Ethensulfonylfluorid: der beste je entdeckte Michael-Akzeptor?

Accelerated and Concerted Aza-Michael Addition and SuFEx Reaction in Microdroplets in Unitary and High-Throughput Formats

The sulfur fluoride exchange (SuFEx) reaction is significant in drug discovery, materials science, and chemical biology. Conventionally, it involves installation of SO₂ F followed by fluoride exchange by a catalyst. We report catalyst-free Aza-Michael addition to install SO₂ F and then SuFEx reaction with amines, both occurring in concert, in microdroplets under ambient conditions. The microdroplet reaction is accelerated by a factor of ∼10⁴ relative to the corresponding bulk reaction. We suggest that the superacidic microdroplet surface assists SuFEx reaction by protonating fluorine to create a good leaving group. The reaction scope was established by performing individual reactions in microdroplets of 18 amines in four solvents and confirmed using high-throughput desorption electrospray ionization experiments. The study demonstrates the value of microdroplet-assisted accelerated reactions in combination with high-throughput experimentation for characterization of reaction scope.

β-Aminosulfonyl Fluorides via Water-Accelerated N-Heterocyclic Carbene Catalysis

Herein, a water-accelerated, N-heterocyclic carbene (NHC)-catalyzed aza-Michael addition reaction was reported to access β-aminosulfonyl fluorides, which are key hubs of the sulfur(VI) fluoride exchange (SuFEx) reaction. As a crucial reaction medium, water considerably enhanced the reaction rate with excellent chemo- and site-selectivity (up to >99 : 1) compared to conventional solvents. In addition, the late-stage ligation of bioactive molecules with the aliphatic β-amino SuFEx hub was demonstrated. Mechanistic studies on experimental, analytical, and computational approaches support noncovalent activation over NHC catalysis "on-water".

Hydrophobic Amplification Enabled High-Turnover Phosphazene Superbase Catalysis

β-Sulfido sulfonyl fluoride and its derivatives have been gaining attention recently in the fields of medicinal chemistry and material science. The conventional method for the synthesis of functionalized alkyl sulfonyl fluorides requires several chemical transformations. Therefore, a direct establishment of such chemical structures remains challenging, and an efficient catalytic approach is highly desired. Herein a significant "on-water" hydrophobic amplification was achieved, enabling a high-turnover catalytic thia-Michael addition to produce unprecedented β-arylated-β-sulfido sulfonyl fluorides. Amounts as low as 100 ppm (0.01 mol %) of the phosphazene superbase were sufficient to successfully catalyze the reaction with excellent chemo-/site-selectivity and with optimal functional group tolerance. Several β-arylated ethene sulfonyl fluorides were converted into thia-Michael adducts up to >99 % yields. The mild conditions, high turnover, neutral pH, and scalability of the sustainable catalytic process benefit the preparation of potential pharmaceuticals (e. g., polyisoprenylated methylated protein methyl esterase inhibitors) and organic materials (e. g., electrolyte additives).

Utilizing Carbonyl Coordination of Native Amides for Palladium-Catalyzed C(sp3 )-H Olefination

PdII -catalyzed C(sp3 )-H olefination of weakly coordinating native amides is reported. Three major drawbacks of previous C(sp3 )-H olefination protocols, 1) in situ cyclization of products, 2) incompatibility with α-H-containing substrates, and 3) installation of exogenous directing groups, are addressed by harnessing the carbonyl coordination ability of amides to direct C(sp3 )-H activation. The method enables direct C(sp3 )-H functionalization of a wide range of native amide substrates, including secondary, tertiary, and cyclic amides, for the first time. The utility of this process is demonstrated by diverse transformations of the olefination products.

SuFEx-Based Polysulfonate Formation from Ethenesulfonyl Fluoride-Amine Adducts

The SuFEx-based polycondensation between bisalkylsulfonyl fluorides (AA monomers) and bisphenol bis(t-butyldimethylsilyl) ethers (BB monomers) using [Ph₃ P=N-PPh₃ ]⁺ [HF₂ ]^- as the catalyst is described. The AA monomers were prepared via the highly reliable Michael addition of ethenesulfonyl fluoride and amines/anilines while the BB monomers were obtained from silylation of bisphenols by t-butyldimethylsilyl chloride. With these reactions, a remarkable diversity of monomeric building blocks was achieved by exploiting readily available amines, anilines, and bisphenols as starting materials. The SuFEx-based polysulfonate formation reaction exhibited excellent efficiency and functional group tolerance, producing polysulfonates with a variety of side chain functionalities in >99 % conversion within 10 min to 1 h. When bearing an orthogonal group on the side chain, the polysulfonates can be further functionalized via click-chemistry-based post-polymerization modification.

A Heck-Matsuda Process for the Synthesis of β-Arylethenesulfonyl Fluorides: Selectively Addressable Bis-electrophiles for SuFEx Click Chemistry

A Heck-Matsuda process for the synthesis of the otherwise difficult to access compounds, β-arylethenesulfonyl fluorides, is described. Ethenesulfonyl fluoride (i.e., vinylsulfonyl fluoride, or ESF) undergoes β-arylation with stable and readily prepared arenediazonium tetrafluoroborates in the presence of the catalyst palladium(II) acetate to afford the E-isomer sulfonyl analogues of cinnamoyl fluoride in 43-97 % yield. The β-arylethenesulfonyl fluorides are found to be selectively addressable bis-electrophiles for sulfur(VI) fluoride exchange (SuFEx) click chemistry, in which either the alkenyl moiety or the sulfonyl fluoride group can be the exclusive site of nucleophilic attack under defined conditions, making these rather simple cores attractive for covalent drug discovery.