Electrosynthesis of 3-alkyl, 3‑hydroxy isoindolin-1-ones enabled by metal-free redox catalysis and enhanced by rapid alternating polarity (rAP)

• Aromatic carbonyl radical anions act as catalytic reducing species and coupling partners. • Alternating current (AC) outperforms Direct current (DC) in radical coupling reaction. • Mild reduction and oxidation potentials obtained during AC electrolysis limit decomposition. • Oxidation of bromide released during the reaction serves as a sacrificial reductant. In this work, an electrosynthetic cross-coupling reaction is presented between the carbonyl group of N -(aryl)phthalimide and benzyl/allyl bromides that produces 3-alkyl, 3-hydroxy isoindolin-1-ones. The reaction proceeds via homogeneous reductive catalytic activation of the bromo-compound using N -(aryl)phthalimides as a mediator and rapid alternating polarity ( r AP) electrolysis; the latter technique permits a more efficient use of the alkyl halide. It is detailed how the reaction was optimized, while citing general trends observed when working with rAP. Voltammetric exploration shows that bromide ion release from the catalytic coupling feeds the counter-electrode reaction, protecting the product from decomposition. These conditions may be extrapolated to carbonyls in general to produce tertiary alcohols as well. Finally, exploration of the reaction scope enabled us to apply the developed reaction to the synthesis of 18 examples of 3-alkyl, 3-hydroxy isoindolin-1-one derivatives and other tertiary alcohols in moderate to good yields at room temperature using carbon-based electrodes, without sub-zero temperatures, metals or unstable reagents.