Novel Synthesis of 2-Oxo-3-butynoates by Copper-Catalyzed Cross-Coupling Reaction of Terminal Alkynes and Monooxalyl Chloride

A general and efficient Cu(I)-catalyzed cross-coupling reaction of terminal alkynes and monooxalyl chloride for the synthesis of 2-oxo-3-butynoates and 2-oxo-3-butynoamides was developed. Readily available starting materials, the mild reaction conditions, wide functional group tolerance, and the obviation of stoichiometric organolithium or magnesium reagents combine to highlight this reaction

Rhodium-Catalyzed Cycloisomerization of 1,6-Enynes with an Intramolecular Halogen Shift: Reaction Scope and Mechanism

The rhodium(I)-species-catalyzed cycloisomerization reaction of a wide spectrum of 1,6-enynes with an unusual intramolecular halogen shift was investigated. This Rh-catalyzed enyne cyclization reaction represents a new process for the synthesis of stereodefined α-halomethylene-γ-butyrolactones, lactams, tetrahydrofurans, pyrrolidines, and cyclopentanes. Coordinatively unsaturated rhodium species ([Rh(COD)Cl]2 + dppb + AgSbF6) only catalyzes the reaction with enyne substrates bearing a Z-form double bond, while neutral rhodium species (RhCl(PPh3)3) could catalyze enyne substrates bearing a Z- or E-form double bond to form the desired products and has a wider substrate scopes. The mechanism of the reaction was studied by the employment of control experiments with different enyne isomers, and a π-allyl rhodium intermediate was suggested to explain the formation of the cyclic products with an intramolecular halogen shift

Synthesis of a Bulky and Electron-Rich Derivative of SEGPhos and Its Application in Ru-Catalyzed Enantioselective Hydrogenation of β-Ketoesters

The synthesis and resolution of a bulky and electron-rich derivative of SEGPhos and its application in Ru-catalyzed asymmetric hydrogenation reaction of β-ketoesters are reported. Up to 99.5% ee was achieved. Under solvent-free reaction conditions, acetoacetates could be reduced with good enantioselectivity and high efficiency; a TON of 20 000 was obtained within 3.5 h. The results obtained were comparable to those when SEGPhos was applied

Palladium-Catalyzed Tandem Cyclization/Suzuki Coupling of 1,6-Enynes: Reaction Scope and Mechanism

A palldium(0)-catalyzed tandem cyclization/Suzuki coupling reaction of various 1,6-enyne substrates was developed. This Pd-catalyzed enyne cyclization reaction represents a new process for the synthesis of stereodefined α-arylmethylene-γ-butyrolactones, lactams, multifunctional tetrahydrofurans, pyrrolidines, and cyclopentanes. The mechanism of the reaction was studied by the employment of different enyne isomers and boronic acids; a π-allyl palladium intermediate was suggested to explain the formation of the cyclic products. The stereochemistry of this reaction can be well explained by a chairlike transition state