In this review, the recent advances of the application of 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as a photoredox catalyst in the past three years (2016–2018) for various organic reactions are summarized.

By using water as the hydrogen source, an eco-friendly and practical protocol for the synthesis of Z-vinyl thiocyanates through ultrasound-promoted Brønsted acid ionic liquid-catalyzed hydrothiocyanation of activated alkynes under minimal solvent conditions has been developed. This process effectively avoids the use of organic solvents, metal catalysts and harsh reaction conditions. This reaction shows attractive characteristics such as operational simplicity, broad substrate scope with good to excellent yields, ease of scale-up and high energy efficiency and recyclable and reusable catalysts.

The first example of visible-light-induced deoxygenative C2-sulfonylation of quinoline N-oxides with sulfinic acids in the presence of an organic dye as the catalyst was developed. The reaction conditions are eco-friendly and mild, employing ambient air as the sole oxidant and aqueous acetone solution as the solvent. This approach requires only a very low catalyst loading, allowing gram-scale preparation as well as late-stage modification of biologically active compounds bearing quinoline groups.

A mild and eco-friendly visible-light-induced decarboxylative acylation of quinoxalin-2(1H)-ones and α-oxo carboxylic acids with ambient air as the sole oxidant at room temperature was established. The reaction proceeded efficiently without any metal catalysts, strong oxidants or external-photosensitizers, ultimately reducing the generation of waste.

An electrochemical multicomponent reaction was established under catalyst-, chemical-oxidant-free and mild conditions, which provides an eco-friendly and simple protocol for constructing 4-selanylpyrazoles from easily available raw materials with high yields.