Styrenes hydroxycarbonylation, palladium

The critical role of the counter anion in the hydroxycarbonylation of styrene for different phosphorus-modified palladium systems has been reported. The regioselectivity can be controlled... 

Several Pd11 complexes with thiolate or thioether derivative ligands have been studied to be applied in the hydroxycarbonylation reaction.394 Aminothiolate complexes of palladium with PPh3 catalyze the conversion of styrene to 2-phenylpropionic acid in high yield and excellent regioselectivity.644 Under mild conditions and in the presence of a catalytic amount of an S, TV-chelated palladium or//zo-amino-arenethiolate complex, styrene reacts with CO and oxalic acid or water to selectively give 2-phenylpropanic aid in high yield.645... 

In order to keep the mild conditions, hydroxycarbonylation has been performed in biphasic media, maintaining the catalyst in the aqueous phase thanks to water-soluble mono- or diphosphine ligands. In the presence of the sodium salt of trisulfonated triphenylphosphine (TPPTS), palladium was shown to carbonylate efficiently acrylic ester [19], propene and light alkenes [20,21] in acidic media. For heavy alkenes the reduced activity due to the mass transfer problems between the aqueous and organic phases can be overcome by introducing an inverse phase transfer agent, and particularly dimeihyl-/-i-cyclodextrin [22,23]. Moreover, a dicationic palladium center coordinated by the bidentate diphosphine ligand 2,7-bis(sulfonato)xantphos (Fig. 2) catalyzes, in the presence of tolylsulfonic acid for stability reasons, the hydroxycarbonylation of ethylene, propene and styrene and provides a ca. 0.34 0.66 molar ratio for the two linear and branched acids [24],... 

The hydrocarboxylation of styrene (Scheme 5.12) and styrene derivatives results in the formation of arylpropionic acids. Members of the a-arylpropionic acid family are potent non-steroidal anti-inflammatory dmgs (Ibuprofen, Naproxen etc.), therefore a direct and simple route to such compounds is of considerable industrial interest. In fact, there are several patents describing the production of a-arylpropionic acids by hydroxycarbonylation [51,53] (several more listed in [52]). The carbonylation of styrene itself serves as a useful test reaction in order to learn the properties of new catalytic systems, such as activity, selectivity to acids, regioselectivity (1/b ratio) and enantioselectivity (e.e.) in the branched product. In aqueous or in aqueous/organic biphasic systems complexes of palladium were studied exclusively, and the results are summarized in Table 5.2. 

The Carbonylative Heck Reaction is not the same as those that were traditionally called Heck carbonylations . Heck carbonylations normally include alkoxycarbonylation, aminocarbonylation and hydroxycarbonylation, while a carbonylative Heck reaction is more related to a Heck reaction. In the late 1960s, Richard Heck developed several coupling reactions of arylmercury compounds in the presence of either stoichiometric or catalytic amounts of palladium salts [1-7]. Based on this work in 1972, he described a protocol for the coupling of iodo-benzene with styrene, which today is known as the Heck reaction [8]. In contrast to this, the catalytic insertion of olefins into acylpalladium complexes is called a Carbonylative Heck reaction . Here the acylpalladium complexes can either by CO insertion or by the oxidative addition of benzoyl precursors [9, 10]. 

Frew JJR, Damian K, Van Rensburg H, Slawin AMZ, Tooze RP, Clarke ML. Palladium(tf) complexes of new bulky bidentate phosphanes active and highly regioselective catalysts for the hydroxycarbonylation of styrene. Chem. Eur. J. 2009 15 10504-10513. 

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