Photoredox-Catalyzed Generation and Reactivity of α-Carbonyl Cationic Intermediates

Abstract

α-Carbonyl cationic intermediates have emerged as useful species for polarity-reversed functionalization of carbonyl compounds. Recent progress in photoredox catalysis has enabled their generation under mild conditions, especially from electrondeficient alkenes and related carbonyl substrates. This Review summarizes recent advances in the photoredox-catalyzed generation and synthetic transformations of α-carbonyl cationic intermediates. The discussion focuses on conceptual development of this field, mechanistic aspects of radical-polar crossover pathways, and representative reactivity patterns, including αnucleophilic fluorination and halogenation, fluoroalkylative inverse conjugate functionalization, nitrile trapping/Ritter-type amination, and remote difunctionalization. This Review aims to provide a concise overview of this rapidly developing area and to highlight future opportunities in α-carbonyl cation chemistry.