Efficient preparation of 4-Iodofuran-2(5H)-ones by iodolactonisation of 2,3-allenoates with I2

Article abstract of DOI:10.1002/ejoc.200500296

4-Iodofuran-2(5H)-ones were prepared, in moderate to high yields, by the facile iodolactonisation of ethyl 2,3-allenoates with I₂ in aqueous MeCN by the direct participation of the carbonyl oxygen atom in the regioselective electrophilic additi

Full text of DOI:10.1002/ejoc.200500296

FULL PAPER
Efficient Preparation of 4-Iodofuran-2(5H)-ones by Iodolactonisation of 2,3-
Allenoates with I2
Chunling Fu[a] and Shengming Ma*[a,b]
Keywords: Allenes / Cyclisation / Esters / Iodine / Lactones
4-Iodofuran-2(5H)-ones were prepared, in moderate to high
yields, by the facile iodolactonisation of ethyl 2,3-allenoates
with I2 in aqueous MeCN by the direct participation of the
carbonyl oxygen atom in the regioselective electrophilic ad-
dition of the allene moiety.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
Butenolides are a class of compounds with biological
interest.[1,2] Recently, we have developed some methodolo-
gies for the synthesis of differently substituted butenol-
ides,[3,4] and we have also developed a halolactonisation of
2,3-allenoic acids that affords 3-halobutenolides, which are
important precursors for introducing different substituents
at the β-position in related coupling reactions.[5] 2,3-Al-
lenoic acids are usually prepared by the hydrolysis of 2,3-
allenoates in a process that usually affords 3-alkynoic acids
as by-products.[6] Thus, new protocols for the direct synthe-
sis of 4-halobutenolides from 2,3-allenoates are highly de-
sirable. Gill et al. have reported that the reaction of ethyl 4-
methyl-2,3-butadienoate with Br2 in CCl4 affords the corre-
sponding β-bromobutenolides in 56–58% yields.[7] We have
also succeeded in the direct halolactonisation of 2,3-al-
lenoates with CuBr2, which affords 3-bromobutenolides.[8]
However, the coupling reaction of a C–Br bond is, in most
cases, not as efficient as that of a C–I bond. Marshall et al.
have reported the iodolactonisation of methyl, (trimethyl-
silyl)ethyl, or benzyl esters of some 2,3-allenoic acids with
IBr.[6] Herein, we wish to report an efficient iodolactonis-
ation of 2,3-allenoates with I2, which is cheaper and more
readily available.
Scheme 1.
Recently, we have observed a highly stereoselective
iodohydroxylation of 1,2-allenyl sulfoxides with I2, in which
the sulfinyl group participates in the electrophilic addition
process to afford (Z)-2-iodo-3-sulfinyl-2-alkenols via five-
membered intermediates.[9] Thus, we imagined that we may
be able to develop a protocol for the direct iodolactonis-
ation of 2,3-allenoates with the participation of the car-
bonyl oxygen atom. We tested this protocol with ethyl 2,3-
allenoate 3a as the starting material, and were lucky to ob-
serve that the iodolactonisation occurred in an aqueous
MeCN (MeCN/H2O = 4:1) solution to afford the expected
product 4a in 61% yield (Entry 1, Table 1). Through screen-
ing, we found that the best MeCN/H2O ratio is 15:1 (En-
try 4, Table 1). It should be noted that the reaction in the
absence of H2O affords 4a in only 46% yield (Entry 6,
Table 1). The reactions in other aqueous organic solvents
are not competitive (Entries 7–9, Table 1).
The results of the iodolactonisation of 2,3-allenoates
with I2 under this set of standard reaction conditions are
summarised in Table 2. It should be noted that the reaction
affords 3-iodobutenolides in good to excellent yields and
also that the reaction scope is very wide: R1 can be alkyl or
aryl, R2 can be H or ethyl, and R3 can be H, alkyl, or
benzyl; 4-monosubstituted, 2,4-disubstituted, or 2,2,4-tri-
substituted 2,3-allenoates can be iodolactonized to afford
products 4 in moderate to high yields. Even the reaction
Results and Discussion
Synthesis of Starting Materials
The starting 2,3-allenoates were prepared according to
the Wittig-type reaction of ylides 1 with acyl chlorides 2
(Scheme 1).
