CS276700B6 - A method of preparing styrene methoxy derivatives - Google Patents

Abstract

The methoxy derivatives of styrene of the general formula I, where R = H, CH3O, are prepared by intramolecularly eliminating water from the methoxy derivative of phenylethyl alcohol of the general formula II, where R has the meaning already given, under reflux of a solvent, for example xylene, nonane, propylbenzene, decane, for 30 minutes to 3 hours, in the presence of anhydrous copper sulfate and optionally with the addition of a polymerization inhibitor, for example p-tert-butylpyrocatechin.

Description

The invention relates to a process for the preparation of styrene derivatives characterized by the presence of two or three methoxyl groups on the benzene nucleus by dehydration of the corresponding phenylethyl alcohols. ·

Process for the preparation of 3,4,5-trimethoxystyrene, consisting in intramolecular elimination! water from the corresponding phenylethyl alcohol derivative in the presence of freshly remelted potassium bisulfate as an acid catalyst (U.S. Pat. No. 3,637,662) is not only non-reproducible but also denied in the literature, pointing out that under such conditions the preferred formation of the corresponding diaryl ethers (Naturwiss ., 44, 1957, W. Kleeberg, G. Suchardt, Observations on the Dehydration of Arylmethylcarbinole, p. 584). By dehydration of the corresponding phenylethyl alcohol in the absence of an acid catalyst, RL Frank et al. Prepared in 18 'yield 3,4-dimethoxystyrene (J. Am. Chem. Soc., 68, 1946, RL Frank, CE Adams, RE Allen, R. Gander). , PV Smith, Alkoxy- and Aryloxystyrenes, pp. 1365-1368).

Principle of the process for the preparation of trimethoxystyrenes of general formula I ch = ch ₂ ώ ^(I)

R ^ X ^ _OCH3 0CH ₃ wherein the radical R = H, C ^ H, wherein the radical R is substituted in position 5, the invention consists in the fact that the secondary trimetoxyfenyletylakohol of formula II it CHCH ₃

0CK _{3 OCH3} wherein R is as defined above, is treated with refluxing solvent of boiling point 140-174 DEG C. in the presence of anhydrous copper sulfate, optionally with addition of polymerization inhibitor, refluxed for 30 minutes to 3 hours, the insoluble component was removed, the solution concentrated and subsequently distilled at a pressure of 100 to 900 Pa. Xylene, nonane, propylbenzene or decane are used as the refluxing solvent with a boiling point between 140 and 174 ° C.

According to the invention, the methoxyl derivative of the secondary phenylethyl alcohol is dehydrated intramolecularly, the reaction being easily controlled by determining the water in the separator. Yields are up to 85%. If the styrene derivatives obtained are not used as an intermediate within 48 hours, they must be stabilized by the addition of a polymerisation inhibitor, which can be separated by distillation at a pressure of 100 to 900 Pa before use.

Examples of embodiments of the invention

Example 1

Pour 100 ml of xylene and add 1.6 g of anhydrous copper sulphate to a 250 ml flask equipped with mechanical stirring, an addition funnel with an elongated stem and a water condenser with a low condenser, placed in a laboratory heating nest. It is refluxed for 10 minutes at a boiling point of xylene of 140 ° C, during which time water is removed via a separator if copper sulphate contains traces of water. Then 53 g (0.25 mol) of 1- (3,4,5-trimethoxyphenyl) ethyl alcohol are added dropwise over 30 minutes and constant reflux is maintained by heating throughout the reaction time. The reaction is complete when no more water is excreted. The total reaction time, including dropwise addition, is 3 hours. The insoluble component is filtered off from the reaction mixture, the filtrate is concentrated at 5 kPa and the crude product is distilled off at 100 Pa. The purity of the product is checked by thin-layer chromatography in a solvent system of ethyl acetate with benzene in a volume ratio of 1: 3, visibility of spots

CS 276700 B 6 iodine vapors. The retention factor R _f is 0,85 for 3,4,5-trimethoxystyrene, 0,25 for 1- (3,4,5-trimethoxyphenylethyl alcohol and 0,60 for diaryl ethers) to give 42 g of 3,4,5-trimethoxystyrene ( 85% yield) in the form of a syrup with a boiling point of 99-101 ° C at a pressure of 100 Pa.

