A One‐Pot Synthesis of Pyranocoumarins Through Microwave‐Promoted Propargyl Claisen Rearrangement/Wittig Olefination. Issue 2 (16th January 2018) - Schmidt, Bernd
Abstract : The reaction between propargyl ethers of hydroxybenzaldehydes and the ylide ethyl (triphenylphosphoranylidene)acetate was carried out under microwave irradiation to regioselectively afford angular pyranocoumarins. The chromene and coumarin heterocyclic scaffolds were simultaneously formed in the same synthetic step without changing the reaction conditions. The natural products seselin, braylin, and dipetalolactone were among the products synthesized by this method. Abstract : A method towards the synthesis of angular pyranocoumarins from propargylic ethers has been developed. The sequence proceeds through a microwave‐promoted tandem propargyl Claisen rearrangement, Wittig olefination, E/Z isomerization, and cyclization series of reactions in times as low as 10 min.