A novel one-pot synthesis of 3-carbomethoxy-4-arylfuran-2-(5H)-ones from ketones using [hydroxy(tosyloxy)iodo]benzene

Article abstract of DOI:10.1016/j.tetlet.2008.05.012

A novel one-pot procedure for the synthesis of 3-carbomethoxy-4-aryl furan-2-(5H)-ones is reported via α-tosyloxylation of enolisable ketones with [hydroxy(tosyloxy)iodo]benzene, followed by treatment with potassium monomethyl malonate and K₂CO₃.

Full text of DOI:10.1016/j.tetlet.2008.05.012

Tetrahedron Letters 49 (2008) 4402–4404
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Tetrahedron Letters
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A novel one-pot synthesis of 3-carbomethoxy-4-arylfuran-2-(5H)-ones
from ketones using [hydroxy(tosyloxy)iodo]benzene
*
Nandkishor N. Karade , Sumeet V. Gampawar, Jeevan M. Kondre, Sandeep V. Shinde
School of Chemical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606, Maharashtra, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel one-pot procedure for the synthesis of 3-carbomethoxy-4-aryl furan-2-(5H)-ones is reported via
a-tosyloxylation of enolisable ketones with [hydroxy(tosyloxy)iodo]benzene, followed by treatment with
potassium monomethyl malonate and K2CO3.
Received 19 March 2008
Revised 30 April 2008
Accepted 3 May 2008
Available online 9 May 2008
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords:
Hypervalent iodine
c-Lactone
Potassium monomethyl malonate
Enolisable ketone
Recently, there has been significant growth in the applications
of hypervalent iodine reagents in organic synthesis.1 [Hydro-
xy(tosyloxy)iodo]benzene (HTIB) commonly known as Kosser’s
reagent is the sole efficient reagent for inducing a-tosyloxylation
of enolisable ketones.2 The resulting a-tosyloxyketones are envi-
ronmentally benign alternatives to the toxic and lachrymatory
a-haloketones. Since it is generally not necessary to isolate the
a-tosyloxyketone, they can be utilised in situ as strategic precur-
sors for the one-pot synthesis of a wide range of heterocycles such
as thiazoles, selenazoles, oxazoles, imidazoles, pyrazoles and
benzofurans.3
The c-butenolide structural subunit is present in a growing
number of natural products and synthetic compounds with wide-
ranging biological properties.4 This biological importance of c-but-
enolides has prompted the development of a plethora of methods
for their synthesis.5 The preparation of c-lactones is achieved
mainly by the halo- or seleno-lactonisation reactions of b,c- and
c,d-unsaturated carboxylic acids.5a The success of these reactions
is due to the facile halo- and seleno-functionalisation of the car-
bon–carbon double bond followed by neighbouring group partici-
pation of the nucleophilic carboxyl group. As HTIB is known for
the a-tosyloxylation of enolisable ketones2 as well as for vic-dito-
syloxylations of alkenes,6 it can be used safely as an alternative
to halogen or selenium reagents in the lactonisation reactions of
appropriate carboxylic acids. The reactions of b,c- and c,d-unsatu-
rated carboxylic acids7 and 5-oxocarboxylic acids8 with HTIB are
known for the efficient synthesis of c-lactones. In spite of this
excellent intramolecular strategy, precursors such as b,c- and c,d-
unsaturated carboxylic acids and 5-oxocarboxylic acids are poorly
available commercially and therefore, special efforts are required
for their preparation. Recently, Wirth and co-workers reported
the efficient synthesis of c-butenolides from b,c-unsaturated car-
boxylic acids using PhI(OCOCF3)2 and a catalytic quantity of
(PhSe)2 under mild reaction conditions.9 Furthermore, the free rad-
ical-based cyclisation of aliphatic carboxylic and benzoic acids
using a hypervalent iodine(III) reagent and KBr to form c-lactones
was reported by Kita and co-workers10 The above-discussed strat-
egies for c-lactone synthesis are based mainly upon intramolecular
cyclisation of appropriate carboxylic acids.
