HYDROETHOXYCARBONYLATION OF α-OLEFINS AT LOW PRESSURE
711
1737 cm–1 and C–O–C stretching vibrations at 1033–
FFAP, column length 30 m, inner diameter 0.25 mm,
nitroterephthalic acid modified with polyethylene
glycol as the stationary phase).
1300 cm–1) and of the СН, СН2, and СН3 groups
1
(≈729, 1300–1462, 2800–3000 cm–1). The Н NMR
parameters (CDCl3) of the products of hexene-1
hydroethoxycarbonylation corresponded to the linear
product containing the admixture of the branched one.
The most weak-field range of the spectrum contained a
quartet at 4.12 ppm (J = 7.3 Hz) assigned to the
methylene group of the ethyl substituent. The protons
of the adjacent methyl group resonated at 1.25 ppm
(triplet, J = 7.3 Hz). The most upfield range of the
spectrum contained the signals of the methyl group of
the acid part (0.88 ppm, triplet, J = 5.3 Hz). The
protons of the methylene group adjacent to the car-
bonyl one were found at 2.28 ppm (triplet, J = 7.3 Hz).
The multiplet at 1.62 ppm was assigned to the
methylene protons at the С5 atom; other methylene
groups (those at the С2, С3, and С4 atoms) were
assigned to the multiplet around 1.29 ppm. The admix-
ture of the branched isomer (ethyl α-methylcapronate)
was identified by the presence of the doublet signal of
the methyl groups at the С5 atom at 1.13 ppm (J =
6.8 Hz) and the multiplet signal of the methine proton
at the С5 atom at 2.4 ppm (J = 8.0 Hz). The signals of
other protons of the branched product were overlapped
by those of the major linear product (ethyl enanthoate).
IR spectra were recorded using a Nicolet 5700 single-
beam spectrometer (ThermoElectron Corporation,
USA) at 400–4000 cm–1. 1Н NMR spectra were
recorded using a Bruker DPX 400 instrument.
Hydroethoxycarbonylation of hexene-1. A mix-
ture of 6.637 g (7.89×10–2 mol) of hexene-1, 2.289 g
(4.97×10–2 mol) of ethanol, 0.080 g (11.42×10–5 mol)
of PdCl2(PPh3)2, 0.180 g (6.85×10–4 mol) of PPh3, and
0.122 g (9.14×10–4 mol) of AlCl3 was charged into a
100 mL stainless steel reactor equipped with a stirrer
and a carbon(II) oxide injecting device. The pressure
reactor was sealed, deaerated by flushing with car-
bon(II) oxide for three times, and filled with carbon(II)
oxide to a pressure of 10 at; then stirring and heating
were switched on. The temperature was increased to
100°С during 1 h, the pressure was up to 25 at, and the
reaction mixture was stirred under those conditions
during 5 h. Then the vessel was cooled down to
ambient, and the reaction mixture was separated by
fractionation. Yield 7.0 g (84.6%) of a mixture of ethyl
enanthoate and ethyl 2-methylcapronate (77.8 : 22.2).
IR spectrum, ν, cm–1: 1737 (С=О), 1033–1300
[СН2С(О)О], 729 (СН), 1300–1462 (СН2), 2800–3000
(СН3). Ethyl enanthoate. 1Н NMR spectrum (СDCl3),
δ, ppm: 4.12 q (2Н, СН3СН2О, J = 7.3 Hz), 1.25 t (3Н,
СН3СН2О, J = 7.3 Hz), 0.88 t [3Н, СН3(СН2)5С(О)О,
J = 5.3 Hz], 1.29 m [6Н, СН3СН2СН2СН2(СН2)2С(О)О],
1.62 m [2Н, СН3(СН2)3СН2СН2С(О)О], 2.28 t [2Н,
СН3(СН2)4СН2С(О)О, J = 7.3 Hz]. Ethyl 2-methyl-
capronate. 1Н NMR spectrum (СDCl3), δ, ppm: 1.13 d
[3Н, СН3(СН2)3СН(СН3)С(О)О, J = 6.8 Hz], 2.4 m
[1Н, СН3(СН2)3СН(СН3)С(О)О].
In summary, we observed high catalytic activity of
the PdCl2(PPh3)2–PPh3–AlCl3 three-component system
containing AlCl3 as the promotor in the reaction of
hydroethoxycarbonylation of hexene-1 and octene-1.
The reaction occurred with the formation of a pair of
isomeric products: the linear and the branched ones.
The optimal conditions of the reactions were ela-
borated, and the yield of the target products (isomeric
esters) reached 84.6 (for hexene-1) and 93.8% (for
octene-1).
Hydroethoxycarbonylation of octene-1 was per-
formed similarly using 5.6 g (5.02×10–2 mol) of octene-
1, 1.52 g (3.3×10–2 mol) of ethanol, 0.053 g (7.59×
10–5 mol) of PdCl2(PPh3)2, 0.119 g (4.55×10–4 mol) of
PPh3, and 0.081 g (6.07×10–4 mol) of AlCl3. Yield 5.76 g
(93.8%) of a mixture of ethyl pelargonate and ethyl
2-methylcaprylate (77.5 : 22.5). IR spectrum, ν, cm–1:
1738 (С=О), 1033–1260 [СН2С(О)О], 740 (СН), 1340–
1462 (СН2), 2868–2957 (СН3).
EXPERIMENTAL
The following chemicals were used as received:
hexene-1, octene-1, and dichlorobis(triphenylphos-phine)-
palladium (Sigma-Aldrich), anhydrous ethanol, alumi-
num trichloride, and carbon dioxide without special
purification. Triphenylphosphine (“pure,” Chemapol)
was recrystallized from ethanol.
The experiments were performed without solvents,
using a stainless-steel laboratory pressure reactor. The
ratio of the isomeric esters (linear and branched) was
determined by chromatography using an Agilent
7890A/5975C chromato–mass spectrometer (USA)
(ionization by electron impact, capillary column HP-
ACKNOWLEDGMENTS
This work was financially supported by the
Ministry of Education and Science of Kazakhstan
(grant no. 2743/GF-4).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 4 2017