Hypervalent iodine(III) sulfonate mediated synthesis of 5-benzoyldihydro-2(3H)-furan-one in ionic solvent

Article abstract of DOI:10.3987/COM-04-10301

The room temperature ionic liquid, n-butylpyridinium tetrafluoroborate(BPyBF₄) is used as a "green" recyclable solvent for the reaction of 4-benzoylbutyric acid with [hydroxy-(2,4-dinitrobenzenesulfonyloxy)iodo]-benzene (HDNIB) to prepare 5-benzoyldihydro-2(3H)-furanone.

Full text of DOI:10.3987/COM-04-10301

HETEROCYCLES, Vol. 65, No. 3, 2005
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HETEROCYCLES, Vol. 65, No. 3, 2005, pp. 649 - 656
Received, 6th December, 2004, Accepted, 14th January, 2005, Published online, 21st January, 2005
HYPERVALENT IODINE(III) SULFONATE MEDIATED
SYNTHESIS OF
5-BENZOYLDIHYDRO-2(3H)-FURAN-
ONE IN IONIC SOLVENT
Rei-Sheu Hou,a Huey-Min Wang,a Yu-Chien Lin,b and Ling-Ching Chen*b
a Chung Hwa College of Medical Technology, Tainan, Taiwan 717, R.O.C.
b Graduate Institute of Pharmaceutical Sciences, Kaohsiung Medical University,
Kaohsiung, Taiwan 807, R.O.C.
Abstract⎯The room temperature ionic liquid, n-butylpyridinium tetrafluoroborate
(BPyBF4) is used as a “green” recyclable solvent for the reaction of
4-benzoylbutyric acid with [hydroxy-(2,4-dinitrobenzenesulfonyloxy)iodo]-
benzene (HDNIB) to prepare 5-benzoyldihydro-2(3H)-furanone.
Room temperature ionic liquids (RTIL) are liquids that are composed entirely of ions. In fact, ionic
liquids can now be produced which remain liquid at room temperature and below (even as low as -90℃)
and appear to be undemanding and inexpensive to manufacture.1 Ionic liquids offer an attractive alterative
to conventional organic liquids for clean synthesis, as they are easy to recycle, lack flammability, and
possess effectively no vapour pressure. Compared with classical molecular solvents, the ionic liquids are
environmentally benign reaction media.2 To date some of the more important reactions have been carried
out and investigated in ionic liquids, for example, Friedel–Crafts reaction,3 alkoxycarbonylation,4
hydrogenation,5 Diels–Alder reaction,6 Wittig reaction,7 Heck reaction,8 Trost-Tsuji coupling,9
ring-closing metathesis (RCM),10 Suzuki cross-coupling,11 Fischer indole synthesis,12 1,3-dipolar
cycloaddition reaction,13 Beckmann rearrangement,14 the Knoevenagel, and Robinson annulation
reactions,15 etc.
Lactonisation methodology plays an important role in modern organic synthetic chemistry not only
because lactones occur in nature in great abundance and variety,16 but also because they constitute a
particularly useful class of synthons.17 The preparation of lactones was via cyclization of acyclic olefinic
carboxylic acids.18 Recently, Moriarty et al. have developed a simple and useful route to synthesize
19
5-benzoyldihydro-2(3H)-furanone by using [hydroxy(tosyloxy)iodo]benzene (HTIB). As part of a
program to investigate the range of organic reactions possible in ionic liquids, we were interested in the

