IE41999B1 - Preparation of 6,11-dihydro-11-oxodiben(b,e)-oxepin-alkanoic acids - Google Patents

Abstract

6,11-Dihydro-11-oxodibenz[b,e]oxepinealkanoic acids of the formula I are prepared from dicarbonyl halides of the formula II which are converted into oxepinealkanoyl halides which are then hydrolysed to compounds of the formula I. The symbols in the formulae have the meaning stated in Claim 1. The reaction is carried out either with a Lewis acid in the presence of solvents at 0 DEG C to room temperature or in the presence of iron chloride without solvent at temperatures from 100 to 150 DEG C. The compounds of the formula II can be prepared by treating the corresponding dicarboxylic acid with a mixture of thionyl chloride and iron chloride at room temperature to the boiling point of the reaction mixture. The compounds of the formula I have anti-inflammatory and analgesic effects.

Description

This invention relates to a method for the preparation of 6,11 - dihydro - 11 - oxodibenz/b,e/oxepin alkanoic acids, which have anti-inflammatory and analgesic activity.

The methods described in the prior art for the production of these compounds result in side reactions, polymerization and in substantially lower yields, than can be achieved with the method of the invention. An article by K. Stachand H. Spingler, Monatshefte Chem., Bd. 9_3, 1962 and German Patent Specification No. 1,279, 682 of Stach and Spingler disclose that cyclization of an a - phenoxy - o - toluic acid under drastic conditions, for example, by prolonged heating with thionyl chloride at an elevated temperature of about 160°C, provides the 6,11 - dihydro - 11 - oxodibenz/b,e7 - oxepine, but with substantially lower yields than can now be attained. The above prior art also discloses the cyclization of monoacid chlorides of the formula COCI - 3 wherein R is a methyl or methoxy group or a chlorine, bromine or hydrogen atom at elevated temperatures (13022O°C), to give a corresponding oxepin.

Furthermore, it has been proposed to cyclise a 5 compound acid of the formula by treatment with a dehydrating or condensing medium, for example, polyphosphoric acid, ethanol - phosphorous pentoxide, phosphoric anhydride, anhydrous trifluoro10 acetic acid, or sulphuric acid with or without a solvent at a temperature of from about 20 to 150°C.

This cyclization is disclosed in Belgian Patent Specification No. 818,055, published November 18, 1974 of Ueno, el al.

The present invention provides a process for the manufacture of a 6,11 - dihydro - 11 - oxodibenz/b,e/oxepin - 2 - or 3 - alkanoic acid, which comprises reacting a compound of the general formula I COX (I) - 4 1 2 wherein R and R , which may be the same or different, each represents a hydrogen atom or a methyl group, .X represents a chlorine, bromine or fluorine atom, each Y represents an alkyl group having up to 4 carbon atoms, an alkoxy group having up to 4 carbon atoms, a halogen atom or a trifluoromethyl group, n represents 0, 1 or 2, and the -C——COX group is on the 3- or 4-position of the phenyl ring, with a Friedel-Crafts catalyst and hydrolysing the resulting oxepin alkanoyl halide.

The resulting acid has the general formula 2 in which R , R , Y and n have the meanings given above, 12 » *— and the -CR R COOH group is in the 2- or 3-position.

Compounds of the general formula (III) are described and claimed in Patent Specification No. 39835.

In this method a diacid halide is cyclised as opposed to a monoacid chloride as described by Stach and Spingler, and the yields obtained are considerably higher than in the processes previously proposed, frequently being over 90% and even approaching 100% in certain cases.

It is unusual and unexpected that under the conditions of this invention apparently only intramolecular cyclization is observed. The anticipated and equally possible intermolecular Friedel-Crafts reaction does not apparently occur, and it is thought that this absence of intermolecular reactions permits the excellent yields of the products of this invention.

Furthermore, prior art methods of preparing 6,11 dihydro - 11 - oxodibenz/b,e/oxepin - 3 - alkanoic acids have the disadvantage that generally both the 3 alkanoic and the 1 - alkanoic acid isomers are formed. This can be seen in Example 6 of the afore-mentioned Belgian Patent Specification, and although the method described therein is not regio specific, the method of the invention has been surprisingly found to be regio specific and thus enables the attainment of a 3 - alkanoic acid without the simultaneous production of the 1 alkanoic acid to any measurable extent.

The diacid haldide of formula I may be prepared by treating the corresponding dicarboxylic acid. of the general formula II COOH (II) 1' 9 wherein R , R, y and n are as defined above with a halogenating agent, for example, a thionyl halide or a phosphorus pentahalidc in the presence or absence of a solvent or diluent. The reaction is carried out, for example, at a temperature from ambient to the boiling point of the reaction mixture for 15 minutes to four hours.

