Pinacol Coupling Reaction

This reaction involves the reductive homo-coupling of a carbonyl compound to produce a symmetrically substituted 1,2-diol. The first step is single electron transfer of the carbonyl bond, which generates radical ion intermediates that couple via carbon-carbon bond formation to give a 1,2-diol. The example depicted above shows the preparation of pinacol itself.

Pinacol and other highly substituted 1,2-diols tend to undergo dehydration with rearrangement under acid-catalysis (see Pinacol Rearrangement).

Recent Literature

Catalytic, Highly Enantio- and Diastereoselective Pinacol Coupling Reaction with a New Tethered Bis(8-quinolinolato) Ligand

A highly enantioselective catalytic protocol for the intramolecular reductive coupling of ketones and hydrazones furnishes cyclic syn 1,2-amino alcohol derivatives with excellent levels of diastereo- and enantioselectivity. The reaction proceeds through neutral ketyl radical intermediates generated via a concerted proton-coupled electron transfer event jointly mediated by a chiral phosphoric acid catalyst and a photoredox catalyst.

A Convenient Synthesis of Unsymmetrical Pinacols by Coupling of Structurally Similar Aromatic Aldehydes Mediated by Low-Valent Titanium

Zn/InCl₃-Mediated Pinacol Cross-Coupling Reactions of Aldehydes with α,β-Unsaturated Ketones in Aqueous Media

Samarium Diiodide-Catalyzed Diastereoselective Pinacol Couplings

Samarium(II)-Mediated Pinacol Coupling in Water: Occurrence of Unexpected Disproportionation and Action of Low-Valent Samarium as an Active Species

Novel and efficient Ni-mediated pinacol coupling of carbonyl compounds