Hz,	8.8	
Hz,	1H),	6.43	(d,	J	=	8.8	Hz,	1H),	4.97	(d,	J	=	5.1	Hz,	1H),	3.68	(m,	
2H),	3.60‐3.51	 (m,	2H),	3.27	 (m,	1H),	2.00‐1.95	 (m,	1H),	1.68‐
1.32	(m,	10H).	13C	NMR	(75	MHz,	CDCl3,	δ):	121.0,	120.4,	114.0,	
78.9,	 71.8,	 67.0,	 62.4,	 60.5,	 53.9,	 34.8,	 31.6,	 30.6,	 29.5,	 25.3,	
22.4,	19.6,	17.6.	MS	(ESI,	m/z):	346	([M+H])+.	
	
	
	
	

 
 



Nagarapu	et	al.	/	European	Journal	of	Chemistry	2	(2)	(2011)	260‐265	 263	
 

 
 

 

 
	

Scheme	2
	

 
	

Scheme	3
	

 
	

Scheme	4
	

	
3.	Results	and	discussion	
	

During	 the	 course	 of	 our	 studies	 directed	 towards	 the	
development	of	practical,	and	eco‐friendly	procedures	[27‐30],	
we	 developed	 the	 applicability	 of	 SnCl2.2H2O	 for	 efficient,	
convenient	 and	 facile	 synthesis	 of	 quinoline	 derivatives	 by	 a	
one‐pot	 condensation	 of	 aryl	 aldehydes,	 substituted	 anilines,	
3,4‐dihydro‐2H‐pyran	and	anhydrous	Na2SO4	 in	acetonitrile	at	
room	 temperature	 (Scheme	 1).	 Initially	 a	 pilot	 reaction	 was	
carried	 out	 using	 benzaldehyde	 (2	mmol),	 aniline	 (2.2	mmol)	
and	 3,4‐dihydro‐2H‐pyran	 (2.6	 mmol)	 in	 the	 presence	 of	
SnCl2.2H2O	 (46	mg,	 0.2	mmol)	without	 any	 solvent.	 After	 4	 h,	
only	 27	 %	 of	 a	 mixture	 of	 the	 C‐2	 epimers	 (4	 and	 5)	 of	 a	
tetrahydroquinoline	 product	 was	 isolated	 as	 1:1	 ratio.	
Increasing	 the	 amount	 of	 SnCl2.2H2O	 did	 not	 improve	 the	
product	 yield	 to	 a	 considerable	 amount.	 Subsequently,	 we	
investigated	the	effect	of	the	different	solvents	on	the	reaction	
rate	 as	 well	 as	 the	 yields	 of	 the	 products.	 It	 was	 found	 that	
MeCN	was	 the	 best	 solvents	 for	 our	 reaction.	 In	 coordinating	
solvents	 such	 as	 THF,	 Et2O	 and	 DME,	 the	 reaction	 was	 very	
slow	and	resulted	in	lower	product	yields.	Similar	results	were	
obtained	 in	 protic	 solvents	 such	 as	 MeOH	 and	 EtOH.	 After	
screening	 for	 different	 solvents,	 MeCN	 came	 out	 as	 the	 best	
solvent	of	 the	choice,	which	not	only	afforded	 the	products	 in	
good	yield,	but	also	higher	reaction	rates	(95%	yield)	(Table	1).	
It	was	 interesting	 to	note	 that	 the	 trans	 isomer	5	was	 always	
obtained	as	the	major	product	(Table	2).	

We	 first	 investigated	 the	 synthesis	 of	 5‐Phenyl‐
3,4,4a,5,6,10b‐hexahydro‐2H‐pyrano[3,2‐c]quinolines	(4a)	and	
(5a).	 Reaction	 of	 benzaldehyde	 1	 (212	 mg,	 2.0	 mmol)	 with	
aromatic	 amine	 2	 (202	 mg,	 2.2	 mmol),	 and	 3,4‐dihydro‐2H‐
pyran	3	(218	mg,	2.6	mmol)	in	the	presence	of	SnCl2.2H2O	(0.2	
mmol),	 anhydrous	 Na2SO4	 (	 150	 mg)	 and	 CH3CN	 (2.5	 mL)	 at	
room	 temperature	 for	1.8	h	gave	4a	white	 crystalline	powder	

melting	point	204‐205	oC	and	5a	as	a	viscous	oil	in	30:70	ratio	
(0.50	g,	95	%	yield)	(Scheme	1).	

