DE2264663C3 - Unsaturated sulfoxides and process for their preparation - Google Patents

Description

SOR ²

wherein R ¹ . R ² and R have the preceding meaning, characterized in that an aromatic aldehyde of the formula

R-CHO

where R has the above meaning. with a sulfoxide of the formula

R ¹ SCH ₂ SOR ²

in which R ¹ and R ^{2 have} the meaning defined, reacts in the presence of a base at room temperature to 120 ° C. is

The present application relates to unsaturated sulfoxides of the general formula

RCH = C

SR ¹

SOR ²

40

wherein R ¹ and R ^{2 are} a C ₁ - to C, -alkyl or phenyl radical and R is a phenyl radical. which is optionally substituted by chlorine or C ₁ - to C ₃ -alkyl or methoxy groups, or is a methylenedioxy radical.

The invention also relates to a process for the preparation of unsaturated sulfoxides of the general formula _§Rl

RCH = C

ss

SOR ²

wherein [V. R ^: and R have the preceding meaning, which is characterized by. that one is an <-o aromatic aldehyde of the formula

R CIK)

where R has the above meaning. mn one Sulphoxide of formula 6s

R ¹ Sc .I ₂ SOR ²
wherein R ¹ and R ² are as defined above. in the presence of a base at room temperature up to! 20 "C.

The unsaturated sulfoxides according to the invention, in which R, R ¹ and R ^{2 are} as defined in claim 1, are suitable for an advantageous process for the preparation of arylacetic acids or their esters represented by the general formula

RCH ₂ COOR ³

in which R has the definition according to claim 1 and R ^{3 is} a hydrogen atom or an alkyl group. Some of the so accessible arylacetic acid derivatives are effective as pain relievers, anti-inflammatory and pyretolytic drugs and also as drugs! known for curing the diseases of humans and animals. They can also be used as fragrances and plant growth inhibitors. In addition, phenylacetic acid is used as such or in the form of its salts. Amides or esters (for example as potassium phenylacetate, methylphenylacetate or phenylacetamide) are used as the starting material for the production of penicillin. Phenylacetic acid is used to make phenylacetone, and some of the esters are used as fragrances. Several processes for the preparation of phenylacetic acids and their derivatives have been proposed in the past. For example, one typical method for the preparation of phenylacetic acid involves the hydrolysis of benzyl cyanide with sulfuric acid and water or an aqueous solution of sodium hydroxide with heating. Further, a typical method of making phenylacetic esters includes esterifying phenylacetic acid with the corresponding alcohols in the presence of a small amount of sulfuric acid.

The sulfoxides according to the invention open up a slight reaction with alcohols (or water) and direct production route for very useful products of high purity and high yields, what a multitude of alkaloids. Pharmaceuticals or fragrances is important; on the other hand require comparable known substances for their further processing, which is more laborious and complicated Work stages.

To explain the synthetic route opened with the sulfoxides according to the invention, reference is made to the The following reaction scheme I indicated, which compares the previously known access route to ethyl homopiperonyl ester and the new and much simpler route via an inventive one Sulloxyd shows (with regard to the difficulties of the known working method see E. R. S h e ρ a r d et al .. "Preparation of Some Analogs of Papaverine", J. Org. Chcm., Pages 568 to 576). The advantages of the invention Sulphoxides result from the smaller number of stages (starting from the same Starting material, fiperonal). but also: uis the problem-free process steps.

The processing of the inventive Sull'owde include! in one / one the implementation of a sulfoxide according to the invention according to claim 1 with water or alcohols of the general formula

R ¹ OlI

in the presence of a mineral acid; im a will here / u refer to the Dl-OS 22 4X 592.

The inventive method for production

jer unsaturated sulfoxides according to claim 2 can be carried out as follows:

The process involves making an aromatic aldehyde of the formula

R —CHO

wherein R is as in claim 1. with a sulfoxide of the general formula

R ¹ SCH ₂ SOR ²

wherein R ¹ and R ^{2 are} as defined in claim 1 to react in the presence of a base. Because of the sulfoxide bond in the "position, this sulfoxide is easily dehydrated and condensed with the formation of the unsaturated sulfoxide desired. This reaction must be carried out in the presence of a small amount of a base. The bases used are preferably relatively strong bases, for example alkali hydrides such as NaH. quaternary ammonium hydroxide, alkali hydroxide such as sodium hydroxide or potassium hydroxide. Sodium hydride and trimethylbenzylammonium hydrochloride. which is commercially available under the name "Triton B". represent particularly bexorzugle bases.

