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Claisen rearrangements of allylic and propargylic alcohols prepared by an N-Boc-2-acyloxazolidine methodology - Application to the synthesis of original chiral building blocks

par Agami, C;Couty, François;Evano, Gwilherm
Référence European Journal of Organic Chemistry, 2002, 1, page (29-38)
Publication Publié, 2002

Article révisé par les pairs

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Résumé :

Stereodefined alkenols prepared in two steps from a Weinreb amide derived from (R)-phenylglycinol undergo highly stereoselective Claisen rearrangements. The masked aldehyde moiety of the produced N-Boc-alkenyloxazolidines can then be recovered and reduced without epimerization, to yield new enantiopure chiral building blocks. Alternatively, epoxidation of these N-Boc-2-alkenyloxazolidines by a well-established intramolecular bromocarbamation involving the Boc protecting group occurs stereoselectively. The resulting α,β-epoxyoxazolidines are then transformed into trisubstituted stereodefined cyclopropanes. Claisen rearrangements of propargylic alcohols, on the other hand, stereoselectively give α-allenyloxazolidines. These compounds follow a different pathway to α-alkenyloxazolidines as regards bromocarbamation. An original route to enantiopure 3-hydroxy-4-phenylpiperidine was found in the course of this study.