Practical β-masked formylation and acetylation of electron-deficient olefins utilizing tetra(n-butyl)ammonium peroxydisulfate

Solvent-Controllable C-F Bond Activation for Masked Formylation of α-Trifluoromethyl Alkenes via Organo-Photoredox Catalysis

A solvent-controllable organo-photoredox-catalyzed C-F bond activation for masked formylation of α-trifluoromethyl alkenes with low-priced 1,3-dioxolane as masked formyl radical equivalent has been described. Consequently, a diversity of masked formylated gem-difluoroalkenes and monofluoroalkenes are constructed in moderate to high yields. This approach merits readily available starting materials, mild reaction conditions, and broad substrate scope. The feasibility of this approach has been highlighted by the one-pot masked formylation/hydrolysis sequence to form γ,γ-difluoroallylic aldehydes and late-stage modification of pharmaceutical and natural product derivatives.

Green synthesis and biological activities assessment of some new chromeno[2,3-b]pyridine derivatives

Magnetite nanoparticles (MNPs) composed of γ-Fe₂O₃ and hydroxyapatite (HAp) were modified by hexamethylen-1,6-diisocyanate (HMDI) followed by thiourea dioxide and used as recyclable catalyst for the synthesis of some newly derivatives of chromeno[2,3-b]pyridine. The products were synthesized in excellent yields via one-pot three-component reactions of 3-cyano-6-hydroxy-4-methyl-pyridin-2(1H)-one with aldehydes and dimedone under solvent-free conditions. The successful synthesis of products were confirmed using Fourier transform infrared (FTIR), proton/carbon nuclear magnetic resonance (¹H/¹³C NMR), and mass spectroscopies as well as physical data (e.g., melting points and elemental composition). The in vitro antioxidant and antifungal activities of the synthesized samples were evaluated using scavenging effects on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and potato dextrose agar (PDA) medium, respectively. Based on results, the chromeno[2,3-b]pyridine derivatives exhibited excellent biological activities that qualified them for biomedical applications.

Thermal electron-transfer-induced oxidation of 2-pyrazolines

Various 3,5-diaryl-1-phenyl-2-pyrazolines were synthesized, and their thermal oxidation to their corresponding 2-pyrazoles was investigated using tetrabutylammonium peroxydisulfate in acetonitrile solution. Compared to the reported oxidative methods, this oxidizing agent provides a clean and non-expensive oxidative reaction in a short reaction time. Based on the proposed reaction mechanism, the extent of co-planarity of the C₃-aryl ring toward C₃=N₂ double bond of the heterocyclic ring affects the electron-donating ability of the heterocyclic ring and decreases the time of oxidative reaction. The experimental results are supported by cyclic voltammetric measurements.

Site-Specific Functionalization of 1,3-Dioxolane with Imines: A Radical Chain Approach to Masked α-Amino Aldehydes

A thiol-promoted site-specific addition of 1,3-dioxolane to imines through a radical chain process is described. This process represents a metal-free and redox-neutral way to convert inexpensive materials to a broad range of protected α-amino aldehydes in good to excellent yields using only a catalytic amount of radical precursor. Control experiments revealed that both the thiol and a small amount of oxygen from air are indispensable to the success of this reaction.

Metal-free n-Et4NBr-catalyzed radical cyclization of disulfides and alkynes leading to benzothiophenes under mild conditions

The title reaction involves metal free TEAB-catalyzed S–S bond cleavage, C–S bond formation and C–C bond formation; it uses readily available disulfides and alkynes as substrates, and environmentally friendly TEAB as catalyst to synthesize useful benzothiophene derivatives.