NO790342L - PROCEDURE FOR THE PREPARATION OF ALKYL-2-ARYLACRYLATE - Google Patents

Description

The present invention relates to a method for the production of alkyl-2-aryl acrylates with the general formula I

in which

1 2

R and R are the same or different and each represents hydrogen,

1 6

C to C alkyl, halogen, to alkoxy or haloalkyl, C 1 to C 4 alkylthio or haloalkylthio, or nitro;

or

R 1 and R 2 together form a methylenedioxy or halogen-methylenedioxy group;

or

1 2

R and R together with the benzene ring form a 2-naphthyl group;

~and

R 3 is one to C&alkyl group,

and the distinctive feature of the method according to the invention is that formaldehyde is reacted with a phenylacetic acid ester of the general formula II

in which

12 3

R , R , and R have the above meaning, in a polar solvent in the presence of a base.

These and other features of the method according to the invention appear in the patent claims.

Some of the compounds of formula I have previously been described as intermediates in the production of insecticidal substituted 1-phenylcyclopropane carboxylates, 1-phenylcyclobutane carboxylates and 1-(2-naphthyl)-cyclobutane carboxylates.

Monomeric acrylates of the general formula I can be used either alone or together with other polymerizable monomers for the production of useful polymers and they can also be used as intermediates in the production of other chemical compounds.

Known methods for the preparation of alkyl-2-aryl acrylates have consisted of a three-step method where a phenylacetic acid ester was first condensed with a di(lower)alkyl)oxalate in the presence of an alkali metal alcoholate to prepare an alkali metal enolate salt after which the salt was acidified to give the corresponding phenyloxaloacetate which was then reacted with formaldehyde under alkaline conditions to give the desired alkyl-2-phenylacrylate. The realization that forms the basis of the present invention is that it is possible to carry out the conversion of an aryl acetic acid ester into an alkyl-2-aryl acrylate in a single reaction step.

An alcohol alkoxide, an alkali metal or alkaline earth metal oxide, hydroxide, carbonate, bicarbonate or salt of an organic acid is advantageously used as a base. Nitrogen base can also be used.

The solvent may be any suitable polar solvent, e.g. dimethylformamide, dimethylsulfoxide, 1,2-dimethoxyethane, an ethylene glycol ether or ethanol.

Water may optionally be present and the formaldehyde may optionally be supplied as paraformaldehyde or as a solution of formaldehyde in water.

The preferred combination of solvent-base is dimethylformamide and potassium carbonate which gives the best yields of

etc. 2

acrylic acrylates when R and R are electron-donor groups. Amine bases and protonic solvents are preferred when R 1 and R 2 are electron-withdrawing groups.

The reaction can be carried out at normal atmospheric pressure. The reaction temperature depends on the nature of the substituents (R 1 , R 2 ) on the aryl ring, but will usually lie between room temperature and approximately 80°C.

The product aryl acrylates can be isolated using normal processing methods and can be processed further without special isolation.

The invention is illustrated by means of the following

examples of preferred embodiments.

General method for the production of alkyl-2-aryl acrylates

Alkylaryl acetate (formula.11) (0.1 mol) is dissolved in dimethylformamide (50 ml) and paraformaldehyde (0.2 mol), potassium carbonate (0.1 mol) and calcium oxide (0.1 mol) are added all at once or in portions in the course of 3 hours. The reaction temperature is kept at 40°C and the course of formation of the acrylate is followed by means of gas-liquid chromatography. When the starting material has disappeared (5 to 30 hours), the reaction mixture is dissolved in water and extracted with a solvent (ether or dichloromethane. By evaporating the solvent, practically pure acrylate is isolated. This can be further purified if necessary by means of chromatography through a short silica gel -(column}

EXAMPLE 1

Ethyl 2-(4-ethoxyphenyl)acrylate was prepared from ethyl-(4-ethoxyphenyl)acetate in 58.5% yield by the general method described above. NMR and IR spectral analysis of the product was identical to the analyzes for an authentic sample prepared via the alkali metal enolate method.

EXAMPLE 2

Ethyl 2-(4-(g,g,(3,[3-tetrafluoroethoxy)phenyl)acrylate was prepared from ethyl 4-(g,g,(3,(3-tetrafluoroethoxy)phenyl)acetate with 37% yield using the general method. Gas-liquid chromatography of the product gave a single peak. NMR spectrum corresponded to the desired structure: -S ppm:1.3 (triplet 3H),

4.35 (quartet 2H), 5.95 (singlet, 1H proton of the tetrafluoroethoxy group), 6.13 (doublet, 2H - CH2~9ruPPe in acrylate),

7.3 (multiplet 4H - aromatic protons).

EXAMPLE 3

Ethyl-2-(4-nitrophenyl) acrylate

Ethyl 4-nitrophenyl acetate (41.8 g) was slurried in 200 ml of ethanol, 38.5% aqueous formaldehyde solution (31.2 ml) and sodium bicarbonate (1 g) were added and the reaction mixture stirred for 3 hours at 55°C. Most of the ethanol was removed by evaporation and the remainder taken up in a 50/5G water/diethyl ether suspension. After separation, the ether layer was washed with water, dried over anhydrous sodium sulfate and evaporated to dryness to give a pale yellow viscous oil which was purified by chromatography on silica gel eluting with dichloromethane to give ethyl 2-(4-nitrophenyl)-acrylate in 10.5% dividend.

