Radical cyclization of alkynyl aryl ketones for the synthesis of 3-seleno-substituted thiochromones and chromones.

We report a strategy for the direct synthesis of 3-organylselanylthiochromones and 3-organylselanylchromones via the radical cyclization reaction between alkynyl aryl ketones containing an ortho-thiopropyl/methoxy group and diorganyl diselenides promoted by Oxone®. This method allows the construction and seleno-functionalization of thiochromones and chromones using Oxone® as a stable and non-hazardous oxidizing agent in the presence of CH3CN at 82 °C. These reactions tolerate a variety of substituents, and allowed the synthesis of twenty-one new 3-organylselanylthiochromones and selanylchromones in good to excellent yields (55-95%). Additionally, the developed method proved to be suitable for scale up (3.0 mmol, 80%), and the synthetic usefulness of the prepared compounds was demonstrated in the oxidation of 2-phenyl-3-(phenylselanyl)-4H-thiochromen-4-one.