Diastereoselective [2,3]-Sigmatropic Rearrangement of N-Allyl Ammonium Ylides

Abstract

A rapid and diastereoselective method was developed for the [2,3]-sigmatropic rearrangement of N-allyl ammonium ylides, affording products in up to 95% isolated yields and up to 97:3 dr; most of the desired products were formed within 1 minute. For the asymmetric reaction, a chiral auxiliary was introduced to the starting compound, affording the rearrangement product with high diastereoselectivities.

Progress in Catalytic Asymmetric Reactions with 7-Azaindoline as the Directing Group

“…At present, the main types of directing groups are as follows: 2-oxazolidone (A) [29][30][31][32][33][34][35][36][37][38][39][40], tetrahydropyrrole 2,5-dione (B) [41][42][43], pyrazole or 3,5-dimethylpyrazole (C or D) [44][45][46][47][48][49][50][51][52][53][54][55][56], and 8-aminoquinoline (E) [57][58][59][60][61][62][63][64][65]. They coordinate with metals to form stable five-or six-membered ring complexes that control the stereoselectivity of the reaction through a specific chiral environment (Scheme 1).…”

Asymmetric Organocatalytic [2,3]‐Wittig Rearrangement of Cyclohexanone Derivatives

“…[10] Our group previously reported an asymmetric [2,3]-Wittig rearrangement of oxindole, malonate and cyclopentanone derivatives, in addition to an example of a diastereoselective [2,3]-sigmatropic rearrangement of N-allyl ammonium ylides. [11][12][13][14] In 2006, Gaunt et al described the first asymmetric organocatalytic rearrangement on aliphatic cinnamyloxyketones. [15] Almost a decade later, Denmark obtained moderate results using phase-transfer catalysis on allyloxy oxindole derivatives (ee up to 54 %).…”

“…Despite its widespread use, the number of asymmetric catalytic methods is still limited [10] . Our group previously reported an asymmetric [2,3]‐Wittig rearrangement of oxindole, malonate and cyclopentanone derivatives, in addition to an example of a diastereoselective [2,3]‐sigmatropic rearrangement of N‐allyl ammonium ylides [11–14] …”

Chiral N,N′-dioxide/Mg(OTf)2 complex-catalyzed asymmetric [2,3]-rearrangement of in situ generated ammonium salts

“…There are some difficulties associated with the catalytic asymmetric [2,3]-rearrangement, such as the compatibility of all reactants with the catalyst 5a,f and the background reaction in the presence of the external base. 12 Herein, we wish to disclose our effort toward one-pot asymmetric [2,3]rearrangement of in situ formed allylic ammonium ylides. Chiral N,N 0 -dioxide/Mg(OTf) 2 (ref.…”