Metal-free regioselective oxidative biaryl coupling leading to head-to-tail bithiophenes: reactivity switching, a concept based on the iodonium(III) intermediate.

A new synthetic concept for obtaining unsymmetrical biaryl coupling products by an oxidative method is reported. Our synthetic strategy casts light on the reaction intermediate for switching the reactivity of 3-substituted thiophenes. On the basis of this strategy, a novel direct method for the synthesis of head-to-tail bithiophenes using hypervalent iodine(III) reagents has been developed.