JPH01228931A - Method for increasing carbon number of aromatic acetal - Google Patents

Abstract

PURPOSE:To obtain a beta-alkoxyketone or an acetal derivative thereof in high yield for a short time by reacting an aromatic acetal with an enol alkyl ether using an electrolytic acid having high activity as an acid catalyst. CONSTITUTION:An aromatic acetal (e.g., benzaldehyde dimethyl acetal) expressed by formula I (R<1> is H, halogen, alkoxy or bydrocarbon; R<2> is hydrocarbon or two groups R<2> may form a ring) is reacted with an enol alkyl ether (e.g., 1-methory-1-cyclohexene) expressed by formula II (R<3> and R<4> are H or hydrocarbon; R<5> is hydrocarbon or R<3> and R<5> may form a ring) in the presence of a reaction catalyst (especially preferably a cathodic electrolyte obtained by dissolving sodium hexafluorophosphite in acetonitrile) in a solvent (especially preferably the acetonitrile) to afford the aimed beta-alkoxyketone or acetal derivative thereof [e.g., 2-(1-methoxy-1-phenylmethyl)cyclohexanone].

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for increasing the carbon content of aromatic acetal. More specifically, the present invention relates to a method for obtaining a β-alkoxyketone or its acetal by an aldol reaction between an aromatic acetal and an enol alkyl ether using an acid produced by electrolysis (hereinafter referred to as an electrolytic acid) as a reaction catalyst.

[Conventional technology and its problems]

The method of carbonizing acetal to obtain β-alkoxyketones and their acetal forms, which are used as raw materials for α,β-unsaturated carbonyl compounds and cinnamic aldehyde derivatives used in soaps and food flavorings, is as follows: Various aldol reactions are known, and examples of the aldol reaction include (1) Aldol reaction between acetal and lithium enolate (11,0° House et al., Journal of the American Chemical Society (J, Am. , Chcv, Soc, ), 95°33
10 (1973), ); ■ Aldol reaction of acetal and enol silyl ether under various acid catalysts (T, M
ukalyamara, J, Am, Ches, S
oc, 96.7503 (1974): T, Muka
iyama et al. Chemistry Meeting Stars (Chem, L
ett, ), 1984.1759; R, Noyori
et al., J. Am.

Ches, Soc, 102.3240 (1980),
) ; ■ Aldol reaction between acetal and enol alkyl ether under various acid catalysts (R, 1, Hoagli
n et al., J. Am.

Ches, Soc, 71.3488 (1940);
S., M., Markln et al., zh.

Org, Khim, 10.2044 (1974)
O, 15ler et al., Advanced Organic Chemistry (Adv.

Org, Chem, ), 14.115 (1963); D
, Fishsan et al., Synthesis (5ynthes1s
), 19g1, 137:T, Mukalyama
.

Chew, Lett, 1987.1051).

However, in method (1), lithium enolate is an unstable and expensive substance that is dangerous to handle, and there are also problems in that self-condensation products and the like are produced as by-products. The method (2) has problems in that the enol silyl ether is expensive and uneconomical, and the acid catalysts used are often expensive and unstable. In addition, the method (2) above has the requirements to carry out the carbonization reaction of acetal economically, but when using ferric chloride or boron trifluoride ether as an acid catalyst to increase the yield of the product, the In order to increase the yield of the product, the acetal must be used in an amount three times the amount required for the enol alkyl ether, and when the acid catalyst is trimethyl perchlorate, the reaction time is 1 to 12 hours. , there are problems such as it takes a long time.

Therefore, the present inventors focused on the practicality of the aldol reaction between acetal and enol alkyl ether mentioned above, and as a result of intensive research, we found that the problem lies in the acid catalyst, and we used an electrolytic acid with high activity as an acid catalyst. It has been found that all such problems can be solved when used, and the present invention has been completed.

[Means to solve the problem]

That is, the present invention is based on the general formula (■: (wherein, R1 is a hydrogen atom, a halogen atom, a carbon number of 1 to 5
an alkoxyl group or a hydrocarbon group having 1 to 10 carbon atoms,
R2 is a hydrocarbon group having 1 to 10 carbon atoms, and R2 may bond to each other to form a ring) and an aromatic acetal represented by the general formula (): % formula % [) (in the formula, R1 and hydrogen atom or carbon number 1-10
(R5 is a hydrocarbon group having 1 to 10 carbon atoms and may be combined with R3 to form a ring) is reacted in a solvent in the presence of a reaction catalyst. The present invention relates to a method for increasing the carbon content of aromatic acetal, which is characterized by the following.

