ABSTRACT
A selective oxidative [4+2] annulation of alkenes with imidazo-fused heterocycles has been developed by using the synergistic combination of photoredox and cobaloxime catalysts. It allows facile access to various imidazole-fused polyaromatic scaffolds accompanied by H2 evolution. This protocol features high regioselectivity as well as a broad substrate scope. Detailed mechanistic studies indicate that twice the electron/H transfer processes facilitated by this catalytic system achieve the annulation π-extension of imidazo-fused heterocycles with alkenes.
ABSTRACT
New methylene blue (NMB), a phenothiazine dye, was covalently bonded to graphene oxide (GO) using glutaraldehyde as a crosslinking agent, which was characterized by spectroscopic techniques and electrochemistry. The obtained GO-NMB nanocomposite was used as interface material to construct a novel electrochemical sensor for the determination of hydrogen peroxide (H2O2). The electrochemical sensor based on GO-NMB nanocomposite exhibited excellent electrocatalytic activity for the reduction of hydrogen peroxide (H2O2), which was also enhanced by GO within the GO-NMB nanocomposite. With the optimized experimental conditions, the developed sensor showed high sensitivity (79.4 µA mM-1 cm-2) for electrocatalytic determination of H2O2 at the applied potential of -0.50 V in the concentration range of 0.000333 to 2.28 mΜ. The low limit of detection (1.35 µM), good reproducibility, and high stability of the sensor suggests that the electrochemical sensor based on the GO-NMB nanocomposite possesses obvious advantages, which paves a new avenue to functionalize GO for obtaining electrode interface materials.
ABSTRACT
An external oxidant-free C-H functionalization/C-O bond formation reaction for constructing benzo-3,4-coumarins accompanied by quantitative H2 evolution has been developed. High functional group tolerance and excellent reaction efficiency are shown in this transformation. Meanwhile, the substrates containing heterocyclic substituents such as thienyl-, pyridinyl-, and pyrrolylbenzoic acids displayed good performance. Importantly, this reaction can be performed with good efficiency on a gram scale. A cyclic voltammetry study and density functional theory calculations could provide insight into the mechanism of this reaction.
ABSTRACT
Visible-light-mediated formation of furans though direct oxidative [3+2] cycloaddition of 1,3-diones and alkynes is described. This protocol provides a simple and mild route to poly-substituted furans in moderate-to-good yields. Preliminary mechanistic studies suggest that this reaction likely follows a radical addition/cyclization pathway.
ABSTRACT
Selective carbon-carbon and carbon-heteroatom bond cleavage was achieved in a one reaction system. With this strategy a novel Pd/Cu-catalyzed aerobic oxidative oxosulfonation of olefins with DMSO has been developed. Preliminary mechanistic investigations indicated that CO/O2 assisted the bond cleavage and the leaving groups from the starting materials were trapped by O2 and underwent a hydroxylation process.
ABSTRACT
A simple palladium-catalysed oxidative cross-coupling between two different alcohols was developed. Various benzylic alcohols could couple with aliphatic alcohols in excellent yields. The use of benzyl chloride as the oxidant and the amount of aliphatic alcohol were both important for achieving the reaction selectivity.
ABSTRACT
A direct oxidative cross-coupling between terminal alkynes and secondary phosphine oxides was developed. This approach provides an efficient way to construct alkynyl di(phenyl) phosphine oxides from basic materials, and in this process, the silver salts act as a key promoter.
