Palladium(II)-catalyzed switchable mono-/diselenylation of arenes controlled by solvent effects

Recent advances in selective mono-/dichalcogenation and exclusive dichalcogenation of C(sp2)-H and C(sp3)-H bonds

Organochalcogen compounds are prevalent in numerous natural products, pharmaceuticals, agrochemicals, polymers, biological molecules and synthetic intermediates. Direct chalcogenation of C-H bonds has evolved as a step- and atom-economical method for the synthesis of chalcogen-bearing compounds. Nevertheless, direct C-H chalcogenation severely lags behind C-C, C-N and C-O bond formations. Moreover, compared with the C-H monochalcogenation, reports of selective mono-/dichalcogenation and exclusive dichalcogenation of C-H bonds are relatively scarce. The past decade has witnessed significant advancements in selective mono-/dichalcogenation and exclusive dichalcogenation of various C(sp2)-H and C(sp3)-H bonds via transition-metal-catalyzed/mediated, photocatalytic, electrochemical or metal-free approaches. In light of the significance of both mono- and dichalcogen-containing compounds in various fields of chemical science and the critical issue of chemoselectivity in organic synthesis, the present review systematically summarizes the advances in these research fields, with a special focus on elucidating scopes and mechanistic aspects. Moreover, the synthetic limitations, applications of some of these processes, the current challenges and our own perspectives on these highly active research fields are also discussed. Based on the substrate types and C-H bonds being chalcogenated, the present review is organized into four sections: (1) transition-metal-catalyzed/mediated chelation-assisted selective C-H mono-/dichalcogenation or exclusive dichalcogenation of (hetero)arenes; (2) directing group-free selective C-H mono-/dichalcogenation or exclusive dichalcogenation of electron-rich (hetero)arenes; (3) C(sp3)-H dichalcogenation; (4) dichalcogenation of both C(sp2)-H and C(sp3)-H bonds. We believe the present review will serve as an invaluable resource for future innovations and drug discovery.

Chelation-assisted transition metal-catalysed C–H chalcogenylations

This review summarizes recent advances in C–S and C–Se formationsviatransition metal-catalyzed C–H functionalization utilizing directing groups to control the site-selectivity.

Transition metal catalysed direct selanylation of arenes and heteroarenes

Transition metal catalysed C-H functionalization has reached an exciting level of sophistication, and, today, it represents a paradigm shift from the standard logic of synthetic chemistry. The direct conversion of C-H bonds into C-heteroatoms remains, however, a critical challenge. Nowadays, there is a great demand in general synthetic chemistry in, for example, the materials science for the development of straightforward C-Se bond formation, in order to fulfil the practical requirements. In this sense, this review summarizes recent outstanding advances in the C-Se bond formation through transition metal-catalysed direct selanylation, providing new insights into their mechanistic aspects and disclosing effective synthetic routes with high atom economy. In addition, this review intends to show the growing opportunities to construct complex chemical scaffolds containing selenium atoms.

Selenium and Tellurium Electrophiles in Organic Synthesis

This chapter highlights the utility of electrophilic achiral and chiral organoselenium reagents in organic synthesis. A range of reactions from alkene functionalizations, the functionalization of aliphatic and aromatic C–H bonds using stoichiometric and catalytic approaches as well as rearrangement reactions are described. In addition, the utility of organotellurium reagents in organic synthesis is covered in this chapter.

Copper-catalyzed diarylation of Se with aryl iodides and heterocycles

The site-selective copper-catalyzed three-component coupling reaction of electron-deficient heterocycles, Se powder and aryl iodides is disclosed, providing an efficient and practical pathway to access 2-arylselenated heterocycles.