A novel one-pot sulfonyloxylactonization of alkenoic acids mediated by hypervalent iodine species generated in situ from ammonium iodide

Article abstract of DOI:10.1002/hlca.201300152

A novel and efficient one-pot procedure was designed for the sulfonyloxylactonization of alkenoic acids by the reaction of alkenoic acids with m-chloroperbenzoic acid and sulfonic acids in the presence of a catalytic amount of ammonium iodide in a mixture acetonitrile/2,2,2-trifluoroethanol (4: 1) at room temperature for 24 h, which provided the corresponding sulfonyloxy lactones in moderate-to-good yields. Copyright

Full text of DOI:10.1002/hlca.201300152

Helvetica Chimica Acta – Vol. 97 (2014)
137
A Novel One-Pot Sulfonyloxylactonization of Alkenoic Acids Mediated by
Hypervalent Iodine Species Generated in situ from Ammonium Iodide
by Jiantao Hua), Min Zhub), Yuan Xua), and Jie Yan*a)
a) College of Chemical Engineering and Material Sciences, Zhejiang University of Technology,
Hangzhou 310032, P. R. China (fax: þ 86(571)88320238; e-mail: jieyan87@zjut.edu.cn)
b) College of Biological and Environmental Sciences, Zhejiang Shuren University, Hangzhou 310015,
P. R. China
A novel and efficient one-pot procedure was designed for the sulfonyloxylactonization of alkenoic
acids by the reaction of alkenoic acids with m-chloroperbenzoic acid and sulfonic acids in the presence of
a catalytic amount of ammonium iodide in a mixture acetonitrile/2,2,2-trifluoroethanol (4 :1) at room
temperature for 24 h, which provided the corresponding sulfonyloxy lactones in moderate-to-good yields.
Introduction. – To extend the scope of catalytic use of hypervalent iodine reagents
for organic synthesis, we have investigated the sulfonyloxylactonization of alkenoic
acid in the presence of a catalytic hypervalent iodine reagent [1], and we also developed
a novel one-pot method for preparation of a-tosyloxy ketones using a catalytic amount
of NH4I [2]. Herein, we report a novel sulfonyloxylactonization of alkenoic acids using
a catalytic amount of inorganic NH4I, which, to the best of our knowledge, has not been
reported before.
Results and Discussion. – At the beginning of our work, we investigated the
reaction of pent-4-enoic acid with m-chloroperbenzoic acid (MCPBA) and p-
toluenesulfonic acid monohydrate (TsOH · H2O) in the presence of catalytic amounts
of iodides in organic solvents at room temperature for 24 h. Generally, the reaction
proceeded well and afforded the desired product (Table 1).
In the light of the successful formation of 5-tosyloxypentano-4-lactone, the reaction
conditions were optimized, and the results are compiled in Table 1. It was realized that
solvents influenced the yield strongly, and when 1.0 equiv. of pent-4-enoic acid was
mixed with 1.0 equiv. of TsOH · H2O, 1.2 equiv. of MCPBA and 0.2 equiv. of NH4I in a
mixture MeCN/2,2,2-trifluoroethanol (TFE) 4 :1 at room temperature for 24 h, yields
of up to 49% were obtained (Entries 1 – 8). When more MCPBA was added, the yield
increased, and use of 2.0 equiv. of MCPBA resulted in a yield of 74% (Entries 8 – 12);
in contrast, in the absence of MCPBA, no product was observed (Entry 13). Other
oxidants such as potassium hydrogen persulfate (Oxoneꢀ) and NaBO3 · 4 H2O were also
studied; however, low yields were obtained (Entries 14 and 15). NaI and KI were
efficient providing moderate yields (Entries 16 and 17). The effect of the amount of
NH4I was also investigated, and 0.3 equiv. turned out to be the best choice (Entries 8,
10, 19 – 24). When I2 was used instead of NH4I, the product was obtained in 66% yield,
ꢁ 2014 Verlag Helvetica Chimica Acta AG, Zꢂrich

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Table 1. Optimization of the Sulfonyloxylactonization of Pent-4-enoic Acid
Entry
Solvent
Oxidant (equiv.)
