Bis(4-nitrophenyl)tetrafluorosulfuranes: Synthesis, Isomerization and Structural Characterization

Transition-Metal-Free Approach for Z-Vinyl Fluorides by Hydrofluorination of Alkynes bearing SF4 and SF5 Groups

The synthesis of vinyl fluorides plays a crucial role in various scientific disciplines, including pharmaceutical and materials sciences. Herein, we present a direct and stereoselective hydrofluorination method for the synthesis of Z isomers of vinyl fluorides from alkynes containing unexplored SF5 and SF4 groups. Our strategy employed tetrabutylammonium fluoride (TBAF) as a fluorine source. It demonstrates high compatibility with aryls, biaryls, heteroaryls, and tert-alkyl groups, allowing facile incorporation of SF5 and SF4 groups across the triple bond without any transition-metal catalysts. This approach avoids the potential decomposition of the SF5 or SF4 units via coordination with transition metals or acidic protic sources. Remarkably, this transformation proceeded at room temperature without any additional additives, providing the Z isomer of vinyl fluorides in excellent yield and high selectivity. The presence of a water molecule as a hydrate in TBAF is essential for efficient conversion. This methodology opens new avenues for the synthesis of enchanting SF5 - and SF4 -containing fluorinated vinylic scaffolds, thereby providing advanced opportunities for novel drug discovery and fluorinated polymers.

Expanding the Frontier of Linear Drug Design: Cu-Catalyzed Csp -Csp 3 -Coupling of Electron-Deficient SF4 -Alkynes with Alkyl Iodides

Despite the attractive properties of tetrafluorosulfanyl (SF4 ) compounds in drug discovery, medicinal research on SF4 molecules is hindered by the scarcity of suitable synthetic methodologies. Drawing inspiration from the well-established Sonogashira cross-coupling of terminal alkynes under Pd-catalysis, it is envisioned that SF4 -alkynes can serve as effective coupling partners. To overcome the challenges associated with the electron-deficient nature of SF4 -alkynes and the lability of the SF4 unit under transition-metal catalysis, an aryl radical mediated Csp -Csp 3 cross-coupling reaction is successfully developed under Cu catalysis. This methodology facilitates the coupling of SF4 -alkynes with alkyl iodides, leading to the immediate synthesis of SF4 -attached drug-like molecules. These findings highlight the potential impact of SF4 -containing molecules in the drug industry, paving the way for further research in this emerging field.

(Hetero)aryl-SVI Fluorides: Synthetic Development and Opportunities

(Hetero)arylsulfur compounds where the S atom is in the oxidation state VI represent a large percentage of the molecular functionalities present in organic chemistry. More specifically, (hetero)aryl-SVI fluorides have recently received enormous attention because of their potential as chemical biology probes, as a result of their reactivity in a simple, modular, and efficient manner. Whereas the synthesis and application of the level 1 fluorination at SVI atoms (sulfonyl and sulfonimidoyl fluorides) have been widely studied and reviewed, the synthetic strategies towards higher levels of fluorination (levels 2 to 5) are somewhat more limited. This Minireview evaluates and summarizes the progress in the synthesis of highly fluorinated aryl-SVI compounds at all levels, discussing synthetic strategies, reactivity, the advantages and disadvantages of the synthetic procedures, the proposed mechanisms, and the potential upcoming opportunities.

Synthesis of Pyridine-SF4-Isoxazolines Using the Functionality of trans-Tetrafluoro-λ6-sulfanyl Rodlike Linkers

The tetrafluoro-λ⁶-sulfanyl (SF₄) moiety has been relatively undeveloped since its discovery in the 1970s. In this study, we synthesized pyridine-SF₄-isoxazolines, in which the two heterocycles are connected by a rodlike trans-SF₄ linker, via the regioselective 1,3-dipolar cycloaddition of pyridine-SF₄-alkynes and nitrones in the presence of triethylamine. SF₄ linkers are a viable alternative to para-substituted benzenes, alkynes, and bicyclo[1.1.1]pentyl derivatives in drug design, and pyridine-SF₄-isoxazolines have potential applications in drug development.

Regioselective Synthesis of Pyridine-SF4-Methyl Ketones via Hydration of Pyridine-SF4-Alkynes

Herein, we report the metal-free hydration of pyridine-SF₄-alkynes, under acidic conditions and with reaction durations ranging from 5 min to 10 h at room temperature, to synthesize pyridine-SF₄-methyl ketones in yields of 59-93%. Further, we demonstrate the synthetic applications of the synthesized pyridine-SF₄-methyl ketones, such as chlorination, NaBH₄ reduction, Baeyer-Villiger oxidation, and the generation of enol-triflates. These compounds hold promise as useful building blocks in the syntheses of a wide range of SF₄-containing drug candidates.

