Copper-Catalyzed Highly Enantioselective Difluoroalkylation of Secondary Propargyl Sulfonates with Difluoroenoxysilanes

Catalytic AgF-Initiated Intramolecular 1,3-Sulfonyl Migration of gem-Difluorovinyl Sulfonates to α,α-Difluoro-β-ketosulfones

A 1,3-sulfonyl migration of difluorovinyl sulfonates initiated by a catalytic amount of silver fluoride is presented. α,α-Difluoro-β-ketosulfones were successfully prepared in excellent yields. This method features high chemoselectivity, good functional group tolerance, high atom economy, and mild, environmentally benign reaction conditions. Furthermore, mechanistic experiments indicate that this migration proceeds in an intermolecular pathway and the corresponding sulfinates are possible intermediates.

Regioselective Markovnikov hydrodifluoroalkylation of alkenes using difluoroenoxysilanes

Alkene hydrodifluoroalkylation is a fruitful strategy for synthesizing difluoromethylated compounds that are interesting for developing new medicinal agents, agrochemicals, and advanced materials. Whereas the anti-Markovnikov hydrodifluoroalkylation to linear-type products is developed, employing radical-based processes, the Markovnikov synthesis of branched adducts remains unexplored. Herein, we describe acid-catalyzed processes involving carbocation intermediates as a promising strategy to secure the Markovnikov regioselectivity. Accordingly, the Markovnikov hydrodifluoroalkylation of mono-, di-, tri-, and tetrasubstituted alkenes using difluoroenoxysilanes, catalyzed by Mg(ClO4)2·6H2O, is achieved. This allows the diversity-oriented synthesis of α,α-difluoroketones with a quaternary or tertiary carbon at the β-position that are otherwise difficult to access. The method is applied to the modification of natural products and drug derivatives. The resulting α,α-difluorinated ketones could be converted to the corresponding α,α-difluorinated esters or alcohols, or organofluorine compounds featuring a CF2H or CF2CF2Ph moiety. Mechanistic studies support that Mg(ClO4)2·6H2O functions as a hidden Brønsted acid catalyst.

γ-Difluoroalkylation: Synthesis of γ-Difluoroalkyl-α,β-Unsaturated Esters via Photoredox NHC-Catalyzed Radical Reaction

By the cooperative photoredox and N-heterocyclic carbene catalysis, the γ-difluoroalkylation of γ-preoxidized enals was developed for the synthesis of γ-difluoroalkyl-α,β-unsaturated esters with all-carbon quaternary centers. This method provides efficient catalytic C(sp³)-CF₂R bond formation at the γ-position of carbonyl compounds for the first time.

Decarboxylative and Deaminative Alkylation of Difluoroenoxysilanes via Photoredox Catalysis: A General Method for Site-Selective Synthesis of Difluoroalkylated Alkanes

A general method for site-selective difluoroalkylation of alkyl carboxylic redox esters with difluoroenoxysilanes through photoredox-catalyzed decarboxylative reaction has been developed. The reaction can also be extended to aliphatic amine derived pyridinium salts. This method has the advantages of high efficiency, mild reaction conditions, and broad substrate scope, including primary, secondary, and sterically hindered tertiaryl alkyl substrates, providing a general and practical route for applications in organic synthesis and pharmaceutical studies.

Catalytic Asymmetric [3 + 2] Annulation via Indolyl Copper-Allenylidene Intermediates: Diastereo- and Enantioselective Assembly of Pyrrolo[1,2-a]indoles

A catalytic asymmetric decarboxylative [3 + 2] annulation via indolyl copper-allenylidene amphiphilic intermediates has been developed. This protocol offers a straightforward method for the synthesis of biologically important pyrrolo[1,2-a]indoles bearing contiguous quaternary and tertiary stereogenic centers with excellent diastereo- and enantioselectivities (up to >20:1 dr and >99% ee). In addition, the diversity-oriented synthesis of pyrrolo[1,2-a]indoles was achieved via versatile transformations of the alkyne-containing cycloadducts.

Regio- and Enantioselective Bromocyclization of Difluoroalkenes as a Strategy to Access Tetrasubstituted Difluoromethylene-Containing Stereocenters

Difluoromethylene-containing compounds have attracted substantial research interest over the past decades for their ability to mimic biological functions of traditional functional groups while providing a wide variety of pharmacological benefits bestowed by the C-F bond. We report a novel strategy to access RCF2Br-containing heterocycles by regio- and enantioselective bromocyclization of difluoroalkenes enabled by chiral anion phase-transfer catalysis. The utility of this methodology was highlighted through a synthesis of an analogue of efavirenz, a drug used for treating HIV. Additionally, the synthetic versatility of the CF2Br intermediates was showcased through functionalization to a variety of enantioenriched α,α-difluoromethylene-containing products.

Highly enantioselective copper-catalyzed propargylic amination to access N-tethered 1,6-enynes

A highly enantioselective copper-catalyzed propargylic amination has been developed with a new chiral N,N,P ligand, providing a series of N-tethered 1,6-enynes in good to excellent yields with excellent enantioselectivities.

Visible light promoted deaminative difluoroalkylation of aliphatic amines with difluoroenoxysilanes

A visible light promoted deaminative strategy for the difluoroalkylation reaction utilizing pyridinium-activated aliphatic primary amines and difluoroenoxysilane as substrates has been developed.

Photoredox/palladium co-catalyzed propargylic benzylation with internal propargylic carbonates

The developed photo/palladium dual catalytic system provided a novel route to internal propargylic benzylation products. A radical coupling mechanism between the propargylic radical and benzyl radical was proposed.

Photoredox-catalyzed sulfonylation of difluoroenoxysilanes with the insertion of sulfur dioxide

A photoredox-catalyzed three-component reaction of aryldiazonium tetrafluoroborates with sodium metabisulfite and 2,2-difluoro enol silyl ethers is described, providing α,α-difluoro-β-ketosulfones in moderate to good yields under mild conditions.

Catalytic selective mono- and difluoroalkylation using fluorinated silyl enol ethers

This feature article highlights our recent achievements in catalytic selective mono- and difluoroalkylation using fluorinated silyl enol ethers (FSEEs).