Solvent-free iodine-promoted synthesis of 3,2′-pyrrolinyl spirooxindoles from alkylidene oxindoles and enamino esters under ball-milling conditions

A novel solvent-free iodine-promoted cyclization of alkylidene oxindoles with enamino esters via C-C/C-N bond formation has been demonstrated under ball-milling conditions. This protocol provides efficient and green access to a variety of 3,2'-pyrrolinyl spirooxindoles with remarkable functional group tolerance, good yields and excellent diastereoselectivities.