Photocatalytic Multicomponent Reactions: A Review of Recent Developments (2018–2025)

Photocatalytic multicomponent reactions (PC‐MCRs) have emerged as a transformative platform for the rapid assembly of structural complexity from simple precursors, perfectly aligning with the principles of green chemistry. This review provides a comprehensive update on the significant developments in this field from 2018 to 2025. Beyond a systematic overview of three‐, four‐, and pseudofive‐component strategies, we critically examine the evolution of activation modes—ranging from single electron transfer (SET, a process involving the transfer of one electron between molecules to generate reactive radical intermediates) and hydrogen atom transfer (HAT, a concerted transfer of a proton and an electron to cleave inert CH bonds) to energy transfer (EnT, nonradiative energy transfer from excited photocatalysts to substrates without net electron exchange) and radical‐polar crossover (RPCC, a sequential process converting radical intermediates to ionic species via electron transfer to achieve polarity reversal). Particular emphasis is placed on the modular synthesis of high‐value scaffolds, including functionalized amines, pharmaceutically relevant heterocycles, and emerging bioisosteres like bicyclo[1.1.1]pentanes (BCPs). Furthermore, the paradigm shift toward sustainable synthesis, exemplified by the increasing use of metal‐free dyes and heterogeneous semiconductors, is highlighted. Finally, current challenges and future opportunities, particularly regarding stereoselective control and industrial scalability, are discussed.