156731-36-1Relevant articles and documents
The tri-n-butyltin group as a novel stereocontrol element and synthetic handle in the aza-[2,3]-Wittig sigmatropic rearrangement
Anderson, James C.,Roberts, Craig A.
, p. 159 - 162 (1998)
The stereoselective trans hydrostannation of a non terminal alkynyl benzyl amine is described which furnished a tri-nbutyltin substituted aza- [2,3]-Wittig sigmatropic rearrangement precursor. Anionic rearrangement afforded a vinyl stannane product, in 71% yield with near complete control of diastereoselectivity. Subsequent transition metal catalysed carbon-carbon bond forming reactions gave potential precursors to novel unnatural amine acids in good to moderate yields.
The aza-[2,3]-Wittig sigmatropic rearrangement of acyclic amines: Scope and limitations of silicon assistance
Anderson,Flaherty,Swarbrick
, p. 9152 - 9156 (2007/10/03)
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 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 pKa > 22 in order for the initial anion to be reactive enough for rearrangement. Products 7, 29b-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.
