Synthesis and Transformations of Norbornyl Acrylates

Russian Journal ofOrganic Chemistry, Vol. 37, No. 12, 200], pp. 1700-1702. Translatealfrom Zhurnal Organicheskoi Khimii, Vol. 37, No. 12, 200], pp. 1781-1783. Original Russian Text Copyright @ 200] by Mamealov, Nabieva, Dzhafarova. Synthesis and Transformations of Norbornyl Acrylates M. K. Mamedov, E.K.Nabieva, and E.N.Dzhafarova Institute of Petrochemical Processes, Academy of Sciences of Azerdaidzhan, Baku, 370025 Azerdaidzhan Received September 26, 2000 Abstract-—A simple and more environmentally friendly procedure than that traditionally used was developed for preparation of esters consisting in acrylic acid addition to bicyclo[2.2.l]hept-2-ene and its 5-alkyl derivatives. The acrylates obtained were subjected to hydrogenetion followed by hydrolysis of propionic acid esters. A number of new compounds was obtained; some among them possess a pleasant odor. Esters of cyclic alcohols and acrylic acid are successfully used as monomers for plastics [1, 2], efficient adhesive for dental prostheses [3], com- pounds for protection from the action of UV light and paint binder at electronic printing [4], and also in preparation of nonaqueous polymer materials [5]. We developed a simple and more environmentally friendly procedure than that traditionally used for preparation of acrylic acid esters by thermal addition of the acid to bicyclo[2.2.l]hept-2—ene and its 5-exo- alkyl derivatives. The initial bicycloolefins were obtained by isomerization of a mixture of the endo and exo isomers in the presence of AlCl3 in dichloro— methane solution. 0 7 H8 9 Rib +CH =cHcooH—- Rii§2’OCCH:CH2 2 I0 5 4 3 I—VI R = H (I), Me (II), Et (III), i—Pr (IV), Pr (V), Bu (VI). Acrylic acid same as saturated monocarboxylic acids [7-9] stereoselectively adds at heating without catalyst to bicyclo[2.2.l]hept—2-ene to yield an exo isomer of ester I. Compound I smells of pleasant odor with fruit tint and may be used as a component of synthetic perfumes. The investigation of the composition and purity of the esters obtained by GLC revealed that the thermal addition of acrylic acid to the 5-exo-alkyl derivatives of norbornene resulted in formation of 5-ex0-alkyl- bicyclo[2.2.l]hept-2-yl exo-acrylates (II—VI) as 92-94% of the product and 6-exo-alkylbicyclo[2.2. l]- hept—2-yl ex0—acrylates as 6—8% in the ratio 93:7. We used in reaction hyroquinone as inhibitor to prevent the radical polymerization of the acrylic acid at heating. The conditions of reaction and reagents ratio were optimized for ester formation; the best conditions were as follows: temperature 170°C, molar ratio of bicyclic olefins to acrylic acid 1 2 1.25, reaction time 3 h, hydroquinone in amount of 0.1 wt% to acrylic acid. Under these conditions the yields of acrylates reach 54-75%. Alkyl substituents in the 5-position negatively affect the reactivity of the 7r-bond in the bicyclo- [2.2.l]hept-2—ene ring. The longer is the hydrocarbon chain of the alkyl substituent, the lower is the yield of the corresponding acrylate: H> CH3> CH3CH2> cH,cH,cH,> (CH3)2CH >CH3(CH2)3CH2. Aiming at preparation of propionic acid esters with saturated bicyclic alcohols hydrogenation of acrylates I—VI was perfomed in the presence of Ni on kieselguhr as catalyst. The hydrogenated esters were also subjected to hydrolysis by 20% NaOH solution R E.’ CCH=CH2 H2 OCCHZCH3 R :~ R I-VI VII—XII ?~Na°H ¢bOH —CH3CH2COONa R XIII—XVIII R = H (1, VII, XIII), Me (II, VIII, XIV), Et (III, IX, XV), 2'-Pr (IV, X, XVI), Pr (V, XI, XVII), Bu (VI, XII, XVIII). 1070-4280/01/3712-1700$25.00 © 2001 MAIK “Nauka/Interperiodica” SYNTHESIS AND TRANSFORMATIONS OF NORBORNYL ACRYLATES 1701 Table 1. 1H NMR spectra of compounds synthesized, 8, ppm Compd. H’ H2 H3 H“ H5 H6 H7 H8 H9 H” no. I 2.20 4.60 1.40 2.20 1.0 1.10 1.13 6.23 5.75 - II 2.20 4.60 1.45 2.25 5.0 1.15 1.15 6.18 5.76 0.85 VII 2.45 4.75 1.30 2.45 1.9 1.40 1.00 2.25 1.10 - VIII 2.12 4.72 1.48 2.12 5.1 1.90 1.30 2.37 1.27 1.14 XIII 2.50 4.05 1.48 2.55 1.9 1.40 1.30 4.70 - - XIV 2.55 4.15 1.48 2.60 3.9 1.90 1.30 4.65 1.10 - Table 2. Yields, physical properties and elemental analyses of norbornyl acrylates I-VI 0 Found, % Calculated, % C°mPd' Yield, % 35*’ (I; d3,° mg’ Formula no. ( mm g) C H C H I 75 108 1.0318 1.4740 72.24 8.46 C10H14O2 72.26 8.89 II 68 117-118 0.9966 1.4755 73.29 8.91 CHHMOZ 73.30 8.94 III 65 136-137 0.9863 1.4785 74.17 9.30 C,2H18O2 74.19 9.33 IV 59 116-117 0.9710 1.4792 74.90 9.61 CBHZOO2 74.96 9.67 V 60 159-160 0.9827 1.4804 74.92 9.65 CBHQOOZ 74.96 9.67 VI 54 179-180 0.9821 1.4860 75.60 9.95 C,4H22O2 75.63 9.97 along the known procedure [10]. We obtained as a result norbornyl propionates VII-XII in 94-95% yield and bicyclic alcohols XIII-XVIII in 96-98% yield. The purity of compounds synthesized after distilla- tion was 99-99.8%. Their isomeric composition and structure was investigated by means GLC, IR, and NMR spectroscopy. In the IR spectra of all acrylates appears a strong band in the 970 cm'1 region char- acteristic of an exo isomer. The absorption in the region 1725-1730 and 1240-1245 cm'1 evidences the presence of ester groups in the molecules, and the absorption bands at 815 and 890 cm’1 in combination with a band at 1640 cm’1 prove the presence of a vinyl group. 1H NMR spectra of some compounds synthesized are presented in Table 1. As seen from Table 1, in the spectra of acrylates I, II are observed signals at 5.75-6.23 ppm character- istic of vinyl protons, in the spectra of alcohols XIII, XIV appear the signals of hydroXy group protons at 4.65-4.70 ppm, the endo-protons H2 and H5 resonate in the 4.0-5.0 ppm region. EXPERIMENTAL The conditions used for GLC analysis and record- ing of 1H,13C, and IR spectra were described in our preceding communication [8]. RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 As initial compounds were used the following bicyclo hydrocarbons: bicyclo[2.2.l]hept-2-ene, 5-methyl-, 5-ethyl-, 5-isopropyl-, and 5-butylbicyclo- [2.2.l]hept-2-enes. The compounds were obtained by condensation of olefins with cyclopentadiene [11]. The acrylic acid applied corresponded to specifica- tions TU 6-09.413-83. The synthesis of acrylates and their hydrogenation were carried out in a rotating pressure reactor of stainless steel, the hydrolysis of propionates was performed in the common glass vessels. 