Effective esterification of carboxylic acids using (6-oxo-6H-pyridazin-1-yl)phosphoric acid diethyl ester as novel coupling agents

Article abstract of DOI:10.1016/j.tet.2007.10.011

(6-Oxo-6H-pyridazin-1-yl)phosphoric acid diethyl esters (3) are efficient and selective coupling agents for equimolar esterification of carboxylic acids and alcohols. Esterification of aliphatic and aromatic carboxylic acids with aliphatic and aromatic alcohols using 3 afforded the corresponding esters chemoselectively in good to excellent yield.

Full text of DOI:10.1016/j.tet.2007.10.011

Tetrahedron 63 (2007) 12720–12730
Effective esterification of carboxylic acids using
(6-oxo-6H-pyridazin-1-yl)phosphoric acid diethyl
ester as novel coupling agents
Ju-Eun Won,a Ho-Kyun Kim,a Jeum-Jong Kim,a Heong-Seup Yim,a Min-Jung Kim,a
a,
Seung-Beom Kang,a Hyun-A Chung,a Sang-Gyeong Leeb, and Yong-Jin Yoon
*
*
aDepartment of Chemistry and Environmental Biotechnology National Core Research center, Research Institute
of Natural Science, Graduate School for Molecular Materials and Nanochemistry, Gyeongsang National University,
900 Gazwa-dong, Jinju, Gyeongnam 660-701, Republic of Korea
bDepartment of Chemistry, Research Institute of Natural Science, Graduate School for Molecular Materials and Nanochemistry,
Gyeongsang National University, 900 Gazwa-dong, Jinju, Gyeongnam 660-701, Republic of Korea
Received 24 July 2007; revised 1 October 2007; accepted 1 October 2007
Available online 6 October 2007
Abstract—(6-Oxo-6H-pyridazin-1-yl)phosphoric acid diethyl esters (3) are efficient and selective coupling agents for equimolar esterifica-
tion of carboxylic acids and alcohols. Esterification of aliphatic and aromatic carboxylic acids with aliphatic and aromatic alcohols using 3
afforded the corresponding esters chemoselectively in good to excellent yield.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
for high-yielding esterifications with equimolar reactions of
carboxylic acids and alcohols. Pyridazin-3(2H)-one is a
stable and good leaving group, and shows an electron
withdrawing ability.3,5,7–9 Also various organophosphorus
compounds have been developed as carboxylic acid activa-
tors.10 Therefore, we designed and synthesized some
(6-oxo-6H-pyridazin-1-yl)phosphoric acid diethyl esters as
carboxylic acid activator. In this paper, we report on effec-
tive and convenient esterification of carboxylic acids with al-
cohols by using (6-oxo-6H-pyridazin-1-yl)phosphoric acid
diethyl esters in one port.
Effective esterification of carboxylic acids with alcohols is
the most fundamental reaction in organic synthesis.1 It has
long been known that the process of esterification is enor-
mously accelerated by the addition of strong acid such as
sulfuric acid. There are also many methods of esterification
that use specific dehydrating reagents.2 However, the classi-
cal esterifications have some disadvantages of the corrosive-
ness of strong acid, with accompanying side reactions such
as carbonization and oxidation. Although many reagents
for esterification of carboxylic acid have been developed,2–5
the research in this field is still very active even now.6 For di-
rect esterification of carboxylic acid in the absence of strong
acid, carboxylic acid must be activated to more reactive
species by using an activator.
2. Results and discussion
Some 4,5-disubstituted-pyridazin-3(2H)-ones were readily
prepared by the reported methods.11 From preliminary ex-
periments (Table 1, entries 1–5),12 we selected triethylamine
and acetonitrile as a suitable base/solvent system for the syn-
thesis of 3.
In our previous paper,3,5 we have reported on the synthesis of
anhydrides and esters using 4,5-dichloro-2-[(4-nitrobenzen-
sulfonyl)]pyridazin-3(2H)-one as an activator. Because this
esterification proceeds via the corresponding anhydrides as
the intermediate,5 2 equiv of carboxylic acids are required
in this reaction. Therefore, we attempted to develop more ef-
fective coupling agents that contain pyridazinone derivatives
The reaction of 4,5-disubstituted-pyridazin-3(2H)-ones (1)
with diethyl chlorophosphate (2) in the presence of triethyl-
amine in acetonitrile at room temperature afforded the corre-
sponding 3a–3e in excellent yields (Table 1, entries 1 and
6–9) (Scheme 1).
Keywords: (6-Oxo-6H-pyridazin-1-yl)phosphoric acid diethyl ester;
Coupling agent; Carboxylic acid; Pyridazinone; Esterification.
* Corresponding authors. Tel.: +82 055 751 6019; fax: +82 055 761 0244;
e-mail: yjyoon@gnu.ac.kr
Initially, direct esterification of 4-nitrobenzoic acid (4a) with
methanol (5a) using 3a was studied in a variety of
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.10.011

J.-E. Won et al. / Tetrahedron 63 (2007) 12720–12730
12721
Table 1. Synthesis of diethyl 6-oxo-6H-pyridazin-1-ylphosphonate 3a
Table 2. Esterification of compound 4a with methanol (5a) using 3 at reflux
temperature
Y
Y
O
X
O
C OH
O
P
OEt
3
X
Base
O2N
C OMe
O2N
+
MeOH
+
EtO
Cl
Base/solvent
N
O
CH3CN
N
O
EtO
N
P
4a
O
N
H
6a
5a
OEt
Entry
3
Base
Solvent
THF
EtOAc
H2O
THF
EtOAc
H2O
THF
EtOAc
H2O
THF
EtOAc
H2O
EtOAc
EtOAc
EtOAc
EtOAc
Time (h)
6a Yielda (%)
1
2
3
1
2
3
4
5
6
7
8
3a
3a
3a
3a
3a
3a
3a
3a
3a
3a
3a
3a
3b
3c
3d
3e
Et3N
Et3N
Et3N
0.5
0.5
20
0.3
0.5
6
2
2
42
43
20
50
1
95
97
9d
Entry
1
Base
Time (h)
Yieldb (%)
K2CO3
K2CO3
K2CO3
DMAPb
DMAPb
DMAPb
Resinc
98
99
17d
98
95
11d
17
66
11d
97
98
96
89
X
Y
1
2
3
4
5
6
7
8
9
a
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Br
Cl
Cl
Cl
Cl
Cl
OMe
N3
OPh
Br
Et3N
1
28
26
10
18
6
4
8
19
3a (96)
3a (65)
3a (58)
3a (89)
3a (78)
3b (89)
3c (86)
3d (88)
3e (79)
a
a
a
a
b
c
DMAPc
NaH
K2CO3
Cs2CO3
Et3N
Et3N
Et3N
9
10
11
12
13
14
15
16
Resinc
Resinc
d
e
K2CO3
K2CO3
K2CO3
K2CO3
Et3N
0.5
0.8
0.5
a
Reaction was carried out at room temperature.
Isolated yield.
DMAP¼N,N-dimethylaminopyridine.
b
c
a
Isolated yield. 4,5-Dichloropyridazin-3(2H)-one was isolated quantita-
tively.
b
c
d
DMAP¼N,N-dimethylaminopyridine.
representative organic solvents and bases (Table 2, entries 1–
10). Exclusive esterification in excellent yields was obtained
in triethylamine/THF (or toluene, acetone, acetonitrile, di-
ethyl ether, and ethyl acetate),13 potassium carbonate/ethyl
acetate (or THF), and N,N-dimethylaminopyridine/THF
(or ethyl acetate). Among these systems, we selected the po-
tassium carbonate/ethyl acetate system for direct esterifica-
tion of carboxylic acid using 3a. The efficacy of 3b–3e for
esterification was evaluated using the reaction of 4-nitroben-
zoic acid (4a) with methanol (5a) in the presence of
Resin is Amberite-IRA66.
Compound 3 was decomposed.
potassium carbonate in ethyl acetate at reflux temperature
(Table 2, entries 13–16).
Compounds 3a–3d showed similar efficacy for esterification
under this condition. Therefore, we selected compound 3a as
a novel coupling agent for the esterification of carboxylic
acid because 1b–1d were prepared by the conversion of
O
Y
X
Cl P OEt
Y
OEt
2
X
a
b
c
d
e
N
O
x
Cl Cl
Cl Cl
Br
O
EtO
N
P
Et3N/CH3CN
N
O
N
H
Cl OMe
OPh Br
N3
Y
OEt
1
3
3
O
O
Base/Solvent
-Pyridazinone
C
C
+
R'OH
R
OH
R
OR'
4
5
6
COOH
COOH
Me
COOH
COOH
COOH
COOH
COOH
(CH2)6
CH3
O
COOH
OH
RCOOH =
R'OH =
Ph
Ph
NO2
4a
4b
4c
4d
4e
4f
4g
4h
OH
MeOH
5a
i-PrOH
5b
t-BuOH
n-C6H13OH
5c
5d
5e
5f
OH
OH
OH
OH
Cl
SH
OH
HS
O2N
H2N
N
5g
5j
5h
5i
5k
5l
Scheme 1.

