This review focuses on the synthesis of N-heterocycles using amidines as starting materials, with an emphasis on the mechanisms of these reactions via C–N/C–C bond formation.

Herein we report a novel C-S bond cleavage and reconstruction strategy for the synthesis of thiocyanates through direct photocatalytic S-H bond cyanation from thiols and inorganic thiocyanate salts. In our strategy, the unprecedented example of cutting off C-S bond of SCN to deliver the green "CN" sources is demonstrated. This transformation features nontoxic and inexpensive "CN" sources, available starting materials, metal-/base-/ligand-/peroxide-free, high step economy and mild conditions. It leads to the construction of various thiocyanates and some medicinally and biologically active thiocyanate-containing molecules.

An efficient and convenient photocatalytic direct C-3 sulfenylation of indoles with thiophenols has been developed for the construction of 3-sulfenylations.

Photocatalyzed organic synthesis transformation is a remarkable green synthetic strategy because of the advantages of operational simplicity, high chemoselectivities, cheap, and environmental benignancy, along with the extensive applications in the fields of organic, pharmaceutical and functional material chemistry. Generally, photoredox catalysts or photosensitizers are necessary for the generation of their excited states to perform the successive oxidative or reductive reactions through the single electron transfer (SET) or energy transfer (ET) process. Furthermore, the exploration of a colored electron donor-acceptor (EDA) complex or a charge transfer (CT) complex between an electron-rich and an electron-poor substrate provides the chance to deliver the excited intermediate under the irradiation of light, resulting in the formation of radical activate species through a single electron transfer to induce successive various radical reactions. These reactions were performed without the need of any external photocatalysts under mild reaction conditions. Herein, this review focuses on the recent progress on photoinduced radical addition reactions, radical borylations, reductive reactions, radical-radical cross-coupling reactions, degradation reactions and radical cascade cyclization via EDA complexes. We highlight these novel green synthetic methodologies and applications, as well as the mechanisms. This review will help to provide references for organic and medicinal chemists who are charmed by these green organic photochemical transformations based on EDA complexes.

In this review, we have focused on the recent advances in photocatalytic C–S/P–S bond formation via the generation of thioyl/sulfonyl radicals and further functionalization.