Facile oxidative conversion of alcohols to esters using molecular iodine

Article abstract of DOI:10.1016/j.tet.2005.03.097

A simple, efficient, and high-yield procedure for the oxidative conversion of alcohols to various types of esters and ketones, with molecular iodine and potassium carbonate was successfully carried out.

Full text of DOI:10.1016/j.tet.2005.03.097

Tetrahedron 61 (2005) 5915–5925
Facile oxidative conversion of alcohols to esters using
molecular iodine
Naoshi Moria and Hideo Togoa,b,
*
aGraduate School of Science and Technology, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba 263-8522, Japan
bDepartment of Chemistry, Faculty of Science, Chiba University, Yayoi-cho 1-33, Inage-ku, Chiba 263-8522, Japan
Received 25 February 2005; accepted 18 March 2005
Available online 10 May 2005
Abstract—A simple, efficient, and high-yield procedure for the oxidative conversion of alcohols to various types of esters and ketones, with
molecular iodine and potassium carbonate was successfully carried out.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
1.1. Oxidation of alcohols
as Na2Cr2O7/H2SO4,8a PCC/Al2O3,8b and with oxo-
ammonium salt.9 However, these reactions have drawbacks
from a practical point of view, that is, the reaction requires
high temperature, yield of the esters is not high, or the
alcohols used are limited.
Oxidation of alcohols with less toxic reagents is very
important in organic synthesis. Therefore, it has been
intensively studied and numerous reagents and methods
have been developed.1
1.2. Oxidation of aldehydes
It is often required to transform aldehydes directly into
esters during various stages in organic synthesis and natural
product synthesis.10 The oxidation of aldehydes to
carboxylic acids or esters is one of the most frequently
encountered reactions in organic chemistry. Such a process
has been accomplished in a variety of ways. Two-step
methods include the oxidation of hemiacetals,11 acetals,12
cyanohydrins,13 etc. Conversion of aldehydes to the methyl
esters or acids by NaOCl,14a t-BuOCl,14b and Ca(OCl)214c is
effective; however, activated aromatic aldehydes gave
lower yield of the products, because of the ring chlorination.
Generally, one-pot or one-step methods reported require the
use of heavy-metal oxidants such as KMnO4,15 PDC,16 or
the very expensive silver,17 rhodium,18 ruthenium,19 or
Oxidation with molecular halogens and related reagents is
attractive due to the simple operation and low cost. To date,
halogen-mediated oxidation of alcohols to aldehydes, esters,
and ketones with aqueous NaOCl,2 Ca(OCl)2/AcOH,3a,b
t-BuOCl/Py,3c Cl2-dimethyl sulfide,4a,b,e Cl2-dimethyl
sulfoxide,4c Cl2-pyridine,4d Cl2-HMPT or Br2-HMPT,4f,g
Br2/KBr,5a Br2 and HOBr,5b NaBrO2,5c NaBrO3,5d PhCH2-
NCMe3BrK3 ,5e NaBr/CH3CO3H,5f PhIO/KBr,5g and
PyHCBrK3 5h has been well studied. However, these methods
still have several drawbacks such as strong oxidative
conditions, or acidic or basic conditions.
Direct oxidative condensation of primary alcohols to the
corresponding esters, where both the acid and the alcohol
portion of the esters are derived from the alcohols, is
interesting and useful.6 Therefore, extensive study has been
carried out as follows: oxidative condensation with metal
catalysts such as ruthenium or palladium; Ru3(CO)12,7a
RuH2(Ph3P)4,7b,c PdCl2,7d,e Pd(OAc)2,7f PhCH2NCMe3Br4-
MoOK,7g under heating conditions, with chromic acids such
vanadium20 catalysts. Oxidation using NaClO2/H2O2 is
21
the most common method. NIS-mediated oxidation,22
electrochemical oxidation,23 as well as very recently using
cat. V2O5/H2O2,24a cat. QHSO4/H2O2,24b cat. S$SnO2/
H2O2,24c and the conversion of aldehydes into glycol
monoesters with Al2O3/MeSO3H,25 also have been
reported.
Keywords: Molecular iodine; Oxidation; Alcohol; Aldehyde; 2,2,2-
Trifluoroethyl ester; Methyl ester; Condensed ester; Ketone.
Most of the reported methods are useful for oxidation of
aldehydes into the corresponding esters. However, conver-
sion of aldehydes with a stoichiometrical amount of
*
Corresponding author. Fax: C81 43 290 2792;
e-mail: togo@faculty.chiba-u.jp
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.03.097

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N. Mori, H. Togo / Tetrahedron 61 (2005) 5915–5925
Table 1. Oxidation of p-methylbenzyl alcohol with I2/K2CO3 in protic polar solvents
Entry
I2/K2CO3 (equiv)
ROH (pKa)
Time (h)
Yields (%)
If
2f
Xf
1
2
3
4
5
6
7
8
9
5/5
5/5
5/5
5/5
3/3
5/0
5/5
5/5
5/5
(CH3)3COH (18.0)
CH3CH2OH (15.9)
CH3OH (16.0)
H2O (15.7)
CF3CH2OH (12.4)
CF3CH2OH
CF3CH2OH
19
14
24
21
18
18
14
18a
14
0
90
30
0
0
100
0
87
10
4
47
16
0
6
5
24
7 (RZH)
0
66 (4f)
53 (RZH)
83 (3f)
0
85 (3f)
91 (3f)
0
CF3CH2OH
(CF3)2CHOH (9.2)
0
76
a Half amount each of I2 and K2CO3 was added at first, and the rest was added later.
alcohols into esters with molecular iodine has been never
studied.
ketones by a simple procedure using molecular iodine and
potassium carbonate in protic polar solvents (i.e., 2,2,2-
trifluoroethanol, methanol, and t-butyl alcohol). To the best
of our knowledge, reports on the direct oxidative esterifica-
tion of primary alcohols with molecular iodine in such
alcoholic solvents have not yet appeared,29 while the
1.3. Oxidation with molecular iodine
Molecular iodine is a mild, cheap and easily available
oxidizing reagent, and, moreover, it is useful because of its
solid form and it is less toxic than molecular bromine or
chlorine. Previously, simple and effective conversion of
aldehydes to the corresponding methyl esters,26a,b car-
boxylic acids,26c and nitriles26d in the presence of molecular
iodine in methanol, in water/acetonitrile, and in ammonia
water, respectively, was reported. The Lieben iodoform
reaction, which is the reaction of methyl ketones with
Table 2. Oxidation of primary alcohols to 2,2,2-trifluoroethyl esters with
I2/K2CO3 in CF3CH2OH
molecular iodine in aqueous basic solution, is known for the
detection of the methyl ketone group.27
Entry
R–
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
3-O2NC6H4–
3,4-Cl2C6H3–
4-CF3C6H4–
4-ClC6H4–
1
80 (3a)
91 (3b)
87 (3c)
93 (3d)
78
91 (3e)
91 (3f)
83
85 (3g)
63
85 (3h)
93 (3i)
2a
Here, as a part of our basic study of molecular iodine for
organic synthesis,28 we would like to report a useful
oxidation of alcohols to the corresponding esters and
4
5a
5b
Ph–
4-CH3C6H4–
5a
18a
18b
24a
24b
24a
16
9
4-CH3OC6H4–
10
11
12
2,5-(CH3)2C6H3–
3,4,5-(CH3O)3C6H2–
13
14
14
1
95 (3j)
78 (3k)
15
16
24a
84
67 (3l)
CH3(CH2)11
–
60 (3III)
17
15b
91 (3VI)
18
5b
100 (3X)
a Half amount each of I2 and K2CO3 was added at first, and the rest was
added later.
b Molar ratio of I2/K2CO3 is 3.0/3.0.
Scheme 1. Plausible reaction pathway for 2,2,2-trifluoroethyl ester.

