Nickel-catalysed reactions insertion

A nickel-catalysed alkyne insertion between the carbonyl carbon and the -carbon of the cyclobutanone was achieved by combining a ketone-alkyne coupling reaction with a /3-carbon elimination process (Scheme 79).121 The reaction uses cyclobutanones as a four-carbon unit and provides access to substituted cyclohexenones. 

A wide range of substituted isoquinolines (93) have been synthesized via a highly efficient nickel-catalysed annulation of the r-butylimines of 2-iodobenzaldehydes (91) and various alkynes (92) examination of the regiochemistry of the reaction revealed the operation of two different alkyne insertion pathways.119... 

Compared with palladium-catalysed Heck reactions, the studies of nickel-catalysed Heck reactions are far fewer. Theoretical studies show that oxidative addition and olefin insertion occur easier in the nickel system than in the palladium system. On the other hand, p-hydride elimination and catalyst regeneration through HX removal are more difficult in a nickel-based catalytic system." The former characters may make the nickel-catalysed Heck reaction of alkenyl or aryl chloride proceed relatively easily and the latter... 

A nickel-catalysed [4-1-2] cycloaddition of formamides with allgmes through double C-H activation as shown in Scheme 14.67 was also carried out in the presence of AlMes, forming dihydropyridones along with a,p-unsaturated amides as side products. The side products were formed via insertion of alkynes into the C(0)-H bond. Use of PtBus as a ligand is crucial for the success of the reaction. If an unsymmetrical internal all ne is used, a mixture of regioisomers of dihydropyridones was obtained. ... 

Earlier, Kurahashi and Matsubara described regio- and enantioselective nickel-catalysed decarbonylative formal cycloadditions of phthalic anhydrides with allenes to give in a single step the corresponding chiral 5-lac-tones. The process represented an unprecedented insertion reaction of a carbon-carbon double bond into a carbon-oxygen bond. It was performed in the presence of a chiral nickel catalyst generated in situ from Ni(cod)2 and (5,5)-i-Pr-FOXAP in pyridine at reflux. The chiral 5-lactones were achieved in both moderate to good yields (64-73%) and with enantioselectivities of 59-81% ee, as shown in Scheme 4.16. Better yields (73-90%) and enantioselectivities... 

The catalytic cycle of the Ni-catalysed dimerization of ethylene to give 1-butene (65) is explained by the insertion of ethylene to the nickel hydride 62 twice to form the ethyl complex 63 and the butyl complex 64. The elimination of /1-hydrogen gives 1-butene (65), and regenerates the Ni—H species 62. The reaction is chemoselective. Curiously, no further insertion of ethylene to 64 occurs. 

In 2012, Murakami et al reported the asymmetric intramolecular alkene insertion reaction of 3-(2-styryl)cyclobutanones catalysed by an in situ generated chiral nickel complex bearing a BINOL-derived phosphoramidite ligand 15 (Scheme 10.22). The reaction provided a unique and straightforward access to... 

A study of this carbonylation reaction catalysed by tetracarbonylnickel in polar aprotic solvents, e.g. dimethyl sulphoxide or iVA-dimethylformamide, in the presence of calcium hydroxide reveals that the reaction can proceed at one atmosphere pressure of carbon monoxide and at 100 °C. The reaction probably involves oxidation-addition of aryl halide to the nickel followed by carbon monoxide insertion. Rates decrease in the order I > Br > Cl > F, Chloride ions and bromide ions enhance the reaction and this explains the autocatalytic behaviour observed as these ions are released from the aryl halide during reaction. ... 

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