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

Abstract

The Lewis acid catalyzed asymmetric [2,3]-rearrangement of quaternary ammonium ylides formed in situ from glycine pyrazoleamides and allyl bromides.

Recent advances in metal-catalysed asymmetric sigmatropic rearrangements

“…In 2020, the group of Feng reported a chiral N , N ′-dioxide–Mg( ii ) complex-catalysed enantioselective [2,3]-rearrangement of allylic ammonium salts generated in situ from glycine pyrazoleamides and allyl bromides (Scheme 29). 71 Such allylic ammonium salts possessed a pyrazoleamide group as the bidentate coordination site, which were readily subjected to deprotonation with external base i Pr 2 NH to form chiral Lewis acid complex bonded ammonium ylides. Then, these ammonium ylides would undergo a stereoselective [2,3]-rearrangement to deliver anti -configured α-amino acid derivatives 86 in high yields and excellent diastereo- and enantioselectivities.…”

Generation and [2,3]-Sigmatropic Rearrangement of Ammonium Ylides from Cyclopropyl Ketones for Chiral Indolizidines with Bridgehead Quaternary Stereocenters

“…This protocol was also applicable for the preparation of allyl-substituted indolizidines . As shown in Scheme , the reaction of the N -allyl substrate proceeded smoothly, providing 2r in 50% yield with an excellent level of chirality transfer.…”

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).…”