DE1932022B2 - PROCESS FOR PRODUCING 1,2DIHYDROCHINOLINES - Google Patents

Description

converts, in which R is an alkyl radical having 1 to 5 carbon atoms.

Compared to the above-mentioned known method, the method according to the invention has the Advantage that it can be carried out in a shorter time under much milder process conditions can and easily removed the catalysts from the reaction product or neutralized in this can be. Nevertheless, the process according to the invention leads to the same yields as the known one Process (60 to 65%) or in certain cases to even higher yields.

According to the invention, isopropenyl ethyl ether is advantageously used as the isopropenyl alkyl ether.

In the reaction, the catalyst is preferably used in an amount of 1 to 10 percent by weight,

based on the weight of the aromatic amine.

_{Boron fluoride etherate (BF 3} · _{O (C 2} H _{5 I 2} ) or aluminum bromide (AlBr ₃ ) are advantageously used as Lewis acids. Benzene, ethyl acetate or chloroform are expediently used as solvents for the reaction.

After the reaction has subsided, which lasts 2 to 3 hours, the reaction mixture becomes with 10% Washed sodium hydroxide solution, dried over magnesium sulfate and the end product by vacuum distillation isolated.

During the reaction, which takes place with the development of heat, the first accumulates Amine to the double formation of the unsaturated ether with the formation of an unstable intermediate product. The elimination of alcohol leads to the formation of the Schiff base of a ketone. The Schiff base of the ketone reacts with the second molecule of the unsaturated ether according to the scheme of diene synthesis forming an unstable 4-alkoxy-1,2,3,4-tetrahydroquinoline, the alcohol under the reaction conditions to form the 1,2-dihydroquinoline derivative splits off.

NH ₂

CH, = COR

BF ₃

- RAW

N = C

CH ₂ = COR

RAW

R ₃ .

The invention is illustrated in more detail by the following examples.

example 1

6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline

13.7 g (0.1 mol) of p-phenetidine are dissolved in 50 ml of benzene and 2 g of boron fluoride etherate (BF ₃ · O (C ₂ H _S ) ₂ ) are added to the resulting solution. 25.8 g (0.3 mol) of isopropenyl ethyl ether are then introduced with stirring. The temperature of the reaction mixture rises to 52 ° C. as a result of the exothermic reaction. The mixture is stirred for about 1 hour, then washed with 10% sodium hydroxide solution and dried over magnesium sulfate. Fractionation of the reaction products gives 14 g (64.5%) of 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; Bp. 118 to 123 ⁰ C at 1 Torr, n? 1.5592.

Found ... C 77.43, H 8.89, 8.86%;
calcd ... C 77.38, H 8.98% for C ₁₄ H ₁₉ NO.

Example 2
6-methoxy-2,2,4-trimethyl-1,2-dihydroquinoline

12.3 g (0.1 mol) of p-anisidine are dissolved in 25 ml of benzene and 1 ml of boron fluoride etherate (BF ₃ · O (C ₂ H ₅ ) ₂ ) and then 25.8 g (0 , 3 mol) isopropenyl ethyl ether was added. The mixture is cooled somewhat with water. 2 hours after adding the ether, the mixture is treated in exactly the same way as in Example 1. When the reaction products are distilled, 11.5 g (56.6%) of δ-methoxy ^^ - trimethyl-l ^ -dihydroquinoline; Bp. 110 to 113 C at 1.5 Torr, ng 1.5658.

Found ... C 76.71, 77.10, H 8.81, 8.56%;
calcd ... C 76.71, H 8.43% for C ₁₃ H ₁₇ NO.

Example 3
l ^ -trimethyl-S ^ -benzo-1,2-dihydroquinoline

75 g (0.5 mol) of i-naphthylamine are dissolved in 500 ml of ethyl acetate, and 5 ml of boron fluoride etherate (BF ₃ · O (C ₂ H ₅ ) ₂ ) are added to the resulting solution. At a temperature of 27 ° C., 170 g (2 mol) of isopropenyl ethyl ether are added dropwise to the mixture. The reaction starts immediately and develops heat. The introduction of the ether is carried out with a wedge Geschwindigx that the temperature of 45 ⁰ C is not

CH ₃ exceeds. Then the mixture is 30 minutes

stirred, then washed with 10% sodium hydroxide solution and dried over magnesium sulfate. During the distillation 103 g (92%) of product are obtained. B.p. 134 to 136 C at 1.5 torr, n; 1.6730.

