Enantiodivergent hydroboration reactions of a racemic allenylsilane with diisopinocampheylborane and Curtin-Hammett controlled double asymmetric crotylboration reactions of (S)-E-αphenyldimethylsilyl(ddiisopinocampheyl)-crotylborane.
The enantiodivergent hydroboration reactions of racemic allenylsilane (±)-4with (dIpc)2BH and subsequent crotylboration of achiral aldehydes with the product crotylborane (S)-E-5at -78 °C provide (E)-δ-silyl-anti-homoallylic alcohols6in 71-89% yield and with 93-96% ee. Intriguingly, mismatched double asymmetric crotylboration reactions of enantioenriched chiral aldehydes20with (S)-E-5proceed under Curtin-Hammett control to giveanti-β-hydroxylcrotylsilanes24as the only products.
Department of Chemistry, The Scripps Research Institute, Florida, 130 Scripps Way, Jupiter, FL 33458, USA.
Ming
M
Chen
William R
WR
Roush
Curtin–Hammett control; Enantiodivergent hydroboration; Mismatched double asymmetric; crotylboration