Highly Enantioselective Synthesis of Monofluoroalkenes by Rhodium-Catalyzed Asymmetric Arylation/Defluorination of Allyl Difluorides

Radical Decarboxylation-Initiated SH2' Reaction of β,β-Difluoroenol Sulfonates: Access to α,α-Difluoroketones

Reported herein is a novel radical decarboxylation-initiated SH2' reaction of β,β-difluoroenol sulfonates. This transformation is characterized by mild reaction conditions, a broad substrate scope, and late-stage modification of drug molecules, providing general and mechanistically distinct access to bioactive and synthetically versatile α,α-difluoroketones. Preliminary mechanistic studies demonstrate that this reaction proceeds through a succession of silver-mediated decarboxylative radical generation and radical-addition-induced β-elimination of the sulfonyl radical.

Palladium-catalyzed regio- and stereo-selective phosphination of cyclic biarylsulfonium salts to access atropoisomeric phosphines

A palladium-catalyzed regio- and stereo-selective phosphination of cyclic biarylsulfonium salts (racemic) with HPAr3Ar4 for straightforward synthesis of atropoisomeric phosphines (P,S-ligands) bearing a stereogenic axis or both a stereogenic axis and a P-stereogenic center is reported. The high reactivity and regio- and stereo-selectivity originate from the torsional strain release and palladium catalysis, and the construction of a P-stereogenic center is enabled by an efficient dynamic kinetic resolution. The high performance of the nascent P,S-ligands has been demonstrated in palladium-catalyzed asymmetric allylic substitutions, indicating the great potential of the present methodology.

Au(I)-Catalyzed Regioselective Hydrofluorination of Propargylamines Using Aqueous HF

Gold-catalyzed regioselective hydrofluorination of alkynes using aqueous HF has been achieved by employing an amide directing group. For both aryl- and alkyl-substituted propargylamines, the fluorination occurred at the site distal to the amino group.

Stereospecific Nickel-Catalyzed Cross-Electrophile Coupling Reaction of Alkyl Mesylates and Allylic Difluorides to Access Enantioenriched Vinyl Fluoride-Substituted Cyclopropanes

Cross-electrophile coupling reactions involving direct C-O bond activation of unactivated alkyl sulfonates or C-F bond activation of allylic gem-difluorides remain challenging. Herein, we report a nickel-catalyzed cross-electrophile coupling reaction between alkyl mesylates and allylic gem-difluorides to synthesize enantioenriched vinyl fluoride-substituted cyclopropane products. These complex products are interesting building blocks with applications in medicinal chemistry. Density functional theory (DFT) calculations demonstrate that there are two competing pathways for this reaction, both of which initiate by coordination of the electron-deficient olefin to the low-valent nickel catalyst. Subsequently, the reaction can proceed by oxidative addition of the C-F bond of the allylic gem-difluoride moiety or by directed polar oxidative addition of the alkyl mesylate C-O bond.

Chiral Diene Ligands in Asymmetric Catalysis

Asymmetric catalysis has emerged as a general and powerful approach for constructing chiral compounds in an enantioselective manner. Hence, developing novel chiral ligands and catalysts that can effectively induce asymmetry in reactions is crucial in modern chemical synthesis. Among such chiral ligands and catalysts, chiral dienes and their metal complexes have received increased attention, and a great progress has been made over the past two decades. This review provides comprehensive and critical information on the essential aspects of chiral diene ligands and their importance in asymmetric catalysis. The literature covered ranges from August 2003 (when the first effective chiral diene ligand for asymmetric catalysis was reported) to October 2021. This review is divided into two parts. In the first part, the chiral diene ligands are categorized according to their structures, and their preparation methods are summarized. In the second part, their applications in asymmetric transformations are presented according to the reaction types.

Rhodium(I)-Catalyzed Defluorinative Coupling of Boronic Acids with Monofluoroalkenes

We herein describe a highly selective Rh(I)-catalyzed defluorinative coupling of boronic acids with (E)-β-monofluoroacrylates. In contrast to previous methods, the trisubstituted (Z)-alkene products were obtained in excellent dr with an inversion of double bond geometry. Experimental and computational studies established that Rh(I)-facilitated β-F elimination is favored over competing β-H elimination and protodemetalation.

Chemo-, regio- and stereoselective synthesis of monofluoroalkenes via a tandem fluorination-desulfonation sequence

A widely applicable approach for the synthesis of Z-monofluoroalkenes from readily available alkyl triflones and NFSI has been reported. The reaction proceeded under mild conditions, affording mono-fluorinated alkenes in good to excellent yields with excellent chemo- regio- and stereoselectivity. The mechanism may involve electrophilic fluorination of triflones followed by the highly stereoselective concerted bimolecular elimination (E2) of CF3SO2H.

Synthesis of Rhodium Complexes with Chiral Diene Ligands via Diastereoselective Coordination and Their Application in the Asymmetric Insertion of Diazo Compounds into E-H Bonds

A new method for the synthesis of chiral diene rhodium catalysts is introduced. The readily available racemic tetrafluorobenzobarrelene complexes [(R₂ -TFB)RhCl]₂ were separated into two enantiomers via selective coordination of one of them with the auxiliary S-salicyl-oxazoline ligand. One of the resulting chiral complexes with an exceptionally bulky diene ligand [(R,R-iPr₂ -TFB)RhCl]₂ was an efficient catalyst for the asymmetric insertion of diazoesters into B-H and Si-H bonds giving the functionalized organoboranes and silanes with high yields (79-97 %) and enantiomeric purity (87-98 % ee). The stereoselectivity of separation via auxiliary ligand and that of the catalytic reaction was predicted by DFT calculations.

Catalytic asymmetric synthesis of monofluoroalkenes and gem-difluoroalkenes: advances and perspectives

The latest achievements in the catalytic asymmetric synthesis of both monofluoro- and gem-difluoroalkenes are discussed.