Electrochemical reaction of indole-tethered alkynes enabling stereoselective synthesis of iodovinyl spiroindolenine-cyclopentanes†

A novel electrochemical iodination/spirocyclization reaction of 3-alkynyl indoles with n-Bu₄NI as coupling partner and electrolyte is developed, which affords iodovinyl spiroindolenine-cyclopentanes as products in excellent yields and high E-stereoselectivities. This reaction tolerates a wide range of 3-alkynyl indoles and iodide sources, which represents the first example of the electrosynthesis of spiroindolenine-cycloalkanes.