DMSO and iodine mediated reaction of 4-hydroxycoumarins and aldehydes/aryl methyl ketones: Synthesis of furo[3,2-c]coumarins

Article abstract of DOI:10.1016/j.tet.2015.12.016

A simple and efficient method for the synthesis of highly functionalized furo[3,2-c]coumarins was developed. The reaction occurred via initial formation of biscoumarins from the reaction of 4-hydroxycoumarins and aldehydes/aryl methyl ketones in the prese

Full text of DOI:10.1016/j.tet.2015.12.016

Accepted Manuscript
DMSO and Iodine Mediated Reaction of 4-Hydroxycoumarins and Aldehydes/Aryl
Methyl Ketones: Synthesis of Furo[3,2-c]coumarins
Sinki Kolita, Pallabi Borah, P. Seetham Naidu, Pulak J. Bhuyan
PII:
S0040-4020(15)30266-0
10.1016/j.tet.2015.12.016
TET 27342
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 20 October 2015
Revised Date: 4 December 2015
Accepted Date: 7 December 2015
Please cite this article as: Kolita S, Borah P, Naidu PS, Bhuyan PJ, DMSO and Iodine
Mediated Reaction of 4-Hydroxycoumarins and Aldehydes/Aryl Methyl Ketones: Synthesis of
Furo[3,2-c]coumarins, Tetrahedron (2016), doi: 10.1016/j.tet.2015.12.016.
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ACCEPTED MANUSCRIPT
Graphical Abstract
DMSO and Iodine Mediated Reaction of 4-Hydroxy-
coumarins and Aldehydes/Aryl Methyl Ketones:
Synthesis of Furo[3,2-c]coumarins
Leave this area blank for abstract info.
Sinki Kolita, Pallabi Borah,a P. Seetham Naidu and Pulak J Bhuyan*
Medicinal Chemistry Division,CSIR-North East Institute of Science and Technology, Jorhat-785006, Assam, India.
aPresent Address: USTM, Meghalaya.
R1
O
O
H
R2
O
CH3
R2
O
O
R2
O
R2
OR
O
O
O
2
4
80 oC,
O
OR
80 oC, 4-5 h
OH
O
HO
OH
O
O
R1
1-1.5 h
R1
R1
3
I2, DMSO
R1
5
1

Tetrahedron
1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
DMSO and Iodine Mediated Reaction of 4-Hydroxycoumarins and
Aldehydes/Aryl Methyl Ketones: Synthesis of Furo[3,2-c]coumarins
Sinki Kolita, Pallabi Borah,a P. Seetham Naidu and Pulak J Bhuyan*
Medicinal Chemistry Division, CSIR-North-East Institute of Science & Technology, Jorhat 785006, Assam, India. aPresent
Address: USTM, Meghalaya.
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
A simple and efficient method for the synthesis of highly functionalized furo[3,2-
c]coumarins was developed. The reaction occurred via initial formation of biscoumarins
from the reaction of 4-hydroxycoumarins and aldehydes/aryl methyl ketones in the
presence of molecular iodine in DMSO followed by lactone ring opening, cyclization and
oxidative aromatization process. The reaction conditions were moderate, work-up
procedure was simple and products were obtained in high yield.
Available online
Keywords:
4-Hydroxycoumarin,
Aldehyde,
Iodine,
2015 Elsevier Ltd. All rights reserved.
dimethylsulfoxide,
Furo[3,2-c]coumarin
1. Introduction
Very recently, an excellent review on coumarin heterocyclic
derivatives has been published.11
Coumarin and its derivatives are well-recognized naturally
occurring compounds with diverse biological activities.1
Furanocoumarins, particularly furo[3,2-c]coumarins are an
important class of fused coumarins produced by a variety of
plants2 that possess significant biological, pharmacological
and therapeutic activities, such as antifungicidal, insecticidal,
insect antifeedant, anti-HIV and anticancer activities.3
Compounds bearing this molecular motif also exhibit
photochemical, photophysical and photobiological activities,
and have wide applications as drugs for skin and autoimmune
disease as they are photosensitizers of plant origin and
increase the sensitivity of biological objects to UVA
radiation.4 Psoralens are example of such type of drugs which
are extensively used in the PUVA (psoralen plus UVA
radiation) therapy for human skin diseases, including
psoriasis, mycosis fungoides, eczema, vitiligo, and graft-
versus-host disease.5 Therefore, development of efficient
methods for the synthesis of furo[3,2-c]coumarins, and their
synthetic manipulation have become an important area of
current research. As a result, a number of procedures have
been developed for the the synthesis of these compounds
which include Pd-catalyzed heteroannulation,6 cascade
addition-cyclization-oxidation reaction,7 Suzuki cross-
coupling reaction strategy,8 imidazolium ylide activated [4+1]
annulations,9 intramolecular C-O cyclization reactions10 etc.
______________________
The reaction of 4-hydroxycoumarins and aldehydes in the
presence of acid/Bronsted/Lewis acid catalyst produce
biscoumarins.12 Molecular iodine was also used satisfactorily
as catalyst in the reaction to synthesize biscoumarins.13 But,
Shafiee and his co-workers observed that a very small amount
of furo[3,2-c]coumarins also form along with biscoumarins in
the iodine catalyzed reaction process, and subsequently, they
have developed a method for the synthesis of furo[3,2-
c]coumarins first by synthesizing biscoumarins from 4-
hydroxycoumarins in presence of I2 in poly(ethylene glycol)
followed by treatment of the biscoumarins with K2S2O8 in the
presence of Na2CO3 as oxidizing agent.14 However, the
method has lot of disadvantages like drastic reaction
conditions, long reaction time, expensive reagent, tedious
work-up procedure, chromatographic isolation method and
low yield of the product. Moreover, their study was limited to
aldehydes only. In view of that, very recently, Liu et al.
reported the synthesis of similar compounds from the reaction
of 4-hydroxycoumarins and aldehydes catalyzed by Cu(II)
bromide in presence of pyridine.15 But again, the reaction took
long time for completion, required excess use of pyridine,
products were separated by chromatographic method and the
study was confined to aldehydes only.
Dimethyl sulfoxide (DMSO) is a nontoxic organic solvent
which is used in pharmaceutical synthesis, the manufacture of
electronics, and drug delivery in body. It is also used as a mild
oxidizing agent in various organic transformations, as
demonstrated by many fashionable reactions such as Pfitzner-
*Corresponding author.
