Efficient method for the preparation of inverted alkyl carboxylates and phenyl carboxylates via oxidation-reduction condensation using 2,6-dimethyl-1,4-benzoquinone or simple 1,4-benzoquinone

Article abstract of DOI:10.1246/bcsj.77.1569

Oxidation-reduction condensation using in situ formed alkoxydiphenylphosphines, 2,6-dimethy-1,4-benzoquinone, and carboxylic acids provides a useful method for the preparation of inverted tertiary alkyl carboxylates from the corresponding chiral tertiary alcohols under mild and neutral conditions. Similarly, it has afforded alkyl carboxylates successfully in good-to-high yields by the combined use of alkoxydiphenylphosphines having primary, secondary, or tertiary alkoxy groups, carboxylic acids, and simple 1,4-benzoquinone. When chiral secondary or tertiary alcohols are used, the corresponding inverted secondary or tertiary alkyl carboxylates are also obtained in good-to-high yields. In addition, a convenient method for the preparation of phenyl carboxylates in high yields has been established by utilizing oxidation-reduction condensation in toluene at 110 °C using phenoxydiphenylphosphines in situ-formed from phenols and chlorodiphenylphosphine, 2,6-dimethyl-1,4-benzoquinone, and carboxylic acids.

Full text of DOI:10.1246/bcsj.77.1569

Ó 2004 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 77, 1569–1579 (2004) 1569
Efficient Method for the Preparation of Inverted Alkyl Carboxylates
and Phenyl Carboxylates via Oxidation–Reduction Condensation
Using 2,6-Dimethyl-1,4-benzoquinone or Simple 1,4-Benzoquinone
ꢀ;1;2
Taichi Shintou,1 Kentaro Fukumoto,1 and Teruaki Mukaiyama
1Center for Basic Research, The Kitasato Institute, 6-15-5 Toshima, Kita-ku, Tokyo 114-0003
2Kitasato Institute for Life Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641
Received March 4, 2004; E-mail: Mukaiyam@abeam.ocn.ne.jp
Oxidation–reduction condensation using in situ formed alkoxydiphenylphosphines, 2,6-dimethy-1,4-benzoquinone,
and carboxylic acids provides a useful method for the preparation of inverted tertiary alkyl carboxylates from the corre-
sponding chiral tertiary alcohols under mild and neutral conditions. Similarly, it has afforded alkyl carboxylates success-
fully in good-to-high yields by the combined use of alkoxydiphenylphosphines having primary, secondary, or tertiary al-
koxy groups, carboxylic acids, and simple 1,4-benzoquinone. When chiral secondary or tertiary alcohols are used, the
corresponding inverted secondary or tertiary alkyl carboxylates are also obtained in good-to-high yields. In addition, a
convenient method for the preparation of phenꢁyl carboxylates in high yields has been established by utilizing oxida-
tion–reduction condensation in toluene at 110 C using phenoxydiphenylphosphines in situ-formed from phenols and
chlorodiphenylphosphine, 2,6-dimethyl-1,4-benzoquinone, and carboxylic acids.
Oxidation–reduction condensation using a combination
of 2,6-dimethyl-1,4-benzoquinone and alkoxydiphenylphos-
phines formed in situ from alcohols and chrolodiphenylphos-
phine or N,N-(dimethylamiono)diphenylphosphine proceeded
smoothly just from the corresponding alcohols and carboxylic
acids in a one-pot procedure to afford alkyl carboxylates in high
yields.1 Esterification of various chiral secondary alcohols pro-
ceeded smoothly to afford the corresponding esters in high
yields with a perfect inversion of the stereochemistry.1 It was
also shown that the reaction of various carboxylic acids with
tertiary alkoxydiphenylphosphines formed in situ, e.g., 2,2-di-
methylpropionic acid and 2-methyl-1-phenylpropan-2-ol, or
2-phenylbutyric acid and 1-adamantanol, afforded the corre-
sponding t-alkyl carboxylates in 85 to 96% yields, respective-
ly.1 Thus, the possibility of the inversion of t-alkyl alcohol in
this ester-forming reaction was further examined and the chiral
tertiary alcohols were converted into their corresponding esters
with almost complete inversion of the configuration by oxida-
tion–reduction condensation (Scheme 1).2 In addition, the ole-
fins produced from tertiary alcohols, except for the case using
(S)-2-(4-methoxypheny)-2-butanol, were not observed because
they proceeded under ‘‘mild and neutral’’ conditions without
having any assistance of acids or bases. In order to develop
practical and convenient reactions, condensation using simple
O
O
O
O
Ph2P
Ph2P
R1
O
OH
2
1. nBuLi
2. Ph2PCl
O
or
R3
R1
R3
R3
R1
R2
R2
R2
O
O
1
4
3
O
O
O
OH
O
R2
Ph2P
R1
OPPh2
OPPh2
R1
RCOOH
R3
or
+
R3
RCOO
OH
OH
R2
RCOO
6
"Inversion"
7
5
Scheme 1.
Published on the web August 6, 2004; DOI 10.1246/bcsj.77.1569

1570 Bull. Chem. Soc. Jpn., 77, No. 8 (2004)
Oxidation–Reduction Condensation
n
1. BuLi
O
Ph2P
OH
2. Ph PCl
2
O
O
8
O
O
O
R
O
R
O
O
O
O
+
6
O
Ph
Ph
Ph
Ph
Ph
Ph
O
P
R
O
P
P
R
O
O
OH
O
OH
H O
9
10
11
Scheme 2.
1,4-benzoquinone was tried instead of the above-mentioned
2,6-dimethyl-1,4-benzoquinone, and the desired reaction pro-
ceeded smoothly to afford alkyl carboxylates in good-to-high
yields by using a combination of alkoxydiphenylphosphines
having primary, bulky secondary or tertiary alkoxy groups,
1,4-benzoquinone, and carboxylic acids (Scheme 1).3 In the
case of chiral secondary or tertiary alcohols, the corresponding
inverted carboxylates were also obtained in good-to-high
yields.3 In order to extend the scope of these reactions, the for-
mation of phenyl carboxylates by condensation reactions of
phenols with carboxylic acids was further studied by using in
situ-formed phenoxydiphenylphosphines instead of the above-
mentioned alkoxydiphenylphosphines, and the above conden-
and benzoic acid or hydrocinnamic acid was refluxed for 15
h, the desired esters were obtained in 78% chemical yield with
98% inversion or 76% chemical yield with 40% inversion, re-
spectively (Table 1, entries 2 and 3), whereas the corresponding
olefin was formed in 81% yield in the case of 2-(4-methoxy-
phenyl)-2-buthanol, and no desired esters were detected
(Table 1, entry 15).
Next, the esterifications of (ꢂ)-linalool with benzoic acid
having electron-donating or electron-withdrawing groups at
the o-position or the m-position, such as o-nitrobenzoic acid,
m-nitrobenzoic acid, or m-chlorobenzoic acid or o-methoxy-
benzoic acid, were tried and the corresponding esters were ob-
tained in 75–79% chemical yields with 94–99% inversion after
having been allowed to react for 18 h at room temperature
(Table 2, entries 1–3, and 5).
ꢁ
sation proceeded smoothly in toluene at 110 C and afforded
the corresponding phenyl carboxylates in high yields under
neutral conditions (Scheme 2).
Thus, oxidation–reduction condensation using in situ-
formed alkoxydiphenylphosphines, 2,6-dimethyl-1,4-benzo-
quinone, and carboxylic acids provided a new and efficient
method for the preparation of inverted t-alkyl carboxylates
from various chiral tertiary alcohols.
Results and Discussion
Preparation of Inverted t-Alkyl Carboxylates from
Chiral t-Alcohols by a New Type of Oxidation–Reduction
Condensation Using 2,6-Dimethy-1,4-benzoquinone.