N. Mori, H. Togo / Tetrahedron 61 (2005) 5915–5925
5917
Table 3. Oxidation of primary alcohols to methyl esters with I2/K2CO3 in
CH3OH
2. Results and discussion
2.1. Preparation of 2,2,2-trifluoroethyl esters
At first, direct oxidative conversion of alcohols to the esters
with molecular iodine in the presence of potassium
carbonate was carried out. Table 1 shows the effect of a
protic polar solvent (5 ml for 1 mmol of alcohol), that is,
t-butyl alcohol, ethanol, methanol, water, and 2,2,2-
trifluoroethanol in the oxidative conversion of p-methyl-
benzyl alcohol to the corresponding esters or acid (with
water). It indicates 2,2,2-trifluoroethanol is the best solvent
among them, to provide the corresponding 2,2,2-trifluoro-
ethyl ester in high yield (entry 8). Thus, less acidic solvents
such as water, methanol, ethanol, t-butyl alcohol gave the
ester or acid products in low yield under the present
conditions. Since it is known that the pKa value of 2,2,2-
trifluoroethanol is ca. 12.4,32 the result suggests that the
acidic polar solvent promotes the present reaction. Prob-
ably, 2,2,2-trifluoroethanol activates molecular iodine as an
oxidant through a hydrogen bond between its OH proton and
molecular iodine. Recently, it has been known that 2,2,2-
trifluoroethanol sometimes promotes the reactions; there-
fore, synthetic use of 2,2,2-trifluoroethanol as a solvent is
interesting.33 For example, 2,2,2-trifluoroethanol activates
hydrogen peroxide for the oxidation of thiols to disulfides,33a
epoxidation of olefins,33b–d Mn(III)/Cu(II)-mediated oxi-
dative radical cyclization of a-(methylthio) acetamides,33e
Et3N-induced b-cleavage reaction,33f etc. The addition of a
small amount of methanesulfonic acid to the methanol or
ethanol solvent was not effective. The present reaction
requires potassium carbonate as a base (entry 6). Though
1,1,1,3,3,3-hexafluoro-2-propanol (pKa 9.2) is more acidic
than 2,2,2-trifluoroethanol, the yield was much reduced due
to the poor solubility of molecular iodine (entry 9).
Entry
R–
Time (h)
Yielda (%)
1
2
3
4
5
6
3-O2NC6H4–
4-ClC6H4–
Ph–
4-CH3C6H4–
4-CH3OC6H4–
3,4,5-(CH3O)3C6H2–
20
21
14
15
28
19
86
93
86
87
74
77
7
30
82
8
9
24
39
82
91
10
11
12
13
PhCH2CH2–
CH3(CH2)6–
CH3(CH2)11–
4-CH3OC6H4(CH2)2–
40b
5
76
73
70
82
7
80b
14
15
23
8
70
90
16
17
27
76
75
CH2]CH(CH2)8–
20c
a Method A. Alcohol (1 mmol) in MeOH (0.5 ml).
b Method B. Alcohol (2 mmol) in MeOH (0.6 ml).
c After the reaction, zinc powder was added to regenerate the olefinic group.
In the present oxidative conversion of alcohols in 2,2,2-
trifluoroethanol with molecular iodine and potassium
carbonate, it was found that the solvent, 2,2,2-trifluoro-
ethanol, was not oxidized at all by the NMR measurement of
the reaction mixture. Here, exactly, aldehyde is formed at
electrochemical conversion of alcohols to the corresponding
ketones or esters using potassium iodide via the formation
of iodonium ion species generated by electroxidation,30 and
oxidative conversion of secondary alcohols into a-iodo-
ketones with NaI, H2O2, and acid,31a and oxidation of
31b
alcohols using IPy2BF4/I2 were reported.
Table 4. Oxidative condensation of 3-phenylpropanol with I2/K2CO3 in
protic polar solvents
R0OH
Entry
I2/K2CO3
(equiv)
Time (h)
Yields (%)
1
2
3
4
5
6
7
8
9
1.2/5
1.2/5
1.2/5
1.2/5
1.2/5
1.2/1.2
1.2/2.4
1.2/3.6
3.0/3.0
CH3OH
21
21
21
21
21
66
66
66
45
0 (26,a 70b)
0 (8,c 89b)
8 (92b)
CH3CH2OH
(CH3)2CHOH
CF3CH2OH
(CH3)3COH
(CH3)3COH
(CH3)3COH
(CH3)3COH
(CH3)3COH
34 (50b)
96
42 (58b)
84 (16b)
93 (7b)
92 (7b)
a Yield of methyl 3-phenylpropanoate.
b Yield of recovered 3-phenylpropanol.
c Yield of ethyl 3-phenylpropanoate.
Scheme 2. Plausible reaction pathway for condensed ester.

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N. Mori, H. Togo / Tetrahedron 61 (2005) 5915–5925
Table 5. Oxidative condensation of primary alcohols with I2/K2CO3 in t-BuOH
Entry
R–
Time (h)
Yields (%)
Entry
R–
Time (h)
Yields (%)
1
2
3
3-O2NC6H4–
3,4-Cl2C6H3–
4-CF3C6H4–
16
48
48
95 (5a)
99 (5b)
99 (5c)
10
11
12
4-CH3OC6H4(CH2)2–
PhOCH2–
27
42a
27
98 (5IV)
78 (5V)
93 (5VI)
4
19
99 (5k)
13
19
88 (5VII)
5
6
4-CHDOC6H4–
Ph(CH2)2–
31
21
3 (97b)
14
15
33
50
76 (5VIII)
72 (5IX)
96 (5I)
7
8
48c
33
97
97 (5II)
16
17
Br(CH2)5–
42
26
94d
CH3(CH2)6–
32 (41b)
9
CH3(CH2)11
–
41
98 (5III)
a I2 (2.4 equiv) was used.
b Yield of aldehyde.
c Reaction was carried out with 3 g (22 mmol) of alcohol.
d Bromine atom was partly substituted by iodine atom (ca. 12%).
first, and, therefore, it can be obtained in high yield when the
reaction is carried out at room temperature. For example, the
treatment of p-methoxybenzyl alcohol, 2,4,6-trimethyl-
benzyl alcohol, and a-thienylmethanol with molecular
iodine (2.5 equiv) and potassium carbonate (2.5 equiv) in
2,2,2-trifluoroethanol at room temperature for 19, 83, and
70 h provided the corresponding aldehydes in 99, 85, and
87% yields together with trace amounts of the correspond-
ing 2,2,2-trifluoroethyl esters, respectively. Though
TEMPO-mediated oxidation of alcohols to aldehydes with
molecular iodine was reported recently,34 aldehydes can be
formed by the reaction of alcohols with molecular iodine
alone in 2,2,2-trifluoroethanol. Once aldehydes are formed,
then oxidative conversion to 2,2,2-trifluoroethyl esters
proceeds smoothly via the hemiacetals, as shown in
Scheme 1.
When a mixture of alcohol with I2 and K2CO3 in a small
amount of methanol was refluxed, the corresponding methyl
esters were obtained in high yields, as shown in Table 3. In
the present oxidative conversion of alcohols to methyl esters
with methanol solvent, methanol is partly oxidized
competitively. Therefore, the amount of solvent was quite
reduced, and conditions were concentrated (0.3–0.5 ml for
1 mmol of alcohol) to provide the corresponding esters in
the best yield.
2.3. Preparation of oxidative condensed esters
3-Phenylpropanol was treated with molecular iodine and
potassium carbonate in various alcoholic solvents (0.5 ml
for 1 mmol alcohol), such as methanol, ethanol, isopropyl
alcohol, 2,2,2-trifluoroethanol, and t-butyl alcohol, at room
temperature, and the results are shown in Table 4. Thus, the
results indicate that t-butyl alcohol is the best solvent, with
1.2 equiv of molecular iodine and 5.0 equiv of potassium
carbonate, to provide 3-phenylpropyl 3-phenylpropanoate
in high yields (entries 5–8).
