Synthesis of Azanucleosides by Anodic Oxidation in a Lithium Perchlorate-Nitroalkane Medium and Diversification at the 4′-Nitrogen Position

Photoinduced α-C-H Amination of Cyclic Amine Scaffolds Enabled by Polar-Radical Relay

Herein, we report a polar-radical relay strategy for α-C-H amination of cyclic amines with N-chloro-N-sodio-carbamates. The relay is initiated by in situ generation of cyclic iminium intermediate using N-iodosuccinimide (NIS) oxidant as an initiator, which then operates through a series of polar (addition and elimination) and radical (homolysis, hydrogen- and halogen atom transfer) reactions to enable the challenging C-N bond formation in a controlled manner. A broad range of α-amino cyclic amines were readily accessed with excellent regioselectivity, and the superb applicability was further demonstrated by functionalization of biologically relevant compounds.

Synthesis of Ribo-Azanucleosides by Anodic Oxidation: Reactivity Control of Intermediate for Efficient Access to Pharmacophores

Azanucleosides, the sugar-modified nucleoside analogues, have various biological activities, while their efficient synthetic strategy is still under development. Herein, a novel method for the synthesis of pharmaceutically relevant azanucleosides, β-anomers of ribo-azanucleosides, by means of site-specific anodic C-H activation by using a nitroalkane-lithium perchlorate medium is reported. A mechanistic study of the electrochemical reaction and the armed/disarmed concept from traditional glycochemistry revealed that the 2'-substituent has a significant effect on the reactivity of prolinol derivative, and suitable carboxylic acid additives can control the reactivity of the intermediate species, an iminium cation equivalent. Finally, this method was demonstrated to be applicable for the synthesis of β-anomers of ribo-azanucleosides with all four nucleobases in a stereoselective manner.

Selective Functionalization of Styrenes with Oxygen Using Different Electrode Materials: Olefin Cleavage and Synthesis of Tetrahydrofuran Derivatives

Electrode materials can have a significant impact on the course of an electrolysis reaction. Of particular interest is that different electrodes can generate different products from the same substrate. The electrode-material-selective transformations of styrene derivatives with molecular oxygen are reported. Platinum electrodes afford carbonyl products via cleavage of olefins, whereas tetrahydrofuran formation is achieved with carbon electrodes. A variety of different styrenes are available for both reactions. Electrolysis allows straightforward and mild chemical conversions that are metal- and oxidant-free. Electrochemical measurements illuminate the different effects of platinum and carbon electrodes on styrenes. The key to the differing reactions is probably that the oxidation potentials of the substrates are lower (higher HOMO energy) on carbon electrodes than on platinum electrodes. The adsorption of the substrates on carbon electrodes can also promote tetrahydrofuran formation.