Diketones

(a) Field of the Invention

This invention relates to novel beta-diketones substituted by an aryl-aliphatic group in which the aliphatic chain is interrupted by a cyclic group, to the preparation thereof, and to compositions and methods for the use thereof as antiviral agents.

(B) Description of the Prior Art

J. S. Collins U.S. Pat. No. 3,917,718, issued Nov. 4, 1975, discloses compounds useful as pesticidal and antiviral agents and having the formula ##STR1## wherein Ar is phenyl or substituted phenyl, Alk is alkylene of 6-10 carbon atoms and R is lower-alkyl.

J. C. Collins and G. D. Diana U.S. Pat. No. 4,031,246, issued June 21, 1977, discloses compounds useful as pesticidal and antiviral agents and having the formula ##STR2## wherein Ar is phenyl or substituted phenyl, Alk is alkylene of 3-10 carbon atoms and R is lower-alkyl.

Neither of the above prior art patents shows any compounds wherein the alkylene bridge (Alk) is interrupted by a cyclic group.

In a composition of matter aspect, the invention relates to beta-diketones substituted on the carbon atom between the carbonyl groups by an aryl-aliphatic group in which the aliphatic chain is interrupted by a cyclic group. The compounds have the general formulas: ##STR3## wherein: Ar is phenyl or phenyl substituted by methylenedioxy or from one to two substituents selected from the group consisting of hydroxy, alkoxy of 1-3 carbon atoms and halogen;

Y is selected from the group consisting of CH.sub.2, CH.sub.2 CH.sub.2, CH.dbd.CH, O and OCH.sub.2 ;

Y' is selected from the group consisting of CH.sub.2, CH.sub.2 CH.sub.2 and OCH.sub.2 ;

R is alkyl of 1 to 4 carbon atoms; and R' is hydrogen or chlorine.

In a process aspect, the invention relates to a process for preparing the compounds of formulas I, II and III by reacting a compound of the formula ##STR4## wherein X is bromine or iodine and Ar, Y, Y', R and R' have the meanings given hereinabove, with an alkali metal salt of a diketone of the formula (RCO).sub.2 CH.sub.2.

In a further composition of matter aspect, the invention relates to a composition for combatting viruses which comprises an anti-virally effective amount of a compound of formula I, II or III in admixture with a suitable carrier or diluent.

In a further process aspect, the invention relates to a method for combatting viruses which comprises contacting the locus of said viruses with an anti-virally effective amount of at least one compound of formula I, II or III.

In the compounds of formulas I, II or III, when two monovalent substituents are present on the phenyl ring of Ar, the substituents can be the same or different. When halogen substituents are present, they can be any of the four common halogens, fluoro, chloro, bromo or iodo.

In the preparation of the compounds of formulas I, II and III, the reaction of the halide intermediates of formulas IV, V and VI with an alkali metal salt of a diketone, (RCO).sub.2 CH.sub.2, takes place in an inert solvent under anhydrous conditions at ambient temperature or above (20.degree.-100.degree. C.). The alkali metal salt, preferably the lithium, sodium or potassium salt, can be prepared in situ in a solution of the diketone with the appropriate base, for example lithium hydride or potassium carbonate.

The intermediates of formulas IV, V and VI are prepared by standard synthetic methods. One approach is via the compounds wherein the halomethyl group (--CH.sub.2 X) is replaced by carboxy or carboalkoxy. The acid or ester is reduced by means of a metal hydride such as lithium aluminum hydride to the corresponding methanol derivative (--CH.sub.2 OH) and the latter treated with hydrogen bromide to produce the bromomethyl compound.

The compounds of formula IV where Y is CH.dbd.CH are conveniently prepared by bromination of the corresponding compounds of the formula ##STR5## with N-bromosuccinimide.

The compounds of formulas IV or V where Y' is OCH.sub.2 are prepared by reacting 1,4-bis(bromomethyl)benzene or 1,4-bis-(bromomethyl)cyclohexane with a molar equivalent of a phenol, ArOH, in the presence of a base.

The compounds of formula I where Y is CH.sub.2 CH.sub.2 can also be prepared by catalytic hydrogenation of the compounds of formula I where Y is CH.dbd.CH.

