Asymmetric Phase‐transfer and Ion‐pair Organocatalyses

Synthesis, reactions and application of chalcones: a systematic review

“…Epoxy chalcone is an interesting heterocyclic intermediate molecule that is an essential building block in the ring opening reaction, which produces compounds with biological activity 173 and it is known as ethylene oxide or oxirane. 174 The epoxidation of chalcones has received a lot of attention in order to increase yield and enantiomeric excess (ee) values utilizing various types of catalysts [175][176][177][178][179] (Scheme 43). Several oxidants have been used in the epoxidation of chalcones, including hydrogen peroxide, dimethyl dioxirane, sodium hypochlorite, sodium peroxide, m-chloroperbenzoic acid, sodium chlorite, sodium perborate tetrahydrate, oxone, cyclohexylidene bishydro peroxide, trichloroisocyanuric acid, and hydrogen peroxide.…”

A chiral pentanidium and pyridinyl-sulphonamide ion pair as an enantioselective organocatalyst for Steglich rearrangement

“…The use of chiral cations such as quaternary ammonium salts in phase transfer catalysis (PTC) has been extensively reported in the literature. 2–5 Some prominent strategies that evolved from chiral cation PTC include asymmetric counteranion-directed catalysis, 6 chiral anion PTC, 7 and cation- or anion-binding catalysis. 8,9…”

“…The use of chiral cations such as quaternary ammonium salts in phase transfer catalysis (PTC) has been extensively reported in the literature. [2][3][4][5] Some prominent strategies that evolved from chiral cation PTC include asymmetric counteranion-directed catalysis, 6 chiral anion PTC, 7 and cation-or anion-binding catalysis. 8,9 The use of a chiral cation ion pair catalyst with transition metal binding to a ligand on the chiral cation (Ooi 10 and Peters 11 ) or a ligand on the achiral anion (Phipps 12,13 ) has been previously reported (Fig.…”

“…Asymmetric ion pair catalysis is a powerful strategy to achieve an enantioselective outcome in a reaction. 1,2 The chiral cation or anion can transmit stereochemical information to the reaction centres on their respective counterions, thus enabling enantioselectivity to be achieved. The use of chiral cations such as quaternary ammonium salts in phase transfer catalysis (PTC) has been extensively reported in the literature.…”