In a preferred mode of carrying out the process of the invention, the starting material of formula I is reacted with one of the usual Lewis acid catalysts used in Friedel-Crafts reactions, e.g. aluminium chloride, stannic chloride or ferric chloride, at a low temperature of about 0°C to ambient temperature, preferably 5 to 15°C, in the presence of a suitable solvent, preferably 1,2 - dichloroethane. The catalyst may be used in any amount from 1 mole to 0.1 mole per mole of diacid halide.

Irrespective of the absence of intermolecular reaction it is surprising that high yields may be achieved by utilizing very small amounts of a Lewis acid catalyst. One skilled in the art would anticipate that completion of a Friedel-Crafts reaction would require the molar ratio of acyl group to catalyst to be about 1:1. Accordingly, it is rather surprising that the high yields disclosed herein can be achieved utilizing as little as 1/lOth mole of catalyst per mole of acyl group.

The diacid halide used as the starting material in the above preferred embodiment is preferably a compound of formula I in which X represents a chlorine atom.

Y represents one chlorine atom (ie. n=l), or n represents 1 2 and R and R each represents a hydrogen atom.

Ih another preferred mode of carrying out the process of the invention, a diacid halide of formula I is heated with ferric chloride at a temperature within the range of from 100 to 150°C and the resulting oxepin alkanoyl halide is then hydrolysed to give the desired acid. The Friedel-Crafts reaction temperature is pre41999 ferably from 110 to 120°C and the reaction time is, for example, 10 minutes to 24 hours.

Xn a variant of this preferred embodiment, a dicarboxylic acid of the general formula II is reacted with a thionyl halide, preferably thionyl chloride containing small amounts of iron, generally several and preferably 60 parts per million, at a temperature of from ambient to the boiling point of the reaction mixture, then the reaction mixture is heated to a temperature of from 100 to 150°C, preferably 110 to 120°C.

In the dicarboxylic acid of formula I, n is preferably and R and R preferably both represent hydrogen atoms. In this process, the thionyl halide converts the dicarboxylic acid to the corresponding halide, and the thionyl halide/iron component acts as the FriedelCrafts catalyst. This variant is advantageous because the diacid halide is formed in situ, and one set of reagents is used for both steps.

It is surprising that high yields of the cyclic alkanoic acids can be achieved under the rather drastic conditions used in the two variants of the second preferred process, ie. temperatures of from 100 to 150°C because it is recognised that a common cause of poor yields in the Friedel-Crafts cyclization of acid chlorides is drastic reaction conditions (FriedelCrafts and Related Reactions, Edited by George A. Olah, Interscience Publishers, New York ¢1964), at page 912). This is illustrated by the lower yields reported in the above-mentioned prior art.

It will be readily appreciated by those skilled in the art that yields in all cases are dependent upon time of reaction and temperature and particular derivative involved.

The preferred variant of the process of the invention is that described first, the preferred diacid - 8 halides are the chlorides and preferred compounds prepared by the process of the present invention are 6,11 - dihydro - 11 - oxodibenz/b,e7oxepin - 2 - acetic acid and 6,11 - dihydro - 11 - oxodibenz/5,§7oxepin 5 3 - acetic acid. Other useful compounds are 6,11 dihydro - a - methyl - 11 - oxodibenz/b,e7oxepin - 2 acetic acid, 6,11 - dihydro -a - methyl - 11 oxodibenz/E/S/oxepin - 3 - acetic acid and 8 - chloro 6,11 - oxodibenz/b,£7oxepin - 2 - acetic acid.

IO The following Examples illustrate the invention.

EXAMPLE!t To 16 ml of thionyl chloride is added 28.6 g of 4-(2- carboxy - benzyloxy)phenylacetic acid and the mixture is slowly heated to reflux and allowed to reflux for one hour. The excess thionyl chloride is removed under reduced pressure at 90°C to provide a diacid chloride as an oil. The oil is dissolved in 160 ml Of 1,2 - dichloroethane and cooled to a temperature of 5° to 10°C. To the reaction mixture is added 14.1 g of anhydrous aluminium chloride and the mixture is stirred for 90 minutes at 5° to 10°C. The mixture is poured onto ice and stirred for one hour, extracted with chloroform and the chloroform removed to provide an oil. The oil is taken up in a 15% sodium hydroxide solution and heated for 30 minutes. The Solution is acidified and extracted with chloroform to provide 25.6 g of 6,11 - dihydro 11 - oxodibenz/S,e7oxepin - 2 - acetic acid (95.5%), which is identical with an authentic sample by thin layer chromatography, nuclear magnetic resonance, and mixed melting point determination.

