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).

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Recent Literature

Catalytic, Highly Enantio- and Diastereoselective Pinacol Coupling Reaction with a New Tethered Bis(8-quinolinolato) Ligand
N. Takenaka, G. Xia, H. Yamamoto, J. Am. Chem. Soc., 2004, 126, 13198-13199.

Samarium Diiodide-Catalyzed Diastereoselective Pinacol Couplings
H. C. Aspinall, N. Greeves, C. Valla, Org. Lett., 2005, 7, 1919-1922.

Samarium(II)-Mediated Pinacol Coupling in Water: Occurrence of Unexpected Disproportionation and Action of Low-Valent Samarium as an Active Species
S. Matsukawa, Y. Hinakubo, Org. Lett., 2003, 5, 1221-1223.

Novel and efficient Ni-mediated pinacol coupling of carbonyl compounds
L. Shi, C.-A. Fan, Y.-Q. Tu, M. Wang, F.-M. Zhang, Tetrahedron, 2004, 60, 2851-2855.