E-mail: pulak_jyoti@yahoo.com

2
Tetrahedron
ACCEPTED MANUSCRIPT
Moffatt oxidation, the Swern oxidation etc.16 DMSO with
iodine (DMSO + I2) is a very interesting system of reagent
with diverse application in organic synthesis.17
Table 1: Synthesis of furo[3,2-c]coumarins 3
R1
R2
O
O
O
I2, DMSO
In continuation to our studies on coumarins,18 we report here a
novel and highly efficient reaction protocol for the synthesis
of furo[3,2-c]coumarins from the reaction of 4-
hydroxycoumarins and aldehydes/aryl methyl ketones in the
presence of molecular iodine in DMSO (Scheme 1).
O
H
R2
O
OH
OH
O
O
80 oC,
R1
1-1.5 h
1
2
3
R1
Ent. R1
R2
H
Prod. R.T. Yd. (%)
H
H
1h
1.5h
1.5h
1.5h
1 h
1h
78
72
74
73
89
79
80
79
77
86
88
74
72
1
2
3a
3b
3c
3d
3e
3f
Synthesis of furo[3,2-c]coumarins 3 & 5
Me
C6H5
R1
O
H
3
R2
O
O
I2, DMSO
H
O
H
p-MeC6H4
m-NO2C6H4
p-BrC6H4
p-ClC6H4
C6H5
4
+
O
OH
R2
80 oC, 1-1.5 h
OH
H
O
5
O
R1
2
1
H
6
3
R1 = H, CH3, Cl
R1
R2 = H, CH3, C6H5,
H
1h
7
3g
3h
3i
p-ClC6H4, p-BrC6H4,
O
R2
O
p-CH3C6H4,
m-NO2C6H4
Cl
Cl
Cl
Cl
Me
Me
1h
8
O
O
O
p-MeC6H4
p-BrC6H4
p-ClC6H4
H
1h
9
O
O
HO
R1
1h
10
11
12
13
3j
5
R1
O
I2, DMSO
O
CH3
R2
+
R2
OH
O
80 oC, 4-5 h
CH3
O
3k
3l
1h
4
R2 = C6H5, p-CH3C6H4,
p-ClC6H4,
R1
1
1.5h
1.5h
O
HO
R1
C6H5
3m
R1 = H, CH3,
p-OMeC6H4,
R1
6
Cl
p-BrC6H4
Ent. = Entry, Pd = Product, R.T. = Reaction time, Yd. = Yield
Scheme 1
Mechanism for the formation of furo[3,2-c]coumarins 3
2. Results and Discussion
I2
O
R2
O
The study was initiated with the reaction of 4-
hydroxycoumarin 1 (R1 = H) and formaldehyde 2 (R2 = H) at
2:1 molar ratio in the presence of iodine (15 mol%) as catalyst
in DMSO at room temperature, but no reaction occurred.
Then, the reaction temperature was slowly increased and it
was observed that the reaction occurred very smoothly at
O
O
R2
O
O
O
-H2O
H
HO
O
I2
OH
2
R1
R1
1
1
R1
O
R2 OH
o
80 C to afford the furocoumarin 3a (R1 = H; R2 = H) in
OH
R1
R2 OH
O
R1
excellent yield. Next, the load of the iodine as well as the
reaction time was optimized, and established that 7 mol% of
iodine is sufficient to provide maximum yield of the product
3a in just 1h time. Very interestingly, the product was
obtained in solid and pure form on pouring the reaction
mixture in water followed by removing the iodine by adding
sodium thiosulphate, which could be isolated simply by
filtration. Increase in the reaction temperature and time did
not improve the yield of the product. The structure of the
compound was ascertained from the spectroscopic data,
elemental analysis and by comparing with the authentic
sample.14 In order to establish the generality of the reaction, a
series of furo[3,2-c]coumarins 3a-m were synthesized by
utilizing various substituted coumarins 1 with aldehydes 2,
and characterized (Table 1). It was observed that
formaldehyde was highly reactive and products were obtained
in high yield in crystal form in a short reaction time. The
effect of substituent in the benzene ring of 4-
hydroxycoumarin as well as in aryl aldehydes was also
examined properly and found that electron withdrawing group
at the benzene ring of the coumarin molecule and in the
aromatic ring of the aryl aldehydes produced better yield of
the product in a short reaction time in comparison to the
electron donating group (Table 1).
O
O
OH
OH
O
OH
O
H
O
O
[A]
R1
H
H
R1
O
R2
O
OH
R2
O
OH
R1
O
O
O
-CO2
OH
O
OH
O
H
R1
I
I
Me
Me
R1
S O
R1
[B]
R1
HI
O
(Me)2S
R2
H
O
R2
OH
R1
O
O
-HI
OH
O
O
O
H
I
O
H
[Ox]
R1
O
R1
R1
[C]
R2
O
OH
O
O
Scheme 2
R1
3

Tetrahedron
3
ACCEPTED MANUSCRIPT
The mechanism of the reaction is similar to that reported by
Shafiee et. al, but here DMSO, the solvent, involved as an
excellent oxidizing agent in the reaction process to produce
the desired product.14 Hence, first the biscoumarin [A] forms
from the reaction of 4-hydroxycoumarin 1 and aldehyde 2 in
the presence of iodine catalyst which undergoes through a
lactone ring opening and decarboxylation process to produce
the intermediate [B] (Scheme 2). The intermediate [B] in the
presence of iodine and DMSO produced the iodinated
compound [C] which after intramolecular cyclization with the
elimination of hydrogen iodide followed by oxidation
produced the aromatized furo[3,2-c]coumarins 3. DMSO
oxidized iodide to iodine and recycles it in the reaction
process.
temperature. Then we studied the reaction by increasing the
load of iodine as well as reaction time and observed that when
50 mol% of iodine was used in the reaction process, the
reactants were consumed completely to give exclusively one
product in excellent yield in 4 h time. Very interestingly, the
product was identified as furo[3,2-c]coumarin derivative 5a
(R1 = H, R2 = Ph) instead of the expected dihydrofuro[3,2-
c]coumarins 6 (R1 = H, R2 = Ph), from the spectroscopic data
and elemental analysis. Subsequently, a large number of
furo[3,2-c]coumarin derivatives 5a-r were synthesized by
utilizing various coumarins 1 with ketones 4, which were
isolated by simple filtration and characterized (Table 2). As in
the earlier case, it was observed that electron withdrawing
group at the benzene ring of the coumarin molecule as well as
in the aromatic ring of the aryl aldehydes produced better
yield of the product in shorter reaction time in comparison to
the electron donating group (Table 2). On the other hand,
under identical reaction conditions aliphatic ketones did not
take part in the reaction process to produce either the furo[3,2-
c]coumarins or dihydrofuro[3,2-c]coumarins of the types 5 or
6 respectively.
