Received: December, 2012

Fluorine Notes, 2013, 86, 5-6

ESTERIFICATION OF 5,9-DIMETHYL-16-ISOPROPYL-5,13ОІ, 14ОІ-TRIHYDROXYMETHYLTETRACYCLO[10.2.2.01.10.04.9]HEXADEC-15-ENE USING PERFLUORO(2-METHYL-3-OXAHEXANOYL)FLUORIDE

L. M. Popova¹, S. V. Vershilov², A. N. Gorbenko¹

¹Saint-Petersburg State Technological University of Plant Polymers, Saint-Petersburg, Russia
e-mail: lorapopova@mail.ru

²State Enterprise S.V.Lebedev Research Institute of Synthetic Rubber (NIISK), Saint-Petersburg, Russia

Abstract: New polyfluoroalkyl triester has been synthesized esterificating 5,9-dimethyl-16-isopropyl-5,13ОІ,14ОІ-trihydroxymethyltetracyclo[10.2.2.01.10.04.9]- hexadec-15-ene using perfluoro(2-methyl-3-oxahexanoyl)fluoride in 1,4-dioxane over triethylamine.В 

Keywords: Abietic acid, Maleopimaric adduct, Reduction, Triol, Etherification, Polyfluoroalkyl-containing triesters.

Syntheses based on diterpenoic acids are of big interest of researchers. The spectrum of practical tasks solving which they assume using of derived resin acids, particularly based on their dienoadducts is constantly widening. New fields of application for those classes of compounds are being discovered along with such traditional directions as developing of paints, coatings and polymers [1], emulsifiers [2] and corrosion inhibitors [3]. They suggested using of TVD (Thermal Vaccum Deposition)-films derivatives of maleopimaric and citraconic acids for the production of photomasks in microelectronics [4]. The opportunities of developing of stereoselective complex metallic catalysts [5], “ionic liquids” [6] based on derivatives of abietic acid have been considered as well. In our opinion, the search for effective surfactants and biologically active compounds in the row of modified polyfluoroderivatives of diterpenoic alcohols has got no less potential [7].

In the present report you will find the information on the synthesis of new tri(polyfluoroalcoxylacylate)triol obtained using method of maleopimaric adduct’s reduction.

It is known, that obtaining of dienoadducts like maleopimaric acid increases the resistance of material to oxidation and also provides for carrying out further chemical modification of resin acids [8, 9]. However, only a few reports refer to the synthesis of polyols based on maleopimaric acid. Thus, the obtaining method of triol (m. p. 168 -170 yield app. 50%) by reduction of maleopimaric acid using lithiumalumohydride in ether at room temperature in 7 days has been patented [8]. In another report Mr. Zalkov with co-workers [9] have obtained polycyclic hydrocarbon containing four hydroxyl groups when reducing Оі-lactone tetracyclohexadecene of tricarboxylic acid by lithiumalumohydride in ether during 8 hour boiling.В  В 

We have synthesized the initial maleopimaric adduct out of tall oil rosin and maleic anhydride over concentrated sulphuric acid at 120В°C using known method described in the work [11]. The product yield (I) was 35%.

Diterpenoic triol (II) has been synthesized similarly to the procedure described in [9]: the solution of adduct (I) in tetrahydrofurane was added to the suspension of lithiumalumohydride in THF at room temperature and was kept for 24 hours. The process has been controlled using method of Thin Layer Chromatography. The excess of LiAlH₄ was being decomposed adding sequentially water, then 1M H₂SO₄. After isolation and drying the yield of raw product (II) amounted to 95% (see Scheme 1).

Scheme 1

The reaction mixture (II) has been studied to establish the composition and structure of synthesized products using spectral methods.

In the IR spectrum (II) we have observed the stripes of stretching vibrations C-H in the range of 2950-2865 cm^-1, multiply bond C=C at 1700 cm^-1 and hydroxyl groups at 3500 cm^-1. There were practically no signals corresponding to stretching vibrations of carbonyl groups in the range of 1770 cm^-1.

