Recent advance in synthetic applications of difluoromethyl phenyl sulfone and its derivatives

Photoinduced Copper-Mediated Difluoroalkylation of Arylsulfonium Salts with XCF2COR

Photoredox fluoroalkylation has emerged as a powerful method and have unlocked new possibilities in organic chemistry. In this work, the green-light-induced copper-mediated difluoroalkylation of arylsulfonium salts with different XCF2COR reagents is described. The reaction proceeded smoothly at ambient temperature under mild conditions and allowed the formation of a variety of difluoroalkylated arenes in good yields. The photocatalyst, visible-light, and Cu(I) salt played a synergetic role in the reduction of arylsulfonium salt and XCF2COR to the respective radical intermediates. This metallophotoredox protocol was applicable to the late-stage difluoroalkylation of multifunctionalized bioactive molecules, offering opportunities to the discovery of new medicinal agents. The transformation showed advantages of mildness, simple operation, good functional group tolerance, a wide range of substrates, and excellent regioselectivity, which provided an interesting alternative to other difluoroalkylation reactions in terms of structural diversity, selectivity, and availability by the application of arylsulfonium platforms.

Radical photochemical difluorosulfoximination of alkenes and propellanes

Herein, we report a metal-free divergent visible-light driven method for the synthesis of fluorinated sulfoximines. Both olefins and propellanes efficiently undergo difluorosulfoximination with yields up to 77% (65 examples). The process is general and robust and tolerates diverse functional groups, including esters, ethers, ketones, silyl groups, silyl ethers or boronic esters. The functionalization of diverse bioactive ingredients (8 examples) and various product manipulations demonstrate the synthetic usefulness of the developed synthetic platform. Finally, we rationalized the divergent reaction mechanism by performing Stern-Volmer quenching and EPR experiments that revealed the key activity of a difluoroalkyl sulfoximine radical.

New synthetic approaches for the construction of difluoromethylated architectures

Fluorinated compounds play a vital role in the fields of agrochemicals, pharmaceuticals, and materials science because of their unique lipophilicity, permeability, and metabolic stability. Among all such appealing fluorine-containing functional groups, the difluoromethyl group has attracted considerable attention owing to its outstanding chemical and physical properties. It has been used as a lipophilic hydrogen bond donor and a bioisostere of thiol, hydroxy, or amino groups. The excellent properties of the CF2H group have motivated many chemists to develop effective strategies for the selective incorporation of the CF2H group into target molecules. Over the past decades, a variety of efficient, atom-economical, and facile methods have been discovered for the difluoromethylation of organic substrates. This review summarizes the developments in different types of difluoromethylations, which could be classified into the following categories: radical difluoromethylation, transition metal-catalyzed difluoromethylation, and nucleophilic and electrophilic difluoromethylation.

Quantifying the ability of the CF2H group as a hydrogen bond donor

The CF2H group can act as a hydrogen bond donor, serving as a potential surrogate for OH or SH groups but with a weaker hydrogen bond donation ability. Here, we describe a series of CF2H group-containing moieties that facilitate hydrogen bond interactions. We survey hydrogen bond donation ability using several established methods, including 1H NMR-based hydrogen bond acidity determination, UV-vis spectroscopy titration with Reichardt's dye, and 1H NMR titration using tri-n-butylphosphine oxide as a hydrogen bond acceptor. Our experiments reveal that the direct attachment of the CF2H group to cationic aromatic systems significantly enhances its hydrogen bond donation ability, a result consistent with theoretical calculations. We anticipate that this chemistry will be valuable for designing functional molecules for chemical biology and medicinal chemistry applications.

Catalytic Asymmetric Difluoroalkylation Using In Situ Generated Difluoroenol Species as the Privileged Synthon

A robust and practical difluoroalkylation synthon, α,α-difluoroenol species, which generated in situ from trifluoromethyl diazo compounds and water in the presence of dirhodium complex, is disclosed. As compared to the presynthesized difluoroenoxysilane and in situ formed difluoroenolate under basic conditions, this difluoroenol intermediate displayed versatile reactivity, resulting in dramatically improved enantioselectivity under mild conditions. As demonstrated in catalytic asymmetric aldol reaction and Mannich reactions with ketones or imines in the presence of chiral organocatalysts, quinine-derived urea, and chiral phosphoric acid (CPA), respectively, this relay catalysis strategy provides an effective platform for applying asymmetric fluorination chemistry. Moreover, this method features a novel 1,2-difunctionalization process via installation of a carbonyl motif and an alkyl group on two vicinal carbons, which is a complementary protocol to the metal carbene gem-difunctionalization reaction.

