Organosulphur and organoselenium compounds as emerging building blocks for catalytic systems for O-arylation of phenols, a C-O coupling reaction

Diaryl ethers form an important class of organic compounds. The classic copper-mediated Ullmann diaryl ether synthesis has been known for many years and involves the coupling of phenols with aryl halides. However, the use of high reaction temperature, high catalyst loading and expensive ligands has created a need for the development of alternative catalytic systems. In the recent past, organosulphur and organoselenium compounds have been used as building blocks for developing homogeneous, heterogeneous and nanocatalysts for this C-O coupling reaction. Homogeneous catalytic systems include preformed complexes of metals with organosulphur and organoselenium ligands. The performance of such complexes is influenced dramatically by the nature of the chalcogen (S or Se) donor site of the ligand. Nanocatalytic systems (including Pd₁₇Se₁₅, Pd₁₆S₇ and Cu_1.8S) have been designed using a single-source precursor route. Heterogeneous catalytic systems contain either metal (Cu or Pd) or metal chalcogenides (Pd₁₇Se₁₅ or Cu_1.8S) as catalytically active species. This article aims to cover the simple and straightforward methodologies and approaches that are adopted for developing catalytically relevant organosulfur and organoselenium ligands, their homogeneous metal complexes, heterogeneous and nanocatalysts. The effects of chalcogen (S or Se) donor, halogen (Cl/Br/I) of aryl halide, nature (electron withdrawing or electron donating) of substituents present on the aromatic ring of aryl halides or substituted phenols and position (ortho or para) of substitution on the results of catalytic reactions have been critically analyzed and summarized. The effect of composition (Pd₁₇Se₁₅ or Pd₁₆S₇) on the performance of nanocatalytic systems is also highlighted. Substrate scope has also been discussed in all three types of catalysis. The superiority of heterogeneous catalytic systems (e.g., Pd₁₇Se₁₅ immobilised on graphene oxide) indicates the bright future possibilities for the development of efficient catalytic systems using similar or tailored ligands for this reaction.

Copper-catalyzed efficient access to 2,4,6-triphenyl pyridines via oxidative decarboxylative coupling of aryl acetic acids with oxime acetates

A simple and efficient strategy for the synthesis of 2,4,6- triphenyl pyridines has been developed through copper-catalysed oxidative decarboxylative coupling of C(sp3) aryl acetic acids with oxime acetates using oxygen as a sole terminal oxidant.

Synthesis of selenated isochromenones by AgNO3-catalyzed three-component reaction of alkynylaryl esters, selenium powder and ArB(OH)2

Reported is the AgNO₃-catalyzed three-component reaction of alkynylaryl esters, selenium powder and ArB(OH)₂, providing a facile entry to selenated isochromenones. This work highlights the use of selenium powder as a selenium reagent in the synthesis of selenated isochromenones for the first time.

We reported AgNO₃-catalyzed three-component reaction of alkynylaryl esters, selenium powder and ArB(OH)₂, providing an efficient synthetic route to selenated isochromenones.

Selenium-catalyzed oxidation of alkenes: insight into the mechanisms and developing trend

Recent progresses of the selenium-catalyzed oxidation of alkenes are summarized at the mechanism level. It may be beneficial for designing novel selenium-containing catalysts and alkene oxidation protocols for the next phase of studies.