Photoredox-catalyzed generation and reactivity of α-carbonyl cationic intermediates

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 electron-deficient 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 α-nucleophilic 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.