Optimization and Gram-Scale Preparation of S-Trifluoromethyl Sulfoximines and Sulfilimino Iminiums, Powerful Reagents for the Late Stage Introduction of the CF3 Group

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.

Oxidation of N-trifluoromethylthio sulfoximines using NaOCl·5H2O

N-Trifluoromethylthio sulfoximines are biologically interesting compounds, but their potential is still poorly understood. The oxidation of N-trifluoromethylthio sulfoximines led to their corresponding sulfoxide derivatives as a new class of compounds, when using sodium hypochlorite pentahydrate (NaOCl·5H2O) as a green and relatively unexplored reagent. The reactions took place with a small excess of oxidant under environmentally friendly conditions in EtOAc for 16 h at room temperature. Noteworthy distinctions of this transformation are the simplicity, high selectivity, energy and cost efficiency, minimal amounts of non-hazardous waste, isolation of most of the products without the additional need for chromatographic purification, and simple scalability to gram reactions without deterioration of the yield. The reaction exhibited excellent green chemistry metrics with high atom economy (82.0%), actual atom economy (79.5%), reaction mass efficiency (79.7%), E-factor (16.48) and a very high EcoScale score (84.5). Competitive experiments demonstrated that electron-rich substrates are more reactive than their electron-poor counterparts. Furthermore, the Suzuki-Miyaura functionalization of N-trifluoromethylsulfaneylidene sulfoximine could be achieved depending on the conditions, resulting in coupling products with or without an introduced sulfoxide moiety. Sonogashira coupling of N-trifluoromethylsulfaneylidene sulfoximine furnished the expected acetylene derivative in high yield, and the reaction conditions are compatible with the newly introduced sulfaneylidene functionality. Bromine and nickel catalysts were also shown to be deprotecting agents of the sulfoxide group. A selected N-trifluoromethylsulfaneylidene sulfoximine demonstrated its stability in water in the presence of air and in dilute hydrochloric acid, while it converted back to the parent sulfoximine under basic conditions.

Perfluoroalkyl Selenoxides, Selenones and Selenoximines: General Preparation and Properties

A selective access to perfluoroalkyl selenoxides, via Oxone® as oxidant or to selenones by using a Polyoxometalate-based Ionic Liquid (POM-IL) as a catalyst for the oxidation step is described. The reaction works with various perfluoralkyl chains and substituents with satisfactory to excellent yields. A two-step one-pot reaction from selenocyanates was performed to gain access to perfluoroalkyl selenoxides. The previously unknown perfluoroalkyl selenoximines family was also prepared with good yields. Having unlocked two strategies for the synthesis of fluoroalkylated Se^IV and Se^VI compounds, we then evaluated the Hansch-Leo lipophilicity parameters of these groups. Finally, asymmetric aryl perfluoroalkyl selenoximines were resolved to determine their absolute configurations.

Remote Radical Trifluoromethylation: A Unified Approach to the Selective Synthesis of γ-Trifluoromethyl α,β-Unsaturated Carbonyl Compounds

Site-selective trifluoromethylation of silyl dienol ethers derived from α,β-unsaturated aldehydes, ketones, and amides was achieved for the first time in the remote γ position. This photoredox catalyzed process is quite general to compounds bearing many functionalities and is applicable to the late-stage functionalization of biorelevant molecules. The use of S-perfluoroalkyl sulfoximines as ·R_F radical sources enables the generalization of the reaction to other perfluoroalkyl groups (R_F = CF₂H, C₄F₉). Importantly, an unprecedented enantioselective C(sp³)-H perfluoroalkylation process is disclosed.

Structure and Reactivity of N-Heterocyclic Alkynyl Hypervalent Iodine Reagents

Ethynylbenziodoxol(on)e (EBX) cyclic hypervalent iodine reagents have become popular reagents for the alkynylation of radicals and nucleophiles, but only offer limited possibilities for further structure and reactivity fine-tuning. Herein, the synthesis of new N-heterocyclic hypervalent iodine reagents with increased structural flexibility based on amide, amidine and sulfoximine scaffolds is reported. Solid-state structures of the reagents are reported and the analysis of the I-Calkyne bond lengths allowed assessing the trans-effect of the different substituents. Molecular electrostatic potential (MEP) maps of the reagents, derived from DFT computations, revealed less pronounced σ-hole regions for sulfonamide-based compounds. Most reagents reacted well in the alkynylation of β-ketoesters. The alkynylation of thiols afforded more variable yields, with compounds with a stronger σ-hole reacting better. In metal-mediated transformations, the N-heterocyclic hypervalent iodine reagents gave inferior results when compared to the O-based EBX reagents.

One-Pot Synthesis of N-Iodo Sulfoximines from Sulfides

This is the first report on the synthesis and characterization of N-iodo sulfoximines. The synthesis was designed as a room temperature one-pot cascade reaction from readily available sulfides as starting compounds, converted into sulfoximines by reaction with ammonium carbonate and (diacetoxyiodo)benzene, followed by iodination with N-iodosuccinimide or iodine in situ, in up to 90% isolated yields, also at a multigram scale. Iodination of aryls with N-iodo sulfoximines, oxidation, and conversion to N-SCF₃ congeners have been demonstrated.

Photoredox-Catalyzed Selective Synthesis of Allylic Perfluoroalkanes from Alkenes

We report herein a novel photoredox-catalyzed synthesis of allylic trifluoromethanes. The use of sulfilimino iminium as a source of trifluoromethyl radicals proves crucial to achieving high selectivity. Importantly, both styrene derivatives and unactivated alkenes are for the first time suitable partners for this process. The mild reaction conditions are compatible with a variety of functional groups. Remarkably, this method is readily broadened to other perfluoroalkyl groups (R_F =CFCl₂ , CF₂ Br, C₄ F₉ ). An extensive mechanistic study is also provided.