To expand the scope of the reaction, various ketones 4 were
utilized with 4-hydroxycoumarins 1 to synthesize more
functionnalized furo[3,2-c]coumarins. Accordingly, 4-
hydroxycoumarin 1 (R1 = H) was first reacted with
acetophenone 4 (R2 = Ph) under the standard reaction
conditions in the presence of iodine as catalyst (7 mol%) in
o
DMSO at 80 C (Scheme 1). A thin layer chromatographic
study showed the slow consumption of the reactants and
formation of a new compound, but the reaction did not
proceed further on increasing the reaction time as well as the
Mechanism for the formation of furo[3,2-c]coumarins 5a
O
O
O
O
+H2O
-H2O
DMSO
I2
OH
OH
Ph CH3
4a
Ph CHO
[D]
Ph
Ph CH2I
Table 2: Synthesis of furo[3,2-c]coumarins 5
O
O
R2
O
O
O
O
CH3
R2
I2, DMSO
I2
O
O
OH
O
O
OH
O
HO
80 oC, 4-5 h
O
R1
Ph
-H2O
Ph
O
R1
O
H
R1
5
4
1
O
[D]
OH
O
Ent.
1
R1
R2
Pd. R.T.
Yd. (%)
78
1a
H
C6H5
C6H5
C6H5
5h
5h
4h
5h
5h
4h
4h
4h
4h
5h
5h
4h
4h
4h
5a
5b
5c
5d
5e
5f
Ph
O
O
Ph
O
O
O
O
2
Me
Cl
H
72
O
O
O
O
OH
HO
3
81
HO
O
4
p-MeC6H4
p-MeC6H4
p-MeC6H4
p-ClC6H4
p-ClC6H4
p-ClC6H4
73
[E]
[F]
1a
5
Me
Cl
H
70
O
O
Ph
O
6
79
O
O
7
78
5g
5h
5i
HO
Scheme 3
5a
8
Me
Cl
H
77
9
89
A reasonable mechanism of the reaction is depicted in the
scheme 3, taking the formation of 5a as an example. The
reaction occurred via initial formation of phenylglyoxal [D]
from phenyl methyl ketone 4a (Ar = Ph) via sp3-CH
activation followed by oxidation19 which reacts with 4-
hydroxycoumarin 1a (R1 = H) in the presence of iodine to
give the intermediate [E] by eliminating water molecule. The
intermediate [E] then suffers a nucleophilic attack by second
molecule of 4-hydroxycoumarin 1a (R1 = H) to give the bis-4-
hydroxycoumarin [F] which finally produced the product 5a
following the reaction path as discussed in the scheme 2. The
mechanism of the reaction was established by performing
reaction of 4-hydroxycoumarin 1 (R1 = H) with commercially
available phenyl glyoxal [D] in the presence of iodine as
catalyst in DMSO at 80 °C for 2 h (till completion of reaction
checked by TLC) which afforded the product 5a in high yield.
10
11
12
13
14
p-OMeC6H4
p-OMeC6H4
p-OMeC6H4
p-BrC6H4
71
5j
Me
Cl
H
70
5k
5l
77
80
5m
5n
Me
p-BrC6H4
78
86
15
16
17
18
Cl
H
p-BrC6H4
C4H4S
5h
5h
5h
5h
5o
5p
5q
5r
74
71
79
Me
Cl
C4H4S
C4H4S
Ent. = Entry, Pd = Product, R.T. = Reaction time, Yd. = Yield

4
Tetrahedron
ACCEPTED MANUSCRIPT
205 oC)14; 1H NMR (500 MHz, CDCl3): δ 6.72-8.16 (m, 13H),
3. Conclusion
11.63 (s, 1H); 13C NMR (125 MHz, CDCl3): 111.8, 117.1,
117.7, 119.4, 122.3, 123.3, 126.0, 126.1 (2C), 126.5, 127.8,
130.3 (2C), 131.9, 132.0, 133.0, 135.2, 138.1, 153.4, 157.3,
157.6, 160.0, 163.6, 186.2; IR (KBr) νmax: 3343.3, 1766.1,
1625.8 cm-1; MS (ESI): 383.2 (M + H)+.
In conclusion, we have developed a very simple and efficient
method for the synthesis of highly functionalized furo[3,2-c]-
coumarin from 4-hydroxycoumarins and aldehydes/aryl
methyl ketones mediated by iodine in DMSO. DMSO acts as
solvent as well as oxidizing agent and recycles the iodine in
the reaction process. The reaction conditions are moderate,
work-up procedure is very simple and products were isolated
in high yield simply by filtration.
2-(2-Hydroxybenzoyl)-3-(p-tolyl)-4H-furo[3,2-c]chromen-4-
one (3d). Yield = 73% (289 mg); Light yellow solid; Rf
o
1
(Hexane/EtOAc, 8:2) 0.52; mp = 110-111 C; H NMR (500
MHz, CDCl3): δ 2.30 (s, 3H), 6.68-7.94 (m, 12H), 11.59 (s,
1H); 13C NMR (125 MHz, CDCl3): 21.3, 111.8, 112.5, 118.8,
118.9, 120.2, 121.1, 123.8, 124.2, 126.4 (2C), 130.7, 130.8,
131.4 (2C), 131.6, 132.6, 132.8, 136.6, 148.6, 151.8, 155.6,
157.3, 161.2, 185.4; IR (KBr) νmax: 3442.2, 1758.4, 1632.7
cm-1; MS (ESI): 397.1 (M + H)+; Anal. Calcd. for C25H16O5:
C, 75.75; H, 4.07%. Found: C, 75.60; H, 4.10%.
4. Experimental Section
All chemicals were purchased from Merck and Aldrich chemical
companies. The reagents and solvents were used without drying.
The IR spectra were recorded on Perkin Elmer system 2000 FTIR
spectrometer. H NMR and 13C NMR Spectra were recorded
1
on Bruker AV500 Avance – III 500 MHz and 125 MHz FT
NMR in DMSO-d6 and CDCl3 using TMS as an internal
standard. Chemical shifts (δ units) are given from TMS (0
ppm). Chemical shifts for DMSO-d6 were reported at 3.36,
2.50 ppm respectively (δ units). Mass spectra were recorded in
Bruker Daltonics ESQUIRE 3000 LC ESI ion trap mass
spectrometer. Analytical thin layer chromatography (TLC) was
performed using E-Merck aluminium-backed silica gel plates
coated with 0.2 mm thickness of silica gel. Melting points
(uncorrected) were determined in open capillary tubes on a Buchi
B-540 apparatus. Elemental analyses were performed on Perkin-
Elmer 2400 spectrometer at the Analytical Chemistry Division,
CSIR-NEIST, Jorhat.
