[sw2672]

The desired product was obtained when the reaction was conducted with DTBP (Di-tertiarybutyl peroxide) in the water solvent.
However, when the same reaction was conducted in other solvents such as MeOH, toluene, DMF, and DMSO no product was formed.
The reactions at MeCN or dioxane afforded the product in 40% and 20% yields.
Is there any role of the water in the radical mechanism?

[wildfyr]

Think about what would be present if water were to react with DTBP? Does that compound have different reactivity than DTBP?

Do any of these solvents also react with DTBP? Does that product have very different reactivity?

I would leave MeCN and dioxane aside for a moment and focus on water vs the other solvents.