12722
J.-E. Won et al. / Tetrahedron 63 (2007) 12720–12730
1a. Esterification of 4-nitrobenzoic acid (4a) with various ali-
phatic and aromatic alcohols 5b–5i using 3a in the presence
of potassium carbonate in refluxing ethyl acetate afforded
the corresponding esters 6b–6i except for 6e in good to
excellent yields (Table 3, entries 1–8).
of 1ꢀ/2ꢀ alcohols or 1ꢀ/3ꢀ alcohols afforded primary alkyl es-
ter 6t selectively (Table 5, entries 1 and 3). But we found the
corresponding anhydrides as the main products in the com-
petition reaction of 2ꢀ/3ꢀ alcohols with octanoic acid (4d)
and benzoic acid (4h) (Table 5, entries 5 and 6). This selec-
tivity may be due to the steric hindrance of the carbonyl car-
bon of acyl phosphate and alcohols (2ꢀ or 3ꢀ). In the reaction
of carboxylic acids with 2ꢀ or 3ꢀ alcohol under our reaction
condition, the formation of anhydride may be more favor-
able than esterification. Esterification of octanoic acid (4d)
with a mixture of cyclohexanol (5d)/phenol (5f) afforded
phenyl ester 6u selectively in good yield (Table 5, entry
7). We investigated the chemoselectivity in the esterification
of a mixture of phenol (5f)/benzenethiol (5j) and bifunc-
tional alcohols such as 2-mercaptoethanol (5k) and 4-amino-
phenol (5l). The esterification of a mixture of phenol (5f)/
benzenethiol (5j) with octanoic acid (4d) afforded the cor-
responding ester 6u chemoselectively as the main product
instead of the thioester. Also diphenyldisulfide was obtained
as the side product (Table 5, entry 11). The reaction of
2-mercaptoethanol (5k) with octanoic acid (4d) under the
same condition also afforded the thioester 6ak selectively
in 86% yield (Table 5, entry 13). However, the reaction of
4-aminophenol (5l) with octanoic acid (4d) under the same
condition yielded the corresponding amide 6am chemo-
selectively in 99% yield (Table 5, entry 15).
The reaction of 4-nitrobenzoic acid (4a) with benzenethiol
(5j) under the same condition also afforded the correspond-
ing thioester 6j in excellent yields, whereas reaction of 4-ni-
trobenzoic acid (4a) with tert-butyl alcohol (5e) under the
same condition obtained 4-nitrobenzoic anhydride instead
of the corresponding ester 6e in 21% yield (Table 3, entry
4). This result may be attributed to the steric hindrance of
tert-butanol. Treatment of aliphatic or aromatic carboxylic
acids 4b–4g with various alcohols 5a, 5c, 5f, and 5i in the
presence of potassium carbonate in refluxing ethyl acetate
easily afforded the corresponding ester 6k–6ag in good to
excellent yields (Table 4).
Selective esterification of primary alcohol in mixed alcohol
such as 1ꢀ/2ꢀ alcohol and 1ꢀ/3ꢀ alcohol is also often required.
Therefore we examined the selective esterification of a mix-
ture of two alcohols such as 1ꢀ/2ꢀ alcohols, 1ꢀ/3ꢀ alcohols,
2ꢀ/3ꢀ alcohols, aromatic/aliphatic alcohols, or bifunctional
alcohols such as 2-mercaptoethanol (5k) and 4-aminophenol
(5l). The esterification of octanoic acid (4d) with a mixture
Table 3. Esterification of compound 4a with alcohols 5 using 3a at reflux temperature
O
C
O
C OH
3a
O2N
XR'
O2N
+
R'XH
K2CO3/EtOAc
X = O or S
4a
6
5
Entry
1
5
Time (h)
1.5
Product 6
Yielda (%)
O
C
5b
5c
5d
5e
5f
i-PrOH
6b (86)
O2N
O(i-Pr)
O
2
3
4
5
6
7
8
CH3(CH2)5OH
2
6c (80)
6d (77)
6e (—)b
6f (98)
6g (99)
6h (99)
O2N
C
O(CH2)5CH3
O
5.5
3
OH
OH
O2N
C O
O
O2N
C O
O
2
OH
O2N
C O
O
5g
5h
0.5
0.5
O2N
OH
O2N
C O
NO2
Cl
Cl
O
OH
OH
O2N
O2N
O2N
C O
O
5i
5j
0.5
1
6i (97)
6j (98)
C O
N
N
O
9
SH
C
S
a
Isolated yield. 4,5-Dichloropyridazin-3(2H)-one was isolated quantitatively.
4-Nitrobenzoic anhydride instead of 6e was obtained in 21% yield.
b

J.-E. Won et al. / Tetrahedron 63 (2007) 12720–12730
12723
Table 4. Esterification of some carboxylic acids 4b–4g with 5a, 5c, 5f, and 5i using 3a in the presence of potassium carbonate in refluxing ethyl acetate
3a
RCOOR'
6k-6ag
RCOOH
4b-4g
+
R'OH
5
K2CO3 / EtOAc
Time (h)
Entry
1
4
5
Product 6
Yielda (%)
O
4b
4b
4b
4b
4c
4c
4c
5a
MeOH
2
6k (95)
Me
Me
Me
Me
COOH
COOH
COOH
COOH
Me
C OMe
O
2
3
4
5
6
7
5c
5f
5i
CH3(CH2)5OH
9
6l (71)
6m (86)
6n (89)
6o (81)
6p (83)
6q (80)
Me
C O(CH2)5CH3
O
C O
3.5
4
OH
Me
O
OH
N
Me
C O
N
O
5a
5c
5f
MeOH
CH3(CH2)5OH
OH
1
COOH
C OMe
O
4
COOH
COOH
C O(CH2)5CH3
O
C O
0.5
O
OH
N
8
4c
4d
4d
4d
4d
5i
0.5
1.3
5
6r (96)
6s (91)
6t (76)
6u (95)
6v (94)
C O
N
COOH
COOH
COOMe
9
5a
5c
5f
5i
MeOH
CH3(CH2)5OH
OH
3
3
COO(CH2)5CH3
COOH
10
11
12
3
3
COOH
COOPh
3
3
3
O
COOH
3
OH
N
1.5
CO
3
N
COOH
Ph
COOMe
Ph
Ph
13
14
15
16
17
18
4e
4e
4e
4e
4f
4f
5a
5c
5f
5i
MeOH
CH3(CH2)5OH
OH
0.5
0.5
2
6w (92)
6x (93)
6y (87)
6z (95)
Ph
COOH
Ph
COO(CH2)5CH3
Ph
Ph
Ph
Ph
Ph
O
COOH
Ph
CO
Ph
Ph
O
COOH
Ph
CO
Ph
OH
N
0.5
9
N
Ph
O
C
O
C
5c
5f
CH3(CH2)5OH
6aa (70)
6ab (86)
OH
O(CH2)5CH3
O
C
O
1
OH
C
OH
OH
O
O
O
C
O
C
OH
N
19
20
4f
5i
0.5
1.5
6ac (97)
6ad (92)
N
O
C
O
O
COOH
O
4g
5a
MeOH
OMe
O
COOH
O
21
4g
5c
CH3(CH2)5OH
1
6ae (77)
C
O(CH2)5CH3
(continued)

12724
J.-E. Won et al. / Tetrahedron 63 (2007) 12720–12730
Table 4. (continued)
Entry
4
5
Time (h)
3
Product 6
Yielda (%)
O
O
COOH
COOH
O
O
22
4g
4g
5f
5i
6af (95)
OH
OH
C
O
O
O
23
2.5
6ag (95)
C
N
O
N
a
Isolated yield. 4,5-Dichloropyridazin-3(2H)-one was isolated quantitatively.
Table 5. Competition reaction of octanoic acid (4d) or benzoic acid (4h) with mixed alcohols at room temperature
3a
RCOXR'(or R")
6
RCOOH
4
+ R'XH/R"XH
5
K2CO3 / EtOAc
Entry
1
4
R0XH/R00XH (5)
Time (h)
Product 6
COO(CH2)5CH3
Yielda (%)
COOH
4d
4h
4d
4h
4d
4h
4d
4h
4d
4h
4d
4h
4d
4h
4d
1
6t (87)
3
3
CH3(CH2)5OH (5c)/i-PrOH(5b)
O
2
5b
0.3
6ah (90)
6t (82)
COOH
COOH
C O(CH2)5CH3
COO(CH2)5CH3
3
3
3
CH3(CH2)5OH (5c)/t-BuOH(5e)
i-PrOH(5b)/t-BuOH(5e)
O
4
11
6ah (22)c
COOH
COOH
C O(CH2)5CH3
d
—
5
3.5
3.5
2
—
—
3
c
—
6
COOH
COOH
COOPh
7
6u (80)
6ai (86)
6u (88)
3
3
c-C6H11OH(5d)/C6H5OH(5f)
CH3(CH2)5OH(5c)/C6H5OH(5f)
C6H5OH (5f)/C6H5SH (5j)
HSCH2CH2OH (5k)
O
C O
8
2
COOH
COOH
COOPh
9
0.5
4
3
3
O
C O
10
11
12
13
14
15
6ai (82)
6u (71)e
6aj (50)e
6ak (86)
6al (93)
6am (99)
COOH
COOH
COOPh
6
3
3
O
3.5
1.5
4
COOH
COOH
C
S
O
CS(CH2)2OH
3
3
O
COOH
COOH
CS(CH2)2OH
O
1.5
CNH
OH
3
3
(5l)
OH
H2N
O
16
4h
2.5f
6an (92)
COOH
CNH
OH
a
Isolated yield. 4,5-Dichloropyridazin-3(2H)-one was isolated quantitatively.
