Kumada-Tamao group

The reaction of aryl electrophiles with organomagnesium compounds is known as Kumada or Kumada-Tamao-Corriu reaction. The most common leaving groups in the electrophile are halogen atoms and, among them, chlorine is the most wanted due to the good availability and the low price of aryl or heteroaryl chlorides. Unfortunately, the oxidative addition of a metal center to an aryl chloride is a difficult reaction and many efforts have been made to overcome existing limitations. 

K. Tamao, Y. Kiso, K. Sumitani, M. Kumada, AUcyl group isomerization in cross-coupling reaction of secondary alkyl grignard-reagents with organic halides in presence of nickel-phosphine complexes as catalysts, J. Am. Chem. Soc. 1972, 94, 9268. 

One of the first indications that higher valent silanes could be useful donors in palladium-catalyzed cross-coupling reactions was reported by Kumada and Tamao, when they observed that the dipotassium salt of pentafluorosilicate 70 could transfer its vinylphenyl group for the palladium-catalyzed coupling with iodobenzene at high temperature (Scheme 6). ... 

On the other hand, Kumada and Tamao disclosed that an organo(pentaflu-oro)silicate underwent desilylative coupling with iodobenzene in the presence of a palladium catalyst under rather drastic reaction conditions (Eq. 2) [9]. Although the nucleophilicity at the carbon atom having a silicate group is apparently enhanced, a czne-coupling product in addition to an zpso-coupling product is produced. 

Magar, S. S., Fuchs, P. L. Synthesis of tertiary alcohols via the use of the allyidimethylsilyl moiety as a latent hydroxyl group in the Kumada-Fleming-Tamao reaction. Tetrahedron Lett. 1991,32, 7513-7516. 

The Tamao-Kumada and Fleming oxidation reactions involve the oxidation of specific silyl groups to provide a hydroxyl group with retention of configuration.1... 

Shortly after the initial report by Tamao and Kumada, Fleming and co-workers reported a similar use of silanes as masked hydroxyl groups.4 In contrast, the Fleming... 

The Tamao-Kumada and Fleming oxidations have found wide synthetic utility in the oxidation of a variety of silyl groups.6,26 29 However, the true virtue of these reactions lies in the manner in which the silyl group is introduced into the molecule to be oxidized. A number of creative strategies have been developed for this process, some of which will be highlighted below. 

Radical cyclization has also proved to be a useful tool for the Shishido group in their syntheses of triptoquinones B and C and triptocallol.40 Triptoquinone B and C have been shown to exhibit inhibitory activity on interleukin-1 and are both candidates for the treatment of rheumatoid arthritis. Shishido has accomplished synthesis of all three of these compounds, implementing the radical cyclization of bromomethyldimethylsilyl ether 39, derived from optically enriched alcohol 38, to give 40. Finally, the Tamao-Kumada oxidation step provides the natural product, triptocallol (41). 

Mullins, R. J. JoUey, S. L. and Knapp, A. R. Tamao-Kumada-Flenting Oxidation. In Name Reactions for Functional Group Transformations , Li, J. J., Corey, E. J., eds. John Wiley Sons Hoboken, NJ, 2007, pp 237—247. (Review). 

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