Process for producing 2-aceylfuran derivatives

2-Acylfuran derivatives ##STR1## (R: alkyl, phenyl, etc.; R.sub.1 : H, alkyl) are prepared in high yield by reaction, in the presence of a boron trifluoride complex catalyst, of a furan compound ##STR2## (X: H, Cl, Br; Y: Cl, Br) or with RCOOH in the presence of (XYCHCO).sub.2 O.

The present invention relates to a process for producing 2-acylfuran 
derivatives represented generally by the following formula; 
##STR3## 
wherein R is typically alkyl or phenyl group and R.sub.1 is hydrogen or 
alkyl group. 
The 2-acylfuran derivatives are very important as intermediates of 
medicines or of agricultural chemicals, particularly as an intermediate of 
prostaglandings. 
For producing such 2-acylfuran derivatives, various processes have hitherto 
been known, and the typical processes are exemplified below: 
(a) J.C.S., 2262 (1982) 
##STR4## 
(b) J.C.S., 2723 (1963) 
##STR5## 
(c) U.S. Pat. No. 4,254,043 
##STR6## 
These processes mentioned above, however, are not always industrially 
satisfactory because the yield is low in processes (a) and (b), and 
reagents used for the reaction are very expensive in process (c). 
Accordingly, it is an object of the present invention to provide process 
for producing 2-acylfuran derivatives represented generally by the 
above-mentioned formula in high yield, and advantageously to industries 
concerned. 
According to the present invention, there is provide a process for 
producing 2-acylfuran derivatives represented by the formula (I); 
##STR7## 
wherein R is an alkyl group having 1 to 18 carbon atoms, an alkenyl group 
having 3 to 8 carbon atoms, an alkynyl group having 3 to 8 carbon atoms, a 
cyclic alkyl group having 4 to 7 carbon atoms, phenyl group, a phenyl 
group having one or two substituents selected from the group consisting of 
alkyl groups having 1 to 5 carbon atoms, alkoxyl groups having 1 to 5 
carbon atoms and halogen atoms, an aralkyl group having 7 to 12 carbon 
atoms, an alkyl group having 2 to 8 carbon atoms which has a substituent 
of an alkoxyl group having 1 to 5 carbon atoms, or an alkyl group having 2 
to 8 carbon atoms which has a substituent of an alkoxycarbonyl group 
having 2 to 6 carbon atoms; and R.sub.1 is hydrogen atom or a lower alkyl 
group; which comprises reacting, in a solvent and in the presence of a 
boron trifluoride complex catalyst, a furan compound represented by the 
formula (II); 
##STR8## 
wherein R.sub.1 has the same meaning as defined above, with either (a) a 
mixed acid anhydride represented by the formula (III); 
##STR9## 
wherein R has the same meaning as defined above, X is hydrogen, chlorine 
or bromine atom, and Y is chlorine or bromine atom, or with (b) a 
carboxylic acid represented by the formula (IV); 
EQU RCOOH (IV) 
wherein R has the same meaning as defined above in the presence of an acid 
anhydride represented by the formula (V); 
EQU (XYCHCO).sub.2 O (V) 
wherein X and Y have the same meanings as defined above. 
Preferred solvents used in the present invention include aromatic 
hydrocarbons such as benzene, toluene, xylene and the like; and 
halogenated hydrocarbons such as carbon tetracloride, dichloromethane, 
dichloroethane, tetrachloroethylene, monochlorobenzene and the like. These 
are used alone or in combination of two or more, and the amount of such 
solvent is not critical. 
As the catalyst, boron trifluoride or a boron trifluoride complex is used, 
and the boron trifluoride complex includes boron trifluoride-diethyl ether 
complex, boron trifluoride-methanol complex, boron trifluorideacetic acid 
complex, and the like. 
Furan compounds used in the present invention include furan, 2-methylfuran, 
2-ethylfuran and the like. 
In the process of (a) mentioned above, though the amount of catalyst to be 
used is generally from 0.05 to 1 equivalents based on the mixed acid 
anhydride (III), the reaction proceeds even in an amount of catalyst of 
from 0.05 to 0.15. The amount of furan compound (II) is necessarily 1.0 or 
more equivalents, preferably from 1.2 to 2 equivalents based on the mixed 
acid anhydride (III). The reaction temperature is in a range of generally 
from -5.degree. to 100.degree. C., preferably from 30.degree. to 
70.degree. C. The reaction time is generally in a range of from 0.5 to 20 
hours, but it to not particularly limited. 
