WO2021213663A1

WO2021213663A1 - Process for preparing aldehydes from 1,3,5 trioxanes

Info

Publication number: WO2021213663A1
Application number: PCT/EP2020/061379
Authority: WO
Inventors: Elke Fritz-Langhals
Original assignee: Wacker Chemie Ag
Priority date: 2020-04-23
Filing date: 2020-04-23
Publication date: 2021-10-28

Abstract

The invention relates to a process for preparing aldehydes, characterized in that at least one 1,3,5 trioxane of the general formula (I) is reacted to the corresponding aldehyde(s) of the general formula (II) in the presence of at least one cationic silicon and/or germanium compound as the catalyst.

Description

Process for the preparation of aldehydes from 1,3,5-trioxanes

The invention relates to a novel process for the preparation of aldehydes from 1,3,5-trioxanes in the presence of at least one cationic silicon and / or germanium compound as a catalyst.

Aldehydes are a technically important class of compounds. They are used, for example, for the production of polymers, as disinfectants, as tanning agents and as reducing or oxidizing agents. Aldehydes are highly reactive compounds with a limited shelf life. Formaldehyde, for example, can spontaneously decompose explosively in concentrated form, which is why the aqueous solution in which formaldehyde is present as a hydrate, the so-called formalin solution, is used as a storage form. Acetaldehyde must be stored in a cool place, as it already boils at 20 ° C and forms explosive vapor-air mixtures. Due to its very low ignition point of 140 ° C, it can ignite on hot surfaces, which represents a high safety risk. In addition, acetaldehyde condenses very easily to form aldol addition products during storage.

Because of the problems outlined, a stable storage form for aldehydes is of technical interest from which aldehydes can be liberated in a simple manner and without the formation of cleavage products. Suitable storage forms for aldehydes are the corresponding cyclotrimeric products, the 1,3,5-trioxanes, which have a very low reactivity and thus a very good shelf life. For example, trioxymethylene, the cyclotrimeric form of formaldehyde, is a very stable crystalline compound with a boiling point of 114.5 ° C. Paraldehyde, the cyclotrimer of acetaldehyde, boils at 124 ° C. The conversion of 1,3,5-trioxanes into aldehydes does not take place spontaneously, but requires a catalyst. Known catalysts are sulfuric acid or p-toluenesulphonic acid, which, however, are used in large quantities. In Chem. Eur. J.

2013, 19, 10814 describes, for example, the in situ generation of acetaldehyde from paraldehyde with 10 mol% p-toluenesulfonic acid.

When using strong Brønsted acids such as sulfuric acid or p-toluenesulfonic acid, however, there is a risk of acid-catalyzed aldol condensation, which leads to a reduction in product purity. There is also the risk that large proportions of strong acid make the desired subsequent reaction of the aldehyde more difficult or impossible and lead to the formation of by-products.

The object of the present invention is therefore to provide a simple and selective process for the preparation of aldehydes from

1.3.5-trioxanes to be provided.

It has now been found that 1,3,5-trioxanes can be converted very efficiently into the corresponding aldehydes in the presence of cationic silicon and / or germanium compounds as catalysts. The reaction proceeds very selectively under simple reaction conditions and no by-products, such as products of

Aldol condensation reactions found. The aldehydes formed are stable under the conditions.

An object of the invention is a process for the preparation of aldehydes, characterized in that at least one

1.3.5-trioxane of the general formula (I)

wherein the radicals R ^{x are} independently selected from the group consisting of (i) hydrogen and (ii) unsubstituted C ₁ -C ₄₀ -hydrocarbon radical, in the presence of at least one cationic silicon and / or germanium compound as a catalyst for the corresponding Aldehyde (s) of the general formula (II) is implemented

R ^x -CHO (II), in which the radicals R ^x correspond to the radicals R ^x from formula (I).

1,3,5-trioxane (I) or aldehyde (II)

Since the aldehydes formed arise from the 1,3,5-trioxane, the radicals R ^x in formula (II ^{) match the radicals R x} in formula (I). Depending on the choice of the radicals R ^x in formula (I), identical or different aldehydes of the formula (II) are thus formed.