[a] Laboratory of Molecular Recognition and Synthesis, Depart-
ment of Chemistry, Zhejiang University,
310027 Hangzhou, Zhejiang, P. R. China
[b] State Key Laboratory of Organometallic Chemistry, Shanghai
Institute of Organic Chemistry, Chinese Academy of Sciences,
354 Fenglin Lu, Shanghai 200032, P. R. China
Fax: +86-21-6416-7510
E-mail: masm@mail.sioc.ac.cn
3942
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejoc.200500296
Eur. J. Org. Chem. 2005, 3942–3945

4-Iodofuran-2(5H)-ones by Iodolactonisation of 2,3-Allenoates with I2
FULL PAPER
cedures.[16] Compounds 3c, 3h, 3e, 3k and 3l were prepared as fol-
lows.
Table 1. Iodolactonisation reaction of 3a under different condi-
tions.[a]
Ethyl Undeca-2,3-dienoate (3c). Typical Procedure: NEt3 (7.6 mL,
55 mmol) was added at 0 °C to a solution of 1a (17.4 g, 50 mmol) in
dichloromethane (20 mL). After 5 min at 0 °C, a solution of acetyl
chloride (2c; 11.47 g, 65 mmol) in dichloromethane (15 mL) was
added dropwise at 0 °C with stirring, and the solution was stirred
at room temp. overnight. After evaporation of the solvent, the resi-
due was treated with 80 mL of diethyl ether and then filtered. This
process was repeated until no further OPPh3 precipitated. After
concentration, the residue was purified by flash chromatography
on silica gel (petroleum ether/ethyl acetate = 50:1) to afford 7.48 g
(71%) of ethyl undeca-2,3-dienoate (3c) as an oil. 1H NMR
(400 MHz, CDCl3): δ = 5.53(m, 2 H), 4.16 (q, J = 7.2 Hz, 2 H),
2.10 (dq, J = 7.2 Hz and 3.2 Hz, 2 H), 1.42–1.47 (m, 2 H), 1.22–
1.36 (m, 11 H), 0.85 (t, J = 6.8 Hz, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 212.3, 166.2, 95.3, 88.2, 60.6, 31.7, 29.0, 28.8, 28.7,
Entry
Solvent
Time
[h]
Yield of 4a
[%][b]
1
2
3
CH3CN/H2O (4:1)
CH3CN/H2O (20:1)
CH3CN/H2O (12:1)
CH3CN/H2O (15:1)
CH3CN/H2O (15:1)
CH3CN
CH3CN/EtOH (2:1)
Acetone/H2O (15:1)
THF/H2O (15:1)
CH3CN/H2O (12:1)
2
26
10
20
19
43
11.5
18
19
21
61
67
70
71
63
46
48
36
39
48
4
5[c]
6
7[d]
8
9
27.4, 22.6, 14.2, 14.0 ppm. IR (neat): ν = 1961, 1720, 1253, 1158.
˜
10[e]
HRMS: calcd. for C13H22NaO2 [M+ + Na] 233.1512; found
233.1508 cm–1.
[a] The reaction was conducted with 0.2–0.4 mmol of 3a and I2
(2 equiv.). [b] Isolated yield. [c] The reaction was conducted at
30 °C. [d] The reaction was conducted at 0–5 °C. [e] Substrate/I2 =
1:1.2.
The following compounds were prepared similarly.
Ethyl 2-Benzylocta-2,3-dienoate (3e): The reaction of 1d (17.5 g,
40 mmol), NEt3 (6.1 mL, 44 mmol) and 2b (8.0 g, 60 mmol) af-
1
forded 7.11 g (77%) of 3e as an oil. H NMR (400 MHz, CDCl3):
with 4-phenyl-2,3-alkadienoates 3j–l, which react with
CuBr2 to give the corresponding 4-bromobutenolides in
very low yields and selectivity,[8] afforded 4j–l smoothly.