[Function and Examples]

In the present invention, general formula (II).

(In the formula, R1 is a hydrogen atom, a halogen atom, and has 1 to 5 carbon atoms.
an alkoxyl group or a hydrocarbon group having 1 to 10 carbon atoms,
The aromatic acetal represented by R2 is a hydrocarbon group having 1 to 10 carbon atoms, and R2 may be bonded to each other to form a ring, is represented by the general formula ([V)].

CHR3-CR4-OR5([V) (wherein, R3 and R4 are hydrogen atoms or have 1 to 1 carbon atoms
0 hydrocarbon group, R5 is a hydrocarbon group having 1 to 10 carbon atoms, and may be combined with R3 to form a ring) by reacting with an enol alkyl ether represented by Coal is increased.

In the aromatic acetal represented by the general formula (5), R1 is a hydrogen atom, a halogen atom, an alkoxyl group having 1 to 5 carbon atoms, or a hydrocarbon group having 1 to 10 carbon atoms. The halogen atom includes a fluorine atom, a chlorine atom,
Examples include bromine atom and iodine atom. Among these, chlorine atom, bromine atom or iodine atom is preferred. Specific examples of the hydrocarbon group having 1 to 10 carbon atoms include linear or branched alkyl groups having 1 to 10 carbon atoms. Specific examples of R2 include, for example, straight-chain or branched alkyl groups having 1 to 10 carbon atoms which may be bonded to each other to form a ring; Examples of aromatic acetals include compounds represented by the following formula. In this case, the general formula M
Among them, R6 is preferably a linear or branched alkylene group having 2 to 10 carbon atoms.

Specific examples of the aromatic acecool include benzaldehyde, para-1-butylbenzaldehyde, anisaldehyde, para-chlorobenzaldehyde, para-bromobenzaldehyde, para-iodobenzaldehyde, para-cyanobenzaldehyde, and para-nitrobenzaldehyde. Examples include dimethyl or diethyl acetal.

In the enol alkyl ether represented by the general formula N, R3 and - are hydrogen atoms or have 1 to 10 carbon atoms.
Specific examples of such hydrocarbon groups having 1 to 10 carbon atoms include linear or branched alkyl groups having 1 to 10 carbon atoms. Also
R5 is a hydrocarbon group having 1 to 10 carbon atoms and may be bonded with R3 to form a ring. Specific examples of such groups include linear or branched hydrocarbon groups having 1 to 10 carbon atoms. An example is the alkyl group of lO.

Specific examples of the enol alkyl ether include l-methoxy-1-cyclohexene, -methoxy-1-cyclopentene, l-methoxy-1-cyclododecene, 1-methoxy-1-cyclopentadecene, 3.4
-dihydro-2H-pyran, 3,4-dihydro-4-methyl-211-pyran, 2,3-dihydrofuran, ethyl vinyl ether, butyl vinyl ether, 2-methoxypropene and the like.

An electrolytic acid is used as the reaction catalyst. Such an electrolytic acid can be prepared to have the most suitable catalytic activity for the reaction between an aromatic acetal and an enol alkyl ether by changing the type of medium and supporting electrolyte used when preparing the electrolytic acid. .

To give an example of a method for preparing such an electrolytic acid, for example, the prepared medium and supporting electrolyte are placed in a glass H-type separation electrolytic cell having a glass filter as a diaphragm, and then this is electrolyzed to transfer the electrolytic acid to the anode. An example of this method is to generate it indoors.

The electrolytic conditions for preparing the electrolytic acid are as follows.

