Copper-catalyzed enantioselective Mukaiyama aldol reaction of silyl enol ethers with isatins

Water-enabling strategies for asymmetric catalysis

Water possesses unique advantages, including abundance, environmental friendliness and mild effects. Undoubtedly, it is an ideal solvent or reagent in chemical syntheses. Water also shows unique abilities in catalytic asymmetric synthesis. It can accelerate reaction rates, improve diastereo- or enantioselectivities, initiate reactions, diversify chemo, diastereo- or enantioselectivities through various effects (hydrophobic, hydrogen bonding, protonation). Several reviews have demonstrated the positive effects of water in asymmetric synthesis. In this review, we summarize water-enabling strategies in the last decade, and focus on advances which reveal how water affects a reaction.

Construction of a Chiral β-Fluoroamine by Asymmetric Mannich Reaction of 2-Fluoroindanone with Pyrazolinone Ketimines

The asymmetric Mannich reaction of 2-fluoroindanone with ketimine was developed under the catalysis of a kind of chiral copper complex, affording a chiral tetrahedral center containing fluorine. A series of β-fluoroamine derivatives can be obtained in excellent yields (73-94%) with high diastereoselectivities (>99:1 dr) and enantioselectivities (89-99%). The possible transition state was supported by density functional theory calculation.

Synthesis and Evaluation of N-Diaminophosphoryl Aminothioureas as Bifunctional Catalysts for Vinylogous Aldol Reactions of Isatins and 2(3H)-Furanones

The organocatalytic asymmetric direct vinylogous aldol reaction of N-methylisatins 1 and γ-butenolides 2 to provide 3-hydroxy-2-oxindole derivatives 3 was investigated. A series of N-diaminophosphoryl aminothiourea catalysts 4 was synthesized, and their utility for the stereoselective formation of 3 was examined.

Zn-Catalyzed enantioselective allylation and allenylation of isatins by virtue of a proline-derived chiral ligand

An asymmetric allylation and allenylation of isatins with facile organoboron reagents was developed under the catalysis of a Lewis acid. A series of optically pure 3-allyl-3-hydroxyoxindoles and 3-allenyl-3-hydroxyoxindoles can be obtained in excellent yields (up to 99% yield) and high enantioselectivities (up to 97% ee). The possible transition state was supported by DFT calculation and the corresponding mechanism was proposed. A gram scale experiment and further functionalization of these chiral 3-hydroxyoxindoles are established.

The Ligand Free Palladium(II)-Catalyzed Regioselective 1,2-Addition of Enol Silanes to Quinones to Access 4-Hydroxy-4-(2-oxo-2-arylethyl)cyclohexadien-1-ones and Synthetic Applications

In contrast to the conventional 1,4-addition process, regioselective 1,2-addition of silyl enol ethers to quinones can now be achieved via a palladium(II) enolate pathway that provides access to 4-hydroxy-4-(2-oxo-2-arylethyl)cyclohexa-2,5-dien-1-one derivatives. This quinone alkylation protocol proceeds under mild reaction conditions at ambient temperature under open air and does not require either an external ligand for the palladium or the use of a base. Additionally, the cyclohexadienone products have been exploited as synthetic precursors for the construction of fused heteroaryl systems.

Stereoselective Copper-Catalyzed Direct Aldol Reaction of β, γ-Unsaturated α-Ketoesters with Coumaran-3-Ones

An efficient direct aldol reaction between coumaran-3-ones and β, γ-unsaturated α-ketoesters by virtue of a chiral copper complex is developed. A series of coumaran-3-one derivatives containing chiral tertiary alcohol structures are obtained in excellent yields and stereoselectivities.

Radical cyclizations of enynes/dienes with alcohols in water using a green oxidant

A simple, eco-friendly, and efficient methodology for performing radical cyclizations of enynes/dienes with alcohols in water has been established.