Based on these results, a variety of primary alcohols were
directly oxidized to the corresponding 2,2,2-trifluoroethyl
esters in good yields, as shown in Table 2. Benzylic alcohols
(entries 1–15), aliphatic primary alcohols (entries 16 and
17), and neopentyl-typed 1-adamantanemethanol (entry 18)
could be oxidized to the corresponding 2,2,2-trifluoroethyl
esters in good to moderate yields. In benzylic alcohols,
formation of the esters with high yields requires 5 equiv
each of molecular iodine and potassium carbonate, while in
aliphatic primary alcohols, 3 equiv each was required. The
present reaction is clean and the esters are obtained in quite
good yields from the simple primary alcohols.
The reaction probably proceeds as follows: oxidation of
alcohol to aldehyde by molecular iodine, formation of
hemiacetal by the reaction of the formed aldehyde and
alcohol, and then, oxidation of the hemiacetal to an ester by
molecular iodine, as shown in Scheme 2.
Based on these results, various benzylic alcohols (entries
1–4) and primary alcohols (entries 6–16) could be directly
converted to the corresponding oxidatively condensed esters
in high yields in t-butyl alcohol at room temperature, except
for p-methoxybenzyl alcohol which has an electron-
donating group (entry 5), and 1-adamantanemethanol
which is a neopentyl-type alcohol (entry 17), as shown in
Table 5. When the reaction was carried out with 3 g
2.2. Preparation of methyl esters
When methanol was used as a solvent, instead of 2,2,2-
trifluoroethanol, under the same conditions with molecular
iodine and potassium carbonate, the formation of methyl
esters was observed. However, the yields were not high.

N. Mori, H. Togo / Tetrahedron 61 (2005) 5915–5925
5919
Table 6. Stoichiometrically oxidative condensation of aldehydes and alcohols with I2/K2CO3 in t-BuOH
R0-CHO (1.0 equiv)
Entry
R-CH2OH (1.05 equiv)
Time (h)
Yields (%)
1
2
3
PhCH2CH2CHO
PhCH2CH2CHO
PhCH2CH2CHO
4-ClC6H4CH2OH
4-CH3C6H4CH2OH
22
22
90 (6d)
87 (6f)
61 (6m)
22a
4
5
6
7
PhCH2CH2CHO
PhCH2CH2CHO
PhCH2CH2CHO
PhCH2CH2CHO
CH3(CH2)7OH
CH3(CH2)12OH
PhO(CH2)2OH
22
24
22
22
91 (6II)
84 (6III)
89 (6V)
91 (6VIII)
8
PhCH2CH2CHO
22
76 (6IX)
9
PhCH2CH2CHO
PhCH2CH2CHO
22
25
80 (6XI)
10
84 (6XII)
11
PhCH2CH2CHO
23
63b (6XIII)
87 (6II0)
62
12
13
14
15
CH3(CH2)3CHO
PhCH(CH3)CHO
PhCHO
CH3(CH2)7OH
CH3(CH2)7OH
CH3(CH2)7OH
CH3(CH2)7OH
22
22
22
22
47 (46c)
20 (45c)
a Aldehyde/alcoholZ1.5/1.0 (equiv), and reaction temperature was 45 8C.
b Yield of mono ester.
c Yield of octyl octanoate (5II).
(22 mmol) of 3-phenylpropanol, instead of 1 mmol scale,
3-phenylpropyl 3-phenylpropanoate was obtained again in
high yield (entry 7). Thus, this reaction can be carried out
easily for large-scale preparation of oxidatively condensed
esters from primary alcohols.
2.5. Preparation of ketones
Benzylic (entries 1–5) and aliphatic (entries 6–12) alcohols
could be also oxidized in t-butyl alcohol with molecular
iodine and potassium carbonate under the refluxing
conditions smoothly, to the corresponding ketones in high
yields, as shown in Table 7. 2,3,5-Tri-O-benzyl-D-ribo-
furanose and cholestanol were oxidized to 2,3,5-tri-O-
benzyl-D-ribofuranone and cholestanone in good yields,
respectively (entries 11 and 12). Generally, purine-like
C-nucleosides such as formycin A and formycine B were
synthesized from 2,3,5-tri-O-benzyl-D-ribofuranone.35
However, diacetone-D-glucose was not oxidized at all,
even for long reaction time. Probably, molecular iodine
cannot approach the hydroxyl group, due to the steric
hindrance (entry 13).
2.4. Stoichiometrically oxidative condensation of
aldehydes and alcohols to esters
At first, esterification of 3-phenylpropanal with various
alcohols was carried out using iodine and potassium
carbonate in t-butyl alcohol at room temperature (entries
1–11). Next, some of the aldehydes with 1-octanol were
examined (entries 12–15). The results are summarized in
Table 6, and indicate that the oxidative esterification of
aldehydes bearing a primary alkyl group, with primary
alcohols proceeded smoothly to provide the corresponding
esters in high yields. The reactions of aldehydes bearing a
primary alkyl group, with secondary alcohols, or aldehydes
bearing a secondary alkyl group, with alcohols, gave the
corresponding esters in moderate to low yields. Thus the
present oxidative condensation of aldehydes with alcohols
is rather sensitive to steric hindrance and electronic effect,
since the formation of hemiacetal is the key step.
3. Conclusion
The present method is a simple, efficient, and high-yield
procedure for the oxidative conversion of primary alcohols
to the corresponding esters, condensed esters, and secondary
alcohols to the corresponding ketones, with molecular

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N. Mori, H. Togo / Tetrahedron 61 (2005) 5915–5925
Table 7. Oxidation of secondary alcohols to ketones with I2/K2CO3 in
t-BuOH
for column chromatography and Wakogel B-5F was used
for preparative TLC.
Most of the organic chemical substrates are commercially
available. All the compounds gave satisfactory spectro-
scopic data, most methyl esters and ketones were identified
with commercially available authentic materials.36
Entry
Secondary alcohol
Time (h) Yield
(%)
4.2. Typical procedure for oxidative conversion of
primary alcohols to 2,2,2-trifluoroethyl esters
1
2
3
4
5
PhCHOHC2H5
8
6
5
6
7
99
86
99
99
99
4-ClC6H4CHOHCH3
4-CH3C6H4CHOHCH3
PhCHOH(CH2)7CH3
To a solution of benzyl alcohol (1 mmol) in CF3CH2OH
(5 ml) were added I2 (2.5 mmol) and K2CO3 (2.5 mmol)
under an argon atmosphere. The mixture obtained was
stirred for 2 h at 50 8C, then I2 (2.5 mmol) and K2CO3
(2.5 mmol) were added to the mixture again. After 3 h at the
same temperature, the mixture was quenched with satd aq
Na2SO3 (3–5 ml) at 0 8C, and was extracted with Et2O three
times. The organic layer was washed with brine and dried
over Na2SO4 to provide 2,2,2-trifluoroethyl benzoate in
91% yield in an almost pure state. If necessary, the product
was purified by flash column chromatography on silica gel
(hexane–EtOAcZ4:1) to give pure 2,2,2-trifluoroethyl
benzoate as an oil.
6
16
99
7
8
4
6
78
99
4.2.1. 2,2,2-Trifluoroethyl 3-nitrobenzoate (3a). Colorless
solid; mp 46–47 8C; IR (KBr): 1750, 1300, 1250, 1170,
1130 cmK1; 1H NMR (CDCl3) dZ4.78 (2H, q, JZ8.4 Hz),
7.73 (1H, t, JZ8.1 Hz), 8.42 (1H, dt, JZ8.1, 1.2 Hz), 8.49
(2H, ddd, JZ8.1, 2.2, 1.2 Hz), 8.91 (1H, t, JZ2.2 Hz);
HRMS (FAB): obsd MCHZ250.0320, calcd for
C9H7F3NO4 MCHZ250.0327.