The mixed acid anhydride represented by the formula (III), which is one of 
starting materials for the above-mentioned reaction, can be produced by 
reacting a carboxylic acid represented by the formula (VI); 
EQU RCOOH (VI) 
wherein R has the same meaning as defined above, with a haloacetic acid 
compound represented by the formula (VII); 
EQU XYCHCOZ (VII) 
wherein Z is hydroxyl group, chlorine or bromine atom, and X and Y are as 
defined above. 
The carboxylic acid represented by the formula (VI) includes aliphatic 
carboxylic acids having 1 to 18 carbon atoms such as acetic acid, 
propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric 
acid, hexanoic acid, heptanoic acid, octanoic acid, lauric acid, decanoic 
acid, stearic acid, and the like; unsaturated aliphatic carboxylic acids 
having 3 to 8 carbon atoms such as acrylic acid, crotonic acid, 
trans-2-pentenoic acid, 4-pentenoic acid, trans-2-hexanoic acid, 
trans-3-hexanoic acid, cis-3-hexanoic acid, trans-2-methyl-2-pentenoic 
acid, 4-pentynoic acid and the like; saturated alicyclic carboxylic acids 
having 4 to 8 carbon atoms such as cyclopentane carboxylic acid, 
cyclohexane carboxylic acid and the like; such aromatic carboxylic acids 
being unsubstituted or mono- or di-substituted by alkyl group having 1 to 
3 carbon atoms, alkoxyl group having 1 to 3 carbon atoms or halogen atom, 
such as benzoic acid, 4-methylbenzoic acid, 2,4-dimethylbenzoic acid, 
4-methoxybenzoic acid, 4-bromobenzoic acid and the like; aralkyl 
carboxylic acids having 7 to 12 carbon atoms such as phenylacetic acid, 
3-phenylpropionic acid, 2-methyl-2-phenylacetic acid and the like; 
aliphatic carboxylic acids having 2 to 8 carbon atoms which are 
substituted by alkoxyl group having 1 to 5 carbon atoms or alkoxycarbonyl 
group having 2 to 6 carbon atoms such as 3-methoxypropionic acid, 
5-ethoxypentanoic acid, butoxypentanoic acid, 6-methoxyhexanoic acid, 
succinic acid monoethyl ester, glutaric acid monomethyl ester, suberic 
acid monomethyl ester and the like. 
When a haloacetic acid of the formula (VII) in which substituent Z is 
hydroxyl group, is used as the haloacetic acid compound, the aimed mixed 
acid anhydride can be obtained by the dehydration reaction in the presence 
or absence of a dehydrating agent, however, the aimed compound is easily 
available by the reaction using a haloacetyl halide in which the 
substituent Z is chlorine or bromine atom in the presence of an organic 
base and in a solvent. In the latter reaction, the amount of haloacetyl 
halide is generally from 1 to 1.5 equivalents based on the carboxylic 
acid. The organic base used in this reaction includes triethylamine, 
pyridine, diethylaniline and the like, and the amount thereof is generally 
from 1 to 1.5 equivalents based on the carboxylic acid. The reaction 
temperature is generally in a range of from -20.degree. to 50.degree. C. 
The reaction time is generally in a range of from 0.5 to 10 hours, but it 
is not particularly limited. 
The reaction mixture obtained is subjected to filtration for separating off 
the resulting hydrochloride or hydrobromide salt of organic base to obtain 
crude solution of the mixed acid anhydride, which is then purified to 
obtain the mixed acid anhydride. The crude solution mentioned above can be 
used as it is for the next reaction with a furan compound. Accordingly, it 
is advantageous to use a solvent same as the solvent used in the next 
step. 
In the case of the process (b) mentioned above, same carboxylic acids as 
exemplified for carboxylic acids of (VI) may be used, and the acid 
anhydride (V) includes, for example, chloroacetic anhydride, bromoacetic 
anhydride, dichloroacetic anhydride and the like. The amount of furan 
compound (II) is necessarily 1.0 equivalent or more, preferably from 1.2 
to 1.5 equivalents based on the carboxylic acid (IV). The amount of acid 
anhydride (V) is 1.0 equivalent or more, preferably from 1.1 to 1.3 
equivalents based on the carboxylic acid (IV). Although the amount of the 
the boron trifluoride or boron trifuluoride complex catalyst is generally 
from 0.12 to 0.2 equivalents based on the carboxylic acid (IV), this 
amount is not restrictive and may be used in an amount of more than the 
above-mentioned amount. The reaction temperature is generally in a range 
of from -5.degree. to 150.degree. C, preferably from 15.degree. to 
75.degree. C. The reaction time is generally in a range of from 0.5 to 20 
hours, but it is not particularly limited. 
