JP2006037233A - Preparation method of 2-alkyne-1-acetal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To economically prepare 2-alkyne-1-acetal with a high selectivity and in a high product yield. <P>SOLUTION: In a preparation method of 2-alkyne-1-acetal of formula I (wherein substituents are as indicated in the patent claim), a compound of formula III (wherein R<SP>1</SP>is as indicated in formula I) is electrochemically oxidized either in the presence of a 1-6C alkyl alcohol (alcohol A) or in the form of a substance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing 2-alkyne-1-acetal.

  Non-electrochemical methods for producing 2-alkyne-acetals are known, for example, from US 2,879,305, in which case 2-alkyne-1-aldehydes are acetalized with alcohols.

  From the Journal of Electroanalytical Chemistry (1994), 371 (1-2), pages 167-177 and Electrochimica Acta (1993), 38 (10), pages 1337-1344, electrochemical methods in aqueous solutions are known. In these methods, 2-alkyn-1-ol is oxidized. However, the proper formation of acetals is not described.

From Chemische Berichte (1954), 87, 668-676 and Surface Science (2000), 457 (1-2), 178-184, DE-A1-2409117, an electrochemical method is known, In these methods, 2-alkyn-1-ol is oxidized. The corresponding aldehyde, acid or CO ₂ formation is not described here.

In an electrochemical method, saturated alcohol (methanol) (Bulletin of the Chemical Society of Japan (1991), 64 (3), pages 796-800, Journal of Organic Chemistry (1991), 56 (7), 2416 ˜2421, Synlett (1990), (1), pp. 57-58 (using mediator)) or allyl-ether-alcohol (Tetrahedron, 43, 24 (1987), pp. 5797-5806. It is known to oxidize a) to acetals.
US2879305 DE-A1-2409117 Journal of Electroanalytical Chemistry (1994), 371 (1-2), 167-177. Electrochimica Acta (1993), 38 (10), pp. 1337-1344 Chemische Berichte (1954), 87, pp. 668-676. Surface Science (2000), 457 (1-2), pp. 178-184 Bulletin of the Chemical Society of Japan (1991), 64 (3), pp. 796-800 Journal of Organic Chemistry (191), 56 (7), pp 2416-2421 Synlett (1990), (1), pp. 57-58 Tetrahedron, 43, 24 (1987), pp. 5797-5806

  The object of the present invention is therefore to provide an electrochemical process for producing economically and in particular with high product yields and high selectivities of 2-alkyne-1-acetals.

  The above object is achieved by the present invention according to the general formula I

［式中、基は次の意味を有する：Ｒ^１は水素、Ｃ_１〜Ｃ_２０−アルキル、Ｃ_２〜Ｃ_２０−アルケニル、Ｃ_２〜Ｃ_２０−アルキニル、Ｃ_３〜Ｃ_１２−シクロアルキル、Ｃ_４〜Ｃ_２０−シクロアルキル−アルキル、Ｃ_４〜Ｃ_１０−アリール、その際、これらの基は置換されていないか、またはヒドロキシ基、ハロゲン、Ｃ_１〜Ｃ_６−アルコキシ、（Ｃ_１〜Ｃ_６−アルコキシ）−カルボニル、カルボキシル基もしくはニトリル基により置換されており、Ｒ^２はＣ_１〜Ｃ_６−アルキルまたは一般式ＩＩ

[Wherein the radicals have the following meanings: R ¹ is hydrogen, C ₁ -C ₂₀ -alkyl, C ₂ -C ₂₀ -alkenyl, C ₂ -C ₂₀ -alkynyl, C ₃ -C ₁₂ -cycloalkyl, C ₄ -C ₂₀ - cycloalkyl - _alkyl, C 4 _{-C 10} - aryl, in which these groups are unsubstituted or substituted with or hydroxy group, _halogen, C 1 -C ₆ - alkoxy, _(C 1 ~ C ₆ - alkoxy) - carbonyl, it is substituted by a carboxyl group or a nitrile group, ^{R 2} is _C 1 -C ₆ - alkyl or the general formula II

（式中、Ｒ^１は上記の意味を有する）の基、Ｒ^３は基Ｒ^２と同じ意味を有する］の２−アルキン−１−アセタールの製造方法において、一般式ＩＩＩ

In the process for producing 2-alkyne-1-acetal, wherein R ¹ has the same meaning as described above, and R ³ has the same meaning as the group R ² , the general formula III

［式中、基Ｒ^１は一般式Ｉ中と同じ意味を有する］の化合物を、Ｃ_１〜Ｃ_６−アルキルアルコール（アルコールＡ）の存在下に、または物質の形で電気化学的に酸化することにより解決される。

The compound of the formula, wherein R ¹ has the same meaning as in general formula I, is electrochemically oxidized in the presence of a C ₁ -C ₆ -alkyl alcohol (alcohol A) or in the form of a substance. Is solved.

