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Synfacts 2019; 15(05): 0523
DOI: 10.1055/s-0037-1611507
Metals in Synthesis
© Georg Thieme Verlag Stuttgart · New York

The Takai Olefination: Simple Access to E-Alkenyl Halides

Contributor(s):
Paul Knochel
,
Ferdinand H. Lutter
Takai K. * Nitta K, Utimoto K. Kyoto University, Japan
Simple and Selective Method for Aldehydes (RCHO) → (E)-Haloalkenes (RCH:CHX) Conversion by means of a Haloform-Chromous Chloride System.

J. Am. Chem. Soc. 1986;
108: 7408-7410
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Further Information

Publication History

Publication Date:
15 April 2019 (online)

 
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Key words

olefination - stereoselectivity - chromium catalysis

Significance

In 1986 Takai and co-workers developed a simple procedure for the stereoselective preparation of E-alkenyl halides from various aldehydes by using an excess of CrCl2 together with a haloform. The selectivity was dependent on the corresponding haloform and decreased in the order Cl > Br > I.


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Comment

The mild reaction conditions enable highly chemoselective transformations. Thus, the olefination of an aldehyde proceeds smoothly in the presence of ketone moieties. Given the unique chemo- and stereoselectivity, several modifications and improvements of this method have been published over the years.


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