Phosphine-catalyzed domino reaction for the synthesis of conjugated 2,3-dihydrofurans from allenoates and Nazarov reagents

A new domino reaction for Nazarov reagents: An efficient approach was developed for the construction of highly functionalized conjugated 2,3-dihydrofuran skeletons. Nazarov reagents were used for the first time in a phosphine-catalyzed domino reaction and successfully used to construct five-membered ring compounds using alcohol as the solvent. DFT calculations indicate that alcohol is essential for the catalysis of the [1,2]-proton transfer.