EXAMPLE 4

Ethyl- 2-(4-nitrophenyl) acrylate - Alternative method

Paraformaldehyde was slurried in 150 ml of 1,2-dimethoxyethane, piperidine (5 g) was added and the mixture heated to 70°C. Ethyl-(4-nitrophenyl)acetate (104.5 g) was added and the reaction continued for 20 hours. Most of the 1,2-dimethoxyethane was distilled off under reduced pressure and the remainder was taken up in ether and filtered. The filtrate was evaporated to dryness and purified by chromatography on silica gel eluting with dichloromethane to give a yellow solid 74.6 g (67%) after recrystallization.

EXAMPLE 5

Ethyl 2-(4-fluorophenyl)acrylate was prepared from ethyl-(4-fluorophenyl)acetate by the general method in_51% yield. The compound was obtained in the impure state. However, the NMR spectrum showed the presence of a doublet δ = 5.95 (2H) characteristic of the acrylate Ct 2 . The yield was confirmed by further conversion of the product to a difluorocyclopropane by reacting the acrylate with a difluorocarbene and subsequent purification and identification of the difluorocyclopropane.

EXAMPLE 6

Ethyl 2-(4-butoxyphenyl)acrylate was prepared from ethyl 4-butoxyphenylacetate in 35% yield using the general method. NMR spectrum corresponded to the desired structure: £ppm 1.4 multiplet (10H) (CH2 & CH3i butoxy and CH3i ethyl;

4.05 triplet (2H) (0-CH2- in butoxy); 4.43 quartet (2H)

(CH2 in ethyl); 6.05 doublet (2H) (CH2i acrylate); 7.45 multiplet (4H) (aromatic protons).

EXAMPLE 7

Ethyl 2-(4-methoxyphenyl)acrylate was prepared from ethyl 4-methoxyphenylacetate in 37% yield using the general method. NMR spectrum corresponded to the desired structure:

& ppm 1.35 quartet (3H) (CH3i ethyl); 3.80 singlet (3H)

(CH3 in methoxy); 4,2 quartet (2H) (CH2i ethyl); 6.05 doublet (2H) (acrylate CH2); 7.1 multiplet (4H) (aromatic protons).

EXAMPLE 8

Ethyl 2-(3,4-methylenedioxyphenyl)acrylate was prepared from ethyl-(3,4-methylenedioxyphenyl)acetate by the general method in 21% yield as a pale yellow oil. After removal of the solvent and starting material, the acrylate was not characterized as such, but was converted to the corresponding dichlorocyclopropane by reaction with a dichlorocarbene. NMR and IR spectrum of ethyl 1-(3,4-methylenedioxyphenyl)-2,2-dichlorocyclopropane carboxylate after purification corresponded to the desired structure..

EXAMPLE 9

Ethyl 2-(2-naphthyl)acrylate was prepared from ethyl 2-naphthyl acetate by the general method in 41% yield. NMR spectrum of the product purified by chromatography showed the presence of a doublet 6 = 6.13 ppm (2H) characteristic of the acrylate CH 2 . The structure of the product was further confirmed by conversion to ethyl 1-(2-naphthyl)-2,2-difluorocyclopropane carboxylate by reaction with a difluorocarbene. The 2-naphthyldifluorocyclopropane carboxylate was identical to an authentic sample.

Claims (6)

1. Process for the preparation of alkyl-2-aryl acrylates of the general formula I in which 1 2 R and R are the same or different and each is either hydrogen, C 1 to C 1 alkyl, halogen, C 1 to C 6 alkyl or C to C 6 halogeno alkoxy, C to C alkylthio or haloalkylthio, or nitro, or R 1 and R 2 together form a methylenedioxy or halogen-methylenedioxy group; or 1 2 R and R together with the benzene ring form a 2-naphthyl group; and R 3 is a to C, alkyl group, characterized in that formaldehyde is reacted with a phenylacetic acid ester of the general formula II 12 3 wherein R , R , and R have the above-mentioned meaning, in a polar 16sing agent 1 in the presence of a base. 2. Procedure as stated in claim 1, characterized by the fact that a alcohol alkoxide, an alkali metal or alkaline earth metal oxide, hydroxide, carbonate, bicarbonate or a salt of an organic acid or a nitrogen base. 3. Method as stated in claim 1 or 2, characterized in that the solvent used is dimethylformamide, dimethylsulfoxide, 1,2-dimethoxyethane, an ethylene glycol ether, or ethanol. 4. Method as specified in claims 1 to 3, characterized in that the formaldehyde is supplied as paraformaldehyde or as a solution of formaldehyde in water. 5. Method as stated in claim 1, in which the one or 1 2 both of R and R are electron-donor groups, characterized in that dimethylformamide is used as solvent and that potassium carbonate is used as base. 6. Process as stated in claim 1, in which one or both of the groups R <1> and R 2 are electron-accepting groups, characterized in that a protonic solvent is used as solvent and an amine is used as base.