Photoredox catalytic metathesis of TT-salts and aryl bromide/chloride via multicatalysis

Sulfonium salts emerge as unique synthetic intermediates in recent years. Versatile exciting transformations have been developed since the breakthrough works by Procters and Ritters group.

Progress made within just 4-years since thesee seminal works showcased their broad utilities surpassing that of organic halides.

Depending on the conditions, sulfonium salts engaged in various types of transformations such as Suzuki coupling, Sonogashira coupling, Negishi coupling, Heck reaction, carbonylation, boronation, chlorination, iodination, cyanation, photocatalysis, etc., and realize the constructions of various C-C, C-N, C-O, C-X and C-S bonds.

Therefore, they are considered Skeleton Key in Late state Functionalization thanks to excellent compatibility.

However, compared with organic halides that widely exist in nature and are commercially available, the synthetic methods for thiananthenium salts are still very limited. Currently, the direct C-H activation is the rare method showing efficiency for constructing aryl thianthranium salts.

Although this synthetic method showed a remarkable advantage in exquisite remote regioselectivity, it also uncovered a challenge in making other sulfonium salts with other substitution patterns impossibly, such as on ortho- and meta-positions.

Herein I propose to explore the potential of preparing synthetically omnipotent diversative aryl thianthranium (TT) salts from available aryl halides via functional group metathesis.

Attractively, the method will overcome the current limitation to the para-derivatives of TT-salts, giving access to any substitution pattern of TT-salts (ortho-, meta-, para-, bissubstituted, etc.).

The target TT-salts will open up a vast realm of transformations and construction of useful skeletons in fine chemical synthesis and development.