AIBN initiates a radical chain; tin radical abstracts iodine to generate the terminal carbon radical. Intramolecular attack on the ketone gives a cyclic alkoxy radical, which undergoes β-scission to expand the ring and restore a carbonyl. The resulting carbon radical abstracts hydrogen from tin hydride. This gives the saturated ring-expanded keto ester A. The unsaturated or iodine-retaining alternatives do not represent this radical ring-expansion sequence.
More Types of Reactions: Nucleophilic and electrophilic substitution reactions (both aromatic and aliphatic). Addition reactions to carbon-carbon and carbon-heteroatom (N and O) multiple bonds. Elimination reactions. Reactive intermediates – carbocation, carbanion, carbenes, nitrenes, arynes and free radicals. Molecular rearrangements. Barton decarboxylation and Barton-McCombie reaction, Hunsdiecker reaction. questions
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