In general, compounds of general formula I are prepared in which the radicals R ² and R ³ have the same meaning.

In the case of compounds of the general formula I in which R ² is a group of the general formula II, preferably R ³ is also a group of the general formula II.

In the case of compounds of the general formula I in which R ² and R ³ are preferably radicals of the general formula II, the radical R ¹ appearing three times in the formula has the same meaning. When working in the form of a substance, ie without using alcohol A, during production, the starting compound of general formula III is responsible for the function of alcohol A in acetalizing the oxidation product of the compound of general formula III with respect to its function. Fulfill.

Particular preference is given to preparing compounds of the general formula I in which the radicals R ² and R ³ represent methyl. In this case, methanol is correspondingly used as alcohol A.

With respect to the group R ¹ , preference is given to those compounds of the general formula I which represent hydrogen, a C ₁ -C ₆ -alkyl group or a C ₁ -C ₆ -alkyl group substituted by a hydroxyl group. In that case, correspondingly compounds of the general formula II in which the radical R ¹ represents hydrogen, a C ₁ -C ₆ -alkyl group or a C ₁ -C ₆ -alkyl group substituted by a hydroxyl group use.

Particular preference is given to using compounds of the general formula I in which R ¹ represents hydrogen and the radicals R ² and R ³ represent methyl. In that case, 2-propyn-1-ol is used as the starting product as the compound of general formula III and methanol as alcohol A.

  Another compound of the general formula I which is particularly advantageously prepared is 1,1,4,4-tetramethoxybut-2-yne. In that case, 2-butyne-1,4-diol is used as the starting product as compound of general formula III and methanol is used as alcohol A.

  In the electrolyte, the alcohol A and the compound of the general formula III are generally used in a double equimolar amount relative to the alcoholic hydroxyl group contained in the compound of the formula III, or the alcohol A is used in excess. And in that case simultaneously used as a solvent or diluent for the compound of general formula III and the formed compound of general formula I.

  When using compounds of the general formula III which preferably have two or more alcoholic hydroxyl groups, in order to avoid oligomerization, more than 2 mol (advantageously) per mole of hydroxyl groups which the compound of the general formula III has 5 to 20 mol) of alcohol A is used.

  In some cases, a normal auxiliary solvent is added to the electrolyte. This is a normal, inert solvent having a high oxidation potential common in organic chemistry. Examples include dimethyl carbonate or propylene carbonate.

  In principle, water is also suitable as a cosolvent, and the proportion of water in the electrolyte is advantageously less than 20% by weight.

In general, alkali salts, tetra (C ₁ -C ₆ -alkyl) ammonium salts, preferably tri (C ₁ -C ₆ -alkyl) methylammonium salts are important as the conductive salts contained in the electrolyte It is. Sulfate, hydrogen sulfate, alkyl sulfate, aryl sulfate, halogen ion, phosphate ion, carbonate ion, alkyl phosphate ion, alkyl carbonate ion, nitrate ion, alcoholate, tetrafluoroborate ion or perchlorine as counter ion Acid ions are possible.

  Furthermore, acids derived from the above anions, such as sulfuric acid, sulfonic acid and carboxylic acid, are considered as conductive salts.

  In addition, ionic liquids are also suitable as conductive salts. Suitable ionic liquids are described in Ionic Liquids in Synthesis, Peter Wasserscheid, edited by Tom Welton, Wiley VCH Publishing, 2003, Chapters 1-3.

  The method according to the invention can be carried out in any conventional, divided or undivided type electrolysis cell. Working with an undivided once-through cell (Durchflusszellen) is advantageous.

  In particular, a bipolar-connected capillary decomposition cell (Kapillarspaltzellen) or a flat-plate stacked cell (Plattenstapelzellen) in which electrodes are configured as a flat plate and arranged in a parallel plate shape is preferred (Ullmann's Encyclopedia of Industrial Chemistry, 1999). , Electronic Edition, 6th Edition, VCH Publishing, Weinheim, Volume Electrochemistry, Chapter 3.5, special cell designs and Chapter 5, Organic Electrochemistry, Chapter 5.3.2.2, Cell Design) . Graphite is advantageous as the electrode material.

  In carrying out the process continuously, the feed rates of the substances used are generally determined by the mass ratio of the compound of general formula II used to the compound of general formula I formed in the electrolyte from 10: 1 to 0.05. : 1.

The current density at which the process is carried out is generally 1-1000 mA / cm ² , preferably 10-100 mA / cm ² . In general, it operates at standard pressure. When operating at higher temperatures, higher pressures are advantageously applied to avoid boiling of the starting compound or solvent.

Suitable anode materials are, for example, noble metals such as platinum or metal oxides such as ruthenium oxide or chromium oxide or mixed oxides of the RuO _x TiO _x type and diamond electrodes. A graphite or carbon electrode is preferred.

