Some cationic η3-propargylpalladium complexes were prepared upon treatment of the corresponding η1-propargyl- or η1-allenylbis(triphenylphosphine)palladium(II) chloride with Ag[BF4] or Na[BPh4]. The effectiveness of the latter reagent suggests that a η1-propargyl- or η1-allenyl(chloro)palladium complex equilibrates with a cationic η3-propargylpalladium complex with the liberation of a Cl− ligand. A
phosphane, which is employed as the palladium atom’s ligand, and the solvent have a remarkable effect on this reaction. We found that the optimum conditions for the reaction are those using a bidentate phosphane ligand (dppe) in a polar solvent (DMF). Compound 1a reacted smoothly with both aromatic (PhSH) and secondary thiols (CySH) in high yields. The reactions with thiols bearing functional groups (OH or
NHC–Gold(I) Complexes as Effective Catalysts for the Carboxylative Cyclization of Propargylamines with Carbon Dioxide
作者:Shun Hase、Yoshihito Kayaki、Takao Ikariya
DOI:10.1021/om400949m
日期:2013.10.14
NHC–gold(I) complexes promote carboxylative cyclization of a range of propargylic amines to afford (Z)-5-alkylidene-1,3-oxazolidin-2-ones in methanol under neutral and mild conditions. The highly active and robust catalyst permits CO2 utilization under a mixed gas atmosphere containing CO or H2. As a key intermediate, a new alkenylgold(I) complex was successfully identified from a stoichiometric reaction
Synthesis of 5-methylidenehexahydropyrrolo[l,2-a]imidazoles and 6-methylideneoctahydropyrrolo[l,2-a]pyrimidines by the reaction of 1-alkynyl-1-chlorocyclopropanes with lithium derivatives of 1,2- and 1,3-diaminoalkanes
作者:K. N. Shavrin、V. D. Gvozdev、O. M. Nefedov
DOI:10.1007/s11172-010-0261-6
日期:2010.7
A reaction of 1-alkynyl-1-chlorocyclopropanes with excess of lithiumderivative of 1,2-diaminoethane leads to 5-methylidenehexahydropyrrolo[l,2-a]imidazoles in 35–72% yields, whereas analogous reaction with lithiumderivative of 1,3-diaminopropane gives 6-methyl-ideneoctahydropyrrolo[l,2-a]pyrimidine in up to 50% yield. A mechanism of these unusual multi-step processes includes dehydrochlorination
HCl or AcCl, at the central carbon of the mu-eta(3)-allenyl/propargyl ligand to give the mu-eta(3)-vinylcarbenedipalladium complexes. Intramolecular reaction proceeded smoothly to give cyclization products quantitatively. Addition of a catalytic amount of a palladium(0) complex dramatically accelerated the carbon-carbonbondformation. The MO calculations on the mu-eta(3)-allenyl/propargyl complexes indicated