2-(2-Hydroxy-benzoyl)-3-(3-nitro-phenyl)-furo[3,2-c]chro-
men-4-one (3e). Yield = 89% (380 mg); Yellow solid; Rf
o
1
(Hexane/EtOAc, 8:2) 0.48; mp = 79-81 C; H NMR (500
MHz, CDCl3): 6.89-8.47 (m, 12H), 11.52 (s, 1H); 13C NMR
(125 MHz, CDCl3): 108.9, 110.1, 117.6, 118.4, 118.7, 119.1,
121.7, 123.9, 125.0, 125.4, 127.5, 127.9, 128.9, 131.5, 132.9,
136.1, 137.1, 139.8, 153.2, 157.0, 157.9, 160.1, 163.3, 186.2;
IR (KBr) νmax= 3437.1, 1762.7, 1636.2 cm-1; MS (EI): 428.5
(M+H)+; Anal. Calcd. For C24H13NO7: C, 67.45; H, 3.07 %.
Found: C, 67.30; H, 2.90 %.
3-(4-Bromophenyl)-2-(2-hydroxybenzoyl)-4H-furo[3,2-c]-
chromen-4-one (3f). Yield = 79% (364 mg); Yellow solid; Rf
o
1
(Hexane/EtOAc, 8:2) 0.50; mp = 114-115 C; H NMR (500
MHz, CDCl3): δ 6.72-7.98 (m, 12H), 11.49 (s, 1H); 13C NMR
(125 MHz, CDCl3): 111.3, 116.6, 118.7, 119.4, 121.9, 123.7,
126.9, 128.0, 130.7, 131.2 (2C), 131.5, 131.7 (2C), 131.8,
133.1, 134.6, 136.9, 146.3, 151.7, 155.0, 155.1, 160.1, 186.7;
IR (KBr) νmax: 3446.2, 1769.8, 1634.7 cm-1; MS (ESI): 462.4
(M + H)+; Anal. Calcd. for C24H13BrO5: C, 62.49; H, 2.84%.
Found: C, 62.61; H, 2.86%.
General procedure for the synthesis of compound 3:
A mixture of 4-hydroxycoumarin (2 mmol), aldehyde (1
mmol), I2 (7 mol%) were taken in round bottomed flask
containing 5 ml of DMSO. Then the reaction mixture was
allowed to heat at 80 °C for 1-1.5 h (till completion of
reaction checked by TLC). After completion of the reaction,
the mixture was cooled to room temperature and poured into
water. Then the iodine was neutralized by adding sodium
thiosulphate (5 mL of 5% solution) into the reaction mixture.
The crude product 3 was obtained by simple filtration and
purified by recrystallization from ethanol.
3-(4-Chlorophenyl)-2-(2-hydroxybenzoyl)-4H-furo[3,2-c]-
chromen-4-one (3g). Yield = 80% (332 mg); Yellow solid;
o
1
Rf (Hexane/EtOAc, 8:2) 0.49; mp = 212-213 C; H NMR
(500 MHz, CDCl3): δ 6.86-8.03 (m, 12H), 11.37 (s, 1H); 13C
NMR (125 MHz, CDCl3): 111.2, 112.6, 118.6, 118.9, 120.2,
121.1, 123.3, 124.2, 126.3, 130.6 (2C), 130.9, 131.5 (2C),
131.8, 132.6, 132.8, 136.6, 151.6, 155.3, 157.4, 161.2, 163.5,
186.7; IR (KBr) νmax: 3428.5, 1746.3, 1622.8 cm-1; MS (ESI):
417.5 (M + H)+; Anal. Calcd. for C24H13ClO5: C, 69.16; H,
3.14%. Found: C, 69.33; H, 3.17 %.
2-(2-Hydroxybenzoyl)-4H-furo[3,2-c]chromen-4-one
(3a).
Yield = 78% (238 mg); Yellow solid; Rf (Hexane/EtOAc,
8:2) 0.50; mp = 153-154 oC (reported 154-156 oC)14; 1H NMR
(500 MHz, CDCl3): δ 7.22-8.04 (m, 9H), 11.32 (s, 1H); 13C
NMR (125 MHz, CDCl3): 110.0, 111.3, 117.1, 118.0, 118.1,
118.5, 121.5, 127.8, 129.9, 131.2, 135.0, 136.1, 151.9, 153.0,
158.1, 161.0, 163.9, 184.4; IR (KBr) νmax: 3436.2, 1765.4,
1628.5 cm-1; MS (ESI): 307.2 (M + H)+.
8-Chloro-2-(3-chloro-2-hydroxybenzoyl)-3-phenyl-4H-furo-
[3,2-c]chromen-4-one (3h). Yield = 79% (356 mg); Light
yellow solid; Rf (Hexane/EtOAc, 8:2) 0.57; mp = 155-157 oC;
1H NMR (500 MHz, CDCl3): δ 6.96-8.05 (m, 11H), 11.39 (s,
1H); 13C NMR (125 MHz, CDCl3): 111.2, 112.5, 118.8,
118.9, 120.0, 121.1, 123.8, 124.2, 126.3, 130.7, 130.8 (2C),
131.3, 131.6 (2C), 132.7, 132.9, 136.9, 151.8, 155.6, 157.4,
161.5, 163.5, 184.3; IR (KBr) νmax: 3342.6, 1767.5, 1623.6
cm-1; MS (ESI): 452.6 (M + H)+; Anal. Calcd. for
C24H12Cl2O5: C, 63.88; H, 2.68%. Found: C, 63.76; H, 2.67%.
2-(2-Hydroxybenzoyl)-3-methyl-4H-furo[3,2-c]chromen-4-
one (3b). Yield = 72% (230 mg); Yellow solid; Rf
o
(Hexane/EtOAc, 8:2) 0.60; mp = 217-219 C (reported 216-
o
1
218 C)14; H NMR (500 MHz, CDCl3): δ 2.79 (s, 3H), 7.01-
8.27 (m, 8H), 12.05 (s, 1H); 13C NMR (125 MHz, CDCl3):
10.8, 111.9, 117.9, 118.6, 119.0, 121.5, 122.0, 122.6, 123.9,
124.2, 130.1, 130.9, 133.1, 148.3, 153.8, 157.3, 157.6, 163.6,
186.7; IR (KBr) νmax: 3382.7, 1762.2, 1626.5 cm-1; MS (ESI):
321.4 (M + H)+.