The radicals R ^x in formula (I) are selected independently of one another from the group consisting of (i) hydrogen and (ii) unsubstituted Ci-C4o hydrocarbon radical. The radicals R ^x are preferably selected independently of one another from the group consisting of (i) hydrogen, (ii) methyl radical and (iii) unsubstituted, saturated or unsaturated C ₂ -C ₂₀ hydrocarbon radical; the radicals R ^{x are particularly preferred} independently selected from the group consisting of (i) hydrogen and (ii) methyl radical.

Catalyst The cationic silicon and / or germanium compound is preferably selected from the group consisting of cationic silicon (II), silicon (IV), germanium (II) and / or germanium (IV) compounds; the cationic compound is particularly preferred Silicon and / or germanium compounds selected from the group consisting of (i) silicon (II) and

Germanium (II) compounds of the general formula (III)

([M (II) Cp] ⁺ ) _a X ^a- (III), in which M is selected from germanium or silicon, and Cp is an n-bonded cyclopentadienyl radical of the general formula (purple)

in which the radicals R ^{Y are} independently selected from the group consisting of (i) triorganosilyl radical of the formula - SiR ^b 3, in which the radicals R ^{b are} independently C ₁ -C ₂₀ hydrocarbon radical, (ii) hydrogen, (iii) unsubstituted or substituted C ₁ -C ₂₀ - hydrocarbon radical, and (iv) unsubstituted or substituted C ₁ -C ₂₀ ^_ hydrocarbyloxy group, it also being possible in each case two radicals R ^{Y represents} a monocyclic or polycyclic C ₂ -C may form ₂₀ ^_ hydrocarbon radical with each other, and where substituted means in each case that at least one C atom in the hydrocarbon or hydrocarbonoxy radical can also be replaced by a Si atom,

X ^a- denotes an a-valent anion and a can assume the values 1, 2 or 3; and (ii) silicon (IV) and germanium (IV) compounds of the general formula (IV)

wherein the radicals R ^Y are selected independently of one another from the group consisting of (i) hydrogen and (ii) C ₁ -C ₅₀ hydrocarbon radical; and in which the radicals Z are independently selected from silicon (IV) or germanium (IV); and in which the radical Y denotes _{a divalent C 2} -C _{50 hydrocarbon radical;} and in which the subscript a takes on the values 1, 2 or 3; and in which X ^{a_ is} an a-valent anion.

At least one cationic silicon and / or germanium compound is used as a catalyst, mixtures of compounds of the general formula (III) and / or (IV) also being included.

Examples of radicals R ^Y in formula (purple) are hydrogen, alkyl radicals such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert. -Butyl, n-pentyl, sec-pentyl, iso-pentyl, neo-pentyl, tert-pentyl radicals; Hexyl radicals, such as the n-hexyl radical; Heptyl radicals, such as the n-heptyl radical; Octyl radicals, such as the n-octyl radical and iso-octyl radicals, such as the 2,4,4-trimethylpentyl radical; Nonyl radicals, such as the n-nonyl radical; Decyl radicals, such as the n-decyl radical; Dodecyl radicals, such as the n-dodecyl radical; Hexadecyl radicals, such as the n-hexadecyl radical; Octadecyl radicals, such as the n-octadecyl radical; Cycloalkyl radicals, such as the cyclopentyl, cyclohexyl, cycloheptyl radical and methylcyclohexyl radical; Aryl radicals, such as the phenyl, naphthyl, anthracene and phenanthrene radical; Alkaryl radicals, such as the o-, m- and p-tolyl, xylyl, mesitylenyl and o-, m- and p-ethylphenyl radical; Alkaryl radicals, such as the benzyl radical, the α- and the β-phenylethyl radical; and alkylsilyl radicals such as trimethylsilyl, triethylsilyl, tri-n-propylsilyl, tri-iso-propylsilyl, dimethylethylsilyl, dimethyl-tert-butylsilyl and diethylmethylsilyl radical.