Synthesis of an Eccentric Electron-Deficient Fluorinated Motif, Tetrafluoro-λ6-sulfanyl gem-Difluorocyclopropenes

Fluoro-functionalization is now recognized as a critical strategy in drug discovery; however, the accessible fluoro-functional groups are limited. We herein introduce an eccentric, fully fluorinated motif, trans-tetrafluoro-λ⁶-sulfanyl gem-difluorocyclopropene 2. This novel motif is highly lipophilic and polarized, enabling a connection of two independent groups via three continuous atoms with a large angle of pseudo cis configuration. The target motif was synthesized via a [2+1] cycloaddition of electron-deficient (hetero)aryl-SF₄-alkynes 1 with an electrophilic difluorocarbene source.

Difluoro(aryl)(perfluoroalkyl)-λ4 -sulfanes and Selanes: Missing Links of Trichloroisocyanuric Acid/Potassium Fluoride Chemistry

The TCICA/KF approach to oxidative fluorination of heteroatoms has emerged as a surprisingly simple, safe, and versatile surrogate to classically challenging fluorination reactions. Although polyfluorination (or chlorofluorination) of diaryl disulfides, diaryl diselenides, diaryl ditellurides, aryl iodides, and aryl(perfluoroalkyl)tellanes has been described, the application of this TCICA/KF methodology to aryl(perfluoroalkyl)sulfanes and selanes remains an area of unexplored chemical space. Accordingly, to address the "missing links" in the developing series of chalcogen-based substrate reactivity, we report mild syntheses of metastable difluoro(aryl)(perfluoroalkyl)-λ⁴ -sulfanes and selanes. As only limited examples of these species exist in the current literature (accessible only by using F₂ or XeF₂ /HF), we have carried out detailed structural analyses, primarily using NMR and SC-XRD data. In addition, we investigate the effect of the perfluoroalkyl chain on the outcome of oxidative fluorination, and, finally, we provide preliminary evidence that difluoro(aryl)(trifluoro-methyl)-λ⁴ -sulfanes may act as fluorinating reagents.

An eccentric rod-like linear connection of two heterocycles: synthesis of pyridine trans-tetrafluoro-λ6-sulfanyl triazoles

The trans-tetrafluoro-λ6-sulfane (SF4) group has been utilized as a unique three-dimensional building block for the linear connection of two independent N-heterocycles, pyridines and triazoles. The linearly connected heterocyclic compounds were synthesized by thermal Huisgen 1,3-dipolar cycloaddition between previously unknown pyridine SF4-alkynes and readily available azides, providing a series of rod-like SF4-connected N-heterocycles in good to excellent yields. X-ray crystallographic analysis of the target products revealed the trans-geometry of the SF4 group, which linearly connects two independent N-heterocycles. This research will open the field of chemistry of SF4-connected heterocyclic compounds.

Synthesis of pyridine trans-tetrafluoro-λ6-sulfane derivatives via radical addition

Pyridine-trans-SF₄-alkenes or -alkanes have been synthesized for the first time via the radical addition reactions of pyridine-trans-SF₄Cl to alkynes or alkenes in good to high yields.

Isolation and Molecular Structure of the Organo-persulfuranes [12−S−6(C6)]

Reactions of bis(2,2'-biphenylylene)sulfuranyl bis(tetrafluoroborate) [(8-S-4(C4)]2+ with organo-lithium reagents (PhLi and MeLi) gave bis(2,2'-biphenylylene)di-C-substituted persulfuranes as a first persulfurane [12-S-6(C6)] having only carbon ligands. These compounds have been characterized by 1H and 13C NMR and mass spectroscopies. The structure of the dimethyl derivative was determined by X-ray crystallographic analysis, revealing that it has a distorted octahedral geometry with the two methyl ligands cis to each other, and subsequently, it was analyzed by an ab initio calculation.

Quaternary salts containing the pentafluorosulfanyl (SF5) group

The first quaternary salts of pyridine (2), N-methyl imidazole (3), N-propyl triazole (4), and pyridazine (5) that contain the pentafluorosulfanyl (SF(5)) group were prepared and characterized. Neat reactions of the aromatic nitrogen compounds with SF(5)(CF(2))(n)(CH(2))(m)I (n = 2 or 4, m = 2 or 4) gave quaternary iodides 6a-c, 7a-c, 8a, and 9a,b, which were metathesized with LiN(SO(2)CF(3))(2) to form the bis(trifluoromethylsulfonyl)amides 10a-c, 11a-c, 12a, and 13a,b, in high yields. With the exception of the pyridine bis(trifluoromethylsulfonyl)amide salts, the compounds melted or exhibited a T(g) at <0 degrees C. The methylimidazolium, pyridinium, and pyridazinium salts exhibited densities of approximately 2 g/cm(3). Particularly striking was the density of CF(3)(CF(2))(5)(CH(2))(2)-pyridazinium N(CF(3)SO(2))(2) measured at 2.13 g/cm(3); however, an atypically high density for the 1-CF(3)(CF(2))(5)(CH(2))(2)-3-methyl imidazolium amide (14) was also observed at 1.77 g/cm(3). All quaternary salts were characterized via IR, (19)F, (1)H, and (13)C NMR spectra and elemental analyses.