Retro-favorskii reaction employing fluoride sources and its use as immobilization strategy

Abstract

In this study, we developed a novel and simple approach to perform retro-Favorskii type reactions comprising the use of a readily available fluoride source. Compared to the methods usually employed – which rely on the use of strong basic systems, such as KOH in toluene, at high temperatures and a reaction time of several hours – the one we propose employs milder conditions, shorter reaction times, is compatible with more solvents, and produces no appreciable amount of byproducts, thus allowing simple workup procedures. The reaction we describe is enabled by the strong basic character of the fluoride ion in absence of water. However, we observed that the reaction is remarkably tolerant to humidity and no anhydrous conditions are needed, making the reaction extremely straightforward to perform. The possibility of performing such reactions in a fast and reliable manner, without the appreciable formation of byproducts, can offer new interesting opportunities to efficiently employ propargyl alcohols derivatives as a masking group for carbonyls. The latter approach can be particularly interesting for the synthesis and derivatization of carbonyl-rich compounds – such as large, conjugated, electron-deficient systems or quinoid-based pigments – for which the limited solubility often precludes the synthesis of certain derivatives or their application in functional devices.