A literature survey revealed that c-lactones can be synthesised
by the reaction between olefins and b-diketones or b-ketoesters,11
or potassium monomethyl malonate12 using a suitable single elec-
tron oxidant. The mono-potassium salt of dimethyl malonate is a
readily accessible versatile building block possessing doubly
nucleophilic character at the carbon and oxygen centres.13 It has
been used in combination with olefins in presence of Mn(OAc)3
as a single electron oxidant to form c-lactones in reasonably good
yields.12 However, the addition is not regioselective in the case of
unsymmetrical olefins and therefore, side products are formed.12b
In continuation of our interest in hypervalent iodine reagents,14
herein we report a novel one-pot synthesis of 3-carbomethoxy-
4-arylfuran-2-(5H)-ones from enolisable ketones and potassium
monomethyl malonate using HTIB (Scheme 1).
The success of this reaction is due to the facile in situ formation
of a-tosyloxyketones 2 followed by efficient trapping with potas-
sium monomethyl malonate to form methyl 2-oxo-2-arylethyl
malonate 3, which finally undergoes base (K2CO3) catalysed
* Corresponding author. Fax: +91 2462 229245.
E-mail address: nnkarade2007@rediffmail.com (N. N. Karade).
0040-4039/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2008.05.012

N. N. Karade et al. / Tetrahedron Letters 49 (2008) 4402–4404
4403
O
O
O
PhI(OH)OTs, CH3CN
reflux
Ph
COOMe
O
K2CO3 (0.6 equv.)
reflux, 1.5 h
OMe
O
OTs
Ph
Ar
Ar
O
O
1a-j
2
O
3a
4a
COOMe
reflux
Scheme 2.
COOK
Ar
COOMe
K2CO3
reflux
O
Table 2
OMe
O
O
Synthesis of 3,4-disubstituted furan-2-(5H)-ones from various acetophenones
O
Ar
O
O
O
Ar
COOMe
4a-j
(i) PhI(OH)OTs, CH3CN, reflux (1.5 h)
3
Ar
(ii) MeO2CCH2CO2K, reflux (4-5 h)
(iii) K2CO3, reflux (1.5 h)
O
Scheme 1.
O
4
1
Entry
Ar 1
Product
Reaction time (h)
Yielda (%)
cyclisation to form c-butenolides 4. Intermediates 2 and 3 are not
isolated during the reaction.
a
b
c
d
e
f
g
h
i
C6H5–
4a
4b
4c
4d
4e
4f
4g
4h
4i
11
12
14
13
10
13
14
11
13
12
72
76
69
68
67
66
64
69
71
63
4-MeOC6H4–
2-MeOC6H4–
2,4-(MeO)2C6H3–
4-MeC6H4–
4-BrC6H4–
2-BrC6H4–
4-ClC6H4–
2,4-Cl2C6H3–
4-O2NC6H4–
The reaction conditions were optimised by considering the
model reaction of acetophenone and potassium monomethyl mal-
onate using HTIB as oxidant. A mixture of acetophenone (0.360 g,
3 mmol) and HTIB (1.293 g, 3.3 mmol) was refluxed in CH3CN for
1.5 h with TLC monitoring of the reaction. After the successful
formation of a-tosyloxyacetophenone 2, potassium monomethyl
malonate (0.468 g, 3 mmol) was added and the reaction mixture
was refluxed (5 h) until complete consumption of 2 had occurred.
Finally, K2CO3 (0.248 g, 1.8 mmol) was added and the reaction
mixture was refluxed for 1.5 h to afford methyl 2,5-dihydro-2-oxo-
4-phenylfuran-3-carboxylate 4a in 72% yield.15 Simultaneous addi-
tion of potassium monomethyl malonate and K2CO3 to the in situ
formed a-tosyloxyacetophenone resulted in the formation of sev-
eral side products. This is due to competition between O-alkylation
and C-alkylation reactions of a-tosyloxyacetophenone with potas-
sium monomethyl malonate. Alternative bases such as Et3N and
piperidine were found to be inferior to K2CO3. The optimised reac-
tion conditions required 0.6 equiv of K2CO3 with respect to 1 equiv
of ketone to provide satisfactory yields of the product. The insolu-
bility of potassium monomethyl malonate in CH3CN affects the
yields of methyl 2-oxo-2-arylethyl malonates 3a–g. However, a
slight excess of potassium monomethyl malonate (1.2 equiv w.r.t.
ketone) improved the yield of the open-chain malonate 3. The
key intermediate, methyl 2-oxo-2-arylethyl malonate 3, was iso-
lated in a few cases (Table 1) and characterised by IR, NMR and
mass spectral analysis.16 The 1H NMR spectra of 3a–g exhibited
three sharp signals readily recognised as arising from two methyl-
enes (d 3.59 and d 5.34) and –COOMe (d 3.78) protons.
j
4j
a
Isolated yield.
