Publication
Fluorinated pyridones are an important scaffold displaying relevant biological activities. Efficient assembly strategies of pyridones are transition metal-catalyzed C–H annulations with alkynes. The inaccessibility and extreme lability of fluoro alkynes render any direct utilization in catalysis futile. We report a highly regioselective synthesis of 4-fluoro-2-pyridones using 1-alkynyl triazenes as a convenient fluoroalkyne surrogates. The protocol comprises an alkenyl C–H annulation with 1-alkynyl triazenes followed by a treatment with HF·pyridine smoothly delivering a broad range of 4-fluoro-2-pyridones in a one-pot fashion in 90 min at 23–60 °C. Notably, a rare Lossen rearrangement occurs during the C–H functionalization part of the transformation, allowing selective access to the less-available 4-fluoro-2-pyridone framework. Furthermore, the triazenyl intermediate was elaborated into additional fluorine-containing substituents like fluorinated alkoxy and trifluoromethyl groups.
Alkynes are found in a multitude of natural or synthetic bioactive compounds. In addition to the capacity of these chemical motifs to impact the physicochemical properties of a molecule of interest, the well-established reactivity of alkynes makes them ...