JPS62169741A - Production of citral - Google Patents

Abstract

PURPOSE:To obtain the titled substance useful as a food flavor and synthetic raw material for vitamin E, A, etc., with simple process in high yield, by using easily available geranylamine derivative and nerylamine derivative as raw materials and reacting the materials using a specific catalyst in the presence of a hydrogen acceptor. CONSTITUTION:The objective compound can be produced by hydrolyzing citralenamine produced by reacting using a geranylamine derivative or nerylamine derivative of formula I or formula II (R1 and R2 are lower alkyl or R1 and R2 together with adjacent nitrogen atom form a 4-5C cyclic group or morpholino group) as a raw material and reacting the derivative in a solvent such as dimethylformamide in the presence of a hydrogen acceptor (preferably mesityl oxide and its amount is preferalby nearly equivalent to the substrate) using a ruthenium-phosphine as a catalyst. The above catalyst is a complex obtained by coordinating a bidentate phosphine ligand with ruthenium.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides citral enamine by reacting a geranylamine derivative or a nerylamine derivative in the presence of a hydrogen acceptor with a ruthenium-phosphine complex as a catalyst,
This invention relates to a method for producing citral by hydrolyzing this.

[Conventional technology]

Citral is used as food flavoring, soap flavoring, and cologne fragrance, as well as ionone, methylionone, and vitamin A.

It is important as a raw material for the synthesis of E. Citral has two stereoisomers: gelaral (trans type) and neranil (cis type), but for the purpose of fragrance, the mixture is treated as citral without distinguishing between these isomers. . In this specification, the term citral is used to mean these isomers as well as mixtures.

The source of citral was lemongrass oil, but recently it has been produced by air oxidation of geraniol from turpentine. That is, α-pinene is hydrogenated to form pinane,
This is air oxidized to hydroperoxide, then to vinylol, which is then pyrolyzed to linalool,
It is isomerized to geraniol and nerol, which are dehydrogenated to obtain citral. Also, JP-A-57-10
According to No. 2831, using amine oxide obtained by oxidation of N,N-diethylnerylamine as a raw material,
This is reacted with an acid anhydride, such as acetic anhydride or propionic anhydride, and the yield is 51.4 to 51.4 to amine oxide.
A method for obtaining citral is disclosed in 53.7.

[Problem that the invention seeks to solve]

However, the above method had drawbacks such as a long number of steps and a low yield, and was not satisfactory.

Therefore, it has been desired to develop a method by which citral can be obtained in good yield with simple operations.

[Means for solving problems]

Under such circumstances, the present inventor was conducting research on the isomerization reaction of geranylamine derivatives and nerylamine derivatives, and found that citral enamine could be efficiently obtained by using a ruthenium-phosphine complex as a catalyst.
They discovered that by hydrolyzing this, citral could be obtained in good yield with simple operations, and the present invention was completed.

That is, the present invention provides compounds of the formula (I) or (II), (wherein R,, R, represents a lower alkyl group, or R1
and R7 together with the adjacent nitrogen atom has 4 to 4 carbon atoms.
A geranylamine derivative or a nerylamine derivative represented by (representing the formation of a cyclic group or a morpholino group in 5) is reacted with a ruthenium-phosphine complex as a catalyst in the presence of a hydrogen acceptor to form a citral enamine, which is then hydrated. The present invention provides a method for producing citral, which is characterized by decomposition.

To carry out the present invention, first, 0□005
~0.02 moles of ruthenium-phosphine complex, 1-3
Add moles of hydrogen acceptor, in the presence of solvent, ioo~1
React at 20°C for 10 to 20 hours.

As a solvent, dimethylformamide, 1゜3-dimethyl-2-imidazolidinone, N-methylpyrrolidone,
Aprotic polar solvents such as diethylene glycol dimethyl ether, tetrahydrofuran, and dimethyl sulfoxide can be used, and toluene and the like can be used as the aprotic nonpolar solvent. The amount of solvent used is preferably 1 to 5 times the amount (volume) of the raw material amine.

After the reaction is completed, the solvent is recovered under reduced pressure. If a dilute solution of sulfuric acid, hydrochloric acid, acetic acid, etc. is added directly after the reaction without separating the citral enamine obtained by stirring from the reaction solution, it will be easily hydrolyzed to produce citral. If this is purified by solvent extraction, distillation, etc., citral with a purity of 95% or more can be obtained.

