Diastereo- and enantiomerically pure allylboronates: their synthesis and scope |
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Authors: | Pietruszka Jörg Schöne Niklas Frey Wolfgang Grundl Li |
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Affiliation: | 1. Institut für Bioorganische Chemie der Heinrich‐Heine‐Universit?t Düsseldorf im Forschungszentrum Jülich, Stetternicher Forst, Geb. 15.8, 52426 Jülich, Germany, Fax: (+49)?2461‐616196;2. Institut für Organische Chemie der Universit?t Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany |
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Abstract: | Allylboronates are highly attractive reagents for allyl additions. Enantiomerically pure, stable reagents with a stereogenic centre in alpha-position to boron are especially versatile, albeit often difficult to synthesize. Starting from boron-containing allyl alcohols 6 and 7, which are discussed in detail herein, a set of reagents were obtained via [3,3]-sigmatropic rearrangements and consecutive transformations in the side chain. The configurations could be established first by chemical correlation, but also by X-ray crystallography (16, 18, 34, and 39). Allyl additions were performed resulting in the formation of predominantly (Z)-configured homoallylic alcohols (31, 43-45) with high enantiomeric excess. Detailed investigations on the matched-mismatched interaction between the reagents 15/16 (and ent-15/ent-16, respectively) and isopropylidene glyceraldehyde 42d are presented. |
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Keywords: | allylation asymmetric synthesis boron rearrangement sigmatropic reactions |
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