EXAMPLE 2: A diacid chloride is prepared according to the procedure of Example 1 from 340 ml of thionyl chloride which contains 60 PPM of iron and 400 g of 4 - (2 carboxybenzyloxy)phenylacetic acid. The diacid chloride is heated at a temperature of from 110° to 120°C, for 2 hours, under nitrogen. The reaction mixture is cooled and 1500 ml of water is added and heated to 65°C to effect hydrolysis. After hydrolysis is completed, the oily product is dissolved in a 20% solution of sodium hydroxide at 50-55°C, and the solution is brought to a pH of 1 with 6N hydrochloride acid. The acidified solution is cooled to 10°C, the resultant precipitate filtered, washed with water, collected and dried to provide 362 g (96.5%) of 6,11 - dihydro - 11 - oxodibenz/b,e7oxepin - 2 - acetic acid, which is identical with an authentic sample by thin layer chromatography, nuclear magnetic resonance and mixed melting point.

EXAMPLE 3: To 20 ml of thionyl chloride is added 20 g of 4 (2 - carboxybenzyloxy)phenylacetic acid and the mixture is slowly heated to reflux and allowed to reflux for 2 hours. The excess thionyl chloride is removed under reduced pressure at 90°C to provide a diacid chloride as an oil. The oil is dissolved in 75 ml of 1,2 dichloroethane, cooled to ambient temperature and to the cooled solution is added 1.82 g of stannic chloride. The reaction mixture is stirred for 4 hours at ambient temperature and then poured onto 35 g of ice. The resulting mixture is stirred for 1 hour and the biphasic mixture separates. The organic phase is collected and then concentrated under pressure to provide an oily solid which is poured into 200 ml of water and the aqueous mixture is heated to 60°C, which hydrolyses the mono acid chloride to the free acid. The acid is neutralized with caustic soda solution, treated with 0.4 g of charcoal and 0.4 g of celite and filtered. The clear filtrate solidifies upon the addition of 12N - 10 hydrochloric acid and the solid precipitate collected by filtration, washed with water and dried under reduced pressure to provide 17.2 g of 6,11 - dihydro 11 - oxodibenz/b,e7ozepin - 2 - acetic acid (91.4%).

EXAMPLE 4: To 80 ml of thionyl chloride is added 80 g of 4-(2- carboxybenzyloxy)phenylacetic acid and the mixture is slowly heated to reflux over a 2 hour span and allowed to remain at reflux for 2 hours. The excess thionyl chloride is removed under reduced pressure at 90°C to provide the diaeid chloride. The diaeid chloride . is dissolved in 250 ml of 1,2 - dichloroethane, cooled to 1O°C, and to the cooled solution is added 3.73 g of aluminium chloride. The reaction mixture is stirred at 10°C for 4 hours and then poured onto 250 g of ice. The resulting mixture is stirred for 1 hour and the biphasic mixture separates. The organic phase is collected and then concentrated under reduced pressure to provide an oily solid which is poured into 500 ml of water and the aqueous mixture is heated to 60°C which hydrolyzes the mono acid chloride to the free acid. The acid is neutralized by addition of caustic soda solution and this solution is treated with 2.4 g of charcoal and 2.4 g of celite and filtered. The clear filtrate solidifies upon addition of 12 N hydrochlorici acid and the resulting solid precipitate is washed with water and dried under reduced pressure to provide 72.5 g of 6,11 - dihydro - 11- oxodibenz/E,e7oxepin - 2 - acetic acid (96%).

EXAMPLE 5: To 10 ml of thionyl chlroide is added 5.1 g of 3-(2- carboxybenzyloxy)phenyl acetic acid and the mixture is slowly heated to reflux and allowed to remain at reflux for 2 hours. The excess thionyl chloride is - 11 removed under reduced pressure at 90°C to provide the diacid chloride. The diacid chloride is dissolved in 25 ml of 1,2 - dichloroethane, cooled to between 10 and 15°C and to the cooled solution is added 0.2 g of aluminium chloride. The reaction mixture is stirred at between 10 and 15°C for 4 hours and then poured onto 25 g of ice. The resulting mixture is stirred causing the biphasic mixture to separate. The organic phase is collected and concentrated under reduced pressure, to provide the mono acid chloride. The acid chloride is poured into water and heated to 60°C which hydrolyzes the acid chloride to the free acid. The acid is neutralized with caustic soda solution and the solution clarified by treatment with 0.15 g of charcoal and 0.15 g of celite. Reacidification of the clear solution with 12 N hydrochloric acid causes a solid to form which is collected by filtration, washed with water and dried under reduced pressure to provide an off-white crystalline product. Nuclear magnetic resonance spectra and thin layer chromatography confirms the presence of the desired 6,11 - dihydro - 11 - oxodibenz/b,47oxepin - 3 acetic acid and the absence of the less desirable 6,11 dihydro - 11 - oxodibenz/b,e7oxepin - 1 - acetic acid.

