Electrooxidative Fluorofunctionalization of Arylcyclopropanes.

The work herein demonstrates the viability of an electrochemical oxidative protocol for the expedient realization of 1,3-fluorofunctionalization of arylcyclopropanes under catalyst- and oxidant-free conditions. Given the relatively low nucleophilicity of fluoride ion, the counterintuitive outcome that the ring-opening is initiated by nucleophilic fluorination is rationalized by invoking tight ion pair between aryl radical cation and BF4- counterion. By integrating alcohols, acids, and N-heterocycles as the terminating nucleophiles, straightforward 1,3-fluorooxygenation and 1,3-fluoroamination are smoothly achieved.

One-Pot Synthesis of 2,3-Disubstituted Indanone Derivatives in Water under Exogenous Ligand-Free and Mild Conditions.

Diverse 2,3-substituted indanones are accessed in an efficient and robust protocol by a rhodium-catalyzed tandem carborhodium/cyclization and intramolecular proton shift pathway. The reaction is compatible with a broad range of functional internal acetylenes, especially for natural and functionalized alkynes derivatives, affording the desired indanones in good to excellent yields. Remarkably, this reaction features very mild and sustainable conditions using water as the sole solvent and without exogenous ligands. Control studies support that indanone is formed through the intramolecular proton transfer process from the key intermediate indenol.

Direct Access to α,ß-Unsaturated Ketones via Rh/MgCl2-Mediated Acylation of Vinylsilanes.

We report herein the facile and practical construction of α,ß-unsaturated ketones via rhodium-catalyzed direct acylation of vinylsilanes with readily available and abundant carboxylic acids. This protocol features access to a diverse array of synthetically useful functionalities with moderate to excellent yields. More importantly, the late-stage functionalization of pharmaceuticals was also realized with synthetically useful yield.

Palladium-Catalyzed Electrophilic Functionalization of Pyridine Derivatives through Phosphonium Salts.

Herein, we report a highly efficient and practical method for pyridine-derived heterobiaryl synthesis through palladium-catalyzed electrophilic functionalization of easily available pyridine-derived quaternary phosphonium salts. The nice generality of this reaction was goes beyond arylation, enabling facile incorporation of diverse carbon-based fragments, including alkenyl, alkynyl, and also allyl fragments, onto the pyridine core. Notably, the silver salt additive is revealed to be of vital importance for the success of this transformation and its pivotal role as transmetallation mediator, which guarantees a smooth transfer of pyridyl group to palladium intermediate, is also described.

Visible-Light-Promoted Oxo-Sulfonylation of Ynamides with Sulfonic Acids.

A visible-light-promoted oxo-sulfonylation of ynamides with sulfonic acids is reported, giving rise to a collection of functionalized α-sulfonylated amides in a straightforward manner. The reaction proceeds sequentially through a cascade of electrophilic addition and photoinduced sulfonyl radical-sustained skeleton rearrangement. The high atom economy, mild reaction conditions, and wide substrate scope comprised the merits of this synthetic transformation.

Optimizing the lifetimes of phenoxonium cations derived from vitamin E via structural modifications.

Systematic synthesis of a number of new phenolic compounds with structures similar to vitamin E led to the identification of several sterically hindered compounds that when electrochemically oxidised in acetonitrile in a -2e(-)/-H(+) process formed phenoxonium diamagnetic cations that were resistant to hydrolysis reactions. The reactivity of the phenoxonium ions was ascertained by performing cyclic voltammetric scans during the addition of carefully controlled quantities of water into acetonitrile solutions, with the data modelled using digital simulation techniques.

Competing hydrogen-bonding, decomposition, and reversible dimerization mechanisms during the one- and two-electron electrochemical reduction of retinal (vitamin A).

Retinal (R) can be sequentially voltammetrically reduced in CH3CN in two one-electron processes to form first the anion radical (R(•-)) at -1.75 (±0.04) V vs Fc/Fc(+) (Fc = ferrocene) then the dianion (R(2-)) at -2.15 (±0.04) V vs Fc/Fc(+). The anion radical undergoes a reversible dimerization reaction to form the dianion (R2(2-)) with a forward dimerization rate constant k(dim) = 8 × 10(2) L mol(-1) s(-1) and a reverse monomerization rate constant k(mon) = 2 × 10(-2) s(-1) at 295 K. All three anion species (anion radical, dianion, and dimer dianion) undergo hydrogen-bonding interactions with water that is present at millimolar levels in the solvent. As the water content of the solvent increases, the fate of the reduced compounds is determined by chemically irreversible hydrolysis reactions with H2O and decomposition reactions of the highly charged R(2-). Bulk-controlled potential electrolysis experiments combined with NMR analysis of the reaction solutions indicate that the reduction occurs at the aldehyde group of retinal. The electrochemical data obtained under a range of experimental conditions (varying voltammetric scan rates, temperatures, H2O content of solutions, and retinal concentrations) were modeled by digital simulation techniques to determine the kinetic and thermodynamic parameters associated with all of the homogeneous reactions.