Diastereoselective synthesis of substituted prolines via 5-endo-trig cyclisations of aza-[2,3]-Wittig sigmatropic rearrangement products.
The major diastereoisomers of aza-[2,3]-Wittig sigmatropic rearrangement products from alpha-amino acid derivatives are susceptible to a rare nucleophilic 5-endo-trig cyclisations of an amine onto a non-conjugated vinylsilane in high yield and complete diastereocontrol. Five examples are presented, with cyclisation yields between 35 and 87%. A rationale for the stereoselectivity of the cyclisation is forwarded based upon the steric control factors that have been documented for the aza-[2,3]-Wittig sigmatropic rearrangement. A discussion of the mechanism in the context of the reaction conditions is also presented. Oxidation of the silyl group to a hydroxyl group and complete removal were demonstrated for synthetic utility. (C) 2010 Elsevier Ltd. All rights reserved.
|Title:||Diastereoselective synthesis of substituted prolines via 5-endo-trig cyclisations of aza-[2,3]-Wittig sigmatropic rearrangement products|
|Keywords:||5-endo-trig, Cyclisation, Aza-[2,3]-Wittig, Proline, Sigmatropic rearrangement, Vinyl silane, AMINO-ACID DERIVATIVES, ENANTIOSELECTIVE TOTAL-SYNTHESIS, AZA-WITTIG REARRANGEMENT, ALPHA-ALKYLATION, <2,3>-WITTIG REARRANGEMENT, NITROGEN-HETEROCYCLES, ASYMMETRIC-SYNTHESIS, RING-CLOSURE, CHIRALITY, VINYLAZIRIDINES|
|UCL classification:||UCL > School of BEAMS > Faculty of Maths and Physical Sciences
UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry
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