In
Efficient Method for the Preparation of Primary,
Inverted Secondary, and Tertiary Alkyl Carboxylates from
Alcohols and Carboxylic Acids by Oxidation–Reduction
Condensation Using Simple 1,4-Benzoquinone. First, when
benzyl alcohol and benzoic acid were treated with 1.0 equiva-
lent of 1,4-benzoquinone in dichloromethane, benzyl benzoate
was obtained in 75% yield within 3 h (Table 3, entry 1). When
1.0 equivalent each of 1,4-benzoquinone and benzoic acid were
used, the yields of the desired ester were not influenced by the
amount of benzyloxydiphenylphosphine (Table 3, entries 1–4).
Next, the above effect was further investigated by using the
same equivalents; each of benzyloxydiphenylphosphine and
1,4-benzoquinone were used (Table 3, entries 5–9). As a result,
the ester was obtained in 98% yield when 1.7 equivalents each
of the in situ-formed benzyloxydiphenylphosphine and 1,4-
benzoquinone were treated with 1.0 equivalent of benzoic acid
at room temperature for 1 h (Table 3, entry 8, and Fig. 1).
Next, esterifications of the in situ-formed alkoxydiphenyl-
phosphines from alcohols and chlorodiphenylphosphine with
various carboxylic acids were tried; the result are shown in
Table 4. Benzylation of benzoic acids having electron-donating
or electron-withdrawing groups and saturated or unsaturated
aliphatic carboxylic acids proceeded smoothly to afford the
corresponding benzyl carboxylates in high-to-excellent yields
the first place, alkylations of several carboxylic acids with 1.2
equivalents of chiral tertiary alkoxydiphenylphosphines formed
in situ from chiral nBuLi treated tertiary alcohols and chlorodi-
phenylphosphine were tried by using 1.0 equivalent of 2,6-di-
methyl-1,4-benzoquinone in dichloromethane at room temper-
ature. Condensations of carboxylic acids with various chiral
tertiary alcohols proceeded smoothly to afford the correspond-
ing t-alkyl carboxylates in good yields with almost complete in-
version of stereochemistries; the results are shown in Table 1.
When a CH2Cl2 solution of 1-adamantanol and benzoic acid
was refluxed for 15 h, the corresponding ester was obtained
in 83% yield with the retention of stereochemistry because of
its rigid structure (Table 1, entry 1). When benzoic acid or p-
methoxybenzoic acid having an electron-donating group was
used, esterifications using various chiral tertiary alcohols pro-
ceeded within 18 h at room temperature to afford the corre-
sponding alkyl esters in good yields (81–90%) with almost
complete inversion of the stereochemistries (98 to >99%)
(Table 1, entries 4, 5, 8, 9, and 12–14). When hydrocinnamic
acid (3-phenylpropionic acid) or p-chlorobenzoic acid was
used, on the other hand, the desired esters were obtained in
76–86% yields with 70–84% inversion (Table 1, entries 6, 7,
10, and 11). When a CH2Cl2 solution of (ꢂ)-terpinen-4-ol

T. Shintou et al.
Bull. Chem. Soc. Jpn., 77, No. 8 (2004) 1571
Table 1. Esterification between Several Carboxylic Acids and Various Chiral Tertiary Alcohols
R2COOH (1.0 equiv.)
(1.0 equiv.)
1.nBuLi
O
R1OH
Ph2POR1
R2
OR1
2. Ph2PCl
O
O
(1.2 equiv.)
CH2Cl2, rt, 18h
Entry
R1OHc)
R/Sd)
R2
Product
Yield/%
R/Se)
Inversion/%
1a)
Ph
20
83
0
HO
12
13
2a)
3a)
Ph
21
22
78
76
16/84
66/34
98
40
(R)
OH
86/14
95/5
PhCH2CH2−
4
5
6
7
Ph
23
24
25
26
85
86
83
76
7/93
5/95
98
>99
84
OH
(R)
p-MeO−C6H4−
p-Cl−C6H4−
PhCH2CH2−
20/80
24/76
80
14
15
8
9
Ph
27
28
29
30
90
88
86
86
98/2
>99
>99
71
Et
OH
p-MeO−C6H4−
p-Cl−C6H4−
PhCH2CH2−
98/2
(S)
2/98
1/99
Ph
10
11
70/30
69/31
70
Et
OH
(S)
12
Ph
31
86
99/1
>99
16
Et
OH
Bu
(R)
13
91/9
Ph
Ph
Ph
32
33
34
83
81
9/91
>99
99
Ph
17
Et OH
(S)
14
22/78
77/23
Ph
18
Et
OH
(S)
15b)
N.D.
MeO
19
a) The reaction mixture was refluxed for 15 h. b) The corresponding olefin was obtained in 81% yield. c)
Entries 2–7: Chiral alcohols of (ꢂ)-terpinen-4-ol (Acros Organics) and (ꢂ)-linalool (Fulka Chemika) were
purchased. Entry 8–15: Chiral alcohols were prepared according to Walsh’s procedure.1 d) The enantiomeric
ratios of t-alcohols were determined by preparing the corresponding esters with the carboxylic chlorides. e)
The conditions of separating the corresponding esters were shown in Ref. 2.
under mild conditions (Table 4, entries 1–6). When 1-butanol
or p-methoxybenzyl alcohol having an electron-donating group
or secondary alcohol, such as benzhydrol, was used, the corre-
sponding esters were obtained in high yields upon a treatment
with benzoic acid for 1–3 h (Table 4, entries 7–9). Similarly,
the reaction of alkoxydiphenylphosphine, in-situ formed from
t-butyl alcohol and chlorodiphenylphosohine, with 1,4-benzo-
quinone and benzoic acid under the same conditions afforded
the desired ester in 75% yield (Table 4, entry 12). Condensa-
tions of tertiary alcohol and carboxylic acid, such as 1-adaman-
tanol and 2-phenylbutyric acid or 1-methylcyclopentanol and
triphenylacetic acid, also proceeded smoothly to afford the cor-
responding alkyl carboxylates in excellent yields (Table 4, en-
tries 13 and 14). It was also noted that the corresponding alkyl
carboxylates were obtained in excellent yields with perfect in-
version of the stereochemistry in the case when a chiral secon-
dary alcohol, such as L-menthol, was used (Table 4, entries 10
and 11). In addition, in the case of using chiral tertiary alcohol

1572 Bull. Chem. Soc. Jpn., 77, No. 8 (2004)
Oxidation–Reduction Condensation
Table 2. Esterification between Several Carboxylic Acids and (ꢂ)-Linalool
R2COOH (1.0 equiv.)
1.nBuLi
O
Ph2POR1
R1OH
R2
OR1
2. Ph2PCl
(1.0 equiv.)
O
O
(1.2 equiv.)
CH2Cl2, rt, 18h
a)
Entry
R1OH
OH
R/S
R2COOH
pKa
Product
Yield/%
R/S
Inversion/%
COOH
NO2
1
2.16
35
79
5/95
>99
(R)
COOH
2
3.47
36
76
11/84
94
O2N
14
COOH
3
4
95/5
3.82b)
4.00
37
25
75
83
6/94
99
84
Cl
20/80
Cl
COOH
COOH
5
4.09
38
77
7/93
98
OMe
6
7
4.19
4.47
23
24
85
86
7/93
5/95
98
COOH
>99
MeO
COOH
a) See Ref. 1. b) See Ref. 4.
n
Table 3. Esterification of Benzoic Acid Using BuLi and Benzyl Alcohols
n
1. BuLi/Hexane
O
PhCOOH (1.0 equiv.)
2. Ph PCl
2
BnOH
Ph2POBn
Ph
OBn
THF
o
O
O
39
0
C-rt, 1.0 h
CH2Cl2
Entry
Ph2POBn/equiv.
Benzoquinone/equiv.
