Perylenequinonoid-Catalyzed [4 + 1] and [4 + 2] Annulations of Azoalkenes: Photocatalytic Access to 1,2,3-Thiadiazole/1,4,5,6-Tetrahydropyridazine Derivatives

Abstract

Nitrogen-containing heterocycles are especially considered “privileged” structural scaffolds for the development of new drugs. However, traditional methods of organic synthesis are mainly based on thermal cycloaddition reaction; thus, the exploration of new strategies for the rapid assembly of N-heterocycles under mild conditions is highly desirable. Here, we developed a new method that visible light along with 1 mol % cercosporin, which is one of the perylenequinonoid pigments with excellent properties of photosensitization and can be easily produced by a new isolated endophytic fungus Cercospora sp. JNU001 strain with high yield through microbial fermentation, catalyzes the synthesis of 1,2,3-thiadiazoles and 1,4,5,6-tetrahydropyridazines by a photocatalytic process with good regioselectivity and broad functional-group compatibility under mild conditions. Thus, a bridge between microbial fermentation and organic photocatalysis for the construction of nitrogen-containing heterocycles was set up in a sustainable, environmentally friendly manner.

Aryldiazonium Salts in Photoredox Catalysis – Recent Trends

“…[76] Cercosporin (CP), synthesized from liquid fermentation of glucose, was used as the photocatalyst for this transformation. [77] Excited photocatalyst, CP* acts as a reductant to form aryl radicals from aryldiazonium salts. Thiol then reduces the oxidized photocatalyst to form ground state cercosporin, CP, and thiol radical cation.…”

“…Furthermore, aryldiazonium salts bearing electron donating and electron withdrawing substituents afforded the desired aryl sulfides in good yields (Scheme 50). [76] Cercosporin (CP), synthesized from liquid fermentation of glucose, was used as the photocatalyst for this transformation [77] …”

Recent Advances in Photocatalytic C–N Bond Coupling Reactions

“…Rao, Zhang and co-workers discovered an interesting cercosporin-catalyzed [4+2] homocyclodimerization of azoalkenes for the synthesis of 1,4,5,6-tetrahydropyridazine derivatives (Scheme 67). 71 The process is initiated by…”

Enhanced Cercosporin Production by Co-culturing Cercospora Sp. JNU001 With Leaf-Spot-Disease-Related Endophytic Bacteria

“…Cercosporin is also a potent inhibitor of protein kinase C (PKC) [18], which regulates numerous intracellular signal transduction, including cell differentiation, cell proliferation and in ammatory response, by controlling the function of other proteins through the phosphorylation. More recently, we have developed cercosporin as a new class of metal-free photocatalyst to catalyze a series of chemical transformations, including selective photxidation, C-H activation, C-N coupling and C-S coupling [19][20][21][22][23]. Meanwhile, it has also been utilized to fabricate a novel HARCP/HAp photocatalyst (HexaAcetyl-Reductive Cercosporin/Hydroxyapatite) after a simple structural modi cation, allowing to e ciently photoremove tetracycline in water pollution under natural sunlight [24].…”