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HETEROCYCLES, Vol. 65, No. 3, 2005
reaction of 4-benzoylbutyric acid with [hydroxy-(2,4-dinitrobenzenesulfonyloxy)iodo]benzene (HDNIB)
to prepare 5-benzoyldihydro-2(3H)-furanone in ionic liquids. The required HDNIB was prepared in
satisfory yields from the reaction of 2,4-dinitrobenzenesulfonic acid with phenyliodine(III)
diacetate(PIDA).20
For this study, the accessible and cheaper ionic liquid, n-butylpyridiniumtetrafluoroborate (BPyBF4) was
a strong candidate and was synthesized according to the procedures reported in the literature.1 The scope
of the reaction of various 4-benzoylbutyric acids (1) with HDNIB in BPyBF4 was investigated. We found
that the reaction of 4-benzoylbutyric acids (1) with HDNIB occurred easily in BPyBF4 at 90℃for 2 h to
give the desired 5-benzoyldihydro-2(3H)-furanones (2) in good yields (Scheme I). The results are
summarized in Table 1. When the reaction was conducted in the classical solvents, such as
dichloromethane, the preparation of 5-benzoyldihydro-2(3H)-furanone (2a) needs refluxing for 15 h by
using HTIB.19
R4
R4
HDNIB
BPyBF
R1
R1
O
O
4 , 90oC
COOH
O
O
R2
R2
R3
R3
O2N
HO I O SO2
1
2
NO2
HDNIB =
Scheme I
Table1. Preparation of 5-benzoyldihydro-2(3H)-furanones (2)
Entry
1
Product
R1
H
R2
H
R3
H
R4
H
Yield(%)
76
2a
2
3
4
5
6
7
8
9
Me
MeO
Cl
H
H
H
H
H
72
70
78
73
71
75
80
84
2b
2c
2d
2e
2f
H
H
H
H
Br
H
H
H
Me
H
H
H
Me
Me
H
Me
H
H
2g
2h
2i
i-pr
Me
H
H
Me
Me

HETEROCYCLES, Vol. 65, No. 3, 2005
651
Our experiments showed that after the isolation of the product, the ionic liquid BPyBF4 can be resused
several times without loss of activity (Table 2).
Table 2. Results obtained using recycled ionic liquid
Entry
1
Product
Cycle
1
Yield(%)
75
2a
2
3
2
3
72
73
2a
2a
In summary, the method described herein provides a good approach for the synthesis of
5-benzoyldihydro-2(3H)-furanones by the reaction of 4-benzoylbutyric acids with HDNIB in room
temperature ionic liquid BPyBF4 at 90℃ and gives good yields. Separation of products from the ionic
liquids is very straight forward, as is recycling of the ionic liquid.
ACKNOWLEDGEMENT
We gratefully acknowledge the National Science Council of the Republic of China for the financial
support of this work (Grant No. 92-2113-M-037-014).
EXPERIMENTAL
All melting points are uncorrected. The IR spectra were recorded on a Shimadzu IR-27 G
spectrophotometer. 1H NMR spectra were recorded on a Varian Unity Plus 400 MHz. Chemical shifts (δ)
were measured in ppm with respect to TMS. MS were obtained on a JEOL JMS D-300 instrument.
5-Oxo-5-phenylpentanoic acid (1a) was commercially available from Aldrich.
Typical procedure for the preparation of 4-benzoylbutyric acids (1)21
A solution of glutaric andydride (1.14 g, 10 mmol) in dry toluene (10 mL) was added with stirring to an
ice cold suspension of powdered andydrous AlCl3 (3.33 g, 25 mmol) in dry toluene (5 mL). The mixture
was kept at rt for 12 h and then warm at 60-65 ℃for 0.5 h. The product was decomposed with ice and
37 % HCl and the excess of toluene removed by distillation. The solid product was extracted with hot
NaHCO3, the keto acid was precipitate with 37 % HCl to give 1b.
5-Oxo-5-p-tolylpentanoic acid (1b)