That is, common electrode materials such as platinum, stainless steel, carbon, and lead are used for the electrodes. Among these electrode materials, platinum and carbon are particularly preferably used. Examples of the medium include aprotic solvents such as acetonitrile, benzonitrile, dimethylformamide, and dimethyl sulfoxide, and among these, acetonitrile is particularly preferably used. Supporting electrolytes include, for example, perchlorates such as lithium perchlorate, sodium perchlorate, and tetrabutylammonium perchlorate; lithium tetrafluoroborate, sodium hexafluorophosphate, and sodium hexafluoroantimonate. Among these, perchlorate or sodium hexafluoroantimonate are particularly preferred in terms of obtaining the target compound in high yield.

The amount of the supporting electrolyte to be used varies depending on the type of supporting electrolyte, so it cannot be determined unconditionally.
Usually, it is preferable that the amount of the layer is 0.1 to 101%, especially 1 to 5 m5 ol per 10 ml of the medium. If the amount of supporting electrolyte used is less than 0.1 svo1, it tends to be difficult to conduct electricity;
ol, the supporting electrolyte may precipitate beyond the saturation state, depending on the solubility of the supporting electrolyte in the medium.

Next, electricity is applied to the medium in which the supporting electrolyte is dissolved, and it is preferable that a voltage of 1 to 20 V is usually applied between the anode and cathode terminals. If this voltage is lower than IV, the supporting electrolyte will not be electrolyzed, and if it exceeds 20 V, the efficiency of electrolysis tends to decrease. There is no particular limitation on the energization time, and usually the amount of electricity after energization is 0.1 to 2. It is adjusted to be OF/■o1. If the amount of electricity is less than 1,0F/so1, the yield tends to decrease, and if it exceeds 2,0F/mol, the amount of electricity tends to be wasted. Among the electrolytes thus obtained, the anolyte is used as the electrolytic acid in the present invention.

The reaction between the aromatic acetal and the enol alkyl ether is carried out by an aldol reaction, in which an electrolytic acid is used as a reaction catalyst.

The enol alkyl ether acts as a nucleophilic group during the reaction with the aromatic acetal. The amount of enol alkyl ether used is preferably 0.5 to 5 equivalents, more preferably 1.0 to 1.5 equivalents, per equivalent of aromatic acetal. If the amount of enol alkyl ether used is less than 0.5 molar equivalent, a large amount of unreacted aromatic acetal tends to remain, and if it exceeds 5 equivalents, a large amount of unreacted enol alkyl ether tends to remain. Ether tends to remain.

The amount of the electrolytic acid used is preferably 0.01-0.5 mol, more preferably 0.05-0.2 mol, per 1 mol of aromatic acetal. If the amount of electrolytic acid used is less than 0.01 mol, the reaction rate tends to decrease, and if it exceeds 0.5 mol, no reaction can be achieved even if more electrolytic acid is used. There is a tendency for the rate of improvement to become less noticeable.

The reaction between the aromatic acetal and the enol alkyl ether is carried out by adding a predetermined amount of the aromatic acetal, enol alkyl ether, and electrolytic acid to a solvent such as methylene chloride, 1°2-dichloroethane, or chloroform.

The amount (volume) of the solvent used is 1 to 2 per acetal.
0 times amount, preferably 2 to 10 times amount. If the amount of such a solvent used is less than 1 times the amount, the yield tends to decrease, and if it exceeds 20 times the amount, it tends to cause a decrease in production efficiency.

In addition, during the reaction, the temperature of the reaction solution is controlled to 1100 - 100℃ using, for example, liquid nitrogen, dry ice, a refrigerator, etc.
◆It is preferable to adjust the temperature so that the temperature is 20°C and the temperature is <-80 to -30°C. If the temperature is lower than -100°C, a large amount of energy is required for cooling, and if it is higher than +20°C, it tends to cause an increase in by-products.

Next, by adding, for example, a saturated aqueous sodium bicarbonate solution to the reaction solution, the electrolytic acid remaining in the reaction solution is neutralized and the reaction is stopped. In addition, the reaction time is
Although it is preferable to adjust the time as appropriate depending on the amount of the desired product, it is usually 5 to 60 minutes.

The crude product thus obtained is purified by column chromatography (silica gel packing) or distillation and is purified by general formula (III): (wherein R1, R2, R3, R4 and R5 are the same as above) or general formula (1) : A compound represented by the formula % (wherein R2, R3 and R4 are the same as above) can be used.

