JPS6157815B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing terpene-type aldehydes. More specifically, geranylamine derivative ( ) (trans type) or nerylamine derivative ( ) (cis type) or 7-hydroxygeranylamine derivative ( ) (trans type) or 7-hydroxynerylamine derivative ( ) (cis form) is isomerized using mercaptans as a solvent to form enamines () or (), and then these are hydrolyzed to produce terpene aldehydes. (In the formula, R represents an alkyl group having 1 to 6 carbon atoms)
The terpene aldehyde obtained by the present invention includes citronenal when a geranylamine derivative and/or nerylamine derivative is used as a raw material, and hydroxyl when a 7-hydroxygeranylamine derivative and/or 7-hydroxynerylamine derivative is used as a raw material. Citronellal is obtained. Citronellal is contained in natural citronella oil, and is an important substance that is used in large quantities as a fragrance itself and as a raw material for fragrances such as menthol and hydroxycitronellal. Furthermore, hydroxycitronellal has been used in large quantities as a synthetic fragrance since ancient times, and is an essential and important substance as a component of mixed fragrances. The present inventors have conducted extensive research into industrially advantageous methods for producing these terpene-type aldehydes, and have found that geranylamine derivatives () or nerylamine derivatives () or 7-hydroxygeranylamine derivatives () or Discovered a brand new method in which isomerization of 7-hydroxynerylamine derivatives () to enamines proceeds in high yield and high selectivity by heating in the presence of mercaptans, and completed the method of the present invention. did. The compound of the general formula () or () as the raw material used in the present invention can be produced by various methods, but
The method of producing it from isoprene and a secondary amine is a particularly important and industrially advantageous production method. That is, isoprene and dialkylamine are combined with Li metal or organic
The reaction can be carried out in the presence of a Li catalyst such as Li to give NN dialkyl 3.7 dimethyl octase 2.6 dienylamine. In addition, the compound of the general formula () or () can be prepared by combining the compound of the general formula () or () obtained above with Chemistry Letters, pp. 1031-1032 (1975): [Chemistry Letters 1031-1032
(1975)] by adding water. Although the method of the present invention by isomerizing β, γ unsaturated amine derivatives to obtain enamines is known (JP-A-52-77005, JP-A-53-95909), it requires the use of expensive catalysts and This method has drawbacks that are not industrially advantageous, as it often requires complicated catalyst preparation and is difficult to separate and reuse. However, the mercaptans used in the method of the present invention are inexpensive and easily available as catalysts, and can be used as they are without any modification. Further, after the reaction is completed, it can be separated by simple operations such as washing with an alkaline aqueous solution or distillation, and can be used again, which makes it very advantageous industrially. Specific examples of the mercaptans used in the present invention include unsubstituted and/or substituted aromatic mercaptans such as thiophenol, omptoluenethiol, P-But-thiophenol, and P-chlorothiophenol, and 1.2 ethanedithiol. Examples include mercaptans such as alkyl dithiols such as. The amount of mercaptans used in the present invention is preferably in the range of 0.1 to 50% by weight based on the raw materials, and particularly preferably in the range of 0.5 to 20% by weight. The reaction temperature may be carried out in a range of 80°C to 250°C, particularly preferably in a range of 120°C to 200°C. Although the reaction proceeds very selectively with or without the use of a solvent, the use of a solvent increases the selectivity of the isomerization reaction to enamines. Any catalyst can be used as long as it is stable under the isomerization reaction conditions and does not participate in the reaction. Specific examples of such preferred solvents include chain saturated alcohols such as ethanol, butanol, hexanol, and octanol; glycols such as ethylene glycol and propylene glycol; chain saturated hydrocarbons such as hexane, octane, decane, and tridecane; Aromatic hydrocarbons such as benzene, toluene and xylene can be mentioned. Furthermore, if the reaction is carried out by adding a small amount of a radical initiator such as azobisisobutyronitrile (AIBN) or benzoyl peroxide (BPO) to the mercaptans in an amount of 0.1 to 20% by weight as a reaction accelerator, the reaction can be accelerated. is also possible. After the isomerization reaction is completed, when a dilute solution of an acid such as hydrochloric acid, sulfuric acid, or acetic acid is added to the reaction solution and stirred, enamines are decomposed and aldehydes are separated. If this oil layer is separated from the aqueous layer and purified by distillation, aldehydes can be obtained. It is also possible to obtain a highly pure terpene aldehyde by first isolating the enamine by distillation and then treating it with a dilute acid as described above. The present invention will be explained in detail by giving examples below. Example 1 0.5 g of thiophenol was added to 10 g (48 mmol) of neryl diethylamine, and the mixture was stirred at 180°C for 1 hour. After the reaction was completed, the reaction mixture was cooled and analyzed by gas chromatography. As a result, the conversion rate of neryl diethylamine was 70%, and the selectivity of the obtained citronellal neryl diethylamine was 75%. (Selectivity represents the yield of citronellal diethylamine relative to the converted neryl diethylamine.) When 50 ml of 5% sulfuric acid was added to the citronellal diethyl enamine and stirred, citronellal was separated. This was separated, the residual liquid was extracted with benzene, and both were combined and distilled to obtain pure citronellal. Examples 2 to 4 0.5 g of the mercaptan shown in Table 1 was added to 10 g of neryl diethylamine, and a reaction was carried out under the same conditions as in Example 1 to obtain the results shown in Table 1.

