Alkenes palladium hydration

The hydration of propylene with sulfuric acid catalyst in high-temperature water was investigated using a flow reaction system.31 The major product is isopropanol. A biopolymer-metal complex, wool-supported palladium-iron complex (wool-Pd-Fe), has been found to be a highly active catalyst for the hydration of some alkenes to the corresponding alcohols. The yield is greatly affected by the Pd/Fe molar ratio in the wool-Pd-Fe complex catalyst and the catalyst can be reused several times without remarkable change in the catalytic activity.32... 

Ibuprofen (+) -2- (4-Isobutylphenyl) propionic acid Aromatic alkylation, HF-catalyzed aromatic acetylation, palladium-catlayzed carbonylation, alkene hydration... 

This combination of reagents h s been used to oxidize terminal vinyl groups to methyl ketones and is known as the Wacker oxidation. The nucleophile is simply water, which attacks the activated alkene at the more substituted end in an oxypalladation step. (3-Hydride elimination from the resulting a-alkyl palladium complex releases the enol, which is rapidly converted into the more stable keto form. Overall, the reaction is a hydration of a terminal alkene that can tolerate a range of functional groups. 

This is ordinary electrophilic addition, with rate-determining protonation as the first step. Certain other alkynes have also been hydrated to ketones with strong acids in the absence of mercuric salts. Simple alkynes can also be converted to ketones by heating with formic acid, without a catalyst.Lactones have been prepared from trimethylsilyl alkenes containing an hydroxyl unit elsewhere in the molecule, when reacted with molecular oxygen, CuCla, and a palladium catalyst. ... 

The definitions of oxidation and rednction and potential sources of confusion associated with them are discussed in Sect. VII.1. Some chemists mistakenly think that hydration of ethylene to give ethanol is an oxidation process, but no net oxidation or reduction takes place in hydration of ethylene. On the other hand, hydration of ethylene-palladium complexes to give acetaldehyde (the Wacker oxidation) (Sect. V.3.1) is a genuine two-electron oxidation reaction. If one determines the formal oxidation states (FOS) of the participating atoms (i.e., C and Pd) in the examples shown in Scheme 1, the difference between simple alkene hydration and the Wacker oxidation (Sect. V.3.1.1) is very clear. The formal oxidation states of the other atoms in these reactions do not change. 

Recently, Dong et al. reported a multicatalytic cascade reaction combining Pd, acid, and Ru catalysis [11]. By coupling palladium-catalyzed oxidation, acid-catalyzed hydrolysis, and ruthenium-catalyzed reduction, the elusive anti-Markovnikov olefin hydration was formally achieved, affording primary alcohols from waters and aryl-substituted terminal alkenes (Scheme 9.8). 

The hydration of C-C multiple bonds is a reaction with prevalent industrial interest due to the usefulness of the products as chemical intermediates. The wool-Pd complex is an economical and highly active catalyst for hydration of olefins. It is very stable and can be reused several times without any remarkable change in the catalytic activity [73, 74]. In particular, to convert alkenes to the corresponding alcohols in excellent enantioselectivity, a new biopolymer-metal complex constituted of wool-supported palladium-iron or palladium-cobalt was prepared and used, such as allylamine to amino-2-propanoI, acrylonitrile to lactonitrile and unsaturated acids to a-hydroxycarboxylic acids [75-77]. The same catalytic system was also used for hydration of substituted styrenes to produce chiral benzyl alcohols. The simple and cleaner procedure, mild reaction conditions, high stability and recovery rate of catalyst made these catalytic systems an attractive and useful alternative to the existing methods (Scheme 37). 

Lei X, Bin J, Li T, Xiao FJ, Mei YH, Ying YJ (2004) Asymmetric hydration of alkenes catalyzed by wool-palladium complex. Polym Adv Technol 15 346-349... 

Jia B, Yang X, Huang M-Y, Jiang Y-Y (2003) Hydration of alkenes catalyzed by wool-palladium-iron complex. React Func Polym 57 163-168... 

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