9
10
11
CH3(CH2)4CHOH(CH2)4CH3
Ph(CH2)3CHOHCH3
5
6
8
99
99
79
12
13
40
90
4.2.2. 2,2,2-Trifluoroethyl 3,4-dichlorobenzoate (3b).
Colorless solid; mp 32–33 8C; IR (KBr): 1740, 1300,
1
1265, 1235, 1170, 1110 cmK1; H NMR (CDCl3) dZ4.71
20
0 (88a)
(2H, q, JZ8.4 Hz), 7.57 (1H, d, JZ8.4 Hz), 7.90 (1H, dd,
JZ8.4, 2.0 Hz), 8.15 (1H, d, JZ2.0 Hz); HRMS (EI): obsd
MCZ271.9624, calcd for C9H5Cl2F3O2 MCZ271.9619.
4.2.3. 2,2,2-Trifluoroethyl 4-trifluoromethylbenzoate
a Yield of starting alcohol.
(3c). Oil; IR (neat): 1745, 1165, 1130, 1100, 1065 cmK1
;
1H NMR (CDCl3) dZ4.74 (2H, q, JZ8.3 Hz), 7.75 (2H, d,
JZ8.1 Hz), 8.20 (2H, d, JZ8.1 Hz); HRMS (EI): obsd
MCZ272.0293, calcd for C10H6F6O2 MCZ272.0298.
iodine and potassium carbonate in 2,2,2-trifluoroethanol,
methanol, and t-butyl alcohol. The advantages of the present
reactions are the operational simplicity, elimination of the
use of toxic oxidants or solvents, generality of the reactions,
and high yield of the products.
4.2.4. 2,2,2-Trifluoroethyl 4-chlorobenzoate (3d). Oil;
IR (neat): 1740, 1295, 1255, 1170, 1105 cmK1 1H
;
NMR (CDCl3) dZ4.70 (2H, q, JZ8.4 Hz), 7.46 (2H, d,
JZ8.8 Hz), 8.02 (2H, d, JZ8.8 Hz); HRMS (EI): obsd
MCZ238.0005, calcd for C9H6ClF3O2 MCZ238.0008.
4. Experimental
4.1. General
4.2.5. 2,2,2-Trifluoroethyl benzoate (3e). Oil; bp 84–
86 8C/19 mm Hg (lit.37 bp 77 8C/13 mm Hg); IR (neat):
1
1740, 1295, 1255, 1170, 1115 cmK1; H NMR (CDCl3)
1H NMR and 13C NMR spectra were obtained with JEOL-
JNM-LA-400, JEOL-JNM-LA-400s, and JEOL-JNM-LA-
500 spectrometers. Chemical shifts are expressed in ppm
downfield from tetramethylsilane (TMS) in d units. IR
spectra were measured with JASCO FT/IR-200 and FT/IR-
4100 spectrometers. Mass spectra were recorded on JEOL-
HX-110 and JEOL-JMS-ATII15 spectrometers. Melting
points were determined on Yamato melting points apparatus
Model MP-21. Silica Gel 60 (Kanto Kagaku Co.) was used
dZ4.70 (2H, q, JZ8.4 Hz), 7.48 (2H, t, JZ7.7 Hz),
7.62 (1H, tt, JZ7.7, 1.4 Hz), 8.09 (2H, dt, JZ7.7, 1.4 Hz);
HRMS (EI): obsd MCZ204.0413, calcd for C9H7F3O2
MCZ204.0398.
4.2.6. 2,2,2-Trifluoroethyl p-toluate (3f). Oil; IR (neat):
1
1740, 1295, 1260, 1170, 1110 cmK1; H NMR (CDCl3)
dZ2.43 (3H, s), 4.68 (2H, q, JZ8.4 Hz), 7.27 (2H, d,

N. Mori, H. Togo / Tetrahedron 61 (2005) 5915–5925
5921
JZ8.1 Hz), 7.97 (2H, d, JZ8.1 Hz); HRMS (EI): obsd
MCZ218.0561, calcd for C10H9F3O2 MCZ218.0555.
4.3. Typical procedure for oxidative conversion of
primary alcohols to methyl esters
To a solution of 4-chlorobenzyl alcohol (1 mmol) in
CH3OH (0.5 ml) were added I2 (3 mmol) and K2CO3
(3 mmol) under an argon atmosphere. The mixture obtained
was stirred at 70 8C. After 21 h at the same temperature, the
mixture was quenched with satd aq Na2SO3 (3–5 ml) at
0 8C, and was extracted with Et2O three times. The organic
layer was washed with brine and dried over Na2SO4 to
provide methyl 4-chlorobenzoate in 93% yield in an almost
pure state. If necessary, the product was purified by flash
column chromatography on silica gel (hexane–EtOAcZ
4.2.7. 2,2,2-Trifluoroethyl 4-methoxybenzoate (3g). Oil;
IR (neat): 1735, 1255, 1165 cmK1 1H NMR (CDCl3)
;
dZ3.88 (3H, s), 4.67 (2H, q, JZ8.4 Hz), 6.95 (2H, d,
JZ9.0 Hz), 8.03 (2H, d, JZ9.0 Hz); HRMS (EI): obsd
MCZ234.0494, calcd for C10H9F3O3 MCZ234.0504.
4.2.8. 2,2,2-Trifluoroethyl 2,5-dimethylbenzoate (3h).
Oil; 1H NMR (CDCl3) dZ2.36 (3H, s), 2.56 (3H, s),
4.67 (2H, q, JZ8.4 Hz), 7.16 (1H, d, JZ8.0 Hz), 7.26
(1H, d, JZ8.0 Hz), 7.77 (1H, s); HRMS (EI): obsd
MCZ232.0708, calcd for C11H11F3O2 MCZ232.0711.
8:1) to give pure methyl 4-chlorobenzoate as
a
colorless solid. Mp 43 8C (lit.36 mp 43 8C). 1H NMR
(CDCl3): dZ3.92 (3H, s), 7.42 (2H, d, JZ8.8 Hz), 7.98
(2H, d, JZ8.8 Hz).
4.2.9. 2,2,2-Trifluoroethyl 3,4,5-trimethoxybenzoate (3i).
Colorless solid; mp 67–68 8C; IR (KBr): 1735, 1160,
1
1130 cmK1; H NMR (CDCl3) dZ3.92 (6H, s), 3.93 (3H,
4.4. Typical procedure for oxidative condensation of
primary alcohols to esters
s), 4.70 (2H, q, JZ8.4 Hz), 7.32 (2H, s); HRMS
(FAB): obsd MCZ294.0698, calcd for C12H13F3O5
MCZ294.0715.
To a solution of 3-phenylpropanol (1 mmol) in t-butyl
alcohol (0.5 ml) were added I2 (1.2 mmol) and K2CO3
(5.0 mmol) under an argon atmosphere. The obtained
mixture was stirred at room temperature, until the iodine
color almost disappeared. After 21 h at the same tempera-
ture, the mixture was quenched by the addition of water
(20 ml), Et2O (5 ml), and satd aq Na2SO3 (0.5 ml) at 0 8C.
Then the mixture was extracted with Et2O three times. The
organic layer was washed with brine and dried over Na2SO4
to provide 3-phenylpropyl 3-phenylpropanoate in 96% yield
in an almost pure state. If necessary, the product was
purified by flash column chromatography on silica gel
(hexane–EtOAcZ10:1) to give pure 3-phenylpropyl
3-phenylpropanoate as a colorless oil.
4.2.10. 2,2,2-Trifluoroethyl 1-naphthoate (3j). Colorless
solid; mp 28–29 8C; IR (KBr): 1720, 1160, 1125 cmK1; 1H
NMR (CDCl3) dZ4.79 (2H, q, JZ8.4 Hz), 7.55 (2H, m),
7.66 (1H, td, JZ7.8, 1.4 Hz), 7.91 (1H, d, JZ7.8 Hz), 8.09
(1H, dd, JZ7.8, 1.4 Hz), 8.29 (1H, d, JZ7.8 Hz), 8.92 (1H,
d, JZ7.8 Hz); HRMS (FAB): obsd MCZ254.0549, calcd
for C13H9F3O2 MCZ254.0555.