8-Chloro-2-(3-chloro-2-hydroxybenzoyl)-3-(p-tolyl)-4H-furo-
[3,2-c]chromen-4-one (3i). Yield = 77% (358 mg); Light
yellow solid; Rf (Hexane/EtOAc, 8:2) 0.62; mp = 104-105 oC;
1H NMR (500 MHz, CDCl3): δ 2.42 (s, 3H), 6.82-8.03 (m,
2-(2-Hydroxybenzoyl)-3-phenyl-4H-furo[3,2-c]chromen-4-
one (3c). Yield = 74% (282 mg); Yellow solid; Rf
o
(Hexane/EtOAc, 8:2) 0.50; mp = 203-204 C (reported 203-

Tetrahedron
5
ACCEPTED MANUSCRIPT
10H), 11.42 (s, 1H); 13C NMR (125 MHz, CDCl3): 21.5,
111.0, 112.6, 118.6, 118.8, 120.0, 121.2, 123.9, 124.1, 126.3
(2C), 130.7, 130.9, 131.3 (2C), 131.6, 132.5, 132.8, 136.6,
3-Benzoyl-2-(2-hydroxybenzoyl)-4H-furo[3,2-c]chromen-4-
one (5a). Yield = 78% (319 mg); Yellow crystalline solid; Rf
o
1
(Hexane/EtOAc, 8:2) 0.47; mp = 286-287 C; H NMR (500
MHz, DMSO-d6): δ 6.89-8.03 (m, 13H), 10.51 (s, 1H); 13C
NMR (125 MHz, DMSO-d6): 113.2, 118.3, 118.9, 119.8,
121.3, 122.9, 125.4, 128.6, 129.0, 129.1 (2C), 129.3 (2C),
129.4, 129.6, 133.1, 133.8, 134.7, 150.0, 152.3, 155.7, 156.0,
157.3, 181.7, 187.9; IR (KBr) νmax: 3435.6, 2926.3, 1750.5,
1674.7 cm-1; MS (ESI): 411.4 (M +H )+; Anal. Calcd. for
C25H14O6: C, 73.17; H, 3.44%. Found: C, 72.99; H, 3.47%.
151.8, 155.7, 157.5, 161.5, 164.0, 185.4; IR (KBr) νmax
:
3441.8, 1768.2, 1627.7 cm-1; MS (ESI): 466.1 (M + H)+;
Anal. Calcd. for C25H14Cl2O5: C, 64.54; H, 3.03%. Found: C,
64.37; H, 2.99%.
3-(4-Bromophenyl)-8-chloro-2-(3-chloro-2-hydroxybenzoyl)-
4H-furo[3,2-c]chromen-4-one (3j). Yield = 86% (455 mg);
Light yellow solid; Rf (Hexane/EtOAc, 8:2) 0.55; mp = 200-
o
1
202 C; H NMR (500 MHz, CDCl3): δ 6.82-7.99 (m, 10H),
11.37 (s, 1H); 13C NMR (125 MHz, CDCl3): 111.0, 112.6,
118.8, 118.9, 120.0, 121.1, 123.9, 124.2, 126.3, 130.7, 130.8,
131.4 (2C), 131.6 (2C), 132.6, 132.8, 136.8, 151.9, 155.7,
157.5, 161.6, 164.0, 185.4; IR (KBr) νmax: 3365.7, 1769.0.
1628.5 cm-1; MS (ESI): 531.3 (M + H)+; Anal. Calcd. for
C24H11BrCl2O5: C, 54.37; H, 2.09%. Found: C, 54.21; H,
2.12%.
3-Benzoyl-2-(2-hydroxy-5-methylbenzoyl)-8-methyl-4H-furo-
[3,2-c]chromen-4-one (5b). Yield = 72% (315 mg); Orange
o
1
solid; Rf (Hexane/EtOAc, 8:2) 0.49; mp = 268-269 C; H
NMR (500 MHz, DMSO-d6): δ 2.15 (s, 3H), 2.43 (s, 3H),
6.86-7.97 (m, 11H), 10.18 (s, 1H); 13C NMR (125 MHz,
DMSO-d6): 20.1, 20.7, 110.9, 111.5, 116.9, 117.5, 121.6,
123.5, 128.1, 128.4, 129.3 (2C), 130.1, 131.2 (2C), 134.4,
134.8, 135.3, 135.4, 139.6, 150.1, 152.0, 155.9, 157.7, 158.6,
183.2, 188.3; IR (KBr) νmax: 3521.3, 2922.1, 1751.2, 1681.8
cm-1; MS (ESI): 439.5 (M + H)+; Anal. Calcd. for C27H18O6:
C, 73.97; H, 4.14%. Found: C, 73.78; H, 4.12%.
8-Chloro-2-(3-chloro-2-hydroxybenzoyl)-3-(4-chlorophenyl)-
4H-furo[3,2-c]chromen-4-one (3k). Yield = 88% (426 mg);
Light yellow solid; Rf (Hexane/EtOAc, 8:2) 0.48; mp = 201-
o
1
202 C; H NMR (500 MHz, CDCl3): δ 6.84-8.36 (m, 10H),
11.31 (s, 1H); 13C NMR (125 MHz, CDCl3): 111.0, 112.5,
118.6, 118.7, 120.0, 121.3, 123.9, 124.1, 126.3, 130.8 (2C),
130.9, 131.3 (2C), 131.6, 132.5, 132.8, 136.6, 148.6, 151.8,
155.6, 157.5, 161.6, 185.3; IR (KBr) νmax: 3443.2, 1766.7,
1624.5 cm-1; MS (ESI): 486.3 (M + H)+; Anal. Calcd. for
C24H11Cl3O5: C, 59.35; H, 2.28%. Found: C, 59.54; H, 2.25%.
3-Benzoyl-8-chloro-2-(5-chloro-2-hydroxybenzoyl)-4H-furo-
[3,2-c]chromen-4-one (5c). Yield = 81% (387 mg); Light
orange solid; Rf (Hexane/EtOAc, 8:2) 0.46; mp = 257-259 oC;
1H NMR (500 MHz, DMSO-d6): δ 6.91-8.08 (m, 11H), 10.64
(s, 1H); 13C NMR (125 MHz, DMSO-d6): 111.0, 111.7, 117.9,
119.4, 122.2, 125.5, 125.8, 125.9, 129.4 (2C), 130.1, 131.2
(2C), 131.3, 133.9, 134.4, 138.5, 140.0, 148.9, 150.2, 153.8,
156.0, 159.1, 180.9, 186.8; IR (KBr) νmax: 3446.9, 2916.6,
1763.2, 1670.6 cm-1; MS (ESI): 480.3 (M + H)+; Anal. Calcd.
for C25H12Cl2O6: C, 62.65; H, 2.52%. Found: C, 62.80; H,
2.50%.