Multiplet signals of methylene groups of triol CH₂-O- at 3.07 d (1H, H²⁰, 11.3), 3.23 t (1H, H¹⁷, J_17A,1 = J_17A,17B =10 Hz), 3.36 d (1H, H²⁰), 3.39 m (1H, H¹⁶), 3.70 m (1H, H¹⁶), 3.71 dd (1H, H¹⁷) ppm have been registered in ¹H NMR spectrum of product (II). Singlet with chemical shift at 5.54 ppm (1H, H¹¹) corresponds to the double bond of maleopimaric fragment. Besides that, in the spectrum of mixture (II) there are signals, with Оґ at 5.39 ppm with (C⁷-H) and 5.76 ppm bs (C¹⁴-H) (abietenol) and aromatic protons with chemical shifts at 6.87 s (C¹⁴H, J=7 Hz), 6.98 d (C¹⁴H, J=7 Hz) and 7.15 d (C¹¹H) ppm (dehydroabietinol). According to ¹H NMR data the rate of products in mixture was equal to: triol : abietinol : dehydroabietinol, 1 : 0.5 : 1 respectively.

As mentioned before there is information in literature regarding synthesis of trialkyl esters from corresponding three-atomic diterpene alcohol [5], though the information on analogous reactions with perfluoroalkylacylhalogenides.

For the first time we have carried out the esterification of triatomic diterpene alcohol (II) using equimole quantity of perfluoro(2-methyl-3-oxahexanoyl)-fluoride over scavenger of hydrogen fluoride – triethylamine in anhydrous 1,4-dioxane (see Scheme 2). The process was carried out during 2 hours boiling under chromatographic control. Upon ending the reaction all the volatile products have been evaporated, afterwards dry residue has been dissolved in ethoxyethane, washed through with water and dried up. The yield of raw product (III) amounted to 35%.

Scheme 2

The composition and structure of mixture obtained has been analyzed using analytical and spectral methods.

In the IR spectrum (III) there are stripes of stretching vibrations of C-H bonds in the range of 2950-2865 cm^-1, and also stretching vibrations of carbonyl groups C=O at 1780 cm^-1 and C=C at 1690 cm^-1.

In the UV spectrum (III) in the alcoholic solution three maximum values of absorption of corresponding ПЂв†’ПЂ*-transitions showed themselves at 223 nm (lg 5.60), 242 nm (shoulder) and 257 nm (lg 5.78), confirming the presence of conjugated bonds in the products.

Multiplet signals of methylene groups connected with perfluorinated fragments are typical for tripolyfluoroacylate (III) in H¹ NMR at 2.86 d (1H, H²⁰, 11.3), 3.18 d (1H, H²⁰), 3.44 t (1H, H¹⁷, J_17A,1 = J_17A,17B 10 Hz), 3.70 m(1H, H¹⁶), 3.74 m (1H, H¹⁶), 4.19 dd (1H, H¹⁷), as in spectra of triesters described in the work [5], insignificant shifts into strong field for pointed signals are observed. Signal with chemical shift at 5.54 ppm with (1H, H¹¹) corresponds to double bond of maleopimaric fragment. Also the signals of protons of diene system are in the spectrum of obtained mixture at 5.36 ppm (C⁷-H) Рё 5.75 ppm (C¹⁴-H) (ester of abietinol), besides that the signals of aromatic protons with Оґ 6.86 with (C¹⁴H), 6.98 d (C¹⁴H) and 7.14 d (C¹¹H) ppm (the ester of dehydroabietinol). The rate of products in the mixture virtually hasn’t changed (triester : ester of abietinol : ester of dehydroabietinol, 1 : 0.5 : 1 respectively).

In the ¹⁹F NMR spectrum of product (III) there are resonance signals of fluorine atoms, which according to chemical shifts, multipletness and integral intensivities correspond to perfluorinated fragments in the range of–141.40 С‡ –71.70 ppm.

Experimental Part

UV spectra of compounds’ ethanol solutions were obtained using SF-2000 spectrophotometer at concentration of compounds equal to 10^-4 mole/l the thickness of absorbing layer equals to 1cm.