δ = 7.08–7.21 (m, 5 H), 5.35–5.40 (m, 1 H), 4.05–4.14 (m, 2 H),
3.44–3.53 (m, 2 H), 1.94–1.99 (m, 2 H), 1.21–1.26 (m, 4 H), 1.17
(t, J = 7.2 Hz, 3 H), 0.80 (t, J = 7.2 Hz, 3 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 210.5, 167.2, 139.4, 128.8, 128.0, 126.0,
100.5, 95.2, 60.7, 35.3, 30.8, 27.5, 21.8, 14.1, 13.7 ppm. IR (neat):
Table 2. Cyclisation of I2 with 2,3-allenoates.[a]
ν = 1958, 1711, 1268, 1094 cm–1. MS (70 eV, EI): m/z (%) = 258
˜
(42.08) [M+], 91 (100). HRMS: calcd. for C17H22O2 258.1620;
found 258.1616.
Ethyl 2-Methylundeca-2,3-dienoate (3h): The reaction of 1b (21.7 g,
60 mmol), NEt3 (9.2 mL, 66 mmol) and 2c (15.9 g, 90 mmol) af-
forded 13.19 g (98%) of 3h as an oil. 1H NMR (400 MHz, CDCl3):
δ = 5.36–5.42 (m, 1 H), 4.10–4.16 (m, 2 H), 2.05 (q, J = 7.2 Hz, 2
H), 1.81 (d, J = 2.8 Hz, 3 H), 1.35–1.43 (m, 2 H), 1.19–1.32 (m, 11
H), 0.84 (t, J = 7.2 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 210.0, 168.0, 95.5, 93.7, 60.6, 31.8, 29.0, 28.81, 28.75, 27.9,
Entry
3
Time
[h]
Yield of 4
R1
R2
R3
[%][b]
1
2
3
4
5
6
7
8
9
10
11
12
13
n-C3H7
n-C4H9
n-C7H15
n-C3H7
n-C4H9
n-C3H7
n-C4H9
n-C7H15
CH3
Ph
Ph
Ph
CH3
H
H
H
H
H
H
H
H
CH3
H
H (3a)
H (3b)
20
12
14
11
14
10
16
3
3
3
0.7
0.7
12
71 (4a)
65 (4b)
69 (4c)
78 (4d)
72 (4e)
88 (4f)
89 (4g)
91 (4h)
77 (4i)
83 (4j)
94 (4k)
81 (4l)
60 (4m)
H (3c)
Bn (3d)
22.6, 15.2, 14.2, 14.0 ppm. IR (neat): ν = 1960, 1712, 1270,
˜
Bn (3e)
1121 cm–1. MS (70 eV, EI): m/z (%) = 224 (1.89) [M+], 112 (100).
CH3 (3f)
CH3 (3g)
CH3 (3h)
CH3 (3i)
CH3 (3j)
n-C3H7 (3k)
Bn (3l)
HRMS: calcd. for C14H24O2 224.1776; found 224.1774.
Ethyl 4-Phenyl-2-propylbuta-2,3-dienoate (3k): The reaction of 1c
(28.2 g, 60 mmol), NEt3 (18.4 mL, 132 mmol) and 2e (13.9 g,
90 mmol) afforded 9.03 g (65%) of 3k as an oil. 1H NMR
(400 MHz, CDCl3): δ = 7.17–7.26 (m, 5 H), 6.45 (t, J = 3.2 Hz, 1
H), 4.14 (q, J = 7.2 Hz, 2 H), 2.27–2.29 (m, 2 H), 1.45–1.47 (m, 2
H), 1.19 (t, J = 7.2 Hz, 3 H), 0.88 (t, J = 7.4 Hz, 3 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 212.0, 166.8, 132.7, 128.7, 127.6,
H
H
CH3
H (3m)
[a] The reaction was carried out using 0.2–0.4 mmol of the 2,3-
allenoate. [b] Isolated yield.