Iꢀ (equiv.)
Yield [%]a)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
MeCN
TFE
MeOH
EtOH
THF
AcOEt
CH2Cl2
MCPBA (1.2)
MCPBA (1.2)
MCPBA (1.2)
MCPBA (1.2)
MCPBA (1.2)
MCPBA (1.2)
MCPBA (1.2)
MCPBA (1.2)
MCPBA (1.5)
MCPBA (2.0)
MCPBA (2.5)
MCPBA (3.0)
–
Oxone ꢀ (2.0)
NaBO3 · 4 H2O (2.0)
MCPBA (2.0)
MCPBA (2.0)
MCPBA (2.0)
MCPBA (1.2)
MCPBA (1.2)
MCPBA (2.0)
MCPBA (2.0)
MCPBA (2.0)
MCPBA (2.0)
MCPBA (2.0)
NH4I (0.2)
NH4I (0.2)
NH4I (0.2)
NH4I (0.2)
NH4I (0.2)
NH4I (0.2)
NH4I (0.2)
NH4I (0.2)
NH4I (0.2)
NH4I (0.2)
NH4I (0.2)
NH4I (0.2)
NH4I (0.2)
NH4I (0.2)
NH4I (0.2)
NaI (0.2)
42
39
17
21
30
28
35
49
52
74
52
50
0
48
39
62
57
66
67
65
77
75
39
33
0
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
MeCN/TFE 4 : 1
KI (0.2)
I2 (0.2)
NH4I (0.3)
NH4I (0.4)
NH4I (0.3)
NH4I (0.4)
NH4I (0.1)
NH4I (0.05)
NH4I (0)
a) Yield of the isolated lactones.
which was somewhat low compared with that obtained using NH4I under the same
conditions (Entry 18).
With the optimal conditions in hand, and to assess their generality and applicability,
a series of alkenoic acids were investigated (Table 2).
It is obvious from Table 2 that the sulfonyloxylactonization was compatible with
most of the alkenoic acids, and the corresponding sulfonyloxy lactones were obtained in
moderate-to-good yields (Entries 1 – 7, 10, and 11). Similar treatment of but-3-enoic
acid and (E)-hex-3-enoic acid, only the unsaturated lactones were obtained, not the
1
desired sulfonylactones (Entries 12 and 13). The H-NMR analysis revealed that the
desired five-membered and four-membered lactones were first formed, and then
transformed to the unsaturated lactones by elimination during workup procedure.
Efforts for the preparation of the six-membered lactone using hex-5-enoic acid were
only partially successful: the 1H-NMR spectrum of the crude product indicated lactone
formation, but purification was not achieved. Interestingly, when camphor-10-sulfonic

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acid, an aliphatic sulfonic acid, was used instead of TsOH · H2O under similar
condition, the corresponding sulfonyloxy lactones were also obtained; however, the
yields were somewhat low (Entries 13 – 16). It was also found that alkenoic acids 1b and
1c usually resulted in the mixtures of diastereoisomers, and the ratios changed from
0.35 :0.65 to 0.25 :0.75 (Entries 2, 3, 8, 11, 15, and 16).
