The first iron-catalyzed enantioselective Si−H bond insertion reaction of α-diazoesters was developed. A new chiral spiro-bisoxazoline ligand has proven to be an optimal ligand for the asymmetric reaction to give versatile chiral αsilyl esters in good yields with high enantioselectivities. The mechanism and detailed stereochemical models for enantioselective induction were elucidated by DFT calculations, suggesting that the reaction proceeds via a concerted quintet transition state.
The first highly enantioselective iso-Pictet-Spengler reaction of C-2-linked o-aminobenzylindoles with trifluoromethyl ketones was developed using chiral spirocyclic phosphoric acids as organocatalysts, which afforded optically active benzazepinoindoles bearing trifluoromethylated quaternary stereocenters.
The Pd/C-catalyzed reactions, including reduction reactions and cross-coupling reactions, play an irreplaceable role in modern organic synthesis. Compared to the homogeneous palladium catalyst system, the heterogeneous Pd/C catalyst system offers an alternative protocol that has particular advantages and applications. Herein, a review on Pd/C-catalyzed reactions is presented. Both the advances in Pd/C-catalyzed methodologies and the application of Pd/C-catalysis in total synthesis are covered in this review.
With the vastly increasing applications of chiral phosphine-oxazoline (PHOX) hybrid ligands in various transition-metal-catalyzed reactions, novel PHOX ligands bearing innovative backbones are highly valuable and in great demand. This study describes the development of a new type of chiral PHOX ligands based on a hexamethyl-1,1'-spirobiindane scaffold and incorporating both a phosphine and an oxazoline moiety. The optimal ligand provided high yields and excellent enantioselectivities for the Ni-catalyzed asymmetric arylation of cyclic N-sulfonyl imines with arylboronic acids leading to chiral amines.
The organocatalytic asymmetric reactions of C2-unsubstituted racemic naphthyl-indoles with orthoalkynylnaphthols were employed to synthesize axially chiral styrenes connected to an axially chiral naphthyl-indole unit. Utilizing chiral phosphoric acid as the catalyst, these axially chiral styrenes were prepared in good yields (up to 96%) and excellent stereoselectivity (up to >99.9% ee, >20:1 dr, and >99:1 E/Z) in mild conditions. Moreover, further synthetic transformations were achieved with high yields and excellent stereocontrol.
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