In	 order	 to	 extend	 the	 scope	 of	 this	 catalytic	
transformation,	 the	 general	 applicability	 of	 this	 method	 was	
verified	 by	 reacting	 with	 the	 number	 of	 substituted	
benzaldehydes,	 substituted	 anilines	 and	 different	 dienophiles.	
Cyclohexen‐1‐one	(6)	was	utilized	to	obtain	the	corresponding	
phenanthridinone	derivatives	(7n‐o)	and	(8n‐o)	(70:30)	in	79	
%	yield	(Scheme	2).	
	
Table	1.	Effect	of	solvents	in	the	condensation	of	benzaldehyde,	aniline	and	
3,4‐dihydro‐2H‐pyran	in	the	presence	of	SnCl2.2H2O.	
Entrya Solvent	 Reaction	 time	

(min)	
Yield	(%)b

1 Neat 300	 27
2 MeOH 240	 36
3 EtOH 240	 42
4 THF 180	 45
5 Ether 120	 44
6 DME 180	 52
7 CH2Cl2 60	 63
8 CHCl3 60	 64
9 CH3CN 40	 92
a	 All	 reactions	 were	 performed	 using	 benzaldehyde	 (1	 mmol),	 aniline	 (1.2	
mmol),	3,4‐dihydro‐2H‐pyran	(1.2	mmol),	and	SnCl2.	2H2O	(0.2	mmol).	
b	Combined	isolated	yields.	

	
Phenanthridine	 skeletons	 [31]	 are	 present	 in	 lycorine,	

chelidonine	 and	 haemanthamine	 alkaloids.	 SnCl2.2H2O	 also	
catalyzed	 effectively	 the	 imino	 Diels‐Alder	 reaction	 of	 in	 situ	
generated	N‐benzylidene‐1‐napthylamine	(9)	with	3,4‐dihydro‐
2H‐pyran	 and	 2,3‐dihydrofuran	 to	 afford	 the	 phenanthridine	
derivatives	(10)	and	(11)	as	a	mixture	of	cis	and	trans	isomers	
in	 good	 overall	 yields	 (59‐62%)	 (Scheme	 3).	 The	 pyran	 ring	
was	 cis‐fused	 in	 the	 tetrahydroquinoline	 moiety	 and	 the	
stereochemistry	of	 the	products	was	established	based	on	 the	
coupling	constants.		



264	 Nagarapu	et	al.	/	European	Journal	of	Chemistry	2	(2)	(2011)	260‐265	
	

	 	
Table	2.	The	reaction	times	and	isolated	product	yields	of	the	selected	compounds.	
Entry	 R1	 R2	 Product	 Reaction	Time	(h) Product	ratio	(%) Yield	(%)a	 Reference
1	 H		 H		 a		 1.8	 30:70	 95.0		 [15]	
2	 4‐F		 H		 b		 2.0	 18:82	 91.8		 [15]	
3	 4‐OMe		 H		 c		 2.0	 36:64	 94.1		 [15]	
4	 4‐NO2		 H		 d		 2.0	 22:78	 82.1		 ‐
5	 2,4‐Cl2		 H		 e		 1.8	 29:71	 93.2		 ‐
6	 3‐OMe		 H		 f		 2.0	 33:67	 87.3		 ‐
7	 4‐Cl		 H		 g		 2.0	 34:66	 80.7		 [15]	
8	 4‐Me	 H	 h	 1.8 28:72 86.2	 [14]
9	 H	 (CH3)2‐CH	 i	 2.0 39:61 80.5	 ‐
10	 4‐Br	 (CH3)2‐CH4‐	 j	 1.5 36:64 75.8	 ‐
11	 H	 F	 k	 2.0 42:58 71.2	 ‐
12	 H	 4‐Cl	 l	 1.5 39:61 84.6	 [15]
13	 H		 4‐Br		 m		 1.5	 44:56	 82.5		 [15]	
14	 H		 H		 n		 1.5	 30:70	 79.2		 [11]	
15	 4‐F	 4‐F	 o	 1.5 28:72 76.4	 ‐
16	 H	 1‐Naphthyl	 p	 3.0 36:64 62.0	 [15]
17	 2,4‐Cl	 1‐Naphthyl	 q	 3.0 40:60 60.8	 ‐
18	 2‐Cl	 1‐Naphthyl	 r	 3.0 35:65 59.5	 ‐
a	Combined	isolated	yields.	
	
Table	3.	Reaction	of	anilines	with	dihydropyran	by	SnCl2.	2H2O	catalyzed	synthesis	of	tetrahydropyrano[3,2‐c]quinolones.	
Entry	 Aryl	amine	 Olefin	 Reaction	time	(h) Yield	(%)	 trans	/	cisa
i	

	
	

3.0 90 95:5	

ii	 NH2

	

	

3.5 87 93:7	

iii	 NH2

OCF3 	

	

3.5 85 93:7	

iv	

	

	

3.0 88 95:5	

v	

	

	

3.0 89 90:10

a	Products	ratio	was	determined	by	the	1H	NMR	spectrum	of	the	crude	product.	
	
