No abstract

A new protocol for the synthesis of thieno[3,2-c]coumarins is disclosed herein. Following this method, 3-formyl-2-oxo-2H-chromene-4-thiolate is in-situ generated by the combination of 4-chloro-3-formylcoumarin and sodium sulfide. This chromene-4-thiolate undergoes L-proline catalyzed substitution/Knoevenagel cascade with α-haloketone to afford the desired thieno coumarins in moderate to good isolated yields. The described protocol eliminates the need for stoichiometric amounts of inorganic bases and the use of foul smelling thiols. The reaction conditions tolerate a variety of α-haloketone.