Nickel-Catalyzed Intermolecular Alkyne Insertion into Cyclobutanones

Abstract

Cyclobutanones reacted with alkynes in the presence of nickel(0) catalysts to produce cyclohexenones. Oxidative cyclization of the carbonyl group of the cyclobutanone and the alkyne with the nickel(0) was followed by beta-carbon elimination from the resulting oxanickelacyclopentene and subsequent reductive elimination. This reaction achieves a formal alkyne insertion between the carbonyl carbon and the alpha-carbon, providing a six-membered carbocyclic skeleton.

Eight-Membered Ring Construction by [4 + 2 + 2] Annulation Involving β-Carbon Elimination

“…4 This result demonstrated the synthetic potential of cyclobutanones as a C4 unit in a ring-expansion process involving -carbon elimination. We next envisaged that this protocol could be extended even further to a three-component annulation reaction to construct medium-sized carbocycles.…”

Transition metals in organic synthesis: Highlights for the year 2005

“…Nickel catalyzed cycloadditions of cyclobutanones with alkynes forming cyclohexenones (Eq. (246)) [1310]. Rhodium catalyzed [5 + 2] and [5 + 2 + 1]cycloadditions of allenes with alkenylcyclopropanes (Eqs.…”

Transition Metal-Catalyzed Reactions Using N-Heterocyclic Carbene Ligands (Besides Pd- and Ru-Catalyzed Reactions)

“…12) [34]. While phosphine ligands were generally employed to facilitate the reaction, the authors also demonstrated that IPr was an effective ligand.…”

“…Metal/carbene complexes (30)(31)(32)(33)(34) have also proved fruitful in the hydrosilylation of alkynes, olefins, enones, and ketones. Lappert and Maskell showed that ketones and alkynes could be reduced to silyl ethers and vinylsilanes, respectively, using complexes 30 and 31 (Eqs.…”