Time/h
Yield/%
1
2
3
4
1.0
1.1
1.3
1.5
1.0
1.0
1.0
1.0
3.0
3.0
3.0
3.0
75
75
74
60
5
6
7
8
9
1.1
1.3
1.5
1.7
1.9
1.1
1.3
1.5
1.7
1.9
1.0
1.0
1.0
1.0
1.0
76
84
93
98
98
10
1.1
1.7
1.0
68
such as (S)-2-phenyl-2-butanol, the corresponding ester was
obtained in 92% yield with 99% inversion.
um.5 Oxidation–reduction condensation using in situ-generated
alkoxydiphenylphosphines, carboxylic acids, and 2,6-dimeth-
yl-1,4-benzoquinone or 1,4-benzoquinone provides a new and
efficient method for the preparation of primary, inverted secon-
dary, and tertiary alkyl carboxylates from the corresponding al-
cohols under mild and neutral condition as described in our pre-
vious reports.1–3 In order to extend the scope of these reactions,
the formation of phenyl carboxylates by the condensation reac-
tion of phenols with carboxylic acids was studied by using in
situ-formed phenoxydiphenylphosphines instead of the above-
mentioned alkoxydiphenylphosphines. First, it was observed
Efficient Method for the Preparation of Phenyl Carboxy-
lates from Phenols and Carboxylic Acids by Oxidation–
Reduction Condensation Using 2,6-Dimethyl-1,4-benzo-
quinone. There are a number of reactions reported concerning
aromatic substitution reactions via the addition–elimination
mechanism.5 These reactions generally proceed smoothly by
using aromatic compounds having electron-withdrawing
groups, such as a nitro or carbonyl group, and nucleophiles with
the assistance of transition metals, such as copper or palladi-

T. Shintou et al.
Bull. Chem. Soc. Jpn., 77, No. 8 (2004) 1573
that the phenyl 4-methoxybenzoate was formed in 22% yield
within 3.0 h at room temperature when p-methoxybenzoic acid
was allowed to react with 1.0 equivalent each of 2,6-dimethyl-
1,4-benzoquinone and phenoxydiphenylphosphine formed in
in dichloromethane (Table 5, entry 1). This phenyl carboxylate
was obtained in 51% yield when the reaction mixture was re-
fluxed for 2.5 h. Yields of phenyl esters were intact regardless
of the reaction time, which was 5.0 h, or the amounts of phen-
oxydiphenylphosphine and 2,6-dimethyl-1,4-benzoquinone,
which was 1.5 equivalents each in that case (Table 5, entries
3 and 4). However, when 1.0 equivalent each of phenoxydi-
phenylphosphine and 2,6-dimethyl-1,4-bemzoquinone were
treated with p-methoxybenzoic acid at 110 ꢁC for 2.0 h, the de-
sired ester was obtained in 64% yield (Table 5, entry 5). Then,
the effect of the amounts of phenoxydiphenylphosphine and
2,6-dimethyl-1,4-benzoquinone (1:1) was further examined
(Table 5, entries 6–10) and, as a consequence, the ester was
obtained in 92% yield when 1.5 equivalents each of the in
situ-formed phenoxydiphenylphosphine and 2,6-dimethyl-1,4-
benzoquinone were treated with 1.0 equivalent of p-methoxy-
benzoic acid at 110 ꢁC for 2.0 h (Table 5, entry 7).
n
situ from BuLi-treated phenol and chlorodiphenylphosphine
100
95
90
85
80
75
70
Next, esterifications using in situ-formed phenoxydiphenyl-
phosphines and various carboxylic acids were tried under the
conditions shown in Table 6. Phenylation of benzoic acids hav-
ing electron-donating or electron-withdrawing groups or satu-
rated and unsaturated aliphatic carboxylic acids proceeded
0.8
1
1.2
1.4
1.6
1.8
2
Ph2POBn/benzoquinone /equiv.
Fig. 1. Esterification of benzoic acid with nBuLi and benzyl
alcohol.
Table 4. Esterifications of Various Carboxylic Acids Using Several Alcohols
1. nBuLi/Hexane
O
RCOOH(1.0 equiv.)
R'OH
R'
Ph2POR'
R
O
2. Ph2PCl
THF, 0 oC-rt, 1 h
O
O (1.7 equiv.)
CH2Cl2
(1.7 equiv.)
Entry
R0OH
BnOH
RCOOH
Product
Time/h
Yield/%
98
Yield/%a)
98
1
PhCOOH
39
1.0
2
3
4
5
6
p-MeO-C6H4COOH
p-NO2-C6H4COOH
PhCH2CH2COOH
PhCH=CHCOOH
CH3(CH2)3COOH
40
41
42
43
44
1.0
1.0
1.0
1.0
1.0
95
96
92
98
90
95
95
93
92
93
7
8
9
p-MeO-C6H4CH2OH
PhCOOH
PhCOOH
45
46
1.0
1.0
93
90
91
88
CH3(CH2)3OH
Ph
PhCOOH
47
3.0
90
94
Ph OH
10b)
11b)
PhCOOH
48
49
3.0
3.0
91 (>99.9%)
96 (>99.9%)
86 (>99.9%)
95 (>99.9%)
p-NO2-C6H4COOH
OH
12
13
PhCOOH
50
51
15.0
15.0
75
95
69
96
OH
O
OH
Ph
HO
Ph
Ph
Ph
14
52
27
15.0
15.0
95
91
OH
COOH
15b)
Et
OH
Me
PhCOOH
95 (>99%)
96 (>99%)
Ph
a) See Ref. 5d. Esterifications of various carboxylic acids with various alcohols by using of 2,6-dimethyl-1,4-benzo-
quinone [alcohols (1.1–1.2 equiv.), carboxylic acids (1.0 equiv.), 2,6-dimethyl-1,4-benzoquinone (1.0 equiv.)].
b) Yields in the parenthesis are inversion.

1574 Bull. Chem. Soc. Jpn., 77, No. 8 (2004)
Oxidation–Reduction Condensation
n
Table 5. Esterification of p-Methoxybenzoic Acid Using BuLi and Phenol
p-MeO-
C6H4-COOH
(1.0 equiv.)
n
O
1. BuLi
2. Ph PCl
2
OPh
PhOH
Ph2POPh
THF
o
MeO
O
O
2
0-rt C, 1.0 h
1
53
Solvent
Entry
1/equiv.
2/equiv.
Solvent
Condition
rt, 3.0 h
reflux, 2.5 h
reflux, 5.0 h
reflux, 5.0 h
Yield/%
1
2
3
4
1.0
1.0
1.0
1.5
1.0
1.0
1.0
1.5
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
22
51
50
52
ꢁ
ꢁ
5
6
7
8
9
10
1.0
1.2
1.5
1.6
1.8
2.0
1.0
1.2
1.5
1.6
1.8
2.0
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
110 C, 2.0 h
110 ꢀ C, 2.0 h
64
77
92
91
82
32
110 C, 2.0 h
ꢁ
110 C, 2.0 h
ꢁ
110 C, 2.0 h
ꢁ
110 C, 2.0 h
Table 6. Esterifications of Various Carboxylic Acids with Phenol
n
1. BuLi
RCOOH (1.0 equiv.)
2. Ph PCl
O
2
PhOH
Ph2POPh
R
OPh
THF
O
O
(1.5 equiv.)
o
(1.5 equiv.)
0-rt C, 1.0 h
Toluene, 110 oC, 2.0 h
Entry
1
RCOOH
Product
Yield/%
92
MeO
COOH
MeO
COOPh
COOPh
COOPh
COOPh
53
54
55
56
COOH
COOH
COOH
2
3
4
88
90
90
Br
Br
O2N
O2N
5
6
COOH
COOPh
57
58
90
92
Ph
Ph
COOH
COOH
COOPh
COOPh
Ph
Ph
7
8
59
60
93
95
COOH
COOPh
smoothly to afford the corresponding phenyl carboxylates in
high yields under neutral conditions (Table 6, entries 1–6).
When bulky secondary or tertiary carboxylic acids, such as 2-
phenylbutyric acid or trimethylacetic acid (2,2-dimethylpro-
pionic acid), were used, the corresponding esters were also ob-
tained in high yields by treating these acids with in situ-formed
phenoxydiphenylphosphine for 2.0 h at 110 ꢁC (Table 6, entries
7 and 8).
