Rearrangements – Semipinacol rearrangements of diazonium salts

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When diazomethane adds to a ketone, the product undergoes a ring expansion by rearrangement of the intermediate. Cyclohexanone is more reactive as an electrophile than either cyclopentanone or cycloheptanone, so it ring expands cleanly to cycloheptanone.

Z.-L. Song, C.-A. Fan and Y.-Q. Tu, Chem. Rev., 2011, 111, 7523–7556.