In formula (purple), the radicals R ^Y are preferably selected independently of one another from the group consisting of (i) C ₁ -C ₃ -alkyl radical, (ii) hydrogen and (iii) triorganosilyl radical of the formula -SiR ^b ₃ , in which the radicals R ^{b are,} independently of one another, C ₁ -C ₂₀ -alkyl radical. The radicals R ^Y are particularly preferably selected independently of one another from the methyl radical, hydrogen and trimethylsilyl radical.

The index a in formulas (III) and (IV) is preferably 1, so that X- each independently of one another denotes a monovalent anion.

Examples of anions X- in formula (III) and (IV) are: halides;

Chlorate CIO ₄ -;

Tetrachlorometalates [MCl ₄ ] - with M = Al, Ga;

Tetrafluoroborate [BF ₄ ] -;

Trichlorometalates [MCl ₃ ] ^~ with M = Sn, Ge;

Hexafluorometalates [MF ₆ ] - with M = As, Sb, Ir, Pt;

Perfluoroantimonates [Sb ₂ F ₁₁ ] -, [Sb ₃ F ₁₆ ] ^" and [Sb ₄ F ₂₁ ] -;

Triflate (= trifluoromethanesulfonate) [OSO ₂ CF ₃ ] ^" ; Tetrakis (trifluoromethyl) borate [B (CF ₃ ) ₄ ]

Tetrakis (pentafluorophenyl) metallate [M (C ₆ F _{5) 4} ] - with M = Al, Ga; Tetrakis (pentachlorophenyl) borate [B (C ₆ CI ₅ ) ₄ ]

Tetrakis [(2,4,6-trifluoromethyl (phenyl)] borate {B [C ₆ H _{2 (} CF _{3) 3} ]} -; hydroxy bis [tris (pentafluorophenyl) borate] {HO [B (C ₆ F _{5) 3} ] _2} ^~ ;

Closo-Carborate [CHBuHsCle] -, [CHBuHsBre] -, [CHBn (CH _{3) 5} Br ₆ ] -, [CHBiiFii] ^" , [C (Et) BnFn] -, [CBn (CF _{3) 12} ] - and B ₁₂ CI ₁₁ N (CH ₃₎ 3]

Tetra (perfluoroalkoxy) aluminate [Al (OR ^PF ) ₄ ] - with R ^PF = independently of one another perfluorinated C ₁ -C ₁₄ hydrocarbon radical;

Tris (perfluoroalkoxy) fluoroaluminate [FA1 (OR ^PF ) ₃ ] - with R ^PF = independently perfluorinated C ₁ -C ₁₄ hydrocarbon radical;

Hexakis (oxypentafluorotellur) antimonate [Sb (OTeF ₅ ) ₆ ]

Borates and aluminates of the formula [B (R ^a) 4] -, and [Al (R ^a) 4] -, wherein the radicals R ^a are each independently selected from aromatic C6-Ci4-hydrocarbon radical, in which min ^¬ least a hydrogen atom independently of one another by a radical selected from the group consisting of (i) fluorine, (ii) perfluorinated C ₁ -C ₆ -alkyl radical, and (iii) triorganosilyl radical of the formula -SiR ^b ₃ , in which the radicals R ^{b are} independently C ₁ - C ₂₀ - alkyl radical, is substituted; and tetrakis (trichlorosilyl) boranate [B (SiCl3> 4] -.

In formula (III) and formula (IV), preference is given to the anions X- selected from the group consisting of (i) [B (SiCl3) 4] - and

(ii) the compounds of the formulas [B (R ^a ) ₄ ] - and [Al (R ^a ) ₄ ] -, in which the radicals R ^{a are} each independently selected from an aromatic C6-Ci4 hydrocarbon radical in which at least one hydrogen atom independently of one another by a radical selected from the group consisting of (i) fluorine, (ii) perfluorinated C ₁ -C ₆ -alkyl radical, and (iii)

Triorganosilyl radical of the formula - SiR ^b ₃ , in which the radicals R ^{b are} independently C ₁ -C ₂₀ ^-alkyl radical, is substituted. Examples of radicals R ^a are m-difluorophenyl radical, 2,2,4,4-tetrafluorophenyl radical, perfluorinated 1-naphthyl radical, perfluorinated 2-naphthyl radical, perfluorobiphenyl radical, - C ₆ F ₅ , - CeH ₃ (m-CF ₃ ) ₂ ,

