A new twist for Stork-Danheiser products enabled by visible light mediated -cyclohexene formation; access to acyclic distal enones.

Herein, we investigate the use of visible light to indirectly drive ring opening in unstrained 6- and 7-membered ring systems reaction with a transiently generated -cycloalkene. Identification of conditions that capture visible light energy in the form of ring strain was key to success. Under mildly acidic conditions, cycloalkenols were shown to undergo formally endothermic ring-opening isomerization to give acyclic exo-methylene and distal ketones or aldehydes in high yields.