JPH055823B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing Schiff bases, and more particularly to a method for producing Schiff bases directly from hydrocarbons and isonitrile.

[Prior art]

Schiff bases can generally be produced in good yields by dehydration condensation of the corresponding aldehyde and a primary amine.

However, raw aldehydes must be produced by oxidation of primary alcohols, hydroformylation of olefins, oxidation of methyl-substituted aromatic compounds, carbonylation of aromatic halides, Koch reaction or Vilsmeyer reaction of aromatic compounds, etc. Furthermore, in order to produce Schiff base,
A disadvantage was that the aldehyde thus obtained had to be further reacted with an amine.

[Purpose of the invention]

The object of the present invention is to overcome the above-mentioned conventional drawbacks and to provide a method for directly producing Schiff's base, which comprises directly introducing a carbon-nitrogen double bond into hydrocarbons.

[Structure of the invention]

The method for producing Schiff bases of the present invention which achieves the above object is carried out in the presence of a rhodium complex of at least one organic phosphorus compound selected from the group consisting of phosphine, phosphonite, phosphinite and phosphite, or at least one organic This method is characterized by reacting hydrocarbons and isonitrile under light irradiation in the coexistence of a phosphorus compound and a rhodium compound.

Schiff bases are an important group of compounds that are used as synthetic intermediates for nitrogen-containing compounds or as resin materials for liquid crystals and the like.

The method for producing Schiff's base of the present invention is carried out in the presence of a rhodium complex of at least one organic phosphorus compound selected from the group consisting of phosphine, phosphonite, phosphinite, and phosphite.

Phosphorus in these organic phosphorus compounds is all trivalent, and specifically, monodentate organic phosphorus compounds (indicated by PR' ₃ ) such as trimethylphosphine, triethylphosphine, tributylphosphine, trivalent Chain phosphine such as octylphosphine, triphenylphosphine, tri(p-tolyl)phosphine, tri(p-anisyl)phosphine, cyclic phosphine such as P-methylphosphorene, P-methylphosphole, dimethyl methylphosphonite , phosphonites such as dimethyl phenylphosphonite, phosphinites such as methyl dimethyl phosphinite, methyl diphenyl phosphinite, and phosphites such as triethyl phosphite, triphenyl phosphite, trimethylolpropane phosphite, Also, bidentate organophosphorus compounds (R ² ₂ P
-PR ² ₂ ), for example, 1,2-bis(dimethylphosphino)ethane, 1,3-bis(dimethylphosphino)propane, 1,4-bis(dimethylphosphino)butane, 1,2- Bis(diphenylphosphino)ethane, 1,4-bis(diphenylphosphine)butane, 1,1'-bis(dimethylphosphino)ferrocene, 1,1'-bis(diphenylphosphino)ferrocene, α ，
α′-bis(dimethylphosphino)-ο-xylene,
Examples include bisphosphine such as 1,2-bis(dimethylphosphino)henzen.

These rhodium complexes of organophosphorus compounds can have various structures, but
Monovalent rhodium complexes are preferred.

Specifically, for example, RhX (PR' ₃ ) ₃ (PR' ₃ indicates the above content, and X is selected from the group consisting of hydrogen, a halogen atom, a hydroxyl group, a cyano group, an alkoxy group, a carboxylate group, and a thiocyanato group) (hereinafter the same), RhX (CO) (PR′ ₃ ) ₂ , RhX
(CO) ₂ (PR′ ₃ ), RhX (CO) ₂ (PR′ ₃ ) ₂ , RhX
(PR′ ₃ ) ₄ , [Rh(PR′ ₃ ) ₄ ]Y (Y is PF ₆ , B
It represents a group selected from the group consisting of (C ₆ H ₅ ) ₄ , BF ₄ , CIO ₄ and the above X. (Same below), [Rh (PR′ ₃ ) ₂
(CNR ² ) ₂ ]Y (CNR ² represents isonitrile, R ² represents an alkyl or aryl group. The same applies hereinafter),
[Rh(PR′ ₃ ) ₂ (CNR ² ) ₃ ]Y, RhX(CO)(R ² ₂ P−
PR ² ₂ ), etc.

In the method for producing Schiff's bases of the present invention, it is not necessarily necessary to prepare the rhodium complex of the above-mentioned organophosphorus compound in advance and use the above-mentioned organophosphorus compound and an appropriate rhodium compound in the reaction system. It can also be preferably carried out by a method of forming a rhodium complex in .

Rhodium compounds preferably used for this purpose include Rh(acac)(CO) ₂ (acac
represents acetylacetonato group), [RhX
(CO) ₂ ] ₂ , [RhX(DE)] ₂ (DE is norbornadiene, 1,5-cyclooctadiene, or 1,5
-Hexadiene), [RhX (EN) ₂ ] ₂ (EN indicates ethylene or cyclooctene), RhX
Examples include (CO)(PR′ ₃ ) ₂ .

The raw material compound suitable for the method of the present invention has 30 carbon atoms.
The following hydrocarbons may be substituted with an alkoxy group, an acyl group, an acyloxy group, a carbalkoxy group, a cynoa group, a halogen, or the like.

