Solid-Phase ortho-Hydroxylation of 2,4-Di-tert-butylphenol and Its Derivatives

Article abstract of DOI:10.1134/S107042802001030X

Abstract: Direct phenol–catechol conversion has been realized as a result of the solid-phase reaction of 2,4-di-tert-butylphenol with cuprous oxide under high pressure and shear deformation on the Bridgman anvils. The yield of 3,5-di-tert-butylcatechol in this reaction was about 85%. When cupric oxide was used in the solid-phase process, oxidative coupling of the starting phenol took place, resulting in quantitative formation of tetra-tert-butyl-ortho-bisphenol. The reaction of 6-substituted derivatives of 2,4-di-tert-butylphenol with cuprous oxide was used as an example to demonstrate the possibility of substitutive ortho-hydroxylation yielding 7–20% of pyrocatechols.

Full text of DOI:10.1134/S107042802001030X

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2020, Vol. 56, No. 2, pp. 350–352. © Pleiades Publishing, Ltd., 2020.
Russian Text © The Author(s), 2020, published in Zhurnal Organicheskoi Khimii, 2020, Vol. 56, No. 2, pp. 315–318.
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Solid-Phase ortho-Hydroxylation
of 2,4-Di-tert-butylphenol and Its Derivatives
V. B. Vol’evaа, V. A. Zhorinb, N. L. Komissarovaа,*, M. N. Ovsyannikovaа,
A. V. Ryzhakovaа, and L. N. Kurkovskayaа
a Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, 119334 Russia
b Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow, 119991 Russia
*e-mail: komissarova@polymer.chph.ras.ru
Received July 18, 2019; revised November 17, 2019; accepted November 27, 2019
Abstract—Direct phenol–catechol conversion has been realized as a result of the solid-phase reaction of 2,4-di-
tert-butylphenol with cuprous oxide under high pressure and shear deformation on the Bridgman anvils. The
yield of 3,5-di-tert-butylcatechol in this reaction was about 85%. When cupric oxide was used in the solid-phase
process, oxidative coupling of the starting phenol took place, resulting in quantitative formation of tetra-tert-
butyl-ortho-bisphenol. The reaction of 6-substituted derivatives of 2,4-di-tert-butylphenol with cuprous oxide
was used as an example to demonstrate the possibility of substitutive ortho-hydroxylation yielding 7–20% of
pyrocatechols.
Keywords: 2,4-di-tert-butylphenol, 3,5-di-tert-butylcatechol, cuprous oxide, cupric oxide, solid-phase reactions,
high pressure, shear deformation, Bridgman anvils, ortho-hydroxylation, oxidative coupling
DOI: 10.1134/S107042802001030X
tert-Butylation is widely used in the chemistry of
phenols to protect certain ring positions from undesired
transformations. Moreover, the introduction of tert-
butyl groups affects the redox characteristics of phenols,
making possible transformations uncharacteristic of
unsubstituted analogs. An example of a concerted action
of these two effects is the coordination catalytic ortho-
hydroxylation of 2,4-di-tert-butylphenol 1 leading to,
3,5-di-tert-butylpyrocatechol 2; the reaction is catalyzed
by Cu (I) complexes with donor ligands (L) and occurs
in solvating solvents (Scheme 1, route a) [1, 2].
into account that an increase in the pressure enhances
donor–acceptor interactions, as well as the fact that
oxides with a low metal–oxygen binding energy are
prone to deoxygenation under the HP + SD conditions
[4]. Cuprous oxide is one of such oxides; therefore,
it can be a source of active oxygen in the solid-phase
process.
The reaction of phenol 1 with Cu2O was carried out
on Bridgman rotary anvils at the pressure of 10 kbar and
an angle of rotation of the anvils relative to each other
of 300°. The products were analyzed by TLC using
reference standards. Pyrocatechol 2, traces of a redox-
conjugated 3,5-di-tert-butyl-ortho-benzoquinone 3, and
a small amount of the starting phenol 1 were detected
in the reaction mixture. The solid-phase reaction of
Development of new synthetic approaches to
pyrocatechols is of practical importance. The natural
sources of pyrocatechol, such as coal tars, are small and
scarce. The synthesis of pyrocatechol from hydrocarbon
raw materials, including synthesis of cyclohexene,
its conversion to cyclohexanediol, and subsequent
dehydrogenation [3], is a difficult-to-implement and
costly process. Searching for alternative phenol–
pyrocatechol transformations is quite a relevant task.
Scheme 1.
In this work, we investigated the possibility of solid-
state hydroxylation of phenol 1 by its reaction with Cu2O
under exposure to high pressure and shear deformations
(HP + SD) (Scheme 1, route b). Therewith, we took
350