Difluoromethylated Difunctionalization of Alkenes under Visible Light

Difluoromethylated compounds usually act as bioisosteres for alcohol functional groups and show unique physicochemical and biological properties. The cyano-difluoromethylation of alkenes using 5-((difluoromethyl)sulfonyl)-1-phenyl-1H-tetrazole as a CF2H radical difluoromethyl precursor was developed to afford nitriles including a CF2H group. A low-cost, stable, easily handled 5-((difluoromethyl)sulfonyl)-1-methyl-1H-tetrazole (DFSMT) was synthesized and applied as the radical CF2H reagent. Using DFSMT as the radical CF2H precursor, the oxyl-difluoromethylation of alkenes was developed to obtain difluoromethylated ether products. All of the reactions showed good functional group tolerability. Initial mechanistic experiments indicated that the CF2H radical was involved as the key active intermediate.

Divergent Generation of the Difluoroalkyl Radical and Difluorocarbene via Selective Cleavage of C-S Bonds of the Sulfox-CF2SO2Ph Reagent

A new difluoroalkylation reagent Sulfox-CF2SO2Ph bearing both sulfoximine and sulfone moieties was prepared from commercially available SulfoxFluor and PhSO2CF2H. On one hand, the Sulfox-CF2SO2Ph reagent could act as a (phenylsulfonyl)difluoromethyl radical source under photoredox catalysis, in which the arylsulfoximidoyl group is selectively removed. On the other hand, under basic conditions, Sulfox-CF2SO2Ph could serve as a difluorocarbene precursor for S- and O-difluoromethylations with S- and O-nucleophiles, respectively, in which the phenylsulfonyl group in Sulfox-CF2SO2Ph is selectively removed (followed by α-elimination of the arylsulfoximidoyl group).

Manganese/Cobalt Bimetallic Relay Catalysis for Divergent Dehydrogenative Difluoroalkylation of Alkenes

The involvement of manganese radical for halogen atom transfer (XAT) reactions has been esteemed as one reliable method but encountered with limited catalytic models. In this paper, a novel bimetallic relay catalysis of Mn2 (CO)10 and cobaloxime has been developed for divergent dehydrogenative difluoroalkylation of alkenes using commercially available difluoroalkyl bromides. A wide range of structurally diverse terminal, cyclic and internal alkenes as well as tetrasubstituted alkenes are found to be good coupling partners to deliver difluoroalkylated allylic products and difluoromethylated cyclic products, accompanied with the production of H2 as the by-product. This bimetallic relay strategy features broad substrate scope, mild reaction conditions and excellent functional group compatibility. Its success represents an important step-forward to expedite the construction of a rich library of difluoroalkylated products.

C3-Selective Trifluoromethylthiolation and Difluoromethylthiolation of Pyridines and Pyridine Drugs via Dihydropyridine Intermediates

Herein, we report a method for unprecedented C3-selective C-H tri- and difluoromethylthiolation of pyridines. The method relies on borane-catalyzed pyridine hydroboration for generation of nucleophilic dihydropyridines; these intermediates react with trifluoromethylthio and difluoromethylthio electrophiles to form functionalized dihydropyridines, which then undergo oxidative aromatization. The method can be used for late-stage functionalization of pyridine drugs for the generation of new drug candidates.

Difluoromethylation of Heterocycles via a Radical Process

Difluoromethylation is of prime importance for its applicability in functionalizing diverse fluorine-containing heterocycles, which are core moieties of various biologically and pharmacologically active ingredients. Due to their significant biological and...

Chemo- and regio-divergent access to fluorinated 1-alkyl and 1-acyl triazenes from alkynyl triazenes

The 1,1,2,2-tetrafluoroethylene unit is a prevalent pattern in bioactive molecules and functional materials. Despite being in principle a straightforward strategy to access this motif, the direct tetrafluorination of alkynes involves...

C-H Electrophilic (phenylsulfonyl)difluoromethylation of (hetero)arenes with a newly designed reagent

The synthesis of an original electrophilic difluoromethylating reagent was successfully achieved upon a straightforward protocol (3 steps). Like a Swiss army knife, this bench-stable reagent allowed the functionalization of various classes of compounds under mild and transition metal-free conditions. Hence, an efficient and operationally simple tool for the construction of C(sp2)-, C(sp3)- and S-CF2SO2Ph bonds was provided, expanding the chemical space of PhSO2CF2-containing molecules. Late-stage functionalization of bioactive molecules and the synthesis of PhSO2CF2- and HCF2-analogs of Lidocaine were also successfully achieved.