Radical-Triggered Tandem Cyclization of 1,6-Enynes with HO: A Way to Access Strained 1 H-Cyclopropa[ b]naph thalene-2,7-diones.

A radical-triggered tandem cyclization of 1,6-enynes has been developed herein. Strained 1 H-cyclopropa[ b]naphthalene-2,7-diones are successfully obtained in moderate to good yields with excellent stereoselectivity. Mechanistic studies reveal a key role of water in generating a hydroxyl radical that initiates a sequential Michael addition/ring closure pathway. Importantly, the formed hydroxyl is proposed to be a good leaving group during the cyclopropane ring formation.