Phenyl carboxylates forming reactions by using 2,6-dimeth-
yl-1,4-benzoquinone, p-methoxybenzoic acid, and various
phenoxydiphenylphosphines formed in situ from various
nBuLi-treated phenols and chlorodiphenylphosphine were fur-
ther tried (Table 7). When phenols having electron-donating
or electron-withdrawing groups were used, the corresponding
phenyl carboxylates were obtained in 90 to 94% yields, respec-
tively (Table 7, entries 1 and 2). Esterifications of p-methoxy-
benzoic acid and phenols having methyl groups at the m-posi-
tions, such as 3,5-dimethylphenol, or at the o-positions, such as
2-methylphenol, proceeded smoothly to afford the desired es-
ters in 86–93% yields within 2.0 h (Table 7, entries 3 and 4).
On the other hand, the corresponding phenyl ester was obtained
in 23% yield when ortho-substituted phenol, such as 2,6-di-
methylphenol, was allowed to react under the above conditions
ꢁ
for 6.0 h at 110 C (Table 7, entry 5). When the reaction was
carried out for 2 h at 160 ꢁC using a solvent, such as p-xylene,
the desired product was then obtained in 76% yield (Table 7,

T. Shintou et al.
Bull. Chem. Soc. Jpn., 77, No. 8 (2004) 1575
Table 7. Esterifications of Carboxylic Acid with Various Phenols
MeO-C6H4-COOH
n
1. BuLi
(1.0 equiv.)
O
2. Ph PCl
2
R'OH
Ph2POR'
MeO
THF
o
OR'
O
O
0-rt C, 1.0 h
(1.5 equiv.)
(1.5 equiv.)
Toluene, 110 oC, 2.0 h
Entry
R0OH
Time/h
Product
Yield/%
O
1
MeO
2.0
61
62
90
94
HO
HO
OMe
OMe
NO2
O
O
2a)
MeO
2.0
2.0
2.0
NO2
O
O
MeO
3
63
64
93
86
HO
O
O
4
MeO
HO
HO
O
O
5
6
6.0
2.0
23
76b)
MeO
65
O
OH
O
7
8
2.0
2.0
66
67
86
92
MeO
O
O
HO
MeO
O
a) A corresponding diphenylphosphine was prepared from R0OH, Et3N, and Ph2PCl. b) The reaction
ꢁ
mixture was stirred for 2.0 h in p-xylene at 160 C.
entry 6). The corresponding esters were also obtained in good-
to-high yields when 1-naphthol or 2-naphthol was used
(Table 7, entries 7 and 8).
from PhCOCl and H218O in 93% yield, and the incorporation of
18O was 45%.7 As a result, PhCO18OPh (70) was obtained in
88% yield (45% 18O-incorporation) along with diphenylphos-
phinic acid 4-hydroxy-3,5-dimethylphenyl ester 6 (18O-incor-
poration was not detected). This result thus indicated that the
reaction took place via addition–elimination processes of aro-
matic substitution, as shown in Path A, and that it proceeded
smoothly to afford phenyl carboxylate.
A proposed reaction mechanism of oxidation–reduction con-
densation by the combined use of benzoic acid, 2,6-dimethyl-
1,4-benzoquinone, and phenoxydiphenylphosphine formed in
situ from phenol and chlorodiphenylphosphine is shown in
Scheme 3. Phenoxydiphenylphosphine (8) was assumed to re-
act with 2,6-dimethyl-1,4-benzoquinone to form the intermedi-
ate phosphonium salt (9). The formed phosphonium salt (9)
was, in turn, transformed to the phosphonium carboxylate
(10) by catching one hydrogen atom from the carboxylic acids.
Aromatic substitution took place via addition–elimination
processes after a nucleophilic attack of carboxylate anion of
the intermediate (10), and the corresponding phenyl carbox-
ylate was formed (Scheme 3, Path A). On the other hand, an al-
ternative pathway was considered in which the formed phos-
phonium salt (9) was in turn transformed to the penta-valent
phosphorus compound (68) by catching one hydrogen atom
from the carboxylic acids. A successive nucleophilic attack
of oxygen of the phenol group might afford the phenyl carbox-
ylate (Scheme 3, Path B). In order to examine the above-men-
tioned possible pathways, an 18O-labeling study6 was carried
out by employing a PhCO18OH (69). PhCO18OH was prepared
Conclusion
A new and efficient method for the preparations of inverted
alkyl carboxylates from t-alkoxydiphenylphosphines generated
in situ from chiral tertiary alcohols, 2,6-dimethyl-1,4-benzo-
quionone, and carboxylic acids was established by way of ox-
idation–reduction condensation under a mild condition. It was
also shown that the condensation proceeded successfully to af-
ford alkyl carboxylates in good-to-high yields by the combined
use of alkoxydiphenylphosphines formed in situ from primary,
bulky secondary or tertiary alcohol, simple 1,4-benzoquinone,
and various carboxylic acids. In the case of chiral secondary
or tertiary alcohols, the corresponding inverted carboxylates
were obtained similarly in good-to-high yields. Further, oxida-
tion–reduction condensation using phenoxydiphenylphos-
phines formed in situ from various phenols and chlorodiphenyl-

1576 Bull. Chem. Soc. Jpn., 77, No. 8 (2004)
Oxidation–Reduction Condensation
n
1. BuLi
O
Ph2P
OH
2. Ph PCl
2
O
O
8
O
18O
O
O
Ph
Path A
18O Ph
OPPh2
+
O
O
O
O
O
Ph
Ph
Ph
Ph
Ph
Ph
18O
O
Ph
P
P
P
Ph
O
O
OH
O
OH
18
OH
O
H
70
9
69
10
11
6
O
18O
Ph
18
O
O
OPPh2
O
+
OH
O
P
O
Ph
Ph
Path B
Ph
OH
71
68
Scheme 3.
General Procedure for the Preparation of Carboxylates with
Retention of Stereochemistry.2 Into a stirred solution of chiral t-
alcohol (0.6 mmol) in Et2O (2 mL) was dropped a hexane solution
of nBuLi (0.6 mmol) at 0 ꢁC under argon atmosphere. After the so-
lution was stirred at room temperature for 1.0 h, a Et2O (1 mL)ꢁso-
lution of carboxylic acid chloride (0.6 mmol) was added at 0 C.
The reaction mixture was stirred for 2.0 h at room temperature. Af-
ter completion of the reaction (detected by TLC), it was quenched
with saturated aq NH4Cl, and mixture was extracted with Et2O.
The organic layers were dried over anhydrous sodium sulfate, fil-
tered, and concentrated. The crude product was purified by prepa-
rative TLC to afford the desired product.
General Procedure for the Preparation of Inverted Car-
boxylates.2 Into a stirred solution of chiral t-alcohol (1.5 mmol)
in THF (5 mL) was dropped a hexane solution of nBuLi (1.5 mmol)
at 0 ꢁC under argon atmosphere. After the solution was stirred
at room temperature for 1.0 h, a THF (2 mL) solution of chlorodi-
phenylphosphine (1.5 mmol) was added at 0 ꢁC. The reaction mix-
ture was stirred for 1.0 h at room temperature and the solvent was
concentrated in vacuo. Immediately, carboxylic acid, 2,6-dimeth-
yl-1,4-benzoquinone, and dichloromethane were added to the res-
idue and the mixture was stirred for 18 h at room temperature. The
same result was alternatively obtained by the following procedure;
that is, after the above mentioned residue was diluted with a mixed
solution of hexane (3 mL) and ethyl acetate (0.5 mL), lithium chlo-
ride was removed by filtration through celite (1.0 g) after passing it
through alumina (activated, basic) (Wako Pure Chemical Indus-
tries, LTD) (7 g). The solvent was concentrated in vacuo, and crude
alkoxydiphenylphosphine was obtained. To a mixture of carboxyl-
ic acid (0.60 mmol) and 2,6-dimethyl-1,4-benzoquinone (0.60
mmol) under argon atmosphere was added a dichloromethane
(0.50 mL) solution of the above crude alkoxydiphenylphosphine
under above condition. After the reaction that was monitored by
TLC was completed, the reaction mixture was quenched by adding
water and the aqueous layer was extracted with dichloromethane.
