Efficient Method for the Preparation of Primary, Inverted Secondary and Tertiary Alkyl Carboxylates from Alcohols and Carboxylic Acids by a New Type of Oxidation-Reduction Condensation Using Simple 1,4-Benzoquinone

Article abstract of DOI:10.1246/cl.2003.1100

A new type of oxidation-reduction condensation using in situ formed alkoxydiphenylphosphines (i.e., diphenylphosphinite esters), easily available 1,4-benzoquionone and carboxylic acids provides a new and efficient method for the preparation of alkyl carboxylates from the corresponding alcohols under mild and neutral conditions. Further, the yields of the corresponding inverted carboxylates were equally high in the case of chiral secondary or tertiary alcohols.

Full text of DOI:10.1246/cl.2003.1100

1
100
Chemistry Letters Vol.32, No.12 (2003)
Efficient Method for the Preparation of Primary, Inverted Secondary and Tertiary Alkyl
Carboxylates from Alcohols and Carboxylic Acids by a NewType of Oxidation–Reduction
Condensation Using Simple 1,4-Benzoquinone
y;yy
ꢀy;yy
and Teruaki Mukaiyama
Taichi Shintou
Center for Basic Research, The Kitasato Institute, 6-15-5 Toshima, Kita-ku, Tokyo 114-0003
Kitasato Institute for Life Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641
y
yy
(Received September 1, 2003; CL-030804)
n
A new type of oxidation–reduction condensation using in
Table 1. Esterification of benzoic acid using BuLi and benzyl
alcohol.
situ formed alkoxydiphenylphosphines (i.e., diphenylphosphin-
ite esters), easily available 1,4-benzoquionone and carboxylic
acids provides a new and efficient method for the preparation
of alkyl carboxylates from the corresponding alcohols under
mild and neutral conditions. Further, the yields of the corre-
sponding inverted carboxylates were equally high in the case
of chiral secondary or tertiary alcohols.
n-BuLi/Hexane
Ph2PCl
O
PhCOOH (1.0 equiv.)
BnOH
Ph POBn
2
Ph
OBn
THF
O
O
0oC-rt,1.0 h
CH Cl2
2
Entry Ph2POBn/equiv. Benzoquinone/equiv. Time/h Yield/%
1
2
3
4
5
6
7
8
9
1.0
1.1
1.3
1.5
1.1
1.3
1.5
1.0
1.0
1.0
1.0
1.1
1.3
1.5
3.0
3.0
3.0
3.0
1.0
1.0
1.0
98
75
75
74
60
76
84
93
1
As shown in our previous reports, oxidation–reduction con-
2
densation using in situ-generated alkoxydiphenylphosphine,
2
,6-dimethyl-1,4-benzoquinone, and carboxylic acids provided
a new and efficient method for the preparation of primary, invert-
ed secondary and tertiary alkyl carboxylates from the corre-
sponding alcohols under mild and neutral conditions.
1.7
1.7
1.0
Now, in order to establish a practical and convenient reac-
tions, a condensation using easily available 1,4-benzoquinone
instead of the above mentioned 2,6-dimethyl-1,4-benzoquinone
was studied and the desired reaction proceeded smoothly to af-
ford alkyl carboxylates in good to high yields by combined
use of alkoxydiphenylphosphines having primary, bulky secon-
dary or tertiary alkoxy groups, 1,4-benzoquinone and carboxylic
acids (Scheme 1). In the case of chiral secondary or tertiary al-
cohols, the corresponding inverted carboxylates were obtained
as well in high yields.
1.9
1.1
1.9
1.7
1.0
1.0
98
68
1
0
used, yields of the ester were not influenced by the amount of
benzyloxydiphenylphosphine (1.0–1.5 equiv.) (Table 1, Entries
–4). Next, the effect of the amounts of benzyloxydiphenylphos-
1
phine and 1,4-benzoquinone (1:1) was further screened (Table 1,
Entries 5–9). Consequently, the ester was obtained in 98% yield
when 1.7 equivalents each of in situ-formed benzyloxydiphenyl-
phosphine and 1,4-benzoquinone were treated with benzoic acid
at room temperature for 1 h (Table 1, Entry 8, and Figure 1).
Next, esterifications of various in situ-formed alkoxydiphe-
nylphosphines with various carboxylic acids were tried under the
conditions shown in Table 2. Benzylation of benzoic acids hav-
First, by treating benzoic acid with 1.0 equivalent of 1,4-
benzoquinone in dichloromethane, benzyl benzoate was ob-
tained in 75% yield within 3 h (Table 1, Entry1). When 1.0
equivalent each of benzoic acid and 1,4-benzoquinone were
1
00
O
O
O
O
95
90
Ph P
2
Ph P
2
OH
O
1
2
. n-BuLi
O
R3
R3
R1
R1
R3
. Ph PCl
2
R1
R2
R2
R2
8
8
5
0
1
2
O
OH
O
R2
RCOOH
Ph P
2
OPPh2
75
70
R1
R3
O
+
RCOO
"Inversion"
R3
R1
OH
R2
0.8
1
1.2
1.4
1.6
1.8
2
RCOO
3
Ph2POBn/benzoquinone /equiv.
Scheme 1. Esterifications between alcohols and carboxylic
acids by using of 1,4-benzoquinone.
Figure 1. Esterification of benzoic acid with n-BuLi and benzyl
alcohol.
Copyright Ó 2003 The Chemical Society of Japan