According to the above results, a plausible reaction pathway for the present
reaction is proposed in Scheme 1. Thus, NH4I is first oxidized to I2 and HOI with
MCPBA, and both of them react with alkenoic acid to form the iodolactone, which is
then transformed to the hypervalent iodine intermediate in situ by the continuing
oxidation, and finally the sulfonyloxy lactone is formed with sulfonic acid as
nucleophile in the following intermolecular nucleophilic substitution. To assess this
proposal, pent-4-enoic acid was first reacted with I2 and HOI [3], respectively, both
providing nearly quantitatively the iodolactone. Then, the reaction of the iodolactone
with sulfonic acids was examined (Scheme 2), with the result that, with only TsOH ·
H2O, the desired product of 5-tosyloxypentano-4-lactone was not detected after a
long reaction time. However, when MCPBA was added to the reaction mixture, 5-
tosyloxypentano-4-lactone was obtained in good yield. Therefore, the in situ-generated
hypervalent iodine intermediate was responsible for the reaction. Recently, Kang and
Gade reported another mechanism for an oxidative lactonization of alkenoic acids with
AcOOH, AcOH, and Ac2O in the absence of iodo species [4]. To identify that our
protocol does not conform to the mechanism described in [4], we conducted our
reaction in the absence of NH4I, and no corresponding sulfonyloxy lactone was
obtained (Table 1, Entry 25). We also examined the reaction of 4,5-epoxyhexanoic acid
with TsOH · H2O under our reaction conditions, but the desired sulfonyloxy lactone
Scheme 1. A Plausible Reaction Pathway

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Scheme 2. Identification of the Plausible Reaction Pathway
was not observed after a long reaction time. Therefore, it is obvious that our reaction
mechanism is different from that of Afonsoꢃs reaction [5].
In summary, we have developed a novel and efficient method for the sulfonyloxy-
lactonization of alkenoic acid using a catalytic amount of NH4I with MCPBA in MeCN/
TFE 4 :1 at room temperature. The presented results highlight the advantageous role of
inorganic iodide as catalyst and as a substitute for expensive aryl iodides. Moreover, it
extends the scope of hypervalent iodine reagents in organic synthesis, as well as being
more environmentally benign.
Experimental Part
General. Ammonium iodide (NH4I), m-chloroperbenzoic acid (MCPBA), alkenoic acids, and
sulfonic acids were commercially available. M.p.: XT-4 melting-point apparatus; uncorrected. IR
Spectra: Thermo Nicolet 6700 instrument. 1H- and 13C-NMR spectra: in CDCl3 on a Bruker Avance III
(500 MHz) spectrometer. MS: Thermo ITQ 1100 mass spectrometer.
Representative Procedure for the Catalytic Sulfonyloxylactonization of Alkenoic Acids Using a
Catalytic Amount of NH4I. To a mixture of MeCN (1.6 ml) and 2,2,2-trifluoroethanol (TFE; 0.4 ml),
alkenoic acid 1 (0.3 mmol), MCPBA (0.6 mmol), NH4I (0.09 mmol), and sulfonic acid 2 (0.3 mmol) were
added. The resulting mixture was stirred at r.t. for 24 h. Then, H2O (5 ml), sat. aq. Na2S2O3 (2 ml), and
sat. aq. Na2CO3 (2 ml), were poured into the mixture. The mixture was extracted with CH2Cl2 (3 ꢁ 5 ml),
and the combined org. layer was washed with brine, dried (Na2SO4), filtered, and concentrated under
reduced pressure. The residue was purified by prep. TLC (SiO2; AcOEt/hexane 3 :2) to give the pure
product 3.
(Tetrahydro-5-oxofuran-2-yl)methyl 4-Methylbenzenesulfonate (3a). Yield: 62 mg (77%). White
1
solid. M.p. 78 – 808 ([1]: 79 – 818). H-NMR: 7.78 (d, J ¼ 8.5, 2 H); 7.37 (d, J ¼ 8.5, 2 H); 4.72 – 4.65 (m,
1 H); 4.19 (dd, J ¼ 11.0, 3.0, 1 H); 4.13 (dd, J ¼ 11.0, 4.0, 1 H); 2.61 – 2.48 (m, 2 H); 2.46 (s, 3 H); 2.39 –
2.31 (m, 1 H); 2.15 – 2.10 (m, 1 H). 13C-NMR: 176.0; 145.4; 132.2; 130.0; 127.9; 76.4; 70.0; 27.8; 23.5; 21.6.
(Tetrahydro-4-methyl-5-oxofuran-2-yl)methyl 4-Methylbenzenesulfonate (3b). Yield: 54 mg (63%).
