Assisted by Hydrogen-Bond Donors: Cinchona Quaternary Salts as Privileged Chiral Catalysts for Phase-Transfer Reactions

Abstract

This review is devoted to the asymmetric phase-transfer reactions with the use of hybrid ammonium <i>Cinchona</i> catalysts supported by hydrogen-bond donor groups. Herein, we present a recent advancement of this type of catalysts in the field of biphasic reaction systems. The main emphasis was put on the advantages of additional functional groups present in the structure of the catalysts, such as: hydroxyl, amide, (thio)urea or squareamide.

Fast, highly enantioselective, and sustainable fluorination of 4-substituted pyrazolones catalyzed by amide-based phase-transfer catalysts

“…Detailed results can be seen in the ESI (Table S1†). Then, we turned our attention to the amide-based PTC, which was recently developed by Jurczak; 26 they have been successfully used in asymmetric alkylation of the imino glycine t -butylester, 27 epoxidation of α,β-unsaturated ketones, 28 α-chlorination, and α-alkylation of β-keto esters. 29 We were surprised to see that the ee value was increased to 37% when amide-based PTC 3g was used (Table 1, entry 3).…”

Base-free enantioselective SN2 alkylation of 2-oxindoles via bifunctional phase-transfer catalysis

“…In this context, we realised that phase-transfer catalysis, due to its operational simplicity and utility in mediating reactions involving charged intermediates, could be an excellent methodology for the enantioselective S N 2 alkylation of enolates derived from the 2-oxindole core [13][14][15][16][17][18][19][20][21][22][23]. In recent years, several examples regarding the alkylation of 3-subsituted-2-oxindoles, via asymmetric phase-transfer catalysis, have been reported [24][25][26][27][28][29][30].…”

Recognition of Chiral Carboxylates by Synthetic Receptors

“…New, precisely designed chiral receptors also open up a number of practical opportunities. One area that has been strongly explored by many research groups is asymmetric synthesis [8][9][10][11]. Despite many successes in this area, the practical derivation of homochiral compounds still remains a challenge.…”