Ring Opening of a Cyclobutabenzene Complex under Very Mild Conditions

The isomerization to an ortho-quinodimethane complex from the alcoholate obtained from 1 and n-butyllithium takes place already between −78 and 0°C. The product can be trapped with common dienophiles like dimethyl fumarate as a [4 + 2] cycloadduct in good yields and high stereoselectivity. Compound 1 is synthesized according to the reaction scheme shown below.