Methylene blue is a versatile organic dye, which possesses the adequate potential to be used in photochemical reactions. This readily available dye utilizes visible light as a source of renewable...

Quaternary pyridinium compounds are valuable intermediates in organic synthesis, which have gained immense popularity in the synthetic community. The application of transition metal or photoredox catalysis in transforming quaternary pyridinium compounds into various CÀ C and CÀ X bonds is well established. A majority of these methods require high temperatures, expansive catalysts, and delicate conditions for successful execution. On the other hand, the use of transition metal-free and photocatalysis-free strategies in constructing CÀ C and CÀ X bonds using quaternary pyridinium derivatives has been sought-after. In this context, the electron-donor-acceptor (EDA)-complex reactions have emerged as a state-of-the-art organic synthetic methodology, which do not require any photocatalyst for their successful execution. EDA-complex photochemistry takes advantage of the electron-acceptor ability of quaternary pyridinium derivatives, which can quickly generate a radical precursor via the deaminative process. These newly generated radical intermediates are useful in several valuable transformations. We hereby, in this review, discuss an area of major progress in EDA-complex mediated reactions involving quaternary pyridinium compounds with mechanism, substrate scope, and limitations.

Photoredox chemistry has emerged as an efficient tool in catalyzing organic reactions as it utilizes light as an energy source without any external initiator or reagent. The cyanide group is...

The 1,n-enynes are potent scaffolds in organic synthesis, providing a state-of-the-art approach for synthesizing various acyclic and carbo-and heterocyclic compounds. Radical cascade cyclization and CÀ H functionalization of 1,n-enynes have gained immense attention in the synthetic community. Significant advancement in this field has been developed over the years, employing harsh and expensive metal catalysts usually associated with intense product purification and unwanted side-products. In this context, the advent of visible light photocatalysis as a mild and efficient approach in the area of 1,nenynes is a welcome step. Herein, we provide an exclusive overview of the recent developments in visible light-assisted manipulation of 1,n-enynes. We have classified the review into 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, and 1,8-enynes, as well as dienyne, and enediyne-based reactions.

Heterocyclic N-oxides are prevalent in numerous natural products with broad applications in pharmaceuticals, agrochemicals, material sciences, and asymmetric synthesis. Owing to their profound biological and physiological activity and unique chemical reactivity, the importance of these compounds has stimulated substantial interest among organic synthetic chemists. More importantly, C-2 functionalization of heterocyclic N-oxides, including pyridine-, isoquinoline-, pyrazine-, quinoxaline-, and quinoline N-oxides, is among the most important strategies for heterocyclic functionalization. Besides, deoxygenation of heterocyclic N-oxides has also emerged as a reaction of significance in organic chemistry. In the past decade, visible light photoredox catalyzed C-2 functionalization and deoxygenation of these heterocyclic N-oxides have drawn substantial attention owing to their mild reaction conditions. This review has been categorized based on visiblelight-mediated nondeoxygenative C-2 functionalization (alkylation, fluoroalkylation, arylation, acylation, and amination), deoxygenative C-2 functionalization (sulfonylation, alkynylation, alkylation, and acylation), and deoxygenation (without CÀ H functionaliza-tion) of heterocyclic N-oxides. For most part of the work, the substrate scope, limitation, and mechanism of the reactions have been discussed.