US2854478A - Triethylenically unsaturated octahydro-7-isopropyl-1,4b-dimethyl-1-phenanthrenecarboxylic acid - Google Patents

Description

TRIETHYLENICALLY UNATURATED OCTAHY- DRO -7 -ISOPROPYL-1,4b -DIMETHYL-1-PHENAN- THRENECOXYLIC ACID No Drawing. Application December 29, 1955 Serial No. 556,070

1 Claim. (Cl. 260-5145) This invention relates to new resin acids that may be prepared from the lactone of hydroxytetrahydroabietic acid and the esters of such acids.

It is well known that a crystalline lactone may be obtained from partially hydrogenated rosin, i. e., a rosin containing a dihydroabietic acid, by treatment of the rosin with sulfuric acid. This lactone is commonly called the lactone of hydroxytetrahydroabietic acid and is characterized by a melting point of 131-132" C. and [al -3. According to U. S. 2,360,204 this lactone when treated with an alkyl Grignard reagent yields two acids (called therein dihydroabietic acids), one being characterized by having a melting point of 147-148 C. and [a'l +68 and the other being characterized by having a melting point of 185186 C. and [:1 -36. It is now believed to be rather well-established that during lactonization the angular methyl group shifts from the 4a-position which it has in dihydroabietic acid to the 4b-position and that the alcoholic oxygen is at the 4a-position. With such a shift of the angular methyl group, the acids mentioned above and named in said patent as dihydroabietic acids are instead acids corresponding to a dihydroabietic acid but having the angular methyl group attached to the 4bposition instead of the 4a-position. Accordingly, these acids are more properly named dodecahydro-7-isopropyl- 1,4b-dimethyl-l-phenanthrenecarboxylic acids.

Now, in accordance with this invention, it has been found that an entirely new group of resin acids or esters thereof may be obtained by halogenation of the esters of the acids formed from the lactone of hydroxytetrahydroabietic acid on treatment with a Grignard reagent by bromination of esters of said acids followed by dehydrohalogenation. These new acids contain two or three ethylenic double bonds and may be named as decahydro 7 isopropyl 1,4b dimethyl 1 phenanthrenecarboxylic or octahydro 7 -isopropy1- 1,4b dimethyll-phenanthrenecarboxylic acids. Just what is the position of the double bonds in these new acids is not definitely known, but it has been established by the above sequence of reactions that there is produced a mixture of at least two diene acids and at least one triene acid. It is believed that one of the diene acids has the following formula:

HsC OOOH The other diene acid is believed to have one of the fol- ..tes Patent 0 lowing structures, most probably either the second'or third structure:

H8O COOH H3O /CH:

The triene is believed to have the following structure:

H30 CH3 but it is possible that it could have either of the following two structures:

H O COOH H3O CH3 H30 0 OOH H3O OH;

Whatever may be the actual position of the double bond, it is known for certainty that the same mixture of diene and triene acids is produced regardless of which of the two acids of U. S. 2,360,204 is used as the starting material and further that no rearrangements or carbon-tocarbon fissions occur during the preparation of the new acids, for on hydrogenation of the diene and triene acids of this invention, the original acids are regenerated.

The following examples will illustrate the preparation of the new resin acids of this invention and the esters thereof. All parts, percentages and proportions are by weight unless otherwise indicated.

Example I The resin acid obtained by treating the lactone of hydroxytetrahydroabietic acid with a Grignard reagent and characterized by having a melting point of l47148 C. was esterified by dissolving 6.1 parts of said acid in 250 parts of anhydrous acetone and adding 7.1 parts of potassium carbonate and 14 parts of methyl iodide. The reaction mixture was agitated and heated under reflux for 16 hours, after which it was cooled and filtered. The filtrate was then concentrated, diluted with water, and extracted with ether. The ether layer was separated, washed, and dried. Removal of the ether yielded 6.36 parts of an oil identified as the methyl ester of the above acid.

The total amount of the methyl ester was mixed with 4.0 parts of N-bromosuccinirnide, 0.25 part of p-cymyl cumyl peroxide, and 1600 parts of carbon tetrachloride. A small stream of nitrogen was sparged through the reaction mixture, and after cooling to -2 C., the reaction mixture was exposed to ultraviolet light for 2 hours and then filtered. The filtrate containing the brominated methyl ester was then mixed with 92 parts of collidine and heated to boiling for 16 hours. After cooling, the reaction mixture was diluted with 500 parts of ether and filtered to remove the precipitated collidine hydrobromide. The amount of the latter so obtained was 3.64 parts which was 90% of the theoretical amount. The filtrate was distilled under reduced pressure and the residue was dissolved in ether. The ether solution was then washed and dried and finally distilled to' remove the ether solvent. The yield of dehydrohalogenated esters so obtained amounted to 6.05 parts. An ultraviolet spectral analysis of these esters indicated the presence of at least three ditferent conjugated double bond systems, one at 239- 240 m one at 269 m and the third at approximately 320 mg.