The compounds of formulas I, II or III where the Ar group is substituted by hydroxy are conveniently prepared from the corresponding compounds of formulas I, II or III where the Ar group is substituted by alkoxy by means of conventional dealkylation procedures. It is, however, possible to carry out the conversion of compounds of formulas IV, V or VI where Ar is substituted by hydroxy to compounds of formulas I, II or III, respectively, where Ar is substituted by hydroxy by reacting the former with potassium salt of a diketone, (RCO).sub.2 CH.sub.2, formed in situ from the diketone and potassium carbonate.

The structures of the compounds of the invention were established by the modes of synthesis, by elementary analysis, and by infrared and nuclear magnetic resonance spectral determinations.

Biological evaluation of the compounds of the invention has shown that they possess anti-viral activity. They are thus useful in combatting viruses present on inanimate surfaces as well as viral infections in animal organisms. The in vitro testing of the compounds of the invention against herpes simplex viruses types 1 and 2 and equine rhinovirus has showed that they inhibited viral growth at minimum concentrations (MIC) ranging from about 0.6 to about 50 micrograms per milliliter. The MIC values were determined by standard serial dilution procedures.

The anti-viral compositions are formulated by preparing a dilute solution or suspension in an organic or aqueous-organic medium, for example ethyl alcohol, acetone, dimethylsulfoxide, and the like; and are applied to the locus to be disinfected by conventional means such as spraying, swabbing or immersing. Alternatively, the compounds can be formulated as ointments or creams by incorporating them in conventional ointment or cream bases, such as alkylpolyether alcohols, cetyl alcohol, stearyl alcohol and the like; as jellies by incorporating them in conventional jelly bases such as glycerin and tragacanth; or as aerosol sprays or foams. The anti-virally effective component of the compositions is present in a concentration of between about 0.6 parts per million and about 5 percent by weight, depending upon the chemical species used, the object to be treated and the type of formulation employed. For disinfection of inanimate surfaces with aqueous or aqueous-organic solutions, concentrations in the lower part of the range are effective. For topical application in medical or veterinary use in the form of ointment, cream, jelly or aerosol, concentrations in the upper part of the range are preferred.

The following examples will further illustrate the invention.

A mixture of 120 g. of 4-(4methoxybenzoyl)benzonitrile (m.p. 131.degree.-132.degree. C., Swiss Pat. No. 475,242), 750 ml. of 10 N hydrochloric acid in ethanol, and 750 ml. of ethanol was heated under reflux for 5.5 hours. The ethanol was removed from the reaction mixture and the residue partitioned between water and ethyl acetate. The organic layer was dried over anhydrous magnesium sulfate and the solvent removed to give 130 g. of semi-solid product. The ethyl 4-(4-methoxybenzoyl)benzoate thus obtained had m.p. 74.degree.-81.degree. C. when recrystallized from ethanol.

A solution of 130 g. of ethyl 4-(4-methoxybenzoyl)-benzoate in 1100 ml. of ethanol was hydrogenated in the presence of 10 g. of 10% palladium-on-carbon catalyst at 60.degree. C. and 45 psi initial pressure. The catalyst was filtered off and the solvent removed to give 120 g. of ethyl 4-(4-methoxybenzyl)benzoate as an oil.

A mixture of 120 g. of ethyl 4-(4-methoxybenzyl)-benzoate, 500 ml. of 2 N sodium hydroxide solution and 250 ml. of ethanol was heated at reflux for two hours. The reaction mixture was cooled, diluted with water and extracted with ether. The aqueous layer was acidified with hydrochloric acid and the precipitate which formed was collected and dried to give 100 g. of 4-(4-methoxybenzyl)benzoic acid, m.p. 152.degree.-153.degree. C. when recrystallized from aqueous ethanol.

A solution of 110 ml. (0.11 m) of 1 M boron hydride (BH.sub.3) in tetrahydrofuran was slowly added to a solution of 24.2 g. (0.10 m) of 4-(4-methoxybenzyl)benzoic acid in 110 ml. of tetrahydrofuran at 0.degree. C. The addition was complete in 20 minutes and the reaction mixture was stirred at room temperature for one hour. The reaction mixture was carefully acidified with hydrochloric acid and the solvent removed. The residue was partitioned between water and ether, and the ether layer was washed with aqueous sodium hydroxide, dried over anhydrous magnesium sulfate and concentrated to give 22.2 g. of 4-(4-methoxybenzyl)benzyl alcohol, m.p. 68.degree.-72.degree. C. when recrystallized from cyclohexane.

