Highly Diastereoselective Synthesis of Dihydro-benzoimidazo-[1,3]-thiazines via Electro-oxidative Selenocyclization of Thioallyl Benzoimidazoles

Electrochemically chalcogenative annulation enabled construction of functionalized saturated N-heterocycles

An efficient chalcogenative annulation strategy for constructing functionalized saturated N-heterocycles from unactivated alkenes with dichalcogenides under electrochemical conditions has been presented. This protocol is applicable to mono-, di- or tri-substituted alkenes, providing a straightforward pathway to aziridines, azetidines, pyrrolidines, and piperidines with high regioselectivity. Moreover, the strategy is qualified to realize the oxychalcogenation of alkenes as well.

Electrosynthesis of Cyclic Isoureas and Ureas Through Contiguous Heterofunctionalizations

An efficient synthetic protocol for the selenylated cyclic isoureas was developed using electrochemical activation of diselenides. This sustainable approach permitted transition metal and chemical oxidant-free difunctionalization of olefins and overall access to distinct 1,2,3 triheterofunctionalized carbon skeletons. Excellent functional group tolerance was noticed, allowing the synthesis of a series of cyclic isourea derivatives. In addition, an acid-triggered skeletal isomerization facilitated the synthesis of cyclic urea derivatives from the corresponding cyclic isoureas. Mechanistic investigations, along with voltammetric studies, enabled the postulation of the reaction mechanism.

Recent Progress in Synthetic and Biological Application of Diorganyl Diselenides

Diorganyl diselenides have emerged as privileged structures because they are easy to prepare, have distinct reactivity, and have broad biological activity. They have also been used in the synthesis of natural products as an electrophile in the organoselenylation of aromatic systems and peptides, reductions of alkenes, and nucleophilic substitution. This review summarizes the advancements in methods for the transformations promoted by diorganyl diselenides in the main functions of organic chemistry. Parallel, it will also describe the main findings on pharmacology and toxicology of diorganyl diselenides, emphasizing anti-inflammatory, hypoglycemic, chemotherapeutic, and antimicrobial activities. Therefore, an examination detailing the reactivity and biological characteristics of diorganyl diselenides provides valuable insights for academic researchers and industrial professionals.

In vitro and in vivo anti-pigmentation effects of 2-mercaptobenzimidazoles as nanomolar tyrosinase inhibitors on mammalian cells and zebrafish embryos: Preparation of pigment-free zebrafish embryos

Recently, 10 2-mercaptobenzo[d]imidazole (2-MBI) compounds (1-10) were synthesized. Although all 2-MBI compounds are tyrosinase inhibitors that inhibit mushroom tyrosinase at extremely low concentrations (IC50 values: 20-740 nM) and effectively inhibit the browning of apples, to our knowledge, no studies have determined whether 2-MBI compounds inhibit mammalian tyrosinase. Mammalian tyrosinase is different from mushroom tyrosinase in its distribution within the cell and has structural characteristics that are different from mushroom tyrosinase in amino acid sequence and in the presence of a quaternary structure. Thus, the effect of the 10 2-MBI compounds on mammalian tyrosinase activity was investigated in B16F10 cells. Six compounds (1-6) exhibited stronger intracellular tyrosinase inhibition than that of kojic acid and phenylthiourea (PTU), which are known to be the most potent tyrosinase inhibitors; their strong tyrosinase inhibitory activity robustly inhibited intracellular melanin production in B16F10 cells. None of the tested 2-MBI compounds exhibited appreciable cytotoxicity in HaCaT and B16F10 cells. To confirm the anti-melanogenic efficacy of the 2-MBI compounds in vivo, a zebrafish embryo model was used. At concentrations 100 times lower than kojic acid, most 2-MBI compounds demonstrated much stronger depigmentation efficacy than that of kojic acid, and three 2-MBI compounds (2-4) showed depigmentation activity similar to or more potent than that of PTU, resulting in nearly pigment-free zebrafish embryos. These results suggest that 2-MBI compounds may be potential therapeutic agents for hyperpigmentation-related disorders.

Electro-oxidative Synthesis of Unsymmetrical Alkyne-1,4-diones via Sequential Ring Formation and Cleavage

Synthesis of unsymmetrical but-2-yne-1,4-diones is reported through oxidative alkyne translocation of readily accessible homopropargylic alcohols. The developed method consists of an unprecedented one-pot sequential electro-oxidative annulation-fragmentation-chemical selenoxide elimination process. Excellent functional group compatibility was observed, and an array of yne-1,4-diones were synthesized. Derivatization of the alkyne gave access to other valuable scaffolds. Detailed mechanistic studies through the isolation of key intermediates clarified the cascade transformation.

DBU-Promoted Deaminative Thiolation of 1H-Benzo[d]imidazol-2-amines and Benzo[d]oxazol-2-amines

A facile and efficient catalyst-/metal-/oxidant-free DBU-promoted deaminative thiolation reaction of 1H-benzo[d]imidazol-2-amines and benzo[d]oxazol-2-amines has been developed at room temperature conditions in a one-pot protocol. This practical three-component strategy represents a novel and environmentally friendly reaction pathway toward the straightforward synthesis of various 2-thio-1H-benzo[d]imidazoles and 2-thiobenzo[d]oxazoles using carbon disulfide as a sulfur source through C-N bond cleavage and C-S bond formation process. Different types of 1H-benzo[d]imidazol-2-amines, benzo[d]oxazol-2-amines, and organic bromides are suitable substrates. The gram-scale and late-stage modification experiments provide the potential applications based on this methodology in the field of organic and medicinal chemistry.

Regio- and stereoselective electrochemical selenoalkylation of alkynes with 1,3-dicarbonyl compounds and diselenides

A regio- and stereoselective electrochemical approach for the selenoalkylation of alkynes with 1,3-dicarbonyl compounds and diselenides has been developed.