DE810629C - Process for the preparation of 3, 7-dimethyl-1- (2 ', 6', 6'-trimethyl-cyclohex-1'-enyl) -nona-4, 6, 8-trien-1-yn-3-ol - Google Patents

Description

Process for the preparation of 3,3-dimethyl-1- (2 ', 6', 6'-trimethylcyclohex-l'-enyl) -nona-4, 6, 8-trien-1-yn-3-ol The invention relates focuses on the production of a new unsaturated carbinol, namely 3, 7-dimethyl-i- (2 ', 6', 6'-trimethylcyclohex-i'-enyl) -nona-4, 6, 8-triene-i-yne -3-ols, which can be represented by the following structural formula and that is to be used in the synthesis of vitamin A.

It has been found that the new carbinol can be easily prepared by reacting 2, 6, 6-trimethyl - i - äthinylcycloh @ $ en-magnesium halide with '6-methylocta-3, 5,' 7-trien-2-one in . Presence of an inert solvent and subsequent decomposition of the magnesium compound formed; this reaction can be represented as follows: Organic solvents are used as inert solvents, preferably aliphatic ethers with 4 to 10 carbon atoms, e.g. Diethyl ether, dibutyl ether, tetrahydrofuran or dioxane; other inert solvents can be used in conjunction with these solvents if desired. Preferably the solvent used should be as dry as possible.

The first stage of the process is preferably carried out at temperatures from -3o to + 2o ', preferably in an inert atmosphere, e.g. B. in a nitrogen atmosphere carried out. It is generally desirable that a small amount of one Antioxidant; such as hydroquinone, is present.

The second stage of the process, the decomposition of the magnesium compound, can be carried out by suitable methods, e.g. B. using water, which may contain other reagents. The use of acidic reagents in the decomposition should preferably be avoided, as these cause a rearrangement of the carbinol can. The use of an aqueous solution of ammonium chloride is preferred for the decomposition that occurs at low temperatures, e.g. B. o ', be carried out can.

The halogen magnesium derivative of 2, 6, 6-trimethyl-i-äthinylcyclohexen can be prepared by customary methods; preferably by treating 2, 6, 6-trimethyl-i-äthinylcyclohexen with an alkyl Grignard reagent alkyl-Mg-X (where X has the meaning given), z. B. ethyl magnesium bromide. This reaction is preferably carried out at elevated temperatures of from 20 to 8o '. This reaction, too, is preferably carried out in an inert atmosphere and in the same solvent as is used for the first step of the process of the invention. It has been found that said new compound in the purest form obtained has the following properties of refractive index Light absorption. max. 271 and 281 m # L, inflection ....... 235 to 245, 1475, 1 263 and 625, E = 43700, 3740o and 1850o, respectively. It should be noted that these properties have been observed on the purest material that could be obtained and may vary according to the purity of the product.

2, 6, 6 - trimethyl - i - ethinylcyclohexene 'can be modified to any suitable Manner, e.g. by the method in the British patent specification 627453 6-Methylocta-3, 5, 7-trien-2-one can be made in any suitable manner will.

The invention is illustrated by the following embodiments: Example i 3 g of 2, 6, 6-trimethyl-i-äthinylcyclohexen in 15 ccm of dry ether are added to a solution of ethylmagnesium bromite (from 0.6 g of magnesium) in 2o'cem ether. The mixture is refluxed under nitrogen for 2 hours and then cooled in an ice bath. 3 g of 6-methylocta-3, 5, 7-trien-2-one in 15 cc of ether are then added dropwise with stirring. After stirring for 2 hours at 0 °, the mixture is decomposed with excess ammonium chloride solution and the ethereal layer is finely washed with water, dried and evaporated. The remaining brown oil, yield 5.8 g, showed absorption maxima at 271 and 238 m @,: EI cm 1058 and 697 and an inflection at 276 to 284 m # t In the case of a part distilled at 130 ° / 10-sec mm, the following was found: C 84.20 / 0; H 9.7 ° / 0. Calculated on C2., -, 21/0: C 84.5 °, '0; H 9.90 / 0.