To check the validity of the above-mentioned strategy for c-
butenolide synthesis (Scheme 1), we carried out the reaction of
isolated methyl 2-oxo-2-phenylethyl malonate 3a (1 mmol) with
K2CO3 (0.6 mmol) in acetonitrile at reflux (1.5 h). We obtained
methyl 2,5-dihydro-2-oxo-4-phenylfuran-3-carboxylate 4a in 69%
yield (Scheme 2). Comparing the 1H NMR spectral data of 3a with
cyclisation product 4a showed that the signal corresponding to the
methylene protons flanked by the two ester groups around d 3.58
had disappeared in the case of 4a.
After establishing optimum reaction conditions, we carried
out the synthesis of 3-carbomethoxy-4-arylfuran-2-(5H)-ones
by treating variously substituted acetophenones with potassium
monomethyl malonate using HTIB and the results are summarised
in Table 2. The corresponding 3,4-disubstituted furan-2-(5H)-ones
were obtained in good to excellent yields. To the best of our knowl-
edge, this is the first report on the synthesis of 2-furan-(5H)-ones
possessing an aryl group at C-4 position using potassium mono-
methyl malonate and substituted acetophenones.
In conclusion, we have developed a novel one-pot synthesis of
3-carbomethoxy-4-arylfuran-2-(5H)-ones via a-tosyloxylation of
ketones with HTIB followed by treatment with potassium mono-
methyl malonate and K2CO3. Extension of this method to the prep-
aration of other heterocyclic compounds of biological significance
is underway in this laboratory.
Table 1
Formation of methyl 2-oxo-2-arylethyl malonates from substituted acetophenones
and the potassium monomethyl malonate using HTIB in CH3CN
O
O
(i) PhI(OH)OTs, CH3CN, reflux (1.5 h)
(ii) MeO2CCH2CO2K, reflux (4-5 h)
OMe
O
Ar
Ar
Acknowledgements
O
O
1
3
The authors are thankful to the Department of Science and
Technology (No. SR/FTP/CS-77/2005) and the University Grants
Commission, New Delhi, India (No. MRP 32-245/2006 SR) for the
financial support.
Entry
Ar 1
Product
Yielda (%)
a
b
c
d
e
f
C6H5–
3a
3b
3c
3d
3e
3f
87
84
77
83
81
80
74
4-MeOC6H4–
2-MeOC6H4–
4-ClC6H4–
2-ClC6H4–
4-Br–C6H4–
4-O2N–C6H4–
Supplementary data
g
3g
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2008.05.012.
a
Isolated yield.

4404
N. N. Karade et al. / Tetrahedron Letters 49 (2008) 4402–4404
room temperature and K2CO3 (1.8 mmol) was added and the reaction mixture
References and notes
was refluxed for another 1.5 h. After completion of the reaction, it was diluted
with water and extracted with CHCl3 (15 mL Â 2). The organic layer was dried
over anhydrous Na2SO4 and concentrated under reduced pressure to give a
crude product, which was purified by silica gel column chromatography using
petroleum ether and ethyl acetate as eluent to afford the pure product.
16. Spectral data of selected products:Methyl 2-oxo-2-phenylethyl malonate (3a): IR
(KBr): m = 3024, 2983, 2939, 1759, 1736, 1701, 1597, 1450, 1371, 1336, 1228,
1. (a) Wirth, T. Angew. Chem., Int. Ed. 2005, 44, 3656; (b) Moriarty, R. M. J. Org.
Chem. 2005, 70, 2893; (c) Stang, P. J. J. Org. Chem. 2003, 68, 2997; (d) Zhdankin,
V. V.; Stang, P. J. Chem. Rev. 2002, 102, 2523; (e) Moriarty, R. M.; Prakash, O. Org.
React. 2002, 57, 327; Varvoglis, A. Hypervalent Iodine in Organic Synthesis;
Academic Press: London, 1997; Chapter 7, p 115.
