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Abstract

As mentioned previously in the Chapter 1.1.2, the use of bench-stable aryl sulfonium salts, in particular arylthianthrenium salts as a versatile linchipin, can functionalize the arenes with high site selectivity.[4] However, the electrophilic thianthrenation of arenes often occurs at the most electron-rich site of the aromatic ring (para-position of monosubstituted arenes), thus resulting in the inaccessibility of ortho- and meta-position functionalization. The Chatani group and Yu group have developed a template-directed sequential ortho- (or meta-) C–H and ipso-C–O bond functionalization by using a novel bifunctional template included a directing group, respectively.[14-15] Nevertheless, the installation of the bifunctional template limited the application to the C–H functionalization due to the requirement of the specific arene-substrates, only phenol substrates could be functionalized with this strategy. To combine the advantages of the above two strategies, template 34, which contains a thianthrene-like structure and a directing group, would be designed in this project (Figure 1).
The goal of this project is to achieve sequential meta-, para-, or ortho-, para-C–H (relatively to the ipso substituent) functionalization of arenes with a novel bifunctional 11 template. The template was designed to combine two functions. The first function is the formation of sulfonium salts with high site selectivity, which could be directly converted into a variety of functional groups with transition metal or photoredox catalysis in the final step. The azaphenoxathiin template in intermediated XIV and dibenzothiophene template in intermediate XV would be utilized for this strategy. The second function is to use the directing group included with the template (such as the pyridine or nitrile directing group) to direct the remote C–H olefination (meta- or ortho-position) (Scheme 7).