The combined organic layer was dried over anhydrous sodium
sulfate. After filtration and evaporation, the resulting residue was
phosphine, 2,6-dimethy-1,4-benzoquinone, and various car-
boxylic acids proceeded smoothly at 110 ꢁC in toluene to afford
the corresponding phenyl carboxylates in high yields under
neutral conditions via addition–elimination processes of aro-
matic substitution.
Experimental
General Information. All of the melting points were deter-
mined on a Yanagimoto micro melting point apparatus (Yanaco
MP-S3) and were not corrected. Infrared (IR) spectra were record-
ed on a Nicolet AVATAR360 (ATR) or a Horiba FT300 FT-IR
spectrometer (neat). 1H NMR spectra were recorded on a JEOL
JNM EX270L (270 MHz) spectrometer; chemical shifts (ꢀ) are re-
ported in parts per million relative to teteramethylsilane. Splitting
patterns are designated as s, singlet; d, doublet; t, triplet; q, quartet;
m, multiplet; br, broad. 13C NMR spectra were recorded on an
EX270L (68 MHz) spectrometer with complete proton decoupling.
The chemical shifts are reported in parts per million relative to
tetramethylsilane with the solvent resonance as the internal stand-
ard (CDCl3; ꢀ 77.0). High-resolution mass spectra (HRMS) were
reported on a JEOL LCmate. MS spectra were reported on a JEOL
DX-303HF. The polarimeter was used JASCO P-1020. Analytical
high-performance liquid chromatography (HPLC) was performed
on a Hitachi LC-Organizer (L-4000 UV Detector, L-6200 Intelli-
gent Pump, and D-2500 Chromato-Integrator) equipped with a chi-
ral column (ꢁ4:6 ꢃ 250 mm). Analytical TLC was performed on
Merck preparative TLC plates (silica gel 60 GF254, 0.25 mm).
Column chromatography was carried out on Merck silica gel 60
(0.063–0.200 mm). Preparative thin-layer chromatography (PTLC)
was carried out on silica gel Wakogel B-5F. Dry solvents were pre-
pared by distillation under appropriate drying agents. Carboxylic
acids were purified by recrystallization.
General Procedure for the Preparation of Chiral Tertiary
Alcohols. Chiral tertiary alcohols were prepared according to
Walsh’s procedure.2 The characterization of the products (15–19)
were shown in Ref. 2.

T. Shintou et al.
Bull. Chem. Soc. Jpn., 77, No. 8 (2004) 1577
purified by preparative TLC to afford the corresponding carboxylic
esters. The characterization of the products (26–34) were shown in
Ref. 2.
General Procedure for the Preparation of Carboxylates by
Using 1,4-Benzoquinone. Into a mixture of carboxylic acid
(0.30 mmol) and 1,4-benzoquinone (0.30 mmol) under argon at-
mosphere was added a dichloromethane (0.3 mL) solution of alk-
oxydiphenylphosphine (0.51 mmol) at room temperature. After the
reaction that was monitored by TLC was completed, the reaction
mixture was quenched by adding water and the aqueous layer
was extracted with dichloromethane. The organic layers were dried
over anhydrous sodium sulfate. After filtration and evaporation,
the resulting residue was purified by preparative TLC to afford
the corresponding ether. The above reactions were also carried
out by a one-pot procedure, and the same results were obtained
even in the presence of lithium chloride. The characterization of
the products (39–52) were shown in Ref. 1.
1,5-Dimethyl-1-vinyl-4-hexenyl 2-Nitrobenzoate (35). Col-
27
orless oil; R/S = 5/95: ½ꢂꢄD ¼ þ15:3 (c 0.98, CHCl3), R/S =
26
95/5: ½ꢂꢄD ¼ ꢂ14:2 (c 1.04, CHCl3); IR (ATR, cmꢂ1) 1727,
1534, 1292, 1128, 1072, 732; 1H NMR (270 MHz, CDCl3) ꢀ
7.85 (d, J ¼ 7:3 Hz, 1H), 7.73 (d, J ¼ 7:3 Hz, 1H), 7.65–7.60
(m, 2H), 6.10 (dd, J ¼ 10:9, 6.5 Hz, 1H), 5.26–5.08 (m, 3H),
2.02–1.86 (m, 4H), 1.69 (s, 3H), 1.66 (s, 3H), 1.58 (s, 3H);
13C NMR (68 MHz, CDCl3) ꢀ 163.6, 140.5, 132.5, 131.9, 131.3,
129.9, 128.4, 123.6, 123.4, 114.0, 86.1, 40.0, 25.7, 22.8, 22.4,
17.7; HRMS (EIþ) calcd for C17H21NO4 [M]þ 303.1470, found
m=z 303.1484; HPLC analysis: DAICEL CHIRALCEL OD
(ꢁ4:6 ꢃ 250 mm), hexane/isopropyl alcohol = 900/1, flow rate:
Diphenylphosphinic Acid 4-Hydroxyphenyl Ester (7). Iso-
lated as a white solid; mp 169–171 ꢁC; IR (ATR, cmꢂ1) 3188,
ꢁ
0.5 mL/min, Temp.: 25 C, detector: 254 nm, S (tR ¼ 34:2 min),
1
R (tR ¼ 28:4 min).
1505, 1435, 1186, 1129, 910, 730; H NMR (270 MHz, CDCl3)
1,5-Dimethyl-1-vinyl-4-hexenyl 3-Nitrobenzoate (36). Col-
27
ꢀ 7.88–7.81 (m, 2H), 7.66–7.41 (m, 8H), 6.92–6.80 (m, 2H),
6.58–6.46 (m, 2H); 13C NMR (68 MHz, CDCl3) ꢀ 132.5, 131.9
(d, J ¼ 10:6 Hz), 131.6 (d, J ¼ 10:6 Hz), 128.7 (d, J ¼ 1:1 Hz),
128.6 (d, J ¼ 2:2 Hz), 121.5 (d, J ¼ 4:5 Hz), 119.4, 116.4 (d, J ¼
1:1 Hz); HRMS (APCIþ) calcd for C18H16O3P ½M þ Hꢄþ
311.0837, found m=z 311.0831.
orless oil; R/S = 11/89: ½ꢂꢄD ¼ þ15:5 (c 1.04, CHCl3), R/S
25
= 95/5: ½ꢂꢄD ¼ ꢂ16:4 (c 1.93, CHCl3); IR (ATR, cmꢂ1
)
1722, 1534, 1350, 1292, 1263, 1133; 1H NMR (270 MHz, CDCl3)
ꢀ 8.82 (d, J ¼ 1:6 Hz, 1H), 8.42–8.31 (m, 2H), 7.67–7.61 (m, 1H),
6.10 (dd, J ¼ 10:9, 6.5 Hz, 1H), 5.32–5.13 (m, 3H), 2.08–1.94 (m,
4H), 1.72 (s, 3H), 1.65 (s, 3H), 1.60 (s, 3H); 13C NMR (68 MHz,
CDCl3) ꢀ 162.8, 148.1, 140.9, 153.0, 133.2, 132.1, 129.4, 127.0,
124.3, 123.3, 113.9, 85.0, 39.9, 25.7, 23.6, 22.6, 17.7; HRMS
(EIþ) calcd for C17H21NO4 [M]þ 303.1470, found m=z
303.1450; HPLC analysis: DAICEL CHIRALCEL OD (ꢁ4:6 ꢃ
250 mm), hexane/isopropyl alcohol = 900/1, flow rate: 0.5 mL/
min, Temp.: 25 ꢁC, detector: 254 nm, S (tR ¼ 21:8 min), R
(tR ¼ 18:3 min).
