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Synlett 2008(12): 1913-1914  
DOI: 10.1055/s-2008-1067099
SPOTLIGHT
© Georg Thieme Verlag Stuttgart ˙ New York

Diketene

Nasrin Zohreh*
Faculty of Science, Tarbiat Modares University, P.O. Box 19396-4716, Tehran, Iran
e-Mail: Zohreh@modares.ac.ir;
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Publication History

Publication Date:
11 June 2008 (online)

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Introduction

Diketene (ketene dimer) is a reactive and versatile reagent in organic chemistry, which is used for the introduction of functionalized C2, C3, and C4 units into organic compounds. Diketene is mostly used for the preparation of ­acetoacetate esters and acetoacetamides, which are important synthetic intermediates used in agrichemical, pharmaceutical, and dyestuffs industries. [¹] Synthesis of five- and six-membered heterocycles by using diketene has been widely studied. [²] Reactions of the exocyclic olefin bond, for example photochemical [2+2] reactions, are other important reactions of diketene. [³]

In 1908, Wilsmore prepared the first pure sample of the ketene dimer via thermolysis of acetic anhydride or acetone with a hot platinum wire. [4] Although diketene is a small molecule (C4H4O2), in the absence of modern spectral techniques, it took 40 years to establish its structure definitely as 4-methylene-2-oxetanone. [5]

Nowadays, diketene is obtained by ketene dimerization in trickle towers, into which a liquid stream of the diketene is introduced in counter current to ketene at 35-40 ˚C (Scheme  [¹] ). [6]

Scheme 1

In general, depending on the applied reagents and reaction conditions, ring-opening of diketene results in formation of one of these four structures which usually undergo further reactions to reach the desired compounds. (Scheme  [²] ). [7]

Scheme 2