4.2.11. 2,2,2-Trifluoroethyl nicotinate (3k). Oil; IR (neat):
1745, 1300, 1260, 1180, 1120 cmK1; 1H NMR (CDCl3) dZ
4.75 (2H, q, JZ8.3 Hz), 7.45 (1H, dd, JZ8.0, 4.9 Hz), 8.34
(1H, dt, JZ8.0, 1.9 Hz), 8.85 (1H, dd, JZ4.9, 1.9 Hz), 9.28
(1H, d, JZ1.9 Hz); HRMS (EI): obsd MCZ205.0348,
calcd for C8H6F3NO2 MCZ205.0351.
4.4.1. 3-Nitrobenzyl 3-nitrobenzoate (5a). Colorless solid;
mp 146–147 8C; IR (KBr): 1720, 1280, 1265, 1140 cmK1
;
1H NMR (CDCl3) dZ5.52 (2H, s), 7.62 (1H, t, JZ8.1 Hz),
7.70 (1H, t, JZ8.1 Hz), 7.82 (1H, m), 8.24 (1H, m), 8.34
(1H, m), 8.41 (1H, m), 8.45 (1H, m), 8.89 (1H, m); 13C
NMR (CDCl3) dZ66.1 (s), 123.2 (t), 123.3 (t), 123.6 (t),
124.7 (t), 127.8 (t), 129.8 (t), 131.3 (q), 134.3 (t), 135.4 (t),
137.3 (q), 148.3 (q), 148.4 (q), 164.1 (q); HRMS (EI): obsd
MCZ302.0541, calcd for C14H10N2O6 MCZ302.0539.
4.2.12. 2,2,2-Trifluoroethyl thiophene-2-carboxylate (3l).
1
Oil; IR (neat): 1725, 1250, 1160, 1095 cmK1; H NMR
(CDCl3) dZ4.68 (2H, q, JZ8.4 Hz), 7.15 (1H, dd, JZ5.0,
3.9 Hz), 7.66 (1H, dd, JZ5.0, 1.2 Hz), 7.89 (1H, dd, JZ3.9,
1.2 Hz); HRMS (EI): obsd MCZ209.9967, calcd for
C7H5F3O2S MCZ209.9962.
1
4.2.13. 2,2,2-Trifluoroethyl tridecanoate (3III). Oil; H
4.4.2. 3,4-Dichlorobenzyl 3,4-dichlorobenzoate (5b).
Colorless solid; mp 90–91 8C; IR (KBr): 1725, 1295,
NMR (CDCl3) dZ0.88 (3H, t, JZ6.9 Hz), 1.22–1.32 (18H,
m), 1.61 (2H, q, JZ7.5 Hz), 2.41 (2H, t, JZ7.5 Hz), 4.46
(2H, q, JZ8.4 Hz); HRMS (EI): obsd MCZ296.1957,
calcd for C15H27F3O2 MCZ296.1963.
1
1270, 1245, 1110 cmK1; H NMR (CDCl3) dZ5.30 (2H,
s), 7.27 (1H, dd, JZ8.3, 2.0 Hz), 7.47 (1H, d, JZ8.3 Hz),
7.53 (2H, m), 7.88 (1H, dd, JZ8.3, 2.0 Hz), 8.12 (1H,
d, JZ2.0 Hz); 13C NMR (CDCl3) dZ65.7 (s), 127.6 (t),
128.7 (t), 129.5 (q), 130.3 (t), 130.6 (t), 130.7 (t), 131.6
(t), 132.8 (q), 132.9 (q), 133.1 (q), 135.6 (q), 138.0 (q),
164.3 (q); HRMS (EI): obsd MCZ347.9285, calcd for
C14H8Cl4O2 MCZ347.9278.
4.2.14. 2,2,2-Trifluoroethyl cyclohexanecarboxylate
1
(3VI). Oil; H NMR (CDCl3) dZ1.28 (3H, m), 1.47 (2H,
m), 1.65 (1H, m), 1.75 (2H, m), 1.94 (2H, m), 2.42 (1H, tt,
JZ11.1, 3.6 Hz), 4.47 (2H, q, JZ8.5 Hz); HRMS (EI): obsd
MCZ210.0860, calcd for C9H13F3O2 MCZ210.0868.
4.4.3. 4-(Trifluoromethyl)benzyl 4-(trifluoromethyl)-
4.2.15. 2,2,2-Trifluoroethyl adamantanecarboxylate
(3X). Oil; bp 90–100 8C/1 mm Hg; IR (neat): 1745, 1160,
benzoate (5c). Colorless solid; mp 57–58 8C (lit.38 mp
61–62 8C); IR (KBr): 1720, 1325, 1270, 1105, 1065 cmK1
;
1080 cmK1; H NMR (CDCl3) dZ1.73 (6H, m), 1.93 (6H,
1H NMR (CDCl3) dZ5.45 (2H, s), 7.57 (2H, d, JZ8.2 Hz),
7.66 (2H, d, JZ8.0 Hz), 7.72 (2H, d, JZ8.2 Hz), 8.19 (2H,
d, JZ8.0 Hz); 13C NMR (CDCl3) dZ66.2 (s), 125.5 (t),
1
m), 2.04 (3H, m), 4.45 (2H, q, JZ8.4 Hz); HRMS (EI): obsd
MCZ262.1178, calcd for C13H17F3O2 MCZ262.1181.

5922
N. Mori, H. Togo / Tetrahedron 61 (2005) 5915–5925
125.7 (t), 128.3 (t), 130.1 (t), 130.6 (q), 133.0 (q), 134.7 (q),
139.5 (q), 165.0 (q); HRMS (FAB): obsd MCHZ
349.0661, calcd for C16H11O2F6 MCHZ349.0663.
129.5 (t), 157.7 (q), 158.3 (q), 168.9 (q); HRMS (FAB):
obsd MCZ272.1059, calcd for C16H16O4 MCZ272.1049.
4.4.10. Cyclohexylmethyl cyclohexanecarboxylate (5VI).
1
4.4.4. 3-Pyridinylmethyl nicotinate (5k). Oil; IR (neat):
1720, 1275, 1110 cmK1; 1H NMR (CDCl3) dZ5.42 (2H, s),
7.35 (1H, ddd, JZ7.9, 4.9, 0.8 Hz), 7.41 (1H, ddd, JZ7.9,
4.9, 0.8 Hz), 7.81 (1H, dt, JZ7.9, 2.0 Hz), 8.32 (1H, dt, JZ
7.9, 2.0 Hz), 8.62 (1H, dd, JZ4.9, 1.5 Hz), 8.74 (1H, d, JZ
1.5 Hz), 8.80 (1H, dd, JZ4.9, 2.0 Hz), 9.25 (1H, dd, JZ2.0,
0.8 Hz); 13C NMR (CDCl3) dZ64.5 (s), 123.3 (t), 123.5 (t),
125.6 (q), 131.1 (q), 136.1 (t), 137.1 (t), 149.7 (t), 149.8 (t),
149.9 (t), 150.9 (t), 153.7 (t), 164.9 (q); HRMS (FAB): obsd
MCHZ215.0814, calcd for C12H11N2O2 MCHZ
215.0821.
Oil; IR (neat): 1730, 1170, 1130 cmK1; H NMR (CDCl3)
dZ0.97 (2H, m), 1.12–1.32 (6H, m), 1.44 (2H, m), 1.57–
1.78 (9H, m), 1.90 (2H, m), 2.29 (1H, tt, JZ11.3, 3.6 Hz),
3.87 (2H, d, JZ6.4 Hz); 13C NMR (CDCl3) dZ25.5 (s),
25.7 (s), 25.8 (s), 26.4 (s), 29.1 (s), 29.7 (s), 37.2 (t), 43.3 (t),
69.2 (s), 176.2 (q); HRMS (FAB): obsd MCHZ225.1858,
calcd for C14H25O2 MCHZ225.1855.
