The 2,2-difluoroethyl group is an important lipophilic hydrogen bond donor in medicinal chemistry, but its incorporation into small molecules is often challenging. Herein, we demonstrate electrophilic 2,2-difluoroethylation of thiol, amine and alcohol nucleophiles with a hypervalent iodine reagent, (2,2-difluoro-ethyl)(aryl)iodonium triflate, via a proposed ligand coupling mechanism. This transformation offers a complementary strategy to existing 2,2-difluoroethylation methods and allows access to a wide range of 2,2-difluoroethylated nucleophiles, including the drugs Captopril, Normorphine and Mefloquine.

The hypercoordinate [SiH6]2- anion is not stable in solution. Here, we report the room temperature, solution stable molecular [SiH6]2- complex, [{KCa(NON)(OEt2)}2][SiH6] (NON=4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethyl-xanthene)), where the [SiH6]2- anion is stabilised within a supramolecular assembly that mimics the solid-state environment of the anion in the lattice of K2SiH6. Solution-state reactivity of the complex towards carbon monoxide, benzaldehyde, azobenzene and acetonitrile is reported, yielding a range of reduction and C-C coupled products.

Arynes are fleeting, high-energy intermediates that undergo myriad trapping reactions by nucleophiles. Their unusual reactivity compared to other electrophiles can spur unexpected mechanistic pathways enroute to the formation of benzenoid products. Herein we explore a particularly unique case of thermally generated arynes reacting with phosphoranes to form helical dibenzothiophenes and -selenophenes. Multiple new helical polycyclic aromatic products are reported. DP4+ and X-ray crystallographic analysis were used in tandem to confirm the structural topologies of selected products and to demonstrate the utility of DP4+ for distinguishing between isomeric polycyclic aromatic compounds. Lastly, we discuss a plausible mechanism consistent with DFT computations that accounts for the product formation; namely, ligand coupling (i.e., reductive elimination) within a hypervalent, pentacarbon-ligated σ-phosphorane furnishes the dibenzothio- or dibenzoselenophene.

Electrochemically generated hypervalent iodine(III) species are powerful reagents for oxidative C-N coupling reactions, providing access to valuable N-heterocycles. A new electrocatalytic hypervalent iodine(III)-mediated in-cell synthesis of 1H-N-aryl-3,4-dihydroquinolin-2-ones by dehydrogenative C-N bond formation is presented. Catalytic amounts of the redox mediator, a low supporting electrolyte concentration and recycling of the solvent used make this method a sustainable alternative to electrochemical ex-cell or conventional approaches. Furthermore, inexpensive, readily available electrode materials and a simple galvanostatic set-up are applied. The broad functional group tolerance could be demonstrated by synthesizing 23 examples in yields up to 96 %, with one reaction being performed on a 10-fold higher scale. Based on the obtained results a sound reaction mechanism could be proposed.

The diarylation and skeletal diversification of unstrained cyclic amines was exploited to expand and modify the favorable properties of this important substrate class with pivotal roles in drug discovery. Cyclic amines were employed in the synthesis of a novel class of amino-substituted diaryliodonium salts, which were converted to highly functionalized diarylamines through an atom-efficient one-pot N-arylation/ring opening reaction with external nucleophiles. The reaction proceeds through in situ formation of a diarylammonium intermediate that undergoes a nucleophilic ring opening by cleavage of the strong C-N bond. A wide variety of diarylamines was obtained through introduction of two different aryl groups of varied electronics, and the retained iodo-substituent enables downfield diversifications of the products. More than 20 nucleophiles, including amines, phenols, carboxylic acids, thiols and halides, were alkylated with high functional group tolerance, and the strategy proved efficient also in in late-stage functionalization of natural products and pharmaceuticals.

