Takai-Utimoto olefination

Takai-Utimoto olefination The chromium(ll)-mediated one-carbon homologation of aldehydes to the corresponding ( )-alkenyl halides. 452... 

Peterson olefination, Takai-Utimoto olefination, Tebbe olefination, Wittig reaction, Wittig reaction - Schlosser modification ... 

Indolylvinyl iodides III-55 and III-56 were synthesized using the Takai-Utimoto olefination [160], starting from the corresponding aldehydes, in moderate to high yields (Scheme 4.33). Unfortunately, when we tried this reaction cataly-Mc, only traces of the iodides were detected [161]. 

A variation of this reaction was developed in 1986 by Takai and Utimoto, in which geminal dihaloalkanes were added to aldehydes in a reaction mediated by chromium dichloride. This led to the stereoselective formation of the corresponding tran5-olefins 10 [12]. The major drawback of this method is the rather cumbersome access to the corresponding substituted dihalomethane compounds, which prevents a broad application of this reaction for synthesis. 

Okazoe, T., Takai, K., Utimoto, K. (E)-Selective olefination of aldehydes by means of gem-dichromium reagents derived by reduction of gem-diiodoalkanes with chromium(ll) chloride. J. 7 m. Chem. Soc. 1987, 109, 951-953. 

Takai, K. Kakiuchi,T. Kataoka,Y. Utimoto, K., A Novel Catalytic Effect of Lead on the Reduction of a Zinc Carbenoid with Zinc Metal Leading to a Geminal Dizinc Compound. Acceleration of the Wittig-Type Olefination with the RCHX2-TiCl4-Zn Systems by Addition of Lead. /. Org. 

Takai and Utimoto showed that reactions of aldehydes and a gem-diiodoalkane with chromium(II) chloride gave Wittig-type olefination products (Scheme 5.25) [35]. The notable points of this transformation are stereoselective ( )-alkene formation and chemoselective reaction with the aldehyde. Ketones are recovered unchanged. Instead of a gem-diiodoalkane, a-acetoxy bromide can also be used for this transformation [36]. 

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