Exploiting Visible Light Triggered Formation of trans-Cyclohexene for the Contra-thermodynamic Protection of Alcohols

We report herein a method for the contra-thermodynamic protection and thermodynamic deprotection of alcohols in which all reagents are returned to their original state. This is accomplished by the use of visible light photochemical energy to drive the formation of a highly strained trans-(Z)-cyclohexene. At STP the product ethers contain more potential energy than the starting materials and, thus, can be catalytically returned to the starting materials, effectively realizing a protection–deprotection scheme paid for with an energy currency.