By following the procedures of Examples 1 through 5 the following compounds are produced in good yields: 6,11 - dihydro - n - methyl - 11 - oxodibenz/B,e7oxepin - 2 - acetic acid; 6,11 - dihydro - a - methyl - 11 - oxodibenz/b,§7oxepin - 3 - acetic acid; - chloro - 6,11 - dihydro - 11 - oxodibenz/b,e7oxepin - 2 - acetic acid; 6,11 - dihydro - α,a - dimethyl - 11 - oxodibenz/b,e7oxepin - 2 - acetic acid; and - 12 6,11 - dihydro - 9 - trifluoroinethyl - 11 oxodibenz/b,e/oxepin - 2 - acetic acid.

Claims (2)

1. 2 in which R , R , Y and n have the meanings given in claim 1, whenever prepared by a process as claimed in any one of claims 1 to 18. 20. 6,11 - dihydro - 11 - oxodibenz/S,£7oxepin 3 - acetic acid, whenever prepared by a process as claimed in any one of claims 1 to 18. - 16 21. 6,11 - dihydro - 11 - oxodibenz2E,e7oxepin 1 2 0 and R and R each represents a hydrogen atom. 11. A process as claimed in claim 9, wherein the compound of formula I as defined in claim 9 is reacted with aluminium chloride in 1,2 - dichloroethane at a temperature of from 5 to 15°C. 12. A process as claimed in claim 1, wherein the compound of formula I is reacted with ferric chloride at a temperature within the range of from 100 to 150°C. 13. A process as claimed in claim 1 or claim 12, wherein the compound of formula I is prepared and reacted in situ by reacting a dicarboxylic acid of the general formula II Yn R,1 C-COOH (II) - 15 with a thionyl halide and iron at a temperature within the range of from ambient to the boiling point of the reaction mixture and heating the resulting diacid halide of formula II to a temperature within the range of from 100 to 150°C. 14. A process as claimed in claim 13, wherein the thionyl halide is thionyl chloride. 15. A process as claimed in claim 13 or claim 14, wherein the amount of iron present is 60 ppm. 16. A process as claimed in any one of claims 12 to 15, wherein the temperature is from 110 to 120°C. 17. A process as claimed in any one of claims 12 to 15, wherein in the compound of formula I X represents 1 2 a chlorine atom, n represents 0 and R and R each represents a hydrogen atom. 18. A process as claimed in claim 1, carried out substantially as described in any one of the Examples herein. 19. A 6,11 - dihydro - 11 - oxodibenzy5,6/oxepin 2 - or 3 - alkanoic acid of the general formula COOH (III) 1 2 wherein R and R , which may be the same or different, each represents a hydrogen atom or a methyl group, X represents a chlorine, bromine or fluorine atom, each Y represents an alkyl group having up to 4 carbon atoms, an alkoxy group having up to 4 carbon atoms, a halogen atom or a trifluoromethyl group, n represents 0, 1 or 1 2 2, and the -CR R COX group is in the 3- or 4-position of the phenyl ring, with a Friedel-Crafts catalyst and hydrolysing the resulting oxepin alkanoyl halide. 2. A process as claimed in claim 1, wherein the compound of formula I is reacted with a Friedel-Crafts catalyst at a temperature of from 0°C to ambient in a solvent. 3. A process as claimed in claim 2, wherein the solvent is 1,2 - dichloroetrane. 4. A process as claimed in claim 2 or claim 3, wherein the temperature is from 5 to 15°C. 5. A process as claimed in any one of claims 2 to 4, wherein the Friedel-Crafts catalyst is aluminium chloride, stannic chloride or ferric chloride. 6. A process as claimed in any one of claims 2 to 5, wherein from 1.0 to 0.1 mole of the Friedel-Crafts catalyst is used per mole of the compound of Formula I. 7. A process as claimed in claim 6, wherein 0.1 mole of catalyst is used. 8. A process as claimed in any one of claims 2 to 7, wherein in the compound of formula I X represents a chlorine atom. 9. A. process as claimed in any one of claims 2 to 8, wherein in the compound of formula 1 n represents 1 and Y represents a chlorine atom. 10. A process as claimed in any one of claims 2 to 8, wherein in the compound of formula ϊ n represents

1. A process for the manufacture of a 6,11 dihydro - 11 - oxodibenz/Έ,§7oxepin - 2 or 3 - alkanoic acid which comprises reacting a compound of the general formula I

2. - acetic acid, whenever prepared by a process as claimed in any one of claims 1 to 18.