Specific examples of hydrocarbons and substituted products used in the present invention include methane, ethane, propane, butane, pentane, hexane, octane, isopentane, iso-ontane, decane, eicosane, diethyl ether, 1-fluorohexane, and benzene. , toluene, ethylbenzene, n-
Examples include hexylbenzene, o-xylene, m-xylene, tetralin, naphthalene, 2-methylnaphthalene, 9,10-dibutylanthracene, chlorobenzene, and anisole.

The amount of these hydrocarbons to be used relative to the rhodium complex or rhodium compound can be selected arbitrarily, and when these hydrocarbons are liquid, it is also advantageous to use the amount of the hydrocarbons themselves as a solvent. .

However, if the hydrocarbons are solid at the reaction temperature, solvents such as cyclohexane, decalin, etc. are advantageously used.

Furthermore, there are no limitations on the structure of the isonitrile used in the present invention, such as methylisonitrile, t
-Butylisonitrile, neopentylisonitrile, cyclohexylisonitrile, phenylisonitrile, p-tolylisonitrile, etc. are used.

The amount of isonitrile added is not critical to the occurrence of the reaction, but if the amount of isonitrile present in the reaction system is significantly greater than the amount of rhodium complex or rhodium compound present, it has been recognized that the reaction rate tends to decrease. In such cases, it is preferable to add isonitrile in small portions.

The reaction in the present invention proceeds under light irradiation, but the wavelength range of light may be in the so-called ultraviolet/visible light range, and irradiation with mercury lamps, tungsten lamps, halogen lamps, xenon lamps, sunlight, etc. is preferably used. .

Although the reaction proceeds below 0°C, it can also be heated to 250°C to achieve favorable reaction rates.

The product after the reaction can be easily separated by removing unreacted hydrocarbons and solvent by distillation or the like, and then subjecting the product to chromatography, distillation, recrystallization, or the like.

〔Effect of the invention〕

According to the present invention, Schiff's base can be obtained directly from hydrocarbons in one step, and the product can be easily separated.

Therefore, according to the present invention, Schiff's base can be efficiently produced.

Schiff bases are an important group of compounds that are used as intermediates for the synthesis of nitrogen-containing compounds or as functional materials for liquid crystals and the like.

Examples of the present invention will be described below.

[Example] Example 1 A benzene solution of 6.7 mg of RpCI(CO)(P(CH ₃ ) ₃ ) ₂ was charged into a Pyrex internal irradiation type photoreaction vessel with an internal volume of 70 ml, and 180 mg of cyclohexylisonitrile was charged.
was added and stirred at room temperature for 16.5 hours while irradiating with a 100W high-pressure mercury lamp.

As a result of gas chromatography analysis, N-
It was found that benzylidenecyclohexylamine was produced in a yield of 9% based on the rhodium complex.

Example 2 The amount of cyclohexylisonitrile used was 16.9mg
The same operation as in Example 1 was repeated except that.

The yield of N-benzylidenecyclohexylamine was 245% based on rhodium.

Example 3 The same reaction as in Example 1 was carried out using 28.8 mg of p-tolylisonitrile in place of cyclohexylisonitrile.

The yield of N-benzylidene-p-toluidine was 4% based on rhodium.

Example 4 The same reaction as in Example 1 was carried out using 5.8 mg of methylisonitrile in place of cyclohexylisonitrile.

The yield of N-benzylidenemethylamine was 38% based on rhodium.

Example 5 The same reaction as in Example 1 was carried out using 17 mg of t-butylisonitrile in place of cyclohexylisonitrile.

The yield of N-benzylidene-t-butylamine was 3% based on rhodium.

Example 6 Using isogram atom Rh (RhCl ₍ CO) 2 ) ₂ instead of RhCl(CO)(P(CH ₃ ) ₃ ) ₂ as a rhodium complex,
Furthermore, when 2 equivalents of trimethylphosphine was added to Rh and the reaction of Example 2 was repeated, the yield of N-benzylidenecyclohexylamine was 207% based on rhodium.

Example 7 12 mg of chlorocarbonylbis(tributylphosphine) rhodium and cyclohexylisonitrile were placed in a Pyrex internal irradiation type photoreaction vessel with an internal volume of 70 ml.
18.3 mg and 30 ml of pentane were charged, and the mixture was stirred at room temperature under nitrogen for 22.5 hours while being irradiated with light using a 100 W high-pressure mercury lamp. At 3 hours of reaction time, 11.7 mg of cyclohexylisonitrile was added.

As a result of analysis by gas chromatography and GC-MS, the following products were detected (yields are based on rhodium).

Products Yield (%) N-hexylidenecyclohexylamine 6 N-(2-methylpentylidene)cyclohexylamine 12 N-(2-methylbutylidene)cyclohexylamine 12.

Claims (1)

[Claims] 1. In the presence of a rhodium complex of at least one organic phosphorus compound selected from the group consisting of phosphine, phosphonite, phosphinite, and phosphite, or in the coexistence of at least one organic phosphorus compound and a rhodium compound, hydrocarbons and A method for producing Schiff bases, which comprises reacting isonitrile under light irradiation.