Stereoselective Construction of Nitrile‐Substituted Cyclopropanes from 2‐Substituted Ethenesulfonyl Fluorides via Carbon‐Sulfur Bond Cleavage

Construction of benzimidazole- and indole-fused azabicyclo[3.1.0]hexanes bearing a cyano-containing quaternary center from vinylsulfonium salts through sequential [3 + 2]/[2 + 1] cyclization

A sequential [3 + 2]/[2 + 1] annulation reactions of benzimidazole- and indole-derived acrylonitriles with vinylsulfonium salts have been developed for the first time, and shown to provide in yields of 32 to 98% a series of azabicyclo[3.1.0]hexanes containing each a cyano-substituted tetrasubstituted carbon stereocenter with >20 : 1 dr. This method features simplicity, high efficiency and broad substrate scopes. Moreover, the synthetic utility was demonstrated with gram-scale reactions and further transformations of the products.

Chemoselective Reactions of Functionalized Sulfonyl Halides

Chemoselective transformations of functionalized sulfonyl fluorides and chlorides are surveyed comprehensively. It is shown that sulfonyl fluorides provide an excellent selectivity control in their reactions. Thus, numerous conditions are tolerated by the SO2 F group - from amide and ester formation to directed ortho-lithiation and transition-metal-catalyzed cross-couplings. Meanwhile, sulfur (VI) fluoride exchange (SuFEx) is also compatible with numerous functional groups, thus confirming its title of "another click reaction". On the contrary, with a few exceptions, most transformations of functionalized sulfonyl chlorides typically occur at the SO2 Cl moiety.

Enantioselective Addition of Dialkyl Malonates to β-Arylethenesulfonyl Fluorides under High-Pressure Conditions

Application of high-pressure conditions enables enantioselective Michael-type addition of dialkyl malonates to β-arylethenesulfonyl fluorides. The reaction is efficiently catalyzed with 5 mol % of tertiary amino-thiourea at 9 kbar. Chiral alkanesulfonyl fluorides are formed in yields of up to 96% and enantioselectivities of up to 92%. Functionalization of the adducts via sulfur fluoride exchange (SuFEx) reaction and desulfonylative cyclization is demonstrated.

Alkyl Sulfonyl Fluorides Incorporating Geminal Dithioesters as SuFEx Click Hubs via Water-Accelerated Organosuperbase Catalysis

Sulfur(VI) fluoride exchange (SuFEx) is recognized as another emerging tool for click chemistry. The preparation of the functionalized alkyl sulfonyl fluorides as key SuFEx hubs via C(sp³)-C(sp³) bond formation is exceptionally challenging. We report herein a new efficient method for accessing alkyl sulfonyl fluorides incorporating γ-geminal dithioester via phosphazene catalysis. The aqueous, neutral organosuperbase catalytic system amplifies the reactivity by taking advantage of the hydrophobic amplification. SuFEx-active products are applied to the click connection of bioactive molecules. Density functional theory studies show that the selective outcome of the product is guided by an ion-pair organosuperbase catalyst assembly that is potentially stabilized by a hydrogen-bonding interaction between the catalyst and the DTM in the C(sp³)-C(sp³) bond-forming transition structure.

Regioselective conjugate addition of isoxazol-5-ones to ethenesulfonyl fluoride

The highly regioselective conjugate addition of isoxazol-5-ones to ethenesulfonyl fluoride (ESF) has been developed. In the presence of different bases, N2-alkylated and C4-alkylated isoxazol-5-ones with a sulfonyl fluoride group were obtained separately with good to excellent yields. Further transformations with amines and phenol gave sulfonamides and sulfonates. The intriguing combination of isoxazol-5-ones and the sulfonyl fluoride group produces valuable products for drug discovery.

A cascade reaction for regioselective construction of pyrazole-containing aliphatic sulfonyl fluorides

A copper-catalyzed cascade reaction of α-diazocarbonyl compounds with ethenesulfonyl fluoride (ESF) is developed, affording a variety of highly functionalized pyrazolyl aliphatic sulfonyl fluorides in good to excellent yields (66-98%). This transformation features broad substrates, exclusive regioselectivity, high atom economy and operational simplicity, thus providing a straightforward method for the direct construction of pyrazole-containing aliphatic sulfonyl fluorides, which will provide great applicable value in medicinal chemistry and other related disciplines.

A general approach to nitrile- and sulfonyl fluoride-substituted cyclopropanes

Both cis and trans relative configurations of functionalized cyano cyclopropane bearing sulfonyl fluoride moiety were accessed by Corey-Chaykovsky cyclopropanation reactions. This protocol used mild conditions, and obtained good yields with excellent functional group compatibility. Further application of this class of compounds in SuFEx reactions and cyano reductions were also successfully achieved in good yields.

Enantioselective Addition of Azlactones to Ethylene Sulfonyl Fluoride via Dual Catalysis

Enantioselective conjugate addition of azlactones to ethylene sulfonyl fluoride has been achieved via the cooperative catalysis with (DHQD)₂PHAL and a hydrogen-bond donor (HBD). This approach furnishes a facile access to a range of structurally diverse azlactone sulfonyl fluoride derivatives with good to excellent yields and enantioselectivities. The combination of azlactone and sulfonyl fluoride group produces valuable unnatural α-quaternary amino acid derivatives for the drug discovery.

Highly Enantioselective Addition of N-2,2,2-Trifluoroethylisatin Ketimines to Ethylene Sulfonyl Fluoride

An enantioselective Michael addition between N-2,2,2-trifluoroethylisatin ketimines and ethylene sulfonyl fluoride has been disclosed. This method provides a facile strategy to access a range of structurally diverse isatin-derived α-(trifluoromethyl)imine derivatives with excellent yields and enantioselectivities. The intriguing combination of α-(trifluoromethyl)amine and sulfonyl fluoride groups leads to the valuable candidates for the drug discovery.

A novel three-component reaction for constructing indolizine-containing aliphatic sulfonyl fluorides

A copper-catalyzed three-component reaction for transforming quinolines, isoquinolines and pyridines to a class of indolizine-containing alkyl sulfonyl fluorides was developed.

SO2F2-Mediated Epoxidation of Olefins with Hydrogen Peroxide

An inexpensive, mild, and highly efficient epoxidation protocol has been developed involving bubbling SO₂F₂ gas into a solution of olefin, 30% aqueous hydrogen peroxide, and 4 N aqueous potassium carbonate in 1,4-dioxane at room temperature for 1 h with the formation of the corresponding epoxides in good to excellent yields. The novel SO₂F₂/H₂O₂/K₂CO₃ epoxidizing system is suitable to a variety of olefinic substrates including electron-rich and electron-deficient ones.