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

Abstract

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.

Can Twisted Double Bonds Facilitate Stepwise [2 + 2] Cycloadditions?

“…Trans- cyclohexenes were observed as transient photochemical species . Recently, Weaver et al , demonstrated the use of visible light to activate the cis -/ trans -photoisomerization of a cyclohexene and showed that the resulting trans- cycloalkene could then readily undergo addition reactions with alcohols and urethanes. Trans- cycloheptenes and trans- cyclooctenes can be prepared and can drive strain-promoted reactions, ,− and even larger cycloalkenes rings have less twisted double bonds …”