Reaction I.

CHO

r 'ι ■ - ? Y

(Piper inal

(Present registration.
see example 10)

CH-OH

SCH,

CH,

Turning a solvent can be carried out. In general, organic solvents can be used Solvents such as dimethylformamide. Tetrahydrofuran or dioxane can be used. The reaction runs glaii at room temperature to 120 C, however Temperatures of 50 to 80 C are particularly preferred. These Unsaturated Sulphoxides and the Process their preparation is explained in more detail in the following examples.

If the substituents R ¹ and R ^{2 are} the same groups in the unsaturated sulfoxide, the sulfoxide can be prepared particularly easily, and it can be seen that R ^! and R ^{2 are} not substituents in the arylacetic acid or its ester, which are the end product of Weiler processing. An unsaturated sulfoxide is particularly preferred. in which both R ¹ and R ^{2 are} methyl groups as this is easy to handle. Examples of the phenyl group represented by R are alkyl-substituted phenyls (rusts, such as methylphenyl, also chlorophenyl, methoxy- or dimethoxyphenyl and methylenedioxyphenyl.

B-.vüglich of the starting material R- ¹ OH to be used in further processing. Regarding the working conditions, catalysts and solvents to be observed, reference is also made to DT-OS 22 4 * 592.

CH ₂ CI

■ o

CHXN

NaCN

SOCH ₁

SCH,

CH ■ ---- ■■ C
/ ■ · .. SOCH,

H'H, O

CH ₁ COOH

■ - o

(DT-OS 22 48 592 see example A 12)

C)

C)

H ⁺ EtOH

Verestei

CH (O, Ft

usual procedure

through the discovery
opened proceedings

lomopipemnv 'acidic eth \ lesion

'• f

In addition, z. B. the pharmaceutical active ingredient DL-Dopa using the eifindungsgcmäße Produce substances without any problems (cf. Reaction Scheme II below). whereas the known ones To do this, working methods require extremely complicated and numerous stages

Reaction scheme Π

CH, O -NN

CH = C

SCH,

SO,

Reduction CH, O

OCH.,

OCH,

SCH,

^N - CH, CH

SOCH ₁

(see example 7)

H \ drolic decomposition

■■ - ■ · CHXHO

CH, O - *

OCH,
(Homoveratrumaldehvdl

i Stieckersehe synthesis

NH ₂
-C \ U - ■■ CW COOH

HO

OH

(Dl.-Dopal

example 1

2,572 g of methyl-methyl-methyl-methyl-sulfoxide. one methanolic solution of 3 ml of 40% trimethyl- 4> benzyl ammonium hydroxide (Triton B) and 3 ml of benzaldehyde were added to 5 ml of tetrahydrofuran, and the mixture was refluxed for 4 hours. After adding 100 ml of methylene chloride was the reaction mixture with dilute Sehwe- no washed acidic. The product was dried with anhydrous sodium sulfate and reduced under reduced pressure Focused pressure. The residue was purified by column chromatography (Siliciumdioxidgcl. Methylene chloride), where 3,994 g (91st (VO) < <1 -Methylsulfinyl-1-methylthio-Z-phenylethylene in The standard of a colorless liquid with a boiling point of 149 150 C yielded 0.08 mm Hg.

IR (undiluted!: 1062 cm \

NMR ICCl ₄ ): Λ 2.62s (3H). 2.26s (311). ".5I s il Hi. Ho 7.32 m (311). 7.85 m (2H).

MS (70 ev. 100 C): me 212 (M \ 7 ",, l. 197 (5%). 149 (10 (V ₁₁ ). 134 (%%). Llo HS" ,,). 115 | I4 ""). X9

Anal.w K, "11 ₁₁ OS,):

Rained. . C 56.65. H 5.72. S 30.33:
! ■ found ... C 56.56. H 5.7 (1.S 30.20.

Example 2

1.12 g of methylthiomethyl sulfoxide were dissolved in 10 ml of dioxane, and 1 ml of a 40 ° oigen aqueous Solution of Triion B and 1.25 ml of benzaldehyde were added and the mixture at 63 ° C. for 16 hours touched. After adding 100 ml of methyler chloride, 10 ml of water and 0.5 ml of concentrated hydrochloric acid were added added, which was shaken. The aqueous, separated from the organic layer Layer was extracted with 50 ml of methylene chloride. The extracted methylene chloride layer was mixed with the organic layer combined The combined layers were dried with anhydrous sodium sulfate, wt. was concentrated under reduced pressure. The dried product was chromatographed on the column (silica gel and methylene chloride), 2.00 g of l-methylsulfinyl-l-methylihio-2-phenylethylene revealed.