- C ₆ H ₄ (p-CF ₃ ), - C ₆ H ₂ (2,4,6-CF ₃ ) ₃ , - C ₆ F ₃ [2,4- (SiR ^b ₃ ) ₂ ], - C ₆ F ₃ [2,5- (SiR ^b ₃ ) ₂ ], - C ₆ F ₃ [2,6- (SlR ^b ₃ ) ₂ ], - C ₆ F ₃ [3,4- (SiR ^b ₃ ) ₂ ] , - C ₆ F ₃ [3.5-

(SiR ^b ₃ ) 2], - C ₆ F ₄ (2-SiR ^b ₃ ), - C ₆ F ₄ (3-SiR ^b ₃ ) and - C ₆ F ₄ (4-SiR ^b ₃ ),

- C ₆ F ₃ (m-SiMe ₃ ) 2, - C ₆ F ₄ (p-SiMe ₃ ), - C ₆ F ₄ (p-SiMe ₂ t-butyl).

Particularly preferred in formula (I I I) and (IV) are the anions X- selected from the group consisting of (i) [B (SiCl3) 4] - and

(ii) the compounds of the formula [B (R ^a ) 4] -, in which the radicals R ^{a are} independently selected from an aromatic C ₆ _{-C 14} hydrocarbon radical in which all hydrogen atoms are independently of one another by a radical selected from the group consisting of (i) fluorine and (ii) triorganosilyl radical of the formula -SiR ^b 3, in which the radicals R ^{b are,} independently of one another, C ₁ -C ₂₀ -alkyl radical, are substituted.

In formula (III) and (IV), the anions X- selected from the group consisting of (i) [B (SiCl3) 4] ^_ and (ii) the compounds of the formula [B (R ^a ) 4] are very particularly preferred -, in which the radicals R ^a are selected independently of one another from the group consisting of -C ₆ F ₅ , perfluorinated 1- and 2-naphthyl _{radical, - C 6} F ₃ [2,4- (SiR ^b ₃ ) ₂ ], - C ₆ F ₃ [2,5- (SiR ^b ₃ ) ₂ ],

- C ₆ F ₃ [2,6- (SiR ^b ₃ ) 2], - C ₆ F ₃ [3,4- (SiR ^b ₃ ) ₂ ], - C ₆ F ₃ [3,5- (SiR ^b ₃ ) ₂ ],

- C ₆ F ₄ (2-SiR ^b ₃ ), - C ₆ F ₄ (3-SiR ^b ₃ ) and - C ₆ F ₄ (4-SiR ^b ₃ ), in which the radicals R ^{b are} each independently C ₁ - Mean C ₂₀ -alkyl radical.

Most preferred in formula (I I I) and (IV) are the anions X- selected from the group consisting of [B (SiCl3) 4] -,

[B (C ₆ F ₅ ) 4] -, {B [C ₆ F ₄ (4-TBS)] ₄ } - with TBS = SiMe ₂ tert-butyl, [B (2-

Naph ^F ) 4] - with 2-Naph ^F = perfluorinated 2-naphthyl radical.

Preference is given to using at least one cationic silicon and / or germanium compound selected as the catalyst is from the group consisting of (i) silicon (II) and germanium (II) compounds of the general formula (III), in which the radicals R ^{Y are} independently selected from the group consisting of methyl radical, hydrogen and trimethylsilyl radical, and the anion X- is selected from the group consisting of [B (SiCl ₃ ) 4] ^" , [B (C ₆ F ₅ ) ₄ ] -, {B [C6F4 (4-TBS)] 4} - with TBS = SiMe2tert -Butyl, [B (2-Naph ^F ) 4] - with 2-Naph ^F = perfluorinated 2-naphthyl radical, and (ii) silicon (IV) and germanium (IV) compounds of the general formula (IV), in which the radicals R ^{Y are} independently selected from the group consisting of (i) C ₁ -C ₆ -alkyl radical and (ii)

Phenyl radical, and in which the radical Y is a 1,8-naphthalenediyl radical, and in which the radicals Z are independently selected from silicon (IV) or germanium (IV), and in which the anion X- is selected from Group consisting of [B (C ₆ F ₅ ) ₄ ] - and [B (SiCl ₃ ) 4] -.

