Nickel-mediated stereocontrolled synthesis of spiroketals via tandem cyclization-coupling of β-bromo ketals and aryl iodides.

A ketal-tether approach for the stereoselective synthesis of [5,5] and [5,6]-spiroketals based on reductive coupling catalyzed by the readily available Ni complex is demonstrated. Either an intermolecular or an intramolecular stereospecific cascade has been achieved as well.