The reaction mixture thus obtained is post-treated in usual manners and 
then purified by methods such as distillation, column chromatography or 
the like, if necessary, to obtain in high yield the aimed 2-acylfuran 
derivatives(I). 
Thus, according to the present invention, aimed 2-acylfuran derivatives (I) 
can be produced advantageously for the industry from a furan compound (II) 
and a mixed acid anhydride (III) or a carboxylic acid (IV). Moreover, 
since boron trifluoride, boron trifuloride complexes and acid anhydrides 
are commercially available cheeply, industrial value of the present 
invention is enhanced further.

The present invention will be described in more detail below by way of 
Examples. 
EXAMPLE 1 
A four neck flask equipped with a stirrer and a thermometer was charged 
with 9.41 g (0.05 mole) of suberic acid monomethyl ester, 5.11 g (0.0505 
mole) of triethylamine and 60 ml of carbon tetrachloride. Under stirring, 
5.71 g (0.0505 mole) of monochloroacetyl chloride was added dropwise 
thereto at 0.degree. to 5.degree. C. After completion of dropping, the 
reaction was continued at room temperature for 3 hours. After completion 
of the reaction, the reaction mixture was filtered under reduced pressure 
to remove formed hydrochloride salt of triethylamine. 
To the filtrate were added 5.11 g (0.075 mole) of furan and 0.71 g (0.005 
mole) of boron trifluoridediethyl ether complex and the resulting mixture 
was heated at 40.degree. C. for 4 hours. After completion of the reaction, 
the reaction solution was cooled and washed successively with 50 ml of 
water, 50 ml of 5% aqueous sodium carbonate solution and 50 ml of water. 
The organic layer was dried over anhydrous magnesium sulfate and then 
concentrated under reduced pressure to obtain a crude product. The crude 
product was distilled under reduced pressure to obtain 9.75 g of pale 
yellow liquid 2-(7-methylcarbonyl1-oxoheptyl)furan. 
Yield: 81.8% 
b.p.: 134.degree.-136.degree. C./0.32-0.35 mmHg. 
EXAMPLE 2 
A four neck flask equipped with a stirrer and a thermometer was charged 
with 9.41 g (0.05 mole) of suberic acid monomethyl ester, 5.06 g (0.05 
mole) of triethylamine and 60 ml of carbon tetrachloride. Under stirring, 
7.37 g (0.05 mole) of dichloroacetyl chloride was added dropwise thereto 
at 0 to 5.degree. C. After completion of dropping, the stirring was 
continued at room temperature for 3 hours. After completion of the 
reaction, the reaction mixture was filtered under reduced pressure to 
remove formed hydrochloride salt of triethylamine. 
To the filtrate were added 5.11 g (0.075 mole) of furan and 0.71 g (0.005 
mole) of boron trifluoridediethyl ether complex in this order and the 
resulting mixture was then stirred at 50.degree. C. for 2 hours. After 
completion of the reaction, the reaction mixture was cooled and washed 
successively with 50 ml of water, 50 ml of 5% aqueous sodium carbonate 
solution and 50 ml of water. The organic layer was dried over anhydrous 
magnesium sulfate and then concentrated under reduced pressure to obtain 
10.65 g of a crude product. The crude product was distilled under reduced 
pressure to obtain 9.5 g of pale yellow oily 
2-(7-methoxycarbonyl-1-oxoheptyl) furan. 
Yield: 79.7% 
b.p.: 134.degree.-136.degree. C./0.32-0.35 mmHg. 
EXAMPLE 3 
A four neck flask equipped with a stirrer and a thermometer was charged 
with 6.51 g (0.05 mole) of heptanoic acid, 5.11 g (0.0505 mole) of 
triethylamine and 60 ml of carbon tetrachloride. Thereto was added 5.71 g 
(0.05 mole) of monochloroacetylchloride dropwise at 0 to 5.degree. C. 