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HETEROCYCLES, Vol. 65, No. 3, 2005
mp 146-148 ℃ (AcOEt/hexane). IR (KBr) ν : 2937, 1701, 1654 cm-1. 1HNMR (CDCl3) δ : 2.08 (q, J =
7.2 Hz, 2H), 2.41 (s, 3H), 2.49 (t, J = 7.2 Hz, 2H), 3.05 (t, J = 6.8 Hz, 2H), 7.25 (d, J = 8.4 Hz, 2H),
7.86 (d, J = 8.4 Hz, 2H). EI-MS: 206 (M+), 119, 91. Anal. Calcd for C12H14O3 : C, 69.89; H, 6.84.
Found : C, 69.63; H, 6.72.
5-(4-Methoxyphenyl)-5-oxopentanoic acid (1c)
mp 136-138 ℃ (AcOEt/hexane). IR (KBr) ν : 2961, 1705, 1667 cm-1. 1HNMR (CDCl3) δ : 2.08 (q, J =
7.2 Hz, 2H), 2.49 (t, J = 7.0 Hz, 2H), 3.03 (t, J = 7.0 Hz, 2H), 3.87 (s, 3H), 6.93 (d, J =7.2 Hz, 2H),
7.94 (d, J =7.2 Hz, 2H). EI-MS: 222 (M+), 150, 135. Anal. Calcd for C12H14O4 : C, 64.85; H, 6.35.
Found : C, 64.63; H, 6.57.
5-(4-Chlorophenyl)-5-oxopentanoic acid (1d)
mp 118-120 ℃ (AcOEt/hexane). IR (KBr) ν : 2900, 1727, 1694 cm-1. 1HNMR (CDCl3) δ : 2.08 (q, J =
7.2 Hz, 2H), 2.50 (t, J = 7.0 Hz, 2H), 3.05 (t, J = 7.2 Hz, 2H), 7.44 (d, J = 8.4 Hz, 2H), 7.90 (d, J = 8.8
Hz, 2H). EI-MS: 226 (M+), 141, 139. Anal. Calcd for C11H11O3Cl : C, 58.29; H, 4.89. Found : C, 58.45;
H, 5.08.
5-(4-Bromophenyl)-5-oxopentanoic acid (1e)
mp 116-118 ℃ (AcOEt/hexane). IR (KBr) ν : 2964, 1700, 1640 cm-1. 1HNMR (CDCl3) δ : 2.09 (q, J =
7.2 Hz, 2H), 2.48-2.52 (m, 2H), 3.03-3.10 (m, 2H), 7.55-7.62 (m, 2H), 7.95-7.98 (m, 2H). EI-MS: 273
(M++2), 271 (M+), 185, 183. Anal. Calcd for C11H11O3Br : C, 48.73; H, 4.09. Found : C, 48.51; H, 4.23.
5-(2,4-Dimethylphenyl)-5-oxopentanoic acid (1f)
mp 117-119 ℃ (AcOEt/hexane). IR (KBr) ν : 2937, 1704, 1679 cm-1. 1HNMR (CDCl3) δ : 2.05 (q, J =
7.2 Hz, 2H), 2.35 (s, 3H), 2.47 (t, J = 7.2 Hz, 2H), 2.49 (s, 3H), 2.99 (t, J = 7.2 Hz, 2H), 7.06-7.07 (m,
2H), 7.59 (d, J = 8.4 Hz, 1H). EI-MS: 220 (M+), 133, 105. Anal. Calcd for C13H16O3 : C, 70.89; H, 7.32.
Found : C, 69.54; H, 7.16.
5-(2,5-Dimethylphenyl)-5-oxopentanoic acid (1g)
mp 68-70 ℃ (AcOEt/hexane). IR (KBr) ν : 2937, 1704, 1679 cm-1. 1HNMR (CDCl3) δ : 2.05 (q, J = 7.2
Hz, 2H), 2.35 (s, 3H), 2.44 (s, 3H), 2.49 (t, J = 7.2 Hz, 2H), 2.98 (t, J = 7.2 Hz, 2H), 7.12 (d, J = 8.0 Hz,
1H), 7.18 (dd, J = 1.4, 8.0 Hz, 1H), 7.43 (s, 1H). EI-MS: 220 (M+), 133, 105. Anal. Calcd for C13H16O3 :
C, 70.89; H, 7.32. Found : C, 71.06; H, 7.54.
5-(4-Isopropylphenyl)-5-oxopentanoic acid (1h)
Oily compound. IR (neat) ν : 2959, 1691, 1604 cm-1. 1HNMR (CDCl3) δ : 1.25 (s, 6H), 2.08 (q, J = 7.2
Hz, 2H), 2.49 (t, J = 7.0 Hz, 2H), 2.85-2.99 (m, 1H), 3.06 (t, J = 7.2 Hz, 2H), 7.31 (d, J = 8.4 Hz, 2H),
7.90 (d, J = 8.4 Hz, 2H). EI-MS: 234 (M+), 147. HRMS (EI) Calcd for C14H18O3: 234.1255. Found:
234.1256. Anal. Calcd for C14H18O3 : C, 71.77; H, 7.74. Found : C, 71,52; H, 7.58.

