An unprecedented catalytic asymmetric allylation of isatins and isatin-derived ketimines is reported enabled by agold and chiral organocatalyst cooperative catalysis strategy. This method offers expeditious access to chiral 2,5-disubsituted alkylideneoxazolines containing vicinal stereogenic centers, mainly in optically pure form, and which are otherwise impossible to access.Mechanistic evidence reveals the presence of an alkylgold intermediate,and an X-raycrystal structure of the allylgold species illuminates its unique stability and reactivity.A na symmetric formal hetero-ene reaction of this gold intermediate,i nvolving ad earomatization process,i s enabled with assistance of aq uinine-derived squaramide catalyst. This novel discovery extends the synthetic applications of gold complexes and the versatility of gold catalysis. Scheme 1. Gold-catalyzed transformations of N-propargylamides.
A gold‐catalyzed carbocyclization/C=N bond formation cascade reaction has been developed for the synthesis of polyfunctionalized 4‐iminonaphthalenones and indenes in good to high yields under mild reaction conditions. The reaction goes through 5/6‐endo‐dig diazo‐yne carbocyclization to form the endocyclic vinyl carbene species from corresponding alkyne‐tethered diazo compounds, followed by electrophilic addition/N−O bond cleavage/aromatization sequence with benzo[c]isoxazoles, which features a C=N bond formation process. In addition, the resulting products could be converted into multi‐substituted 2‐naphthol derivatives in high yields.
The catalytic asymmetric construction of allcarbon quaternary stereocenters has received tremendous interest over the past decades, and numerous efficient protocols have been disclosed based on the formation of one CÀ C bond between two assembling reactants. However, the use of asymmetric multicomponent reactions that build two CÀ C bonds on the same carbonic center with concomitant assembly of quaternary stereocenters is rare and remains challenging. Herein, we disclose an enantioselective threecomponent reaction of α-diazo ketones with alkenes and 1,3,5-triazines under dirhodium/chiral phosphoric acid cooperative catalysis, which leads to a practical and atom-economic synthesis of poly-functionalized chiral ketones that bear a α-quaternary stereocenter in generally good to high yields with excellent enantioselectivities. In comparison to the previous method for the construction of tertiary and quaternary stereocenters via carbene gem-difunctionalization reactions, this reaction features an unprecedented gem-dialkylation process via sequential installation of two CÀ C bonds on the carbene center in one reaction, providing an essential complement to the asymmetric construction of all-carbon quaternary stereocenters using common and readily available starting materials.
A dirhodium and chiral phosphoric acid co-catalyzed asymmetric three-component reaction of diazo compound with alcohol and seven-membered imine has been developed via Mannich-type interception of transient oxonium ylide. This reaction...
A Rh2(OAc)4 catalyzed intermolecular Aldol-type interception of phenolic oxonium ylides with isatins has been developed that provides an effective access to the 2,2-disubstituted dihydrobenzofuran derivatives containing 3-hydroxyoxindole in high yields...
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