Trifluoromethylselenolation of Aryldiazonium Salts: A Mild and Convenient Copper-Catalyzed Procedure for the Introduction of the SeCF3Group

Recent investigations into deborylative (thio-/seleno-) cyanation of aryl boronic acids

In this review, we intend to summarize the most important discoveries in the deborylative (thio-/seleno-) cyanation of aryl boronic acids from 2006 to the end of 2023. Thus, the review is divided into three parts. The first section focuses exclusively on cyanation of aryl boronic acids into aryl nitriles. The second section covers the available literature on the synthesis of aryl thiocyanates through thiocyanation of respective aryl boronic acids. The third will discuss selenocyanation of aryl boronic acids into aryl selenocyanates.

Base-Catalyzed One-Pot Synthesis of Selenosulfides: A Base Basicity-Controlled Approach

We developed a novel and efficient sequential one-pot synthesis of selenosulfides via a base-catalyzed methodology utilizing readily available starting compounds, under mild reaction conditions. This method eliminated the need for excess oxidants or additives and simplified the synthesis procedure. Furthermore, organic amine bases served as exceptional catalysts for synthesizing the target products. The performance of a catalytic system depends on the basicity of the bases. The selection of suitable bases, based on their pKaH values, is crucial for the selective synthesis of selenosulfides without the formation of byproducts. This method provides a direct route for the preparation of selenosulfides, which are important scaffolds in organic chemistry.

Synthesis of Selenocyanates and Selenoethers of Amino Pyrazoles and Amino Uracils by In Situ Triselenium Dicyanide from Malononitrile and Selenium Dioxide

Herein, we report an efficient method for synthesis of novel selenocyanates of amino pyrazole, amino uracil, and amino isoxazole derivatives using in situ triselenium dicyanide from the combination of malononitrile and selenium dioxide in DMSO medium. Using the same combination but changing the stoichiometry of reagents and sequence of addition and temperature, symmetrical selenoethers of amino pyrazoles and amino uracils were prepared in good yields. Furthermore, selenocyanates of amino pyrazoles were utilized for the synthesis of corresponding alkynyl selenides in the presence of CuI and Cs₂CO₃. The salient features of this methodology are inexpensive starting materials, short reaction time, and good to very good yields. This method is also applicable for the gram-scale synthesis of selenocyanates of amino pyrazoles and amino uracils.

Paired Electrolysis Enabled Cyanation of Diaryl Diselenides with KSCN Leading to Aryl Selenocyanates

The first example of paired electrolysis-enabled cyanation of diaryl diselenides, with KSCN as the green cyanating agent, has been developed. A broad range of aryl selenocyanates can be efficiently synthesized under chemical-oxidant- and additive-free, energy-saving and mild conditions.

Topochemical, Single-Crystal-to-Single-Crystal [2+2] Photocycloadditions Driven by Chalcogen-Bonding Interactions

The face-to-face association of (E)-1,2-di(4-pyridyl)ethylene (bpen) molecules into rectangular motifs stabilized for the first time by chalcogen bonding (ChB) interactions is shown to provide photoreactive systems leading to cyclobutane formation through single-crystal-to-single-crystal [2+2] photodimerizations. The chelating chalcogen bond donors are based on original aromatic, ortho-substituted bis(selenocyanato)benzene derivatives 1-3, prepared from ortho-diboronic acid bis(pinacol) ester precursors and SeO2 and malononitrile in 75-90 % yield. The very short intramolecular Se⋅⋅⋅Se distance in 1-3 (3.22-3.24 Å), a consequence of a strong intramolecular ChB interaction, expands to 3.52-3.54 Å in the chalcogen-bonded adducts with bpen, a distance (<4 Å) well adapted to the face-to-face association of the bpen molecules into the reactive position toward photochemical dimerization.

Nucleophilic Substitution of Selenosulfonates with Me3SiCF2Br: Facile and Efficient Access to Bromodifluoromethylated Selenides under Metal-Free Conditions

A facile synthesis of bromodifluoromethylated selenides under metal-free conditions is described here. Commercially available Me₃SiCF₂Br and bench-stable selenosulfonates react smoothly to give a broad scope of alkyl- and aryl-substituted bromodifluoromethylated selenides in moderate to good yields via a difluorocarbene intermediate. This protocol features a short reaction time, the absence of toxic waste, good scalability, and successful late-stage modification of bioactive molecules. In addition, the title products can be easily converted to different fluorinated and ¹⁸F-labeled selenides.

