ISSN 0965-5441, Petroleum Chemistry, 2008, Vol. 48, No. 3, pp. 206–209. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © Kh.A. Suerbaev, E.G. Chepaikin, G.Zh. Zhaksylykova, K.S. Kanybetov, T.K. Turkbenov, G.M. Abyzbekova, 2008, published in Neftekhimiya, 2008,
Vol. 48, No. 3, pp. 208–211.
Hydroxycarbonylation of Isobutylene in the Presence
of the Palladium Acetylacetonate–Triphenylphosphine–p-
Toluenesulfonic Acid Catalyst System
a
b
a
a
Kh. A. Suerbaev , E. G. Chepaikin , G. Zh. Zhaksylykova , K. S. Kanybetov ,
a
a
T. K. Turkbenov , and G. M. Abyzbekova
a
Al-Farabi Kazakh National University, ul. Al-Farabi 71, Almaty, 050038 Kazakhstan
b
Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Chernogolovka, 142432 Russia
e-mail: echep@ism.ac.ru; grig@ism.ac.ru
Received February 16, 2007
Abstract—The reaction of isobutylene hydroxycarbonylation with carbon monoxide and an alcohol (ethanol,
1
-menthol) in the presence of the palladium acetylacetonate–triphenylphosphine–p-toluenesulfonic acid cata-
lytic system was investigated. It was shown that the reaction proceeds regioselectively with the formation of
linear products (ethyl isovalerate, 1-menthyl isovalerate). The optimum conditions for running the process were
found, at which the yield of the main products is 67–79%.
DOI: 10.1134/S0965544108030067
Hydroxycarbonylation of isobutylene, a product of increased. There are also patent data that describe the
oil refining, with carbon monoxide and an alcohol in use of a synthesis gas as a source of carbon monoxide
the presence of homogeneous metal complex catalysts [7–9].
makes it possible to synthesize easily and conveniently
Earlier, we developed MIV and EBIV preparation
in one step isovaleric acid esters, which possess biolog-
methods that are more economical and environmentally
ical activity and are components of pharmaceutical
friendly than the current industrial process, with the key
compositions or valuable intermediates for their syn-
steps of the methods being, respectively, the hydromen-
thesis. Some isovalerate esters possess a characteristic
thoxycarbonylation and hydroethoxycarbonylation of
odor and are used as fragrance compounds in the man-
isobutylene with carbon monoxide in the presence of
ufacture of perfumes, cosmetics, and food essences [1].
the êdCI (PPh) –PPh –TsOH and êdCI –PPh –TsOH
2
2
3
2
3
(
[
TsOH is p-toluenesulfonic acid) catalytic systems
The menthol ester of isovaleric acid (MIV) is an
active principle of validol, a popular medicament [2]. It
is synthesized in industry via esterification of isovaleric
acid with menthol. The reactant isovaleric acid is
obtained via the two-step oxidation of isoamyl alcohol
isolated from fusel oils. The presence of the oxidation
step, along with the use of feedstock of a plant origin
10–12].
In this work, we have investigated the reactions of
isobutylene hydromenthoxycarbonylation and hydroet-
hoxycarbonylation in the presence of the halogen-free
palladium catalyst system Pd(acac) –PPh –TsOH with
2
3
the purpose of the further development of the processes
for manufacturing MIV and EBIV. The halogen-free
catalytic system is much less corrosive and does not
bring halogen in the final commercial product, thus
making it possible to abandon testing the pharmaceuti-
cal for chlorine.
(
fusel oils), results in a high content of various undesir-
able impurities in isovaleric acid. It impairs the quality
of MIV and, hence, the final medicine validol. Syn-
thetic d,l-menthol contains an admixture of d,l-isomen-
thol (up to 25%) and, therefore, the use of phytogenic
menthol (l-menthol) is more preferable, as only l-men-
thyl ester of isovaleric acid possesses biological activity
EXPERIMENTAL
[
3]. One of the main active ingredients of the medica-
ment corvalol is ethyl α-bromoisovalerate (EBIV) [2].
The complex Pd(acac) was obtained according to
2
Commercially, the ester is obtained via a complex four- the known procedure [13]. p-Toluenesulfonic acid
stage synthesis, in which the key stage is the bromina- (chemically pure grade) was recrystallized from 96%
tion of isovaleryl chloride [4]. Isobutylene hydromen- ethanol and dried until the composition TsOH · ç é.
2
thoxycarbonylation with the synthesis gas in the pres- Triphenylphosphine (chemically pure grade, Che-
ence of (PPh ) PdCl with an admixture of free triphe- mapol) was recrystallized from an ether–ethanol mix-
3
2
2
nylphosphine was reported [5, 6]. An induction period ture to a constant melting point. Absolute ethanol,
was observed, which shortened as the ratio H /CO isobutylene of 99.5% purity, carbon monoxide of
2
2
06