An efficient catalytic (2 + 2)-cycloaddition reaction leading to the formation of cyclobutane rings has been devised. The process transforms silyl enol ethers and α,β-unsaturated esters into polysubstituted cyclobutanes with a high degree of trans-stereoselectivity. Both the rate and stereoselectivity of the process can be controlled by the choice of the ester group and silyl substituents. The results
An arylative ringexpansion cascade has been developed for the synthesis of medium-sized carbocycles from fused cyclobutenes. This reaction proceeds through a short-lived cis,trans-cycloalkadiene intermediate that is formed by thermal 4π electrocyclic ringopening. Chirality transfer experiments provide direct evidence for the transient generation of the intermediate.