A New Class of Ammonium Ylid for [2,3]-Sigmatropic Rearrangement Reactions:  ene-endo-Spiro Ylids

Abstract

The first examples of sigmatropic rearrangements of ene-endo-spirocyclic, tetrahydropyridine-derived ammonium ylids are reported. Thus, spiro[6.7]-ylids rearrange primarily by a [2,3]-pathway, whereas the analogous [6.6]-ylids rearrange by [1,2]- and [2,3]-mechanisms in roughly equal proportions. This method serves as a rapid entry to the core of a range of alkaloids bearing a pyrrolo[1,2-a]azepine or octahydroindolizidine nucleus.

Modern Organic Synthesis with α-Diazocarbonyl Compounds

“…More recently, Sweeney has reported ene-endo-spirocyclic ylides as a new class of ammonium ylides for [2,3]-sigmatropic rearrangements. 597 As shown in Scheme 259, the tetrahydropyridine-derived spiro [6,7]-ylides were found to undergo mainly [2,3]-rearrangement with minor amounts (23%) of the [1,2]-Stevens rearrangement-derived product also observed. In contrast, the analogous spiro [6,6]-ylides were observed to provide roughly equal amounts of the [2,3]-and [1,2]rearrangement products.…”

“…More recently, Sweeney has reported ene-endo-spirocyclic ylides as a new class of ammonium ylides for [2,3]-sigmatropic rearrangements . As shown in Scheme , the tetrahydropyridine-derived spiro­[6,7]-ylides were found to undergo mainly [2,3]-rearrangement with minor amounts (23%) of the [1,2]-Stevens rearrangement-derived product also observed.…”

Transition metals in organic synthesis: Highlights for the year 2005

“…(108)) [737]. [2,3]-Sigmatropic rearrangements of spirocyclic ammonium ylides were described [738]. Rhodium catalyzed a diastereoselective sulfur ylide formation- [3,3]-sigmatropic rearrangement (Eq.…”

Lewis Acid Mediated Asymmetric [2,3]-Sigmatropic Rearrangement of Allylic Amines. Scope and Mechanistic Investigation

“…The rearrangement conditions were also attempted on the N-substituted 1,2,5,6-tetrahydropyridine 8 , which would give an efficient entry to substituted pyrrolidines (Scheme ). , Unfortunately, no product could be detected and only the starting material and ligand 3a were recovered. This can be rationalized by examining structure 9 , the deprotonated complex between 8 and 4a .…”