Palladium-catalyzed dicyanative [4 + 2] cycloaddition using various ene−enynes was investigated. The key species in this process is a cyanoallene intermediate that is obtained by the cyanopalladation of conjugated enynes followed by 5-exo-cyclization. To achieve an efficient [4 + 2] cycloaddition reaction, both the smooth generation of this species and critical control of regioselectivity in the 6-endo-cyclization
Readily available propargyl alcohols were found to be useful substrates for the copper(I)-catalyzed synthesis of β,γ-unsaturated amides. Nucleophilic attack by the alcohol on the in situ generated ketenimine followed by base-catalyzed elimination and subsequent ring opening yields the desired products under mild conditions.
A direct and selective synthesis of α,β-unsaturated piperidones by a new palladium-catalyzed cascade carbonylation is described. In the presented protocol, easily available propargylic alcohols react with aliphatic amines to provide a broad variety of interesting heterocycles. Key to the success of this transformation is a remarkable catalytic cleavage of the present carbon–carbon triple bond by using
Gold/Brønsted Acid Relay Catalysis for Enantioselective Construction of Spirocyclic Diketones
作者:Deyun Qian、Junliang Zhang
DOI:10.1002/chem.201301208
日期:2013.5.27
opportunities: A redox‐, atom‐, and step‐economical asymmetric cascadereaction for the synthesis of chiral spirocyclic architectures with two contiguous stereocenters in high yields and excellent enantioselectivities by using a gold/chiral Brønstedacid relay catalysis system is described (see scheme). The results suggest that the chiral Brønstedacid rather than the chiral gold phosphate complex serves as