The geranylamine derivative or nerylamine derivative represented by the above formulas (I) and (II) used in the present invention is obtained by adding an amine compound and butyllithium to geranyl chloride or neryl chloride obtained by reacting geraniol or nerol with phosphorus pentachloride. It is easily produced by reacting the obtained amine lithium compound. Other methods include telomerization with a secondary amine of imprene or myrcene using an alkali metal compound [K, Takabe et al.: Tetrahedron Lett, 4009
(I972)] (S, Vuktanabe et al.: Ch
Em, Ind., 231 (I973)). The amine compounds used here include dimethylamine,
diethylamine, di-n-propylamine, di-iΔ-propamine, di-n-butylamine, pyrrolidine,
Examples include piperidine and morpholine.

Hydrogen acceptors include boron, mesityl oxide, 1
-octene, cyclohexene, limonene, cycloocta-1,5-diene, styrene, etc. are used, among which α
, β-unsaturated ketones have a high ability, and among them, mesityl oxide is preferred. The amount of hydrogen acceptor used is preferably approximately equivalent to that of the substrate; for example, if more than three times the amount is used, the amount of by-products presumed to be Dale-Alder products will increase significantly.

The ruthenium-phosphine complex used in the present invention is a complex in which a bidentate phosphine ligand is coordinated to ruthenium, and
It is represented by the following formula (I).

RumXnLpAq (I) (wherein, X represents a hydrogen atom, a chlorine atom, hydrogen chloride, L represents a ligand, A represents a tertiary amine, m is 1 or 2, n
is 1 to 4, p is 2 to 4, and q is 0 or 1) Examples of such ruthenium-phosphine complexes include the following.

Ru, (J4(BINAP), Et3NRuH(J(B
INAP).

RuH, (BINAP).

Ru, Cg, (T-B INAP), Et, NRuH
(J(T-BI NAP).

RuH2 (T-BINAP).

Ru, (J4(t-Bu-BINAP), Et3NRu
t((J(t-Bu-BINAP),.

RuH, (t-Bu-BINAP).

Ru2(J, (I,4-Diphos)2Et3NRu
n(J(I,4-Diphos)2Ru,C4(ゝC:
PPh, ), Et3N In the above compound, Et is an ethyl group, Ph is a phenyl group, BINAP is 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl,
T-BINAP 2,2'-bis(di-paratolylphosphino)-1,1'-binaphthyl, t-Bu-BIN
AP is 2,2/-bis(di-para-tertial-butylphenylphosphino)-1,1'-binaphthyl, 1,
4-Diphos represents 1,4-bis(diphenylphosphino)butane. Such ruthenium-phosphine complexes are described, for example, in the literature (Y, 15hii et al.: Tetr
ahedronLett,, 24.2677 (I9
83) ] (Y, l5hii et al.: Chemlett
,, 1179 (I982)) (T, Ikar
iya et al.: J, Chem, Soc, Chem,
Common, 922 (I985)).

For example, to give an example of producing Ru, CJ, (BINAP), Et, and N, first, ruthenium chloride and cycloocta-1,5-die (abbreviated as COD) are reacted in an ethanol solution [RuCg, (COD)]. ] , get [
:M, A.

13ennet et al.: Chemistry and I
nd,, 1516e (I959)].

Then, (RuC42(COD)) n1 mol and BINA
After heating and reacting 1.2 moles of P with 4 moles of triethylamine in a solvent such as toluene, the crystals were taken from house to house.
Purify by recrystallizing in a solvent. The ruthenium-phosphine complex can be isolated as a crystal and used, or the ruthenium complex can be prepared "in aitu" and used as it is in the reaction.

In the present invention, when enamine is hydrolyzed to obtain citral, the aqueous layer separated is made alkaline with caustic soda, etc., extracted with a solvent such as toluene, and then distilled to produce geranyl, an unreacted raw material. Amine derivatives such as nerylamine derivatives or nerylamine derivatives can be easily recovered. Further, the amine of the geranylamine derivative or the nerylamine derivative, which is generated by decomposition during the reaction process, can be recovered with a recovery rate of 95 or more.

〔Example〕

Next, the present invention will be explained with reference to Examples.

