Pyrylium Salts Acting as Both Energy Transfer and Electron Transfer Photocatalysts for E→Z Isomerization of Activated Alkenes and Cyclization of Cinnamic or Biaryl Carboxylic Acids

2,4,6-Triarylpyrylium salts are stable, easily available and cheap. However, only their elec-tron transfer oxidation ability was explored. We herein report that they could perform both energy transfer and electron transfer...

Stereospecific, Pyrylium Salt-Catalyzed O-Glycosylations of Phenols and Alkyl Alcohols

Despite many years of invention, the field of carbohydrate chemistry remains rather inaccessible to non-specialists, which limits the scientific impact and reach of the discoveries made in the field. Aiming to increase the availability of stereoselective glycosylation chemistry for non-specialists, we have discovered that several commercially available pyrylium salts catalyze stereospecific O-glycosylations of a wide range of phenols and alkyl alcohols. This catalytic reaction utilizes trichloroacetimidates, an easily accessible and synthetically proven electrophile, takes place under air and only initiates when all three reagents are mixed, which should provide better reproducibility by non-specialists. The reaction is stereospecific, resulting in β-specific glycosylations from α-trichloroacetimidates, whilst an α-selective glycosylation proceeds from β-trichloroacetimidates. A mechanistic study revealed that the reaction likely proceeds via an SN2-like substitution on the protonated electrophile.

Regioselective synthesis of functionalized pyrazole-chalcones via a base mediated reaction of diazo compounds with pyrylium salts

A base-mediated reaction of triaryl/alkyl pyrylium tetrafluoroborate salts with α-diazo-phosphonates, sulfones and trifluoromethyl compounds affords the corresponding functionalized pyrazole-chalcones as 5-P-5 and 3-P-3 tautomeric mixture.

Efficient cascade reactions for luminescent pyrylium biolabels catalysed by light rare-earth elements

Luminescent pyrylium salts have been efficiently synthesized from cascade reactions, coupled to supramolecular assembly and used for protein labeling.

Condensation of Pyrylium Salts with Mixed Anhydrides: Arylethers, Arylamines and Sterically Congested Aromatics

The condensation of easily accessible and widely functionalizable 2,4,6-triaryl pyrylium salts with mixed anhydrides, formed in situ from α-functionalized sodium acetates and an anhydride solvent, leads in good yields to...

Catalytic Enantioselective Reactions with (Benzo)Pyrylium Salts

The use of (benzo)pyrylium salts as versatile synthetic building blocks has become an attractive platform for the preparation of valuable heterocyclic compounds. Besides other numerous direct applications of (benzo)pyryliums, the intrinsic electrophilic nature of these species or the dipole character of the related oxidopyrylium derivatives have been exploited towards the development of enantioselective transformations such as nucleophilic dearomatization and cycloaddition reactions. This review aims at providing an overview on the relevant catalytic enantioselective methodologies developed in the past years, which are presented considering the involved metal- and/or organic catalytic system, as well as the type of reaction.

4-(azulen-1-yl)-2,6-diphenylchalcogenopyrylium Perchlorates; Synthesis and Characterization

2,6-Diphenyl substituted thio- and seleno-pyrylium salts with azulen-1-yl moieties in 4-position were prepared from phenylacetylene going through chalcogenopyrones and 4-chloro-chalcogenopyrylium salts as intermediates. The final step of synthesis involves the electrophile substitution in 1-position of azulenes with the obtained chloro-derivatives and the products isolation as stable perchlorates. The electronic and magnetic spectra of products are presented and compared with those of the corresponding pyrylium salts.