Example 3

2.29 g of methyl methylthiomelhyl sulfoxide were dissolved in 10 ml of tetrahydrofuran, and 4 (1/2 mg of sodium hyiliide were added while cooling with ice. The mixture was stirred for 45 minutes and 2.2 ml of benzaldehyde were added at hot - 7 () C. The mixture was 3 hours at 70 C and 1 hour at room

temperature stirred. 50 ml of methylene chloride were / ugeset / l and the insolubles by filtration severed. The filtrate was concentrated under reduced pressure and chromatographed on the column (Siliciumdioxidgcl and Melhyienchlorid). where ^ 1.804 g revealed.

He i s ρ i e I 4

2.41 ii Melhyl-melhylthiomethylsulfoxid were in 10 ml of dimethylformamide dissolved, and 515 mg of sodium hydride were added and the mixture was stirred for 2 hours 20 minutes. 2.5 ml of benzaldehyde were added, and the mixture was stirred for an additional 3 hours at room temperature. 50ml methylene chloride is were added and the mixture was filtered. The filtrate was concentrated under reduced pressure and on the column chromatography (silicon dioxide gel. Methylene chloride), 1,720 g (41.6% yield) of 1-methylsulfinyl-1-methylthio-2-phenylethylcn revealed.

Example 5

1.05 g of methyl methylthiomethyl sulfoxide were dissolved in 7 ml of dioxane, and 1.16 g of p-methoxyhenzaldehyde and 1 ml of a 40% strength aqueous solution of Triton B were added. The mixture was stirred at 80 ° C. for 23 hours. After the same treatment as in Example 2, the product on the column chromatographies was, where "884mg (63.8 ⁰ O yield) 1, (Siliciumdioxidgcl methylene chloride.) - methylsulfinyl -1 - methylthio - 2 - (p - gave mcthoxyphenyil-ethylene A. The sample was chromatographed again for analytical purposes.

IR (neat): 1059 cm " ¹ ... '5

NMR (CCl ₄ I: Λ 2.30 s (3 H). 2.63 s (3 H). 3.84 s (3 Hl. 6.86 d (2 H..! = 8.4 Hz). 7.86 d (2 H. J = 8.4 Hz) . λ43 s (IH).

Mass spectrum (70ev. 100 C): mc 242 (M * i 179 (base peak). 164 (96%). 149 (31% 1. 146 (28%).

Analysis (C ₁₁ HuO ₂ S;):

Calculated ... C 62.82. H 6.71. S 15.25:
found .... C 62.57. H 6.69. S 14.99.

45 Example 6

951 mg of methyl methylthiomethyl sulfoxide and 1.17 g of p-methoxybenzaldehyde were dissolved in 10 ml of tetrahydrofuran solved. 1 ml of a 40% strength methanolic solution of Triton B was added to this solution and the mixture is refluxed for 5 hours. Then 100 ml of methylene chloride. 5 ml Water and 2 ml of 9 η-sulfuric acid were added and the mixture was shaken. The one from the organic layer The separated aqueous layer was extracted again with 50 "ml of methylene chloride. The extracted Methylene chloride layer was combined with the organic layer. The combined phases were dried with anhydrous sodium sulfate and concentrated under reduced pressure. That concentrated 6a Product was chromatographed on the column (silicon dioxide sel. Methylene chloride), 1.51 g (100% yield) 1 - methylsulfinyl - 1 - methylthio-2- (p-methoxyphenyl) -ethylene revealed.

f> 5 example 7

1.078 g of methyl methylthiomethyl sulfoxide were "d 43 34Dih

benzaldehyde and 1 ml of a 4 () ", igcn aqueous solution Min Triton B was added and the mixture Stirred at SO C for 25 hours. The reaction product was treated in the same way as in Example 2 and on the column chromatography (Siüciumdioxidgel. Methyl chloride). 1,118 g (87.1% yield) of 1-methylsulfinyl-1-methyllhio-2- (3'.4'-dimethoxyphenyl) ethylene in the form of a colorless liquid.

IR (neat): 1055 cm '.