127.2, 104.4, 98.2, 61.0, 30.9, 21.3, 14.2, 13.8 ppm. IR (neat): ν =
˜
1943, 1712, 1460, 1251 cm–1. HRMS: calcd. for C15H16NaO2 [M+
+ Na] 253.1197; found 253.1199.
In conclusion, we have developed a convenient method
for the efficient synthesis of 4-iodobutenolides by the iodol-
actonisation of ethyl 2,3-allenoates with I2 in aqueous Ethyl 2-Benzyl-4-phenylbuta-2,3-dienoate (3l): The reaction of 1d
(10.38 g, 20 mmol), NEt3 (6.1 mL, 44 mmol) and 2e (3.40 g,
22 mmol) afforded 2.52 g (45%) of 3l as an oil. 1H NMR
(400 MHz, CDCl3): δ = 7.25–7.39 (m, 10 H), 6.57 (s, 1 H), 4.24–
4.29 (m, 2 H), 3.78 (s, 2 H), 1.27–1.32 (m, 3 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 212.9, 166.2, 139.0, 132.1, 128.9, 128.7,
128.2, 127.7, 127.2, 126.3, 104.2, 98.5, 61.1, 35.5, 14.1 ppm. IR
MeCN. Further studies in this area are being conducted in
our laboratory.
Experimental Section
Starting Materials: Compounds 3a,[11] 3b,[12] 3d,[8] 3f,[13] 3g,[13] (neat): ν = 1945, 1712, 1600, 1495, 1455 cm–1. HRMS: calcd. for
˜
3i,[14] 1j[13] and 1m[15] were prepared according to known pro-
C19H18NaO2 [M+ + Na] 301.1199; found 301.1191.
Eur. J. Org. Chem. 2005, 3942–3945
www.eurjoc.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3943

C. Fu, S. Ma
FULL PAPER
4-Iodo-5-propylfuran-2(5H)-one (4a). Typical Procedure: A solution
of 3a (81.9 mg, 0.53 mmol) and iodine (254 mg, 1 mmol) in 4 mL
of MeCN/H2O (15:1) was stirred at 16°C for 12 h. The mixture
was then quenched with 6 mL of water followed by the addition of
a saturated aqueous solution of Na2S2O3. This mixture was ex-
tracted with diethyl ether (3×25 mL), washed with NaCl and dried
with anhydrous Na2SO4. Concentration and column chromatog-
raphy on silica gel (petroleum ether/ethyl acetate = 20:1) afforded
4a (94.9 mg, 71%) as a white solid. M.p. 57–58°C (petroleum ether/
EI): m/z (%) = 266 (14.05) [M+], 139 (100). IR (KBr): ν = 1740,
˜
1639, 1462, 1275, 1083, 1010 cm–1. C8H11IO2 (266.1): calcd. C
36.11, H 4.17; found C 36.13, H 4.36.
5-Butyl-4-iodo-3-methylfuran-2(5H)-one (4g): The reaction of 3g
(91.9 mg, 0.5 mmol) and I2 254 mg (1 mmol) afforded 125.3 mg
(89%) of 4g as a white solid. M.p. 68–70°C (petroleum ether/di-
ethyl ether). 1H NMR (400 MHz, CDCl3): δ = 4.87–4.89 (m, 1 H),
2.04–2.07 (m, 1 H), 1.93 (s, 3 H), 1.56–1.60 (m, 1 H), 1.33 (m, 4
H), 0.88–0.94 (m, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
170.5, 135.7, 121.6, 85.5, 34.4, 25.8, 22.3, 13.9, 12.8 ppm. IR (KBr):
1
diethyl ether) (ref.[7] 58–59°C). H NMR (400 MHz, CDCl3): δ =
6.45 (s, 1 H), 4.89–4.92 (m, 1 H), 1.67–1.98 (m, 1 H), 1.50–1.55 (m,
1 H), 1.35–1.42 (m, 2 H), 0.91 (t, J = 6 Hz, 3 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 171.1, 129.9, 125.5, 87.9, 34.6, 17.3,
13.7 ppm. MS (70 eV, EI): m/z (%) = 253 (100) [M+ + 1]. IR (KBr):
ν = 1739, 1640, 1466, 1273, 1088, 1039 cm–1. MS (70 eV, EI): m/z
˜
(%) = 281 (97.9) [M+ + 1], 41 (100). C9H13IO2 (280.1): calcd. C
38.59, H 4.68; found C 38.55, H 4.66.
