Transition-Metal-Free HFIP-Mediated Organo Chalcogenylation of Arenes/Indoles with Thio-/Selenocyanates

Synthesis, Characterization, and DFT Studies of NHC-Derived Amide-Functionalized Organoselenium Compounds

The NHC-Se scaffold has emerged as an intriguing target, opening new avenues for discovering compounds that could significantly improve public health. Recently, extensive efforts have been made to synthesize NHC-Se-based organic compounds for various biomedical applications. Herein, we disclose a straightforward method to access a series of new N-heterocyclic carbene (NHC)-derived organoselenium molecules functionalized with an amide moiety. The parent NHC-Se adduct with a pendent ester moiety is sufficiently activated to facilitate a base- and additive-free ester-to-amide bond transformation. Furthermore, the use of PEG 3550, a biocompatible solvent, enhances reaction efficiency and simplifies the workup. This approach employs a broad spectrum of aliphatic amines with good functional group tolerance, offering a versatile and ecofriendly method for extending chemical space around organoselenium compounds. Additionally, density functional theory (DFT) calculations provide insights into the electronic properties, stability, and reactivity profiles of the synthesized compounds, suggesting their promising potential for applications in biomedical fields.

FeCl3-catalyzed oxidative diselenylation of pyrrole-tethered indoles

A mild and efficient FeCl3-catalyzed oxidative diselenylation of pyrrole-tethered indoles has been achieved by using RSeSeR as the source of selenium and m-chloroperoxybenzoic acid (mCPBA) as the oxidant (17-70% yields). In addition, this selenylation reaction system can be expanded to the functionalization of tryptophan derivatives and melatonin at the C-2 position of the indole moiety (55-58% yields).

Design, synthesis, and bioactivity evaluation of novel indole-selenide derivatives as P-glycoprotein inhibitors against multi-drug resistance in MCF-7/ADR cell

The inhibition of P-glycoprotein (P-gp) has emerged as an intriguing strategy for circumventing multidrug resistance (MDR) in anticancer chemotherapy. In this study, we have designed and synthesized 30 indole-selenides as a new class of P-gp inhibitors based on the scaffold hopping strategy. Among them, the preferred compound H27 showed slightly stronger reversal activity (reversal fold: 271.7 vs 261.6) but weaker cytotoxicity (inhibition ratio: 33.7% vs 45.1%) than the third-generation P-gp inhibitor tariquidar on the tested MCF-7/ADR cells. Rh123 accumulation experiments and Western blot analysis demonstrated that H27 displayed excellent MDR reversal activity by dose-dependently inhibiting the efflux function of P-gp rather than its expression. Besides, UIC-2 reactivity shift assay revealed that H27 could bind to P-gp directly and induced a conformation change of P-gp. Moreover, docking study revealed that H27 matched well in the active pockets of P-gp by forming some key H-bonding interactions, arene-H interactions and hydrophobic contacts. These results suggested that H27 is worth to be a starting point for the development of novel Se-containing P-gp inhibitors for clinic use.

Mechanochemical synthesis of organoselenium compounds

We disclose herein a strategy for the rapid synthesis of versatile organoselenium compounds under mild conditions. In this work, magnesium-based selenium nucleophiles are formed in situ from easily available organic halides, magnesium metal, and elemental selenium via mechanical stimulation. This process occurs under liquid-assisted grinding (LAG) conditions, requires no complicated pre-activation procedures, and operates broadly across a diverse range of aryl, heteroaryl, and alkyl substrates. In this work, symmetrical diselenides are efficiently obtained after work-up in the air, while one-pot nucleophilic addition reactions with various electrophiles allow the comprehensive synthesis of unsymmetrical monoselenides with high functional group tolerance. Notably, the method is applied to regioselective selenylation reactions of diiodoarenes and polyaromatic aryl halides that are difficult to operate via solution approaches. Besides selenium, elemental sulfur and tellurium are also competent in this process, which showcases the potential of the methodology for the facile synthesis of organochalcogen compounds.

Visible Light and Triselenium Dicyanide (TSD): New Horizons in the Synthesis of Organic Selenocyanates

Herein, we describe a new method for the synthesis of α-carbonyl selenocyanates by reacting triselenium dicyanide (TSD) and styrenes under blue light irradiation and O2 atmosphere. The reactions are triggered by the formation of Se-centered radical species, followed by the addition/oxidation of the styrene π-bond. α-Carbonyl selenocyanates and α-hydroxy selenocyanates were obtained in moderate to excellent yields from aryl- and alkyl-substituted alkenes, respectively. It was demonstrated that α-carbonyl selenocyanates could be used as a synthetic platform in a multicomponent reaction strategy to prepare 2-phenylimidazo[1,2-a]pyridine derivatives, which were evaluated for their photophysical properties. Overall, this new method provides a useful tool for synthesizing α-carbonyl selenocyanates, and demonstrates their potential for use in the synthesis of other compounds, thus giving new synthetic opportunities to construct organic selenocyanate compounds.

Organoselenium Compounds: Chemistry and Applications in Organic Synthesis

Selenium, originally described as a toxin, turns out to be a crucial trace element for life that appears as selenocysteine and its dimer, selenocystine. From the point of view of drug developments, selenium-containing drugs are isosteres of sulfur and oxygen with the advantage that the presence of the selenium atom confers antioxidant properties and high lipophilicity, which would increase cell membrane permeation leading to better oral bioavailability. In this article, we have focused on the relevant features of the selenium atom, above all, the corresponding synthetic approaches to access a variety of organoselenium molecules along with the proposed reaction mechanisms. The preparation and biological properties of selenosugars, including selenoglycosides, selenonucleosides, selenopeptides, and other selenium-containing compounds will be treated. We have attempted to condense the most important aspects and interesting examples of the chemistry of selenium into a single article.

Metal-free and atom-efficient protocol for diarylation of selenocyanate by diaryliodonium salts

We developed an atom- and reaction mass efficient strategy for the preparation of diarylselenides using iodonium salts as reactants. The developed approach allows the obtaining of diarylselenides from the corresponding trimethoxyphenyl-substituted iodonium salts via a two-step one-pot reaction sequence. The proposed metal-free methodology is based on the involvement of both iodonium aryl groups for diarylation.

Site-selective C5-H and N-H alkylation of unprotected 8-aminoquinolines

8-Aminoquinolines are the building blocks of many pharmaceutical compounds, which has motivated the scientific community to develop new ways to derivatize these compounds. In this work, we performed a site-selective C5-H and N-H alkylation of 8-aminoquinolines using para-quinone methides under extremely mild conditions. C5-H alkylation was performed using protecting group-free 8-aminoquinolines and in metal-free conditions. N-H alkylations were also carried out under mild conditions. All corresponding alkylation products were obtained in high to excellent yields.