By the way, in the present invention, when the compound represented by general formula (1) is used, 3.
4-dihydro-211-pyran, 3,4-dihydro-4
-Methyl-211-pyran, 2,3-dihydrofuran,
Ethyl vinyl ether, butyl vinyl ether, and 2-methoxypropene are used, and when the compound represented by -general is used, the enol alkyl ether is l-methoxy-1-cyclohexene, l-methoxy-
1-cyclopentene, 1-methoxy-1-cyclododecene, and 1-methoxy-1-cyclopentadecene are used.

Next, the method for increasing the carbon content of aromatic acecool according to the present invention will be explained in more detail based on Examples, but the present invention is not limited to these Examples.

Example 1 Electrolytic acid was prepared using a glass H-type N electrolytic cell with a capacity of about 50 ml and a glass filter as a diaphragm, and sodium perchlorate 184B (1,5asol) and tetrabutylammonium perchlorate 397B. (1,5
15 ml of an acetonitrile solution in which mol) was dissolved was added to each of the anode and cathode chambers. Platinum plates (surface area 1.5cj) were used as the anode and cathode materials, and the
Electrolysis was carried out under a constant voltage of V. 1 for the amount of supporting salt in the anode chamber. Electrolysis was stopped when an amount of electricity of OF/sol was applied.

The obtained anolyte was transferred to an ampoule and stored.

Next, 153mg of benzaldehyde dimethyl acetal
(1,0 m5 ol) and 1-methoxy-1-cyclohexene 169B (1,5 w5 ol) were weighed into a dry reactor, and 3 ml of dry methylene chloride was added thereto to dissolve liquid nitrogen and ethanol in a nitrogen atmosphere. using 178
Cooled to ℃. 1 ml of anolyte (electrolytic acid) was added to this solution and stirred for 20 minutes. After the reaction is completed, the reaction solution is injected into a saturated aqueous sodium bicarbonate solution to neutralize the remaining electrolytic acid to stop the reaction, and the crude product is purified by column chromatography (silica gel packing).
-(1methoxy-1-phenylmethyl)cyclohexanone 207 mg (yield 95%, erythro/threo ratio 35/
65, hereinafter referred to as na).

Product 11a was confirmed by measuring its boiling point, infrared absorption spectrum, and 'IINMR spectrum. The results of these measurements are shown below.

(Boiling point) 56-48℃/0.009Torr■Erytron
a (Infrared absorption spectrum, IR (neat)) 3360
．． 3020.2920.2860.2820.1700
(C-0), 1595.1210.1175.1120
．． 1085cm+-1 (IHNMR spectrum (CDC#3) (pp-
)) 1.2-2.1 (■, 611, CH2), 2
．． 27-2.93 (i, 3H, C112CO, CtlC
O), 3.27 (S, 3H, 0CH3), 4.78 (
d, J=5Hz, LH, C11-0), 7.3(s
, 5H, CeHs) ■Threo 1la (Infrared absorption spectrum, IR (neat)) 33BO
13020, 2920, 28BO12810, lf05
(C-0), 1595.1485.1235.1225
．． 1205.1170.1085.1015cm+-1 (IHNMR spectrum (CD(Js) (pp)) 1.05-2.20 (1,8H, c 82), 2
．． 27-2.93 (m, 3H.

CH2C0, CHCO), 3.18(S, 3H, 0C
H3), 4.55 (d.

J-911z, LH, cH-0), 7.25(s, 5
H, Cs Hs) Example 2 The preparation of electrolytic acid was carried out using the same capacitive 50% as used in Example 1.
Using an H-type separation electrolytic cell of 1 ml, 255 g (1.5 saol) of sodium hexafluorophosphate was added to it.
) of acetonitrile solution to each anode and cathode chamber.
One by one was added. Both electrodes are platinum plates (surface area:
1.5cj), electrolysis was carried out under a constant voltage of 20V at room temperature. For the supporting salt in the anode chamber, QF/
Electrolysis was stopped when the amount of electricity @ol was applied.