4.4.11. Cyclopentylmethyl cyclopentanecarboxylate
(5VII). Oil; IR (neat): 1730, 1180, 1155 cmK1; H NMR
1
(CDCl3) dZ1.25 (2H, m), 1.50–1.64 (6H, m), 1.65–1.84
(6H, m), 1.88 (2H, m), 2.20 (1H, septet, JZ7.5 Hz), 2.73
(1H, quint, JZ7.9 Hz), 3.96 (2H, d, JZ7.5 Hz); 13C NMR
(CDCl3) dZ25.3 (s), 25.8 (s), 29.3 (s), 30.0 (s), 38.6 (t), 44.0
(t), 68.2 (s), 176.9 (q); HRMS (FAB): obsd MCHZ
197.1531, calcd for C12H21O2 MCHZ197.1542.
4.4.5. 3-Phenylpropyl 3-phenylpropanoate (5I). Oil; bp
210 8C/1 mm Hg (lit.8b bp 146–150 8C/0.8 mm Hg); IR
(neat): 1730, 1160, 1030 cmK1 1H NMR (CDCl3) dZ
;
1.93 (2H, m), 2.63 (2H, t, JZ7.7 Hz), 2.64 (2H, t, JZ
7.7 Hz), 2.95 (2H, t, JZ7.7 Hz), 4.09 (2H, t, JZ6.5 Hz),
7.18 (6H, m) 7.28 (4H, m); 13C NMR (CDCl3) dZ30.2 (s),
31.0 (s), 32.1 (s), 35.9 (s), 63.8 (s), 126.0 (t), 126.3 (t), 128.3
(t), 128.4 (t), 128.5 (t), 140.5 (q), 141.2 (q), 173.0 (q);
HRMS (FAB): obsd MCHZ269.1552, calcd for C18H21O2
MCHZ269.1542.
4.4.12. (Tetrahydrofuran-2-yl)methyltetrahydrofuran-
2-carboxylate (5VIII). Oil; IR (neat): 1745, 1200, 1175,
1080 cmK1; 1H NMR (CDCl3) dZ1.62 (1H, m), 1.80–2.10
(6H, m), 2.26 (1H, m), 3.80 (1H, m), 3.90 (2H, m), 4.00–
4.18 (3H, m), 4.22 (1H, m), 4.51 (1H, m); 13C NMR
(CDCl3) dZ25.2 (s), 25.6 (s), 25.6 (s), 27.9 (s), 30.2 (s),
66.6 (s), 68.4 (s), 69.3 (s), 76.3 (t), 76.4 (t), 76.6 (t), 173.4
(q); HRMS (FAB): obsd MCHZ201.1145, calcd for
C10H17O4 MCHZ201.1127.
4.4.6. Octyl octanoate (5II). Oil; IR (neat): 1735, 1460,
1165 cmK1; 1H NMR (CDCl3) dZ0.88 (3H, t, JZ7.0 Hz),
0.88 (3H, t, JZ7.0 Hz), 1.25–1.40 (18H, m), 1.62 (4H, t,
JZ7.5 Hz), 2.29 (2H, t, JZ7.5 Hz), 4.06 (2H, t, JZ6.7 Hz);
13C NMR (CDCl3) dZ14.0 (p), 22.6 (s), 25.0 (s), 25.9 (s),
28.6 (s), 28.9 (s), 29.1 (s), 29.2 (s), 31.6 (s), 31.7 (s), 34.4
(s), 64.3 (s), 173.9 (q).
4.4.13. 3-(60-Methylpyridin-20-yl)propyl 3-(60-methyl-
pyridin-20-yl)propanoate (5IX). Oil; IR (neat): 1730,
1455, 1160 cmK1; H NMR (CDCl3) dZ2.04 (2H, tt, JZ
1
7.6, 6.5 Hz), 2.51 (3H, s), 2.52 (3H, s), 2.78 (4H, tt, JZ7.6,
3.1 Hz), 3.07 (2H, t, JZ7.6 Hz), 4.11 (2H, t, JZ6.5 Hz),
6.91 (1H, d, JZ7.6 Hz), 6.97 (3H, m), 7.47 (2H, t, JZ
7.6 Hz); 13C NMR (CDCl3) dZ24.5 (p), 28.7 (s), 33.0 (s),
33.8 (s), 34.6 (s), 63.9 (s), 119.6 (t), 119.7 (t), 120.7 (t),
120.8 (t), 136.6 (t), 157.9 (q), 159.4 (q), 160.3 (q), 173.1 (q);
HRMS (EI): obsd MCZ298.1678, calcd for C18H22N2O2
MCZ298.1681.
4.4.7. Tridecyl tridecanoate (5III). Colorless solid; mp
35–36 8C; IR (KBr): 1735, 1370, 1230, 1205, 1185 cmK1
;
1H NMR (CDCl3) dZ0.88 (6H, t, JZ6.9 Hz), 1.25–1.38
(38H, m), 1.63 (4H, m), 2.29 (2H, t, JZ7.6 Hz), 4.05 (2H, t,
JZ6.7 Hz); 13C NMR (CDCl3) dZ14.1 (p), 22.7 (s), 25.0
(s), 26.0 (s), 28.7 (s), 29.2 (s), 29.3 (s), 29.5 (s), 29.6 (s),
29.7 (s), 31.9 (s), 34.4 (s), 64.4 (s), 174.0 (q); HRMS (FAB):
obsd MCHZ397.4037, calcd for C26H53O2 MCHZ
397.4046.
4.5. Typical procedure for stoichiometrically oxidative
condensation of aldehydes with primary alcohols to
esters
4.4.8. 3-(40-Methoxyphenyl)propyl 3-(40-methoxyphenyl)
propanoate (5IV). Colorless solid; mp 38–39 8C; IR (KBr):
1
1730, 1510, 1245, 1030 cmK1; H NMR (CDCl3) dZ1.89
To a solution of 3-phenylpropanal (1 mmol) and 1-octanol
(1.05 mmol) in t-butyl alcohol (0.5 ml) were added I2
(1.2 mmol) and K2CO3 (3.0 mmol) under an argon atmo-
sphere. The obtained mixture was stirred at room temperature,
until the iodine color almost disappeared. After 22 h at the
same temperature, the mixture was quenched by the addition
of water (20 ml), Et2O (5 ml), and satd aq Na2SO3 (0.5 ml) at
0 8C. Then the mixture was extracted with Et2O three times.
The organic layer was washed with brine and dried over
Na2SO4 to provide octyl 3-phenylpropanoate in 91% yield. If
necessary, the product was purified by flash column
chromatography on silica gel (hexane–EtOAcZ10:1) to
give pure octyl 3-phenylpropanoate as a colorless oil.
(2H, tt, JZ7.9, 6.5 Hz), 2.58 (2H, t, JZ7.9 Hz), 2.60 (2H, t,
JZ7.9 Hz), 2.89 (2H, t, JZ7.9 Hz), 3.77 (3H, s), 3.78 (3H,
s), 4.07 (2H, t, JZ6.5 Hz), 6.83 (4H, dd, JZ7.8, 2.1 Hz),
7.06 (2H, d, JZ8.7 Hz), 7.13 (2H, d, JZ8.7 Hz); 13C NMR
(CDCl3) dZ30.1 (s), 30.3 (s), 31.1 (s), 36.1 (s), 55.2 (p),
63.7 (s), 113.7 (t), 113.8 (t), 129.2 (t), 132.5 (q), 133.2 (q),
157.8 (q), 158.0 (q), 173.0 (q); HRMS (FAB): obsd MC
HZ328.1671, calcd for C20H24O4 MCHZ328.1675.