Hydrogen bromide was bubbled through a solution of 22.2 g. of 4-(4-methoxybenzyl)benzyl alcohol in 100 ml. of benzene held at 20.degree.-30.degree. C. for a period of 20 minutes. The reaction mixture was washed with aqueous sodium chloride solution, then with 2 N aqueous sodium hydroxide solution, dried over anhydrous magnesium sulfate and concentrated to give 27.5 g. of 4-(4-methoxybenzyl)benzyl bromide as an oil.

A mixture of 27.5 g. (0.095 m) of 4-(4-methoxybenzyl)-benzyl bromide and 20 g. (0.15 m) of the lithium salt of heptane-3,5-dione in 300 ml. of dimethylformamide was stirred at 60.degree. C. for 2.5 days. The solvent was removed from the reaction mixture and the residue partitioned between water and ether. The ether layer was washed with water, dried over anhydrous magnesium sulfate and concentrated. The residual oil was distilled to give 20.3 g. of 4-[4-(4-methoxybenzyl)benzyl]-heptane-3,5-dione, yellow oil, b.p. 193.degree.-199.degree. C. (0.04 mm).

4-[4-(4-Methoxybenzyl)benzyl]heptane-3,5-dione when tested in vitro against equine rhinovirus showed anti-viral activity at a minimal inhibitory concentration (MIC) of 6 micrograms per milliliter.

By replacing the lithium salt of heptane-3,5-dione in the foregoing preparation by a molar equivalent amount of the lithium salt of pentane-2,4-dione, nonane-4,6-dione, undecane-5,7-dione, or 1,1,7,7-tetramethylheptane-3,5-dione, it is contemplated that there can be obtained, respectively, 3-[4-(4-methoxybenzyl)benzyl]pentane-2,4-dione [I; Ar is 4-CH.sub.3 OC.sub.6 H.sub.4, Y is CH.sub.2, R is CH.sub.3, R' is H]; 5-[4-(4-methoxybenzyl)benzyl]nonane-4,6-dione [I; Ar is 4-CH.sub.3 OC.sub.6 H.sub.4, Y is CH.sub.2, R is CH.sub.2 CH.sub.2 CH.sub.3, R' is H]; 6-[4-(4-methoxybenzyl)benzyl]undecane-5,7-dione [I; Ar is 4--CH.sub.3 OC.sub.6 H.sub.4, Y is CH.sub.2, R is (CH.sub.2).sub.3 CH.sub.3, R' is H]; or 4-[4-(4-methoxybenzyl)benzyl]-1,1,7,7-tetramethylheptane-3,5-dione [I; Ar is 4--CH.sub.3 OC.sub.6 H.sub. 4, Y is CH.sub.2, R is C(CH.sub.3).sub.3, R' is H].

By replacing the 4-(4-methoxybenzoyl)benzonitrile in Example 1, part (a) above by a molar equivalent amount of 4-benzoylbenzonitrile, 4-(3,4-methylenedioxybenzoyl)benzonitrile, 4-(4-chlorobenzoyl)benzonitrile, 4-(2-chloro-4-methoxybenzoyl)-benzonitril e, 4-(4-bromobenzoyl)benzonitrile, or 4-(4-iodobenzoyl)benzonitrile, and carrying out the transformation of Example 1, parts (a) through (f), it is contemplated that there can be obtained, respectively, 4-(4-benzylbenzyl)heptane-3,5-dione [I; Ar is C.sub.6 H.sub.5, Y is CH.sub.2, R is C.sub.2 H.sub.5, R' is H]; 4-[4-(3,4-methylenedioxybenzyl)benzyl]heptane-3,5-dione [I; Ar is 3,4-CH.sub.2 O.sub.2 C.sub.6 H.sub.3, Y is CH.sub.2, R is C.sub.2 H.sub.5, R' is H]; 4-[4-(4-chlorobenzyl)benzyl]heptane-3,5-dione [I; Ar is 4-ClC.sub.6 H.sub.4, Y is CH.sub.2, R is C.sub.2 H.sub.5, R' is H]; 4-[4-(2 -chloro-4-methoxybenzyl)benzyl]-heptane-3,5-dione [I; Ar is 2-Cl-4-CH.sub.3 OC.sub.6 H.sub.3, Y is CH.sub.2, R is C.sub.2 H.sub.5, R' is H]; 4-[4-(4-bromobenzyl)benzyl]heptane-3,5-dione [I; Ar is 4-BrC.sub.6 H.sub.4, Y is CH.sub.2, R is C.sub.2 H.sub.5, R' is H]; or 4-[4-(4-iodobenzyl)-benzyl]heptane-3,5-dione [I; Ar is 4-IC.sub.6 H.sub.4, Y is CH.sub.2, R is C.sub.2 H.sub.5, R' is H].