HETEROCYCLES, Vol. 65, No. 3, 2005
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5-Oxo-5-(2,4,6-trimethylphenyl)pentanoic acid (1i)
Oily compound. IR (neat) ν : 2979, 1732, 1696 cm-1. 1HNMR (CDCl3) δ : 2.03 (q, J = 7.2 Hz, 2H), 2.16
(s, 6H), 2.26 (s, 3H), 2.42 (t, J = 7.2 Hz, 2H), 2.75 (t, J = 7.2 Hz, 2H), 6.81 (s, 2H). 13CNMR (CDCl3) δ :
17.1, 18.2, 20.2, 32.6, 42.9, 127.9, 131.7, 137.9, 173.0, 210.4. EI-MS: 234 (M+), 147, 119. HRMS (EI)
Calcd for C14H18O3: 234.1255. Found: 234.1254. Anal. Calcd for C14H18O3 : C, 71.77; H, 7.74. Found : C,
71,57; H, 7.62.
Typical procedure for the preparation of 5-benzoyldihydro-2(3H)-furanones (2)
A mixture of 4-benzoylbutyric acid (0.20 g, 1 mmol), HDNIB (0.94 g, 2 mmol) and ionic liquid (2 mL)
was stirred for 2 h at 90 ℃. The reaction mixture was extracted with Et2O. The remaining ionic liquid
suspension was filtered, and reused after drying in vacuum. The combined ethereal solution was
evaporated under reduced pressure. The residue was chromatography on silica gel column eluting with
CHCl3-AcOEt (9:1) to give 2a.
5-Benzoyldihydro-2(3H)-furanone (2a)
1
mp 77-78 ℃ (CHCl3/hexane) (lit.,22 78-79 ℃). IR (neat) ν : 1780, 1687, 1245, 1060 cm-1. HNMR
(CDCl3) δ : 2.44-2.62 (m, 4H), 5.79-5.82 (m, 1H), 7.50-7.55 (m, 2H), 7.63-7.67 (m, 1H), 7.98 (dd, J =
1.2, 8.8 Hz, 2H). 13CNMR (CDCl3) δ : 24.9, 26.6, 78.1, 128.5, 128.8, 133.3, 134.1, 176.3, 194.4. EI-MS:
105, 77.
5-(4-Methylbenzoyl)dihydro-2(3H)-furanone (2b)
1
mp 89-90 ℃ (CHCl3/hexane) (lit., 23 90-91 ℃). IR (neat) ν : 1768, 1689, 1229, 1066 cm-1. HNMR
(CDCl3) δ : 2.44 (s, 3H), 2.44-2.62 (m, 4H), 5.76-5.79 (m, 1H), 7.31 (d, J = 8.4 Hz, 2H), 7.88 (d, J =
8.4 Hz, 2H). 13CNMR (CDCl3) δ : 21.7, 25.0, 26.8, 78.1, 128.8, 128.9, 129.6, 129.7, 131.0, 145.4, 176.3,
193.9. EI-MS: 204 (M+), 119, 91.
5-(4-Methoxybenzoyl)dihydro-2(3H)-furanone (2c)
mp 121-123 ℃ (CHCl3/hexane) (lit., 22 122-124 ℃). IR (neat) ν : 1773, 1683, 1244, 1071 cm-1. 1HNMR
(CDCl3) δ : 2.48-2.65 (m, 4H), 3.89 (s, 3H), 5.73-5.76 (m, 1H), 6.98 (d, J = 8.8 Hz, 2H), 7.97 (d, J =
13
8.8 Hz, 2H). CNMR (CDCl3) δ : 25.0, 26.9, 55.6, 78.1, 114.2, 126.6, 131.2, 164.4, 176.4, 192.7.
EI-MS: 220 (M+), 135, 77.
5-(4-Chlorobenzoyl)dihydro-2(3H)-furanone (2d)
1
mp 92-93 ℃ (CHCl3/hexane) (lit., 23 93-94 ℃). IR (neat) ν : 1773, 1694, 1282, 1071 cm-1. HNMR
(CDCl3) δ : 2.54-2.59 (m, 4H), 5.69-5.74 (m, 1H), 7.49 (dd, J = 2.0, 6.4 Hz, 2H), 7.95 (dd, J = 2.0, 6.8
13
Hz, 2H). CNMR (CDCl3) δ : 24.6, 26.8, 78.2, 129.3, 130.2, 131.9, 140.9, 175.9, 193.2. EI-MS: 141,
139.
5-(4-Bromobenzoyl)dihydro-2(3H)-furanone (2e)