Reaction temperature¼at reflux temperature.
Benzoic anhydride was obtained in 54% yield.
Octanoic anhydride was obtained in 75% yield.
Diphenyldisulfide was also obtained.
b
c
d
e
f
The solvent was THF.

J.-E. Won et al. / Tetrahedron 63 (2007) 12720–12730
12725
The reaction of benzoic acid (4h) with a mixture of 1ꢀ/2ꢀ
3. Conclusion
alcohols afforded primary alkyl ester 6ah in excellent selec-
tivity and in high yield (Table 5, entry 2). The esterification
of benzoic acid (4h) with a mixture of 1ꢀ/3ꢀ alcohols af-
forded primary alkyl ester 6ah (22%) and benzoic anhy-
dride (54%) (Table 5, entry 4). The reaction of a mixture
of 2ꢀ/3ꢀ alcohols with benzoic acid (4h) isolated only ben-
zoic anhydride instead of the corresponding ester (Table 5,
entry 6). Aromatic alcohols were selectively esterified with
benzoic acid (4h) in the competition reaction of aliphatic/ar-
omatic alcohol under our condition (Table 5, entries 8 and
10). The esterification of a mixture of phenol (5f)/benzene-
thiol (5i) with benzoic acid (4h) using 3a afforded the corre-
sponding thioester 6aj (50%) chemoselectively and
diphenyldisulfide (Table 5, entry 12). The reaction of 2-
mercaptoethanol (5k) with benzoic acid (4h) using 3a under
same condition also afforded selectively thioester 6al in 93%
yield (Table 5, entry 14). The structure of 6al was established
by IR, NMR, and elemental analysis. However, the reaction
of 4-aminophenol (5l) with benzoic acid (4h) using 3a under
the same condition yielded the corresponding amide 6an
chemoselectively in 92% yield (Table 5, entry 16).
Compound 3a is an efficient coupling agent for equimolar
esterification of carboxylic acids with alcohols under the ba-
sic condition. It also has some advantages: (i) the reaction
condition is basic, (ii) this method shows excellent selecti-
vity for primary or secondary alcohols, (iii) the coupling
agent is easily prepared from commercially available com-
pound 1, and (iv) compound 1 can be recovered quantita-
tively for reuse. We also believe that these coupling agents
would be applicable particularly to solid-phase syntheses
and amidation of carboxylic acid.
4. Experimental
4.1. General
Column chromatography was carried out on silica gel 60
(70–230 mesh). Melting points were determined with
a Thomas–Hoover capillary apparatus and are uncorrected.
1H and 13C NMR spectra were recorded on a 300 MHz
spectrophotometer with chemical shift values reported in
d units (part per million) relative to an internal standard
(tetramethylsilane). IR spectra were obtained on a Hitachi
270-50 or Mattson Genesis Series FT-IR spectrophotome-
ter. Elemental analyses were performed with CHNS-932
(Leco).
In the esterification of octanoic acid (4d) or benzoic acid
(4h), the different selectivity of cyclohexanol (5d) and
phenol (5f) may be attributed to the steric hindrance and/or
the difference of pKa for two alcohols. Also, the different
chemoselectivity for esterification of octanoic acid (4d) or
benzoic acid (4h) with phenol (5f) or benzenethiol (5j)
may be due to the different nucleophilicity of two nucleo-
philes (5f and 5j) and/or the different electrophilicity of the
carbonyl carbons for aliphatic and aromatic carboxylic acids.
4.2. 4,5-Disubsituted-6-oxo-6H-pyridazin-1-ylphos-
phonates (3a–3e)
A solution of diethyl chlorophosphate (10.4 mmol) in sol-
vent such as CH2Cl2, THF, CH3CN, acetone, or toluene
was added slowly to a solution of 4,5-disubsituted-pyrid-
azin-3(2H)-ones10 (9.4 mmol) in solvent such as CH2Cl2,
THF, CH3CN, acetone, or toluene in the presence of a base
(10.4 mmol) at the appropriate temperature with stirring.
The mixture was stirred at room temperature until compound
1 disappeared. After filtering the mixture, water (150 mL)
was added to the filtrate. The product was extracted with
methylene chloride (150 mL). The methylene chloride solu-
tion was dried over anhydrous magnesium sulfate. The
resulting solution was evaporated under reduced pressure
to give compound 3 as liquid.
In all the reactions described above, reusable 4,5-dichloro-
pyridazin-3(2H)-one (1a) was also isolated quantitatively.
On the other hand, acid anhydride was not detected during
these reactions when monitored with TLC except for the
use of 2ꢀ and 3ꢀ alcohols. Actually, only 1 equiv of carboxy-
lic acid was required for the esterification under these reac-
tion conditions. This esterification mechanism is different
from that of the esterification of carboxylic acid with alcohol
by using 4,5-dichloro-2-[(4-nitrobenzenesulfonyl)]pyrida-
zin-3(2H)-one.6 The esterification of carboxylic acid using
compound 3 may be proceeded via two steps, the formation
of acyl phosphate in the first step and then alcohol reacts
with acyl phosphate to give the ester in the second step.
Therefore, diethyl 6-oxo-6H-pyridazin-1-ylphosphonate is
a more effective coupling agent than 4,5-dichloro-2-[(4-ni-
trobenzenesulfonyl)]pyridazin-3(2H)-one6 for equimolar
esterification of carboxylic acids and alcohols. The struc-
tures of all the products were established by IR, NMR, and
elemental analyses (Scheme 2).
4.2.1. Diethyl-4,5-dichloro-6-oxo-(6H)-pyridazin-1-yl-
phosphonate (3a). Liquid. Rf¼0.33 (EtOAc/n-hexane¼1:1,
v/v). IR (KBr) 3020, 2970, 1700, 1610, 1560, 1460, 1430,
1400, 1380, 1310, 1180, 1150, 1120, 1050, 980, 940 cmꢁ1
.
1H NMR (CDCl3) d: 9.04 (s, 1H), 4.52–4.42 (m, 4H),
1.48–1.43 (m, 6H). 13C NMR (CDCl3) d: 157.6, 149.6,
138.3, 127.2, 65.9, 16.0. Elemental analysis calcd for
C8H11Cl2N2O4P: C, 31.92; H, 3.68; N, 9.30. Found: C,
31.93; H, 3.74; N, 9.33.
O
C
O
C
O
P
OEt
O
C
3a / Base
- Pyridazinone
R'OH / Base
-HOP(=O)(OEt)2
R'
OEt
R
OH
R
O
R
O
4.2.2. Diethyl-5-chloro-4-methoxy-6-oxo-(6H)-pyrid-
azin-1-ylphosphonate (3b). Liquid. Rf¼0.33 (EtOAc/
n-hexane¼1:2, v/v). IR (KBr) 3010, 2960, 2940, 1695,
1620, 1580, 1480, 1460, 1400, 1360, 1290, 1170, 1120,
Ester
RCOO-
O
C
O
C
R
O
R
1
1040, 980 cmꢁ1. H NMR (CDCl3) d: 8.91 (s, 1H), 4.50–
Anhydride
4.40 (m, 4H), 4.15 (s, 3H), 1.44 (t, 6H, J¼7.1 Hz). 13C
NMR (CDCl3) d: 157.8, 156.9, 137.3, 113.8, 65.5, 57.7,
Scheme 2.

12726
J.-E. Won et al. / Tetrahedron 63 (2007) 12720–12730
16.0. Elemental analysis calcd for C9H14ClN2O5P: C, 36.44;
H, 4.76; N, 9.44. Found: C, 36.46; H, 4.77; N, 9.52.
d: 8.28 (d, 2H, J¼8.9 Hz), 8.20 (d, 2H, J¼8.8 Hz), 5.29
(m, 1H), 1.41 (d, 6H, J¼6.3 Hz). 13C NMR (CDCl3) d:
164.2, 150.4, 136.3, 130.6, 123.4, 69.7, 21.9. Elemental
analysis calcd for C10H11NO4: C, 57.41; H, 5.30; N, 6.70.
Found: C, 57.49; H, 5.31; N, 6.72.
