Chemoselektive, modulare Diversifikation polyhalogenierter Arylfluorosulfate (ArOSO 2 F), ermöglicht durch ein luftstabiles Pd I ‐Dimer

Radical Fluorosulfonamidation: A Facile Access to Sulfamoyl Fluorides

Recently, the introduction of fluorosulfonyl (-SO2F) groups have attracted considerable research interests, as this moiety could often afford enhanced activities and new functions in the context of chemical biology and drug discovery. Herein, we report the design and synthesis of 1-fluorosulfamoyl-pyridinium (FSAP) salts, which could serve as an effective photoredox-active precursor to fluorosulfamoyl radicals and enable the direct radical C-H fluorosulfonamidation of a variety of (hetero)arenes. This method features mild conditions, visible light, broad substrate scope, good group tolerance, etc., and a metal-free protocol is also viable by using organic photocatalysts. Further, FSAP can also be applied to the radical functionalization of alkenes via 1,2-difunctionalization, radical distal migration, tandem radical-polar crossover reactions, etc. In addition, a formal C-H methylamination of (hetero)arenes by combining this radical C-H fluorosulfonamidation with subsequent hydrolysis as well as product derivatization are also demonstrated.

Rapid and Modular Access to Vinyl Cyclopropanes Enabled by Air-stable Palladium(I) Dimer Catalysis

While vinyl cyclopropanes are valuable functional groups in drugs or natural products as well as established precursors to trigger a rich variety of synthetic transformations, their reactive nature can make their installation via direct catalytic approaches challenging. We herein present a modular access to (di)vinyl cyclopropanes under very mild conditions and full conservation of stereochemistry, allowing access to the cis or trans cyclopropane- as well as E or Z vinyl-stereochemical relationships. Our protocol relies on air-stable dinuclear PdI catalysis, which enables rapid (<30 min) and selective access to a diverse range of vinyl cyclopropane motifs at room temperature, even on gram scale.

Modular Generation of (Iodinated) Polyarenes Using Triethylgermane as Orthogonal Masking Group

While the modular construction of molecules from suitable building blocks is a powerful means to more rapidly generate a diversity of molecules than through customized syntheses, the further evolution of the underlying coupling methodology is key to realize widespread applications. We herein disclose a complementary modular coupling approach to the widely employed Suzuki coupling strategy of boron containing precursors, which relies on organogermane containing building blocks as key orthogonal functionality and an electrophilic (rather than nucleophilic) unmasking event paired with air-stable PdI dimer based bond construction. This allows to significantly shorten the reaction times for the iterative coupling steps and/or to close gaps in the accessible compound space, enabling straightforward access also to iodinated compounds.

Air-Stable PdI Dimer Enabled Remote Functionalization: Access to Fluorinated 1,1-Diaryl Alkanes with Unprecedented Speed

While remote functionalization via chain walking has the potential to enable access to molecules via novel disconnections, such processes require relatively long reaction times and can be in need of elevated temperatures. This work features a remote arylation in less than 10 min reaction time at room temperature over a distance of up to 11 carbons. The unprecedented speed is enabled by the air-stable PdI dimer [Pd(μ-I)(PCy2 t Bu)]2 , which in contrast to its Pt Bu3 counterpart does not trigger direct coupling at the initiation site, but regioconvergent and chemoselective remote functionalization to yield valuable fluorinated 1,1-diaryl alkanes. Our combined experimental and computational studies rationalize the origins of switchability, which are primarily due to differences in dispersion interactions.

