Nickel-Catalyzed Chemo- and Enantioselective Coupling between Cyclobutanones and Allenes: Rapid Synthesis of [3.2.2] Bicycles

Palladium-catalysed alkenyl and carbonylative C-C bond activation of cyclobutanones

A palladium catalysed C-C bond activation of cyclobutanones for the construction of alkenyl and carbonylated indanones has been developed. The in situ generated σ-alkylpalladium intermediate VIA C-C bond cleavage of cyclobutanone could be trapped with N-tosylhydrazones and carbon monoxide, respectively. The reactions were carried out under mild conditions with excellent functional group tolerance.

Enantioselective Desymmetrization of Cyclobutanones: A Speedway to Molecular Complexity

Cyclobutanones hold a privileged role in enantioselective desymmetrization because their inherent ring strain allows for a variety of unusual reactions to occur. Current strategies include α-functionalization, rearrangement, and C-C bond activation to directly convert cyclobutanones into a wide range of enantiomerically enriched compounds, including many biologically significant scaffolds. This Minireview provides an overview of state-of-the-art methods that generate complexity from prochiral cyclobutanones in a single operation.

Enantioselective Cross-Exchange between C-I and C-C σ Bonds

A palladium-catalyzed enantioselective intramolecular σ-bond cross-exchange between C-I and C-C bonds is realized, providing chiral indanones bearing an alkyl iodide group and an all-carbon quaternary stereocenter. Pd/TADDOL-derived phosphoramidite is found to be an efficient catalytic system for both C-C bond cleavage and alkyl iodide reductive elimination. In addition to aryl iodides, aryl bromides can also be used for this transformation in the presence of KI. Density-functional theory (DFT) calculation studies support the ring-opening of cyclobutanones occuring through an oxidative addition/reductive elimination process involving Pd^IV species.

Distal-Bond-Selective C-C Activation of Ring-Fused Cyclopentanones: An Efficient Access to Spiroindanones

A site-selective rhodium-catalyzed C-C activation of ring-fused cyclopentanones was achieved to afford efficient access to a range of spiroindanones. The use of bulky 2-amino-6-picoline as a cocatalyst is key to the excellent selectivity of this C-C bond cleavage in cyclopentanones.