1,2-Dioxygenation of alkenes leads to a structural motif ubiquitous in organic synthons, natural products and active pharmaceutical ingredients. Straightforward and green synthesis protocols starting from abundant raw materials are required for facile and sustainable access to these crucial moieties. Especially industrially abundant aliphatic alkenes have proven to be arduous substrates in sustainable 1,2-dioxygenation methods. Here, we report a highly efficient electrocatalytic diacetoxylation of alkenes under ambient conditions using a simple iodobenzene mediator and acetic acid as both the solvent and an atom-efficient reactant. This transition metal-free method is applicable to a wide range of alkenes, even challenging feedstock alkenes such as ethylene and propylene, with a broad functional group tolerance and excellent faradaic efficiencies up to 87 %. In addition, this protocol can be extrapolated to alkenoic acids, resulting in cyclization of the starting materials to valuable lactone derivatives. With aromatic alkenes, a competing mechanism of direct anodic oxidation exists which enables reaction under catalyst-free conditions. The synthetic method is extensively investigated with cyclic voltammetry.

A series of luminescent, neutral pentacoordinate dithieno[3,2-b:2\',3\'-d]phosphole compounds was synthesized by [4+1] cycloaddition of o-quinones with the corresponding trivalent phospholes. The electronic and geometrical modification of the π-conjugated scaffold implemented here impacts the aggregation behavior of the species in solution. It proved successful in generating species with improved Lewis acidity of the phosphorus center that was then leveraged for small-molecule activation. Hydride abstraction from an external substrate involving the hypervalent species is followed by an intriguing P-mediated umpolung from the hydride to a proton and supports the catalytic potential of this class of main-group Lewis acids for organic chemistry. This study is a comprehensive investigation into various methods, including electronic, chemical, geometric modifications (and sometimes combinations of these approaches) to systematically improve the Lewis acidity of neutral and stable main-group Lewis acids with practical value for a range of chemical transformations.

A systematic investigation of imidazo- and pyrazoloiodazinium salts is presented. Besides a robust synthetic protocol that allowed us to synthesize these novel cyclic iodonium salts in their mono- and dicationic forms, we gained in-depth structural information through single-crystal analysis and demonstrated the ring opening of the heterocycle-bridged iodonium species. For an exclusive set of dicationic imidazoiodaziniums, we show highly delicate post-oxidation functionalizations retaining the hypervalent iodine center.

Phosphoranides comprising three phosphorus carbon bonds are scarcely represented in the literature. We now utilized tris(pentafluoroethyl)phosphane, P(C2 F5 )3 , and cyanobis(pentafluoroethyl)phosphane, P(C2 F5 )2 (CN), featuring electron withdrawing pentafluoroethyl groups, to synthesize such compounds. Metal fluorides MF (M=Ag, Cs) add to P(C2 F5 )3 yielding respective M[P(C2 F5 )3 F] salts. Those M[P(C2 F5 )3 F] subsequently suffer a loss of C2 F4 , furnishing M[P(C2 F5 )2 F2 ]. The cesium salt decomposes instantaneously when warmed to rt, whereas the silver salt decomposes slowly over several days at rt. Treatment of Ag[P(C2 F5 )3 F] with 2,2\'-bipyridine facilitated the isolation and structural characterization of [Ag(bipy){P(C2 F5 )3 F}]. With P(C2 F5 )2 (CN), AgF reacts under substitution of the cyano group yielding P(C2 F5 )2 F, rather than phosphoranide formation. However, [K(18-crown-6)]F adds to P(C2 F5 )2 (CN) furnishing [K(18-crown-6)][P(C2 F5 )2 (CN)F]. Its structural characterization was successful, despite its tendency to undergo an exchange of substituents, yielding [K(18-crown-6)][P(C2 F5 )2 F2 ] and presumably [K(18-crown-6)][P(C2 F5 )2 (CN)2 ]. The latter forms an equilibrium with [K(18-crown-6)]CN and P(C2 F5 )2 (CN) which lies well on side of the phosphane and cyanide salt.

We describe a multi-step continuous-flow procedure for the generation of six-membered diaryliodonium salts. The accompanying scalability and atom economy are significant improvements to existing batch methods. Benzyl acetates are submitted to this two-step procedure as highly available and cheap starting materials. An acid-catalyzed Friedel-Crafts alkylation followed by an anodic oxidative cyclization yielded a defined set of cyclic iodonium salts in a highly substrate-dependent yield.