Wagner rearrangement

:  a reaction that is applicable especially to organic compounds containing a neopentyl or similar grouping, that is thought to proceed by way of a carbonium ion, and that involves change of the carbon skeleton (as from pinene to bornyl chloride by hydrogen chloride, from neopentyl iodide to tert-amyl acetate by silver acetate, or from methyl-tert-butyl-carbinol to tetramethyl-ethylene by acids) — compare pinacolone