New Enantiomerically Pure Allylboronic Esters in Allyl Additions: Synthesis and NMR Investigation of Intermediates

Abstract

Enantiomerically pure allylboronic esters 1 + 2 with a stereogenic center α to the boron moiety can be obtained by a sigmatropic rearrangement of boron containing allyl alcohols. Allyl additions with the new reagents are highly selective, which was shown via the direct measurement of the diastereoisomeric ratio of the intermediates 5 + 6 by characteristic NMR chemical shifts. The observations are not limited to ester containing reagents, but holds also true for hydrocarbon side-chains (e.g. in 11 + 12) that were readily obtained by reducing the ester.

Key words

spectroscopy - allylations - boron - stereoselectivity

References

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CCDC-273337 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: [phone]; E-mail: [e-mail]].