Regio- and Enantioselective Monoborylation of Alkenylsilanes
was complete, the reaction mixture was passed through
a short silica gel column eluting with Et2O/hexane (20:80).
The crude mixture was further purified by flash column
chromatography (SiO2, Et2O/hexane, typically 0:100–4:96)
to give the corresponding monoborylation product 3a as
a colorless oil. The flash column chromatography should be
done within 5 min after the crude mixture was applied on
the silica gel surface; otherwise the products are obtained in
low yield. The ee value was determined by HPLC analysis
of the corresponding alcohol after NaBO3 oxidation of the
borylated product in comparison of the racemic sample.
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Acknowledgements
This work was financially supported by the Funding Program
for Next Generation World-Leading Researchers (NEXT
Program, No. G002) from the Japan Society for the Promo-
tion of Science (JSPS). We would like to thank Nippon
Chemical Industrial Co., Ltd. for the gift of BenzP*.
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