Reductions carboxylic acids, palladium® acetate

Palladium-carbon/sulfuric acid Reductive N-alkylation of carboxylic acid amides with acetals... 

Esters of racemic pyrazolidine-3-carboxylic acid (5-azaproline, 16) are obtained by a two-step reaction via addition of diazomethane to acrylic acid esters to form the corresponding dihydropyrazoline derivatives, which are converted into the desired pyrazolidine-3-carb-oxylic acid derivative by hydrogenation over palladium on charcoal,11621 or by reduction with sodium cyanoborohydride,[164l or with zinc in acetic acid. Details are given in Table 6J1651... 

Compound A, C7H12, was found to be optically active. On catalytic reduction over a palladium catalyst, 2 equivalents of hydrogen were absorbed, yielding compound B, C7Hm. On ozonolysis of A, two fragments were obtained. One fragment was identified as acetic acid. The other fragment, compound C, was an optically active carboxylic acid, C5H o02- Write the reactions, and draw structures for A, B, and C. 

Such oxidative addition of carboxylic anhydride also takes place to electron rich Pd(0) complexes, and hydrogenolysis of the resulting complex gives corresponding aldehyde and carboxylic acid. For example, reaction of Pd(styrene)(PMe3)2 with acetic anhydride leads to oxidative addition of the C-0 bond to give (acetyl)(acetato)palladium(II) complex, which reacts with atmospheric H2 to give acetaldehyde, acetic acid, and ethanol (Scheme 3.37) [73]. Ethanol may be produced by reduction of acetaldehyde. 

Palladium-carbon sodium acetate Aldehydes from carboxylic acid chlorides Modified Rosenmund-Zetzscfae reduction... 

Catalytic reduction of 7-(l-chloroalkyl)-8-chloro-9-[(dimethylamino-methylene)amino]-4-oxo-4//-pyrido[ 1,2-a]pyrimidine-3-carboxylate 331 over 10% palladium-on-charcoal with hydrogen in acetic acid gave 7-alkyl-9-[(dimethylaminomethylene)amino]-4-oxo-4//-pyrido[l,2- ]pyrimidine-3-carboxylates 332 (91H1455). 

Even on prolonged hydrogenation under these conditions, only 23 per cent of the product was the 2,3-dihydro compound. When Raney nickel (p. 90) or platinum oxide [159] is present, reduction of the double bond at the 2,3-positions frequently occurs. When ethyl 6-chlorochromone-2-carboxylate was reduced with zinc dust and acetic acid, a dimeric chromanone was obtained [25a]. Hydrogenolysis of the chlorine and reduction of the pyrone ring occurred with hydrogen and palladium-charcoal [25a]. 

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