	

The	 coupling	 constant	 of	 C5‐H	 (J4a,5	 =	 4.6‐5.5	 Hz)	 in	 4	
indicated	the	cis	relationship	between	C‐4a	and	C‐5,	whereas	in	
5	 (J4a,5	 =	 10.2‐11.10	 Hz)	 trans	 form.	 The	 simplicity,	 together	
with	 the	 use	 of	 inexpensive,	 non‐toxic	 and	 environmentally	
benign	 nature	 of	 SnCl2.2H2O	 catalyst	 in	 MeCN	 solvent	 is	 a	
remarkable	feature	of	the	procedure.	

The	generality	of	the	present	protocol	was	then	extended	to	
trans	 (12),	 cis	 (13)	 isomers	 of	 tetrahydropyrano[3,2‐c]	
quinoline.	The	 reactions	proceeded	efficiently	 in	90%	yield	 at	
ambient	 temperature.	 In	most	of	 the	cases,	 the	products	were	
obtained	 as	 a	 mixture	 of	 cis	 and	 trans‐isomers	 favoring	 the	
trans	 diastereomers	 as	 observed	 by	 others	 in	 most	 of	 the	
Povarov	 imino	 Diels‐Alder	 reactions	 [32]	 (Scheme	 4).	 The	
product	 ratio	was	determined	based	on	previous	 reports	 [33]	
by	1H	NMR	spectrum	of	 the	crude	product	and	the	results	are	
summarized	in	Table	3.	
	
4.	Conclusion	
	

In	 conclusion,	 we	 have	 developed	 a	 new	 and	 effective	
methodology	 for	 the	 synthesis	of	 tetrahydropyranoquinolines,	
phenanthridinone,	 phenanthridine	 and	 pyranoquinoline	 (with	
2	 equiv.	 of	 cyclic	 enol	 ether)	 derivatives	 in	 one‐pot	 synthesis	
using	a	catalytic	amount	of	SnCl2.2H2O.	The	notable	features	of	
this	procedure	mild	and	neutral	reaction	conditions,	high	yields	
of	 products,	 the	 low	 cost	 and	 commercially	 availability	 of	 the	
catalyst,	 simple	 and	 easy	 isolation	 of	 the	 products	 the	 main	
advantages	 over	 existing	 procedures	 for	 the	 synthesis	 of	
quinoline,	 phenanthridinone	 and	 phenanthridine	 derivatives.	

The	 ambient	 reaction	 conditions,	 shorter	 reaction	 times,	
excellent	 product	 yields	 make	 this	 catalytic	 system	 an	
alternative	method	for	the	synthesis	of	these	derivatives.	
	
Acknowledgements	
	

The	 authors	 are	 thankful	 to	 the	 Dr.	 J.	 S.	 Yadav	 Director,	
Indian	Institute	of	Chemical	Technology	and	Dr.	V.	V.	Narayana	
Reddy	Head,	Organic	Chemistry	Division‐II,	 Indian	 Institute	of	
Chemical	 Technology,	 Hyderabad	 for	 their	 constant	
encouragement	and	support.	
	
References	
	
[1]. Nesterova,	I.	N.;	Alekseeva,	L.	M.;	Andreeva,	L.	M.;	Andreeva,	N.	I.;	

Golovira,	S.	M.;	Granic,	V.	G.	Khim.	Form.	Zh.	(Russ.)	1995,	29,	31‐34.	
[2]. Yamada,	N.;	Kadowaki,	S.;	Takahashi,	K.;	Umezu,	K.	Biochem.	

Pharmacol.	1992,	44,	1211‐1213.	
[3]. Faber,	K.;	Stueckler,	H.;	Kappe,	T.	J.	Hetrocycl.	Chem.	1984,	21,	1177‐

1181.		
[4]. Akhmed,	Kh.	S.;	Bessonova,	I.	A.	Dokl.	Akad,	Nauk.	Uzh.,	SSR	1982,	34‐

36	(Russ.);	Chem.	Abstr.	1983,	98,	83727q.		
[5]. Anzino,	M.;	Cappelli,	A.;	Vomero,	S.;	Cagnatto,	A.;	Skorupska,	M.	Med.	

Chem.	Res.	1993,	3,	44‐46.		
[6]. Quraishi,	M.	A.;	Thakur,	V.	R.;	Dhawan,	S.	N.	Indian	J.	Chem.	Sect.	B.	