4.2.3. Diethyl-4-azido 5-chloro-6-oxo-(6H)-pyridazin-1-
ylphosphonate (3c). Liquid. Rf¼0.30 (EtOAc/n-hexane¼
1:1, v/v). IR (KBr) 3010, 2960, 2260, 1690, 1580, 1460,
1380, 1360, 1300, 1250, 1210, 1180, 1080, 1050, 1020,
4.3.3. Hexyl 4-nitrobenzoate (6c). Liquid. Rf¼0.71
(EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3140, 2950, 2890,
1730, 1610, 1540, 1470, 1360, 1320, 1280, 1110, 1020,
1
860 cmꢁ1. H NMR (CDCl3) d: 8.90 (s, 1H), 4.96–4.40
(m, 4H), 1.46–1.41 (m, 6H). 13C NMR (CDCl3) d: 157.7,
141.9, 141.1, 116.8, 65.8, 16.0. Elemental analysis calcd
for C8H11ClN5O4P: C, 31.23; H, 3.60; N, 22.77. Found: C,
31.34; H, 3.69; N, 22.78.
880, 720 cmꢁ1
.
1H NMR (CDCl3) d: 8.29 (d, 2H,
J¼9.0 Hz), 8.21 (d, 2H, J¼9.0 Hz), 4.38 (t, 2H,
J¼6.7 Hz), 1.85–1.75 (m, 2H), 1.51–1.26 (m, 6H), 0.91 (t,
3H, J¼7.0 Hz). 13C NMR (CDCl3) d: 165.7, 151.4, 136.9,
131.6, 124.5, 67.1, 32.3, 29.5, 26.6, 23.5, 14.9. Elemental
analysis calcd for C13H17NO4: C, 62.14; H, 6.82; N, 5.57.
Found: C, 62.20; H, 6.89; N, 5.59.
4.2.4. Diethyl-5-chloro-4-phenoxy-6-oxo-(6H)-pyridazin-
1-ylphosphonate (3d). Liquid. Rf¼0.40 (EtOAc/n-hexane¼
1:1, v/v). IR (KBr) 3010, 1690, 1580, 1500, 1380, 1320,
1300, 1230, 1210, 1050, 980, 900, 820, 780 cmꢁ1. 1H NMR
(CDCl3) d: 8.51 (s, 1H), 7.52–7.13 (m, 5H), 4.53–4.44 (m,
4H), 1.48–1.43 (m, 6H). 13C NMR (CDCl3) d: 158.3, 155.3,
153.2, 140.3, 130.7, 126.6, 120.1, 115.5, 65.7, 16.1. Elemen-
tal analysis calcd for C14H16ClN2O5P: C, 46.88; H, 4.50; N,
7.81. Found: C, 46.91; H, 4.52; N, 7.84.
4.3.4. Cyclohexyl 4-nitrobenzoate (6d). Liquid. Rf¼0.73
(EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3150, 2970, 2900,
1730, 1610, 1530, 1460, 1410, 1360, 1340, 1290, 1180,
1
1110, 1020, 960, 890 cmꢁ1. H NMR (CDCl3) d: 8.28 (d,
2H, J¼9.0 Hz), 8.21 (d, 2H, J¼9.0 Hz), 5.11–5.03 (m, 1H),
2.00–1.95 (m, 2H), 1.83–1.75 (m, 2H), 1.68–1.57 (m, 3H),
1.53–1.33 (m, 3H). 13C NMR (CDCl3) d: 164.0, 150.4,
136.4, 130.6, 123.4, 74.4, 31.5, 25.3, 23.6. Elemental analysis
calcd for C13H15NO4: C, 62.64; H, 6.07; N, 5.62. Found: C,
62.67; H, 6.10; N, 5.67.
4.2.5. Diethyl-4,5-dibromo-6-oxo-(6H)-pyridazin-1-yl-
phosphonate (3e). Liquid. Rf¼0.30 (EtOAc/n-hexane¼1:1,
v/v). IR (KBr) 3030, 2980, 2950, 1700, 1600, 1540, 1430,
1
1420, 1380, 1300, 1180, 1100, 1050, 970 cmꢁ1. H NMR
(CDCl3) d: 9.04 (s, 1H), 4.52–4.42 (m, 4H), 1.47–1.42 (m,
6H). 13C NMR (CDCl3) d: 158.5, 151.5, 132.4, 121.4,
65.9, 16.1. Elemental analysis calcd for C8H11Br2N2O4P:
C, 24.64; H, 2.84; N, 7.18. Found: C, 24.66; H, 2.95; N, 7.21.
4.3.5. Phenyl 4-nitrobenzoate (6f). Mp 127–129 ꢀC.
Rf¼0.75 (EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3130, 1750,
1610, 1530, 1490, 1360, 1320, 1280, 1190, 1080, 1020,
1
870, 850, 760, 720 cmꢁ1. H NMR (CDCl3) d: 8.40–8.33
4.3. Esterification of carboxylic acid derivatives with
alcohol derivatives
(m, 4H), 7.46 (t, 2H, J¼8.1 Hz), 7.31 (t, 1H, J¼7.4 Hz),
7.23 (d, 2H, J¼7.5 Hz). 13C NMR (CDCl3) d: 163.3, 150.9,
150.5, 135.0, 131.3, 129.7, 126.4, 123.7, 121.4. Elemental
analysis calcd for C13H9NO4: C, 64.20; H, 3.73; N, 5.76.
Found: C, 64.23; H, 3.75; N, 5.78.
A solution of carboxylic acid (4.1 mmol, 1 equiv), alcohol
(4.5 mmol, 1.1 equiv), base (4.5 mmol, 1.1 equiv), coupling
agent 3 (6.1 mmol, 1.5 equiv), and solvent (30 mL) was
stirred at reflux temperature or at room temperature until
carboxylic acid disappeared by TLC monitoring. After cool-
ing to room temperature, the mixture was filtered. The sol-
vent was evaporated under reduced pressure. The resulting
residue was applied to the top of an open-bed silica gel
column (2.5ꢂ10 cm). The column was eluted with methyl-
ene chloride. Fractions containing the ester were combined,
and evaporated under reduced pressure to give the ester. And
fractions containing pyridazinone derivative were com-
bined, and evaporated under reduced pressure to give pyrid-
azinone derivative.
4.3.6. 4-Nitrophenyl 4-nitrobenzoate (6g). Mp 158–
159 ꢀC. Rf¼0.77 (CH2Cl2). IR (KBr) 3150, 1760, 1600,
1560, 1540, 1500, 1360, 1340, 1270, 1220, 1080, 870,
1
720 cmꢁ1. H NMR (CDCl3) d: 8.40 (s, 4H), 8.36 (d, 2H,
J¼9.1 Hz), 7.96 (d, 2H, J¼9.1 Hz). 13C NMR (CDCl3) d:
162.5, 155.1, 151.2, 145.8, 133.9, 131.5, 125.5, 123.9,
122.5. Elemental analysis calcd for C13H8N2O6: C, 54.18;
H, 2.80; N, 9.72. Found: C, 54.22; H, 2.88; N, 9.81.
4.3.7. 2-Chlorophenyl 4-nitrobenzoate (6h). Mp 119–
121 ꢀC. Rf¼0.77 (CH2Cl2). IR (KBr) 3130, 3100, 1760,
1620, 1540, 1490, 1370, 1290, 1270, 1220, 1090, 900, 860,
1
4.3.1. Methyl 4-nitrobenzoate (6a). Mp 94–95 ꢀC. Rf¼0.58
(EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3120, 3080, 2950,
2850, 1720, 1610, 1530, 1440, 1350, 1310, 1280, 1100,
780, 730 cmꢁ1. H NMR (CDCl3) d: 8.45–8.37 (m, 4H),
7.53 (d, 1H, J¼7.9 Hz), 7.39–7.28 (m, 4H). 13C NMR
(CDCl3) d: 162.5, 151.1, 146.8, 134.3, 131.5, 130.5, 128.0,
127.6, 126.8, 123.8, 123.6. Elemental analysis calcd for
C13H8ClNO4: C, 56.23; H, 2.90; N, 5.04. Found: C, 56.31;
H, 2.97; N, 5.09.
1
960, 880, 820, 720 cmꢁ1. H NMR (CDCl3) d: 8.29 (d,
2H, J¼9.0 Hz), 8.21 (d, 2H, J¼9.0 Hz), 3.99 (s, 3H). 13C
NMR (CDCl3) d: 165.2, 150.6, 136.5, 130.7, 123.6, 52.9. El-
emental analysis calcd for C8H7NO4: C, 53.04; H, 3.89; N,
7.73. Found: C, 49.96; H, 3.97; N, 7.80.
4.3.8. Pyridin-3-yl 4-nitrobenzoate (6i). Mp 111–112 ꢀC.
Rf¼0.24 (EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3120,
1740, 1620, 1600, 1560, 1520, 1480, 1420, 1340, 1320,
1260, 1200, 1060, 1000, 840, 700 cmꢁ1. 1H NMR (CDCl3)
d: 8.61–8.58 (m, 2H), 8.39 (s, 4H), 7.66 (d, 1H,
J¼8.4 Hz), 7.46–7.41 (m, 1H). 13C NMR (CDCl3) d:
4.3.2. Isopropyl 4-nitrobenzoate (6b). Mp 106–108 ꢀC.
Rf¼0.67 (EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3110,
3070, 3050, 2990, 2940, 2870, 1710, 1610, 1520, 1460,
1340, 1290, 1090, 1000, 830, 710 cmꢁ1. 1H NMR (CDCl3)

J.-E. Won et al. / Tetrahedron 63 (2007) 12720–12730
12727
1
162.9, 151.1, 147.5, 143.2, 137.2, 134.1, 131.4, 129.2, 124.1,
123.8. Elemental analysis calcd for C12H8N2O4: C, 59.02; H,
3.30; N, 11.47. Found: C, 59.05; H, 3.38; N, 11.49.