1
White solid. M.p. 93 – 958 ([1]: 91 – 958). H-NMR: 7.80 (dd, J ¼ 10.0, 5.0, 2 H); 7.37 (d, J ¼ 10.0, 2 H);
4.68 – 4.62 (m, 0.27 H); 4.58 – 4.52 (m, 0.73 H); 4.22 (dd, J ¼ 11.0, 3.5, 0.54 H); 4.15 – 4.11 (m, 1.46 H);
2.76 – 2.67 (m, 1 H); 2.51 – 2.35 (m, 1 H); 2.46 (s, 3 H); 2.06 – 2.03 (m, 0.27 H); 1.73 – 1.70 (m, 0.73 H);
1.27 (d, J ¼ 7.0, 3 H). 13C-NMR: 178.2; 145.4 (d, J ¼ 12.5); 132.3; 130.0 (d, J ¼ 6.3); 127.9 (d, J ¼ 6.3); 74.5;
74.1; 70.2; 69.4; 35.0; 33.6; 32.1; 31.7; 21.6; 16.0; 15.0.

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Helvetica Chimica Acta – Vol. 97 (2014)
(Tetrahydro-3-methyl-5-oxofuran-2-yl)methyl 4-Methylbenzenesulfonate (3c) [1]. Yield: 52 mg
1
(61%). Colorless oil. H-NMR: 7.80 (d, J ¼ 10.0, 2 H); 7.38 (d, J ¼ 10.0, 2 H); 4.62 – 4.59 (m, 0.34 H);
4.17 – 4.13 (m, 0.66 H); 4.22 – 4.17 (m, 2 H); 2.81 – 2.71 (m, 1 H); 2.64 – 2.59 (m, 0.34 H); 2.52 – 2.50 (m,
0.66 H); 2.46 (s, 3 H); 2.29 (dd, J ¼ 17.5, 8.0, 0.34 H); 2.19 (dd, J ¼ 17.5, 8.0, 0.66 H); 1.18 (d, J ¼ 10.0,
2 H); 1.12 (d, J ¼ 5.0, 1 H). 13C-NMR: 175.6; 175.2; 145.4 (d, J ¼ 6.3); 132.1 (d, J ¼ 23.8); 130.1 (d, J ¼
22.5); 127.9 (d, J ¼ 2.5); 82.9; 78.8; 68.6; 67.7; 36.2 (d, J ¼ 23.8); 31.8 (d, J ¼ 25.0); 21.6; 17.0; 13.5.
(Tetrahydro-4,4-dimethyl-5-oxofuran-2-yl)methyl 4-Methylbenzenesulfonate (3d). Yield: 70 mg
(78%). White solid. M.p. 99 – 1018. IR (film): 2977, 2934, 1787, 1459, 1355, 1210, 1188, 1136, 978.
1H-NMR: 7.79 (d, J ¼ 8.3, 2 H); 7.37 (d, J ¼ 8.2, 2 H); 4.66 – 4.57 (m, 1 H); 4.21 (dd, J ¼ 11.1, 3.5, 1 H);
4.09 (dd, J ¼ 11.1, 5.2, 1 H); 2.46 (s, 3 H); 2.13 (dd, J ¼ 12.9, 6.6, 1 H); 1.91 (dd, J ¼ 12.9, 9.7, 1 H); 1.26 (s,
3 H); 1.25 (s, 3 H). 13C-NMR: 180.7; 145.3; 132.4; 130.0; 127.9; 73.2; 69.6; 39.9; 38.5; 24.8; 24.7; 21.6. ESI-
MS: 299.1 (100, [M þ 1]þ). HR-MS: 299.0944 ([M þ 1]þ, C14H19O5Sþ; calc. 299.0948).
Hexahydro-2-oxo-2H-cyclopenta[b]furan-6-yl 4-Methylbenzenesulfonate (3e). Yield: 44 mg (50%).