Electrochemical Oxo-Fluorosulfonylation of Alkynes under Air: Facile Access to β-Keto Sulfonyl Fluorides

Radical fluorosulfonylation is emerging as an appealing approach for the synthesis of sulfonyl fluorides, which have widespread applications in many fields, in particular in the context of chemical biology and drug development. Here, we report the first investigation of FSO₂ radical generation under electrochemical conditions, and the establishment of a new and facile approach for the synthesis of β-keto sulfonyl fluorides via oxo-fluorosulfonylation of alkynes with sulfuryl chlorofluoride as the radical precursor and air as the oxidant. This electrochemical protocol is amenable to access two different products (β-keto sulfonyl fluorides or α-chloro-β-keto sulfonyl fluorides) with the same reactants. The β-keto sulfonyl fluoride products can be utilized as useful building blocks in the synthesis of various derivatives and heterocycles, including the first synthesis of an oxathiazole dioxide compound. Furthermore, some β-keto sulfonyl fluorides and derivatives exhibited notably potent activities against Bursaphelenchus xylophilus and Colletotrichum gloeosporioides.

Introducing A New Class of Sulfonyl Fluoride Hubs via Radical Chloro-Fluorosulfonylation of Alkynes

Sulfonyl fluorides have widespread applications in many important fields, including ligation chemistry, chemical biology, and drug discovery. Therefore, new methods to increase the synthetic efficiency and expand the available structures of sulfonyl fluorides are highly in demand. Here, we introduce a new and powerful class of sulfonyl fluoride hubs, β-chloro alkenylsulfonyl fluorides (BCASF), which can be constructed via radical chloro-fluorosulfonyl difunctionalization of alkynes under photoredox conditions. BCASF molecules exhibit versatile reactivities and well undergo a series of transformations at the chloride site while keeping the sulfonyl fluoride group intact, including reduction, Suzuki coupling, Sonogashira coupling, as well as nucleophilic substitution with various nitrogen, oxygen, and sulfur nucleophiles. By using BCASF as a synthetic hub, a wide range of sulfonyl fluorides becomes readily accessible, such as cis alkenylsulfonyl fluorides, dienylsulfonyl fluorides, and ynenylsulfonyl fluorides, which are challenging or even not possible to synthesize before with the known methods. Moreover, further application of BCASF to the late-stage modification of peptides and drugs is also demonstrated.

Chemodivergence between Electrophiles in Cross-Coupling Reactions

Chemodivergent cross-couplings are those in which either one of two (or more) potentially reactive functional groups can be made to react based on choice of conditions. In particular, this review focuses on cross-couplings involving two different (pseudo)halides that can compete for the role of the electrophilic coupling partner. The discussion is primarily organized by pairs of electrophiles including chloride vs. triflate, bromide vs. triflate, chloride vs. tosylate, and halide vs. halide. Some common themes emerge regarding the origin of selectivity control. These include catalyst ligation state and solvent polarity or coordinating ability. However, in many cases, further systematic studies will be necessary to deconvolute the influences of metal identity, ligand, solvent, additives, nucleophilic coupling partner, and other factors on chemoselectivity.

Radical Fluorosulfonylation: Accessing Alkenyl Sulfonyl Fluorides from Alkenes

Sulfonyl fluorides have widespread applications in many fields. In particular, their unique biological activity has drawn considerable research interest in the context of chemical biology and drug discovery in the past years. Therefore, new and efficient methods for the synthesis of sulfonyl fluorides are highly in demand. In contrast to extensive studies on FSO₂ ⁺ -type reagents, a radical fluorosulfonylation reaction with a fluorosulfonyl radical (FSO₂ ^. ) remains elusive so far, probably owing to its instability and difficulty in generation. Herein, the development of the first radical fluorosulfonylation of alkenes based on FSO₂ radicals generated under photoredox conditions is reported. This radical approach provides a new and general access to alkenyl sulfonyl fluorides, including structures that would otherwise be challenging to synthesize with previously established cross-coupling methods. Moreover, extension to the late-stage fluorosulfonylation of natural products is also demonstrated.