The intermediate benzonitriles, ArCOC.sub.6 H.sub.4 CN, are readily prepared by a Friedel-Crafts type reaction between p-bromobenzoyl chloride and ArH, followed by reaction of the resulting benzophenone derivative ArCOC.sub.6 H.sub.4 Br with cuprous cyanide to replace the bromine atom by a cyano group.

The transformation of Example 1(f) can alternatively be effected by heating 4-(4-methoxybenzyl)benzyl bromide with heptane-3,5-dione in the presence of potassium carbonate and potassium iodide in an inert solvent such as 2-butanone.

A solution of 29.15 g. (0.116 m, 11 ml.) of boron tribromide in 160 ml. of methylene dichloride was added dropwise to a stirred solution of 26 g. (0.077 m) of 4-[4-(4-methoxybenzyl)benzyl]heptane-3,5-dione (Example 1) in 160 ml. of methylene dichloride held at -65.degree. C. The reaction mixture was stirred for three hours at room temperature, 500 ml. of ice-water then added and the stirring continued for 30 minutes. The organic layer was washed with saturated sodium carbonate solution, dried over anhydrous magnesium sulfate and concentrated. The residue was partitioned between water and ether with a trace of hydrochloric acid added. The mixture was shaken for 30 minutes and the ether layer separated and washed with sodium bicarbonate solution. The 22 g. of oil obtained after removal of the ether was chromatographed on 1 kg. of silica, packed wet with ethyl acetate:hexane 1:4 and eluted with the same solvent, taking 500 ml. fractions. Fractions 7- 15 gave 17.5 g. of 4-[4-(4-hydroxybenzyl)benzyl]heptane-3,5-dione, which was recrystallized from hexane-ether to give 6.5 g. of colorless plates, m.p. 65.degree.-66.degree. C.; MIC=3 microg/ml (equine rhinovirus).

Alternatively, the compound of Example 2 can be prepared by demethylation of 4-(4-methoxybenzyl)benzyl bromide (Example 1e) with boron tribromide according to the procedure of Example 2, and heating the resulting 4-(4-hydroxybenzyl)benzyl bromide with heptane-3,5-dione in the presence of potassium carbonate and potassium iodide in an inert solvent such as 2-butanone.

A solution of 60 g. of 3,4-methylenedioxybenzyl bromide in 200 ml. of carbon disulfide was slowly added over a period of 45 minutes to a solution of 260 g. of ethyl 2-furoate and 20 g. of zinc chloride in 600 ml. of carbon disulfide held at 31 10.degree. C. The reaction mixture was allowed to warm to room temperature, filtered, extracted with water and saturated sodium chloride solution, and dried over anhydrous sodium sulfate. The solvent was removed and the residue distilled to give 27 g. of ethyl 5-(3,4-methylenedioxybenzyl)-2-furoate, b.p. 162.degree.-166.degree. C. (0.5 mm), which crystallized to a solid, m.p. 67.degree.-68.degree. C.

A solution of 15.3 g. of ethyl 5-(3,4-methylenedioxybenzyl)-2-furoate in 75 ml. of tetrahydrofuran was added dropwise to a suspension of 4 g. of lithium aluminum hydride in 125 ml. of tetrahydrofuran at such a rate as to maintain reflux. The reaction mixture was then stirred for 45 minutes, and the excess lithium aluminum hydride was decomposed by dropwise addition of 50% aqueous tetrahydrofuran and stirring for 30 minutes. The mixture was filtered and the solvent removed. The residue was recrystallized from ether-pentane to give 9.8 g. of 5-(3,4-methylenedioxybenzyl)furfuryl alcohol, m.p. 68.degree.-69.degree. C.

A solution of 6.6 g. of phosphorus tribromide in 50 ml. of ether was added dropwise to a solution of 15 g. of 5-(3,4-methylenedioxybenzyl)furfuryl alcohol in 150 ml. of ether held at 0.degree. C. After the addition was completed, the mixture was stirred for one hour at room temperature and then shaken with 20 ml. of 50% aqueous sodium hydroxide for 15 minutes. The organic layer was separated, washed with water, dried over potassium hydroxide and concentrated. The resulting product was used directly in the next reaction.