Colorless oil. IR (film): 971, 2879, 1784, 1457, 1362, 1177, 1097, 984. 1H-NMR: 7.79 (d, J ¼ 8.3, 2 H); 7.37
(d, J ¼ 8.1, 2 H); 4.84 – 4.83 (m, 1 H); 4.80 (d, J ¼ 6.9, 1 H); 3.05 – 3.03 (m, 1 H); 2.79 (dd, J ¼ 18.6, 10.3,
1 H); 2.45 (s, 3 H); 2.24 (dd, J ¼ 18.7, 2.9, 1 H); 2.20 – 2.14 (m, 1 H); 1.91 – 1.87 (m, 2 H); 1.57 – 1.52 (m,
1 H). 13C-NMR: 76.0; 145.3; 133.1; 130.0; 127.8; 87.1; 84.5; 36.1; 35.0; 30.6; 29.8; 21.6. ESI-ES: 297.1 (100,
[M þ 1]þ). HR-MS: 297.0783 ([M þ 1]þ, C14H17O5Sþ; calc. 297.0791).
(Tetrahydro-5-oxofuran-2-yl)methyl 4-Chlorobenzenesulfonate (3f). Yield: 54 mg (62%). White
solid. M.p. 99 – 1008. IR (film): 3092, 2958, 1774, 1477, 1398, 1359, 1281, 1190, 1169, 1088, 967. 1H-NMR:
7.84 (d, J ¼ 8.7, 2 H); 7.56 (d, J ¼ 8.7, 2 H); 4.71 – 4.70 (m, 1 H); 4.24 (dd, J ¼ 11.1, 3.2, 1 H); 4.17 (dd, J ¼
11.1, 4.5, 1 H); 2.62 – 2.49 (m, 2 H); 2.40 – 2.33 (m, 1 H); 2.15 – 2.08 (m, 1 H). 13C-NMR: 175.8; 141.0;
133.8; 129.8; 129.4; 76.3; 70.4; 27.8; 23.4. ESI-MS: 291.0 (100, [M þ 1]þ). HR-MS: 291.0091 ([M þ 1]þ,
C11H12ClO5Sþ; calc. 291.0088).
(Tetrahydro-4-methyl-5-oxofuran-2-yl)methyl 4-Chlorobenzenesulfonate (3g). Yield: 52 mg (57%).
White solid. M.p. 118 – 1208. IR (film): 3095, 2996, 2938, 2879, 1768, 1457, 1370, 1283, 1181, 1144, 967.
1H-NMR: 7.87 (d, J ¼ 1.8, 1 H); 7.86 (d, J ¼ 1.8, 1 H); 7.57 (d, J ¼ 2.0, 1 H); 7.56 (d, J ¼ 1.8, 1 H); 4.59 –
4.55 (m, 1 H); 4.28 (dd, J ¼ 11.2, 3.3, 1 H); 4.15 (dd, J ¼ 11.2, 5.2, 1 H); 2.72 – 2.69 (m, 1 H); 2.52 – 2.47 (m,
1 H); 1.74 – 1.68 (m, 1 H); 1.28 (d, J ¼ 7.0, 3 H). 13C-NMR: 178.0; 141.0; 133.9; 129.8; 129.4; 74.4; 69.8;
35.1; 32.2; 15.1. ESI-MS: 305.0 (100, [M þ 1]þ). HR-MS: 305.0241 ([M þ 1]þ, C12H14ClO5Sþ; calc.
305.0245).
(Tetrahydro-3-methyl-5-oxofuran-2-yl)methyl 4-Chlorobenzenesulfonate (3h). Yield: 42 mg (46%).
