Pinacol Rearrangement

In the conversion that gave its name to this reaction, the acid-catalyzed elimination of water from pinacol gives t-butyl methyl ketone.

---

Mechanism

This reaction occurs with a variety of fully substituted 1,2-diols, and can be understood to involve the formation of a carbenium ion intermediate that subsequently undergoes a rearrangement. The first generated intermediate, an α-hydroxycarbenium ion, rearranges through a 1,2-alkyl shift to produce the carbonyl compound. If two of the substituents form a ring, the Pinacol Rearrangement can constitute a ring-expansion or ring-contraction reaction.

---

Recent Literature

Asymmetric Addition of Alkylzinc Reagents to Cyclic α,β-Unsaturated Ketones and a Tandem Enantioselective Addition/Diastereoselective Epoxidation with Dioxygen
S.-J. Jeon, P. J. Walsh, J. Am. Chem. Soc., 2003, 125, 9544-9545.