Example 1 Geranyldiethylamine 10.5% (50 mmol),
Ru, (J, (BINAP), Et, NO, 423
ft (0.5 mmol), dimethylformamide 2
6m1. Five parts (60 mmol) of mesityl oxide were placed in a sealed tube and reacted at 120°C for 12 hours. After the reaction was completed, a portion was taken out, trans-stilbene was added as an internal standard reagent, and GLC analysis was performed to determine the conversion rate and selectivity of the reaction from geranyl diethylamine to citral enamine. Conversion rate is 43.3%, selection rate is 73.7
It was Chi. Then, dimethylformamide was distilled off, 5ml of water and 5Qml of ethyl ether were added, and the mixture was heated to 0°C.
7 Qml of 10% acetic acid was slowly added dropwise thereto, the pH was adjusted to 4-5, and the mixture was stirred for 2 hours. It separates into water and oil layer, so extract the water layer with ethyl ether,
This was combined with the oil layer, washed with 5% hydrochloric acid and 10% aqueous sodium carbonate solution, and dried using magnesium sulfate.

After distilling off the solvent, distillation was performed to obtain 2.347 citral (theoretical yield: 71%) of fraction 80-b. According to GLC analysis, this product was a 25:75 mixture of neral and geranial.

In the above step, the aqueous layer separated by ether extraction after hydrolysis is cooled with ice water, made alkaline by adding a 50% aqueous solution of caustic soda, extracted with a tolutan, and distilled to produce diethylamine 1.51y- (Recovery rate 95
h) and unreacted geranyl diethylamine 5.35%
(recovery rate 90%).

Example 2 Neryl diethylamine 10.5 ? (50 mmol)
, Ru, C4(BINAP)2Et, NO, 423P
(0.5 mil!J% le), dimethylformamide 26 ml. 17 ml (I 50 mmol) of mesityl oxide was placed in a sealed tube and reacted at 100°C for 200 hours. When the reaction was completed, GLC analysis was performed in the same manner as in Example 1, and the conversion rate was 36.0% and the selectivity was 58.1%.

Then, dimethylformamide was distilled off and 50ml of water was added.
, ethyl ether 5 (HJ) was added, and the mixture was cooled to 0°C. To this, 10-thiacetic acid 70- was slowly added dropwise, the pH was adjusted to 4-5, and the mixture was stirred for 2 hours. The aqueous and oil layers were separated, and the aqueous layer was cooled to 0°C. The portion was extracted with ethyl ether, combined with the oil layer, washed with 5-dihydrochloric acid and 10% aqueous sodium carbonate solution, and dried using magnesium sulfate.After distilling off the solvent, distillation was performed to obtain a
b fraction of citral 1.435' (theoretical yield 52.3%)
I got it. According to GLC analysis, this product was a 33:67 mixture of neral and geranial.

In addition, 1.25 J of diethylamine was added in the same manner as in Example 1.
(recovery rate 95 cm) and neryl diethylamine 6.05
y- (recovery rate 90%) was recovered.

Example 3 Geranyldiethylamine 2.14 (I0 mmol), (
(RuC also (COD)) n28 rn9 (0.1 mmol), BINAP66■ (I0 mmol), dimethylfluoro/l/A 7 mi)" 5.2rnl, mesityloxy)" 1.2 mJ C12 mmol) The mixture was placed in a sealed tube and reacted at 120°C for 12 hours. GLC analysis was performed in the same manner as in Example 1 to determine the conversion rate and selectivity of the reaction leading to citral enamine, and the conversion rate was 73.7.
%, and the selectivity was 54.0%. Then, by treating in the same manner as in Example 1, the boiling point was 80~bH? Citral o, s 9? (Theoretical yield 52.
5ch) was obtained. According to GLC analysis, this product was a 27:73 mixture of neral and geranial.

Examples 4 to 12 Ru, C4 (BINAP) used in Example 1,
Citral was obtained from υgeranyldiethylamine in the same manner as in Example 1, using each ruthenium-phosphine complex instead of Et3N. The results are shown in Table 1.

Examples 12 to 15 Citral was obtained in the same manner as in Example 1 except that geranyl diethylamine used in Example 1 was replaced with each keranylamine derivative. Second result
Shown in the table.

Table 2 [Effects of the Invention] The present invention uses useful citral as raw materials from readily available geranylamine derivatives and nerylamine derivatives,
It is a production method with high industrial value that requires relatively short steps and provides good yields.

that's all

Claims (1)

[Claims] 1. Formula (I) or (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (I) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (II) (In the formula, R_1 and R_2 are Represents a lower alkyl group,
or R_1 and R_2 together with adjacent nitrogen atoms form a cyclic group or morpholino group having 4 to 5 carbon atoms) in the presence of a hydrogen acceptor. A method for producing citral, which comprises reacting with a ruthenium-phosphine complex as a catalyst to produce citral enamine, and hydrolyzing this.