OXIDATION OF
α
ꢀPINENE BY ATMOSPHERIC OXYGEN
195
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air in the reaction mixture has almost no effect on the
direction of isomerization of ꢀpinene
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α
2.
4. I. V. Il’ina, K. P. Volcho, D. V. Korchagina, et al., Helv.
The enantioselectivity of reactions plays a significant
role in isomerization and oxidation of ꢀpinene
Thus, almost complete racemization of camphene
under the reaction conditions is a formidable problem
emerging upon performing the isomerization of
Chim. Acta 89, 507 (2006).
α
2.
5
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The short contact times typical when performing the
reaction in the supercritical solution in a continuousꢀ
flow reactor give grounds for expecting a lower racemꢀ
ization level than that observed under “normal” condiꢀ
tions. The enantiomeric excess in certain products of
8. A. V. Pavlova, T. G. Tolstikova, E. A. Morozova, et al.,
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9. T. G. Tolstikova, A. V. Pavlova, M. P. Dolgikh, et al.,
compound
tions in the presence of air in this work was determined
by GLCꢀMS in the chiral phase. (+)ꢀ ꢀPinene with
53% enantiomeric excess was used to perform the conꢀ
versions. The isomerization of (+)ꢀ ꢀpinene into
camphene and limonene was accompanied only by
2 transformation under supercritical condiꢀ
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α
2
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8,
5
3
partial racemization, the enantiomeric excess in these
compounds being 38–39%. The products of oxidation
12. M. P. Corvi and A. Ranise, Verbenone Derivatives:
EP1212292 (2004).
(verbenone
phone 13) and acetoxylation (
are formed from (+)ꢀ
lectivity.
1, campholenic aldehyde 11, and pinocamꢀ
13. M. Lajunen and A. M. P. Koskinen, Tetrahedron Lett.
α
ꢀfenchyl acetate 17
)
35, 4461 (1994).
αꢀpinene
2
with high enantioseꢀ
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15. V. I. Anikeev, I. V. Il’ina, K. P. Volcho, et al., Russ. J.
Note finally that the reactivity of monoterpene
(+)ꢀ ꢀpinene in the presence of cobalt catalyst in
Phys. Chem. A 84, 1112 (2010).
α
2
the complex supercritical solvent consisting of CO2
and ethyl acetate was studied for the first time. Comꢀ
pounds with bicyclo[2.2.1]heptane and paraꢀmenꢀ
thane backbones were shown to be major isomerizaꢀ
tion products, with the reaction being accompanied by
partial racemization. The formation of oxidation
products is observed in the presence of air; epoxydaꢀ
tion rather than allylic oxidation is the process that
predominates at the first stage. The oxidized products
(campholenic aldehyde, verbenone, pinocamphone)
are formed with high enantioselectivity. The formation
of acetoxylation products is observed at temperatures
over 200°С; they are apparently formed by the interacꢀ
tion between ethyl acetate and monoterpene.
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ACKNOWLEDGMENTS
This work was financially supported by the Russian
Foundation for Basic Research, project no. 11ꢀ08ꢀ171.
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RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
Vol. 86
No. 2 2012