Next, benzaldehyde dimethyl acetal 153B (
1,0 saol) and 189 g (1,5 smol) of 1-methoxy-1-cyclohexene were weighed into a dry reactor, 3 ml of dry methylene chloride was added thereto, and liquid nitrogen and ethanol were added in a nitrogen atmosphere. -78℃ using
It was cooled to 1 ml of anolyte solution ('@electrolytic acid) was added to this solution, and the reaction was carried out for 20 minutes. After the reaction was completed, the remaining electrolytic acid was neutralized by injecting the reaction solution into a saturated aqueous sodium bicarbonate solution, and the reaction was carried out. The crude product was purified by column chromatography (silica gel packing) to give 95 g of 2-(1-methoxy-1-phenylmethyl)cyclohexanone (yield 44%, erythrol threo ratio 47/53). ) was obtained.

Product boiling point, infrared absorption spectrum and 1HNMR
When the spectrum was measured, it was the same as the product na obtained in Example 1.

Example 3 Benzaldehyde dimethyl acetal 153 mg (1,
0-sol) and 3,4-dihydro-2H-pyran 125
B (1,5-ol) was placed in a dry reactor, 3 ml of dry methylene chloride was added thereto, and the mixture was cooled to -78°C using liquid nitrogen and ethanol in a nitrogen atmosphere.

Add 1 ml of the anolyte (electrolytic acid) prepared in Example 1 to this solution.
was added, and the reaction was carried out for 20 minutes. After the reaction is completed, the reaction solution is injected into a saturated aqueous sodium bicarbonate solution to neutralize the remaining electrolytic acid and stop the reaction.The crude product is purified by column chromatography (silica gel packing) to obtain 2-methoxy -3-(l-methoxy-1-
phenylmethyl)tetrahydro-2H-pyran 20Bm
g (yield 87%, hereinafter referred to as Ia) was obtained.

Next, the boiling point, infrared absorption spectrum and 'HNMR spectrum of the product 1a were measured. The results are shown below.

(Boiling point) 125°C/8.5 Torr (Infrared absorption spectrum, IR (neat)) 3060
．． 3030.2940.2g80.2820.1605
．． 1500.1470.1140.1120011-1
(IIINMR spectrum (CDC#s) (pl
) I)) 0.40-2.40 (Zen, 711.C)! −(
CI+2)3-0).

3.05 (S, 3H, CH30), 3.33 (8,3H
, CH30).

3.93 (d, J=lQHz, LH, CH-0), 4.
92 (s, LH.

CH-0), 7.17 (s, 5H, C5Hs) Example 4 Anisaldehyde dimethyl acetal 183 mg (1,
0 saol) and 2,3-dihydrofuran 105B (1,
5saol) was weighed into a dry reactor, 3i1 of dry methylene chloride was added thereto, and the mixture was cooled to 8°C using liquid nitrogen and ethanol in a nitrogen atmosphere. Add the anolyte (electrolytic acid) prepared in Example 1 to this solution.
1 was added and the reaction was carried out for 20 minutes. After the reaction is completed, the reaction solution is injected into a saturated aqueous sodium bicarbonate solution to neutralize the remaining electrolytic acid and stop the reaction.The crude product is purified by distillation to obtain 2-methoxy-3-(l-methoxy 134 mg of -1-(paramethoxyphenyl)methyl)-tetrahydrofuran (yield 53%, hereinafter referred to as !r) was obtained.

Next, the boiling point, infrared absorption spectrum and 'HNMR spectrum of the product If were measured. The results are shown below.

(Boiling point) 120°C/7.0 Torr (Infrared absorption spectrum, IR (neat)) 2920
．． 281O11740, 1700, 1625, 1595
,1520,14BO11380,1310,1185
, 1145, 1100, 1050cIl-1 ('HNMR spectrum (CD (J 3 (ppm))
1.00-2.80 (■, 511.CH-(CH2)
z-0).

3.08 (S, 311.Cl430), 3.31 (S
, 3H, Cl30).

3.73 (S, 3H, CH30).

3.88 (d, J-10Hz, II, CH-0).

5.01 (s, LH, CH-0), 6.95 (dd,
J=22.4Hz, 4H.