Found ... C 85.42, 85.52, H 7.99, 8.00%;
calculated ... C 86.05, H 7.67% for C ₁₆ H _r NO.

Example 4
6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline

27.4 g (0.2 mol) of p-phcnetidine are dissolved in 100 ml of chloroform, and 3 g of aluminum bromide (AlBr ₃ ) and then 68.8 g (0.8 mol) of isopropenyl ethyl ether are added to the resulting solution. The mixture obtained is treated as indicated in Example 1. The yield of o-ethoxy-Z ^ -trimethyl-1,2-dihydroquinoline is 26.9 g (62%).

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Claims (2)

Patent claims: 1. Process for the preparation of 1,2-dihydroquinolines the general formula (D wherein the radicals R, alkyl radicals with 1 to 5 carbon atoms, R ₂ a hydrogen atom and R ₃ a straight-chain or branched alkyl radical, an aryl, acyl, alkoxy, aryloxy, acylamino, nitro, hydroxy or acyloxy group or a halogen atom or R ₂ and R ₃ together with the carbon atoms to which they are bonded represent a fused-on benzene ring, characterized in that one mole of an amine of the general formula (H) NH, in the presence of a Lewis acid as a catalyst and an inert solvent at a temperature between room temperature and 52 ⁰ C with 3 to 4 mol of an isopropenyl alkyl ether of the general formula CH ₇ = C - OR (HD These compounds are used as antioxidants, stabilizers and herbicides. It is already a process for the preparation of substituted 1,2-dihydroquinolines by reaction of aromatic amines with acetone in the presence of catalysts such as iodine, bromine, benzenesulfonic acid, Toluenesulfonic acid or sulfanilic acid, known. For example, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline is used obtained by during 5 hours ίο a tenfold excess of acetone by up to 170 175 C heated p-phenetidine is passed. As a catalyst, sulfanilic acid is used in an amount of about 8 percent by weight used (anthology »Synthesis and investigation of the effectiveness of Stabilizers for polymeric materials «, Voronezh Verlag, Zentralno-Chemosemnoje knishnoje isdalelstwo, 1964, p. 180, in Russian). This known method has extraordinary disadvantages. So a high temperature must be used, the 7u side reactions, such as for resin formation and Demethylation leads, so that an extraordinary cleaning effort is required even to separate the by-products. It is also difficult to separate the catalyst used from the end product. In addition, the acetone consumption is great high. It is therefore the object of the invention to make available a new process for the preparation of the substituted 1,2-dihydroquinolines of the general formula I which requires only a small amount of energy and cleaning processes and can be carried out under much milder conditions.
According to the invention, this object is achieved by adding one mole of an amine of the general formula converts, in which R is an alkyl radical having 1 to 5 carbon atoms. 2. The method according to claim 1, characterized in that in the presence of a Lewis acid as a catalyst and characterized in that _{enylethyl ether is used as the isopropenyl alkyl ether isopropyl 45 of} an inert solvent at a temperature. between room temperature and 52 "C with 3 to 4 moles of an isopropenyl alkyl ether of the general formula The invention relates to a process for the preparation of 1,2-dihydroquinolines in general formula (D wherein the radicals R _{1 are} alkyl radicals with 1 to 5 carbon atoms, R _{2 is} a hydrogen atom and R _{3 is} a straight-chain or branched alkyl radical, an aryl, acyl, alkoxy, aryloxy, Ac> Laiino, nitro, hydroxy or acyloxy group or a halogen atom or R ₂ and R ₃ together with the carbon atoms to which they are attached represent a fused-on benzene ring. CH, = C - OR (III)