Aryl(Mes)iodonium salts are broadly useful aryl transfer reagents in transition metal catalysis, and as aryne precursors. A commonly used approach to access these reagents is a protocol originally described by Ochiai using aryl boronic acid and diacetoxy iodobenzene in a boron-iodane exchange reaction. However, diacetoxy iodomesitylene is sterically congested and less reactive than its benzene counterpart and the yields of aryl(Mes)iodonium salts are lower, especially with electron deficient aryl boron reagents ( average yield 55%, n=14 ). Here we describe our efforts to improve the yield of the boron-iodane exchange reaction for the synthesis of electron deficient aryl(Mes)iodonium tetrafluoroborates. We have developed two complementary sets of reaction conditions to access these compounds from potassium aryltrifluoroborate salts. The two reaction conditions developed allow flexibility of operation depending on the functionality on the aryltrifluoroborate salts. These modifications allow the reactions to be performed open-to-air at room-temperature under 1 hour. Finally, the mechanism of the boron-iodane exchange was probed by Hammett analysis to determine the extent of substitution participation under our reaction conditions.

Expanding the scope and mechanistic understanding of the Boron iodane exchange reaction to synthesize Aryl(Mes)iodonium salts

ACS Fall 2021

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