926-36-3Relevant articles and documents
Palladium/Copper-catalyzed Oxidation of Aliphatic Terminal Alkenes to Aldehydes Assisted by p-Benzoquinone
Komori, Saki,Yamaguchi, Yoshiko,Murakami, Yuka,Kataoka, Yasutaka,Ura, Yasuyuki
, p. 3946 - 3955 (2020/07/06)
The development of an anti-Markovnikov Wacker-type oxidation for simple aliphatic alkenes is a significant challenge. Herein, a variety of aldehydes can be selectively obtained from various unbiased aliphatic terminal alkenes using PdCl2(MeCN)2/CuCl in the presence of p-benzoquinone (BQ) under mild reaction conditions. Isomerization of the terminal alkene to the internal alkene was suppressed via slow addition of the starting material to the reaction mixture. In addition to the Pd catalyst, CuCl and BQ were essential in order to obtain the anti-Markovnikov product with high selectivity. Terminal alkenes bearing a halogen substituent afforded their corresponding aldehydes with high anti-Markovnikov selectivity. The halogen acts as a directing group in the reaction. DFT calculations indicate that a μ-chloro Pd(II)?Cu(I) bimetallic species with BQ coordinated to Cu is the catalytically active species in the case of a terminal alkene without a directing group.
Crucial role of additives in iridium-catalyzed hydroformylation
Behr, Arno,K?mper, Alexander,Nickel, Martin,Franke, Robert
, p. 243 - 248 (2015/09/01)
Abstract This paper presents the new highly selective iridium-catalyzed hydroformylation of 1-octene with an Ir(cod)(acac)/PPh3/salt catalyst system. The addition of inorganic salts such as LiCl suppresses the hydrogenation of 1-octene and increases the yield of desired hydroformylation products. Even low amounts of LiCl (LiCl/Ir = 2/1) significantly increase the chemoselectivity of aldehydes up to 94% with a 1-octene conversion of 90% within 7 h. This catalyst is applicable to other alkenes such as 1-pentene or 1-dodecene. The high selectivities and the remarkable activity of the optimized iridium catalyst are promising in terms of successfully implementing on an industrial scale in the future.
Kinetic explanation for the temperature dependence of the regioselectivity in the hydroformylation of neohexene
Gueven, Sabriye,Nieuwenhuizen, Marko M. L.,Hamers, Bart,Franke, Robert,Priske, Markus,Becker, Marc,Vogt, Dieter
, p. 603 - 610 (2014/03/21)
The kinetics of Rh-catalyzed neohexene hydroformylation were investigated with the bulky monodentate ligand tris(2,4-di-tert-butylphenyl)phosphite. The hydrogenolysis of the Rh-acyl intermediate was identified as the rate-limiting step for both the linear and the branched aldehydes. Rate equations for both aldehydes were derived and kinetic parameters were estimated. Increased aldehyde linearity at higher temperatures, frequently observed in hydroformylation, was elucidated by deuterioformylation experiments. These showed that at 100 °C the formation of linear Rh-alkyl was more reversible than the formation of the branched derivative. The ratio of linear to branched Rh-acyl species was determined by in situ high-pressure IR spectroscopy experiments, which allowed the difference in the activation energies for the hydrogenolysis steps towards the aldehyde isomers to be quantified. The hydrogenolysis of Rh-acyl was found to be the step that caused the greatest temperature effect on the regioselectivity. Kinetics arouses curiosity: Studying the kinetics of neohexene hydroformylation catalyzed by a bulky-phosphite-modified Rh catalyst brings up the question: "What is the reason behind the temperature dependence of regioselectivity?" We answer this question by using mechanistic tools such as deuterium labeling and in situ IR spectroscopy. The hydrogenolysis step of the catalytic cycle seems to be the main step that is responsible. Copyright