Cs Hs ) Example 5 Anisaldehyde dimethyl acetal 183-g (1,
Weigh out 0 mmol) and ethyl vinyl ether (mmol) into a dry reactor, and add 3 ml of dry methylene chloride to this.
was added and cooled to -78°C using liquid nitrogen and ethanol under a nitrogen atmosphere. 1 ml of the anolyte (electrolytic acid) prepared in Example 1 was added to this solution, and a reaction was carried out for 20 minutes. After the reaction is completed, the reaction solution is injected into a saturated aqueous sodium bicarbonate solution to neutralize the remaining electrolytic acid and stop the reaction, and the crude product is purified by distillation.
l-methoxy-l-ethoxy-3-methoxy-3-(paramethoxyphenyl)propane 176 mg (yield 69%
, hereinafter referred to as 11).

Next, the boiling point, infrared absorption spectrum and 'HNMR spectrum of Product 11 were measured. The results are shown below.

(Boiling point) 145°C/7.5 Torr (Infrared absorption spectrum, IR (neat)) 2980
, 2930, 2835, 1815, 1590, 1515
, 1485, 1445, 1210, 1175, 1130
, 1105, 1080 cm-1 ('HNMR spectrum (COCls) (
ppm)) 1, 20 (t.J-7Hz.3H, CD3
).

1, 98 (Q, J-7Hz.2H, OCH2).

3, 15 (S.3H.CH30), 3.30 (S.3
H. CH30).

3, 20-3.90 (1.2H.cH2), 3.7
8 (S, 3H.CH30).

3, 90-4.60 (■.2H.CI-C-CH).

7,00(dd,J-23Hz,8Hz.411.Cs
t-ta) Examples 6 to 11 In the same manner as in Example 1, the acetals shown in Table 1 were reacted with enol alkyl ether to obtain products.

[Margin below] The physical properties of the compounds obtained in each example are as follows.

(Product obtained in Example 6 2-methoxy-3-(1-
methoxy-1-(para-t-butylphenyl)methyl)
-Physical properties of tetrahydrofuran (1b>) (boiling point) 146°C/8.0 Torr (infrared absorption spectrum, IR (neat)) 2960
．． 2880.2820.1740.1B20.1510
．． 1470, 1200.1180.1130.1120
．． 1085.1060cm-1 ('HNMR spectrum (CDCjs) (ppm)
)0.50~2.15(m,7H,cH-(CH2)
s −0).

1.29(s, 9H, (CHs)3C), 3.09(
S, 3H, C) 130).

3J7 (s, 3H, C) 130), 3.91 (d, J”
1OHz, LH, Cl-0).

4.95 (s, LH, Cl-0), 8.19-7.40
(m, 4H, csHa) (Product 2 obtained in Example 7
-Methoxy-3-(1-methoxy-1-(bara-methoxyphenyl)methyl)-tetrahydropyran (I c)
physical properties) (boiling point) 135 °C/8.0 Torr (infrared absorption spectrum, IR (neat)) 2940
．． 2830.1615.1585.1515.1485
．． 1380.1360.1170.1130.1110
．． 1085 ('HNMR spectrum (CDCf s )
(ppm))0.40-2.50(1,7H,CH-
(CH2)s-0).

3.10 (S, 3H, CH30), 3.39 (S, 3H
, CH30).

3.73 (S, 3H, CH30).

3.90 (d, J=lGHz, LH, cH-0).

4.93 (s, LH, cH-0).

13.97 (dd, J-22, 8Hz, 4H, C3H4
) (product obtained in Example 8 2-methoxy-3-(1
Physical properties of -methoxy-1-phenylmethyl)-tetrahydrofuran (Id) (boiling point) 110°C/7.0 Torr (infrared absorption spectrum, IR (neat)) 3040
．． 3005.29BO12800, 1600, 1585
,1495,1455,1180,1135,1090
, 1040011-1 (lHNMR spectrum (CDC
N 3 ) (ppm)) 1.00-2.80 (1,5
H, CH-(CH2)z-0).

3.10 (S, 3H, CH30), 3.31 (S, 3H
, CH30).

3, gl(d, J-1011z, C11-0).

5.08 (s, III, C11-0), 7.22 (
s, 511. Cs Hs).

(Product obtained in Example 9 2-methoxy-3-(1-
methoxy-1-(para-1-butylphenyl)methyl)
- Physical properties of tetrahydrofuran (Iθ) (boiling point) 143°C/9.0 Torr (infrared absorption spectrum, IR (neat)) 2920
．． 281O11740, 1700, 1625, 1595
,1520,1145,l100cII-"('IIN
MR spectrum (CDCj s ) (ppm))■,
00-2.80(-,5H,C)I-(CH2)2-
0).