NMR (CDCl3,): Λ 2.31s (3H), 2.72s (3H). 6.9Od (1 H. J = 8.3 Hz). 7.46 d χ d (1 H, .1 - = 8.3 Hz, 2.4 Hz). 7.55 s (lH). 7.73d (1 H. 1 = 2.4 Hz).

Compute; ... C 52.91. H 5.92. S 23.55:
found C, 53.04. H 5.88. S 23.52.

Example 8

1,176 g of methyl methylthiomethyl sulfoxide were dissolved in 7 ml of dioxane, and 1.33 g of p-chlorobenzaldehyde and 1 ml of a 40% aqueous solution of Triton B was added. The mix was Stirred at 80 ° C. for 25 hours. When the procedure described in Example 2 was used, the result was 1190 mg (72.8% yield) 1-methylsulfinyl-1-methylthio-2- (p-chlorophenyl) ethylene.

IR (neat): 1062 cm " ¹ .

NMR (CCU): Λ 2.32 s (3H), 2.68 s (3H). 7.36d (2 H. J = 8.7Hz). 7.48 s (IH). 7.82d (2H..I = 8.7 Hz).

Analysis (C ₁₀ H ₁₂ OS ₂ Cl):

Calculated ... C 48.67, H 4.49:
found .... C 48.63. H 4.81.

Example 9

545 mg of phenyl-phenylthiomethylsulfoxide and 446 mg of p-chlorobenzaldehyde were in 5 rn! Tetrahydrofuran dissolved, whereupon 0.5 ml of a 40% methanolic solution of Triton B were added. The mixture was refluxed for 5.5 hours. 100 ml of methylene chloride were added and the reaction product is washed with dilute sulfuric acid and then with anhydrous Dried sodium sulfate. The product was concentrated under reduced pressure and the rest of the column chromatography (silica gel, methylene chloride). 708 mg of 1-phenylsulfinyl -1 - phenyithio - 2 - (p - chlorophenyl) - ethylene in the form of colorless crystals with a melting point from 87.5-89.5 C.

IR (KBr): 1042 cm ^M.

NMR (CCl ₄ ): Λ 7.06 s (5H). 715-7.80 m (9H). 7.98 s (IH).

Analysis (C ₂₀ H ₁₅ OS ₂ C1): H 4.08. S. 17.29; Calculated C. 64.76. H 3.85. S. 17.47. a found. C. 64.36.

.g Methylmyy

~ ml of dissolved dioxane and 1.43 si 3,4-dimethoxy-

Example 10

674 mg methyl methylthiomethyl sulfoxide. 895 mg of Piperonal and 0.7 ml of Triton B became 5 ml Tetrahydrofuran was added and the mixture was added Heated under reflux for 9 hours. 50 ml of methylene chloride was added and the reaction product was washed with dilute sulfuric acid. The organic layer was washed with anhydrous sodium sulfate dried and under reduced pressure

709 617/249

con / eniiieit. whereupon chromatography on the column was (silica gel. methylene chloride). 870 mg (81% yield) of 1-methylsulfinyl-1-methvltliio - 2 - (3'.4 '- melhylenedioxiphenvll - iiilnlen revealed. '

IR: 1058cm '(film).

NMR (in CDCI.,): Λ 2.34 s {}] {). 2.76 s (3Hl. 6.05 s (2 H). 6.87 d 11 H. 1 - 8 Hz). 7.30 d χ d (1 H. .1 - S and: H / I. 7.54s (IH). 7.75 d (IH. J = 2Hz). Analysis (C _n H ₁₂ OS,): ^IC

Calculated ... C 51.54. 114.72. S 25.02; found .... C 51.27. Il 4.65. S 25.20.

Example 11

Ii 2,650 g p-isopropylbenzaldehyde and 2,240 g

Methyl-niethylthiomethyl-sulfoxide was dissolved in 30 ml of tetrahydrofuran, and 2 ml of a 4 () "uigen methanolic solution of Triton B were added. The mixture was then heated and refluxed for 25 hours. 50 ml of methylene chloride were added and then with 20 ml of dilute 3 η-sulfuric acid. The organic layer was dried with potassium carbonate (anhydrous) and then concentrated under reduced pressure. The residue was separated by column chromatography (silica gel, methylene chloride), whereby 3.013 g of l-methylsulfinyl-I-methylthic- 2- (p-isoprop_viphenyI) ethene in the form of a pale yellow oily substance yielded: 68%. ^ ₀

IR (neat): 1063 cm " ¹ .

