Reaction of chromone-3-carboxaldehydes with TOSMIC: synthesis of 4-(2-hydroxybenzoyl)pyrroles

Chromone-3-carboxaldehydes 1 react with tosylmethylisocyanide (TOSMIC) in the presence of DBU in THF at room temperature to furnish, after in situ deformylation, good yields of 2-tosyl-4-(2-hydroxybenzoyl)pyrroles 2. When the same reaction is performed with potassium carbonate in methanol under reflux pyrroles 2 are again isolated, but in lower yields. Finally, from the reaction of 1a in the presence of a stronger base (NaOH) only a small amount of the 3-substituted derivative 3a along with polymeric material is isolated.