Wen Zhang

The cross-electrophile dialkylation of alkenes enables the formation of two C(sp³)-C(sp³) bonds from readily available starting materials in a single transformation, thereby providing a modular and expedient approach to building structural complexity in organic synthesis. Herein, we exploit the disparate electronic and steric properties of alkyl halides with varying degrees of substitution to accomplish their selective activation and addition to alkenes under electrochemical conditions. This method enables regioselective dialkylation of alkenes without the use of a transition-metal catalyst and provides access to a diverse range of synthetically useful compounds.

This Viewpoint outlines our recent contribution in electroreductive synthesis. Specifically, we leveraged deeply reducing potentials provided by electrochemistry to generate radical and anionic intermediates from readily available alkyl halides and chlorosilanes. Harnessing the distinct reactivities of radicals and anions, we have achieved several challenging transformations to construct C-C, C-Si, and Si-Si bonds. We highlight the mechanistic design principle that underpinned the development of each transformation and provide a view forward on future opportunities in growing area of reductive electrosynthesis.

Pyridines and related N-heteroarenes are commonly found in pharmaceuticals, agrochemicals and other biologically active compounds^1,2. Site-selective C–H functionalization would provide a direct way of making these medicinally active products^3,4,5. For example, nicotinic acid derivatives could be made by C–H carboxylation, but this remains an elusive transformation^6,7,8. Here we describe the development of an electrochemical strategy for the direct carboxylation of pyridines using CO₂. The choice of the electrolysis setup gives rise to divergent site selectivity: a divided electrochemical cell leads to C5 carboxylation, whereas an undivided cell promotes C4 carboxylation. The undivided-cell reaction is proposed to operate through a paired-electrolysis mechanism^9,10, in which both cathodic and anodic events play critical roles in altering the site selectivity. Specifically, anodically generated iodine preferentially reacts with a key radical anion intermediate in the C4-carboxylation pathway through hydrogen-atom transfer, thus diverting the reaction selectivity by means of the Curtin–Hammett principle¹¹. The scope of the transformation was expanded to a wide range of N-heteroarenes, including bipyridines and terpyridines, pyrimidines, pyrazines and quinolines.

A series of novel nitroxyl radical hindered-amine light stabilizer monomers were designed and synthesized from 2,2,6,6-tetramethylpiperidine- N -oxyl-4-ol, cyanuric chloride, allylamine, and 2-hydroxyphenylbenzotriazole derivatives. Structures of the new stabilizers were confirmed by ¹ H NMR, ¹³ C NMR, FT-IR, ESI-HRMS, and element analysis. The synthesized compounds 5a–f were evaluated for their antioxidant and antiaging properties, and a significant stabilizing effect against photodegradation was found.