NMR (CDCI,) :,) 1.25 d <6H. .1 = 7 Hz). 2.28 s (3H). 2.270 s (311). 2.89 septet (1 H. J = 7Hz). 7.23 d (2 H. 1 = 7 Hz). 7.57 s (1H). 7.81 d (2H. J = 7 Hz). (The methyl signal of the geometric isomer was found at <■> 2.12 and λ 2.74.)

Example 12

1,058 g of m-toluylaldehyde and 1,587 g of isopropylisopropylthiomethyl sulfoxide were dissolved in 20 ml of tetrahydrofuran, and 1.5 ml of 40% methanolic Triton B solutions were added. The mixture was heated and refluxed for 16 hours. 100 ml of methyl chloride were added and then shaken with 20 ml of dilute 3N sulfuric acid. The organic layer was dried with potassium carbonate (anhydrous) and then under reduced Focused pressure. The residue was purified by column chromatography (silica gel. Methvler.chlorid) separated, with 1,945 g of 1-isopropylsulfinyl - 1 - isopropylthio - 2 - (m - tojyl) - ethylene resulted in the form of a light yellow oily substance. Yield: 78%.

IR (neat): 1063 cm " ¹ .

NMR (CDCI _-1 ): 1.04 d (3 H, J = 7 Hz). 1.21 d (3 H. J = 7Hz). 1.23 d (3 H. J = 7 Hz), 1.42 d (3 H. J = 7 Hz). 2.34 s (3H). 3.18 septet (1 H. J = 7 Hz). 3.28 Se - '. Ett (IH. J = 7Hz). 7.0 7.35 m (2H). 7.49 s ("1 H). 7.6 7.8 m (2 H).

The further processing of sulfoxides according to the invention is illustrated by the following examples.

At s ρ i e 1 A I

191 mg of 1-methylsulfinyl-1-methylthio-2-phenylethylene were dissolved in 1.5 ml of 1,2-dimethoxyethane as a solvent, and then 1 ml 36% hydrochloric acid added through the Heat evolved on addition of the concentrated hydrochloric acid. The unsaturated sulloxide around the water from the hydrochloric acid was removed 3 hours at room temperature. / u the reaction mixture obtained uurdcii ^ Oml Mcllnien ■ Chloride and 5 ml of water are added to the reaction extract product / u. The aqueous layer was separated off with 50 ml of methylene chloride extracted. The results from these 1 xlraktioncn Organic layers were combined and dried with anhydrous sodium sulfate and reduced under reduced pressure Focused pressure. After adding 30 ml of ether, the concentrated product was twice mil .Each 10 ml of a saturated aqueous solution of Natnumbi carbonate extracted. The other layer was changed only 3 times extracted with 30ml methyl chloride each time. the The organic layer was dried with anhydrous sodium sulfate to give 77 mg of a colorless one Crystals.

The yield was 63% (based on the unsaturated Starting sulfoxide; the yields listed below are also based on this Melting point of the product was 69 to 75 C. Evidenced by IR spectrum and mixed melting point the product proves to be identical to phenylacetic acid.

Example A2

300 mg of 1-methylsulfinyl-1-methylthio-2-phenylatnylene were dissolved in 10 ml of anhydrous ethanol and the solution was saturated with hydrogen chloride. This gas was introduced with ice cooling. The reaction was carried out for 8 hours at room temperature carried out and the reaction mixture under reduced Focused pressure. By columnar chromalographic Separation (silicon dioxide ^ !. benzene) gave 179 mg of ethylphenyl acetate in one yield of 77%.

Example A3

1 - methylsulfinyl - 1 - methylthio - 2 - (p - methoxyphenyD-ethylene was dissolved in 2 ml of 1,2-dimethoxyethane and 1 ml of concentrated hydrochloric acid was added at room temperature. The reaction was carried out for 15 hours at room temperature, and the reaction mixture was made with 50% ml ether extraniert, and the organic layer was extracted with an aqueous solution of potassium carbonate. the aqueous layer was extracted with Chlorwasser- t? ι "'/" ^a "= ^{esäuerl u"} d then extracted ³ 3 times with each 5OmI methylene chloride. the organic The layer was dried with anhydrous sodium sulfate, and then concentrated under reduced pressure to give 62 mg (yield 25%) of colorless crystals. The reaction product was recrystallized from a mixture of carbon tetrachloride and cyclohexane, whereby

Example A4

274 mg of 1-methylsulfinyl-1-methylthio-2- (p-methoxyphenyD-ethylene were dissolved in 10 ml of anhydrous ethanol, and the solution was washed with hydrogen chloride gas saturated with ice cooling. The reaction product was left overnight at room temperature allowed to stand and then concentrated under reduced pressure. The residue was through Separate structural chromatography (silicon dioxide

η-hexane to benzene = 1: 1 and benzene, where 20 (i mg of ethyl p-methoxyphenyl lacelate resulted.