2-(2-Hydroxy-3-methylbenzoyl)-8-methyl-4H-furo[3,2-c]chro-
men-4-one (3l). Yield = 74% (247 mg); Light yellow solid; Rf
o
1
(Hexane/EtOAc, 8:2) 0.57; mp = 189-190 C; H NMR (500
MHz, CDCl3): δ 2.39 (s, 3H), 2.50 (s, 3H), 6.97-7.96 (m, 7H),
11.45 (s, 1H); 13C NMR (125 MHz, CDCl3): 20.6, 20.8,
110.1, 111.4, 117.3, 118.0, 118.1, 118.5, 121.5, 128.6, 130.2,
133.7, 135.0, 138.0, 152.2, 154.1, 157.9, 159.1, 162.0, 184.4;
IR (KBr) νmax: 3343.8, 1766.9, 1626.8 cm-1; MS (ESI): 335.4
(M + H)+; Anal. Calcd. for C20H14O5: C, 71.85; H, 4.22%.
Found: C, 71.67; H, 4.24%.
2-(2-Hydroxybenzoyl)-3-(4-methylbenzoyl)-4H-furo[3,2-c]-
chromen-4-one (5d). Yield = 73% (309 mg); Orange solid; Rf
o
1
(Hexane/EtOAc, 8:2) 0.48; mp = 245-246 C; H NMR (500
MHz, DMSO-d6): δ 2.44 (s, 3H), 6.86-8.16 (m, 12H), 10.51
(s, 1H); 13C NMR (125 MHz, DMSO-d6): 21.6, 111.7, 113.2,
118.8, 119.8, 121.3, 123.0, 125.4, 129.2, 129.3 (2C), 129.5
(2C), 129.6, 129.7, 133.1, 133.6, 133.7, 145.5, 149.9, 152.3,
155.7, 155.9, 157.3, 181.7, 187.3; IR (KBr) νmax: 3435.1,
2927.7, 1751.3, 1674.8 cm-1; MS (ESI): 425.6 (M + H)+;
Anal. Calcd. for C26H16O6: C, 73.58; H, 3.80%. Found: C,
73.41; H, 3.83%.
2-(2-Hydroxy-3-methylbenzoyl)-8-methyl-3-phenyl-4H-furo-
[3,2-c]chromen-4-one (3m). Yield = 72% (295 mg); Light
yellow solid; Rf (Hexane/EtOAc, 8:2) 0.58; mp = 194-195 oC;
1H NMR (500 MHz, CDCl3): δ 2.42 (s, 3H), 2.58 (s, 3H),
6.72-8.16 (m, 11H), 11.32 (s, 1H); 13C NMR (125 MHz,
CDCl3): 20.0, 21.5, 111.9, 117.0, 117.8, 119.2, 122.3, 123.2,
126.0 (2C), 126.1, 126.5, 127.8 (2C), 130.3, 131.9, 132.0,
133.0, 135.2, 138.1, 152.2, 154.1, 157.9, 159.1, 162.1, 185.2;
IR (KBr) νmax: 3367.8, 1765.9, 1629.5 cm-1; MS (ESI): 411.7
(M + H)+; Anal. Calcd. for C26H18O5: C, 76.09; H, 4.42%.
Found: C, 75.94; H, 4.43%.
2-(2-Hydroxy-5-methylbenzoyl)-8-methyl-3-(4-methylben-
zoyl)-4H-furo[3,2-c]chromen-4-one (5e). Yield = 70% (316
mg); Orange solid; Rf (Hexane/EtOAc, 8:2) 0.51; mp = 293-
o
1
295 C; H NMR (500 MHz, DMSO-d6): δ 2.07 (s, 3H), 2.12
(s, 3H), 2.42 (s, 3H), 6.52-7.79 (m, 10H), 10.19 (s, 1H); 13C
NMR (125 MHz, DMSO-d6): 20.0, 20.6, 21.0, 110.8, 111.5,
116.9, 117.5, 121.6, 123.5, 128.1, 128.4, 129.3 (2C), 130.1,
131.2 (2C), 134.4, 134.8, 135.3, 135.4, 139.6, 150.3, 151.9,
155.4, 157.2, 161.0, 183.2, 187.1; IR (KBr) νmax: 3435.5,
2927.4, 1745.4, 1669.8 cm-1; MS (ESI): 453.6 (M + H)+;
Anal. Calcd. for C28H20O6: C, 74.33; H, 4.46%. Found: C,
74.55; H, 4.43%.
General procedure for the synthesis of compound 5:
A mixture of 4-hydroxycoumarin (2 mmol), aryl methyl
ketone (1 mmol), I2 (50 mol%) were taken in round bottomed
flask containing 5 ml of DMSO. Then the reaction mixture
was allowed to heat at 80 °C for 4-5 h (till completion of
reaction checked by TLC). After completion of the reaction,
the mixture was cooled to room temperature and poured into
water. Then the iodine was neutralized by adding sodium
thiosulphate (10 mL of 5% solution) into the reaction mixture.
The product 5 was isolated by filtration and recrystallized
from ethanol.
8-Chloro-2-(5-chloro-2-hydroxybenzoyl)-3-(4-methylbenzo-
yl)-4H-furo[3,2-c]chromen-4-one (5f). Yield = 79% (389
mg); Orange solid; Rf (Hexane/EtOAc, 8:2) 0.49; mp = 275-
276 oC; 1H NMR (500 MHz, DMSO-d6): δ 2.40 (s, 3H), 6.90-
8.13 (m, 10H), 10.62 (s, 1H); 13C NMR (125 MHz, DMSO-

6
Tetrahedron
ACCEPTED MANUSCRIPT
d6): 21.3, 110.9, 111.8, 117.1, 117.7, 119.4, 122.3, 123.3,
125.7, 129.0, 129.1 (2C), 129.5 (2C), 130.6, 133.5, 134.6,
134.9, 136.0, 150.1, 153.7, 156.1, 158.1, 158.4, 183.3, 188.3;
IR (KBr) νmax: 3411.2, 2928.1, 1749.7, 1694.2 cm-1; MS
(ESI): 494.4 (M + H)+; Anal. Calcd. for C26H14Cl2O6: C,
63.31; H, 2.86%. Found: C, 63.16; H, 2.87%.
Anal. Calcd. for C28H20O7: C, 71.79; H, 4.30%. Found: C,
71.98; H, 4.34%.
8-Chloro-2-(5-chloro-2-hydroxybenzoyl)-3-(4-methoxybenzo-
yl)-4H-furo[3,2-c]chromen-4-one (5l). Yield = 77% (391
mg); Yellow solid; Rf (Hexane/EtOAc, 8:2) 0.47; mp = 215-
216 oC; 1H NMR (500 MHz, DMSO-d6): δ 3.85 (s, 3H), 6.89-
8.06 (m, 10H), 10.62 (s, 1H); 13C NMR (125 MHz, DMSO-
d6): 56.0, 113.2, 114.4, 114.5, 118.7, 119.8, 121.3, 121.5,
122.9 (2C), 125.5, 129.1, 129.2, 129.4, 129.6, 131.9, 133.0
(2C), 133.9, 155.7, 155.9, 157.3, 164.5, 164.6, 181.8, 186.0;
IR (KBr) νmax: 3457.2, 2976.4, 1739.8, 1673.3 cm-1; MS
(ESI): 510.3 (M + H)+; Anal. Calcd. for C26H14Cl2O7: C,
61.32; H, 2.77%. Found: C, 61.16; H, 2.75%.
