Catalyst-Free Organic Transformations under Visible-Light

Abstract

Pollutants from industry and chemical laboratories have harmful effects on human health and the environment. Concerns about this problem have led to the development of more versatile and sustainable protocols based on the principles of green chemistry. One of these innovative approaches is to carry out the reactions under visible-light sources without photocatalysts. This benign, simple, and cost-effective method, inspired by nature, could be a suitable alternative to some classical methods, and change the harsh reaction conditions into milder ones. In this Perspective, we outlined the results of catalyst-free organic reactions under visible-light to further encourage researchers in this promising field. The proposed mechanisms based on the generation of an electron donor−acceptor complex (EDA) and a single-electron transfer (SET) pathway were discussed.

Synergism between few-layer black phosphorus and graphitic carbon nitride enhances the photoredox C–H arylation under visible light irradiation

“…55 Following this pioneering study, C-H arylations have been reported using metal-free photocatalysts ranging from organic molecules, [56][57][58][59][60] polymers, 61 and semiconductors, namely BP, 8 g-CN/rGO, 28 biocatalyst 62 and etc. 63 Given the benefits of this new area in organic synthesis, photoredox catalysis for the direct C-H bond functionalization is now one of the best attractive options. The production of aryl radicals by single-electron transfer (SET) to a convenient substrate is the key step of photoredox C-H functionalization.…”

Visible-light-promoted sulfenylation of 6-aminouracils under catalyst-free conditions

“…9 Some exciting results under catalyst-free visiblelight-promoted reaction conditions have been published since 2017. 10 In recent years, efforts have been made for the site-selective synthesis and modification of bioactive scaffolds in order to increase their structural diversity and utilization. 11 Pyrimidines, an integral part of DNA and RNA, show diverse pharmacological applications as effective bactericides, antivirals, insecticides, fungicides, and medicines.…”

“…9 Some exciting results under catalyst-free visible-light-promoted reaction conditions have been published since 2017. 10…”

Recent Developments on Catalyst‐Free, Visible‐Light‐Triggered Synthesis of Heterocyclic Scaffolds and Their Mechanistic Study

“…Sometimes, in case of electron donor-acceptor (EDA) complexes, an electron-transfer event can occur by absorbing visible light without need of any photocatalyst. [10] The heterocyclic scaffolds comprise one of the largest research areas in organic chemistry and have always been on the frontline of attention due to their abundant uses in pharmaceutical fields. [11,12] The importance of heterocyclic compounds for biomedical and material science applications has led to an increase in the development of novel methods for their preparation.…”