2. (a) Kosser, G. F.; Wettach, R. H. J. Org. Chem. 1976, 41, 3609; (b) Kosser, G. F.;
Wettach, R. H. J. Org. Chem. 1977, 42, 1476; (c) Kosser, G. F.; Wettach, R. H. J.;
Smith, C. S. J. Org. Chem. 1980, 45, 1542; (d) Kosser, G. F.; Relenyi, A. G.; Kalos, A.
N.; Rebrovic, L.; Wettach, R. H. J. Org. Chem. 1982, 47, 2487; (e) Moriaraty, R. M.;
Penmasta, R.; Awasthi, A. K.; Epa, W. R.; Prakash, I. J. Org. Chem. 1989, 54, 1101.
3. (a) Kosser, G. F.; Wettach, R. H. J. Org. Chem. 1977, 42, 1476; (b) Moriarty, R. M.;
Vaid, R. K.; Hopkins, T. E.; Vaid, B. K.; Prakash, O. Tetrahedron Lett. 1990, 31, 201;
(c) Moriarty, R. M.; Vaid, B. K.; Duncan, M. P.; Levy, S. G.; Prakash, O.; Goyal, S.
Synthesis 1992, 845; (d) Prakash, O.; Goyal, S. Synthesis 1992, 629; (e) Prakash,
O.; Rani, N.; Goyal, S. J. Chem. Soc., Perkin Trans. 1 1992, 707; (f) Prakash, O.;
Saini, N.; Sharma, P. K. Synlett 1994, 221; (g) Prakash, O.; Saini, N.; Sharma, P. K.
Heterocycles 1994, 38, 409; (h) Uneno, M.; Togo, H. Synthesis 2004, 16, 2673.
4. (a) Tomioka, K.; Ishiguro, T.; Koga, K. J. Chem. Soc., Chem. Commun. 1979, 652;
(b) Tomioka, K.; Ishiguro, T.; Koga, K. Tetrahedron Lett. 1980, 21, 2973; (c)
Vigneron, J. P.; Meric, R.; Larcheveque, M.; Debal, A.; Kunesch, G.; Zagatti, P.;
Gallois, M. Tetrahedron Lett. 1982, 23, 5051; (d) Tomioka, K.; Sato, F.; Koga, K.
Heterocycles 1982, 17, 311; (e) Tomioka, K.; Ishiguro, T.; Litaka, Y.; Koga, K.
Tetrahedron 1984, 40, 1303; (f) Vigneron, J. P.; Meric, R.; Larcheveque, M.;
Debal, A.; Lallemand, J. Y.; Kunesch, G.; Zagatti, P.; Gallois, M. Tetrahedron 1984,
40, 3521; (g) Mann, J.; Thomas, A. J. J. Chem. Soc., Chem. Commun. 1985, 737; (h)
Drew, M. G. B.; Mann, J.; Thomas, A. J. J. Chem. Soc., Perkin Trans. 1 1986, 2279;
(i) Mann, J.; Thomas, A. J. Tetrahedron Lett. 1986, 27, 3533; (j) Ortega, M. J.;
Zubia, E.; Ocana, J. M.; Naranjo, S.; Salva, J. Tetrahedron 2000, 56, 3963.
5. Review: (a) Ranganathan, S.; Muraleedharan, K. M.; Vaish, N. K.; Jayaraman, N.
Tetrahedron 2004, 60, 5273; (b) Lopez, J. A.; Guerra, F. M.; Moreno-Dorado, F. J.;
Jorge, Z. D.; Massanet, G. M. Tetrahedron Lett. 2007, 48, 1749; (c) Babu, S. A.;
Yasuda, M.; Okabe, Y.; Shibata, I.; Baba, A. Org. Lett. 2006, 8, 3029; (d) Liu, Y.;
Liu, M.; Guo, S.; Tu, H.; Zhou, Y.; Gao, H. Org. Lett. 2006, 8, 3445; (e) Genin, E.;
Toullec, Y.; Antoniotti, S.; Brancour, C.; Genet, J.-P.; Michelet, V. J. Am. Chem. Soc.
2006, 128, 3112; (f) Bassetti, M.; D’Annibale, A.; Fanfoni, A.; Minissi, F. Org. Lett.