Elemental analysis for molecular weight ’194.23 calculated: 67.96 wt. % carbon, 7.27 wt. % hydrogen, ...

found: 67.30 wt. % carbon, 7.48 wt.% hydrogen.

Example 2

The procedure is as in Example 1, except that decane is used as the solvent with a boiling point of 174 DEG C. and 0.1% by weight is added to the reaction mixture. % of p-tert-butylpyrocatechin, based on the theoretical amount of 3,4,5-trimethoxystyrene formed as polymerization inhibitor. 3,4,5-trimetoxystyrén liquid was obtained in a yield of 80 ⁹ jnonr. However, the reaction time is reduced to 30 minutes.

Example 3

The procedure is as in Example 1, except that 1- (3,4-dimethoxyphenyl) ethyl alcohol is used in an amount of 46 g (0.25 mol). 35 g (85% yield) of 3,4-diniethoxystyrene are obtained in the form of a liquid, b.p. 113 DEG-115 DEG C. at 900 Pa.

Elemental analysis for 'θΐθ ^ υίονί' 164.2 calculated: 73.15 wt. % carbon, 7.37 wt. % hydrogen, found: 72.82 wt. % carbon, 7.04 wt. % hydrogen.

The styrene methoxy derivatives prepared by the process of the invention are important intermediates for the preparation of styrene oxides as well as biologically active mescaline and adrenaline derivatives which have utility in biochemistry, molecular biology, medical sciences such as e.g. model substances in the study of nerve excitation transmission by the adrenergic system.

Claims (2)

CS 276700 8 6 2 iodine vapor. The retention factor Rf is 0.85 for 3,4,5-trimethoxystyrene, 0.25 for 1- (3,4,5-trimethoxyphenyl) ethyl alcohol and 0.60 for diaryl ethers. There are obtained 42 g of 3,4,5-trimethoxystyrene (85% yield) as a syrup having a boiling point of 99 to 101 ° C at a pressure of 100 Pa. Elemental analysis for molecular weight 194.23 calculated: 67.96 wt. % carbon, 7.27 wt. % hydrogen, found: 67.30 wt. % carbon, 7.48 wt. -S hydrogen. EXAMPLE 2 The procedure of Example 1 was followed except that decane was used as the solvent at boiling point 174 DEG C. and 0.1 wt. % of p-tert-butylpyrocatechin based on the theoretical amount of 3,4,5-trimethoxystyrene formed as an inhibitor of polymerization. The liquid 3,4,5-trimethoxystyrene is obtained in an 80% yield. However, the reaction time is shortened to 30 minutes. EXAMPLE 3 The procedure of Example 1 was followed except that 1- (3,4-dimethoxyphenyl) ethyl alcohol was used in an amount of 46 g (0.25 mol). 35 g (85% yield) of 3,4-dimethoxystyrene are obtained in the form of a liquid having a boiling point of 113-115 ° C at a pressure of 900 Pa. Elemental analysis for molecular weight 164.2 calculated: 73.15 wt. % carbon, 7.37 wt% hydrogen, found: 72.82 wt. % carbon, 7.04 wt. % hydrogen. Styrene methoxy derivatives prepared according to the invention are important intermediates for the preparation of styrene oxides as well as biologically active derivatives of mescaline and adrenaline, which are used in biochemistry, molecular biology, medical sciences such as modeling agents in the study of nerve excitation by the adrenergic system. PATENT CLAIMS A process for the preparation of methoxy derivatives of styrene of formula I (I) wherein R = H, CH 3, wherein the radical R is substituted at the 5-position, characterized in that the trimethoxyphenylethyl alcohol of formula II (II) wherein R is as defined above, a refluxing solvent having a boiling point of 140 DEG-174 DEG C. is treated in the presence of anhydrous copper sulfate, optionally with a polymerization inhibitor, refluxing for 30 minutes to 3 hours, the insoluble component being separated, the flow is concentrated and subsequently distilled at 100 to 900 Pa. 2. A process for the preparation of methoxy derivatives of styrene of the formula I according to claim 2, characterized in that the refluxing solvent is a solvent having a boiling point of 140 to 174 ° C, preferably xylene, nonane, propylbenzene or decane.