One-pot synthesis of functionalized benzo[c]-coumarins and their precursors via the reaction of 2-(polyfluoroalkyl)chromones with 4-alkyl-3-cyanocoumarins

2-(Polyfluoroalkyl) chromones react with 4-alkyl-3-cyanocoumarins in dichloromethane in the presence of triethylamine to give a wide variety of functionalized benzo[c] coumarin derivatives in good yields. This new annulation reaction presumably proceeds by a tandem intermolecular Michael addition and subsequent intramolecular condensation between an intermediate enolate anion and cyano group. In the case of 3-cyano-4-methylcoumarin and 2-(trifluoromethyl) chromones activated by two electron-withdrawing substituents, three acyclic intermediates were isolated and the possible mechanism of the reaction was suggested.