Highly (E)-Selective BF3·Et2O-Promoted Allylboration of Chiral Nonracemic α-Substituted Allylboronates and Analysis of the Origin of Stereocontrol
M Chen, WR Roush - Organic letters, 2010 - ACS Publications
M Chen, WR Roush
Organic letters, 2010•ACS Publications… 9c In connection with an ongoing problem in natural product synthesis, we had occasion to
explore Lewis acid promoted allylborations of enantioenriched R-substituted allylboronates.
We found and report herein that (E)-δ-methyl-homoallylic alcohols 2 are obtained in good
yields and excellent enantioselectivities from BF3·Et2O-promoted allylboration reactions of
1.In addition, we have found that δ-chloro-substituted homoallylic alcohols 14 can also be
obtained in good yield and 3-6:1 (… We were intrigued by the possibility that …
explore Lewis acid promoted allylborations of enantioenriched R-substituted allylboronates.
We found and report herein that (E)-δ-methyl-homoallylic alcohols 2 are obtained in good
yields and excellent enantioselectivities from BF3·Et2O-promoted allylboration reactions of
1.In addition, we have found that δ-chloro-substituted homoallylic alcohols 14 can also be
obtained in good yield and 3-6:1 (… We were intrigued by the possibility that …
δ-Methyl-substituted homoallylic alcohols 2 were prepared in 71−88% yield, E:Z >30:1 and 93% to >95% ee via BF3·Et2O-promoted allylboration with α-Me-allylboronate 1. The origin of high (E)-selectivity is proposed.
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