Intermolecular Dearomatization of Naphthalene Derivatives by Photoredox-Catalyzed 1,2-Hydroalkylation.

An intermolecular hydroalkylative dearomatization of naphthalenes with commercially available α-amino acids is achieved via visible-light photoredox catalysis. With an organic photocatalyst, a series of multi-substituted 1,2-dihydronaphthalenes are obtained in good-to-excellent yields. Intriguingly, by tuning the substituents at the C2 position of naphthalenes, formal dearomative [3+2] cycloadditions occur exclusively via a hydroalkylative dearomatization-cyclization sequence. This overall redox-neutral method features mild reaction conditions, good tolerance of functionalities, and operational simplicity. Diverse downstream elaborations of the products are demonstrated. Preliminary mechanistic studies suggest the involvement of a radical-radical coupling pathway.

Asymmetric Dearomatization of Indole Derivatives with N-Hydroxycarbamates Enabled by Photoredox Catalysis.

Dearomatization of indoles provides efficient synthetic routes for substituted indolines. In most cases, indoles serve as nucleophiles. Reported here is an asymmetric dearomatization reaction of indole derivatives that function as electrophiles. The combination of a photocatalyst and chiral phosphoric acid open to air unlocks the umpolung reactivity of indoles, enabling their dearomatization with N-hydroxycarbamates as nucleophiles. A variety of fused indolines bearing intriguing oxy-amines were constructed in excellent yields with moderate to high enantioselectivities. Mechanistic studies show that the realization of two sequential single-electron transfer oxidations of the indole derivatives is key, generating the configurationally biased carbocation species while providing the source of stereochemical induction. These results not only provide an efficient synthesis of enantioenriched indoline derivatives, but also offer a novel strategy for further designing asymmetric dearomatization reactions.

Glucose-sensitive colorimetric sensor based on peroxidase mimics activity of porphyrin-Fe3O4 nanocomposites.

5,10,15,20-Tetrakis(4-carboxyphenyl)-porphyrin-functionalized Fe3O4 nanocomposites (H2TCPP-Fe3O4) were successfully prepared by a simple two-step method. These nanocomposites exhibited ultra-high peroxidase-like activity compared with pure Fe3O4 nanoparticles. Colorless peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) was changed by H2O2 to its blue oxidized state. Kinetic studies indicated that the H2TCPP-Fe3O4 nanocomposites exhibited enhanced affinity toward H2O2 with a higher catalytic activity than Fe3O4 nanoparticles alone. Results of a fluorescent probe suggested that the catalase-mimic activity of the H2TCPP-Fe3O4 nanocomposites effectively catalyzed the decomposition of H2O2 into hydroxyl radicals. A simple, sensitive, and selective visual and colorimetric method with TMB as the substrate was designed to detect glucose when combined with glucose oxidase. This colorimetric method can be used for colorimetric detection of H2O2 with a minimum detection limit of 1.07×10(-6) M and a dynamic range of 5×10(-6) mol·L(-1) to 8×10(-5) mol·L(-1). This method can also be used to detect glucose at a minimum detection limit of 2.21×10(-6) M and a dynamic range of 25×10(-6) mol·L(-1) to 5×10(-6) mol·L(-1). Furthermore, the robustness of the nanocomposites makes them suitable for a wide range of applications in biomedicine and environmental chemistry fields.