The aza-[2,3]-Wittig sigmatropic rearrangement of acyclic amines: Scope and limitations of silicon assistance.
J ORG CHEM
9152 - 9156.
The inclusion of a C-2 trialkylsilyl substituent into allylic amine precursors allows the base-induced aza-[2,3]-Wittig sigmatropic rearrangement to proceed in-excellent yield and diastereoselectivity. The rearrangement precursors require a carbonyl-based nitrogen protecting group that must be stable to the excess of strong base required for the reaction. The N-Boc and N-benzoyl group are very good at stabilizing-the product anion and initiating deprotonation. The migrating groups (G) need to stabilize the intial anion by resonance and require G-CH3 pK(a) > 22 in order for the initial anion to be reactive enough for rearrangement. Products 7, 20b-d,f,g, and 23 are formed with high (10-20:1) anti diastereoselectivity. Product 23 containing the morpholine amide group is useful for preparing other carbonyl derivatives.
|Title:||The aza-[2,3]-Wittig sigmatropic rearrangement of acyclic amines: Scope and limitations of silicon assistance|
|Keywords:||ENOLATE CLAISEN REARRANGEMENT, AZA-WITTIG REARRANGEMENT, <2,3>-WITTIG REARRANGEMENT, <2,3>WITTIG REARRANGEMENT, INVERSION, ACIDS, STEREOCONTROL, CONFIGURATION, CYCLIZATIONS, AZIRIDINES|
|UCL classification:||UCL > School of BEAMS
UCL > School of BEAMS > Faculty of Maths and Physical Sciences
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