Recent trends in the chemistry of Sandmeyer reaction: a review

Metal-catalyzed reactions play a vital part to construct a variety of pharmaceutically important scaffolds from past few decades. To carry out these reactions under mild conditions with low-cost easily available precursors, various new methodologies have been reported day by day. Sandmeyer reaction is one of these, first discovered by Sandmeyer in 1884. It is a well-known reaction mainly used for the conversion of an aryl amine to an aryl halide in the presence of Cu(I) halide via formation of diazonium salt intermediate. This reaction can be processed with or without copper catalysts for the formation of C-X (X = Cl, Br, I, etc.), C-CF₃/CF₂, C-CN, C-S, etc., linkages. As a result, corresponding aryl halides, trifluoromethylated compounds, aryl nitriles and aryl thioethers can be obtained which are effectively used for the construction of biologically active compounds. This review article discloses various literature reports about Sandmeyer-related transformations developed during 2000-2021 which give different ideas to synthetic chemists about further development of new and efficient protocols for Sandmeyer reaction. An updated compilation of new approaches for Sandmeyer reaction is described in this review to construct a variety of carbon-halogen, carbon-phosphorous, carbon-sulfur, carbon-boron etc. linkages.

Progress and recent trends in the direct selenocyanation of (hetero)aromatic C-H bonds

This review covers recent advances in the direct selenocyanation of (hetero)aromatic C-H bonds with an emphasis on the reaction mechanisms. This novel approach is an effective means of preparing a variety of aromatic and heteroaromatic selenocyanates, which are extremely versatile synthetic precursors of selenium-containing compounds, such as selenols, seleninic acids, selenides, diselenides, and trifluoromethyl selenides.

New organoselenides (NSAIDs-Se derivatives) as potential anticancer agents: Synthesis, biological evaluation and in silico calculations

Herein we reported the synthesis of twenty new organoselenium compounds (2a-2j and 3a-3j) based on the hybridization of nonsteroidal antiinflammatory drugs (NSAIDs) skeleton and organoselenium motif (-SeCN and -SeCF₃), the anticancer activity was evaluated against four types of cancer cell lines, Caco-2 (human colon adenocarcinoma cells), BGC-823 (human gastric cancer cells), MCF-7 (human breast adenocarcinoma cells), PC-3 (human prostatic cancer cells). Interestingly, the introduction of the -SeCN or -SeCF₃ moiety in corresponding parent NSAIDs results in the significant effect on cancer cell lines. Moreover, the most active compound 3a showed IC₅₀ values lower than 5 μM against the four cancer cell lines, particularly to BGC-823 and MCF-7 with IC₅₀ values of 2.5 and 2.7 μM, respectively. Furthermore, three compounds 3a, 3g and 3i were selected to investigate their ability to induce apoptosis in BGC-823 cells via modulating the expression of anti-apoptotic Bcl-2 protein, pro-inflammatory cytokines (IL-2) and proapoptotic caspase-8 protein. The redox properties of the NSAIDs-Se derivatives prepared herein were conducted by 2, 2-didiphenyl-1-picrylhydrazyl (DPPH), bleomycin dependent DNA damage and glutathione peroxidase (GPx)-like assays. Finally, molecular docking study revealed that an interaction with the active site of thioredoxin reductase 1 (TrxR1) and predicted the anticancer activity of the synthesized candidates. Overall, these results could serve a promising launch point for further design of NSAIDs-Se derivatives as potential anticancer agents.

Synthesis and biological evaluation of organoselenium (NSAIDs-SeCN and SeCF3) derivatives as potential anticancer agents

A series of organoselenium compounds based on the hybridization of nonsteroidal antiinflammatory drugs (NSAIDs) scaffolds and Se functionalities (-SeCN and -SeCF₃) were synthesized and characterized, and evaluated against four types of cancer cell lines, SW480 (human colon adenocarcinoma cells), HeLa (human cervical cancer cells), A549 (human lung carcinoma cells), MCF-7 (human breast adenocarcinoma cells). Interestingly, most of the investigated compounds showed active in reducing the viability of different cancer cell lines. The most active compound 3h showed IC₅₀ values lower than 20 μM against the four cancer cell lines, particularly to SW480 and MCF-7 with IC 50 values of 4.9 and 3.4 μM, respectively. Furthermore, NSAIDs-SeCN derivatives (2h and 2i) and NSAIDs-SeCF₃ derivatives (3h and 3i) were selected to investigate their ability to induce apoptosis in MCF-7 cells via modulation the expression of anti-apoptotic Bcl-2 protein, pro-inflammatory cytokines (IL-2) and proapoptotic caspase-3 protein. Moreover, the redox properties of the synthesized organoselenium candidates were conducted by 2, 2-didiphenyl-1-picrylhydrazyl (DPPH), bleomycin dependent DNA damage and glutathione peroxidase (GPx)-like assays. Taken together, these NSAIDs-Se candidates could provide promising new lead derivatives for further potential anticancer drug development.