2900, 1760, 1470, 1270, 1210, 1190, 1150, 1050 cmꢁ1. H
NMR (CDCl3) d: 3.55 (s, 3H), 2.24–2.15 (m, 1H), 1.18–
1.76 (m, 2H), 1.66–1.59 (m, 2H), 1.55–1.52 (m, 1H),
1.40–1.27 (m, 2H), 1.24–1.05 (m, 3H). 13C NMR (CDCl3)
d: 176.2, 51.2, 42.9, 28.9, 25.6, 25.3. Elemental analysis
calcd for C8H14O2: C, 67.57; H, 9.92. Found: C, 67.59; H,
10.01.
4.3.9. S-Phenyl 4-nitrobenzothioate (6j). Mp 155–157 ꢀC.
Rf¼0.71 (CH2Cl2). IR (KBr) 3100, 3070, 1670, 1600, 1520,
1480, 1440, 1340, 1320, 1200, 1100, 920, 850, 750,
680 cmꢁ1. H NMR (CDCl3) d: 8.34 (d, 2H, J¼8.8 Hz),
1
8.18 (d, 2H, J¼8.8 Hz), 7.53–7.48 (m, 5H). 13C NMR
(CDCl3) d: 188.8, 150.7, 141.3, 134.9, 130.1, 129.5, 128.5,
125.2, 124.0. Elemental analysis calcd for C13H9NO3S: C,
60.22; H, 3.50; N, 5.40. Found: C, 60.24; H, 3.53; N, 5.48.
4.3.16. Hexyl cyclohexanecarboxylate (6p). Liquid.
Rf¼0.85 (EtOAc/n-hexane¼1:2, v/v). IR (KBr) 2970,
2900, 1750, 1690, 1470, 1400, 1330, 1260, 1180, 1140,
1
1050 cmꢁ1. H NMR (CDCl3) d: 4.05 (t, 2H, J¼6.7 Hz),
2.33–2.24 (m, 1H), 1.19–1.86 (m, 2H), 1.77–1.72 (m, 2H),
1.66–1.57 (m, 3H), 1.51–1.23 (m, 11H), 0.89 (t, 3H,
J¼6.9 Hz). 13C NMR (CDCl3) d: 166.7, 143.3, 129.5,
129.0, 127.8, 64.8, 31.5, 28.7, 25.7, 22.5, 21.6, 14.0. Ele-
mental analysis calcd for C13H22O2: C, 74.24; H, 10.54.
Found: C, 74.23; H, 10.60.
4.3.10. 4-Nitrobenzoic anhydride. Mp 55–56 ꢀC. Rf¼0.84
(EtOAc/n-hexane¼1:1, v/v). IR (KBr) 3150, 3000, 1730,
1620, 1540, 1360, 1280, 1110, 1030, 880, 810, 720 cmꢁ1
.
1H NMR (CDCl3) d: 8.12 (d, 2H, J¼9.0 Hz), 8.12 (d, 2H,
J¼9.0 Hz). 13C NMR (CDCl3) d: 164.7, 150.5, 135.8,
130.6, 123.5. Elemental analysis calcd for C15H10N2O6: C,
57.33; H, 3.21; N, 8.91. Found: 57.37; H, 3.33; N, 8.96.
4.3.17. Phenyl cyclohexanecarboxylate (6q). Liquid.
Rf¼0.71 (EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3100,
2960, 2900, 1770, 1610, 1500, 1460, 1390, 1330, 1260,
4.3.11. Methyl 4-methylbenzoate (6k). Liquid. Rf¼0.77
(EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3030, 1740, 1620,
1210, 1170, 1140, 1040, 950 cmꢁ1. H NMR (CDCl3) d:
1
1
1450, 1290, 1190, 1120, 1030, 850, 760 cmꢁ1. H NMR
7.30 (t, 2H, J¼8.2 Hz), 7.14 (t, 1H, J¼7.4 Hz), 7.03 (d,
2H, J¼7.4 Hz), 2.56–2.46 (m, 1H), 2.05–2.00 (m, 2H),
1.80–1.75 (m, 2H), 1.66–1.50 (m, 3H), 1.38–1.21 (m, 3H).
13C NMR (CDCl3) d: 176.1, 64.2, 43.2, 31.4, 29.0, 28.6,
25.7, 25.6, 25.4, 22.5, 13.4. Elemental analysis calcd for
C13H16O2: C, 76.44; H, 7.90. Found: C, 76.50; H, 7.98.
(CDCl3) d: 7.91 (d, 2H, J¼8.2 Hz), 7.20 (d, 2H, J¼8.2 Hz),
3.87 (s, 3H), 2.37 (s, 3H). 13C NMR (CDCl3) d: 167.1,
143.5, 129.6, 129.0, 127.4, 51.8, 21.5. Elemental analysis
calcd for C9H10O2: C, 71.98; H, 6.71. Found: C, 72.03; H,
6.79.
4.3.12. Hexyl 4-methylbenzoate (6l). Liquid. Rf¼0.81
(EtOAc/n-hexane¼1:2, v/v). IR (KBr) 2940, 2850, 1720,
4.3.18. Pyridin-3-yl cyclohexanecarboxylate (6r). Liquid.
Rf¼0.50 (EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3100, 2960,
2900, 1720, 1600, 1500, 1460, 1280, 1210, 1190, 1110, 1050,
810 cmꢁ1. 1H NMR (CDCl3) d: 8.43 (d, 1H, J¼4.5 Hz), 8.40
(d, 1H, J¼2.2 Hz), 7.44 (d, 1H, J¼8.3 Hz), 7.30–7.26 (m,
1H), 2.62–2.52 (m, 1H), 2.07–2.02 (m, 2H), 1.83–1.78 (m,
2H), 1.69–1.51 (m, 3H), 1.42–1.23 (m, 3H). 13C NMR
(CDCl3) d: 173.7, 147.5, 146.5, 143.3, 129.1, 123.7, 42.9,
28.7, 25.6, 25.1. Elemental analysis calcd for C12H15NO2:
C, 70.22; H, 7.37; N, 6.82. Found: C, 70.24; H, 7.41; N, 6.85.
1
1620, 1460, 1380, 1270, 1180, 1100, 1020, 760 cmꢁ1. H
NMR (CDCl3) d: 7.93 (d, 2H, J¼8.2 Hz), 7.21 (d, 2H,
J¼8.2 Hz), 4.29 (t, 2H, J¼6.7 Hz), 2.39 (s, 3H), 1.79–1.70
(m, 2H), 1.36–1.30 (m, 6H), 0.92–0.87 (m, 3H). 13C NMR
(CDCl3) d: 166.7, 143.3, 129.5, 129.0, 127.8, 64.8, 31.5,
28.7, 25.7, 22.5, 21.6, 14.0. Elemental analysis calcd for
C14H18O2: C, 77.03; H, 8.31. Found: C, 77.11; H, 8.36.
4.3.13. Phenyl 4-methylbenzoate (6m). Mp 75–76 ꢀC.
Rf¼0.72 (EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3050,
2950, 1720, 1610, 1590, 1480, 1460, 1400, 1270, 1250,
1190, 1170, 1090, 1020, 840, 750 cmꢁ1. 1H NMR (CDCl3)
d: 8.09 (d, 2H, J¼8.2 Hz), 7.42 (t, 2H, J¼8.1 Hz), 7.30 (d,
2H, J¼8.3 Hz), 7.25–7.19 (m, 3H), 2.44 (s, 3H). 13C NMR
(CDCl3) d: 165.3, 151.1, 144.1, 130.2, 129.5, 129.3, 126.9,
125.8, 121.8, 21.8. Elemental analysis calcd for C14H12O2:
C, 79.22; H, 5.70. Found: C, 79.18; H, 5.82.
4.3.19. Methyl octanoate (6s). Liquid. Rf¼0.86 (EtOAc/n-
hexane¼1:1, v/v). IR (KBr) 2960, 2890, 1760, 1470, 1450,
1
1380, 1210, 1180 cmꢁ1. H NMR (CDCl3) d: 3.66 (s, 3H),
2.31 (t, 2H, J¼7.4 Hz), 1.62 (t, 2H, J¼7.4 Hz), 1.33–1.29
(m, 8H), 0.88 (t, 3H, J¼6.6 Hz). 13C NMR (CDCl3) d:
174.1, 51.2, 34.0, 31.6, 29.0, 28.8, 24.9, 22.5, 13.9. Elemen-
tal analysis calcd for C9H18O2: C, 68.31; H, 11.47. Found: C,
68.33; H, 11.51.