3.08 (s, 3H, CHsO), 3.31 (S, 3H
, CH30), 3-73 (S, 3) 1. cH30).

3.88 (d, J-1011z, LH, Cl-0).

5.01 (s, 111.Cl-0), 6.95 (m, 4
H,c@H4) (Physical properties of the product 1-ethoxy-1-methoxy-3-methoxy-3-phenylpropane (Ig) obtained in Example 1O) (Boiling point) 121°C/8.5 Torr (Infrared absorption Spectrum, IR (neat)) 3065
．． 3030.2980.2930.2825.1605
．． 1500.1455.1380.1185.1130
．． 1105.10BOcs-' (lHNMR spectrum (CDCf3) (ppll
)) 1.18 (t, J=7Hz, 3H, cH3)
.

1.98 (q, j-7) 1z, 2H, CH20).

3.13(s,3H,C)bO)- 3,20-3.80 (Zen, 2H, CH2-C).

4.15-4. [i5(dust, 2H, C1!-0, CH-
0).

7.20 (s, 5H, CsHs) (Physical properties of the product 1-ethoxy-1-methoxy-3-methoxy-3-(para-1-butylphenyl)propane (1h> obtained in Example 11) boiling point) 145°C/7.5 Torr (infrared absorption spectrum, IR (neat) 2970,
2900, 2870, 2820, 161O11510,
1460, 1410, 1370, 1175, 1110,
10800m+-'('HNMR spectrum (CDCl
3) (ppm))0.5-2.3(1,511,
cH3cH2-0).

1.30(s, 9H, (CH3)3C) ~3, OO~4
．． 80 (layers, 4+1, C11-CH2-CI).

3.17 (S, 3H, CH30), 3.38 (s, 3H
, CHsO).

7.00 to 7.50 (m, 4H, C@Ha') [Effect of the invention] As explained above, according to the carbon enrichment method of the present invention, acetal and enol alkyl β-alkoxyketone or its acetal form can be obtained from ether in a short time and in high yield.

Therefore, the carbonization method of the present invention is industrially extremely advantageous as acetal carbonization method.

Claims (1)

[Claims] 1 General formula (III): ▲There are mathematical formulas, chemical formulas, tables, etc.▼(III) (In the formula, R^1 is a hydrogen atom, a halogen atom, or a carbon number of 1 to
5 is an alkoxyl group or a hydrocarbon group having 1 to 10 carbon atoms, R^2 is a hydrocarbon group having 1 to 10 carbon atoms, and R^2 may be bonded to each other to form a ring). Aromatic acetal and general formula (IV): CHR^3=CR^4-OR^5 (IV) (wherein, R^3 and R^4 are hydrogen atoms or carbon atoms with 1
~10 hydrocarbon groups, R^5 is a hydrocarbon group having 1 to 10 carbon atoms, and may be combined with R^3 to form a ring) as a reaction catalyst in a solvent. A method for increasing the carbon content of an aromatic acetal, the method comprising reacting the aromatic acetal in the presence of. 2. The method for increasing carbonization of aromatic acetal according to claim 1, wherein the reaction catalyst is an acid generated in an electrolytic system. 3. The method for increasing carbonization of aromatic acetal according to claim 2, wherein the reaction catalyst is an anode electrolyte obtained by electrolyzing an electrolyte solution obtained by dissolving a supporting electrolyte in a medium. 4. The method for carbonizing aromatic acetal according to claim 3, wherein the medium is acetonitrile and the supporting electrolyte is sodium perchlorate and/or tetrabutylammonium perchlorate. 5. The method for carbonizing aromatic acetal according to claim 3, wherein the medium is acetonitrile and the supporting electrolyte is sodium hexafluorophosphite. 6. The method for carbonizing aromatic acetal according to claim 3, wherein the medium is acetonitrile and the supporting electrolyte is sodium hexafluoroantimonate. 7. The method for carbonizing an aromatic acetal according to claim 1, wherein the solvent is methylene chloride, 1,2-dichloroethane or chloroform.