SOLID-PHASE ortho-HYDROXYLATION OF 2,4-DI-tert-BUTYLPHENOL
351
Scheme 2.
Scheme 3.
OH
t-Bu
R
Cu2O
2
HP + SD
t-Bu
5, 6
phenol 1 with CuO involves oxidative doubling resul-
ting in a nearly quantitative formation of 2,2',4,4'-tetra-
tert-butyl-bisphenol (4) (Scheme 2). Pyrocatechol 2
was not detected in this case.
DMF containing a drop of pyridine, filtered, the filtrate
was diluted with H2O, extracted with hexane, and the
extract was analyzed by TLC on Silufol UV 254 plates
in hexane–ether (6 : 1) using reference standards. The
conversion of the starting phenol was estimated using
reference mixtures with different phenol (1, 5, and 6)–
pyrocatechol 2 ratios (from 10 : 1 to 1 : 10).
Theexamplesof2,4-di-tert-butyl-6-bromophenol(5)
and 2,4,6-tri-tert-butylphenol (6) were used to
demonstrate the possibility of substitutive ortho-
hydroxylation under the action of Cu2O under the HP +
SD conditions to form pyrocatechol 2 (Scheme 3).
However, the conversion of the starting phenols in these
reactions is much lower.
The adequacy of the resulting estimates was
confirmed by NMR spectroscopy. For preparative
isolation of pyrocatechol 2 formed in the phenol
1–Cu2O system, we combined reaction mixtures
from 6 experiments. Phenol 1 and pyrocatechol 2
were separated by preparative TLC under the above
conditions. From 0.15 g of the mixture we isolated
0.052 g of pyrocatechol 2 together with quinone 3 and
0.007 g of the starting phenol 1, which corresponds to
a 84–85% conversion to pyrocatechol 2. The latter was
oxidized into the more stable 3,5-di-tert-butyl-ortho-
benzoquinone (3) under the action of Ag2O in hexane;
mp 111–112°С (hexane) is consistent with that reported
in [5] (Scheme 5).
Phenol 6 is easily oxidized to a stable “blue aroxyl”
radical 7. Presumably, this radical takes part in the
solid-phase process. The ortho-selectivity of the studied
solid-phase process is consistent with the observation
of Vol’eva et al. [5] that the selectivity of the reaction
of blue aroxyl with oxygen depends on whether
coordinating metal ions are present in the reaction
system (Scheme 4).
Phenol 6 is a by-product of the industrial production
of 2,6-di-tert-butylphenol; therefore, the conversion of
phenol 6 into pyrocatechol 2 present interest as one of
the possible ways of utilization of this by-product.
The conversions of phenols 5 and 6 into pyrocatechol
2, estimated using the corresponding reference
standards, were 18–20% and 5–7%, respectively. These
estimates were confirmed by NMR spectroscopy.
Binary mixtures of phenols 1, 5, and 6 with copper
oxides (Cu2O or CuO) were prepared from powdered
compounds in a 1 : 2 phenol–oxide molar ratios. About
30 mg of the mixture was taken for each experiment.
When the mixtures were exposure to HP + SD,
explosive phenomena accompanied by a strong sound
were observed. The reaction mixture was dissolved in
Thus, the solid-phase phenol–pyrocatechol
transformation under the HP + SD conditions can
contribute to the list of known methods of synthesis of
pyrocatechols.
Scheme 4.
t-Bu
O
O
O
t-Bu
t-Bu
t-Bu
O2, Mn(II)
t-Bu
O
2
t-Bu
t-Bu
O
t-Bu
t-Bu
7
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 2 2020

VOL’EVA et al.
https://doi.org/10.1039/B212683D
352
Scheme 5.
2. Chatterjee, A., Yadav, H.R., Choudhury, A.R., Ali, A.,
Singh, Y., and Ghosh, R., Polyhedron, 2018, vol. 141,
p. 140.
t-Bu
O
O
Ag2O
C6H14
2
https://doi.org/10.1016/j.poly.2017.11.040
t-Bu
3. Semenov, M.V, Komarov, A.G., Mikhailyuk, A.I., Lit-
vintsev, I.Y., and Sapunov, V.N., Pet. Chem., 1995,
vol. 35, p. 111.
3
1
The Н NMR spectra were registered on a Bruker
Avance 500 spectrometer for CDCl3 solutions, internal
reference TMS.
4. Gonikberg, M.T., Khimicheskoe ravnovesie i skorost’
reaktsii pri vysokikh davleniyakh (Chemical Equilibrium
and Reaction Rate at High Pressures), Moscow: Khimiya,
1969.
CONFLICT OF INTEREST
The authors declare no conflict of interest.
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 2 2020