4.3.14. Pyridin-3-yl 4-methylbenzoate (6n). Mp 75–76 ꢀC.
Rf¼0.45 (EtOAc/CH2Cl2¼1:5, v/v). IR (KBr) 3120, 3050,
3000, 2930, 2850, 1740, 1650, 1610, 1580, 1470, 1430,
4.3.20. Hexyl octanoate (6t). Liquid. Rf¼0.82 (EtOAc/n-
hexane¼1:2, v/v). IR (KBr) 2960, 2900, 1760, 1580, 1400,
1
1380, 1270, 1190, 1120 cmꢁ1. H NMR (CDCl3) d: 4.06
1
1280, 1210, 1180, 1140, 940 cmꢁ1. H NMR (CDCl3) d:
(t, 2H, J¼6.7 Hz), 2.29 (t, 2H, J¼7.6 Hz), 1.66–1.57 (m,
4H), 1.40–1.23 (m, 14H), 0.92–0.86 (m, 6H). 13C NMR
(CDCl3) d: 173.9, 64.3, 34.4, 31.6, 31.4, 29.1, 28.9, 28.6,
25.6, 25.0, 22.5, 22.4, 14.0, 13.0. Elemental analysis calcd
for C14H26O2: C, 74.29; H, 11.58. Found: C, 74.33; H, 11.61.
8.56 (d, 1H, J¼2.1 Hz), 8.53 (d, 1H, J¼4.2 Hz), 8.09 (d,
2H, J¼8.2 Hz), 7.61 (d, 1H, J¼8.3 Hz), 7.41–7.36 (m, 1H),
7.33 (d, 2H, J¼8.0 Hz), 2.46 (s, 3H). 13C NMR (CDCl3) d:
164.8, 147.4, 146.9, 145.0, 143.6, 130.3, 129.4 (2), 126.0,
123.9, 21.8. Elemental analysis calcd for C13H11NO2: C,
73.23; H, 5.20; N, 6.57. Found: C, 73.25; H, 5.25; N, 6.64.
4.3.21. Phenyl octanoate (6u). Liquid. Rf¼0.66 (CH2Cl2).
IR (KBr) 3090, 2950, 2880, 1770, 1600, 1500, 1470, 1380,
4.3.15. Methyl cyclohexanecarboxylate (6o). Liquid.
Rf¼0.73 (EtOAc/n-hexane¼1:2, v/v). IR (KBr) 2970,
1300, 1200, 1140, 1100, 1030, 930 cmꢁ1 1H NMR
.
(CDCl3) d: 7.34 (t, 2H, J¼7.4 Hz), 7.18 (t, 1H, J¼7.4 Hz),

12728
J.-E. Won et al. / Tetrahedron 63 (2007) 12720–12730
7.08–7.03 (m, 2H), 2.52 (t, 2H, J¼7.4 Hz), 1.78–1.69 (m,
2H), 1.42–1.30 (m, 8H), 0.89 (t, 3H, J¼6.9 Hz). 13C NMR
(CDCl3) d: 172.2, 150.9, 129.4, 124.7, 121.6, 34.4, 31.7,
29.1, 29.0, 25.0, 22.7, 14.1. Elemental analysis calcd for
C14H20O2: C, 76.33; H, 9.15. Found: C, 76.36; H, 9.23.
NMR (CDCl3) d: 172.7, 64.3, 31.4, 28.7, 26.9, 26.8, 25.6,
22.7, 21.8, 18.7, 13.9. Elemental analysis calcd for
C12H20O2: C, 73.43; H, 10.27. Found: C, 73.47; H, 10.31.
4.3.28. Phenyl 2,2-dimethylcyclopropanecarboxylate
(6ab). Liquid. Rf¼0.70 (EtOAc/n-hexane¼1:2, v/v). IR
(KBr) 3100, 2970, 2900, 1760, 1660, 1600, 1500, 1450,
4.3.22. Pyridin-3-yl octanoate (6v). Liquid. Rf¼0.43
(EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3060, 2950, 2880,
1780, 1740, 1600, 1490, 1440, 1400, 1290, 1220, 1140,
1400, 1280, 1200, 1150, 1100, 1080 cmꢁ1 1H NMR
.
(CDCl3) d: 7.29 (t, 2H, J¼8.2 Hz), 7.12 (t, 1H, J¼7.4 Hz),
7.07–7.03 (m, 2H), 1.71–1.66 (m, 1H), 1.28 (s, 3H), 1.17
(t, 1H, J¼4.7 Hz), 1.15 (s, 3H), 0.93–0.89 (m, 1H). 13C
NMR (CDCl3) d: 171.2, 151.2, 129.4, 125.6, 121.8, 26.9,
26.8, 24.1, 22.8, 18.8. Elemental analysis calcd for
C12H14O2: C, 75.76; H, 7.42. Found: C, 75.81; H, 7.47.
1120, 1040 cmꢁ1 1H NMR (CDCl3) d: 8.44 (d, 1H,
.
J¼4.7 Hz), 8.40 (d, 1H, J¼2.6 Hz), 7.47–7.42 (m, 1H),
7.31–7.26 (m, 1H), 2.56 (t, 2H, J¼7.4 Hz), 1.78–1.68 (m,
2H), 1.40–1.24 (m, 8H), 0.87 (t, 3H, J¼7.0 Hz). 13C NMR
(CDCl3) d: 171.7, 147.4, 146.7, 143.4, 129.2, 123.8, 34.2,
31.6, 29.0, 28.8, 24.8, 22.5, 14.0. Elemental analysis calcd
for C13H19NO2: C, 70.56; H, 8.65; N, 6.33. Found: C,
70.59; H, 8.67; N, 6.37.
4.3.29. Pyridin-3-yl 2,2-dimethylcyclopropanecarboxy-
late (6ac). Liquid. Rf¼0.62 (EtOAc/CH2Cl2¼1:5, v/v). IR
(KBr) 3100, 3040, 2990, 2900, 1760, 1600, 1490, 1440,
1
4.3.23. Methyl 2,2-diphenylacetate (6w). Mp 58–59 ꢀC.
Rf¼0.63 (EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3070,
3040, 2950, 1730, 1600, 1500, 1460, 1430, 1340, 1320,
1280, 1190, 1150, 1000, 840, 800 cmꢁ1. 1H NMR (CDCl3)
d: 7.31–7.12 (m, 10H), 5.03 (s, 1H), 3.72 (s, 3H). 13C
NMR (CDCl3) d: 173.0, 138.7, 128.6, 127.6, 127.3, 57.1,
52.3. Elemental analysis calcd for C15H14O2: C, 79.62; H,
6.24. Found: C, 79.67; H, 6.25.
1400, 1280, 1230, 1140, 1100, 1080, 1040, 980 cmꢁ1. H
NMR (CDCl3) d: 8.46–8.43 (m, 2H), 7.50–7.46 (d, 1H,
J¼8.3 Hz), 7.33–7.29 (m, 1H), 1.78–1.74 (m, 1H), 1.30 (s,
3H), 1.25 (s, 3H), 1.23 (t, 1H, J¼5.1 Hz), 1.07–1.03 (m,
1H). 13C NMR (CDCl3) d: 170.9, 147.6, 146.5, 143.5,
129.4, 123.8, 26.8, 26.6, 24.8, 23.2, 18.7. Elemental analysis
calcd for C11H13NO2: C, 69.09; H, 6.85; N, 7.32. Found: C,
69.15; H, 6.87; N, 7.34.
4.3.24. Hexyl 2,2-diphenylacetate (6x). Liquid. Rf¼0.70
(CH2Cl2). IR (KBr) 3090, 3050, 2950, 2890, 1740, 1610,
1500, 1460, 1400, 1320, 1290, 1240, 1200, 1160, 1010,
4.3.30. Methyl furan-2-carboxylate (6ad). Liquid.
Rf¼0.75 (EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3170,
3040, 2990, 1750, 1600, 1500, 1450, 1400, 1320, 1250,
1
1
760 cmꢁ1. H NMR (CDCl3) d: 7.32–7.19 (m, 10H), 5.01
1210, 1190, 1040, 980, 780 cmꢁ1. H NMR (CDCl3) d:
(s, 1H), 4.13 (t, 2H, J¼6.7 Hz), 1.61–1.54 (m, 2H), 1.30–
1.20 (m, 6H), 0.85 (t, 3H, J¼7.0 Hz). 13C NMR (CDCl3)
d: 172.6, 138.9, 128.7, 128.6, 127.3, 65.4, 57.3, 31.4, 28.6,
25.5, 22.6, 14.0. Elemental analysis calcd for C20H22O2:
C, 81.60; H, 7.53. Found: C, 81.61; H, 7.58.
7.62–7.61 (m, 1H), 7.18 (d, 1H, J¼3.5 Hz), 6.53–6.51 (m,
1H), 3.89 (s, 3H). 13C NMR (CDCl3) d: 158.9, 146.2,
144.4, 118.0, 111.9, 51.5. Elemental analysis calcd for
C6H6O3: C, 57.14; H, 4.80. Found: C, 57.18; H, 4.86.