2005, 7, 1805; (g) Yang, C.-G.; Reich, N. W.; Shi, Z.; He, C. Org. Lett. 2005, 7,
4553; (h) Wu, J.; Zhu, Q.; Wang, L.; Fathi, R.; Yang, Z. J. Org. Chem. 2003, 68, 670;
(i) Ma, S.; Wu, S. J. Org. Chem. 1999, 64, 9314; (j) Ma, S.; Shi, Z. J. Org. Chem.
1998, 63, 6387.
6. (a) Kosser, G. F.; Rebrovic, L.; Wettach, R. H. J. Org. Chem. 1981, 46, 4324; (b)
Rebrovic, L.; Kosser, G. F. J. Org. Chem. 1984, 49, 2462.
7. (a) Shah, M.; Taschner, M. J.; Kosser, G. F.; Rach, N. L. Tetrahedron Lett. 1986, 27,
4557; (b) Shah, M.; Taschner, M. J.; Kosser, G. F.; Rach, N. L.; Jenkins, T. E.; Cyr,
P.; Powers, D. Tetrahedron Lett. 1986, 27, 5437.
8. Moriarty, R. M.; Vaid, R. K.; Hopkins, T. E.; Vaid, B. K.; Prakash, O. Tetrahedron
Lett. 1990, 31, 201.
9. Browne, D. M.; Niyomura, O.; Wirth, T. Org. Lett. 2007, 16, 3169.
10. Dohi, T.; Takenaga, N.; Goto, A.; Maruyama, A.; Kita, Y. Org. Lett. 2007, 16, 3129.
11. (a) Szumny, A.; Wawrzenczyk, C. Synlett 2006, 1523; (b) De Mattos, M. C. S.; De
Souza, S. P. L.; Elias, S. M. Heterocycl. Commun. 2003, 3, 247; (c) Solabannavar, S.
B.; Helavi, V. B.; Desai, U. V.; Mane, R. B. Tetrahedron Lett. 2002, 25, 4535.
12. (a) Fristad, W. E.; Peterson, J. R.; Ernst, A. B. J. Org. Chem. 1985, 50, 3143; (b)
Peterson, J. R.; Do, H. D.; Surjasasmita, I. B. Synth. Commun. 1988, 18, 1985; (c)
Allegretti, M.; D’Annibale, A.; Trogolo, C. Tetrahedron 1993, 49, 10705; (d)
D’Annibale, A.; Trogolo, C. Tetrahedron Lett. 1994, 35, 2083; (e) Lamarque, L.;
Meou, A.; Brun, P. Tetrahedron Lett. 1998, 39, 8283; (f) Lamarque, L.; Meou, A.;
Brun, P. Tetrahedron 1998, 54, 6497.
13. Reaction of dimethyl malonate with 1 equiv of KOH in MeOH at room
temperature with stirring readily affords monopotassium methyl malonate.
14. (a) Karade, N. N.; Tiwari, G. B.; Huple, D. B. Synlett 2005, 2039; (b) Karade, N. N.;
Tiwari, G. B.; Gampawar, S. V. Synlett 2007, 1921; (c) Karade, N. N.; Gampawar,
S. V.; Tiwari, G. B. Lett. Org. Chem. 2007, 6, 419; (d) Karade, N. N.; Shirodkar, S.
G.; Dhoot, B. M.; Waghmare, P. B. J. Chem. Res. (S) 2005, 4, 274; (e) Karade, N. N.;
Budhewar, V. H.; Katkar, A. N.; Tiwari, G. B. ARKIVOC 2006, 162.
1149, 1031, 973, 759, 691 cmÀ1 1H NMR (400 MHz, CDCl3): d = 3.59 (s, 2H,
.
CH2), 3.78 (s, 3H, COOCH3), 5.41 (s, 2H, OCH2), 7.51 (t, J = 7.48 Hz, 2H, ArH),
7.61 (t, J = 7.48 Hz, 1H, ArH), 7.90 (d, 2H, J = 7.12 Hz, ArH). 13C NMR (400 MHz,
CDCl3): d = 41.08, 52.77, 70.64, 119.14, 127.86, 129.15, 132.21, 162.75, 165.22,
169.55. LCMS (M+1): m/z = 237.
Methyl 2-oxo-2-(4-methoxyphenyl)ethyl malonate (3b): IR (KBr): m = 2981, 2953,
2845, 1749, 1712, 1693, 1600, 1506, 1431, 1284, 1161, 1022, 844, 779 cmÀ1 1H
.
