Identify the major product of the following reaction:

Step-by-step solution

The given reaction involves the acid-catalyzed rearrangement of a spiro ketone. First, the carbonyl oxygen of the spiro[3.5]nonan-5-one is protonated by concentrated H₂SO₄ , generating a resonance-stabilized carbocation at the carbonyl carbon. Next, to relieve the significant angle strain of the four-membered cyclobutane ring, a C-C bond from this ring migrates to the adjacent carbocation center. This ring expansion results in a fused bicyclic intermediate containing a five-membered and a six-membered ring, with a