Chemistry Letters Vol.32, No.12 (2003)
1101
Table 2. Esterifications of various carboxylic acids using sveral
alcohols
as L-menthol was used (Table 2, Entries 10 and 11). In case of
chiral tertiary alcohol such as (S)-2-phenyl-2-butanol, the corre-
sponding ester was obtained in 92% yield with 99% inversion
(Table 2, Entry 15).
RCOOH (1.0 equiv.)
O (1.7 equiv.)
O
1
. n-BuLi
R'OH
Ph2POR'
R'
2.
Ph PCl
2
R
O
O
Typical experimental procedure is as follows; to a mixture
of carboxylic acid (0.30 mmol) and 1,4-benzoquinone (0.30
mmol) under argon atmosphere was added a dichloromethane
(
1.7 equiv.)
CH Cl2
2
3
Yield /% a
(0.3 mL) solution of alkoxydiphenylphosphine (0.51 mmol) at
Entry
R'OH
RCOOH
PhCOOH
p-MeO-C H COOH 1.0
Time /h Yield /%
room temperature. After the reaction that was monitored by
TLC was completed, the reaction mixture was quenched by add-
ing water and the aqueous layer was extracted with dichlorome-
thane. The organic layers were dried over anhydrous sodium sul-
fate. After filtration and evaporation, the resulted residue was
purified by preparative TLC to afford the corresponding ester.
The above reactions were also carried out by one-pot procedure
and the same results were obtained even in the presence of lithi-
um chloride.
Thus, a new type of oxidation–reduction condensation using
in situ formed alkoxydiphenylphosphines (i.e., diphenylphos-
phinite esters), carboxylic acids, and 1.7 equivalents of 1,4-ben-
zoquinone provided successfully a new and efficient method for
the preparation of alkyl carboxylates from the corresponding al-
cohols under mild and neutral conditions. Further, the yields of
the corresponding inverted carboxylates were equally high in the
case of chiral secondary or tertiary alcohols.
1
2
3
4
5
6
BnOH
1.0
98
95
96
92
98
90
98
95
95
93
92
93
6
4
p-NO -C H COOH 1.0
2
6 4
PhCH CH COOH 1.0
2
2
PhCH=CHCOOH
1.0
1.0
CH (CH ) COOH
3
2 3
p-MeO-
C H CH OH
7
8
PhCOOH
1.0
1.0
93
90
91
88
6
4
2
CH (CH ) OH
PhCOOH
PhCOOH
3
2 3
Ph
9
3.0
3.0
90
94
Ph OH
1
0b
1b
PhCOOH
91
86
(
(
>99.9%) (>99.9%)
96
95
1
p-NO2-C6H4COOH 3.0
OH
>99.9%) (>99.9%)
1
2
3
OH
PhCOOH
O
15.0
15.0
75
95
69
96
This study was supported in part by the Grant of the 21st
Century COE Program, Ministry of Education, Culture, Sports,
Science and Technology (MEXT).
1
OH
Ph
HO
Ph Ph
Ph
References and Notes
1
1
4
15.0
15.0
95
96
OH
a) T. Mukaiyama, T. Shintou, and W. Kikuchi, Chem. Lett.,
002, 1126. b) T. Shintou, W. Kikuchi, and T. Mukaiyama,
COOH
2
Et OH
5b
PhCOOH
95
(>99%)
96
(>99%)
1
Chem. Lett., 32, 22 (2003). c) T. Mukaiyama, W. Kikuchi,
and T. Shintou, Chem. Lett., 32, 300 (2003). d) T. Shintou,
W. Kikuchi, and T. Mukaiyama, Bull. Chem. Soc. Jpn., 76,