General Procedure for the Preparation of Phenyl Car-
boxylates. Into a mixture of carboxylic acid (0.30 mmol) and
2,6-dimethyl-1,4-benzoquinone (0.45 mmol) under argon atmo-
sphere was added a toluene (0.35 mL) solution of phenoxydiphenyl-
phosphine (0.45 mmol) at room temperature. The reaction mixture
was stirred for 2 h in toluene while keeping the temperature of the
oil bath at 110 ꢁC. After the reaction monitored by TLC was com-
pleted, the mixture was cooled down to room temperature. Water
was then added to quench the mixture and the aqueous layer was
extracted with dichloromethane. The dichloromethane solution
was dried over anhydrous sodium sulfate. After filtration and
evaporation, the resulting residue was purified by preparative
TLC to afford the corresponding ester. The above reactions could
also be carried out by a one-pot procedure, and the same results
were obtained in the coexistence of lithium chloride.
Phenyl 4-Methoxybenzoate (53).8 White solid; mp 67–69 ꢁC
(lit.8a mp 67–69 ꢁC); IR (ATR, cmꢂ1) 1723, 1254, 1193, 1161,
1075, 743; 1H NMR (270 MHz, CDCl3) ꢀ 8.16 (d, J ¼ 8:9 Hz,
2H), 7.45–7.39 (m, 2H), 7.29–7.19 (m, 3H), 6.98 (d, J ¼ 8:9 Hz,
2H), 3.90 (s, 3H); 13C NMR (68 MHz, CDCl3) ꢀ 164.8, 163.7,
150.9, 132.2, 129.3, 125.6, 121.7 (ꢃ2), 113.7, 55.5; HRMS
(ACPIþ) calcd for C14H13O3 [M]þ 229.0865, found m=z 229.0871.
Phenyl Benzoate (54).8a,9 White solid; mp 71–72 ꢁC (lit.8a mp
70–72 ꢁC); IR (ATR, cmꢂ1) 1726, 1257, 1196, 1060, 749; 1H NMR
(270 MHz, CDCl3) ꢀ 8.22–8.19 (m, 2H), 7.64–7.61 (m, 2H), 7.54–
7.40 (m, 4H), 7.30–7.20 (m, 3H); 13C NMR (68 MHz, CDCl3) ꢀ
165.0, 150.8, 133.5, 130.1, 129.5, 129.4, 12þ8.5, 125.8, 121.6;
HRMS (ACPIþ) calcd for C13H11O2 ½M þ Hꢄ 199.0759, found
m=z 199.0764.
1,5-Dimethyl-1-vinyl-4-hexenyl 3-Chlorobenzoate (37).
25
Colorless oil; R/S = 6/94: ½ꢂꢄD ¼ þ16:8 (c 1.02, CHCl3), R/
25
S = 95/5: ½ꢂꢄD ¼ ꢂ16:5 (c 0.82, CHCl3); IR (ATR, cmꢂ1
)
1
1719, 1288, 1256, 1128, 1072, 746; H NMR (270 MHz, CDCl3)
ꢀ 7.97–7.96 (m, 1H), 7.91–7.87 (m, 1H), 7.52–7.49 (m, 1H),
7.39–7.34 (m, 1H), 6.08 (dd, J ¼ 11:1, 6.5 Hz, 1H), 5.29–5.12
(m, 3H), 2.05–1.93 (m, 4H), 1.69 (s, 3H), 1.65 (s, 3H), 1.59 (s,
3H); 13C NMR (68 MHz, CDCl3) ꢀ 141.3, 134.3, 132.5, 131.9,
129.5, 129.4, 127.5, 123.6, 113.6, 84.2, 77.2, 40.0, 25.7, 23.7,
22.6, 17.7; HRMS (EIþ) calcd for C17H21ClO2 [M]þ 292.1230,
found m=z 292.1236; HPLC analysis: DAICEL CHIRALCEL
OD (ꢁ4:6 ꢃ 250 mm), hexane/isopropyl alcohol = 900/1, flow
ꢁ
rate: 0.5 mL/min, Temp.: 25 C, detector: 254 nm, S (tR ¼ 15:0
min), R (tR ¼ 12:7 min).
1,5-Dimethyl-1-vinyl-4-hexenyl 2-Methoxybenzoate (38).
26
Colorless oil; R/S = 7/93: ½ꢂꢄD ¼ þ16:8 (c 1.00, CHCl3), R/
28
S = 95/5: ½ꢂꢄD ¼ ꢂ17:4 (c 1.33, CHCl3); IR (ATR, cmꢂ1
)
1
1703, 1249, 1077, 754; H NMR (270 MHz, CDCl3) ꢀ 7.78–7.76
(m, 1H), 7.44–7.41 (m, 1H), 6.97–6.94 (m, 2H), 6.08 (dd,
J ¼ 10:9, 6.5 Hz, 1H), 5.30–5.14 (m, 3H), 3.88 (s, 3H), 2.05–
1.88 (m, 4H), 1.68 (s, 3H), 1.66 (s, 3H), 1.59 (s, 3H); 13C NMR
(68 MHz, CDCl3) ꢀ 164.7, 159.0, 141.9, 132.9, 131.6, 131.4,
123.8, 121.3, 119.9, 113.0, 111.9, 83.5, 55.8, 40.0, 25.7, 24.0,
22.5, 17.6; HRMS (EIþ) calcd for C18H24O3 [M]þ 288.1725,
found m=z 288.1732; HPLC analysis: DAICEL CHIRALCEL OJ
(ꢁ4:6 ꢃ 250 mm), hexane/isopropyl alcohol = 1000/1, flow rate:
0.5 mL/min, Temp.: 25 ꢁC, detector: 254 nm, S (tR ¼ 22:9 min), R
(tR ¼ 26:1 min).
Phenyl 4-Bromobenzoate (55).8b,10 White solid; mp 117–118
ꢁC (lit.10 mp 116–117 ꢁC); IR (ATR, cmꢂ1) 1729, 1265, 1075, 747;
1H NMR (270 MHz, CDCl3) ꢀ 8.06 (d, J ¼ 8:5 Hz, 2H), 7.66 (d,
J ¼ 8:5 Hz, 2H), 7.47–7.41 (m, 2H), 7.31–7.19 (m, 3H); 13C NMR
(68 MHz, CDCl3) ꢀ 164.3, 150.6, 131.8, 131.5, 129.4, 128.7,
128.3, 126.0, 121.5; HRMS (ACPIþ) calcd for C13H10BrO2 ½M þ
Hꢄþ 276.9864, found m=z 276.9871.
Diphenylphosphinic Acid 4-Hydroxy-3,5-dimethylphenyl
Ester (6). The characterization of the title compound was shown
in Ref. 1.
Phenyl 4-Nitrobenzoate (56).8b,11 White solid; mp 128–129
ꢁC (lit.11 mp 128–129 ꢁC); IR (ATR, cmꢂ1) 1739, 1520, 1265,
1180, 1075, 755; 1H NMR (270 MHz, CDCl3) ꢀ 8.38–8.37 (m,

1578 Bull. Chem. Soc. Jpn., 77, No. 8 (2004)
Oxidation–Reduction Condensation
4H), 7.49–7.44 (m, 2H), 7.34–7.32 (m, 1H), 7.26–7.22 (m, 2H);
13C NMR (68 MHz, CDCl3) ꢀ 163.0, 150.6, 150.2, 134.7, 131.1,
129.5, 126.2, 123.5, 121.2; HRMS (ACPIꢂ) calcd for C13H9NO4
[M]þ 243.0532, found m=z 243.0524.
