Reversible Carbon−Carbon Bond Formation between 1,3-Dienes and Aldehyde or Ketone on Nickel(0)

Catalytic Addition of Simple Alkenes to Carbonyl Compounds Using Group 10 Metals

Recent advances using nickel complexes in the activation of unactivated monosubstituted olefins for catalytic intermolecular carbon-carbon bond-forming reactions with carbonyl compounds, such as simple aldehydes, isocyanates, and conjugated aldehydes and ketones, are discussed. In these reactions, the olefins function as vinyl- and allylmetal equivalents, providing a new strategy for organic synthesis. Current limitations and the outlook for this new strategy are also discussed.

Diastereoselective construction of functionalized homoallylic alcohols by Ni-catalyzed diboron-promoted coupling of dienes and aldehydes

The nickel-catalyzed reaction of carbonyls and dienes was accomplished in a regio- and stereoselective fashion employing a stoichiometric amount of bis(pinacolato)diboron. This reductive coupling furnishes an allyl boronic ester as the reaction product, a compound which was readily converted to the derived allylic alcohol by oxidative workup.

Diastereoselective nickel-catalyzed reductive aldol cyclizations using diethylzinc as the stoichiometric reductant: scope and mechanistic insight

In the presence of diethylzinc as a stoichiometric reductant, Ni(acac) 2 functions as an efficient precatalyst for the reductive aldol cyclization of alpha,beta-unsaturated carbonyl compounds tethered to a ketone electrophile through an amide or an ester linkage. The reactions are tolerant of a wide range of substitution at both alpha,beta-unsaturated carbonyl and ketone components and proceed smoothly to furnish beta-hydroxylactams and beta-hydroxylactones with generally high diastereoselectivities. A series of experiments, including deuterium-labeling studies, was carried out in an attempt to gain some insight into the possible reaction mechanisms that might be operative.

Nickeladihydrofuran. Key intermediate for nickel-catalyzed reaction of alkyne and aldehyde

The formation of a nickeladihydrofuran by oxidative cyclization of an alkyne and an aldehyde with nickel(0) has been demonstrated; the transformation of the nickeladihydrofuran into an enone by decomposition, a lactone by carbonylation and an allylic alcohol by treatment with ZnMe(2) suggests that nickeladihydrofuran is an important key intermediate in a variety of catalytic reactions.

Nickel-catalyzed [2+2+2] cycloaddition of two alkynes and an imine

The reaction of N-benzenesulfonylbenzaldimine with Ni(cod)2 and PCy3 gave the corresponding η2-iminenickel complex quantitatively. Diphenylacetylene reacted with the η2-iminenickel complex to generate five-membered aza-nickelacycle. Insertion of second alkynes into the five-membered aza-nickelacycle led to the formation of the corresponding seven-membered aza-nickelacycles. Heating the solution of the seven-membered aza-nickelacycles induced the reductive elimination to give 1,2-dihydropyridine. In the presence of 10 mol % of Ni(cod)2 and PMetBu2 at 100 °C, the intermolecular [2+2+2] cycloaddition of N-benzenesulfonylbenzaldimine and 2-butyne occurred to give the expected 1,2-dihydropyridine in 87 % yield. In the presence of PCy3, the reaction also proceeded catalytically, however, PMetBu2 gave better results. Less bulky or less basic phosphine, PnBu3 or P(o-tol)3, was not efficient for the reaction. Although Ni(0)-NHC complex was a good catalyst for [2+2+2] cycloaddition of two alkynes and a ketone or an aldehyde, this reaction did not proceed in the presence of an NHC ligand, 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene.

Nickel catalyzed Grob fragmentation: ω-dienyl aldehydes synthesis

With a proper choice of phosphane ligands, a Ni(cod)2-phosphane catalyst promotes decarboxylative ring-opening reaction of a wide structural variety of cyclic carbonates to give omega-dienyl aldehydes in good yields.