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Asymmetric Friedel–Crafts conjugate addition reactions that generate an α-chiral center are challenging because the configuration-determining step is a proton-transfer reaction of a highly active e...

Catalytic asymmetric reactions in which water is a substrate are rare. Enantioselective transition-metal-catalyzed insertion of carbenes into the O-H bond of water can be used to incorporate water into the stereogenic center, but the reported chiral catalysts give good results only when α-aryl-α-diazoesters are used as the carbene precursors. Herein we report the first highly enantioselective O-H bond insertion reactions between water and α-alkyl- and α-alkenyl-α-diazoesters as carbene precursors, with catalysis by a combination of achiral dirhodium complexes and chiral phosphoric acids or chiral phosphoramides. Participation of the phosphoric acids or phosphoramides in the carbene transfer reaction markedly suppressed competing side reactions, such as β-H migration, carbene dimerization, and olefin isomerization, and thus ensured good yields of the desired products. Fine-tuning of the ester moiety facilitated enantiocontrol of the proton transfer reactions of the enol intermediates and resulted in excellent enantioselectivity. This protocol represents an efficient new method for preparation of multifunctionalized chiral α-alkyl and α-alkenyl hydroxyl esters, which readily undergo various transformations and can thus be used for the synthesis of bioactive compounds. Mechanistic studies revealed that the phosphoric acids and phosphoramides promoted highly enantioselective [1,2]- and [1,3]-proton transfer reactions of the enol intermediates. Maximization of molecular orbital overlap in the transition states of the proton transfer reactions was the original driving force to involve the proton shuttle catalysts in this process.

The transition-metal-catalyzed reaction of diazo compounds with arenes or heteroarenes is an efficient and straightforward approach to functionalize aromatic compounds. This digest summarizes recent progresses on transition-metal-catalyzed asymmetric reactions of diazo compounds with electron-rich (hetero-) arenes, including C–H functionalization, cascade reaction, cyclopropanation, cycloaddition, Buchner reaction and intramolecular dearomatization.

A highly efficient asymmetric Michael addition of thiols to exocyclic enones was achieved by using chiral spiro phosphoramide catalysts. The precisely chiral control in the protonation of the enol intermediate ensured high enantioselectivity. The reaction features high activity (yields up to 99%, turnover numbers up to 8400) and high enantioselectivity (up to 97% ee) with a broad substrate scope, and it has the potential for wide application in the synthesis of chiral sulfides.

An iridium complex with a newly prepared chiral spiro amino-phosphine ligand efficiently catalyzed the hydrogenation of both β-aryl-β-methyl-nitroalkenes and β-alkyl-β-methyl-nitroalkenes to the corresponding saturated nitroalkanes, which represents the first report of a chiral catalyst that exhibits high enantioselectivity for the challenging hydrogenation of β,β-dialkyl-nitroalkenes.

We report the first intramolecular enantioselective cyclopropanation of indoles, which was accomplished in good to high yield (up to 94%) with excellent enantioselectivity (up to >99.9% ee) by using copper or iron complexes of chiral spiro bisoxazolines as catalysts. This reaction is a straightforward, efficient method for constructing polycyclic compounds with an all-carbon quaternary stereogenic center at the 3-position of the indole skeleton, a core structure shared by numerous natural products and bioactive compounds.

A protocol for the highly efficient iridium-catalyzed asymmetric hydrogenation of racemic α-substituted lactones via dynamic kinetic resolution is described., We report a protocol for the highly efficient iridium-catalyzed asymmetric hydrogenation of racemic α-substituted lactones via dynamic kinetic resolution. Using Ir-SpiroPAP (R)-1d as a catalyst, a wide range of chiral diols were prepared in a high yield (80–95%) with a high enantioselectivity (up to 95% ee) under mild reaction conditions. This protocol was used for enantioselective syntheses of (–)-preclamol and a chiral 2,5-disubstituted tetrahydropyran.

An iridium complex with a newly prepared chiral spiro amino-phosphine ligand efficiently catalyzed the hydrogenation of both β-aryl-β-methyl-nitroalkenes and β-alkyl-β-methyl-nitroalkenes to the corresponding saturated nitroalkanes, which represents the first report of a chiral catalyst that exhibits high enantioselectivity for the challenging hydrogenation of β,β-dialkyl-nitroalkenes.