At least one cationic silicon and / or germanium compound is particularly preferably used as catalyst, which is selected from the group consisting of [Cp * Si] ⁺ [B (C ₆ F ₅ ) ₄ ] -; [Cp * Si] ⁺ {B [C ₆ F ₄ (4-TBS)] ₄ } -, with TBS = SiMe ₂ tert-butyl;

[Cp * Si] ⁺ [B (2-Naph ^F ) ₄ ] -, with 2-Naph ^F = perfluorinated 2-naphthyl radical, [Cp * Ge] ⁺ [B (C ₆ F ₅ ) ₄ ] -; [Cp * Ge] ⁺ {B [C ₆ F ₄ (4-TBS)] ₄ } -, [Cp * Si] ⁺ [B (SiCl ₃ ) 4] -, [Cp * Ge] ⁺ [B (SiCl ₃ ) ₄ ] -,

[Cp (SiMe ₃ ) ₂ Ge] ⁺ [B (C ₆ F ₅ ) 4] -, [Cp (SiMe ₃ ) ₃ Ge] ⁺ [B (C ₆ F ₅ ) 4] -, [Cp (SiMe ₃ ) ₂ Ge] ⁺ [B (SiCl ₃ ) ₄ ] -, [Cp (SiMe ₃ ) ₃ Ge] ⁺ [B (SiCl ₃ ) ₄ ] - and compounds of the formula (IV) in which the radicals R ^Y are selected independently of one another are selected from the group consisting of (i) C ₁ _{-C 6} -alkyl radical and (ii) phenyl radical, and in which the radical Y is a 1,8-naphthalenediyl radical, and in which the radicals Z are independently selected from silicon (IV) or germanium (IV) and in which the anion X- is selected from the group consisting of [B (C6F ₅ ) ₄ ] - and [B (SiCl ₃ ) ₄ ] -. Very particular preference is given to using at least one cationic silicon and / or germanium compound which is selected from the group consisting of

[Cp * Ge] ⁺ [B (C ₆ F ₅ ) ₄ ] -, [Cp * Si] ⁺ [B (SiCl ₃ ) 4] -, [Cp * Ge] ⁺ [B (SiCl ₃ ) ₄ ] -, [Cp * Si] ⁺ [B (C ₆ F ₅ ) ₄ ] -, [Cp (SiMe ₃ ) ₃ Ge] ⁺ [B (SiCl3) 4] -, and compounds of the formula (IV) in which the radicals R ^{Y are} independently selected from the group consisting of (i) unbranched C ₁ -C ₄ -alkyl radical and (ii) phenyl radical, and in which the radical Y is a 1,8-naphthalenediyl radical, and in which the radicals Z are independent are selected from one another from silicon (IV) or germanium (IV) and in which the anion X- is selected from the group consisting of [B (C ₆ F ₅ ) ₄ ] - and [B (SiCl ₃ ) ₄ ] -.

The method according to the invention is preferably carried out in a temperature range from -20.degree. C. to 250.degree. C., the method is preferably carried out in a temperature range from 20.degree. C. to 150.degree.

The pressure in the process according to the invention can be freely selected by the person skilled in the art; the pressure is usually in the range from 0.1 bar to 50 bar. The process is particularly preferably carried out at normal pressure.

The reaction according to the invention can be carried out without a solvent or with the addition of one or more solvents. The proportion of the solvent or the solvent mixture, based on the compound of the general formula (I), is preferably at least 0.01% by weight and at most 1000 times the amount by weight, particularly preferably at least 1% by weight and at most 100 times the amount by weight , very particularly preferably at least 10% by weight and at most 10 times the amount by weight.

Aprotic solvents, for example hydrocarbons such as pentane, hexane, heptane, cyclohexane or toluene, chlorinated hydrocarbons such as Dichloromethane, chloroform, chlorobenzene or 1,2-dichloroethane, ethers such as diethyl ether, methyl tert-butyl ether, anisole, tetrahydrofuran or dioxane, or nitriles such as acetonitrile, benzonitrile or propionitrile, or organic sulfur oxides such as dimethyl sulfoxide, diethyl sulfoxide or sulfolane can be used .