4.3.31. Hexyl furan-2-carboxylate (6ae). Liquid. Rf¼0.61
(EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3150, 2950, 2870,
1730, 1580, 1480, 1400, 1300, 1230, 1170, 1110,
4.3.25. Phenyl 2,2-diphenylacetate (6y). Mp 67–68 ꢀC.
Rf¼0.72 (EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3100,
3050, 1760, 1600, 1500, 1460, 1320, 1240, 1200, 1270,
1
760 cmꢁ1. H NMR (CDCl3) d: 7.58–7.57 (m, 1H), 7.17
1250, 1090, 960, 760, 740, 710, 700 cmꢁ1
.
1H NMR
(d, 1H, J¼3.5 Hz), 6.51–6.49 (m, 1H), 4.30 (t, 2H,
J¼6.8 Hz), 1.79–1.70 (m, 2H), 1.35–1.26 (m, 6H), 0.92–
0.85 (m, 3H). 13C NMR (CDCl3) d: 18.8, 146.1, 144.9,
117.6, 111.7, 65.0, 31.4, 28.6, 25.5, 22.5, 13.9. Elemental
analysis calcd for C11H14O3: C, 68.02; H, 7.27. Found: C,
68.05; H, 7.34.
(CDCl3) d: 7.44–7.18 (m, 13H), 7.07–7.03 (m, 2H), 5.26
(s, 1H). 13C NMR (CDCl3) d: 171.0, 150.8, 138.2, 129.4,
128.7, 127.5, 125.9, 121.4, 57.1. Elemental analysis calcd
for C20H16O2: C, 83.31; H, 5.59. Found: C, 83.38; H, 5.61.
4.3.26. Pyridin-3-yl 2,2-diphenylacetate (6z). Mp 61–63 ꢀC.
Rf¼0.62 (EtOAc/CH2Cl2¼1:5, v/v). IR (KBr) 3100, 3050,
1680, 1600, 1510, 1490, 1470, 1440, 1380, 1330, 1230,
4.3.32. Phenyl furan-2-carboxylate (6af). Mp 38–40 ꢀC.
Rf¼0.66 (EtOAc/n-hexane¼1:2, v/v). IR (KBr) 3150,
3080, 1740, 1600, 1570, 1490, 1470, 1400, 1300, 1220,
1200, 1170, 1090, 1010, 930, 910 cmꢁ1. 1H NMR (CDCl3)
d: 7.66–7.65 (m, 1H), 7.43–7.36 (m, 3H), 7.28–7.18 (m,
3H), 6.58–6.56 (m, 1H). 13C NMR (CDCl3) d: 156.9,
150.2, 147.2, 144.0, 129.5, 126.1, 121.6, 119.5, 112.2. Ele-
mental analysis calcd for C11H14O3: C, 70.21; H, 4.29.
Found: C, 70.27; H, 4.32.
1
1150, 1040, 960, 760, 720 cmꢁ1. H NMR (CDCl3) d: 8.47
(d, 1H, J¼3.6 Hz), 8.40 (d, 1H, J¼2.4 Hz), 7.44–7.29 (m,
12H), 5.29 (s, 1H). 13C NMR (CDCl3) d: 170.6, 147.5,
147.1, 143.3, 137.8, 129.1, 128.9, 128.6, 127.7, 123.9, 57.0.
Elemental analysis calcd for C19H15NO2: C, 78.87; H, 5.23;
N, 4.84. Found: C, 78.91; H, 5.27; N, 4.89.
4.3.27. Hexyl 2,2-dimethylcyclopropanecarboxylate
(6aa). Liquid. Rf¼0.78 (EtOAc/n-hexane¼1:2, v/v). IR
(KBr) 2950, 2890, 1740, 1470, 1410, 1390, 1330, 1280,
4.3.33. Pyridin-3-yl furan-2-carboxylate (6ag). Liquid.
Rf¼0.46 (EtOAc/n-hexane¼1:1, v/v). IR (KBr) 3100,
3050, 1750, 1610, 1560, 1500, 1440, 1330, 1240, 1200,
1
1180, 1130, 1100, 1030 cmꢁ1. H NM (CDCl3) d: 4.06 (t,
1
2H, J¼6.8 Hz), 1.67–1.58 (m, 2H), 1.51–1.46 (m, 1H),
1.38–1.26 (m, 6H), 1.21 (s, 3H), 1.16 (s, 3H), 1.07 (t, 1H,
J¼5.2 Hz), 0.89 (t, 3H, J¼6.9 Hz), 0.85–0.81 (m, 1H). 13C
1160, 1080, 980 cmꢁ1. H NMR (CDCl3) d: 8.57 (d, 1H,
J¼2.4 Hz), 8.54 (d, 1H, J¼4.7 Hz), 7.71–7.70 (m, 1H),
7.63 (d, 1H, J¼8.3 Hz), 7.43 (d, 1H, J¼3.6 Hz), 7.41–7.38

J.-E. Won et al. / Tetrahedron 63 (2007) 12720–12730
12729
(m, 1H), 6.63–6.62 (m, 1H). 13C NMR (CDCl3) d: 156.3,
147.6, 147.1, 143.4, 143.3, 137.0, 129.3, 124.0, 120.2,
112.4. Elemental analysis calcd for C11H14O3: C, 63.49;
H, 3.73; N, 7.40. Found: C, 63.51; H, 3.75; N, 7.44.
4.3.40. N-(4-Hydroxyphenyl)octanamide (6am). Mp 114–
116 ꢀC. Rf¼0.57 (EtOAc). IR (KBr) 3311, 3194, 3144, 3069,
3041, 2949, 2923, 2866, 2849, 1651, 1588, 1545, 1515,
1450, 1379, 1245, 1184, 941, 832 cmꢁ1
.
1H NMR
(DMSO) d: 13.7 (s, 1H), 7.33 (t, 2H, J¼11.9 Hz), 6.65 (t,
2H, J¼12.0 Hz), 2.22 (t, 2H, J¼14.8 Hz), 1.56 (t, 2H,
J¼13.5 Hz), 1.27–1.18 (m, 8H), 0.86 (t, 3H, J¼13.0 Hz).
13C NMR (DMSO) d: 171.0, 153.5, 137.1(2), 121.2, 115.4,
36.7, 31.6, 29.1, 28.9, 25.7, 22.5, 14.4. Elemental analysis
calcd for C14H21NO2: C, 71.46; H, 8.99; N, 5.95. Found:
C, 71.51; H, 9.02; N, 5.97.
4.3.34. Hexyl benzoate (6ah). Liquid. Rf¼0.65 (EtOAc/n-
hexane¼1:4, v/v). IR (KBr) 3050, 2990, 1730, 1470, 1190,
1
1120, 1090, 1040, 720 cmꢁ1. H NMR (CDCl3) d: 8.04 (d,
2H, J¼7.1 Hz), 7.49 (t, 1H, J¼7.3 Hz), 7.39 (t, 2H,
J¼7.7 Hz), 4.29 (t, 2H, J¼7.0 Hz), 1.78–1.68 (m, 2H),
1.44–1.29 (m, 6H), 0.89 (t, 3H, J¼7.0 Hz). 13C NMR
(CDCl3) d: 166.4, 132.6, 130.5, 129.4, 128.2, 64.9, 31.4,
28.7, 25.7, 22.5, 13.9. Elemental analysis calcd for
C13H18O2: C, 75.69; H, 8.80. Found: C, 75.73; H, 8.82.
4.3.41. N-(4-Hydroxyphenyl)benzamide (6an). Mp 207–
209 ꢀC. Rf¼0.48 (EtOAc/n-hexane¼1:2, v/v). IR (KBr)
3410, 3350, 1660, 1620, 1600, 1560, 1530, 1450, 1340,
1
4.3.35. Phenyl benzoate (6ai). Mp 66–68 ꢀC (lit.14 mp 68–
70 ꢀC). Rf¼0.71 (EtOAc/n-hexane¼1:3, v/v). IR (KBr)
3080, 1740, 1600, 1500, 1460, 1270, 1210, 1190, 1180,
1260, 1240, 1120, 840 cmꢁ1. H NMR (CDCl3) d: 10.03
(s, NH, D2O exchangeable), 9.26 (s, OH), 7.93 (d, 2H,
J¼6.8 Hz), 7.56–7.48 (m, 5H), 6.75 (d, 2H, J¼8.8 Hz).
13C NMR (CDCl3) d: 165.4, 154.2, 137.1, 135.6, 131.7,
131.2, 128.8, 128.0, 122.7, 115.4. Elemental analysis calcd
for C13H11NO2: C, 73.23; H, 5.20; N, 6.57. Found: C,
73.25; H, 5.24; N, 6.60.
1090, 1070, 1040, 1010, 760, 720, 700 cmꢁ1 1H NMR
.