  Possible cathode materials are, for example, iron, steel, special steel, nickel or noble metals, such as platinum and graphite or carbon materials and diamond electrodes. Preference is given to systems of graphite as anode and cathode and systems of graphite, anode and nickel, special steel or steel as cathode.

  After completion of the reaction, the electrolytic solution is worked up by a general separation method. For this purpose, the electrolyte is generally first distilled and the individual compounds are recovered separately in the form of various fractions. Further purification can be achieved, for example by crystallization, extraction, distillation or chromatography.

  Example 1

Example for undivided driving methods:
An undivided flat laminate cell with a graphite anode and a steel cathode was used. 160 g of 2-propyn-1-ol was reacted in 640 g of methanol with 5.3 g of sulfuric acid at a temperature of 20 ° C. within 19 hours. The electrolysis was carried out at 3.4 A / dm ² and a 2F charge was passed through the cell for the 2-propyn-1-ol used. 8.8 GC area% of 1,1-dimethoxy-2-propyne was obtained in the electrolytic discharge (reaction rate 49%, yield 30%).

  Example 2

Example for split driving:
A split parallel plate cell (Parallelplatenzelle) with a graphite anode and a steel cathode was used. In 1400 g of methanol, 401 g of 2-propynol and 38 g of MTBS (methyltributylammonium methyl sulfate) were reacted in the anode chamber and 941 g of methanol and 24 g of MTBS in the cathode chamber at a temperature of 20 ° C. within 38 hours. Electrolysis was performed at 3.1 A / dm ² and a 2F charge was passed through the cell for the 2-propyn-1-ol used. In the anolyte, 8.3 GC area% of 1,1-dimethoxy-2-propion was obtained (reaction rate 91%, yield 19%).

  Example 3

Example for a split driving method:
A segmented parallel plate cell with a graphite anode and a steel cathode was used. 13 g of 2-butyne-1,4-diol and 3.8 g of MTBS (methyltributylammonium methylsulfate) in 117 g of methanol in the anode chamber and 130 g of methanol and 3.8 g of MTBS in the cathode chamber at a temperature of 19 ° C. The reaction was carried out within 14 hours. The electrolysis was performed at 3.4 A / dm ² and a 4F charge was passed through the cell for the 2-butyne-1,4-diol used. After electrolysis, the anolyte and catholyte are combined, and the reaction rate is 100%, 53% 1,1-dimethoxy-2-butyn-4-ol and 1,1,4,4-tetramethoxy-2-butyne A yield of 20% was obtained (according to GC area%).

Claims (7)

Formula I

[Wherein the radicals have the following meanings: R ¹ is hydrogen, C ₁ -C ₂₀ -alkyl, C ₂ -C ₂₀ -alkenyl, C ₂ -C ₂₀ -alkynyl, C ₃ -C ₁₂ -cycloalkyl, C ₄ -C ₂₀ - cycloalkyl - _alkyl, C 4 _{-C 10} - aryl, in which these groups are unsubstituted or substituted with or hydroxy group, _halogen, C 1 -C ₆ - alkoxy, _(C 1 ~ C ₆ - alkoxy) - carbonyl, it is substituted by a carboxyl group or a nitrile group, ^{R 2} is _C 1 -C ₆ - alkyl or the general formula II

In the process for producing 2-alkyne-1-acetal, wherein R ¹ has the same meaning as described above, and R ³ has the same meaning as the group R ² , the general formula III

The compound of the formula, wherein R ¹ has the same meaning as in general formula I, is electrochemically oxidized in the presence of a C ₁ -C ₆ -alkyl alcohol (alcohol A) or in the form of a substance. A process for producing 2-alkyne-1-acetal, which is characterized in that   The process according to claim 1, wherein 2-propyn-1-ol or 2-butyne-1,4-diol is used as the compound of general formula III and methanol is used as alcohol A.   The process according to claim 1 or 2, wherein the process is carried out in an electrolyte containing sulfuric acid, sulfonic acid or carboxylic acid.   The process according to claim 1, wherein the process is carried out in an electrolyte containing less than 20% by weight of water. As conductive salts, sulfate ion, hydrogen sulfate ion, alkyl sulfate ion, aryl sulfate ion, halogen ion, phosphate ion, carbonate ion, alkyl phosphate ion, alkyl carbonate ion, nitrate ion, alcoholate, tetrafluoroborate ion Or containing one or more compounds selected from the group of sodium-, potassium-, lithium-, iron-, tetra (C ₁ -C ₆ -alkyl) ammonium salts having a perchlorate ion as a counter ion The process according to claim 1, wherein the process is carried out in an electrolyte containing an ionic liquid.   6. The process as claimed in claim 1, wherein the process is carried out in a bipolar dissociated capillary decomposition cell or plate stack cell or in a divided electrolysis cell.   When using a compound of general formula III having two or more alcoholic hydroxyl groups, at least 2 mol (preferably 5-20 mol) of alcohol A is used per mol of hydroxyl group of the compound of general formula III. The method according to any one of claims 1 to 6.