ν = 1738, 1582, 1296, 1168 cm–1.
5-Heptyl-4-iodo-3-methylfuran-2(5H)-one (4h): The reaction of 3h
(88.2 mg, 0.4 mmol) and I2 (203 mg, 0.8 mmol) afforded 115.6 mg
(91%) of 4h as a white solid. M.p. 83–84°C (petroleum ether/di-
ethyl ether). 1H NMR (400 MHz, CDCl3): δ = 4.84–4.88 (m, 1 H),
2.00–2.04 (m, 1 H), 1.91 (s, 3 H), 1.55–1.57 (m, 1 H), 1.25–1.34 (m,
10 H), 0.85–0.91 (m, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ
= 170.6, 135.7, 121.5, 85.6, 32.8, 31.7, 29.1, 29.0, 23.7, 22.6, 14.1,
12.8 ppm. MS (70 eV, EI): m/z (%) = 322 (5.93) [M+ + 1], 41 (100).
˜
The following compounds were prepared similarly.
5-Butyl-4-iodofuran-2(5H)-one (4b): The reaction of 3b (84.6 mg,
0.5 mmol) and I2 (256.7 mg, 1 mmol) afforded 86.4 mg (65%) of 4b
as a white solid. M.p. 61–62°C (petroleum ether/diethyl ether)
(ref.[5b] 62–63°C, n-hexane). 1H NMR (400 MHz, CDCl3): δ = 6.52
(s, 1 H), 4.96–4.98 (m, 1 H), 2.02–2.08 (m, 1 H), 1.58–1.64 (m, 1
H), 1.37–1.42 (m, 4 H), 0.92 (t, J = 8 Hz, 3 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 171.2, 130.0, 125.5, 88.0, 32.2, 25.7, 22.3,
13.8 ppm.
IR (KBr): ν = 1735, 1640, 1276, 1088 cm–1. C H IO (322.2):
˜
12 19
2
calcd. C 44.74, H 5.94; found C 44.80, H 6.07.
4-Iodo-3,5,5-trimethylfuran-2(5H)-one (4i): The reaction of 3i
(79.3 mg, 0.51 mmol) and I2 254 mg (1 mmol) afforded 99.7 mg
(77%) of 4i as a white solid. M.p 138–140°C (petroleum ether/
5-Heptyl-4-iodofuran-2(5H)-one (4c): The reaction of 3c (63.6 mg,
0.3 mmol) and I2 (152.4 mg, 0.6 mmol) afforded 63.4 mg (69%) of
4c as a white solid. M.p. 78–79°C (petroleum ether/diethyl ether)
(ref.[5b] 78–79°C, n-hexane). 1H NMR (400 MHz, CDCl3): δ = 6.45
(s, 1 H), 4.89–4.91 (m, 1 H), 1.70–2.02 (m, 1 H), 1.49–1.56 (m, 1
H), 1.20–1.33 (m, 10 H), 0.82 (t, J = 6 Hz, 3 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 171.2, 130.0, 125.5, 88.0, 32.5, 31.7, 29.1,
29.0, 23.7, 22.6, 14.1 ppm.
