Recent advances of 4CzIPN in visible-light-mediated ring-formation reactions towards N -heterocycles.

Abstract

Nitrogen-containing heterocyclic compounds are prevalent and play important roles across various fields, including medicine, natural products, agrochemicals, pharmaceuticals, and organometallic chemistry. The ongoing demand for novel techniques to synthesize these compounds has led to the growing popularity of ring-formation reactions, which enhance synthetic efficiency by enabling the simultaneous formation of multiple rings in a single transformation. Recently, visible-light-mediated photoredox catalysis has attracted attention for its clean and efficient approach, particularly in the context of green chemistry. Transition metal-free photoredox catalysis has emerged as a promising area, with the organophotocatalyst 4CzIPN standing out for its excellent redox potential, strong stability, and cost-effectiveness, which make it versatile for various applications. Despite the growing field of research on visible-light photoredox methods and the use of 4CzIPN, there is a lack of comprehensive analysis regarding its role in ring-formation reactions for synthesizing N-heterocycles. This review aims to fill that gap by summarizing recent advancements in 4CzIPN-catalyzed ring-formation reactions from 2020 to the present. It will provide a mechanistic overview, discuss the advantages and disadvantages of various synthetic protocols, and explore new opportunities for sustainable methods to create structurally diverse N-heterocycles. The review is organized into seven sections based on the structural formation of N-heterocycles, including the synthesis of oxindoles, quinolinones/quinolines/isoquinolines, quinazolinones/fused quinazolinones, phenanthridines, indoles/pyrrolo[1,2-a]indoles, indole[2,1-a]isoquinolinones/benzimidazo[2,1-a]isoquinolinones, and miscellaneous compounds.

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