Solvents or solvent mixtures with a boiling point or boiling range of up to 120 ° C. at 0.1 MPa are preferred. The solvents are preferably chlorinated and non-chlorinated aromatic or aliphatic hydrocarbons.

The amount of catalyst of the formula (III) or (IV) can be freely selected by the person skilled in the art. The amount of catalyst is usually below 1 mol%, based on the compound of the general formula (I).

The process according to the invention is technically very easy to carry out; it does not require any special conditions or technical requirements. The educts required are generally available on an industrial scale. The amounts of catalyst required are small and are usually below 1 mol%.

The process according to the invention gives the aldehydes of the general formula (II) in high yield. No by-products could be detected. Compared to the known processes, the process according to the invention has the advantage that the conversion into aldehydes can also be carried out with very small amounts of catalyst of 0.01 mol% or less, which considerably simplifies the process.

The process according to the invention also enables the simplified, safe use of aldehydes, in particular acetaldehyde and formaldehyde, by using the corresponding 1,3,5-trioxanes, which are acted upon at least one cationic silicon and / or germanium compound which form the aldehydes in situ. This upstream reaction enables, for example, strongly exothermic conversions of aldehydes to be better controlled and handled more safely.

For example, in the technically important oxidative coupling of siloxanes according to reaction equation (1)

Si-H + H-Si + 2 CH ₃ CHO => Si-O-Si + CH ₃ -O-CH ₃ (1) the use of paraldehyde in the presence of at least one cationic silicon and / or germanium compound as a catalyst to one milder, more controllable course of the reaction, which is of great importance for an industrial process.

The preparation of the aldehydes using the process according to the invention can be controlled by choosing the reaction conditions such as concentration and temperature, as the examples in Table 1 show. Thus, higher temperatures lead to a greater release of the aldehydes and lower temperatures to a reduced release of the aldehydes. Low concentrations favor the formation of aldehydes.

The formation of the aldehydes from the 1,3,5-trioxanes is a reversible reaction, so cationic silicon and / or germanium compounds can also be used to produce 1,3,5-trioxanes from the corresponding aldehydes.

The invention therefore also relates to the use of cationic silicon and / or germanium compounds as catalysts for the preparation of 1,3,5-trioxanes from aldehydes. 1,3,5-Trioxane (trioxymethylene) is required, for example, for the production of polyoxymethylene-based polymers (POM). These have exceptional properties such as mechanical, chemical and temperature stability. With the ever increasing demand for POM, there is a growing need for 1,3,5-trioxane and improved processes are being sought that can meet this need.

In the majority of processes, the formaldehyde formed in the gas phase by the oxidation of methanol is first introduced into water and the formaldehyde hydrate solution (formalin solution) formed is then converted into 1,3,5-trioxane at high temperature in the presence of acids, in particular sulfuric acid. The disadvantage of these processes is that formaldehyde cannot be converted directly into 1,3,5-trioxane, but only via the intermediate stage of the hydrate. This process is complex, time-consuming and energy-consuming, as water has to be removed from the system first, and is therefore costly. Also, only a conversion rate of 10% is achieved. Increasing the amount of catalyst could lead to a certain increase in space-time performance, but this measure promotes the formation of by-products. Hence processes of great interest which enable the direct conversion of gaseous formaldehyde into 1,3,5-trioxane.

EP2782906B1 describes the direct production of 1,3,5-trioxane from free formaldehyde in an aprotic solvent, organic sulfur oxides are explicitly mentioned, in the presence of acids such as trifluoroacetic acid.

Various Lewis acid catalysts, for example 5 mol% InCl3 (Synth. Commun. 2005, 35, 2801), 1-5 mol% UO ₂ ²⁺ (ACS Catal. 2019, 9, 9025),

20 mol% FeCl (Tetrahedron Lett. 2015, 56, 2406) or 12 mol% ZnO (Ind. Eng. Chem. Res. 2013, 52, 9538), which are used due to their lack of availability, their radioactivity or the large number of Quantities are not suitable for use in technology.