3-(4-Chlorobenzoyl)-2-(2-hydroxybenzoyl)-4H-furo[3,2-c]-
chromen-4-one (5g). Yield = 78% (346 mg); Yellow solid; Rf
o
1
(Hexane/EtOAc, 8:2) 0.45; mp = 230-231 C; H NMR (500
MHz, DMSO-d6): δ 6.70-8.25 (m, 12H), 10.80 (s, 1H); 13C
NMR (125 MHz, DMSO-d6): 109.2, 111.5, 113.2, 119.8,
121.3, 129.3 (2C), 129.4, 129.7, 129.8, 131.2 (2C), 131.3,
133.0, 134.7, 139.7, 142.3, 145.0, 152.2, 155.7, 158.0, 160.0,
160.4, 181.4, 186.8; IR (KBr) νmax: 3501.4, 2924.3, 1759.2,
1676.3 cm-1; MS (ESI): 445.9 (M + H)+; Anal. Calcd. for
C25H13ClO6: C, 67.50; H, 2.95%. Found: C, 67.36; H, 2.93%.
3-(4-Bromobenzoyl)-2-(2-hydroxybenzoyl)-4H-furo[3,2-c]-
chromen-4-one (5m). Yield = 80% (391 mg); Orange solid;
o
1
Rf (Hexane/EtOAc, 8:2) 0.44; mp = 233-235 C; H NMR
(500 MHz, DMSO-d6): δ 6.25-8.17 (m, 12H), 10.49 (s, 1H);
13C NMR (125 MHz, DMSO-d6): 114.5, 118.7, 119.8, 121.3,
121.5, 122.9 (2C), 125.5 (2C), 129.1, 129.2, 129.4, 129.6,
129.9, 131.9, 133.1, 133.2, 133.6, 155.7, 155.9, 157.3, 164.5,
164.6, 181.7, 186.0; IR (KBr) νmax: 3509.6, 2936.9, 1763.8,
1669.7 cm-1; MS (ESI): 490.4 (M + H)+; Anal. Calcd. for
C25H13BrO6: C, 61.37; H, 2.68%. Found: C, 61.23; H, 2.71%.
3-(4-Chlorobenzoyl)-2-(2-hydroxy-5-methylbenzoyl)-8-meth-
yl -4H-furo[3,2-c]chromen-4-one (5h). Yield = 77% (363
mg); Orange solid; Rf (Hexane/EtOAc, 8:2) 0.46; mp = 282-
o
1
283 C; H NMR (500 MHz, DMSO-d6): δ 2.11 (s, 3H), 2.47
(s, 3H), 6.80-7.87 (m, 10H), 10.14 (s, 1H); 13C NMR (125
MHz, DMSO-d6): 20.0, 20.6, 110.7, 111.5, 116.9, 117.5,
121.5, 123.4, 128.1, 128.4, 129.3, 130.1 (2C), 131.2 (2C),
134.4, 134.8, 135.3, 135.4, 139.6, 151.9, 154.3, 155.2, 158.9,
160.2, 183.3, 188.2; IR (KBr) νmax: 3435.7, 2927.7, 1753.2,
1676.3 cm-1; MS (ESI): 473.9 (M + H)+; Anal. Calcd. for
C27H17ClO6: C, 68.58; H, 3.62%. Found: C, 68.79; H, 3.65%.
3-(4-Bromobenzoyl)-2-(2-hydroxy-5-methylbenzoyl)-8-
methyl-4H-furo[3,2-c]chromen-4-one (5n). Yield = 78% (403
mg); Orange solid; Rf (Hexane/EtOAc, 8:2) 0.45; mp = 245-
o
1
246 C; H NMR (500 MHz, DMSO-d6): δ 2.12 (s, 3H), 2.43
(s, 3H), 6.50-7.79 (m, 10H), 10.12 (s, 1H); 13C NMR (125
MHz, DMSO-d6): 20.1, 20.9, 114.5, 118.7, 119.8, 121.3,
121.5, 122.9 (2C), 125.5, 129.1, 129.2, 129.4, 129.6, 129.9,
131.9 (2C), 133.1, 133.2, 133.7, 155.7, 155.9, 157.3, 164.5,
164.6, 181.8, 186.0; IR (KBr) νmax: 3516.2, 2924.7, 1773.4,
1662.9 cm-1; MS (ESI): 518.2 (M + H)+; Anal. Calcd. for
C27H17BrO6: C, 62.69; H, 3.31%. Found: C, 62.52; H, 3.33%.
8-Chloro-2-(5-chloro-2-hydroxybenzoyl)-3-(4-chloroben-
zoyl)-4H-furo[3,2-c]chromen-4-one (5i). Yield = 89% (456
mg); Orange solid; Rf (Hexane/EtOAc, 8:2) 0.42; mp=225-
o
1
227 C; H NMR (500 MHz, DMSO-d6): δ 6.90-8.13 (m,
10H), 10.62 (s, 1H); 13C NMR (125 MHz, DMSO-d6): 110.9,
111.8, 114.4, 117.1, 117.7, 119.4 (2C), 122.3, 123.4, 125.7,
129.3 (2C), 130.5, 131.9, 133.3, 134.8, 137.2, 149.8, 153.6,
156.1, 158.1, 158.3, 164.4, 183.2, 186.5; IR (KBr) νmax
:
3-(4-Bromobenzoyl)-8-chloro-2-(5-chloro-2-hydroxybenzoyl)-
4H-furo[3,2-c]chromen-4-one (5o). Yield = 86% (479 mg);
Light orange solid; Rf (Hexane/EtOAc, 8:2) 0.40; mp = 262-
264 C; H NMR (500 MHz, DMSO-d6): δ 6.89-8.37 (m,
10H), 10.62 (s, 1H); 13C NMR (125 MHz, DMSO-d6): 110.7,
111.5, 114.4, 114.5, 116.9, 117.5, 121.5, 121.8, 123.5 (2C),
129.0, 129.1, 129.3, 131.3 (2C), 131.9, 132.0, 135.2, 150.0,
3435.7, 2991.9, 1771.3, 1682.3 cm-1; MS (ESI): 514.6 (M +
H)+; Anal. Calcd. for C25H11Cl3O6: C, 58.45; H, 2.16%.