1
diethyl ether) (ref.[7] 140–141°C). H NMR (400 MHz, CDCl3): δ
= 1.89 (s, 3 H), 1.45 (s, 6 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 170.2, 134.6, 129.5, 88.0, 25.8, 13.1 ppm. IR (KBr): ν = 1734,
˜
1640, 1288, 1080 cm–1. MS (70 eV, EI): m/z (%) = 252 (14.84) [M+],
43 (100).
4-Iodo-3-methyl-5-phenylfuran-2(5H)-one (4j): The reaction of 3j
(82.5 mg, 0.41 mmol) and I2 (202 mg, 0.80 mmol) afforded
102.1 mg (83%) of 4j as a white solid. M.p. 93–94°C (petroleum
ether/diethyl ether) (ref.[10] 93–94°C, n-hexane). 1H NMR
(400 MHz, CDCl3): δ = 7.40–7.42 (m, 3 H), 7.24–7.25 (m, 2 H),
5.75 (s, 1 H), 2.02 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ
= 170.7, 135.5, 133.6, 129.8, 128.9, 127.6, 122.2, 87.6, 13.0 ppm.
3-Benzyl-4-iodo-5-propylfuran-2(5H)-one (4d): The reaction of 3d
(76.1 mg, 0.31 mmol) and I2 (156 mg, 0.61 mmol) afforded 82.4 mg
(78%) of 4d as a white solid. M.p. 87–88°C (petroleum ether/di-
ethyl ether). 1H NMR (400 MHz, CDCl3): δ = 7.12–7.25 (m, 5 H),
4.79–4.80 (m, 1 H), 3.53–3.61 (m, 2 H), 1.86–1.99 (m, 1 H), 1.42–
1.47 (m, 1 H), 1.30–1.36 (m, 2 H), 0.85 (t, J = 8 Hz, 3 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 170.1, 138.3, 136.5, 128.8, 128.6,
126.9, 122.6, 85.5, 34.9, 33.1, 17.3, 13.7 ppm. MS (70 eV, EI): m/z
4-Iodo-5-phenyl-3-propylfuran-2(5H)-one (4k): The reaction of 3k
(94.0 mg, 0.40 mmol) and I2 206.8 mg (0.80 mmol) afforded
125.5 mg (94%) of 4k as a white solid. M.p. 102–104°C (petroleum
ether/diethyl ether) (ref.[5b] 104–105°C, n-hexane). 1H NMR
(400 MHz, CDCl3): δ = 7.40–7.41 (m, 3 H), 7.22–7.24 (m, 2 H),
5.73 (s, 1 H), 2.40 (t, J = 7.2 Hz, 2 H), 1.63–1.69 (m, 2 H), 0.99 (t,
J = 7.6 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 170.1,
138.9, 133.8, 129.7, 128.9, 127.5, 122.0, 87.4, 29.2, 20.6, 13.8 ppm.
(%) = 342 (15.71) [M+], 129 (100). IR (KBr): ν = 1739, 1633, 1494,
˜
1451, 1192 cm–1. C14H15IO2 (342.2): calcd. C 49.14, H 4.42; found
C 49.19, H 4.52.
3-Benzyl-5-butyl-4-iodofuran-2(5H)-one (4e): The reaction of 3e
(79.3 mg, 0.307 mmol) and I2 (152.6 mg, 0.6 mmol) afforded
78.4 mg (72%) of 4e as a white solid. M.p. 92–93°C (petroleum
ether/diethyl ether). 1H NMR (400 MHz, CDCl3): δ = 7.21–7.34
(m, 5 H), 4.78–4.80 (m, 1 H), 3.59 (d, J = 11.2 Hz, 1 H), 3.56 (d,
J = 11.2 Hz, 1 H), 1.96–1.99 (m, 1 H), 1.49–1.53 (m, 1 H), 1.26 (m,
4 H), 0.81 (t, J = 5 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ
= 170.0, 138.3, 136.5, 128.8, 128.6, 126.9, 122.5, 85.6, 33.1, 32.5,
IR (KBr): ν = 1758, 1635, 1493, 1454 cm–1. MS (70 eV, EI): m/z
˜
(%) = 328 (6.17) [M+], 105 (100).
