Synthesis of Perfluoroalkylated Pyrazoles from α-Perfluoroalkenylated Aldehydes.

Within this study, we report a simple two-step process for the synthesis of perfluoroalkylated pyrazoles from aliphatic aldehydes. In the photocatalytic first step, the aldehydes are transformed into the corresponding perfluoroalkylated enals, which then undergo nucleophilic attack by hydrazine and subsequent ring closure, providing the fluorinated 3,4-substituted pyrazole products in a 64-84% yield. Using triphenylphosphine and imidazolidinone as organocatalysts, the method is operationally simple and omits heavy metal-containing waste.

Straightforward Synthesis of Fluorinated Enals Photocatalytic α-Perfluoroalkenylation of Aldehydes.

(Per)fluorinated substances represent an important compound class with regard to drug design and material chemistry. We found a mild, operationally simple, and inexpensive photocatalytic perfluoroalkenylation reaction giving tetrasubstituted, highly electron-deficient enals straight from aldehydes. This one-step reaction tolerates various functional groups and can be applied to a wide range of substrates giving the products in yields of 52-84%.