1
Colorless oil. IR (film): 3093, 2969, 1788, 1477, 1368, 1280, 1188, 1088, 970. H-NMR: 7.85 (d, J ¼ 8.7,
2 H); 7.56 (d, J ¼ 7.3, 2 H); 4.65 – 4.55 (m, 0.3 H); 4.27 – 4.17 (m, 0.7 H); 2.82 – 2.78 (m, 0.3 H); 2.73 (dd,
J ¼ 17.7, 8.7, 0.7 H); 2.63 (dd, J ¼ 17.4, 8.6, 0.3 H); 2.50 – 2.46 (m, 0.7 H); 2.27 (dd, J ¼ 17.4, 7.8, 0.3 H); 2.20
(dd, J ¼ 17.7, 8.5, 0.7 H); 1.18 (d, J ¼ 6.8, 0.9 H); 1.12 (d, J ¼ 7.1, 2.1 H). 13C-NMR: 175.0; 141.0; 133.8;
129.8 (d, J ¼ 2.2); 129.4 (d, J ¼ 2.4); 82.8; 78.7; 68.9; 68.2; 36.3; 36.1; 31.9; 31.8; 17.9; 13.6. ESI-MS: 322.0
(100, [M þ NH4]þ). HR-MS: 322.051 ([M þ NH4]þ, C12H17NClO5Sþ; calc. 322.0516).
Hexahydro-2-oxo-2H-cyclopenta[b]furan-6-yl 4-Chlorobenzenesulfonate (3i). Yield: 41 mg (43%).
1
Colorless oil. IR (film): 3093, 2968, 1784, 1477, 1368, 1281, 1181, 1088, 983. H-NMR: 7.87 (d, J ¼ 8.6,
2 H); 7.56 (d, J ¼ 8.5, 2 H); 4.89 – 4.87 (m, 1 H); 4.82 (d, J ¼ 7.0, 1 H); 3.07 – 3.05 (m, 1 H); 2.81 (dd, J ¼
18.7, 10.3, 1 H); 2.27 (dd, J ¼ 18.7, 2.9, 1 H); 2.21 – 2.17 (m, 1 H); 1.96 – 1.90 (m, 2 H); 1.59 – 1.54 (m, 1 H).
13C-NMR: 175.9; 140.9; 134.7; 129.9; 129.3; 87.0; 85.2; 36.2; 35.0; 30.6; 30.0. ESI-MS: 339.0 (100, [M þ
Na]þ). HR-MS: 339.0061 ([M þ Na]þ, C13H13ClNaO5Sþ; calc. 339.0070).
(Tetrahydro-5-oxofuran-2-yl)methyl Benzenesulfonate (3j). Yield: 46 mg (60%). Colorless oil. IR
(film): 2957, 1781, 1449, 1362, 1181, 1096, 957. 1H-NMR: 7.88 – 7.86 (m, 2 H); 7.68 – 7.65 (m, 1 H); 7.57 –
7.54 (m, 2 H); 4.69 – 4.65 (m, 1 H); 4.20 (dd, J ¼ 11.1, 3.2, 1 H); 4.12 (dd, J ¼ 11.2, 4.6, 1 H); 2.57 – 2.48 (m,
2 H); 2.35 – 2.28 (m, 1 H); 2.09 – 2.03 (m, 1 H). 13C-NMR: 176.0; 135.1; 134.1; 129.3; 127.7; 76.3; 70.2;
27.7; 23.2. ESI-MS: 279.0 (100, [M þ Na]þ). HR-MS: 279.0301 ([M þ Na]þ, C11H12NaO5Sþ; calc.
279.0303).
(Tetrahydro-4-methyl-5-oxofuran-2-yl)methyl Benzenesulfonate (3k). Yield: 53 mg (66%). Colorless
1
oil. IR (film): 3068, 2977, 2881, 1775, 1450, 1362, 1292, 1189, 1096, 972. H-NMR: 7.87 – 7.83 (m, 2 H);
7.66 – 7.63 (m, 1 H); 7.55 – 7.52 (m, 2 H); 4.64 – 4.60 (m, 0.35 H); 4.55 – 4.50 (m, 0.65 H); 4.21 (dd, J ¼ 11.3,

Helvetica Chimica Acta – Vol. 97 (2014)
145
3.1, 0.65 H); 4.15 (dd, J ¼ 11.0, 3.2, 0.35 H); 4.11 – 4.03 (m, 1 H); 2.73 – 2.59 (m, 1 H); 2.45 – 2.40 (m,
