Base‐mediated 1,4‐Conjugate Addition/Intramolecular 5‐exo‐dig Annulation of Propargylamines with Benzoylacetonitriles and β‐Keto Esters for Polysubstituted Furans and Furo[3,4‐c]coumarins Formation

A novel and one‐pot domino reaction of propargylamines with benzoylacetonitriles and β‐keto esters for the regiospecific synthesis of polysubstituted furans and furo[3,4‐c]coumarins has been developed. The reaction is believed to proceed by sequential 1,4‐conjugate addition of benzoylacetonitriles/β‐keto esters to propargylamines, 5‐exo‐dig annulation/isomerization to form the fully substituted furans, and intramolecular transesterification to furo[3,4‐c]coumarin skeleton. The features of this method include inexpensive base, readily available substrates, high regioselectivity, and convenient operation. A wide variety of densely functionalized furans and furocoumarins are furnished by one‐pot domino process and transition‐metal free methods in moderate to good yields, respectively.