NMR (400 MHz, CDCl3): d = 3.58 (s, 2H, CH2), 3.78 (s, 3H, COOCH3), 3.88 (s, 3H,
OCH3), 5.36 (s, 2H, CH2), 6.96 (d, 2H, J = 8.96 Hz, ArH), 7.89 (d, 2H, J = 8.96 Hz,
ArH). 13C NMR (400 MHz, CDCl3): d = 41.02, 52.64, 55.60, 66.57, 114.17, 127.08,
130.16, 164.22, 166.08, 189.80. LCMS (M+1): m/z = 267.
Methyl 2-oxo-2-(2-methoxyphenyl)ethyl malonate (3c): 1H NMR (400 MHz,
CDCl3): d = 3.57 (s, 2H, CH2), 3.78 (s, 3H, COOCH3), 3.95 (s, 3H, OCH3), 5.31
(s, 2H), 6.99 (d, 1H, J = 8.52 Hz, ArH), 7.05 (t, 1H, J = 8 Hz, ArH), 7.52–7.55 (m,
1H, ArH), 7.94 (d, 1H, J = 7.95 Hz, ArH). LCMS (M+1): m/z = 267.
Methyl 2-oxo-2-(4-chlorophenyl)ethyl malonate (3d): 1H NMR (400 MHz, CDCl3):
d = 3.59 (s, 2H, CH2), 3.78 (s, 3H, COOCH3), 5.37 (s, 2H, CH2), 7.48 (d, 2H,
J = 8.6 Hz, ArH), 7.85 (d, 2H, J = 8.6 Hz, ArH). LCMS (M+1): 271.
Methyl 2-oxo-2-(2-chlorophenyl)ethyl malonate (3e): IR (KBr): m = 3026, 2956,
2928, 1759, 1741, 1589, 1431, 1338, 1217, 1149, 971, 785 cmÀ1 1H NMR
;
(400 MHz, CDCl3): d = 3.54 (s, 2H, CH2), 3.76 (s, 3H, COOCH3), 5.29 (s, 2H), 7.37
(m, 1H, ArH), 7.45 (m, 2H, ArH), 7.64 (m, 1H, ArH). 13C NMR (400 MHz,
CDCl3):d = 40.82, 52.69, 69.00, 127.23, 130.17, 130.68, 131.70, 133.06, 135.49,
165.91, 166.53, 194.33. LCMS (M+1): m/z = 271.
Methyl 2-oxo-2-(4-bromophenyl)ethyl malonate (3f): IR (KBr): m = 3022, 2995,
1753, 1730, 1701, 1585, 1432, 1346, 1203, 1159, 1068, 981, 821 cmÀ1 1H NMR
.
(400 MHz, CDCl3): d = 3.58 (s, 2H, CH2), 3.78 (s, 3H, COOCH3), 5.33 (s, 2H,
OCH2), 7.64 (d, 2H, J = 8.64 Hz, ArH), 7.76 (d, 2H, J = 8.64 Hz, ArH). 13C NMR
(400 MHz, CDCl3): d = 40.88, 52.69, 66.59, 129.29, 132.30, 132.45, 132.71,
165.95, 166.58, 190.53. LCMS (M+1):m/z = 316.
Methyl 2,5-dihydro-2-oxo-4-phenylfuran-3-carboxylate (4a): IR (KBr): m = 3024,
2970, 2937, 1751, 1732, 1637, 1442, 1372, 1340, 1242, 1069, 1039, 768,
696 cmÀ1 1H NMR (400 MHz, CDCl3): d = 3.89 (s, 3H, COOCH3), 5.18 (s, 2H,
.
OCH2), 7.46–7.55 (m, 5H, ArH). 13C NMR (400 MHz, CDCl3): d = 52.79, 70.66,
119.10, 127.87, 129.15, 132.24, 162.77, 165.31, 169.60. LCMS (M+1): m/z = 219.