Example 2 Use of tetrahydrofuran as a solvent. 2 g of i-ethynyl-2,6,6-trimethylcyclohexene in 7 cc of tetrahydrofuran were slowly added at -20 ° to a solution of ethylmagnesium bromide (made from 0.32 g of magnesium, 2.5 g of ethyl bromide in 15 cc of tetrahydrofuran) . The mixture was stirred overnight at room temperature in a nitrogen atmosphere, then cooled to -30 °; and a solution of 1.8 g of 6-methylocta-3, 5, 7-triene-2-ön in -io cc of tetrahydrofuran was added dropwise. After stirring for 2 hours at -3o0, the solution was allowed to warm to -iö °; and then a solution of 5 g of ammonium chloride in 15 cc of water was added to decompose the complex. The mixture was extracted with ether and the extracts washed with water and dried over anhydrous magnesium sulfate. -J) as Evaporation of the solvent in vacuo gave 2.9 g of 3, 7-dimethyl-i- (2 ', 6', 6'-trimethylcyclohex-i'-en'-i'-yl) -nona-4 , 6, 8-triene-i-in-3-oil as a, viscous 01, Ultraviolet Absorption: Inflection = 274 to 284 m # L = 937 ' max. = 271 m # t = 986; e 28 ooo Inflection = 238 mu = 530 i cm Example 3 Use of di-n-butyl ether as a solvent. The reaction was carried out exactly as in Example, with the only difference that di-n-butyl ether was used as the solvent in the reaction. 3 g of 3, 7-dimethyl-i- (2 ', 6', 6'-trimethylcyclohex-i'-en-i'-yl) -nona-4, 6, 8-triene-i-yn-3-01 were obtained as viscous 01 , 1 Ultraviolet absorption: max = 282 m # t = 965; E 26 400 max. = 271 m # L = 1144; E 32 8oo Inflection = 23o to 249 mp. = 566 i cm Example 4 Use of dioxane as a solvent. The Grignard compound of i-ethynyl-2,6,6-tremethylcyclohexene was prepared exactly as in Example 2 using diethyl ether as the solvent. 2 g of 6-methylocta-3, 5, 7-trien-2-one in 10 cc of dioxane were then slowly added at room temperature and the mixture was stirred for a further 2 hours. The decomposition of the complex with ammonium chloride and work-up as described above gave 1.5 g of 3, 7-dimethyl-i- (2 ', 6', 6'-trimethyl cyclohex-i'-en-i'-yl) - nona-4, 6, 8-trien-i-yn-3-ol as a viscous 01, i% Ultraviolet absorption: Inflection = 274 to 283 m # L = 412 max. = 271 m #t = 413; E 10 800 max. = 229 m (L = 700 11 cm

Claims (3)

PATENT CLAIMS: i. Process for the preparation of 3, 7-dimethyl-1- (2 ', 6', 6'-trimethylcyclohex-i'-enyl) -nona-4, 6, 8-trien-i-yn-3-o1 of the structural formula characterized in that 2, 6, 6-trimethyl-i-ethinylcyclohexene with an alkylmagnesium halide in the presence of an inert solvent is converted into the halogenomagnesium derivative of the general formula in which X is chlorine or bromine, converted, then reacted with 6-methylocta-3, 5, 7-trien-2-one in the presence of an inert solvent and then decomposed the magnesium compound obtained. 2. The method according to claim i, characterized in that that an aliphatic ether with 4 to 10 carbon atoms is used as the inert solvent, z. B. diethyl ether, dibutyl ether, tetrahydrofuran or dioxane or mixtures thereof, used with other inert solvents if necessary. 3. Procedure according to Claim i and 2, characterized in that the first stage of the process at a temperature of 2o to 8o ', the second stage at a temperature of -3o to + 20 ° in an inert atmosphere and in the presence of an antioxidant and the decomposition in the 3rd stage with an aqueous ammonium chloride solution is carried out at a low temperature of around 0 °.