Example A 5

260 mg of 1-methylsuH'myl-1 -meih \ lihio-2- (p-ch! Orphen \ l) -ether were dissolved in 10 ml of anhydrous ethanol and the solution was washed with hydrogen chloride gas saturated with ice cooling. The reaction mixture was left to stand overnight at room temperature. The product was then at reduced Concentrated pressure and chromatographs on the column (silicon dioxide gel. Benzene / u n-hexane = Γ. 1). 193 mg (yield 92.2 ",,) ethyl p-chlorophenyl acetate revealed. Da. ·, Product was determined by comparing the IR spectra with standard samples identified.

Example A 6

260 mg of 1-methylsulfinyl-mclhylthio-2- (3 ', 4'-dimethü.xyphcnyl) -ethylene were dissolved in 10 ml of anhydrous ethanol, and the solution was saturated with hydrogen chloride gas at room temperature. The temperature of the solution rose to about 50.degree. The reaction mixture was left overnight at room temperature left to stand and chromatographs on the column (silica gel. benzene), whereby 86 mg (yield 37.2%) of ethyl (3'.4'-dimethoxyphenyl) acetate revealed.

Example A 7

195 mg of 1-methylsulfinyl-1-methylthio-2- (3'.4-dimethoxyphenyl) -ethylcn were dissolved in 15 ml of anhydrous ethanol, and into the solution was taken Ice cooling hydrogen chloride gas introduced until see the solution turned yellow. The reaction mixture was left to stand at room temperature overnight and concentrated under reduced pressure. The residue was purified by column chromatography (silica gel, Benzene) separated, resulting in 69 mg (yield 40%) of ethyl (3 ', 4'-dimethoxyphenyl) acetate.

Example A X

ISO mg I - Phenylsullinyl-1-phenylthie> -2-ip-chlor-

phenyli-iitlnlen were dissolved in 10ml ethanol, and

The solution was cooled with (water-release gas saturated. The reaction mixture was sleiiengcl.issen and under overnight at room temperature concentrated under reduced pressure. The residue was chromatographed by column (silica gel, η-hexane and benzene) separated, giving 82 mg (90% yield) of ethyl p-clilorphenyl acetate.

Example A 9

The procedure of Example A2 was repeated, however, 254 mg of 1-methylsinyl-l-methylthio-2- (p-isopropylphenyl) ethylene were dissolved in 10 ml of ethanol. 171 mg were obtained (yield K3 "u | Ethyl p-isopropyl phenyl acetate.

Example AIO

The procedure of Example A 2 was repeated, except that 282 mg of 1-isopropylsulfmyl-1-isopropylthio - 2- (m-methylphenyl-ethyien were dissolved in 10 ml of butanol. 174 mg (yield 2s 84.5%) butyl-m-methylphenylaciate.

Example All

The procedure of Example A 1 was except that 100mg hydrobromic acid (specific \ o fish weight 1:48) and 360 mg 1-phenylsulfinyl-1 repeats - phenylthio - 2 - (p - chlorphenyi I - äthyien used were This gave 121 mg (72!. "» Yield) p-chlorophenylacetic acid.

Example A 12

522 mg of 1-methylsulfinyl-1-methylthio 2- (3'.4'-methylcndioxyphenyl) -ethylene were dissolved in 10 M ethanol, and hydrogen chloride gas was passed into the solution while cooling with ice until it turned yellow (after about 20 minutes). The reaction mixture; was concentrated under reduced pressure unc to the column chromatographies (Siliciumdioxydge! benzene) to give 386 mg ^ (91 "" yield) of ethyl (3'.4'-methylenedioxyphenyl) acetate yielded.

Claims (2)

Patent claims: 1. Unsaturated sulfoxides of the general formula RCH = C SR ¹ SOR ² wherein R ¹ and R ² a C ₁ - to C ₃ -AlkVl- or Phen> l radical and R a phenyl radical, which is optionally _{substituted by chlorine or C 1} - to C ₃ -AlTyI- or methoxy groups, or a Methyiendioxyphenyl- Rest means. 2. Process for the preparation of an unsaturated sulfoxide of the general formula RCH = C SR ¹