0.65 H); 2.32 – 2.27 (m, 0.35 H); 1.98 – 1.95 (m, 0.35 H); 1.66 – 1.59 (m, 0.65 H); 1.18 (d, J ¼ 2.6, 3 H).
13C-NMR: 178.9; 178.1; 135.2; 135.1; 134.1 (d, J ¼ 8.4); 129.3 (d, J ¼ 5.9); 127.6 (d, J ¼ 4.7); 74.4; 74.0;
70.5; 69.7; 34.8; 33.4; 31.8; 31.4; 15.8; 14.8. ESI-MS: 288.1 (100, [M þ NH4]þ). HR-MS: 288.092 ([M þ
NH4]þ, C12H18NO5Sþ; calc. 288.0906).
1
Furan-2(5H)-one (3l) [6]. Yield: 16 mg (63%). Colorless oil. H-NMR: 7.61 – 7.59 (m, 1 H); 6.19 –
6.17 (m, 1 H); 4.93 – 4.92 (m, 2 H). 13C-NMR: 173.6; 152.7; 121.6; 72.1.
5-Ethylfuran-2(5H)-one (3m) [6]. Yield: 26 mg (75%). Colorless oil. 1H-NMR: 7.47 – 7.45 (m, 1 H);
6.14 – 6.12 (m, 1 H); 5.03 – 5.00 (m, 1 H); 1.88 – 1.82 (m, 1 H); 1.77 – 1.70 (m, 1 H); 1.02 (t, J ¼ 1.9, 3 H).
13C-NMR: 173.1; 155.9; 121.8; 84.3; 26.3; 9.0.
(Tetrahydro-5-oxofuran-2-yl)methyl [(1S,4R)-7,7-Dimethyl-2-oxobicyclo[2.2.1]hept-1-yl]methansul-
1
fonate (3n) [7]. Yield: 42 mg (42%). Colorless oil. H-NMR: 4.82 – 4.79 (m, 1 H); 4.51 (ddd, J ¼ 22.0,
11.5, 3.0, 1 H); 4.37 (ddd, J ¼ 21.5, 11.0, 4.5, 1 H); 3.62 (dd, J ¼ 15.5, 6.0, 1 H); 3.08 (dd, J ¼ 15.0, 4.0,
1 H); 2.69 – 2.52 (m, 2 H); 2.43 – 2.37 (m, 3 H); 2.20 – 2.02 (m, 3 H); 1.97 (d, J ¼ 17.5, 1 H); 1.75 – 1.65 (m,
1 H); 1.51 – 1.45 (m, 1 H); 1.10 (s, 3 H); 0.88 (s, 3 H). 13C-NMR: 214.2; 176.1; 76.7 (d, J ¼ 7.5); 70.1; 69.9;
57.8 (d, J ¼ 2.5); 48.1; 47.2; 42.6 (d, J ¼ 2.5); 42.4 (d, J ¼ 1.3); 27.9; 26.8; 24.8 (d, J ¼ 7.5); 23.3 (d, J ¼
8.8); 19.5 (t, J ¼ 2.5).