Methyl 2,5-dihydro-4-(4-methoxyphenyl)-2-oxofuran-3-carboxylate (4b): IR
(KBr): m = 3018, 2953, 2927, 1739, 1605, 1515, 1435, 1215, 1179, 1030, 753,
667 cmÀ1 1H NMR (400 MHz, CDCl3): d = 3.87 (s, 3H, OMe), 3.91 (s, 3H, OMe),
.
5.16 (s, 2H, OCH2), 6.98 (d, 2H, J = 8.92 Hz, ArH), 7.56 (d, 2H, J = 8.88 Hz, ArH).
13C NMR (400 MHz, CDCl3): d = 52.72, 55.56, 70.38, 114.57, 116.49, 121.35,
130.08, 162.91, 163.34, 164.51, 170.08. LCMS (M+1): m/z = 249.
Methyl 2,5-dihydro-4-(2-methoxyphenyl)-2-oxofuran-3-carboxylate (4c): IR
(KBr): m = 3076, 2951, 2838, 1731, 1599, 1536, 1462, 1434, 1248, 1165, 1022,
802, 754 cmÀ1 1H NMR (400 MHz, CDCl3): d = 3.81 (s, 3H, OMe), 3.84 (s, 3H,
.
OMe), 5.18 (s, 2H, OCH2), 6.99 (d, 1H, J = 11.2 Hz, ArH), 7.04 (t, 1H, J = 8.8 Hz,
ArH), 7.31 (d, 1H, J = 8.0 Hz, ArH), 7.47 (t, 1H, J = 7.6 Hz, ArH). 13C NMR
(400 MHz, CDCl3): d = 52.43, 55.45, 71.45, 111.51, 118.67, 120.44, 120.93,
129.29, 133.20, 156.93, 162.76, 163.93, 169.85. LCMS (M+1):m/z = 249.
Methyl 2,5-dihydro-2-oxo-4-p-tolylfuran-3-carboxylate (4e): IR (KBr): m = 3032,
2960, 2926, 2870, 1750, 1716, 1631, 1609, 1433, 1344, 1249, 1132, 819, 787,
713 cmÀ1 1H NMR (400 MHz, CDCl3): d = 2.42 (s, 3H, ArCH3), 3.78 (s, 3H,
.
COOCH3), 5.39 (s, 2H, OCH2), 7.28 (d, 2H, J = 8.96 Hz, ArH), 7.81 (d, 2H, J = 8 Hz,
ArH). 13C NMR (400 MHz, CDCl3): d = 21.64, 52.73, 70.54, 118.09, 126.24,
127.89, 129.85, 143.23, 163.01, 165.11, 169.79. LCMS (M+1): m/z = 233.
Methyl 2,5-dihydro-4-(4-bromophenyl)-2-oxofuran-3-carboxylate (4f): 1H NMR
(400 MHz, CDCl3): d = 3.90 (s, 3H, OMe), 5.15 (s, 2H, OCH2), 7.43 (d, 2H, J = 8.68
Hz, ArH), 7.63 (d, 2H, J = 8.68 Hz, ArH). LCMS (M+1): m/z = 297.
Methyl 2,5-dihydro-4-(4-chlorophenyl)-2-oxofuran-3-carboxylate (4h): IR (KBr):
m = 2982, 2847, 1747, 1723, 1617, 1488, 1376, 1341, 1299, 1252, 832,
15. Experimental procedure: To a solution of ketone (3 mmol) in MeCN (15 mL) was
added [hydroxyl(tosyloxy)iodo]benzene (3.3 mmol) and the mixture was
refluxed for 1.5 h. After successful formation of the a-tosyloxyketone (as
monitored by TLC), potassium monomethyl malonate (3.6 mmol) was added
and the reaction mixture was refluxed for 4–5 h until complete consumption of
the a-tosyloxyketone had taken place. Then the reaction mixture was cooled to
764 cmÀ1 1H NMR (400 MHz, CDCl3): d = 3.92 (s, 3H, OMe), 5.17 (s, 2H,
.
OCH2), 7.53 (d, 2H, J = 11.2 Hz, ArH), 7.48 (d, 2H, J = 11.2 Hz, ArH). 13C NMR
(400 MHz, CDCl3): d = 52.93, 70.49, 119.51, 127.57, 129.32, 129.53, 138.60,
162.52, 164.20, 169.24. LCMS (M+1): m/z = 253.