Palladium-Catalyzed Isomerization of Methylenecyclopropanes in Acetic Acid

Palladium-Catalyzed Nucleophilic Reaction of Alkylidenecyclopropanes with β,γ-Unsaturated α-Ketoesters: Ligand-Controlled Divergent Synthesis

A palladium-catalyzed ligand-controlled selective 1,4-addition and cycloaddition reaction of β,γ-unsaturated α-ketoesters with alkylidenecyclopropanes (ACPs) has been developed. Using ACPs and β,γ-unsaturated α-ketoesters as starting materials, γ-dienyl-α-ketoesters and dihydro-2H-pyrans could be prepared selectively by modulating the ligand. A range of multisubstituted α-ketoesters and dihydro-2H-pyrans were obtained in moderate to excellent yields with excellent regioselectivities.

Iron-Catalyzed Ortho C-H Homoallylation of Aromatic Ketones with Methylenecyclopropanes

We report here a C-H homoallylation reaction of aromatic ketones with methylenecyclopropanes (MCPs) only using a catalytic amount of Fe(PMe₃)₄. A variety of aromatic ketones and MCPs are applicable to the reaction to form ortho-homoallylated aromatic ketones selectively via regioselective scission of the three-membered rings. The homoallylated products are amenable to further elaborations, providing functionalized 1,2-dihydronaphthalenes.

A cooperative zinc/catalytic indium system for the stereoselective sequential synthesis of (E)-1,3-dienes from carbonyl compounds

A novel cooperative system based on zinc/catalytic indium for the stereoselective synthesis of highly functionalized (E)-1,3-dienes from aldehydes and ketones has been developed.

NHC/Nickel(II)-Catalyzed [3+2] Cross-Dimerization of Unactivated Olefins and Methylenecyclopropanes

Cross-dimerization of a methylenecyclopropane (1) and an unactivated alkene (2) with typical hydroalkenylation reactivity was observed for the first time by using a [NHC-Ni(allyl)]BAr^F catalyst (NHC=N-heterocyclic carbene). Results show that the C-C cleavage of 1 did not involve a Ni⁰ oxidative addition, which was crucial in former systems. Thus the method reported here emerges as a complementary method for attaining highly chemo- and regioselective synthesis of methylenecyclopentanes (3) with broad scope. An efficient NHC/Ni^II -catalyzed rearrangement of 1 leads to the convergent synthesis of 3 in the presence of 2.

Copper/B2pin2-Catalyzed Difluoroalkylation of Methylenecyclopropanes with Bromodifluorinated Acetates and Acetamides: One-Pot Synthesis of CF2-Containing Dihydronaphthalene Derivatives

Novel copper/B₂pin₂-catalyzed difluoroalkylation of methylenecyclopropanes with bromodifluorinated acetates and acetamides via a tandem radical process involving ring-opening/intramolecular cyclization has been reported. This protocol is not only tolerated to a diverse range of substrates but also applicable to the synthesis of useful difluoromethylated compounds. Moreover, the reaction could be performed on a gram scale with a high yield, which opens up the possibility for practical applications.

Selectivity in metal-catalyzed carbon-carbon bond cleavage of alkylidenecyclopropanes

When more complex system leads to simpler reactivity profile; the ring-opening of strained three-membered rings such as methylene- and alkylidenecyclopropanes generally lead to several products. If one starts with more functionalized carbon skeletons, selective reactions are now observed and rationalization as well as synthetic applications are described in this concept article. This methodology could be used to the preparation of challenging structural motifs possessing quaternary carbon stereocenters in acyclic systems.