Nickel-catalyzed carbonylation

Nickel-catalyzed carbonylation of a-haloalkynes with carbon monoxide under phase-transfer conditions gave either allenic monoacids or unsaturated diacids.93 The carbonylation initially afforded monoacids, which reacted further to give diacids with high stereoselectivity (Eq. 4.52). 

Nickel-catalyzed carbonylation of a-ketoalkynes has also been reported by Arzoumanian et al. under phase-transfer conditions.94 The carbonylation gave either furanone or unsaturated carboxylic acids depending on the substituents of substrates (Eq. 4.53). A similar reaction, nickel-catalyzed cyanation of a-ketoalkynes with KCN in water, was also reported to afford unsaturated hydroxylactams (Eq. 4.54).95... 

It is evident that the next improvement in this technology is to develop a process that utilizes a catalyst that is less expensive but just as selective and active as rhodium. This paper describes the development of nickel catalyzed carbonylation whose performance matches the current industry standard of rhodium. 

The activity of the nickel catalyst is affected by major variations in carbon monoxide partial pressure. With very low carbon monoxide partial pressure, nickel precipitates as a metal powder and occasionally as nickel iodide. Stability of the catalyst is improved with higher CO partial pressure up to a point above which the catalyst activity drops linearly. The optimum level of carbon monoxide is different from one catalyst mixture to another. This behavior is characteristic of all the nickel catalyzed carbonylation reactions we studied. In the Li-P system, optimum carbon monoxide partial pressure is in the range of 700 to 800 psi (Table V). On the other hand, the optimum carbon monoxide partial pressure for the Li-Sn system is in the range of 220 to 250 psi, at 160 C, and 450 psi at 180 C (Table VI). It is presumed that the retarding effect of higher carbon monoxide partial pressure is associated with stabilizing an inactive carbonyl species. 

Scheme 8. Suggested mechanism for the contribution of hydrocarboxylation during the nickel-catalyzed carbonylation of higher alcohols.

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. 

Palladium is a relatively high-priced catalyst and it would be preferable if a lower-priced nickel catalyst could be used instead. All attempts, however, to form polymers by nickel-catalyzed carbonylation poly condensations of aromatic diamines with aromatic dibromides failed to yield high molecular weight materials. 

Although nickel-catalyzed carbonylative Pauson-Khand cycloadditions have not been broadly developed, related doubly carbonylative cycloadditions involving allyl halides have been demonstrated as an entry to functionalized cyclopentenones. In recent catalytic versions, iron powder was used as the terminal reductant and dehalogenating agent (Scheme 3-38). [Caution Ni(CO)4, which could potentially be liberated in this reaction, is a highly toxic gas.]... 

Even though Ni(CO)4 is called liquid death, this nickel catalyst has been applied in carbonylation reactions [52]. The group of Ricart reported a nickel-catalyzed carbonylative cycloaddition of alkynes and aUyl hahdes to cyclopentanes. The desired products were obtained in high yields and with controlled stereoselectivity. Iron was used as a reductant. An extension of the reaction to new substrates led to the conclusion that, although the steric and electronic effects of the alkyne substituents are generally irrelevant in relation to the adducts and their yields, those of the allylic counterpart may have a significant influence on the outcome of the reaction. However, the presence of the amine moiety in the alkyne completely inhibited the reaction. The feasibility of a multicentered reaction was verified with a triacetylene, in which up to 12 bonds were created simultaneously and in good yield (Scheme 1.30). 

Scheme 1.30 Nickel-catalyzed carbonylative synthesis of cyclopentanes.

Table 2.1 Nickel-catalyzed carbonylation of organo halides...

Chen and Wang described a nickel-catalyzed carbonylative Negishi coupling reactions [82]. In the presence of a catalytic amount of nickel chloride and 4,4 -dimethoxyl-2,2 -bypyridyl under carbon monoxide atmosphere, various enones were produced from enol triflates and diorganozinc reagents (Scheme 4.44). They demonstrate that the rate of CO insertion is increased by the addition of lithium or magnesium halides and the use of polar solvents. Alkenyl iodides can also be used instead of enol triflates. 

In 2008 Bhanage s team reported on a copper-catalyzed carbonylative Sonogashira reaction of aryl iodides [68]. In this procedure, copper bis(2,2,6,6-tetra-methyl-3,5-heptanedionate) [Cu(TMHD)2] was used as the catalyst for this transformation and using NEta as a base. Alkynones were produced in good yields (Scheme 5.33). A nickel-catalyzed carbonylation of allyl halides and acetylenes was reported on by Moreto and colleagues [69]. Cyclopentane skeletons were produced in high yields and with controlled stereochemistry. 

Ng, T. F. Jamison, J. Am. Chem. Soc. 2006, 128, 5362-5363. Nickel-catalyzed, carbonyl-ene-type reactions selective for alpha olefins and more efficient with electron-rich aldehydes, (c) C.-Y. Ho, T. F. Jamison, Angew. Chem. Int. Ed. 2007, 46, 782—785. Highly selective coupling of alkenes and aldehydes catalyzed by [Ni(NHC) P(OPh)j ] synergy between a strong a donor and a strong k acceptor. 

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