1645 (2003). e) T. Mukaiyama, T. Shintou, and K.
Fukumoto, J. Am. Chem. Soc., 125, 10538(2003).
Ph
Me
a
Esterifications of various carboxylic acids with various alcohols
using 2,6-dimethyl-1,4-benzoquinone. [Alcohols (1.1–1.2 equiv.),
carboxylic acids (1.0 equiv.), 2,6-dimethyl-1,4-benzoquinone (1.0
equiv.)]
2
Other oxidation-reduction condensation. For examples: a) T.
Mukaiyama, I. Kuwajima, and Z. Suzuki, J. Org. Chem., 28,
b
Yields in the parenthesis are inversion.
2
024 (1963). b) I. Kuwajima and T. Mukaiyama, J. Org.
ing electron-donating or electron-withdrawing groups and satu-
rated or unsaturated aliphatic carboxylic acids proceeded
smoothly to afford the corresponding carboxylic acid benzyl es-
ters in high to excellent yields under mild conditions (Table 2,
Entries 1–6). When primary alcohols such as n-buthanol or p-
methoxybenzyl alcohol having electron-donating or secondary
alcohols such as benzhydrol were used, the corresponding esters
were obtained in high yields on treatment with benzoic acid for
Chem., 29, 1385 (1964). c) T. Mukaiyama, R. Matsueda,
and M. Suzuki, Tetrahedron Lett., 22, 1901 (1970). d) O.
Mitsunobu, M. Yamada, and T. Mukaiyama, Bull. Chem.
Soc. Jpn., 40, 935 (1967). e) O. Mitsunobu and M. Yamada,
Bull. Chem. Soc. Jpn., 40, 2380 (1967). f) O. Mitsunobu and
M. Eguchi, Bull. Chem. Soc. Jpn., 44, 3427 (1971). g) O.
Mitsunobu, Synthesis, 1981, 1. h) T. Tsunoda, Y. Yamamiya,
and S. Ito, Tetrahedron Lett., 34, 1639 (1993). i) Y.-J. Shi, D.
L. Hughes, and J. M. McNamara, Tetrahedron Lett., 44,
3609 (2003).
1–3 h (Table 2, Entries 7–9). Similarly, the reaction of tert-buta-
nol and benzoic acid afforded the desired ester in 75% yield un-
der the same conditions (Table 2, Entry 12). The condensations
of tertiary alcohol and carboxylic acid such as 1-adamanthanol
and 2-phenylbutyric acid or 1-methylcyclopentanol and triphe-
nylacetic acid also proceeded smoothly to afford the correspond-
ing alkyl carboxylates in excellent yields (Table 2, Entries 13
and 14). In addition, it was noted that the corresponding alkyl
carboxylates were obtained in excellent yields with perfect in-
version of stereochemistry when chiral secondary alcohol such
3
Preparation of various alkoxydiphenylphosphines. See
Ref. 1; into a stirred solution of alcohol (1.5 mmol) in THF
(5 mL) was dropped a hexane solution of n-BuLi (1.5 mmol)
ꢁ
at 0 C under argon atmosphere. After the solution was stir-
red at room temperature for 1.0 h, a THF (2 mL) solution of
ꢁ
chlorodiphenylphosphine (1.5 mmol) was added at 0 C. The
reaction mixture was stirred for 1.0 h at room temperature
and the solvent was concentrated in vacuo.
Published on the web (Advance View) November 3, 2003; DOI 10.1246/cl.2003.1100