2-exo-Bicyclo[2.2.1]heptyl acrylate (I). A miX- ture of 47.1 g of norbornene, 45 g of acrylic acid, and 0.045 g of hydroquinone was heated in the pres- sure reactor to 170°C for 3 h. The fractional distilla- tion of the resulting miXture afforded 61.9 g (75%) of compound 1. Compounds II-VI were prepared similarly (Table 2). 2-eX0-Bicyclo[2.2.1]heptyl propionate (VII). A mixture of 33.2 g of compound I, 3.32 g of catal- yst Ni on kieselguhr activated in a flow of hydrogen, and 0.33 g of hydroquinone was charged in the pres- sure reactor, and hydrogen was fed in to the pressure of 100 atm. The reactor was heated to 120°C for 2.5 h. After the hydrogen was no long consumed the No. 12 2001 1702 MAMEDOV et al. Table 3. Yields, physical properties and elemental analyses of norbornyl propionates VII-XII 0 0 Compd. Yield, % hp; 0C dio H1230 Found, A) Fommla Calculated, A) no. (30 mm Hg) H C H VII 94 109.5 0.9996 1.4596 71.32 9.56 CWHMOZ 71.39 9.58 VIII 96 119-120 0.9894 1.4620 72.45 9.93 CHH18O2 72.49 9.95 IX 98 137.0-137.5 0.9884 1.4630 73.40 10.25 C,2H20O2 73.43 10.27 X 96 145-146 0.9760 1.4600 74.20 10.51 C13H22O2 74.24 10.54 XI 97 156.5-157.0 0.9868 1.4655 74.20 10.50 CBHMOZ 74.24 10.54 XII 98 177-178 0.9876 1.4666 75.60 10.74 CMHMO2 75.63 10.78 Table 4. Yields, physical properties and elemental analyses of bicyclic alcohols XIII-XVIII Compd. bp OC Found, % Calculated, % Yield, % ’ dfio n,23° Formula no. (30 mm Hg) H C H XIII 98 a - - 74.91 10.72 C7H12O 74.95 10.78 XIV 97 73-74 0.9988 1.4826 76.11 11.16 C8H14O 76.14 11.18 XV 94 98-99 0.9950 1.4836 77.00 11.50 C9H,6O 77.08 11.50 XVI 94 122-123 0.9875 1.4890 77.81 11.72 C,0H,8O 77.86 11.76 XVII 95 117-118 0.9745 1.4790 77.72 11.72 C10H18O 77.86 11.76 XVIII 95 142-143 0.9738 1.4896 78.50 11.94 CHHNO 78.51 11.97 a Melting point of compound XIII 127°C is consistent with the published data [12]. catalyst was filtered off, and the reaction mixture was subjected to fractional distillation. Compound VII was obtained in 94% yield. Compounds VIII-XII were prepared in the similar way (Table 3). 2-exo-Bicyclo[2.2.1]heptanol (XIII). To a mix- ture of 16.8 g of compound VII and 25 ml of ethanol at heating to 70°C while vigorous stirring was added within 1 h 20 ml of 20% NaOH solution. The stirring was continued for 1 h more. The reaction mixture was extracted with ether, the extract was dried with anhydrous CaCl2, the solvent was distilled off. We obtained 11 g (98%) of compound XIII. Bicyclic alcohols XIV-XVIII were prepared in the similar way; their characteristics are given in Table 4. REFERENCES 1 . Tekhnol o gi ya plasticheskikh mass (Plastics Technology), Korshak, V.V., Ed., Moscow: Khimiya, 1972, pp. 50-70. 2. Emel’yanov, N.P., Naumova, L.V., and Koz- RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 9. 10. 11. 12. 10v, N.S., Dokl. Akad. Nauk Belarus. SSR, 1967, vol. 2, no. 2, pp. 140-144. Golding, B., Khimiya i tekhnologiya polimernykh materialov (Chemistry and Technology of Polymeric Materials), Leningrad: Khimiya, 1963, p. 422. Japan Patent 61-53242, 1986; Ref Zh. Khim., 1986, 9N66P. . Japan Patent 60-226513, 1986; Ref Zh. Khim., 1986, 19S69P. Sadykhov, Sh.G., Gumbatov, E.G., Mamedov, A.A., and Musaeva, Azerb. Khim. Zh., 1983, no. 3, pp. 57-59. Mamedov, M. 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