(Tetrahydro-4-methyl-5-oxofuran-2-yl)methyl [(1S,4R)-7,7-Dimethyl-2-oxobicyclo[2.2.1]hept-1-yl]-
1
methanesulfonate (3o) [7]. Yield: 39 mg (38%). Colorless oil. H-NMR: 4.79 – 4.72 (m, 0.25 H); 4.68 –
4.62 (m, 0.75 H); 4.51 (ddd, J ¼ 19.0, 11.5, 3.0, 1 H); 4.37 – 4.31 (m, 1 H); 3.66 – 3.59 (m, 1 H); 3.09 –
3.03 (m, 1 H); 2.83 – 2.78 (m, 0.25 H); 2.77 – 2.70 (m, 0.75 H); 2.56 – 2.49 (m, 1 H); 2.46 – 2.37 (m,
2 H); 2.16 – 2.13 (m, 1 H); 2.10 – 2.03 (m, 1 H); 1.97 (d, J ¼ 18.0, 1 H); 1.79 – 1.68 (m, 2 H); 1.50 – 1.44 (m,
1 H); 1.31 (d, J ¼ 5.5, 2.25 H); 1.30 (d, J ¼ 6.0, 0.75 H); 1.10 (s, 2.25 H); 1.09 (s, 0.75 H); 0.89 (s, 2.25 H);
0.88 (s, 0.75 H). 13C-NMR: 214.4; 214.3; 179.2; 178.3; 74.9; 74.5 (d, J ¼ 7.5); 70.5; 70.4; 69.7; 69.4; 57.9 (d,
J ¼ 3.8), 48.2 (d, J ¼ 3.8); 47.4; 47.3 (d, J ¼ 6.3); 42.7; 42.5 (d, J ¼ 2.5); 35.2; 33.7; 32.2 (d, J ¼ 8.8); 31.6
(d, J ¼ 6.3); 26.9; 24.9 (t, J ¼ 3.8); 19.6 (d, J ¼ 5.0); 16.1; 15.1 (d, J ¼ 3.8).
(Tetrahydro-3-methyl-5-oxofuran-2-yl)methyl [(1S,4R)-7,7-Dimethyl-2-oxobicyclo[2.2.1]hept-1-yl]-
1
methanesulfonate (3p) [7]. Yield: 33 mg (32%). Colorless oil. H-NMR: 4.75 – 4.30 (m, 3 H); 3.63 (dd,
J ¼ 15.0, 4.5, 1 H); 3.07 (dd, J ¼ 15.5, 4.0, 1 H); 2.85 – 2.78 (m, 1 H); 2.72 – 2.66 (m, 0.68 H); 2.56 – 2.49
(m, 0.32 H); 2.45 – 2.22 (m, 3 H); 2.15 – 2.13 (m, 1 H); 2.11 – 2.02 (m, 1 H); 1.97 (d, J ¼ 18.5, 1 H); 1.75 –
1.65 (m, 1 H); 1.51 – 1.44 (m, 1 H); 1.23 (dd, J ¼ 6.5, 3.0, 0.96 H); 1.17 (d, J ¼ 7.5, 2.04 H); 1.10 (s, 3 H);
0.88 (s, 3 H). 13C-NMR: 214.3; 175.7 (d, J ¼ 2.5); 175.4; 83.3 (d, J ¼ 2.5); 79.2 (d, J ¼ 5.0); 68.8; 68.6;
68.2; 68.0; 57.9 (d, J ¼ 3.8); 48.2; 47.4 (d, J ¼ 3.8); 47.2 (d, J ¼ 2.5); 42.7 (d, J ¼ 3.8); 42.5 (d, J ¼ 2.5);
36.4 (d, J ¼ 3.8); 36.2; 31.9; 31.8; 31.7; 26.9; 24.9 (d, J ¼ 2.5); 24.8; 19.6 (d, J ¼ 3.8); 18.0; 13.5.
Financial supports from the Natural Science Foundation of China (Project 21072176) and the
Zhejiang Province Natural Science Foundation of China (Project Y4100231) are greatly appreciated.
REFERENCES
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[4] Y.-B. Kang, L. H. Gade, J. Org. Chem. 2012, 77, 1610.
[5] A. A. Rosatella, C. A. M. Afonso, Adv. Synth. Catal. 2011, 353, 2920.
[6] M. Shah, M. J. Taschner, G. F. Koser, N. L. Rach, Tetrahedron Lett. 1986, 27, 4557.
[7] M. Zhu, N.-B. Sun, H. Li, J. Yan, J. Heterocycl. Chem. 2010, 47, 436.
Received April 11, 2013