Applications of Organoborates

Applications of Organoborates. Electrophile-induced rearrangements of four coordinate borate salts now provide a major proportion of the new synthetic applications of organoboron compounds. Many of these procedures utilize trialkylal-kynylborates, the basic reaction of which is outlined in reaction (6), 

Takano, K. Ogasawara, and I. Nagayama, T. Kutsuma, Synthetic Comm., 1976, 6, 349. A. Kumar, A. Singh, and D. Devaprabhakara, Tetrahedron Letters, 1976, 2177. 

An alternative route to trialkylalkynylborate salts is shown in reaction (7).  

Some types of vinylboranes are readily hydrolysed in aqueous base if first converted into a borate complex by addition of Bu Li. The iodine-induced formation of substituted alkenes from vinylborates has been applied in the conversion of (75) into (76), a prostaglandin model.Bromine induces coupling of the aryl groups in borates such as (77), though yields of coupled product e.g. 78) are moderate.  

Utimoto, Y. Yabuki, K. Okada, and H. Nozaki, Tetrahedron Letters, 1976, 3969. 

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Applications of Organoborates. Details have appeared of reactions of tri-alkylethenylborates with aldehydes, epoxides, and iodine, respectively useful for syntheses of 1,3-diols, 1,4-diols, and alk-l-enes. Trialkylalkynylborates cannot normally be acylated successfully because of cyclization and further rearrangement of. the initial intermediates. However, the trialkylalkynylborates... 

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