After completion of dropping, the stirring was continued at room 
temperature for 3 hours. After completion of the reaction, the reaction 
mixture was filtered under reduced pressure to remove formed hydrochloride 
salt of triethylamine. 
To the filtrate were added 5.11 g (0.075 mole) of furan and 0.71 g (0.005 
mole) of boron trifluoridediethyl ether complex and stirring was continued 
at 50.degree. C. for 3 hours. After completion of the reaction, the 
reaction solution was cooled and washed successively with water, 5% 
aqueous sodium carbonate solution and water. The organic layer was 
concentrated under reduced pressure and the resulting concentrated residue 
was purified by silica gel-filled column chromatography to obtain 7.6 g of 
2-hepanoylfuran. 
Yield: 85% 
n.sub.D.sup.25 : 1.4820 
EXAMPLES 4 to 16 
Reaction and post-treatment were carried out in the same manner as in 
Example 1, except that each carboxylic acid (0.05 mole) shown in Table 1 
was a substituent for suberic acid monomethyl ester in Example 1, to 
obtain results shown in Table 1. 
TABLE 1 
__________________________________________________________________________ 
Starting carboxylic acid Produced 2-acylfuran derivative 
Example Amount 
Amount Physical 
No. Name of compound 
used produced 
Yield Name of compound properties 
__________________________________________________________________________ 
4 Pentanoic acid 5.11 
(g) 
6.2 
(g) 
82 (%) 
2-Valerylfuran n.sub.D.sup.25 
1.4860 
5 Isovaleric acid 5.11 6.3 83 2-Isovalerylfuran n.sub.D.sup.25 
1.4815 
6 Propionic acid 3.7 3.1 50 2-Propionylfuran n.sub.D.sup.25 
1.4908 
7 Succinic acid monoethyl ester 
7.31 7.46 76 2-(3-Ethoxycarbonyl-1-oxopropyl)furan 
6 m.p. 
52.degree. C. 
8 Benzoic acid 6.11 4.13 48 2-Benzoylfuran n.sub.D.sup.25 
1.5796 
9 Glutaric acid monomethyl ester 
7.31 7.65 78 2-(4-Methoxycarbonyl-1-oxobutyl)furan 
2 m.p. 
42.5.degree. 
C. 
10 3-Phenylpropionic acid 
7.51 8.36 83.5 2-(1-Oxo-3-phenylpropyl)furan 
n.sub.D.sup.25 
1.5633 
11 Cyclohexane carboxylic acid 
6.41 7.26 81.5 Cyclohexyl furyl ketone 
m.p. 
41.degree. C. 
12 6-Methoxyhexanoic acid 
7.31 7.9 81 2-(6-Methoxyhexanoyl)furan 
n.sub.D.sup.25 
1.5132 
13 Crotonic acid 4.31 2.66 39 2-Crotonylfuran n.sub. 
1.428725 
14 Trans-3-hexenoic acid 
5.71 8.21 83 2-(Trans-3-hexenoyl)furan 
n.sub.D.sup.25 
1.4291 
15 4-Pentynyric acid 
4.71 6.22 84 2-(4-Pentynoyl)furan 
n.sub.D.sup.25 
1.4368 
16 Stearic acid 14.2 13.5 81 2-(Octadecanoyl)furan 
n.sub.D.sup.25 
1.5144 
__________________________________________________________________________ 
EXAMPLE 17 
Reaction and post-treatment were carried out in the same manner as in 
Example 1, except that 1.0 g of boron trifluoride-acetic acid complex was 
substituent for the boron trifluoride-diethyl ether complex, to obtain 
8.53 g of 2-(7-methoxycarbonyl-1-oxoheptyl)furan. 
Yield: 80% 
b.p.: 135.degree.-137.degree. C./0.35 mmHg 
EXAMPLE 18 
Reaction and post-treatment were carried out in the same manner as in 
Example 1, except that 8.61 g (0.05 mole) of decanoic acid was substituent 
for the suberic acid monomethyl ester, to obtain 9.15 g of 
2-decanoylfuran. 
