UDC 547.597.2

CHEMISTRY

Academician B. A. ARBUZOV, Z. G. ISAEVA, V. V. RATNER

ON THE STRUCTURE OF THE OXIDE OBTAINED IN THE OXIDATION OF Δ³-CARENE WITH SELENIUM ANHYDRIDE

In the oxidation of d-Δ³-carene with selenium dioxide in acetic anhydride under the conditions described by Alkhonio (¹), we, along with unchanged Δ³-carene, p-methylisopropenylbenzene, p-menthadien-1,5-ol-8 acetate, and a ketone (m.p. 136—137° of the 2,4-dinitrophenylhydrazone), to which we tentatively assign the structure caren-4(7)-one-5 (²), isolated a compound of composition C₁₀H₁₄O (17 g from 844 g of Δ³-carene). This compound had not previously been isolated by us in any of the oxidation reactions of Δ³-carene studied (²–⁵). By chromatography on neutral alumina (activity I) the substance was obtained in the pure state and had: b.p. 61—63°/9 mm; \(n_D^{20}\) 1.5030; \(d_4^{20}\) 0.9707; \([\alpha]_D +279.6^\circ\); \(MR\) found 45.72; C₁₀H₁₄O F₂ \(MR\) calculated 44.68; \(R_f = 0.5\).

Found, %: C 79.83; 79.88; H 9.27; 9.29. C₁₀H₁₄O. Calculated, %: C 79.95; H 9.39.

The substance had a sharp odor. On storage in a sealed tube at room temperature it readily polymerized.

The data of the IR spectrum (Fig. 1) indicate the absence of carbonyl and hydroxyl groups. The oxygen evidently has an oxide character (1278, 1052, 1000, 900 cm⁻¹ (⁶)). The presence of frequencies 1636, 1592, and 887 cm⁻¹ indicates the presence of a conjugated system of double bonds, one of which is semicyclic. The doublet at 1378 and 1362 cm⁻¹ indicates the presence of an isopropyl group.

The data of the UV spectrum of the oxide (Fig. 2) make probable the presence in the compound of a β-phellandrene skeleton (\(\lambda_{\max}\) 233 mµ, \(\lg \varepsilon = 4.2\)). On reduction with LiAlH₄ the oxide remained unchanged (physical constants, IR spectrum), which indicates that the oxide does not contain an α-oxide ring. The NMR spectrum of the oxide (Fig. 3) confirms the assumptions made. The peaks \(\delta = 5.95\) and \(\delta = 5.80\) (2H) correspond to protons at a double bond in the ring, \(\delta = 4.59—4.20\) (3H) to two protons of a semicyclic bond and one pro-

Fig. 1. IR spectrum of the oxide

the CH—O group. The region $\delta = 2.20—2.00$ (3H) belongs to the CH$_2$ and CH groups in the ring. The singlet $\delta = 1.20$ (6H) corresponds to two methyl radicals. The low value $\delta = 1.20$ indicates that the gem-dimethyl group is located at a carbon atom bonded to oxygen. On the basis of the data presented, oxide C$_{10}$H$_{14}$O may be assigned structure I or II.

Reduction of the oxide (2.9 g) with sodium (1.8 g) in alcohol (18 ml), followed by chromatography on aluminum oxide, gave the starting oxide (0.38 g), pinol (0.57 g, b.p. 71—76°/21 mm, $n_D^{20}$ 1.4710, $\alpha_D^{20} +28.5^\circ$; dibromide—m.p. 92.5—93.5°, a mixed sample with pinol dibromide gave no depression) and $\alpha$-terpineol (0.67 g, b.p. 67.5°/5 mm, $n_D^{20}$ 1.4801, $[\alpha]_D = +47.55^\circ$, $d_4^{20}$ 0.9346, $\alpha$-naphthylurethane—m.p. 144—145°, a mixed sample with $\alpha$-naphthylurethane of $dl$-$\alpha$-terpineol gave no melting-point depression; the IR spectrum and NMR spectrum coincided with the spectra of $dl$-$\alpha$-terpineol). The data presented indicate that the oxide studied has structure I (2,8-oxido-$n$-menthadien-1(7),5).

Fig. 2. UV spectrum of the oxide

Fig. 3. NMR spectrum of the oxide

Further confirmation of the structure of oxide I could be provided by its oxidation with potassium permanganate, since for structure I one could expect the formation of terebic acid (m.p. 176°) (V).

Oxidation of the oxide with potassium permanganate led, however, to an acid corresponding in composition to terebic acid, but with m.p. 201—202°, $[\alpha]_D -15.5^\circ$ (C 5.13, C$_2$H$_5$OH). An acid with m.p. 202° and $[\alpha]_D -11.85^\circ$ (C 2.215, C$_2$H$_5$OH) was isolated by Simonsen upon oxidation of $\Delta^3$- and $\Delta^4$-carenes with Beckmann’s mixture and was a mixture of $l$- and $dl$-trans-caronic acids ($^7$). The formation of trans-caronic acid is inconsistent with structure I, which forced us to investigate in greater detail the acid with m.p. 201—202° obtained from the oxide. The acid with m.p. 201—202° could be $l$-terebic acid (m.p. 201—204°), isolated by Dellepine ($^8$) and Matsui ($^9$). To prove the identity of the acid with m.p. 201—202° with $l$-terebic acid

IR spectra and NMR spectra were taken of this acid, of dl-terebic acid with m.p. 174.5–175.5°, obtained by oxidation of pinol, and of trans-caronic acid with m.p. 211–212°, obtained by oxidation of $\Delta^3$-carene with potassium permanganate. The IR spectra of the named acids are shown in Fig. 4. As can be seen from Fig. 4, the spectra of the acid with m.p. 201–202° and of dl-terebic acid coincide almost completely. They contain bands at 1734 and 1737 cm$^{-1}$, respectively, corresponding to the lactone carbonyl.

