Electrochemical Annulation–Iodosulfonylation of 1,5-Enyne-containing <i>para</i>-Quinone Methides (<i>p</i>-QMs) to Access (<i>E</i>)-Spiroindenes

Abstract

A new electrochemical three-component annulation-iodosulfonylation of 1,5-enyne-containing <i>para</i>-quinone methides (<i>p</i>-QMs) has been established by using available arylsulfonyl hydrazides and potassium iodide under environmentally benign conditions. The electrosynthesis offers sustainable and efficient access to construct spirocyclohexadienone-containing (<i>E</i>)-indenes without any additional catalyst or oxidant through a sulfonyl-radical-triggered 1,6-addition and an I⁺-mediated <i>ipso</i>-cyclization cascade. Notably, potassium iodide plays the triple role of an electrolyte, a redox catalyst, as well as an iodination reagent.