The product of the reaction of part (c) above was dissolved in 175 ml. of dimethylformamide and 15 g. of the lithium salt of heptane-3,5-dione was added. The reaction mixture was kept at 50.degree.-60.degree. C. for about 16 hours. The solvent was then removed and the residue partitioned between water and ether. The ether layer was washed with water, dried and concentrated. The residue was distilled to give 13 g. of 4-[5-(3,4-methylenedioxybenzyl)-2-furfuryl]heptane-3,5-dione, yellow oil, b.p. 191.degree.-193.degree. C. (0.5 mm); MIC=6 microg/ml (equine rhinovirus).

By replacing the lithium salt of heptane-3,5-dione in the foregoing preparation by a molar equivalent amount of the lithium salt of pentane-2,4-dione, nonane-4,6-dione, undecane-5,7-dione, or 1,1,7,7-tetramethylheptane-3,5-dione, it is contemplated that there can be obtained, respectively, 3-[5-(3,4-methylenedioxybenzyl)-2-furfuryl]pentane-2,4-dione [III; Ar is 3,4-CH.sub.2 O.sub.2 C.sub.6 H.sub.3, R is CH.sub.3 ]; 5-[5-(3,4-methylenedioxybenzyl)-2-furfuryl]nonane-4,6-dione [III; Ar is 3,4-CH.sub.2 O.sub.2 C.sub.6 H.sub.3, R is CH.sub.2 CH.sub.2 CH.sub.3 ]; 6-[5-(3,4-methylenedioxybenzyl)-2-furfuryl]undecane-5,7-dione [III; Ar is 3,4-CH.sub.2 O.sub.2 C.sub.6 H.sub.3, R is (CH.sub.2).sub.3 CH.sub.3 ]; or 4-[5-(3,4-methylenedioxybenzyl)-2-furfuryl]-1,1,7,7-tetramethylheptane-3,5 -dione [III; Ar is 3,4-CH.sub.2 O.sub.2 C.sub.6 H.sub.3, R is C(CH.sub.3).sub.3 ].

By replacing the 3,4-methylenedioxybenzyl bromide starting material in Example 3, part (a), by a molar equivalent amount of benzyl bromide, 4-chlorobenzyl bromide, 4-bromobenzyl bromide, 4-fluorobenzyl bromide, 2-chloro-4-methoxybenzyl bromide, or 4-ethoxybenzyl bromide, and carrying out the transformations of Example 3, parts (a) through (d), it is contemplated that there can be prepared, respectively, 4-(5-benzyl-2-furfuryl)-heptane-3,5-dione [III; Ar is C.sub.6 H.sub.5, R is C.sub.2 H.sub.5 ]; 4-[5-(4-chloro-benzyl)-2-furfuryl]heptane-3,5-dione [III; Ar is 4-ClC.sub.6 H.sub.4, R is C.sub.2 H.sub.5 ]; 4-[5-(4-bromobenzyl)-2-furfuryl]heptane-3,5-dione [III; Ar is 4-BrC.sub.6 H.sub.4, R is C.sub.2 H.sub.5 ]; 4-[5-(4-fluorobenzyl)-2-furfuryl]-heptane-3,5-dione [III; Ar is 4-FC.sub.6 H.sub.4, R is C.sub.2 H.sub.5 ]; 4-[5-(2-chloro- 4-methoxybenzyl)-2-furfuryl]heptane-3,5-dione [III; Ar is 2-Cl-4-CH.sub.3 OC.sub.6 H.sub.3, R is C.sub.2 H.sub.5 ]; or 4-[5-(4-ethoxybenzyl)-2-furfuryl]heptane-3,5-dione [III; Ar is 4-C.sub.2 H.sub.5 OC.sub.6 H.sub.4, R is C.sub.2 H.sub.5 ].

It is further contemplated that 4-[5-(2-chloro-4-methoxybenzyl)-2-furfuryl]heptane-3,5-dione can be demethylated with boron tribromide according to the procedure of Example 2 to give 4-[5-(2-chloro-4-hydroxybenzyl)-2-furfuryl]heptane-3,5-dione [III; Ar is 2-Cl-4-HOC.sub.6 H.sub.3, R is C.sub.2 H.sub.5 ].