[Table] Example 5 Thiophenol added to 10g of neryldiethylamine
10g of n-decane was added as a 0.5g solvent, and the mixture was stirred at 180°C for 1 hour. After the reaction was completed, it was cooled and analyzed by gas chromatography. As a result, the conversion rate of neryl diethylamine was 69%, and the selectivity of the obtained citronellal enamine was 94%. This citronellal enamine was treated in the same manner as in Example 1,
Pure citronellal was obtained. Example 6 Thiophenol in 10g of neryl diethylamine
0.5g of AIBN and 0.06g of AIBN were added, and the mixture was stirred at 180°C for 1 hour. As a result of gas chromatography analysis, the conversion rate of neryl diethylamine was 82%, and the selectivity of the obtained citronellal enamine was 75%. Example 7 0.5 g of thiophenol and 10 g of n-decane were added to 10 g (0.055 mol) of neryldimethylamine, and the mixture was stirred at 180°C for 2 hours. After the reaction was completed, the mixture was cooled and analyzed by gas chromatography. As a result, the conversion rate of neryl dimethylamine was 58%, and the selectivity of the obtained citronellal dimethyl enamine was 79%. Example 8 0.3 g of thiophenol and 6 g of n-decane were added to 6 g of 7-hydroxygeranyl diethylamine at 180°C.
The mixture was stirred for 2 hours. After the reaction was completed, the mixture was cooled and analyzed by gas chromatography. As a result, the conversion rate of 7-hydroxygeranyl diethylamine was 82% and the selectivity of hydroxycitronellal diethyl enamine was 81%. 4N sulfuric acid was added to this hydroxycitronellal diethylenamine until it became weakly acidic, and the mixture was reacted at 20°C for 9 hours. After the reaction, the mixture was extracted with ether and distilled to obtain pure hydroxycitronellal.

Claims (1)

[Claims] 1 General formula or or (In the formula, R represents an alkyl group having 1 to 6 carbon atoms)
The geranylamine derivative () or nerylamine derivative () or 7-hydroxygeranylamine derivative () or 7-hydroxynerylamine derivative () represented by the formula is isomerized using mercaptans to obtain the general formula () or (). A method for producing terpene-type aldehydes, which comprises preparing an enamine represented by the formula (wherein R has the above-mentioned meaning) and then hydrolyzing this enamine.