Yield: 82.4% 
n.sub.D.sup.25 : 1.4998 
EXAMPLE 19 
A four neck flask equipped with a stirrer and a thermometer was charged 
with 3.7 g (0.05 mole) of propionic acid, 5.11 g (0.0505 mole) of 
triethylamine and 60 ml of carbon tetrachloride. Thereto was added 
dropwise 5.71 g (0.0505 mole) of monochloroacetyl chloride at 0.degree. to 
5.degree. C. After completion of dropping, the reaction mixture was 
filtered under reduced pressure to remove formed hydrochloride salt of 
triethylamine. 
To the filtrate were added 5.36 g (0.065 mole) of 2-methylfuran and 0.71 g 
of boron trifluoride-diethyl ether complex and the resulting mixture was 
stirred at 50.degree. C. for 4 hours. After completion of the reaction, 
post-treatment was carried out in the same manner as in Example 3 to 
obtain 2.87 g of 2-propionyl-5-methylfuran. 
Yield: 41.5% 
n.sub.D.sup.25 : 1.5087 
EXAMPLE 20 
Reaction and post-treatment were carried out in the same manner as in 
Example 19, except that 6.51 g (0.05 mole) of heptanoic acid was 
substituent for the propionic acid, to obtain 5.95 g of 
2-heptanoyl-5-methylfuran. 
Yield: 66% 
n.sub.D.sup.25 : 1.4910 
EXAMPLE 21 
In 50 ml of toluene were dissolved 9.41 g (0.05 mole) of suberic acid 
monomethyl ester and 9.83 g (0.0575 mole) of monochloroacetic anhydride. 
To the resulting solution were added 4.43 g (0.065 mole) of furan and 0.71 
g of boron trifluoride-diethyl ether complex and the resulting mixture was 
then stirred at 50.degree. C. for 6 hours. After completion of the 
reaction, the reaction solution was cooled and washed successively with of 
water, 5% aqueous sodium carbonate solution and water. The organic layer 
was dried over anhydrous magnesium sulfate and then concentrated under 
reduced pressure and the resulting concentrated residue was purified by 
silica gel-filled column chromatography to obtain 11 g of 
2-(7-methoxycarbonyl-1-oxoheptyl)furan. 
Yield: 92.3% 
b.p.: 135.degree.-137.degree. C./0.35 mmHg. 
EXAMPLE 22 
In 50 ml of toluene were dissolved 6.51 g (0.05 mole) of heptanoic acid and 
10.26 g (0.06 mole) of monochloroacetic anhydride. To the resulting 
solution were added 4.43 g (0.065 mole) of furan and 0.71 g of boron 
trifluoride-diethyl ether complex and the resulting mixture was then 
stirred at 50.degree. C. for 5.5 hours. After completion of the reaction, 
the reaction solution was cooled and washed with 5% aqueous sodium 
carbonate solution and water in this order. The organic layer was 
concentrated under reduced pressure and the resulting concentrated residue 
was then purified by silica gel-filled column chromatography to obtain 8.2 
g of 2-heptanoylfuran. 
Yield: 91% 
n.sub.D.sup.25 : 1.4824 
EXAMPLES 23 to 32 
Reaction and post-treatment were carried out in the same manner as in 
Example 22, except that each carboxylic acid (0.05 mole) shown in Table 2 
was substituent for the heptanoic acid, to obtain results shown in Table 
2. 
In Example 27, however purification by column chromatography was not 
carried out. 
TABLE 2 
__________________________________________________________________________ 
Starting carboxylic acid 
Reaction condition 
Produced 2-acylfuran derivative 
Example Amount 
Temper- Amount Physical 
No. Name of compound 
used ature 
Time produced 
Yield Name of Compound 
properties 
__________________________________________________________________________ 
23 3-Methylbutanoic acid 
5.11 
(g) 
50 
.degree.(C.) 
5 (hrs) 
6.74 
(g) 
88.6 
(%) 
2-Isovalerylfuran 
n.sub.D.sup.27.8 
1.4803 
24 n-Pentanoic acid 
5.11 50 5 6.76 88.8 2-Valerylfuran 
n.sub.D.sup.28 
1.4865 
25 2-Methylpropionic acid 
4.41 40 8 5.6 81.1 2-Isobutyrylfuran 
n.sub.D.sup.28 
1.4870 
26 Propionic acid 
3.7 60 3 3.29 53 2-Propionylfuran 
n.sub.D.sup.28 
1.4942 
27 Succinic acid 
8.21 50 6 7.86 80.1 2-(3-Methoxycarbonyl-1- 
m.p. 
51.6.degree. 