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1
mp 71-73 ℃ (CHCl3/hexane) (lit., 23 70-72 ℃). IR (neat) ν : 1780, 1690, 1244, 1064 cm-1. HNMR
13
(CDCl3) δ : 2.45-2.63 (m, 4H), 5.79-5.82 (m, 1H), 7.63-7.68 (m, 2H), 7.97-8.00 (m, 2H). CNMR
(CDCl3) δ : 24.9, 26.7, 78.2, 128.7, 128.9, 130.2, 132.3, 133.4, 134.2, 176.3, 194.3. EI-MS: 271, 269
(M+), 185, 183, 155, 77.
5-(2,4-Dimethylbenzoyl)dihydro-2(3H)-furanone (2f)
1
mp 145-146 ℃ (CHCl3/hexane) (lit., 23 146 ℃). IR (neat) ν : 1783, 1688, 1245, 1063 cm-1. HNMR
(CDCl3) δ : 2.33-2.62 (m, 4H), 2.38 (s, 3H), 2.52 (s, 3H), 5.69-5.72 (m, 1H), 7.11 (d, J = 8.0 Hz, 1H),
13
7.12 (s, 1H), 7.59 (d, J = 8.0 Hz, 1H). CNMR (CDCl3) δ : 21.4, 21.5, 25.2, 26.8, 78.9, 128.5, 129.4,
130.5, 133.3, 140.4, 143.5, 176.5, 196.8. EI-MS: 218 (M+), 133, 105.
5-(2,5-Dimethylbenzoyl)dihydro-2(3H)-furanone (2g)
1
Oily compound. IR (neat) ν : 1783, 1692, 1244, 1063 cm-1. HNMR (CDCl3) δ : 2.38 (s, 3H), 2.47 (s,
3H), 2.49-2.64 (m, 4H), 5.68-5.72 (m, 1H), 7.18 (d, J = 8.0 Hz, 1H), 7.26-7.27 (m, 1H), 7.44 (s, 1H).
13CNMR (CDCl3) δ : 20.6, 20.7, 25.0, 26.7, 79.1, 129.3, 132.1, 133.2, 135.4, 136.5, 137.2, 176.4, 197.8.
EI-MS: 218 (M+), 133, 105. HRMS (EI) Calcd for C13H14O3: 218.0943. Found: 218.0946. Anal. Calcd
for C13H14O3: C, 71.54; H, 6.47. Found: C, 71.42; H, 6.63
5-(4-Isopropylbenzoyl)dihydro-2(3H)-furanone (2h)
mp 81-83 ℃(CHCl3/hexane). IR (KBr) ν : 1770, 1687, 1601, 1225, 1072 cm-1. 1HNMR (CDCl3) δ : 1.28
(d, J = 6.8 Hz, 6H), 2.45-2.64 (m, 4H), 2.95-3.02 (m, 1H), 5.77-5.80 (m, 1H), 7.36 (d, J = 8.4 Hz, 2H),
13
7.91 (d, J = 8.4 Hz, 2H). CNMR (CDCl3) δ : 23.4, 24.9, 26.7, 34.2, 78.1, 126.9, 128.9, 131.2, 176.2,
193.8. EI-MS: 147, 91. Anal. Calcd for C14H16O3: C, 72.39; H, 6.94. Found: C, 72.43; H, 6.85.
5-(2,4,6-Trimethylbenzoyl)dihydro-2(3H)-furanone (2i)
Oily compound. IR (neat) ν : 1787, 1707, 1609, 1251, 1063 cm-1. 1HNMR (CDCl3) δ : 2.17 (s, 6H), 2.24
(s, 3H), 2.16-2.61 (m, 4H), 5.23-5.26 (m, 1H), 6.78 (s, 2H). 13CNMR (CDCl3) δ : 19.5, 21.0, 24.5, 24.6,
26.9, 81.8, 128.8, 130.6, 134.0, 134.9, 137.3, 139.9, 176.0, 205.6. EI-MS: 232 (M+), 149, 147, 121, 105.
HRMS (EI) Calcd for C14H16O3: 232.1099. Found: 232.1097. Anal. Calcd for C14H16O3: C, 72.39; H,
6.94. Found: C, 72.52; H, 6.78
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