Copper-promoted/copper-catalyzed trifluoromethylselenolation reactions

Copper catalysis and, more generally, copper chemistry are pivotal for modern organofluorine chemistry. Major advances have been made in the field of trifluoromethylselenolations of organic compounds where copper catalysis played a crucial role. Recent developments in this field are highlighted in this minireview.

NCS-promoted thiocyanation and selenocyanation of pyrrolo[1,2-a]quinoxalines

An efficient NCS-promoted thiocyanation of pyrrolo[1,2-a]quinoxalines with NH₄SCN or KSCN was developed. Moreover, in the presence of KSeCN, the selenocyanation of pyrrolo[1,2-a]quinoxalines was also achieved.

Trifluoromethyl-substituted selenium ylide: a broadly applicable electrophilic trifluoromethylating reagent

An easily available, air/moisture insensitive and broadly applicable electrophilic reagent trifluoromethyl-substituted selenium ylide 1a and its reactions with a variety of nucleophiles including β-ketoesters and silyl enol ethers, aryl/heteroaryl boronic acids, electron-rich heteroarenes and sulfinates were described.

Difluorocarbene-derived trifluoromethylselenolation of benzyl halides

Cu-Promoted difluorocarbene-derived trifluoromethylselenolation of benzyl halides with the Ph₃P⁺CF₂CO₂⁻/S_e/F⁻ system is described.

Divergent Reactivity of a Dinuclear (NHC)Nickel(I) Catalyst versus Nickel(0) Enables Chemoselective Trifluoromethylselenolation

We herein showcase the ability of NHC-coordinated dinuclear NiI -NiI complexes to override fundamental reactivity limits of mononuclear (NHC)Ni0 catalysts in cross-couplings. This is demonstrated with the development of a chemoselective trifluoromethylselenolation of aryl iodides catalyzed by a NiI dimer. A novel SeCF3 -bridged NiI dimer was isolated and shown to selectively react with Ar-I bonds. Our computational and experimental reactivity data suggest dinuclear NiI catalysis to be operative. The corresponding Ni0 species, on the other hand, suffers from preferred reaction with the product, ArSeCF3 , over productive cross-coupling and is hence inactive.

Electrophilic Trifluoromethylselenolation of Boronic Acids

Trifluoromethylselenylated compounds are emergent compounds with interesting physicochemical properties that still suffer from a lack of efficient synthetic methods. We recently developed an efficient one-pot strategy to generate in situ CF₃SeCl and use it in various reactions. Herein, we continue our study of the reactivity scope of this preformed reagent. Cross-coupling reactions with aromatic and heteroaromatic boronic acids have been investigated. The expected products have been obtained, using a stoichiometric amount of copper, with moderate yields.

Benzyltrifluoromethyl (or Fluoroalkyl) Selenide: Reagent for Electrophilic Trifluoromethyl (or Fluoroalkyl) Selenolation

Trifluoromethylseleno substituent (CF3Se) is an emerging group, but its direct introduction onto organic molecules is still quite limited and mainly restricted to nucleophilic methods. Herein, we describe a new approach to easily and safely perform electrophilic trifluoromethylselenolation starting from a simple and easily accessible reagent, namely, benzyltrifluoromethyl selenide. This strategy can be generalized to various fluoroalkylselanyl groups, even functionalized ones.

Dehydrogenative [2 + 2 + 1] Heteroannulation Using a Methyl Group as a One-Carbon Unit: Access to Pyrazolo[3,4-c]quinolines

A practical and straightforward access to pyrazolo[3,4-c]quinolines by molecular sieve mediated dehydrogenative [2 + 2 + 1] heteroannulation of N-(o-alkenylaryl)imines with aryldiazonium salts is described using a sp(3)-hybrid carbon atom as a one-carbon unit. The reaction enables the formation of three new chemical bonds, a C-C bond and two C-N bonds, in a single reaction and features simple operation and excellent functional group tolerance.

Expeditious trifluoromethylthiolation and trifluoromethylselenolation of alkynyl(phenyl)iodoniums by [XCF3]− (X = S, Se) anions

Metal- and additive-free trifluoromethylthiolation and trifluoromethylselenolation of alkynyl(phenyl)iodoniums by [XCF₃]⁻ (X = S, Se) anions was accomplished in 5–10 minutes.