C. 
monoethyl acid oxopropyl)furan 
28 Benzoic acid 
6.11 50 8.5 4.13 48 2-Benzoylfuran 
n.sub.D.sup.28 
1.5799 
29 Glutaric acid 
7.31 50 6 8.07 82.3 2-(4-Methoxycarbonyl-1- 
m.p. 
42.8.degree. 
C. 
monomethyl ester oxobutyl)furan 
30 Cyclohexane carboxylic acid 
6.41 50 6 7.75 87 Cyclohexyl furyl 
m.p.ne 
41.degree. C. 
31 n-Butyric acid 
4.41 50 6 4.07 58.9 2-Butyrylfuran 
n.sub.D.sup.27.8 
1.4598 
32 3-Phenylpropionic acid 
7.51 50 6 9.06 90.5 2-(1-oxo-3-phenylpropyl) 
n.sub.D.sup.26.2 
1.5636 
furan 
__________________________________________________________________________ 
EXAMPLE 33 
In 50 ml of toluene were dissolved 3.7 g (0.05 mole) of propionic acid and 
10.26 g (0.06 mole) of monochloroacetic anhydride. To the resulting 
solution were added 5.36 g (0.065 mole) of 2-methylfuran and 0.71 g of 
boron trifluoride-diethyl ether complex and the resulting mixture was then 
stirred at 50.degree. C. for 7 hours. After completion of the reaction, 
the reaction solution was cooled and washed successively with 5% aqueous 
sodium carbonate solution and water. The organic layer was concentrated 
under reduced pressure and the resulting concentrated residue was then 
purified by silica gel-filled column chromatography to obtain 2.96 g of 
2-propionylfuran. 
Yield: 42.8% 
n.sub.D.sup.25 : 1.5078 
EXAMPLE 34 
In 50 ml of toluene were dissolved 6.51 g (0.05 mole) of heptanoic acid and 
10.26 g (0.06 mole) of monochloroacetic anhydride. To the resulting 
solution were added 5.34 g (0.065 mole) of 2-methylfuran and 0.71 g of 
boron trifluoride-diethyl ether complex and the resulting mixture was then 
stirred at 50.degree. C. for 5.5 hours. After completion of the reaction, 
the reaction solution was cooled and washed successively with 5% aqueous 
sodium carbonate solution and water. The organic layer was concentrated 
under reduced pressure and the resulting concentrated residue was then 
purified by silica gel-filled column chromatography to obtain 6.27 g of 
2-heptanoyl-5-methylfuran. 
Yield: 69.6% 
n.sub.D.sup.25 : 1.4900 
EXAMPLE 35 
In 50 ml of toluene were dissolved 6.51 g (0.05 mole) of heptanoic acid, 
4.43 g (0.065 mole) of furan and 14.39 g (0.06 mole) of dichloroacetic 
anhydride. To the resulting solution was added 0.71 g of boron 
trifluoridediethyl ether coplex and the resulting mixture was then stirred 
at 50.degree. C. for 3 hours. After completion of the reaction, the 
reaction solution was cooled and washed successively with 5% aqueous 
sodium carbonate solution and water. The organic layer was concentrated 
under reduced pressure and the resulting concentrated residue was then 
purified by silica gel-filled column chromatography to obtain 8.95 g of 
2-heptanoylfuran. 
Yield: 99.3% 
n.sub.D.sup.25 : 1.4823 
EXAMPLE 36 
In 50 ml of toluene were dissolved 7.31 g (0.05 mole) of monomethylglutaric 
acid, 4.43 g (0.085 mole) of furan and 14.39 g (0.06 mole) of 
dichloroacetic anhydride. To the resulting solution was added 0.71 g of 
boron trifluoride-diethyl ether complex and the resulting mixture was then 
stirred at 50.degree. C. for 3 hours. After completion of the reaction, 
the reaction solution was cooled and washed successively with 5% aqueous 
sodium carbonate solution and water. The organic layer was concentrated 
under reduced pressure and the resulting concentrated residue was then 
purified by silica gel-filled column chromatography to obtain 9.54 g of 
2-(4-methoxycarbonylbutyryl)furan. 
Yield: 94.5% 
m.p.: 42.5.degree. C. 