(CDCl3) d: 8.20 (d, 2H, J¼7.1 Hz), 7.62 (t, 1H, J¼7.5 Hz),
7.49 (t, 2H, J¼7.3 Hz), 7.42 (t, 2H, J¼7.8 Hz), 7.28–7.19
(m, 3H). 13C NMR (CDCl3) d: 165.2, 151.0, 133.6, 130.2,
129.6, 129.5, 128.6, 125.9, 121.8. Elemental analysis calcd
for C13H10O2: C, 78.77; H, 5.09. Found: C, 78.79; H, 5.14.
4.3.42. Octanoic anhydride. Liquid. Rf¼0.90 (EtOAc/n-
hexane¼1:4, v/v). IR (KBr) 2954, 2927, 2855, 1818, 1749,
1
4.3.36. S-Phenyl benzothioate (6aj). Mp 61–63 ꢀC.
Rf¼0.73 (CH2Cl2). IR (KBr) 3090, 1740, 1680, 1600,
1490, 1440, 1260, 1200, 1180, 1060, 1040, 900, 760,
1463, 1411, 1375, 1273, 1260, 1040, 761, 747 cmꢁ1. H
NMR (CDCl3) d: 5.03 (s, 2H), 2.45 (t, 8H, J¼7.4 Hz),
2.35 (t, 1H, J¼7.4 Hz), 1.71–1.61 (m, 10H), 1.31–1.29 (t,
41H, J¼8.0 Hz), 0.88 (t, 15H, J¼6.4 Hz). 13C NMR
(CDCl3) d: 169.6, 35.2, 31.6, 28.8 (2), 24.2, 22.5, 14.0. Ele-
mental analysis calcd for C16H30O3: C, 71.07; H, 11.18.
Found: C, 71.13; H, 11.20.
1
690 cmꢁ1. H NMR (CDCl3) d: 8.03 (d, 2H, J¼7.1 Hz),
7.60 (t, 1H, J¼7.3 Hz), 7.54–7.43 (m, 7H). 13C NMR
(CDCl3) d: 190.2, 135.1, 133.7, 130.2, 129.6, 129.3, 128.8,
128.6, 127.5. Elemental analysis calcd for C13H10OS: C,
72.87; H, 4.70; S, 14.96. Found: 72.90; H, 4.76; S, 15.00.
4.3.43. Benzoic anhydride. Mp 40–41 ꢀC (lit.16 mp 38–
42 ꢀC). Rf¼0.40 (EtOAc/n-hexane¼1:4, v/v). IR (KBr)
3100, 1780, 1720, 1610, 1500, 1460, 1430, 1340, 1300,
4.3.37. Diphenyldisulfide. Mp 56–58 ꢀC (lit.15 mp 58–
60 ꢀC). Rf¼0.81 (CH2Cl2). IR (KBr) 3060, 2930, 1580,
1
1
1480, 1440, 1300, 1070, 1020, 900, 740, 690 cmꢁ1. H
1230, 1180, 1050, 1030, 1010, 950, 790 cmꢁ1. H NMR
NMR (CDCl3) d: 7.71–7.47 (m, 2H), 7.29 (t, 2H,
J¼7.0 Hz), 7.21 (t, 1H, J¼7.1 Hz). 13C NMR (CDCl3) d:
137.1, 129.1, 127.6, 127.2. Elemental analysis calcd for
C12H10S2: C, 66.01; H, 4.62. Found: C, 66.04; H, 4.69.
(CDCl3) d: 8.16 (m, 4H), 7.67 (t, 2H, J¼7.5 Hz), 7.52 (t, 4H,
J¼7.8 Hz). 13C NMR (CDCl3) d: 162.4, 147.4, 139.6, 131.2,
129.1, 128.6, 127.7, 127.6, 127.4. Elemental analysis calcd
for C15H12O2: C, 80.34; H, 5.39. Found: C, 80.36; H, 5.43.
4.3.38. S-2-Hydroxyethyl octanethioate (6ak). Liquid.
Rf¼0.56 (EtOAc/n-hexane¼1:1, v/v). IR (KBr) 3443,
2953, 2925, 2854, 1732, 1681, 1456, 1415, 1273, 1123,
Acknowledgements
1044, 748 cmꢁ1
.
1H NMR (CDCl3) d: 3.72 (t, 2H,
This work was supported by a grant from the Korean Science
and Engineering Foundation (KOSEF) to the Environmental
Biotechnology National Core Research Center (Grant No.:
R15-2003-012-02001-0).
J¼11.3 Hz), 3.5 (s, 1H), 3.1 (t, 2H, J¼12.9 Hz), 2.57 (t,
2H, J¼15.1 Hz), 1.64 (m, 2H), 1.23 (t, 8H, J¼7.7 Hz),
0.88 (t, 3H, J¼13.4 Hz). 13C NMR (CDCl3) d: 200.0, 61.4,
44.0, 31.5, 31.4, 28.8, 25.5, 22.5, 13.9. Elemental analysis
calcd for C10H20O2S: C, 58.78; H, 9.87. Found: C, 58.80;
H, 9.91.
References and notes
4.3.39. S-2-Hydroxyethyl benzothioate (6al). Liquid.
Rf¼0.61 (EtOAc/CH2Cl2¼1:3, v/v). IR (KBr) 3450, 3350,
3100, 2950, 2900, 1670, 1600, 1460, 1410, 1300, 1210,
1. (a) Larock, R. C. Comprehensive Organic Transformations; VCH:
New York, NY, 1989; p 966; (b) Katrizky, A. R.; Otto Meth, C.;
Charles, W. R. Comprehensive Organic Functional Group
Transformations; Pergamon: Cambridge, UK, 1995; Vol. 5;
(c) Franklin, A. S. J. Chem. Soc., Perkin Trans. 1 1998, 2451.
2. For selected examples: (a) Hassner, A.; Alexanian, V.
Tetrahedron Lett. 1978, 19, 4475; (b) Ziegler, F. E.; Berger,
G. D. Synth. Commun. 1979, 9, 539; (c) Saigo, K.; Usui, M.;
Kikuchi, K.; Shimada, E.; Mukaiyama, T. Bull. Chem. Soc.
Jpn. 1977, 50, 1863; (d) Inanaga, J.; Hirata, K.; Saeki, H.;
1
1180, 1170, 1150, 1020, 920 cmꢁ1. H NMR (DMSO) d:
7.95 (d, 2H, J¼7.1 Hz), 7.54 (t, 1H, J¼7.5 Hz), 7.41 (t,
2H, J¼7.4 Hz), 3.84 (t, 2H, J¼6.2 Hz), 3.34 (s, OH), 3.27
(t, 2H, J¼6.3 Hz). 13C NMR (DMSO) d: 192.3, 136.8,
133.6, 128.6, 127.3, 61.6, 31.7. Elemental analysis calcd
for C9H10O2S: C, 59.32; H, 5.53; S, 17.59. Found: C,
59.34; H, 5.57; S, 17.62.

12730
J.-E. Won et al. / Tetrahedron 63 (2007) 12720–12730
Katsuki, T.; Yamaguchi, M. Bull. Chem. Soc. Jpn. 1979, 52,
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2, 4 and 5; Eshghi, H.; Rafei, M.; Karimi, M. H. Synth.
Commun. 2001, 31, 771.
7. Kim, J. J.; Kweon, D. H.; Cho, S. D.; Kim, H. K.; Jung, E. Y.;
Lee, S. G.; Falck, J. R.; Yoon, Y. J. Tetrahedron 2005, 61,
5889.
8. Park, Y. D.; Kim, J. J.; Cho, S. D.; Lee, S. G.; Falck, J. R.; Yoon,
Y. J. Synthesis 2005, 1136.
9. Lee, S. G.; Kim, J. J.; Kim, H. K.; Kweon, D. H.; Kang, Y. J.;
Cho, S. D.; Kim, S. K.; Yoon, Y. J. Curr. Org. Chem. 2004, 8,
1463.
1989; (e) Ohta, S.; Shimabayashi, A.; Aono, M.; Okamoto,
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Lizarbe, J. R. F.; Bilbao, A. Z. Synthesis 1980, 547; (g) Kim,
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Nahmany, M.; Melman, A. Org. Lett. 2001, 3, 3733; (i)
Saitoh, K.; Shina, I.; Mukaiyama, T. Chem. Lett. 1988, 679;
(j) Brewster, J. H.; Ciotti, C. J., Jr. J. Am. Chem. Soc. 1955,
77, 6214; (k) Hendrickson, J. B.; Schwartzman, S. M.
Tetrahedron Lett. 1975, 16, 277; (l) Candrasekaran, S.;
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T.; Ichikawa, J.; Asami, M. Chem. Lett. 1983, 683; (n)
Ramaiah, M. J. Org. Chem. 1985, 50, 4991; (o) Shiina, I.;
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12. Compound 1 was also reacted with 2 in methylene chloride,
THF, acetone, and toluene in the presence of triethylamine to
give compound 3 in 85–95% yield, respectively.
13. Esterification of 4a with methanol in refluxing toluene, ace-
tone, acetonitrile, methylene chloride, and diethyl ether also
gave the corresponding ester 6a in good to excellent yields
under same condition.
14. Aldrich Hand Book of Fine Chemicals; Sigma–Aldrich: Korea,
2007–2008; p 1936.
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