Enantioselective Organocatalytic Michael Addition to Unsaturated Indolyl Ketones

Asymmetric N-Alkylation of 1H-Indoles via Carbene Insertion Reaction

An intermolecular enantioselective N-alkylation reaction of 1H-indoles has been developed by cooperative rhodium and chiral phosphoric acid catalyzed N-H bond insertion reaction. N-Alkyl indoles with newly formed stereocenter adjacent to the indole nitrogen atom are produced in good yields (up to 95 %) with excellent enantioselectivities (up to >99 % ee). Importantly, both α-aryl and α-alkyl diazoacetates are tolerated, which is extremely rare in asymmetric X-H (X=N, O, S et al.) and C-H insertion reactions. With this method, only 0.1 mol % of rhodium catalyst and 2.5 mol % of chiral phosphoric acid are required to complete the conversion as well as achieve the high enantioselectivity. Computational studies reveal the cooperative relay of rhodium and chiral phosphoric acid, and the origin of the chemo and stereoselectivity.

Visible-light-induced synthesis of N-disulfanyl indoles, pyrroles or carbazoles via the construction of stable S-S-N bonds

A simple and efficient visible-light-induced approach for the formation of stable S-S-N bonds has been developed. Through these photocatalytic reactions, a series of N-disulfanyl indoles, pyrroles and carbazoles were afforded with good to excellent yields. Moreover, the gram-scale experiment has confirmed the practicability of this approach.

Rhodium-Catalyzed Asymmetric 1,4-Addition of α/β-(N-Indolyl) Acrylates

A rhodium-catalyzed asymmetric 1,4-addition of α/β-(N-indolyl) acrylates to access highly enantioenriched chiral N-alkylindoles promoted by chiral diene or sulfur-olefin ligands under mild reaction conditions has been developed, which provides an efficient and practical approach for constructing carbon stereocenters adjacent to the indole nitrogen. The reaction can be applied to various N-indolyl-substituted α,β-unstaturated esters and arylboron reagents, providing access to a wide range of α- and β-(N-indolyl) propionate derivatives in high yields with excellent enantioselectivities (≤99% ee).

Enantioselective Total Synthesis of [3]-Ladderanol through Late-Stage Organocatalytic Desymmetrization

Ladderane phospholipids, with their unusual ladder-like arrangement of concatenated cyclobutane rings, represent an architecturally unique class of natural products. However, despite their fascinating structure and other necessary impetus, only a few synthetic studies of these molecules have been reported so far. We have now devised a concise total synthesis of [3]-ladderanol, a component of natural ladderane phospholipids, using an organocatalytic enantioselective desymmetrizing formal C(sp² )-H alkylation. Our synthetic strategy rests on the late-stage introduction of chirality, thus allowing facile access to both enantiomers of [3]-ladderanol as well as an analogue. This is the first time a desymmetrization strategy is applied to the synthesis of [3]-ladderanol. The scope of this desymmetrizing C(sp² )-H alkylation of meso-cyclobutane-fused cyclohexenediones is also presented.

Multifunctional Catalysts in the Asymmetric Mannich Reaction of Malononitrile with N-Phosphinoylimines: Coactivation by Halogen Bonding versus Hydrogen Bonding

A multifunctional (noncovalent) catalyst containing halogen-bond donor, hydrogen-bond donor, and Lewis basic sites was developed and applied in an enantioselective Mannich reaction between malononitrile and diphenylphosphinoyl-protected aldimine affording products in high yields (up to 98%) and moderate to high enantiomeric purities (ee up to 89%). Typically, noncovalent catalysts rely on several weak interactions to activate the substrate, with one or two of these giving the most notable contribution to activation. In this instance, instead of the initially proposed coactivation by halogen bonding, it was revealed that hydrogen bonding plays a key role in determining the enantioselectivity.

Metal-free synthesis of β-aminoketones by the reductive hydroamination of ynones

This study describes a cascade method for the synthesis of β-aminoketones through the reductive hydroamination of alkynes under very mild metal-free conditions. It allows for the rapid conversion of ynones and amines into corresponding β-aminoketones with a broad substrate scope and diverse functionalities. This straightforward and easy-to-handle reaction process can be successfully applied for the synthesis of Proroxan and Propipocaine, offering a potential option for the synthesis of drug molecules with the β-aminoketone skeleton.

Recent progress in the chemistry of β-aminoketones

The current study highlighted the significance of β-aminoketones as privileged biologically active molecules, recent synthetic strategies, and synthetic applications.