2,6-Dimethylphenyl 4-Methoxybenzoate (65).19 Colorless
1
oil; IR (ATR, cmꢂ1) 1725, 1604, 1252, 1156, 764; H NMR (270
MHz, CDCl3) ꢀ 8.20 (d, J ¼ 8:9 Hz, 2H), 2.96 (s, 3H), 7.00 (d, J ¼
8:9 Hz, 2H), 3.89 (s, 3H), 2.18 (s, 6H); 13C NMR (68 MHz, CDCl3)
ꢀ 163.7, 148.2, 132.1, 130.3, 128.4, 125.6, 121.5, 120.0, 113.8,
55.5, 16.5; HRMS (ACPIþ) calcd for C16H17O3 ½M þ Hꢄþ
257.1178, found m=z 257.1186.
Phenyl Pentanoate (57).12 Colorless oil; IR (ATR, cmꢂ1
)
1756, 1195, 1140, 1099; 1H NMR (270 MHz, CDCl3) ꢀ 7.40–
7.34 (m, 2H), 7.24–7.18 (m, 1H), 7.09–7.05 (m, 2H), 2.56 (t, J ¼
7:4 Hz, 2H), 1.80–1.69 (m, 2H), 1.49–1.41 (m, 2H), 0.97 (t, J ¼
7:4 Hz, 3H); 13C NMR (68 MHz, CDCl3) ꢀ 172.1, 150.6, 129.3,
125.6, 121.5, 34.2, 27.1, 22.3, 13.8; HRMS (ACPIþ) calcd for
C11H15O2 ½M þ Hꢄþ 179.1072, found m=z 179.1073.
Naphthalen-1-yl 4-Methoxybenzoate (66).20 White solid; mp
108–109 ꢁC; IR (ATR, cmꢂ1) 1723, 1600, 1253, 1079, 763;
1H NMR (270 MHz, CDCl3) ꢀ 8.29 (d, J ¼ 9:0 Hz, 2H), 7.95–
7.87 (m, 2H), 7.79–7.76 (m, 1H), 7.54–7.47 (m, 3H), 7.37–7.34
(m, 1H), 7.04 (d, J ¼ 9:0 Hz, 2H), 3.92 (s, 3H); 13C NMR (68
MHz, CDCl3) ꢀ 163.9, 146.8, 134.6, 132.3, 127.9, 127.5, 127.0,
126.3, 125.8, 125.4, 121.5, 121.2, 118.2, 113.9, 108.4, 55.6; HRMS
(ACPIþ) calcd for C18H15O3 ½M þ Hꢄþ 279.1021, found m=z
279.1025.
ꢁ
Phenyl Cinnamate (58).13 White solid; mp 76–78 C (lit.13b
ꢁ
1
mp 76–78 C); IR (ATR, cmꢂ1) 1723, 1306, 1140, 762; H NMR
(270 MHz, CDCl3) ꢀ 7.87 (d, J ¼ 15:9 Hz, 1H), 7.57 (m, 2H),
7.43–7.38 (m, 5H), 7.28–7.16 (m, 3H), 6.64 (d, J ¼ 15:9 Hz,
1H); 13C NMR (68 MHz, CDCl3) ꢀ 165.2, 150.6, 146.4, 134.0,
130.6, 129.3, 128.9, 128.2, 125.7, 121.5, 117.2; HRMS (ACPIþ)
calcd for C15H13O2 ½M þ Hꢄþ 225.0916, found m=z 225.0921.
Phenyl 2-Phenylbutylate (59).14 Colorless oil; IR (ATR,
cmꢂ1) 1752, 1192, 1133, 727; 1H NMR (270 MHz, CDCl3) ꢀ
7.41–7.29 (m, 7H), 7.20–7.15 (m, 1H), 6.99–6.96 (m, 2H), 3.69
(t, J ¼ 7:7 Hz, 1H), 2.28–2.17 (m, 1H), 1.95–1.85 (m, 1H), 0.99
(t, J ¼ 7:3 Hz, 3H); 13C NMR (68 MHz, CDCl3) ꢀ 172.4, 150.6,
138.4, 129.2, 128.6, 127.9, 127.3, 125.6, 121.3, 53.5, 26.8, 12.2;
HRMS (ACPIþ) calcd for C16H17O2 ½M þ Hꢄþ 241.1229, found
m=z 241.1227.
Naphthalen-2-yl 4-Methoxybenzoate (67).21 White solid; mp
113–114 ꢁC (lit.21 mp 113–114 ꢁC); IR (ATR, cmꢂ1) 1720, 1260,
1
1153, 1060, 750; H NMR (270 MHz, CDCl3) ꢀ 8.20 (d, J ¼ 8:8
Hz, 2H), 7.91–7.80 (m, 3H), 7.68 (m, 1H), 7.49–7.47 (m, 2H),
7.37–7.24 (m, 1H), 7.00 (d, J ¼ 8:8 Hz, 2H), 3.90 (s, 3H);
13C NMR (68 MHz, CDCl3) ꢀ 164.9, 163.7, 148.5, 133.7, 132.2,
131.3, 129.3, 127.7, 127.5, 126.4, 125.5, 121.7, 121.3, 118.6,
113.8, 55.5; HRMS (ACPIþ) calcd for C18H15O3 ½M þ Hꢄþ
279.1021, found m=z 279. 1014.
Benzoic Acid [PhCO18OH] (69).7 Into a stirred solution of
benzoyl chrolide (56 mmol) in pyridine (20 mL) was dropped a
H218O (56 mmol) at room temperature under argon atmosphere.
After the solution was stirred at room temperature for 18 h, concen-
trated HCl was added (pH 1). The solution was extracted with Et2O
(20 mL ꢃ 5) and the combined organic layer was dried over anhy-
drous sodium sulfate. After filtration and evaporation, the resulting
residue was purified by recrystallization (from EtOH) to afford the
title compound (69) (6.4 g, 93%) as a white solid: mp 122–123 ꢁC;
IR (ATR, cmꢂ1) 3069–2539, 1662, 1276, 930; 1H NMR (270 MHz,
CDCl3) ꢀ 12.7 (br, 1H), 8.17–8.11 (m, 2H), 7.67–7.44 (m, 3H);
13C NMR (68 MHz, CDCl3) ꢀ 172.4, 134.4, 133.7, 130.4, 130.1,
129.2, 128.8, 128.4; HRMS (ACPIꢂ) calcd for C7H5O18O [M]þ
123.0333, found m=z 123.0332 (45% 18O-incorporation), calcd
for C7H5O2 [M]þ 121.0298, found m=z 121.0290.
Phenyl Benzoate [PhCO18OPh] (70). White solid: mp 69–70
ꢁC; IR (ATR, cmꢂ1) 1727, 1696, 1257, 1196, 1060, 749; 1H NMR
(270 MHz, CDCl3) ꢀ 8.22–8.19 (m, 2H), 7.63–7.40 (m, 6H), 7.29–
7.20 (m, 2H); 13C NMR (68 MHz, CDCl3) ꢀ 150.8, 133.5, 130.1,
129.5, 129.4, 128.5, 125.8, 121.6; HRMS (ACPIþ) calcd for
C13H10O18O ½M þ Hꢄþ 201.0804, found m=z 201.0802 (45%
18O-incorporation), calcd for C13H10O2 ½M þ Hꢄþ 199.0754,
found m=z 199.0757.
Phenyl 2,2-Dimethylpropionate (60).15
Colorless oil; IR
(ATR, cmꢂ1) 1748, 1194, 1110, 740; 1H NMR (270 MHz, CDCl3)
ꢀ 7.40–7.34 (m, 2H), 7.23–7.21 (m, 1H), 7.06–7.03 (m, 2H), 1.36
(s, 9H); 13C NMR (68 MHz, CDCl3) ꢀ 176.9, 150.9, 129.2, 125.5,
121.4, 39.1, 27.2; HRMS (ACPIþ) calcd for C11H15O2 ½M þ Hꢄþ
179.1072, found m=z 179.1079.
