New asymmetric syntheses with boronic esters and fluoroboranes*
Donald S.Matteson
Department of Chemistry, Washington State University,
Pullman, WA 99164-4630, USA
Abstract: Efficient cleavage of sterically hindered boronic
esters of asymmetric diols to recover both the diol and a more reactive
borane derivative has been a challenging problem. A remarkable borosilicate
glass-catalyzed cleavage with thionyl chloride and imidazole proved
less useful than hoped for. Potassium bifluoride converts boronic esters
to diols and alkyltrifluoroborates. These with chlorosilanes yield alkyldifluoroboranes,
which with alkyl azides form secondary amines in high enantiopurity.
*Lecture presented at the XIth International Meeting
on Boron Chemistry (IMEBORON XI), Moscow, Russia, 28 July - 2 August
2002. Other presentations are published in this issue,
pp. 1157-1355.
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