3-Benzyl-4-iodo-5-phenylfuran-2(5H)-one (4l): The reaction of 3l
(84.2 mg, 0.30 mmol) and I2 153.9 mg (0.60 mmol) afforded
91.9 mg (81%) of 4l as a white solid. M.p. 100–102°C (petroleum
ether/diethyl ether). 1H NMR (400 MHz, CDCl3): δ = 7.16–7.38
(m, 10 H), 5.72 (s, 1 H), 3.76 (d, J = 14.4 Hz, 1 H), 3.69 (d, J =
14.4 Hz, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 170.1, 138.1,
136.4, 133.6, 129.9, 129.0, 128.9, 128.7, 127.6, 127.0, 122.9, 87.7,
25.8, 22.3, 13.8 ppm. MS (70eV, EI): m/z (%) = 357 (8.50) [M+
+
1], 115 (100). IR (KBr): ν = 3029, 1760, 1635, 1495, 1061 cm–1.
˜
HRMS: calcd. for C15H17IO2 356.02733; found 356.02289.
4-Iodo-3-methyl-5-propylfuran-2(5H)-one (4f): The reaction of 3f
(83.5 mg, 0.5 mmol) and I2 (254.9 mg, 1 mmol) afforded 116.2 mg
(88%) of 4f as a white solid. M.p. 63–65°C (petroleum ether/diethyl
ether). 1H NMR (400 MHz, CDCl3): δ = 4.84–4.86 (m, 1 H), 1.96–
2.02 (m, 1 H), 1.90 (s, 3 H), 1.50–1.53 (m, 1 H), 1.37–1.47 (m, 2
H), 0.93 (t, J = 8 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ
= 170.6, 135.6, 121.6, 85.4, 34.9, 17.3, 13.7, 12.8 ppm. MS (70 eV,
33.3 ppm. IR (KBr): ν = 1761, 1633, 1602, 1495, 1455 cm–1. MS
˜
(70 eV, EI): m/z (%) = 376 (4.52) [M+], 203 (100). HRMS: calcd.
for C17H13IO2 375.99603; found 375.99608.
4-Iodo-5,5-dimethylfuran-2(5H)-one (4m): The reaction of 3m
(71.2 mg, 0.5 mmol) and I2 257.4 mg (1.02 mmol) afforded 71.0 mg
(60%) of 4m as a white solid. M.p. 120–122°C (petroleum ether/
3944
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2005, 3942–3945

4-Iodofuran-2(5H)-ones by Iodolactonisation of 2,3-Allenoates with I2
FULL PAPER
diethyl ether). 1H NMR (400 MHz, CDCl3): δ = 6.37 (s, 1 H), 1.47
(s, 6 H) ppm. 13CNMR (400 MHz, CDCl3): δ = 170.4, 133.2, 129.1,
Appl. EP 372,940, 1990; Chem. Abstr. 1990, 113, 191137j; e) Y.
Ducharme, J. Y. Gauthier, P. Prasit, Y. Leblanc, Z. Wang, S.
Leger, M. Therien, PCT Int. Appl. WO 95 00,501, 1995; Chem.
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59197m.
90.5, 25.54 ppm. IR (KBr): ν = 1735, 1584, 1278, 1246 cm–1. MS
˜
(70 eV, EI): m/z (%) = 238 (33.73) [M+], 223 (100). HRMS: calcd.
for C6H7IO2 237.94908; found 237.94925.
[3] For an account, see: S. Ma, Acc. Chem. Res. 2003, 36, 701–
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Acknowledgments
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Financial support from the National Natural Science Foundation
of China, the Major State Basic Research Development Program
(grant no. G2000077500) and the Cheung Kong Scholar Pro-
gramme are greatly appreciated. Shengming Ma is jointly ap-
pointed by Zhejiang University and Shanghai Institute of Organic
Chemistry. This work was conducted at Zhejiang University.
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Received: April 27, 2005
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Published Online: August 1, 2005
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3945