Allyl halides, carbonylation unsaturated acids

PdCl2(tppms)2 was also used as a catalyst for the atmospheric pressure carbonylation of allyl halides at 30-50°C in the presence of sodium hydroxide or alkoxides to afford P,y-unsaturated acids or esters in yields up to 93% (P,y/a,p ratio 87/13) in biphasic or monophasic methanolic media.55,56,473,474... 

Carbonylation of allylic as well as benzylic halides occurred readily in a two-phase aqueous sodium hydroxide/heptane system at atmospheric pressure and room temperature in the presence of PdCl2(tppms)2 as the catalyst giving y-unsaturated acids in moderate yields [77, 78]. The addition of surfactants such as n-C7Hi5S03Na or n-C7HisC02Na accelerated the carbonylation reaction. 

Nickel carbonyl, however, does not react with acids to form such complexes. Nevertheless, it is possible that a reaction similar to (2) could occur with an intermediate alkyne-nickel carbonyl complex, giving rise to the formation of an alkenylnickel dicarbonyl halide, RCH=CH—Ni(CO)2X, which could then yield the unsaturated acid according to Eq. (3a) or (3b) 12). This reaction formally would resemble the carbonylation of allyl halides, discussed in Section II, C. Divinyl ketones may be formed as by-products of carbonylation 13), and the stereochemistry of addition to the acetylenic linkage is reported to be exclusively cis 13). 

Malonic acid labeled with carbon-14 at C2 or at Cl,3 and the corresponding mono- and diesters have become important and highly versatile building blocks for the synthesis of a broad range of labeled compounds, such a,/3-unsaturated acids and esters, cycloalkanes, 8-keto esters, a-amino acids, phenols, dihydropyridines/pyridines, pyrimidines and quinolines. In addition, they are widely used as acetic acid synthons ( CH2COOR CHCOOR) for the extension of carbon chains of alkyl, allyl and benzyl halides as well as of saturated and a,)8-unsaturated carbonyl compounds. This Section discusses aU malonates, wherever labeled, and unlabeled malonates used with carbon-14-labeled reaction partners. However, it is the [2- " C]malonates that have been most often used in radiochemical synthesis. 

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