One-Pot Synthesis of Functionalized 2,5-Dihydrofurans via an Amine-Promoted Petasis Borono–Mannich Reaction

A series of functionalized 2,5-dihydrofurans were efficiently synthesized via an amine-promoted Petasis borono–Mannich reaction of 4-substituted 1,2-oxaborol-2(5H)-ols with salicylaldehydes in high yields. The process, which combines a boronic acid-based Mannich reaction and a highly efficient intramolecular SN2 cyclization, provides a one-step and efficient route toward 2,5-dihydrofurans from simple and stable starting materials.