# Reaction Mechanism for a radical ring opening

I have a radical reaction which I got from an organic chemistry lecture and was drawing the possible mechanism for it.

Fig 2. shows my thought process. The I is removed making a radical and ISnBu$$_3$$. The radical opens the ring and the new radical is formed which then reacts with the hydrogen radical. However Fig 1. shows the reactants and products from the lecture which don't match with what I thought.

I don't see how the carbon on the "top" of the propane ring becomes part of the chain.

Could the lecture slides have been wrong or am I missing something?

• Without consulting the literature, there is the possibility that fig. 2 is a product of kinetic control whereas fig. 1 is the product of thermodynamic control. The second radical in fig. 2 would recyclize under dilute Bu3SnH concentration. This is certainly the case for the bromo epoxide analog of the cyclopropyl iodide. Sep 5 at 17:57
• @user55119 is there be a reaction mechanism for the thermodynamically controlled product? I just don't see how the carbon can become part of the chain Sep 5 at 18:13
• After you form the radical, break the "bottom" bond in the cyclopropane ring. That produces your terminal double bond and a resonance stabilized benzylic radical. Breaking the other cyclopropane bonds does not produce a stabilized radical.
– ron
Sep 5 at 18:47
• @Ron just beat me to it. Sep 5 at 18:51