1989,	28B,	891‐893.		
[7]. Ramesh,	M.;	Mohan,	P.	S.;	Shanmugam,	P.	Tetrahedron	1984,	40,	4041‐

4049.	
[8]. Young,	K.	K.;	Sun,	M.	K.;	Dae,	Y.	K.	J.	Am.	Chem.	Soc.	2010,	132,	1184‐

1149.	
[9]. Vladimir,	V.	K.	Tetrahedron	2009,	65,	2721‐2750.	
[10]. Paul,	B.;	Jonh‐Carl,	O.;	Taeboem,	O.	Tetrahedron	2001,	57,	6099‐6138.	



Nagarapu	et	al.	/	European	Journal	of	Chemistry	2	(2)	(2011)	260‐265	 265	
 

 
 

[11]. Kametani,	T.;	Takeda,	H.;	Suzuki,	Y.;	Honda,	T.	Synth.	Commun.	1985,	
15,	499‐505.	

[12]. Ma,	Y.;	Qian,	C.;	Xie,	M.;	Sun,	J.	J.	Org.	Chem.	1999,	64,	6462‐6467.	
[13]. Babu,	G.;	Perumal,	P.	T.	Tetrahedron	Lett.	1998,	39,	3225‐3228.	
[14]. Yadav,	J.	S.;	Subba	Reddy,	B.	V.;	Srinivas.	R.;	Madhuri,	Ch.;	Ramalingam,	

T.	Synlett.	2001,	0240‐0242.	
[15]. Mahesh,	M.;	Venkateswar,	R.	C.;	Srinivas,	R.	K.;	Raju,	P.	V.	K.;	Narayana,	

R.	V.	V.	Synth.	Commun.	2004,	34,	4089‐4104.		
[16]. Shivaji.	V.	M.;	Sastry.	M.	N.;	Ching‐Fa,	Y.	Synlett.	2006,	1399‐1403.	
[17]. Min,	X.;	Yue‐dong,	L.	Synlett.	2005,	2357‐2361.		
[18]. Gourhari,	M.;	Pradip,	K.	Tetrahedron	Lett.	2006,	47,	5733‐5736.	
[19]. Mahajan,	D.;	Ganai,	B.	A.;	Sharma,	R.	L.;	Kapoor,	K.	K.	Tetrahedron	Lett.	

2006,	47,	7919‐7921.	
[20]. Nagaiah,	K.;	Sreenu,	D.;	Rao,	R.	S.;	Vashishta,	G.;	Yadav,	J.	S.	

Tetrahedron	Lett.	2006,	47,	4409‐4413.	
[21]. Xing,	X.;	Wu,	J.;	Baishya,	G.;	Wei‐Min,	D.	Tetrahedron	2006,	62,	11200‐

11206.	
[22]. Gu,	D.	A.;	Ji,	S.	H.;	Jang,	Z.Q.;	Zhou,	M.	F.;	Loh,	T.	P.	Synlett.	2005,	0959‐

0962.	
[23]. Yadav,	J.	S.;	Subba	Reddy,	B.V.;	Baishya,	G.;	Reddy,	Narsaiah,	K.V.	

Tetrahedron	2005,	61,	9541‐9544.		
[24]. Wang,	B.	Y.;	Gu,	C.;	Luo,	T.;	Yang,	L.;	Suo,	J.	Tetrahedron	Lett.	2004,	45,	

3417‐3419.	
[25]. Rebeiro,	G.	L.;	Khadlikar,	B.	M.	Synthesis	2001,	0370‐0372.	
[26]. Nagarapu,	L.;	Venkateswarlu,	P.;	Gopal,	P.;	Srinivas,	K.;	Ruparani,	P.;	

Radhika	K.	J.	Mol.	Cat.	A:	Chem.	2007,	26,	53‐56.	
[27]. Nagarapu,	L.;	Chary,	M.	V.;	Satyender,	A.;	Srinivas,	K.	Cat.	Communs.	

2007,	8,	1173‐1177.	
[28]. Nagarapu,	L.;	Rajashaker,	B.;	Rakesh,	P.	Appl.	Catal.	A:	General	2007,	

332,	304‐309.	
[29]. Nagarapu,	L.;	Rajashaker,	B.;	Hari	Babu,	M.	J.	Heterocyclic	Chem.	2009,	

48(4),	728‐731.	
[30]. Nagarapu,	L.;	Venkata	Narsimhaji,	C.	H.;	Shukla,	C.	K.;	Rajashaker,	B.	

Synthesis	2010,	3374‐3378.	
[31]. Wildman,	W.	C.	Alkaloids	1960,	6,	289‐289.	
[32]. Povarov,	L.	S.	Russ.	Chem.	Rev.	1967,	36,	656‐657.		
[33]. Yadav,	J.	S.;	Subba	Reddy,	B.	V.;	Srinivas,	R.;	Kiran,	K.	S.;	Kunwar,	A.	C.	

Tetrahedron	2003,	58,	1599‐1604.