Palladium acetate/Potassium formate

Another interesting application of microwave irradiation is found in the selective dehalogenation of the iodinated indole alkaloid Plakohypaphorine F, described by E. Fattorusso et al. [117,118] (Scheme 32). The bis-halogenated compound was treated with potassium formate and palladium acetate under controlled microwave irradiation, resulting in selective deiodination. The choice of the solvent, in this case DMSO, was found to be crucial. 

Reduction of the double bond of (2-pyridyl)acrylates (XI-53) without reducing the ester group in order to obtain 2-pyridylpropionates (XI-54) was accomplished in good yields by using either a mixture of phosphorus with 57% hydriodic acid in acetic acid" or by hydrogenation over platinum oxide" or 10% palladium-on-carbon in acetic acid. Treatment of the betaine of either the 2- or 4-pyridineacrylate (XI-S5) with fused potassium formate in formic acid also... 

The palladium-catalyzed domino assembly of norbornene (65), the ds-alkenyl iodide 66, and a terminal alkyne or cyanide reported by Torii, Okumoto et al. [315] provides an example for a sequence of oxidative addition, intermolecular double bond insertion, and interception of a copper acetylide or potassium cyanide. These reactions with acetylenes have been performed in good yields in the presence of diethylamine, tetra-n-butylammonium chloride, and catalytic amounts of palladium acetate, triphenylphosphine, and copper] I) iodide. Remarkably, they are characterized by complete inversion of the cis configuration of the alkenyl iodide and a high degree of discrimination for the enantiotopic ends of the double bond in norbornene. To account for that, intermediate formation of a cyclopropylcarbinyl-palladium species by a 3-exo-trig cyclization in 67 and subsequent cycloreversion to a new homoallylpalladium intermediate as the direct precursor to 68 and 69 has been assumed. Thus, the products 68 and 69 are formed virtually with complete stereoselectivity (Scheme 8.17). 

Alkaline condensation of 4-isopropylbenzaldehyde and propanal results, via the aldol, in the formation of 2-methyl-3-(4-isopropylphenyl)-2-propenal. The unsaturated aldehyde is hydrogenated selectively to the saturated aldehyde in the presence of potassium acetate and a suitable catalyst, such as palladium alumina [150] ... 

The role of gold in the Pd/Au/K acetate catalysts is to stabilize the size of Pd crystallites and avoid sintering. The role of potassium acetate is to maintain the catalyst activity and decrease CO2 selectivity. Potassium acetate favours a strong adsorption of acetic acid on palladium, lowering the barrier to vinyl acetate formation. Gold by itself is inactive in the catalysis of vinyl acetate. Pd only catalysts produce vinyl acetate at much lower rates than the Pd/Au/K catalyst system and their activity decays rapidly. 

Hydroxycarbonylation of vinyl triflates/halides has received considerable attention. The formation of carboxylic acids from palladium-catalyzed carbonylation of vinyl triflates is presumed to occur through the intermediacy of an unstable mixed anhydride. Hydroxycarbonylation of vinyl triflates has been reported to occur at room temperature in DMF under a CO balloon in the presence of Pd(OAc)2(PPh3)2 and potassium acetate [55]. The crucial role of the acetate anion is supported when the starting triflate is recovered after it has been reacted under usual conditions omitting potassium acetate. Acrylic acids have been obtained by palladium-catalyzed... 

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