Mizoroki-Heck Reactions with 4-Phenoldiazonium Salts

Significantly better yields were achieved in Mizoroki–Heck reactions using 4‐phenoldiazonium salts instead of their O‐alkylated analogues under otherwise identical conditions. We found that a one‐flask deacetylation–diazotation–precipitation sequence starting from paracetamol or acetanilides derived thereof provides a convenient access to the required diazonium tetrafluoroborates. The utility of these arylating agents in palladium‐catalyzed CC bond forming reactions was demonstrated for a one‐flask‐synthesis of the heterocyclic core of the drug aripiprazole. Notably, the diazonium salt formation from an acetanilide could be combined with two Pd‐catalyzed steps in a one‐flask sequence, without any exchange of solvents or isolation of intermediates.