[Rh^III(Cp*)]-catalyzed arylfluorination of α-diazoketoesters for facile synthesis of α-aryl-α-fluoroketoesters

Here we describe the Cp*Rh(III)-catalyzed cascade arylfluorination reactions of α-diazoketoesters with arylboronic acids and N-fluorobenzenesulfonimide for one-pot C(sp³)–C(aryl) and C(sp³)–F bond formation. The arylfluorination reaction can be accomplished with remarkable chemo- and regioselectivity. Our mechanistic investigation showed that the Rh-catalyzed arylfluorination of diazoacetates occurred by (1) transmetalation of arylboronic acids to form an arylrhodium(III) complex, (2) coupling of diazomalonates with the arylrhodium(III) complex to form carbene–rhodium, (3) migratory carbene insertion to form a diketonato-rhodium(III) complex – probably via rearrangement of the putative σ-alkylrhodium(III) complex, and (4) electrophilic fluorination of the diketonato-rhodium to form the α-aryl-α-fluoromalonates.