When using cationic silicon and / or germanium compounds as the catalyst, the very small amounts of catalyst that are required are advantageous because they increase the economic viability of an industrial process.

Examples

Example 1: Preparation of aldehyde (II) from 1,3,5-trioxane (I) A solution of a 1,3,5-trioxane of the formula (I) in dichloromethane is mixed with the catalyst and the amount of aldehyde according to the formula ( II) determined after 3 hours. Parameters, reaction conditions and results are shown in Table 1.

Example 2: Preparation of 1,3,5-trioxane (I) from aldehyde (II) A solution of aldehyde of the formula (II) in dichloromethane is mixed with the catalyst and the amount of 1,3,5-trioxane of the formula ( I) determined after 3 hours. Parameters, reaction conditions and results are shown in Table 2.

Example 3: Production of formaldehyde (II, R ^x = H) from 1,3,5-trioxane (I, R ^x = H)

Trioxane is dissolved in dichloromethane, the catalyst Cp * Ge ⁺ B (C ₆ F ₅ ) ₄ - is added and the mixture is left to stand overnight at ambient temperature (23 ° C.). The reaction mixture is examined by NMR spectroscopy. It contains 2 mol% formaldehyde based on the 1,3,5-trioxane used. Example 4: Preparation of 1,3,5-trioxane (I, R ^x = H) from

Formaldehyde (II, R ^x = H)

Gaseous formaldehyde is produced by heating solid, dry paraformaldehyde to 125-135 ° C. The formaldehyde gas that forms is passed into a dichloromethane solution which has been cooled to -10 ° C. and which contains Cp * Ge ⁺ B (C ₆ F ₅ ) ₄ - with the aid of a stream of argon. After the introduction, the solution contains 1,3,5-trioxane (I, R ^x = H) and formaldehyde in a ratio of 95: 5.

Claims

1. Process for the preparation of aldehydes, characterized in that at least one 1,3,5-trioxane of the general formula (I)

R ^x -CHO (II), in which the radicals R ^x correspond to the radicals R ^x from formula (I)

2. The method according to claim 1, characterized in that the radicals R ^x in formula (I) are independently selected from the group consisting of (i) hydrogen, (ii) methyl radical and (iii) unsubstituted, saturated or unsaturated C ₂ -C ₂₀ hydrocarbon radical.

3. The method according to any one of claims 1 or 2, characterized in that the radicals R ^x in formula (I) are independently selected from the group consisting of (i) hydrogen and (ii) methyl radical.

4. The method according to any one of claims 1-3, characterized in that the cationic silicon and / or germanium compound is selected from the group consisting of cationic silicon (II), silicon (IV), germanium (II) and / or germanium (IV) compounds.

5. The method according to any one of claims 1-4, characterized in that the cationic silicon and / or germanium compound is selected from (i) silicon (II) and germanium (II) compounds of the general formula

(III)

([M (II) Cp] ⁺ ) _a X ^a- (III) in which M is selected from germanium or silicon, and Cp is an n-bonded cyclopentadienyl radical of the general formula (IIIa)

SiR ₂₀ ^_ hydrocarbon radical ^b 3, in which the radicals R ^b independently of each other C ₁ -C, (ii) hydrogen, - of the formula in which the radicals R ^Y is independently selected from the group consisting of (i) triorganosilyl

, whereby in each case two radicals R ^{Y represents} a monocyclic or polycyclic C ₂ -C may form ₂₀ ^_ hydrocarbon group hydrocarbon group, and (iv) unsubstituted or substituted C ₁ -C ₁₀ ^_ hydrocarbyloxy together - (iii) unsubstituted or substituted C ₁ -C ₂₀ , and where substituted in each case means that at least one carbon atom in the hydrocarbon or hydrocarbonoxy radical can also be replaced by an Si atom, X ^a- denotes an a-valent anion and a can assume the values 1, 2 or 3; and (ii) silicon (IV) and germanium (IV) compounds of the general formula (IV)

wherein the radicals R ^Y are selected independently of one another from the group consisting of (i) hydrogen and (ii) C _{1 -C 50} hydrocarbon radical; and in which the radicals Z are independently selected from silicon (IV) or germanium (IV); and in which the radical Y denotes _{a divalent C 2} -C _{50 hydrocarbon radical;} and in which the subscript a takes on the values 1, 2 or 3; and in which X ^{a_ is} an a-valent anion.

