AbstractMalonic esters and other derivatives, with thio or selenophenol in polyphosphoric acid, lead to unexpected Simonis reaction. Instead of 4‐hydroxy 1‐thio or 1‐selenocoumarines they give 2‐phenylthio‐1‐thio chromones or 2‐phenylseleno 1‐seleno chromones. Several intermediates are considered. The most probable one seems to be an acrylic compound formed via the thiophenyl or selenophenyl ethyl malonate (or malonic acid). «Mixed» chromones are indeed obtained from these thiolesters or thiolacids and selenophenols