Nickel-catalyzed reactions double carbonylation

Nickel cyanide catalyzes the PTC carbonylation of vinyl halides to a,y9-unsat-urated acids [141]. A similar reaction involving 2-bromo-l-phenyl-l,3-butadiene gives the a-ketolactone (60%) and dienoic acid (15 %) (the former results from the double carbonylation reaction (eq. (11)) [142]), possibly proceeding via a nickel metallacycle [143]. 

The nickel-catalyzed carbonylation of allyl halides in the presence of alkynes and water produces 2,5-dienoic acids in good yields under very mild conditions (equation 25). This remarkable four-component reaction probably involves oxidative addition of the allyl chloride to the catalyst, followed by successive insertions of alkyne and CO, and finally hydrolysis. The carbon-carbon double bond derived from alkyne insertion is thus conjugated with the carbonyl group and generally has the (Z)-configuration. 

H.ii. Double Carbonylation Reactions Catalyzed by Nickel Complexes... 

Transition metals can display selectivities for either carbonyls or olefins (Table 20.3). RuCl2(PPh3)3 (24) catalyzes reduction of the C-C double bond function in the presence of a ketone function (Table 20.3, entries 1-3). With this catalyst, reaction rates of the reduction of alkenes are usually higher than for ketones. This is also the case with various iridium catalysts (entries 6-14) and a ruthenium catalyst (entry 15). One of the few transition-metal catalysts that shows good selectivity towards the ketone or aldehyde function is the nickel catalyst (entries 4 and 5). Many other catalysts have never been tested for their selectivity for one particular functional group. 

Acrylonitrile and related compounds displace all the carbonyl groups from nickel carbonyl to form [(RCH CHCN)2Ni], in which the nitrile bonds through the olefinic double bond 222, 418). The bis(acrylonitrile) complex catalyzes many reactions, including the conversion of acrylonitrile and acetylene to heptatrienenitrile and the polymerization of acetylene to cyclooctatetraene 418). Cobalt carbonyl gave a brown-red amorphous material with acrylonitrile, which had i cn absorptions typical of uncoordinated nitrile groups, but interestingly, the presence of C=N groups was also indicated 419). In acidic methanol, cobalt carbonyl converts a,j8-unsaturated nitriles to saturated aldehydes 459). 

Besides nickel and cobalt, almost all of the catalysts discussed in the last chapter which were suited for the formation of free acids can be applied, e. g. rhodium, palladium and, with certain restrictions, iron. Cobalt hydrocarbonyl catalyzes the stoichiometric ester synthesis at mild reaction conditions [35, 121]. The initially formed acylcobalt carbonyls react rapidly with alcohols even at 50 °C and, in the presence of Na-alcoholate, even at 0 °C to give esters [121]. Dienes with isolated double bonds react with carbon monoxide and alcohols at mild reaction conditions in the presence of Pd/HCl to give unsaturated monocarboxylic acid esters and at more severe conditions to give saturated dicarboxylic acid esters [508]. 

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