4.4.9. 2-Phenoxyethyl 2-phenoxyacetate (5V). Colorless
solid; mp 82–83 8C (lit.39 mp 83–84 8C); IR (KBr): 1740,
1
1365, 1215 cmK1; H NMR (CDCl3) dZ4.19 (2H, t, JZ
4.7 Hz), 4.57 (2H, t, JZ4.7 Hz), 4.67 (2H, s), 6.90 (4H, m),
6.98 (2H, m), 7.28 (4H, m); 13C NMR (CDCl3) dZ63.5 (s),
65.2 (s), 65.6 (s), 114.6 (t), 114.7 (t), 121.3 (t), 121.8 (t),
4.5.1. 4-Chlorobenzyl 3-phenylpropanoate (6d). Oil; IR
1
(neat): 1735, 1495, 1145, 1090 cmK1; H NMR (CDCl3)

N. Mori, H. Togo / Tetrahedron 61 (2005) 5915–5925
5923
dZ2.68 (2H, t, JZ7.8 Hz), 2.96 (2H, t, JZ7.8 Hz), 5.06
(2H, s), 7.19 (5H, m), 7.28 (4H, m); 13C NMR (CDCl3) dZ
30.9 (s), 35.8 (s), 65.4 (s), 126.3 (t), 128.3 (t), 128.5 (t),
128.7 (t), 129.5 (t), 134.1 (q), 134.4 (q), 140.3 (q), 172.6 (q);
HRMS (FAB): obsd MCHZ275.0839, calcd for
C16H16O2Cl MCHZ275.0839.
7.28 (2H, m); 13C NMR (CDCl3) dZ25.6 (s), 27.9 (s), 30.9
(s), 35.7 (s), 66.5 (s), 68.4 (s), 76.4 (t), 126.2 (t), 128.2 (t),
128.4 (t), 140.4 (q), 172.8 (q); HRMS (FAB): obsd MCHZ
235.1314, calcd for C14H19O3 MCHZ235.1334.
4.5.8. 3-(60-Methylpyridin-20-yl)propyl 3-phenyl-pro-
panoate (6IX). Oil; IR (neat): 1730, 1455, 1155 cmK1
;
4.5.2. 4-Methylbenzyl 3-phenylpropanoate (6f). Oil; IR
1H NMR (CDCl3) dZ2.04 (2H, m), 2.52 (3H, s), 2.63 (2H, t,
JZ7.7 Hz), 2.78 (2H, t, JZ7.7 Hz), 2.95 (2H, t, JZ7.7 Hz),
4.12 (2H, t, JZ6.6 Hz), 6.90 (1H, d, JZ7.6 Hz), 6.96 (1H,
d, JZ7.6 Hz), 7.20 (3H, m), 7.28 (2H, m), 7.47 (1H, t, JZ
7.6 Hz); 13C NMR (CDCl3) dZ24.5 (p), 28.7 (s), 30.9 (s),
34.7 (s), 35.8 (s), 64.0 (s), 119.6 (t), 120.7 (t), 126.2 (t),
128.3 (t), 128.5 (t), 136.6 (t), 140.5 (q), 157.9 (q), 160.3 (q),
172.9 (q); HRMS (FAB): obsd MCHZ284.1634, calcd for
C18H22NO2 MCHZ284.1651.
1
(neat): 1730, 1150 cmK1; H NMR (CDCl3) dZ2.34 (3H,
s), 2.66 (2H, t, JZ7.8 Hz), 2.95 (2H, t, JZ7.8 Hz), 5.06
(2H, s), 7.13–7.22 (7H, m), 7.26 (2H, m); 13C NMR (CDCl3)
dZ21.1 (p), 30.9 (s), 35.9 (s), 66.2 (s), 126.2 (t), 128.3 (t),
128.4 (t), 128.5 (t), 129.2 (t), 132.9 (q), 138.0 (q), 140.4 (q),
172.7 (q); HRMS (FAB): obsd MCHZ255.1392, calcd for
C17H19O2 MCHZ255.1385.
4.5.3. (N-Tosyl-indol-3-yl)methyl 3-phenylpropanoate
1
(6m). Oil; H NMR (CDCl3) dZ2.34 (3H, s), 2.65 (2H, t,
4.5.9. 4-(Benzyloxy)phenethyl 3-phenylpropanoate
(6XI). Colorless solid; mp 61–62 8C; IR (KBr): 1725,
JZ7.8 Hz), 2.94 (2H, t, JZ7.8 Hz), 5.22 (2H, s), 7.12–7.27
(7H, m), 7.34 (1H, t, 7.6 Hz), 7.47 (1H, d, 7.6 Hz), 7.60 (1H,
s), 7.78 (2H, d, 7.6 Hz), 7.97 (1H, d, 7.6 Hz); 13C NMR
(CDCl3) dZ21.5 (p), 30.8 (s), 35.7 (s), 57.7 (s), 113.6 (t),
117.2 (q), 119.7 (t), 123.4 (t), 125.0 (t), 125.6 (t), 126.2 (t),
126.9 (t), 128.2 (t), 128.4 (t), 129.4 (q), 129.9 (t), 135.0 (q),
135.1 (q), 140.2 (q), 145.1 (q), 172.7 (q); HRMS (FAB):
obsd MCZ433.1339, calcd for C25H23NO4S MCZ
433.1348.
1
1240, 1170 cmK1; H NMR (CDCl3) dZ2.60 (2H, t, JZ
7.8 Hz), 2.83 (2H, t, JZ7.0 Hz), 2.91 (2H, t, JZ7.8 Hz),
4.23 (2H, t, JZ7.0 Hz), 5.02 (2H, s), 6.89 (2H, d, JZ
8.7 Hz), 7.08 (2H, d, JZ8.7 Hz), 7.17 (3H, m), 7.28 (3H,
m), 7.38 (4H, m); 13C NMR (CDCl3) dZ30.9 (s), 34.2 (s),
35.9 (s), 65.2 (s), 70.0 (s), 114.8 (t), 126.2 (t), 127.5 (t),
127.9 (t), 128.3 (t), 128.5 (t), 128.6 (t), 129.9 (t), 130.1 (q),
137.1 (q), 140.5 (q), 157.5 (q), 172.8 (q); HRMS (FAB):
obsd MCZ360.1721, calcd for C24H24O3 MCZ360.1725.
4.5.4. Octyl 3-phenylpropanoate (6II). Oil; IR (neat):
1
1735, 1160 cmK1; H NMR (CDCl3) dZ0.88 (3H, t, JZ
4.5.10. 2-(10,70,70-Trimethyl-bicyclo[2,2,1] hept-20-
yloxy)ethyl 3-phenylpropanoate (6XII). Oil; IR (neat):
1735, 1165, 1120 cmK1; 1H NMR (CDCl3) dZ0.80 (3H, s),
0.87 (3H, s), 0.96 (3H, s), 0.97 (2H, m), 1.45–1.75 (5H, m),
2.63 (2H, t, JZ7.8 Hz), 2.95 (2H, t, JZ7.8 Hz), 3.20 (1H,
dd, JZ7.5, 3.5 Hz), 3.47 (1H, m), 3.58 (1H, m), 4.17 (2H,
m), 7.20 (3H, m), 7.28 (2H, m); 13C NMR (CDCl3) dZ11.7
(p), 20.1 (p), 20.2 (p), 27.3 (s), 30.9 (s), 34.4 (s), 35.9 (s),
38.5 (s), 45.0 (t), 46.4 (q), 49.2 (q), 63.8 (s), 66.9 (s), 87.4
(t), 126.2 (t), 128.3 (t), 128.5 (t), 140.6 (q), 172.8 (q); HRMS
(FAB): obsd MCZ330.2214, calcd for C21H30O3 MCZ
330.2195.
