doi:10.1016/j.jorganchem.2005.05.031 
Copyright © 2005 Elsevier B.V. All rights reserved.
Palladium-catalyzed hydroesterification of styrene derivatives in the presence of ionic liquids
Marc A. Klingshirn1, Robin D. Rogers and Kevin H. Shaughnessy
, 
Department of Chemistry and the Center for Green Manufacturing, The University of Alabama, P.O. Box 870336, Tuscaloosa, AL 35487-0336, USA
Received 21 April 2005;
revised 18 May 2005;
accepted 24 May 2005.
Available online 28 June 2005.
References and further reading may be available for this article. To view references and further reading you must
purchase this article.
Abstract
The palladium-catalyzed hydroesterification of olefins occurs efficiently in a range of ionic liquid media. Selectivities ranging from 5–7:1 for the linear ester were obtained with styrene in a range of IL solvents. The use of ILs allowed the catalyst to be easily separated from the organic product by either extraction or distillation. The (Ph3P)2PdCl2 precatalyst could be recovered unchanged from the ionic liquid phase. The IL/catalyst phase could be recycled five times with an average yield of 68%.
Graphical abstract
Hydroesterification of styrene derivatives and 1-octene was achieved in good yield in ionic liquid solvents. Both styrenes and 1-octene gave good linear:branch product selectivities. The catalyst/IL phase could be recycled up to 5 times with an average yield of 68%.
Keywords: Ionic liquids; Hydroesterification; Palladium; Catalyst recycling
Fig. 1. Typical ionic liquid cations and anions.
Scheme 1. Competing neutral and cationic catalytic cycles showing major project expected for each pathway.
Table 1.
Optimization of hydroesterification of styrene and carbon monoxidea
a IL = [C
4mim][NTf
2 ], styrene (0.25 mL), (Ph
3P)
2PdCl
2 (2.3 mol%), Ph
3P (4.6 mol%),
t = 6 h.
b Yields and
l:
b ratio were determined by GC.
c l:
b = linear to branched product ratio.
Table 2.
Solvent screening for palladium-catalyzed hydroesterification of styrenea
a 4 mL IL, 4 mL methanol, 90 °C, 200 psi CO, styrene (0.50 mL), (Ph
3P)
2PdCl
2 (1.2 mol%), Ph
3P (2.3 mol%),
t = 3 h.
b Yields were determined by GC.
c l:
b = linear to branched product ratio, NA = not applicable.
d Addition of 0.5 wt% [C
4mim][Cl] relative to [C
4mim][NTf
2].
Table 3.
Hydroesterification of various alkenes under optimum conditionsa
a 4 mL [C
4mim][NTf
2], 4 mL methanol, 90 °C, 200 psi CO,
t = 3 h.
b Product distribution determined from
1H NMR spectra of the distilled product mixtures. n.d., none detected.
c Methanol addition product.
d Linear ester.
e Branched ester.
Table 4.
Recycling of IL-catalyst solution used in the hydroesterification of styrenea
a 4 mL [C
4mim][NTf
2] IL, 4 mL methanol, 70 °C, 200 psi CO, 0.25 mL styrene. Runs 2–6 used IL/catalyst solution recovered from the previous run.
b Determined by GC.
c l:
b = linear to branched product ratio determined by GC.
Table 5.
Solvent properties of ionic liquids
a Literature value determined from Reichardt’s dye
[31].
b Kamlet–Taft polarizability parameter (literature values)
[38].
c Kamlet–Taft hydrogen bond acidity parameter (literature values)
[38].
d Kamlet–Taft hydrogen bond basicity parameter (literature values)
[38].
e Calculated solubility of CO at 1 bar using Henry’s constant (literature values)
[39].
f Measured using solvatochromic dyes
p-nitroaniline and
N,
N-diethyl
p-nitroaniline by the method of Kamlet and Taft
[30].
Abstract
Purchase PDF (166 K)
E-mail Article
Add to my Quick Links
Cited By in Scopus (11)
Purchase PDF (173 K)
