Electrochemical Oxidative Annulation of Inactivated Alkynes for the Synthesis of Sulfonated 2 H -Chromene Derivatives.

A unique, facile, and straightforward electrochemical oxidative annulation of inactivated propargyl aryl ethers with sulfonyl hydrazides leading to 3-sulfonated 2 H -chromenes has been achieved. Significantly, this protocol involves a green approach that works under mild reaction conditions using a constant current in an undivided cell and is devoid of oxidants and catalysts. Notably, the process exhibited a broad scope and functional group tolerance to deliver 2 H -chromenes and would represent an alternative and sustainable strategy versus conventional chromene synthesis.