Dialkylzinc-promoted Additions of Alkenylboronic Esters to Nitrones

Dialkylzinc-promoted Additions of Alkenylboronic Esters to Nitrones 

Chavant and Vallee have demonstrated dialkylzinc-promoted addition of pinacolyl alkenylboronates to nitrones (Equation 15) [85]. The reaction is tolerant of chloro and pivalate ester functionality on the alkenylboronate 85. Nitrones 86 derived from aromatic aldehydes with either N-benzyl or N-alkyl functionality were mainly used, although two examples employing nitrones derived from enolizable aliphatic aldehydes were also reported. The addition protocol is thought to rely on a transmetaUation of the pinacolyl alkenylboronates with dimethylzinc to give alkenylzinc species, which then undergo addition to give products such as 87. The use of diethylzinc resulted in some competitive direct ethylation of the nitrones. and NMR studies 

Nickelotalyzed Couplings of Boronic Acids with Alkynes and Imines 

5 For an overview of organoboronate and organoboron chemistry, see D. S. Matteson, Stereodirected Synthesis with Organoboranes, Springer-Verlag, Berlin, 1995. 

7 For an overview of organoborane chemistry, see A. Pelter, K. Smith, H. C. Brown, Borane Reagents, Academic, London, 1988. 

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