Oxidative dithianylium salts

A very generally applicable method for converting a variety of different functional groups into their partially or fully fluorinated analogs is the oxidative fluorodesulfuration of thiocarbonyl compounds, dithiolanes, dithianes, and dithianylium salts. 

Scheme 2.72 Synthesis of liquid c stals by oxidative fluorodesulfuration of xanthogenates (aboi e) [162], and by the oxidative alkoxydifluorodesulfuration of dithianylium salts (beloiv) [163].

Scheme 2.73 Synthesis of ,c -difluoroether-linked liquid crystals by oxidative alkoxydi-fluorodesulfuration of dithianylium salts. The intermediate dithioorthoester is only stable at temperatures below ca — 50 C [147a].

Dithianylium salts in combination with oxidative fluorodesulfuration chemistry are also useful reagents for synthesis of gem-difluoromethylene analogs of carboxylic acid derivatives other than esters. If the fluorodesulfuration is conducted in the presence of other O- or M-nucleophiles the corresponding a.a-difluoroalkyl compounds are obtained in reasonable to good yields (Scheme 2.74). 

Oxidative Alkoxydifluorodesulfuration of Dithianylium Salts A.7.1 Dithianylium Triflate 27... 

R-CF2OOR Dithianylium salt oxidative fluorodesulfliration in the presence of R -OOH 72... 

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