6. The method of claim 5, wherein the index a in formula

(III) and (IV) assumes the value 1, so that X- each independently of one another denotes a monovalent anion.

7. The method according to claim 6, wherein in formula (III) and

Formula (IV) the anions X- are selected from the group consisting of (i) [B (SiCl3) 4] - and (ii) the compounds of the formulas [B (R ^a ) 4] - and [Al (R ^a ) 4] -, in which the radicals R ^{a are} each independently selected from aromatic C ₆ -C ₁₄ hydrocarbon radical in which at least one hydrogen atom is independently selected from the group consisting of (i) fluorine, (ii) perfluorinated C ₁ -C ₆ -alkyl radical, and (iii) triorganosilyl radical of the formula - SiR ^b 3, in which the radicals R ^{b are,} independently of one another, C ₁ -C ₂₀ ^-alkyl radical, is substituted.

8. The method according to any one of claims 1-7, wherein the cationic silicon and / or germanium compound is selected from the group consisting of (i)

Silicon (II) and germanium (II) compounds of the general formula (III), in which the radicals R ^Y are selected independently of one another from the group consisting of methyl radical, hydrogen and trimethylsilyl radical, and the anion X- is selected from the group consisting of

[B (SiCl ₃ ) 4] -, [B (C ₆ F ₅ ) ₄ ] -, {B [C ₆ F ₄ (4-TBS)] _4} - with TBS =

SiMe2tert-Butyl, [B (2-Naph ^F ) 4] - with 2-Naph ^F = perfluorinated 2-naphthyl radical; and (ii) silicon (IV) and germanium (IV) compounds of the general formula (IV) in which the radicals R ^{Y are} independently selected from the group consisting of (i) C ₁ -C ₆ -alkyl radical and ( ii)

Phenyl radical, and in which the radical Y is a 1,8-naphthalenediyl radical, and in which the radicals Z are independently selected from silicon (IV) or germanium (IV) and in which the anion X- is selected from the group consisting of [B (C ₆ F ₅ ) ₄ ] - and [B (SiCl ₃ ) 4] - ·

9. Use of cationic silicon and / or germanium compounds as catalysts for the production of 1,3,5-trioxanes from aldehydes.

10. Use according to claim 9, characterized in that the cationic silicon and / or germanium compounds are selected from the group consisting of cationic silicon (II), silicon (IV), germanium (II) and / or germanium (IV )-Links

11. Use according to claim 9 or 10, characterized in that the cationic silicon and / or germanium compounds are selected from (i)

Silicon (II) and germanium (II) compounds of the general formula (III)

([M (II) Cp] ⁺ ) _a X ^a - (III) in which M is selected from germanium or silicon, and Cp is an n-bonded cyclopentadienyl radical of the general formula (IIIa)

, whereby in each case two radicals R ^{Y represents} a monocyclic or polycyclic C ₂ -C may form ₂₀ ^_ hydrocarbon group hydrocarbon group, and (iv) unsubstituted or substituted C ₁ -C ₂₀ ^_ hydrocarbyloxy together - (iii) unsubstituted or substituted C ₁ -C ₂₀ , and where substituted in each case means that at least one carbon atom in the hydrocarbon or hydrocarbonoxy radical can also be replaced by an Si atom, X ^a- denotes an a-valent anion and a can assume the values 1, 2 or 3; and (ii) silicon (IV) and germanium (IV) compounds of the general formula (IV)

wherein the radicals R ^Y are selected independently of one another from the group consisting of (i) hydrogen and (ii) C ₁ _{-C 50} hydrocarbon radical; and in which the radicals Z are independently selected from silicon (IV) or germanium (IV); and in which the radical Y denotes _{a divalent C 2} -C _{50 hydrocarbon radical;} and in which the subscript a takes on the values 1, 2 or 3; and in which X ^{a- is} an a-valent anion.