Catalysis with Palladium(I) Dimers

Dinuclear PdI complexes have found widespread applications as diverse catalysts for a multitude of transformations. Initially their ability to function as pre-catalysts for low-coordinated Pd0 species was harnessed in cross-coupling. Such PdI dimers are inherently labile and relatively sensitive to oxygen. In recent years, more stable dinuclear PdI -PdI frameworks, which feature bench-stability and robustness towards nucleophiles as well as recoverability in reactions, were explored and shown to trigger privileged reactivities via dinuclear catalysis. This includes the predictable and substrate-independent, selective C-C and C-heteroatom bond formations of poly(pseudo)halogenated arenes as well as couplings of arenes with relatively weak nucleophiles, which would not engage in Pd0 /PdII catalysis. This Minireview highlights the use of dinuclear PdI  complexes as both pre-catalysts for the formation of highly active Pd0 and PdII -H species as well as direct dinuclear catalysts. Focus is set on the mechanistic intricacies, the speciation and the impacts on reactivity.

A Next-Generation Air-Stable Palladium(I) Dimer Enables Olefin Migration and Selective C-C Coupling in Air

We report a new air-stable PdI dimer, [Pd(μ-I)(PCy2 t Bu)]2 , which triggers E-selective olefin migration to enamides and styrene derivatives in the presence of multiple functional groups and with complete tolerance of air. The same dimer also triggers extremely rapid C-C coupling (alkylation and arylation) at room temperature in a modular and triply selective fashion of aromatic C-Br, C-OTf/OFs, and C-Cl bonds in poly(pseudo)halogenated arenes, displaying superior activity over previous PdI dimer generations for substrates that bear substituents ortho to C-OTf.

Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations

While halogenation is of key importance in synthesis and radioimaging, the currently available repertoire is largely designed to introduce a single halogen per molecule. This report makes the selective introduction of several different halogens accessible. Showcased here is the privileged stability of nontoxic aryl germanes under harsh fluorination conditions (that allow selective fluorination in their presence), while displaying superior reactivity and functional-group tolerance in electrophilic iodinations and brominations, outcompeting silanes or boronic esters under rapid and additive-free conditions. Mechanistic experiments and computational studies suggest a concerted electrophilic aromatic substitution as the underlying mechanism.

Modular and Selective Arylation of Aryl Germanes (C-GeEt3 ) over C-Bpin, C-SiR3 and Halogens Enabled by Light-Activated Gold Catalysis

Selective Csp 2 -Csp 2 couplings are powerful strategies for the rapid and programmable construction of bi- or multiaryls. To this end, the next frontier of synthetic modularity will likely arise from harnessing the coupling space that is orthogonal to the powerful Pd-catalyzed coupling regime. This report details the realization of this concept and presents the fully selective arylation of aryl germanes (which are inert under Pd0 /PdII catalysis) in the presence of the valuable functionalities C-BPin, C-SiMe3 , C-I, C-Br, C-Cl, which in turn offer versatile opportunities for diversification. The protocol makes use of visible light activation combined with gold catalysis, which facilitates the selective coupling of C-Ge with aryl diazonium salts. Contrary to previous light-/gold-catalyzed couplings of Ar-N2 + , which were specialized in Ar-N2 + scope, we present conditions to efficiently couple electron-rich, electron-poor, heterocyclic and sterically hindered aryl diazonium salts. Our computational data suggest that while electron-poor Ar-N2 + salts are readily activated by gold under blue-light irradiation, there is a competing dissociative deactivation pathway for excited electron-rich Ar-N2 + , which requires an alternative photo-redox approach to enable productive couplings.

N-Trifluoromethyl Hydrazines, Indoles and Their Derivatives

Reported herein is the first efficient strategy to synthesize a broad range of unsymmetrical N-CF₃ hydrazines, which served as platform to unlock numerous currently inaccessible derivatives, such as tri- and tetra-substituted N-CF₃ hydrazines, hydrazones, sulfonyl hydrazines, and valuable N-CF₃ indoles. These compounds proved to be remarkably robust, being compatible with acids, bases, and a wide range of synthetic manipulations. The feasibility of RN(CF₃ )-NH₂ to function as a directing group in C-H functionalization is also showcased.