Radical Smiles rearrangement process

An unprecedented domino radical cyclization/Smiles rearrangement process of 175 to give 3-(2-aryl-N-methylacetamido)indolin-2-ones 178 or 180 was reported by Gerard, Sapi, et al. [63] (Scheme 5.38). The reaction proceeds via a 5-exo-trig cyclization followed by radical substitution. The radical intermediate 177, formed via the radicals A and 176, could undergo either a normal termination of a radical to form product 178 in 11-66% yields or an additional amidyl radical cyclization, giving the product 180 in up to 40% yield depending on the reaction conditions. 

Scheme 5.38 Domino radical cyclization/Smiles rearrangement process.

Smiles processes involving three-membered cyclic transition states are much less frequent under ionic conditions.However, similar Truce-Smiles processes under radical conditions are well documented. Known as neophilic rearrangements, they lead to efficient carbon-aryl bond formation with frequent extrusion of small molecules such as sulfur dioxide. These Smiles-type reactions involving cyclic transition states with a small ring size will not be evaluated further in this chapter. 

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