The mixture of the methyl esters of the decahydroand octahydro-7-isopropyl-l,4b-dimethyl-l-phenanthrenecarboxylic acids produced above was then saponified by suspending the above product in 100 parts of diethylene glycol, adding 2 parts of potassium hydroxide dissolved in 20 parts of water, and heating the mixture to reflux temperature for 2 hours under a blanket of nitrogen. The reaction solution so obtained Was then cooled, diluted with 300 parts of water, and extracted with ether. The aqueous phase was separated and acidified with 10% hydrochloric acid. The precipitated acids which resulted were extracted with ether and isolated from the ether extract. An ultraviolet spectrum of this product established that there were at least three different conjugated unsaturated acids present in the mixture and that the acidic mixture contained approximately of one diene acid, of a second diene acid, and 10% of a triene acid.

By converting this acid mixture to its butanol amine (2-amino-Z-methylpropanol) salts, recrystallizing from acetone several times, and then regenerating the acids by acidification with acetic acid, it was possible to concentrate one of the diene acids to an estimated 80% purity. The mother liquors from these acetone recrystallizations were combined, neutralized with boric acid, extracted with ether, and then treated with di-n-amylamine- Recrystallization of the amylamine salts from acetone several times followed by acidification gave a crystalline concentrate which was estimated by ultraviolet spectral analysis to contain of the second diene acid. Elemental. analyses of both of these diene acid concentrates were consistent with the empirical formula C H O Example 2 Fifty parts of the resin acid obtained by treating the lactone of hydroxytetrahydroabietic acid with a Grignard reagent and characterized by having a melting point of 185 C. was methylated in the same manner as described in Example 1 to give 48 parts of the methyl ester. This ester was then brominated with 29 parts of N-bromosuccinimide under the same conditions as described in the bromination reaction in Example 1. Treatment of this brominated product with collidine resulted in dehydrohalogenation and the formation of 30 parts of collidine hydrobromide. After removal of this salt and the collidine solvent, the reaction residue was dissolved in ether, Washed, and dried. Removal of the ether yielded a mixture of esters that had the same ultraviolet absorption characteristics as the mixture of esters produced in Example 1.

Partial saponification of these esters with sodium hydroxide in butanol and a little water gave 22 parts of an acid fraction (fraction A) and 30 parts of unsaponified material. A more drastic saponification of the latter with potassium hydroxide and diethylene glycol gave 21 parts of acidic material (fraction B and 5 parts of neutral materials. Fractional recrystallization of fraction B1 from acetone yielded 5.2 parts (fraction 13:) of

the original acid having a melting point .of 185 C. and 9.0 parts (fraction B of a mixed acid fraction. Ultraviolet spectral analyses gave the following composition estimates for these various acid fractions:

Percent Percent Hetero- Homo- Percent Original Fraction annular annular Triene Acid Diene Diene Acid Acid Acid A portion of fraction A was reacted with maleic anhydride in refluxing benzene. After removal of the benzene solvent by evaporation, the residue was dissolved in excess 2% alkali and then neutralized with hydrochloric acid to pH 6. The precipitated, unreacted material (major product) was collected by filtration. An ultraviolet spectral analysis of this unreacted material indicated the triene acid component had been removed by adduct formation and the heteroannular and homoannular diene acids had been further concentrated to an estimated 45% and 45%, respectively. A small sample of this crystalline concentrate was dissolved in a dry, hydrogen chloride-saturated chloroform solution and allowed to stand at room temperature for 18 hours. Separation of the products gave a neutral fraction (major product) and an acid fraction. -Recrystallization of this acid fraction as its butanol amine salt from methyl acetate gave the butanol amine salt of the pure heteroannular diene acid; [ocJ +l11 (1% in ethanol);

M 240 mp (6, 15,800)

Another portion of fraction A was hydrogenated in acetic acid with a platinum catalyst. An X-ray diflraction analysis indicated the crystalline product was the original starting acid having a melting point of 185 C.