4-Methoxyphenyl 4-Methoxybenzate (61).16 White solid; mp
124–125 ꢁC (lit.16 mp 125 ꢁC); IR (ATR, cmꢂ1) 1721, 1509, 1246,
1189, 1164, 1024, 763; 1H NMR (270 MHz, CDCl3) ꢀ 8.14 (d, J ¼
8:9 Hz, 2H), 7.11 (d, J ¼ 8:9 Hz, 2H), 6.98 (d, J ¼ 8:9 Hz, 2H),
6.93 (d, J ¼ 8:9 Hz, 2H), 3.89 (s, 3H), 3.82 (s, 3H); 13C NMR
(68 MHz, CDCl3) ꢀ 165.1, 163.6, 157.0, 144.3, 132.1, 122.4,
121.8, 114.4, 113.7, 55.7, 55.5; HRMS (ACPIþ) calcd for
C15H15O4 ½M þ Hꢄþ 259.0970, found m=z 259.0966.
4-Nitrophenyl 4-Methoxybenzoate (62).11,17 White solid; mp
167–168 ꢁC (lit.11 mp 167 ꢁC); IR (ATR, cmꢂ1) 1732, 1512, 1264,
1208, 1164, 1063, 1010, 838, 758; 1H NMR (270 MHz, CDCl3) ꢀ
8.32 (d, J ¼ 8:9 Hz, 2H), 8.15 (d, J ¼ 8:9 Hz, 2H), 7.41 (d, J ¼ 8:9
Hz, 2H), 7.01 (d, J ¼ 8:9 Hz, 2H), 3.92 (s, 3H); 13C NMR (68
MHz, CDCl3) ꢀ 168.0, 163.8, 161.2, 149.2, 132.4, 126.1, 125.1,
122.6, 114.0, 55.6; HRMS (ACPIþ) calcd for C14H12NO5 ½M þ
Hꢄþ 274.0715, found m=z 274.0714.
3,5-Dimethylphenyl 4-Methoxybenzoate (63). White solid;
mp 51–52 ꢁC; IR (ATR, cmꢂ1) 1717, 1248, 1138, 1077; 1H NMR
(270 MHz, CDCl3) ꢀ 8.13 (d, J ¼ 8:8 Hz, 2H), 6.97 (d, J ¼ 8:8 Hz,
2H), 6.89 (s, 1H), 6.81 (s, 2H), 3.88 (s, 3H), 2.33 (s, 6H); 13C NMR
(68 MHz, CDCl3) ꢀ 165.0, 163.6, 150.7, 139.1, 132.1, 127.4,
121.9, 119.2, 113.7, 55.5, 21.3; HRMS (ACPIþ) calcd for
C16H17O3 ½M þ Hꢄþ 257.1178, found m=z 257.1175.
This study was supported in part by the Grant of the 21st
Century COE Program, Ministry of Education, Culture, Sports,
Science and Technology (MEXT).
The authors wish to thank Mr. Sachiki Shimizu, Sankio
Chemical Co., LTD. (http://www.sankio-chem.co.jp/) for his
kind help with the mass spectrometry and IR analysis.
2-Methylphenyl 4-Methoxybenzoate (64).18 Colorless oil; IR
1
(ATR, cmꢂ1) 1722, 1260, 1163, 1067, 752; H NMR (270 MHz,
References
CDCl3) ꢀ 8.17 (d, J ¼ 8:6 Hz, 2H), 7.27–7.11 (m, 4H), 6.98 (d,
J ¼ 8:6 Hz, 2H), 3.88 (s, 3H), 2.22 (s, 3H); 13C NMR (68 MHz,
CDCl3) ꢀ 164.3, 163.6, 149.3, 132.0, 130.9, 130.1, 126.7, 125.7,
121.9, 121.5, 113.6, 55.4, 16.2; HRMS (ACPIþ) calcd for
C15H15O3 ½M þ Hꢄþ 243.1021, found m=z 243.1017.
1 T. Shintou, W. Kikuchi, and T. Mukaiyama, Bull. Chem.
Soc. Jpn., 76, 1645 (2003).
2 T. Mukaiyama, T. Shintou, and K. Fukumoto, J. Am. Chem.
Soc., 125, 10538 (2003).

T. Shintou et al.
Bull. Chem. Soc. Jpn., 77, No. 8 (2004) 1579
3
(2003).
4
T. Shintou and T. Mukaiyama, Chem. Lett., 32, 1100
11 F. M. Menger and J. H. Smith, J. Am. Chem. Soc., 94, 3824
(1972).
12 S. Takimoto, J. Inanaga, T. Katsuki, and M. Yamaguchi,
Bull. Chem. Soc. Jpn., 54, 1470 (1981).
13 a) W. R. Bowman, E. Mann, and J. Parr, J. Chem. Soc.,
Perkin Trans. 1, 2000, 2991. b) W. A. Bonner and F. D. Mango,
J. Org. Chem., 29, 430 (1964). c) A. B. Charette, M. K. Janes,
and H. Lebel, Tetrahedron: Asymmetry, 14, 867 (2003).
14 J. Yamazaki, T. Watanabe, and K. Tanaka, Tetrahedron:
Asymmetry, 12, 669 (2001).
15 M. Miyashita, I. Shiina, S. Miyoshi, and T. Mukaiyama,
Bull. Chem. Soc. Jpn., 66, 1516 (1993).
16 A. V. Doshi and N. N. Joshi, J. Indian Chem. Soc., 70, 807
(1993).
G. Bouchard, P. A. Carrupt, B. Testa, V. Gobry, and H. H.
Girault, Chem.—Eur. J., 8, 3478 (2002).
a) T. J. Broxton and V. Marcou, J. Org. Chem., 56, 1041
5
(1991). b) J. Zilberman, D. Ioffe, and I. Gozlan, Synthesis, 1992,
659. c) M. L. D. Palacious and R. F. P. Comdom, Synth. Commun.,
33, 1783 (2003). d) R. F. P. Comdom and M. L. D. Palacious,
Synth. Commun., 32, 2055 (2002). e) M. Wolter, G. Nordmann,
G. E. Job, and S. L. Buchwald, Org. Lett., 4, 973 (2002). f)
M. C. Harris, X. Huang, and S. L. Buchwald., Org. Lett., 4, 2885
(2002). g) J. P. Wolfe and S. L. Buchwald, J. Org. Chem., 62,
1264 (1997). h) J. Louie, M. S. Driver, B. C. Hamann, and J. F.
Hartwig, J. Org. Chem., 62, 1268 (1997).
6
(2000).
7
B. A. Garcia and D. Y. Gin, J. Am. Chem. Soc., 122, 4269
17 U. Ghosh, D. Ganessunker, V. J. Sattigeri, K. E. Carlson,
D. J. Mortensen, B. S. Katzenellenbogen, and J. A.
Katzenellenbogen, Bioorg. Med. Chem., 11, 629 (2003).
18 A. Hercouet and M. L. Corre, Tetrahedron, 37, 2867
(1981).
a) J. L. Gibson and L. S. Hart, J. Chem. Soc., Perkin Trans.
2, 1991, 1343. b) I. M. Dawson, L. S. Hart, and J. S. Littler,
J. Chem. Soc., Perkin Trans. 2, 1985, 1601.
8
a) S. Hashimoto and I. Furukawa, Bull. Chem. Soc. Jpn., 54,
19 R. Martin, N. Gros, V. Bohmer, and H. Kammerer,
¨ ¨
2839 (1981). b) I. Bauerova and M. Ludwig, Collect. Czech. Chem.
Commun., 65, 1777 (2000).
Monatsh. Chem., 110, 1057 (1979).
20 Y. Ding, R. Wu, and Q. Lin, Synth. Commun., 32, 2149
(2002).
9
D. Crich and J.-T. Hwang, J. Org. Chem., 63, 2765 (1998).
10 B. Iselin, W. Rittel, P. Sieber, and R. Schwyzer, Helv.
Chem. Acta, 40, 373 (1957).
21 Von W. Dilthey, W. Hoschen, and O. Dornheim, J. Prakt.
Chem., 1937, 210.
¨