Influence of Ring Strain on the Formation of Rearrangement vs Cyclization Isotwistane Products in the Acyl Radical Reaction of Bicyclo[2.2.2]octanone

An acyl radical reaction of bicyclo[2.2.2]octenone to yield either rearranged or cyclized isotwistane products is described. The influence of ring strain on the reaction was demonstrated by alternating the sizes of the fused ring in the starting material. DFT calculations showed that the reaction is under thermodynamic control and proceeds via a 5-exo-trig cyclization intermediate, which undergoes either hydrogen-atom transfer (HAT) to give a cyclized product or rearrangement via a twistane intermediate to give a rearranged product.

Automated summary

An acyl radical reaction of bicyclo[2.2.2]octenone is described, which can yield rearranged or cyclized isotwistane products. The influence of ring strain on the reaction was demonstrated. DFT calculations showed that the reaction is under thermodynamic control and proceeds via a 5-exo-trig cyclization intermediate, which can undergo either hydrogen-atom transfer to give a cyclized product or rearrangement via a twistane intermediate to give a rearranged product.