7.0 Hz), 1.22–1.38 (10H, m), 1.59 (2H, m), 2.63 (2H, t, JZ
7.9 Hz), 2.95 (2H, t, JZ7.9 Hz), 4.06 (2H, t, JZ6.8 Hz),
7.20 (3H, m), 7.29 (2H, m); 13C NMR (CDCl3) dZ14.1 (p),
22.6 (s), 25.9 (s), 28.6 (s), 29.1 (s), 29.2 (s), 31.0 (s), 31.8
(s), 35.9 (s), 64.6 (s), 126.2 (t), 128.3 (t), 128.4 (t), 140.5 (q),
173.0 (q); HRMS (FAB): obsd MCHZ263.2017, calcd for
C17H27O2 MCHZ263.2011.
4.5.5. Tridecyl 3-phenylpropanoate (6III). Oil; IR (neat):
1735, 1455, 1160 cmK1; 1H NMR (CDCl3) dZ0.88 (3H, t,
JZ7.0 Hz), 1.22–1.38 (20H, m), 1.63 (2H, m), 2.62 (2H, t,
JZ7.9 Hz), 2.95 (2H, t, JZ7.9 Hz), 4.06 (2H, t, JZ6.7 Hz),
7.20 (3H, m), 7.28 (2H, m); 13C NMR (CDCl3) dZ14.2 (p),
22.8 (s), 26.0 (s), 28.7 (s), 29.3 (s), 29.4 (s), 29.6 (s), 29.7
(s), 29.8 (s), 31.1 (s), 32.0 (s), 36.0 (s), 64.7 (s), 126.3 (t),
128.4 (t), 128.5 (t), 140.7 (q), 173.1 (q).
4.5.11. (R)-2-((3aR,5R,6R,6aS)-6-(Benzyloxy)-tetra-
hydro-2,2-dimethylfuro[2,3-d][1,3]dioxol-5-yl)-2-
hydroxyethyl 3-phenylpropanoate (6XIII). Oil; IR (neat):
1735, 1215, 1165, 1070, 1025 cmK1; 1H NMR (CDCl3) dZ
1.30 (3H, s), 1.46 (3H, s), 2.46 (1H, broad), 2.65 (2H, t, JZ
7.8 Hz), 2.94 (2H, t, JZ7.8 Hz), 4.09 (2H, m), 4.14 (2H, m),
4.38 (1H, dd, JZ14.4, 5.5 Hz), 4.55 (1H, d, JZ11.9 Hz),
4.60 (1H, d, JZ3.9 Hz), 4.69 (1H, d, JZ11.9 Hz), 5.91 (1H,
d, JZ3.9 Hz), 7.18 (3H, t, JZ3.9 Hz), 7.25 (2H, m), 7.33
(5H, m); 13C NMR (CDCl3) dZ26.2 (p), 26.7 (p), 30.8 (s),
35.6 (s), 66.5 (s), 67.4 (t), 72.0 (s), 79.3 (t), 81.6 (t), 82.0 (t),
105.1 (t), 111.7 (q), 126.2 (t), 127.7 (t), 128.1 (t), 128.4 (t),
128.6 (t), 137.1 (q), 140.2 (q), 173.0 (q); HRMS (FAB):
obsd MCHZ443.2065, calcd for C25H31O7 MCHZ
443.2070.
4.5.6. 2-Phenoxyethyl 3-phenylpropanoate (6V). Color-
less solid; mp 52–53 8C; IR (KBr): 1730, 1240, 1160 cmK1
;
1H NMR (CDCl3) dZ2.67 (2H, t, JZ7.8 Hz), 2.95 (2H, t,
JZ7.8 Hz), 4.12 (2H, t, JZ4.7 Hz), 4.42 (2H, t, JZ4.7 Hz),
6.90 (2H, d, JZ7.5 Hz), 6.96 (1H, t, JZ7.5 Hz) 7.19 (3H,
m), 7.26 (4H, m); 13C NMR (CDCl3) dZ30.8 (s), 35.7 (s),
62.8 (s), 65.8 (s), 114.6 (t), 121.1 (t), 126.2 (t), 128.3 (t),
128.5 (t), 129.5 (t), 140.3 (q), 158.4 (q), 172.8 (q); HRMS
(FAB): obsd MCHZ271.1324, calcd for C17H19O3 MC
HZ271.1334.
4.5.7. (Tetrahydrofuran-2-yl)methyl 3-phenyl-propano-
4.5.12. Octyl pentanoate (6II0). Oil; IR (neat): 1735,
1170 cmK1; 1H NMR (CDCl3) dZ0.88 (3H, t, JZ7.0 Hz),
0.92 (3H, t, JZ7.4 Hz), 1.22–1.38 (12H, m), 1.61 (4H, m),
2.30 (2H, t, JZ7.4 Hz), 4.06 (2H, t, JZ6.7 Hz); 13C NMR
(CDCl3) dZ13.7 (p), 14.0 (p), 22.3 (s), 22.6 (s), 25.9 (s),
1
ate (6VIII). Oil; IR (neat): 1730, 1160, 1075 cmK1; H
NMR (CDCl3) dZ1.55 (2H, m), 1.90 (3H, m), 2.68 (2H, t,
JZ8.0 Hz), 2.96 (2H, t, JZ8.0 Hz), 3.79 (1H, m), 3.87 (1H,
m), 4.01 (1H, m), 4.09 (1H, m), 4.16 (1H, m), 7.23 (3H, m),

5924
N. Mori, H. Togo / Tetrahedron 61 (2005) 5915–5925
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¨
5. (a) Farkas, L.; Schachter, O. J. Am. Chem. Soc. 1949, 71, 2827.
27.1 (s), 28.6 (s), 29.2 (s), 31.8 (s), 34.1 (s), 64.4 (s), 174.0
(q); HRMS (EI): obsd MCZ214.1940, calcd for C13H26O2
MCZ214.1933.
(b) Perlmutter-Hayman, B.; Weissmann, Y. J. Am. Chem. Soc.
1969, 91, 668. (c) Kageyama, T.; Kawahara, S.; Kitamura, K.;
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4.6. Typical procedure for oxidation of secondary
alcohols to ketones
To a solution of (K)-menthol (1 mmol) in t-butyl alcohol
(1 ml) were added I2 (2 mmol) and K2CO3 (2 mmol) under
an argon atmosphere. The mixture obtained was stirred at
90 8C. After 16 h at the same temperature, the mixture was
quenched with satd aq Na2SO3 (3–5 ml) at 0 8C, and was
extracted with Et2O three times. The organic layer was
washed with brine and dried over Na2SO4 to provide (K)-
menthone in 99% yield in an almost pure state. If necessary,
the product was purified by flash column chromatography
on silica gel (hexane–EtOAcZ4:1) to give pure (K)-
menthone as an oil.36 1H NMR (CDCl3) dZ0.85 (3H, d, JZ
6.8 Hz), 0.92 (3H, d, JZ6.8 Hz), 1.01 (3H, d, JZ6.1 Hz),
1.28–1.45 (2H, m), 1.79–2.20 (6H, m), 2.35 (1H, m).
6. Otera, J. Esterification; Wiley: New York, 2003.
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1
4.6.1. 2,3,5-Tri-O-benzyl-D-ribofuranone. Oil; H NMR
(CDCl3) dZ3.52 (1H, dd, JZ11.1, 2.7 Hz), 3.62 (1H, dd,
JZ11.1, 2.7 Hz), 4.08 (1H, dd, JZ5.6, 1.7 Hz), 4.41 (3H,
m), 4.53 (2H, m), 4.67 (1H, d, JZ11.9 Hz), 4.72 (1H, d, JZ
11.9 Hz), 4.91 (1H, d, JZ11.9 Hz), 7.18 (2H, m), 7.25–7.37
(13H, m); 13C NMR (CDCl3) dZ68.6 (s), 72.2 (s), 72.6 (s),
73.4 (s), 73.6 (t), 75.2 (t), 81.6 (t), 127.4 (t), 127.8 (t), 127.9
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Acknowledgements
Financial support from Forum on Iodine Utilization is
gratefully acknowledged.
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