Robust and Self-Cleaning Electrochemical Production of Periodate.

Periodate, a platform oxidizer, can be electrochemically recycled in a self-cleaning process. Electrosynthesis of periodate is well established at boron-doped diamond (BDD) anodes. However, recovered iodate and other iodo species for recycling can contain traces of organic impurities from previous applications.

The "Green" Electrochemical Synthesis of Periodate.

High-grade periodate is relatively expensive, but is required for many sensitive applications such as the synthesis of active pharmaceutical ingredients. These high costs originate from using lead dioxide anodes in contemporary electrochemical methods and from expensive starting materials. A direct and cost-efficient electrochemical synthesis of periodate from iodide, which is less costly and relies on a readily available starting material, is reported.

Divergent gold-catalysed reactions of cyclopropenylmethyl sulfonamides with tethered heteroaromatics.

Cyclopropenylmethyl sulfonamides with tethered heteroaromatics have been demonstrated to undergo divergent gold-catalysed cyclisation reactions. A formal dearomative (4+3) cycloaddition takes place with furan-tethered substrates, yielding densely functionalised 5,7-fused heterocycles related to the bioactive curcusone natural products. Indole-tethered substrates display divergent reactivity giving biologically important tetrahydro-β-carbolines via a Friedel-Crafts mechanism.

The Gold(I)-Mediated Domino Reaction to Fused Diphenyl Phosphoniumfluorenes: Mechanistic Consequences for Gold-Catalyzed Hydroarylations and Application in Solar Cells.

A domino sequence, involving a phosphinoauration and a gold-catalyzed 6-endo-dig cyclization step, was developed. Starting from modular and simple-to-prepare phosphadiynes, π-extended phosphoniumfluorenes were synthesized. The mechanistic proposal was supported by kinetic measurements and by the trapping of key intermediates.

Direct Access to π-Extended Phosphindolium Salts by Simple Proton-Induced Cyclization of (o-Alkynylphenyl)phosphanes.

A detailed synthetic and mechanistic study for the synthesis of phosphindolium salts from easy accessible (o-alkynylphenyl)phosphanes is reported. Mechanistic investigation indicates a fast protonation at phosphorus as evidenced by the isolation of the phosphonium intermediate, followed by a protophosphonylation reaction across the alkyne moiety. DFT calculations support our mechanistic proposal and indicate a reaction highly exergonic compared to our recently reported phosphinoauration.

Intramolecular anti-Phosphinoauration of Alkynes: An FLP-Motivated Approach to Stable Aurated Phosphindolium Complexes.

The synthesis of aurated phosphindolium complexes from easy accessible 1,5-alkynylphosphine derivatives has been studied by using gold(I) complexes featuring carbene and phosphine ligands as initiators. Upon formation of the mixed phosphine NHC/phosphine gold species, elevated temperatures induced the cyclization to give stable aurated phosphindolium salts, which is supported by DFT calculations. The key elementary step that comprises a yet unknown anti-phosphinoauration of an unactivated alkyne is favored if bulky NHC ligands are used which was analyzed by kinetic measurements.

A Mechanistic Investigation of the Gold(III)-Catalyzed Hydrofurylation of C-C Multiple Bonds.

The gold-catalyzed direct functionalization of aromatic C-H bonds has attracted interest for constructing organic compounds which have application in pharmaceuticals, agrochemicals, and other important fields. In the literature, two major mechanisms have been proposed for these catalytic reactions: inner-sphere syn-addition and outer-sphere anti-addition (Friedel-Crafts-type mechanism). In this article, the AuCl-catalyzed hydrofurylation of allenyl ketone, vinyl ketone, ketone, and alcohol substrates is investigated with the aid of density functional theory calculations, and it is found that the corresponding functionalizations are best rationalized in terms of a novel mechanism called "concerted electrophilic ipso-substitution" (CEIS) in which the gold(III)-furyl σ-bond produced by furan auration acts as a nucleophile and attacks the protonated substrate via an outer-sphere mechanism.

Expanding the Scope of the Gold(I)-Catalyzed Rautenstrauch Rearrangement: Protic Additives.

The synthesis of substituted 2-cyclopentenones using a commercially available gold(I) catalyst is described under flexible reaction conditions. During the course of our investigations, we discovered that using a proton source as an additive is required to obtain the desired substituted cyclopentenones in good yields.

Concise synthesis of aryl-C-nucleosides by Friedel-Crafts alkylation.

A fast and simplified synthesis of 1',2'-dideoxy-1'-pyrenyl-riboside and several other C-nucleosides is shown. Shelf-stable 1-O-methyl-3,5-di-O-toluoyl-2-deoxyribose is demonstrated to serve as a versatile glycosyl donor in Lewis acid promoted Friedel-Crafts alkylations of unsubstituted pyrene and other inexpensive arenes such as fluorene and methylnaphthalene. The reaction conditions favour the formation of beta-configurated C-nucleosides which renders additional epimerisation steps unnecessary.