Assembly of 3,5-Dihydroxy-4 <i>H</i> -selenopyran-4-one Core via Recyclization of Allomaltol Derivatives under Action of Triselenium Dicyanide

In the present work, we described the first example of construction of a previously unknown 3,5-dihydroxy-4H-selenopyran-4-one scaffold. The considered approach is based on the cascade process including selenocyanation of substituted allomaltols under action of triselenium dicyanide followed by recyclization of a 3-hydroxypyran-4-one unit into the 3,5-dihydroxy-4H-selenopyran-4-one moiety. Triselenium dicyanide used for selenocyanation was generated in situ from readily available selenium dioxide and malononitrile. The elaborated method demonstrates wide substrate compatibility under mild reaction conditions, opening access to the array of target 2-acetyl-6-aroyl-3,5-dihydroxy-4H-selenopyran-4-ones with yields up to 69%. For exploration of the mechanistic pathway, 77Se NMR monitoring experiments of the reaction mixture were carried out.