Fig. 4. IR spectra (oil): a — acid with m.p. 201–202°, b — dl-terebic acid with m.p. 174.5–175.5°, c — trans-caronic acid with m.p. 211–212°.

In the IR spectrum of trans-caronic acid the band at 1740 cm\(^{-1}\) is absent, and the absorption band of the \(C{=}O\) of the carboxyl group is present (1686 cm\(^{-1}\)). The NMR spectra of the acid with m.p. 201–202° and of \(dl\)-terebinic acid (in CD\(_3\)OD) proved to be very similar and contained peaks at \(\delta = 2.93\) (3H), corresponding to the protons of the CH\(_2\) group and to the proton of the CH group at the carboxyl group (\(^{10,11}\)), and a doublet at \(\delta = 1.45\) and 1.27 (6H) of the gem-dimethyl group (\(^{12}\)). The spectrum of trans-caronic acid (in CD\(_3\)OD) differed from the spectrum of the acid with m.p. 201–202° and contained a peak at \(\delta = 1.97\) (2H) of the protons at the carbons bonded to the carboxyl groups (\(^{13}\)), and a peak at \(\delta = 1.20\) (6H) of the gem-dimethyl grouping* (\(^{14}\)). The data presented prove the structure of the acid with m.p. 201–202° as \(l\)-terebinic acid.

We carried out experiments on the counter-synthesis of oxide I, starting from pinol (III). Pinol was obtained through \(\alpha\)-pinene oxide and \(dl\)-sobrerol. \(dl\)-Pinol was converted into pinolglycol diacetate (VIII) either through the dibromide (VI), or through pinolglycol (VII). Pyrolysis of the diacetate was carried out in vacuum (100 mm) in dibutyl phthalate, in the presence of naphthalenesulfonic acid (\(^{15}\)) with gradual raising of the temperature to 260° (5 g of diacetate, 0.1 g of \(\beta\)-naphthalenesulfonic acid, and 16 ml of dibutyl phthalate; the experiment was carried out twice).

The pyrolysis product (2.4 g), after chromatography, gave a fraction which, in physical constants, odor, IR and NMR spectra, was close to oxide I. In pure form, however, the oxide could not be isolated. Oxidation of the chromatography product with potassium permanganate gave \(dl\)-terebinic acid with m.p. 174–175° (since the initial pinol was the \(dl\)-form, oxide I should have been obtained in the \(dl\)-form). The data presented confirm the structure of the oxide C\(_{10}\)H\(_{14}\)O (I)***.

Scientific-Research Chemical Institute
named after A. M. Butlerov
at Kazan State University
named after V. I. Ulyanov-Lenin

Received
3 V 1965

REFERENCES

1. J. Alkonji, Chem. Ber., 94, 2486 (1961).
2. Б. А. Арбузов, З. Г. Исаева, В. В. Ратнер, Изв. АН СССР, ОХН, 1965, No. 3, 475.
3. Б. А. Арбузов, З. Г. Исаева, В. В. Ратнер, ДАН, 134, 583 (1960).
4. Б. А. Арбузов, З. Г. Исаева, В. В. Ратнер, Изв. АН СССР, ОХН, 1962, No. 4, 644.
5. Б. А. Арбузов, З. Г. Исаева и др., Изв. АН СССР, ОХН, 1965, No. 3, 466.
6. П. И. Беллами, Инфракрасные спектры сложных молекул, ИЛ, 1963, p. 168.
7. G. S. Gibson, J. L. Simonsen, J. Chem. Soc., London, 1929, 307, 909.
8. M. Delepine, M. Badoche, C. R., 235, 1069 (1952); Chem. Abstr., 47, 1048 i (1953).
9. M. Matsui, T. Oprno et al., Bull. Chem. Soc. Japan, 25, 210 (1952); Chem. Abstr., 47, 12269 (1953).
10. J. Jackman, Applications of n.m.r. Spectroscopy in Organic Chemistry, 58, London, 1959, p. 57.
11. H. Conroy, Advances in Organic Chemistry, 2, 1960, p. 287.
12. C. E. Berkoff, L. Crombie, J. Chem. Soc., 1960, 3734.
13. K. B. Wieberg, B. J. Nist, J. Am. Chem. Soc., 85, 2788 (1963).
14. G. L. Closs, L. E. Closs, J. Am. Chem. Soc., 85, 100 (1963).
15. M. P. Cava et al., J. Am. Chem. Soc., 78, 2303 (1956).

* The spectrum had a peak (\(\delta = 5.00\)) corresponding to CD\(_3\)OH, probably arising through exchange of the proton of the carboxyl group for deuterium of deuteriomethanol.
* Peak \(\delta = 5.45\), corresponding to CD\(_3\)OH.
** For recording the IR, UV, and NMR spectra we express our gratitude to I. P. Popovaya, E. G. Yarkova, and A. A. Musina. The IR spectra were obtained on a Hilger H-800 spectrometer with a NaCl prism. The UV spectra were measured on an SF-4 spectrophotometer. The NMR spectra were recorded on a YaMR-KGU-1 NMR spectrometer.