Found: C, 58.28; H, 2.13%.
o
1
2-(2-Hydroxybenzoyl)-3-(4-methoxybenzoyl)-4H-furo[3,2-c]-
chromen-4-one (5j). Yield = 71% (312 mg); Light yellow
o
1
solid; Rf (Hexane/EtOAc, 8:2) 0.47; mp = 272-273 C; H
NMR (500 MHz, DMSO-d6): δ 3.85 (s, 3H), 6.86-8.06 (m,
12H), 10.48 (s, 1H); 13C NMR (125 MHz, DMSO-d6): 56.0,
110.9, 111.9, 114.4, 117.1, 117.7, 119.4, 122.3 (2C), 123.4,
125.7, 129.3, 130.5, 131.9 (2C), 133.4, 134.8, 137.1, 149.9,
152.0, 155.6, 164.3, 164.4, 186.3, 186.4; IR (KBr) νmax
:
3473.8, 2982.6, 1764.5, 1679.7 cm-1; MS (ESI): 559.3 (M +
H)+; Anal. Calcd. for C25H11BrCl2O6: C, 53.80; H, 1.99%.
Found: C, 53.65; H, 1.97%.
153.7, 156.1, 158.1, 158.3, 164.3, 183.3, 186.5; IR (KBr) νmax
:
2-(2-Hydroxybenzoyl)-3-(thiophene-2-carbonyl)-4H-furo[3,2-
3439.1, 2970.4, 1755.7, 1673.6 cm-1; MS (ESI): 441.2 (M +
H)+; Anal. Calcd. for C26H16O7: C, 70.91; H, 3.66%. Found:
C, 70.75; H, 3.64%.
c]chromen-4-one (5p). Yield = 74% (307 mg); Light yellow
o
1
solid; Rf (Hexane/EtOAc, 8:2) 0.30; mp = 244-245 C; H
NMR (500 MHz, DMSO-d6): δ 7.71-8.95 (m, 11H), 11.35 (s,
1H); 13C NMR (125 MHz, DMSO-d6): 114.4, 114.5, 118.7,
119.8, 121.3 (2C), 121.5, 122.9, 125.5 (2C), 129.1, 129.2,
129.4, 129.6, 131.9, 133.0, 155.6, 155.9, 157.3, 164.5, 164.6,
181.8, 186.1; IR (KBr) νmax: 3513.7, 2978.5, 1768.3, 1673.1
cm-1; MS (ESI): 417.6 (M + H)+; Anal. Calcd. for C23H12O6S:
C, 66.34; H, 2.90%. Found: C, 66.54; H, 2.93%.
2-(2-Hydroxy-5-methylbenzoyl)-3-(4-methoxybenzoyl)-8-
methyl-4H-furo[3,2-c]chromen-4-one (5k). Yield = 70% (327
mg); Orange solid; Rf (Hexane/EtOAc, 8:2) 0.50; mp = 224-
o
1
226 C; H NMR (500 MHz, DMSO-d6): δ 2.15 (s, 3H), 2.48
(s, 3H) 3.86 (s, 3H), 6.81-7.90 (m, 10H), 10.66 (s, 1H); 13C
NMR (125 MHz, DMSO-d6): 20.0, 20.6, 56.0, 110.7, 111.5,
114.2, 117.1, 117.8, 119.2, 122.1, 123.2, 125.6, 129.0 (2C),
130.2, 131.9 (2C), 133.2, 134.9, 137.0, 139.2, 153.8, 156.0,
158.3, 158.9, 164.3, 183.3, 186.8; IR (KBr) νmax: 3441.6,
2967.9, 1743.5, 1682.7 cm-1; MS (ESI): 469.4 (M + H)+;
2-(2-Hydroxy-5-methylbenzoyl)-8-methyl-3-(thiophene-2-
carbonyl)-4H-furo[3,2-c]chromen-4-one (5q). Yield = 71%
(315 mg); Yellow solid; Rf (Hexane/EtOAc, 8:2) 0.33; mp =
o
1
249-250 C; H NMR (500 MHz, DMSO-d6): δ 2.18 (s, 3H)
2.48 (s, 3H) 7.04-8.01 (m, 9H), 10.12 (s, 1H); 13C NMR (125

Tetrahedron
7
ACCEPTED MANUSCRIPT
Lett. 2012, 53, 4343; (c) Hamdi, N.; Purta, M. C.; Valerga, P.;
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MHz, DMSO-d6): 21.6, 21.7, 117.2, 117.7, 119.4, 122.0,
122.3, 123.3, 125.7, 125.8, 129.2, 129.6 (2C), 129.7 (2C),
129.8, 130.6, 131.7, 153.7, 153.8, 156.1, 158.2, 158.4, 183.3,
187.7; IR (KBr) νmax: 3523.8, 2982.6, 1772.9, 1675.8 cm-1;
MS (ESI): 445.2 (M + H)+; Anal. Calcd. for C25H16O6S: C,
67.56; H, 3.63%. Found: C, 67.40; H, 3.66%.
14. Zareai, Z.; Khoobi, M.; Ramazani, A.; Foroumadi, A.;
Souldozi, A.; Slepokura, K.; Lis, T.; Shafiee, A. Tetrahedron
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Vishwakarma, R. A.; Sawant, S. D. Org. Biomol. Chem. 2015,
13, 7973; (b) Yin, G.; Zhou, B.; Meng, X.; Wu, A.; Pan, Y.
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2012, 53, 5034; (b) Majumder, S.; Borah, P.; Bhuyan, P. J.
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8-Chloro-2-(5-chloro-2-hydroxybenzoyl)-3-(thiophene-2-
carbonyl)-4H-furo[3,2-c]chromen-4-one (5r). Yield = 79%
(383 mg); Light yellow solid; Rf (Hexane/EtOAc, 8:2) 0.29;
o
1
mp = 264-265 C; H NMR (500 MHz, DMSO-d6): δ 7.33-
8.10 (m, 9H), 10.61 (s, 1H); 13C NMR (125 MHz, DMSO-d6):
118.9, 119.7, 121.3, 122.9, 125.4, 128.6, 129.0, 129.1 (2C),
129.3 (2C), 129.8, 129.9, 133.1, 133.8, 134.7, 150.0, 152.1,
155.8, 156.1, 157.3, 181.7, 188.0; IR (KBr) νmax: 3531.8,
2976.7, 1781.5, 1677.4 cm-1; MS (ESI): 486.2 (M + H)+;
Anal. Calcd. for C23H10Cl2O6S: C, 56.93; H, 2.08%. Found: C,
56.75; H, 2.10%.
Acknowledgements
We thank DST, New Delhi and CSIR, New Delhi for
financial assistance (CAAF-NE Project).
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