Identify the major product of the following reaction:

Step-by-step solution

The given reaction is an acid-catalyzed semi-pinacol rearrangement. The starting material contains a cyclobutanol ring and an enol ether moiety (the 4,5-dihydrofuran ring). In the presence of concentrated H₂SO₄ , the electron-rich double bond of the enol ether is readily protonated. Protonation occurs at the -carbon (C3 of the dihydrofuran ring) to generate a highly stable, oxygen-stabilized carbocation (an oxonium ion) at the C2 position. This carbocation is adjacent to the cyclobutane ring, setting up the conditi