¹H and ¹⁹F NMR spectrum has been registered using Bruker 500 with operational frequency of 500 MHz (470 MHz - for ¹⁹F), in CDCl₃ exterior standard – CCl₃F.

IR spectra were registered at Specord M-80 (Jena) with operational frequency within the range of 4000-900 cm^-1. The measurements were carried out using CaF₂ glasses with the cuvette’s thickness of 200 mkm.

The reaction path and purity of initial and obtained compounds have been carried out using TLC method at Sorbphil plates, eluent: hexane-methylenchloride (1-1) and hexane-methylenechloride-acetone (1-1-0.5).

The purification and dehydration of tolyol, tetrahydrofurane and 1,4-dioxane were carried out using the known methods [12].

Tall rosin and perfluro(2-methyl-3-oxahexanoyl)fluoride (boiling point 54 В°C) have been used as initial compounds in the work process [13].

Maleopimaric adduct of tall oil rosin (I). 3.5 g (36 mmole) of maleic anhydride, 4-5 drops of concentrated H₂SO₄ are added to 10 g (33 mmole) of tall oil rosin and kept for 1 hour at 120В°C. The reaction is controlled using method of TLC. The reaction mass is extracted using toluene (3 x 20ml) upon the end of the process and the extract itself is washed through with hot water till neutral reaction is obtained, dried with Na₂SO₄, the solvent is distilled and dried in vacuum over P₂O₅. The yield of product (I) amounted to 8 g (60%).

Resedimentation of maleopimaric acid [11] (I). 23 ml of diethyl ether are being added to 6.0 g (15 mmole) of maleopimaric adduct and heated up till total dissolving, afterwards the product (I) is precipitated using light petroleum ether, then it is cooled, filtered and lade-down crystals are dried in vacuum over P₂O₅. Yield amounted to 1.7 g (35%).

5,9-Dimethyl-16-isopropyl-5,13ОІ,14ОІ-trihydroxymethyltetracyclo- [10.2.2.0^1.10.0^4.9]hexadec-15-ene (II). The solution of 2.74 g (6.8 mmole) of maleopimaric acid in 20 ml of THF is being added drop by drop to the mixture of 0.8 g (21 mmole) of LiAlH₄ in 13 ml of THF at room temperature, then mixed up and kept for 24 hours at room temperature, afterwards 43 ml of H₂O and 36 ml of 1M H₂SO₄ are being added dropwise and mixed up for 3 hours. Upon ending of decomposition of LiAlH₄ the reaction mixture has been extracted using diethyl ether (3Г—30 ml), the organic phase has been washed through with distilled water, dried with Na₂SO₄ and solvent has been distilled off. The yield of product (II) amounted to 2.35 g (95%).

Tri[perfluoro(2-methyl-3-oxahexanoyl)] ester 5.9-dimethyl-16-isopropyl-5,13 -5,13ОІ,14ОІ-trihydroxymethyltetracyclo-[10.2.2.0^1.10.0^4.9]hexa-dec-15-ene (III). The solution of 6.2 g (19 mmole) perfluoro(2-methyl-3-oxahexanoyl)fluoride in 10 ml of 1,4-dioxane was added dropwise to the mixture of 2,34 g (6.2 mmole) triol (II) and 1.89 g (19 mmole) triethylamine. The reaction mixture was kept for 2 hours at 50-55В°C, the reaction path was controlled using TLC method. Upon the reaction end the excess of perfluoro(2-methyl-3-oxahexanoil)fluoride, triethylamine and 1,4-dioxane was distilled off. Afterwards the residue was dissolved in diethyl ether, washed through with distilled water, dried with Na₂SO₄, filtered and the solvent was distilled off. The yield (III) amounted to 2.8 g (35%).

Conclusion

The processing of triol, the product of reduction of maleopimaric adduct using the equimolar quantity of perfluoro(2-methyl-3-oxahexanoyl)fluoride over acceptor of hydrogen fluoride (triethylamine) results in formation of polyfluorine containing complex triester.

References

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Recommended for publication by V. Kornilov

Fluorine Notes, 2013, 86, 5-6