EXAMPLE 37 
In 50 ml of toluene were dissolved 4.41 g (0.05 mole) of isobutyric acid, 
5.34 g (0.065 mole) of 2-methylfuran and 14.39 g (0.06 mole) of 
dichloroacetic anhydride. To the resulting solution was added 0.71 g of 
boron trifluoride-diethyl ether complex and the resulting mixture was then 
stirred at 50.degree. C. for 3 hours. After completion of the reaction, 
the reaction solution was cooled and washed successively with 5% aqueous 
sodium carbonate solution and water. The organic layer was concentrated 
under reduced pressure and the resulting concentrated residue was then 
purified by silica gel-filled column chromatography to obtain 6.74 g of 
2-isobutyryl-5-methylfuran. 
Yield: 88.6% 
n.sub.D.sup.25 : 1.4939 
EXAMPLE 38 
In 50 ml of toluene were dissolved 7.31 g (0.05 mole) of 6-methoxyhexanoic 
acid, 4.43 g (0.065 mole) of furan and 14.39 g (0.06 mole) of 
dichloroacetic anhydride. To the resulting solution was added 0.71 g of 
boron trifluoride-diethyl ether complex and the resulting mixture was then 
stirred at 50.degree. C. for 3 hours. After completion of the reaction, 
the reaction solution was cooled and washed successively with 5% aqueous 
sodium carbonate solution and water. The organic layer was concentrated 
under reduced pressure and the resulting concentrated residue was then 
purified by silica gel-filled column chromatography to obtain 8.83 g of 
2-(6-methoxyhexanoyl)furan. 
Yield: 90% 
n.sub.D.sup.25 : 1.5132 
EXAMPLE 39 
In 50 ml of toluene were dissolved 4.31 g (0.05 mole) of crotonic acid, 
4.43 g (0.065 mole) of furan and 10.26 g (0.06 mole) of monochloroacetic 
anhydride. To the resulting solution was added 0.71 g of boron 
trifluoridediethyl ether complex and the resulting mixture was then 
stirred at 50.degree. C. for 6.5 hours. After completion of the reaction, 
the reaction solution was cooled and washed successively with water, 5% 
aqueous sodium carbonate solution and water. The organic layer was 
concentrated under reduced pressure and the resulting concentrated residue 
was then purified by silica gel-filled column chromatography to obtain 2.8 
g of 2-crotonylfuran. 
Yield: 41.1% 
n.sub.D.sup.25 : 1.4283 
EXAMPLE 40 
In 50 ml of toluene were dissolved 9.41 g (0.05 mole) of suberic acid 
monomethyl ester and 9.83 g (0.0575 mole) of monochloroacetic anhydride. 
To the resulting solution were added 4.43 g (0.065 mole) of furan and 1.0 
g of boron trifluoride-acetic acid complex and the resulting mixture was 
then stirred at 60.degree. C. for 3 hours. After completion of the 
reaction, the reaction solution was cooled and washed successively with 5% 
aqueous sodium carbonate solution and water. The organic layer was 
concentrated under reduced pressure and the resulting concentrated residue 
was then purified by silica gel-filled column chromatography to obtain 
10.1 g of 2-(7-methoxycarbonyl-1-oxoheptyl)furan. 
Yield 85%. 
b.p.: 135.degree.-137.degree. C./0.35 mmHg. 
EXAMPLES 41 to 44 
Reaction and post-treatment were carried out in the same manner as in 
Example 40, except that each carboxylic acid (0.05 mole) shown in Table 3 
was substituent for the suberic acid monomethyl ester, to obtain results 
shown in Table 3. 
TABLE 3 
__________________________________________________________________________ 
Starting carboxylic acid 
Produced 2-acylfuran derivative 
Example Amount 
Amount Physical 
No. Name of compound 
used produced 
Yield Name of compound 
properties 
__________________________________________________________________________ 
41 4-Pentynoic acid 
4.9 
(g) 
6.5 
(g) 
88 (%) 
2-(4-Pentynoyl)furan 
n.sub.D.sup.25 1.4356 
42 Trans-3-hexonoic acid 
5.7 6.57 80 2-(Trans-3-hexenoyl)furan 
n.sub.D.sup.25 1.4308 
43 Decanoic acid 
8.6 10.55 
95 2-Decanoylfuran 
n.sub.D.sup.25 1.4986 
44 Stearic acid 
14.2 15.2 91.3 2-Octadecanoylfuran 
n.sub.D.sup.25 
__________________________________________________________________________ 
1.5146