Efficient Formation of 2,3-Dihydrofurans via Iron-Catalyzed Cycloisomerization of α-Allenols

Herein, we report a highly efficient iron-catalyzed intramolecular nucleophilic cyclization of α-allenols to furnish substituted 2,3-dihydrofurans under mild reaction conditions. A highly diastereoselective variant of the reaction was developed as well, giving diastereomeric ratios of up to 98:2. The combination of the iron-catalyzed cycloisomerization with enzymatic resolution afforded the 2,3-dihydrofuran in high ee. A detailed DFT study provides insight into the reaction mechanism and gives a rationalization for the high chemo- and diastereoselectivity.