Fraction B was converted to its di-n-amylamine salts and recrystallized several times from methyl acetate. This increased the homoannular diene acid concentration in the mixed acids to an estimated Example 3 A 1:1 mixture (23 parts) of the two resin acids obtained by treating the lactone of hydroxytetrahydroabietic acid with a Grignard reagent and characterized by having melting points of 147-148" C. and C. was brominated with 13 parts of N-bromo-succinimide in the same manner as described in Example 1. Dehydrohalogenation of the brominated product with collidine yielded 14.3 parts of collidine hydrobromide. After removal of this collidine hydrobromide and the excess collidine, the mixture of dehydrohalogenated esters (24.3 parts) was partially saponified with 6.2 parts of potassium hydroxide in refluxing diethylene glycol to yield 9.2 parts of an unsaponified material and a 13.5-part acid fraction. By a fractional recrystallization of the butanol amine and diamylamine salts of this acid fraction, there was obtained two crystalline concentrates of unsaturated acids. One of these was estimated by ultraviolet spectral analysis to contain of the heteroannular diene acid and 80% of the homoannular diene acid. The other crystalline concentrate Was estimated by the same means to contain 15 of the heteroannular diene acid, 75% of the homeannular diene acid, and 3% of the triene acid.

In accordance with this invention, it is possible to produce a new series of resin acids having an entirely diflerent structural skeleton from that of the naturally occurring resin acids. As pointed out above, it is now accepted that the angular methyl group in the lactone of hydroxytetrahydroabietic acid is in the 4b-position and consequently that the two monoethylenically unsaturated acids, having an empirical formula C H O and produced by treating the lactone with a Grignard reagent, likewise have the angular methyl group attached to the 4b-position. By brominating esters of these acids and then dehydrobrominating the bromo derivatives, it has now been possible to produce a mixture of diand triethylenically unsaturated acids having empirical formulas of C H O and C H O respectively, which may then be separated into its individual components. Of particular significance is the fact that the same mixture of diene and triene acids is produced regardless of which of the monoethylenically unsaturated acids is used as a starting material, i. e., the one characterized by having a melting point of 147 C. or the one having a melting point of 185 C. Of further significance is the fact that on hydrogenation of the mixture of diene and triene acids or of the individual acids, the original starting acid is regen erated (020113202),

The halogenation reaction may be carried out by contacting an ester of one or both of the unsaturated resin acids produced from the lactone with an N-haloimide. Exemplary of N-haloimides which may be used are N-bromoacetimide, N-bromosuccinimide, N-bromophthalimide, N-chloroacetimide, N-chlorosuccinimide, etc. Since these N-haloinn'des will react with water to form hypobromous acid, or hypochlorous acid, the reaction should be carried out under substantially anhydrous conditions to avoid waste of the brominating agent. Bromination or chlorination reaction temperatures can range between 22 C. and the refluxing temperature of the reaction mixture, the preferable temperature being 2 C.

Dehydrohalogenation of these halogenated monoolefinic resin acid esters, is most conveniently carried out by treatment with excess collidine at temperatures between 10 and 175 C., preferably between and C. Other basic materials may also be employed with considerable success, e. g., dimethylaniline, quinoline and isoquinoline, pyridine, potassium carbonate, alumina, etc. These dehydrohalogenations may be carried out in solutions or mixtures in inert solvents (e. g., carbon tetrachloride, ether, benzene, etc.) or in the case where the dehydrohalogenating agent is a liquid in a solution or mixture with that agent.

The above described halogenation and dehydrohalogenation reactions gave as a product a mixture of esters of the acids of the invention which esters correspond to the ester used as a starting material. While the examples have shown only the use of a methyl ester as a starting reactant, it is obvious that other esters can be used since the ester group takes no part in the reaction. Lower alkyl esters such as the methyl, ethyl, propyl, and butyl esters are preferred starting reactants.

The sodium salts of the acids of this invention are highly efiicient sizes for paper. A typical size can be made by saponifying the mixed acids prepared in Example 1 with sodium carbonate in aqueous solution. This forms a liquid size which can be dehydrated, if desired, to form a dry size. The size is used in the same well-known methods that rosin sizes are used and is capable of providing sized paper with excellent penetration characteristics.

What we claim and desire to protect by Letters Patent is:

Triethylenically unsaturated octahydro-fl-isopropyl-l, 4b-dimethyl-l-phenanthrenecarboxylic acid.

References Cited in the file of this patent Du Pont et al.: C. A., vol. 43, 6605, 1949, July-Septemher.

Du Pont et al.: C. A., vol. 45, 8482, 1951, October- November.

Hasselstrom et al.: J. A. C. 5., vol. 61, 1228.