Synthesis of novel phase transfer catalysts derived from proline-mandelic acid/tartaric acid: their evaluation in enantioselective epoxidation and Darzen condensation

Abstract

Herein, we have described the synthesis of novel chiral cyclic phase transfer catalysts (PTCs). These catalysts are synthesized from proline, mandelic acid and tartaric acid by using simple synthetic methods with competitive yields. These chiral cyclic phase transfer catalysts have been characterized by 1 H NMR and 13 C NMR spectroscopy, IR spectroscopy and elemental analysis. The effectiveness of these novel chiral cyclic phase transfer catalysts was evaluated by applying them in the enantioselective epoxide synthesis from α, β unsaturated ketone (chalcone) and Darzens condensation. The obtained results show that the synthesized derivatives of proline, mandelic acid and tartaric acid are effectual as PTCs.

A New 2-Aminospiropyrazolylammonium Cation with Possible Uses in the Topical Areas of Ionic Liquids

“…These catalysts were synthesized from proline with competitive yields. They were designed and synthesized in such a way that out of the four sides, three sides of quaternary nitrogen are blocked with cyclic groups and one aromatic group at αor β-position to the nitrogen, whereas only one side is available for ion pairing with an anion [164]. These PTCs {(R)-1-((R)-hydroxy(phenyl)methyl)-5-azaspiro-[4.4]-nonan-5-ium bromide (a) and (R)-1-((R)-hydroxy(phenyl)methyl)-5-azaspiro- [4,5]-decan-5-ium bromide (b)} have the OH group at the β-position to the quaternary nitrogen, which can help lead to hydrogen bonding or attractive van der Waals interaction, which are advantageous for enhancing enantioselectivity (Figure 10).…”

“…The obtained results show that the synthesized derivatives of proline are as effective as PTCs since the reaction products have been obtained with high yields (87-90% and 82-85%) and excellent enantioselectivity (78.30-79.99 attractive van der Waals interaction, which are advantageous for enhancing enantioselectivity (Figure 10). Reproduced from [164]. Copyright 2019 SNCSC.…”

“…These catalysts were synthesized from proline with competitive yields. They were designed and synthesized in such a way that out of the four sides, three sides of quaternary nitrogen are blocked with cyclic groups and one aromatic group at α-or β-position to the nitrogen, whereas only one side is available for ion pairing with an anion [164]. These PTCs {(R)-1-Scheme 10.…”

Enantioselective Michael addition of malonic esters to benzalacetophenone by using chiral phase transfer catalysts derived from proline-mandelic acid/tartaric acid

“…By referring to this rational molecular design of chiral phase-transfer catalysts reported in literature, 7,8 we have recently reported the designing and synthesis of the chiral cyclic phase transfer catalysts derived from proline, mandelic acid and tartaric acid (I-VI, Figure 1) along with their successful evaluation for the effectiveness in enantioselective epoxidation and Darzens condensation. 9 To explore the further scope in enantioselective synthesis, we have utilized these PTCs for enantioselective Michael addition.…”

Synthesis of Methyl 4,6-Di-O-ethyl-α-d-glucopyranoside-Based Azacrown Ethers and Their Effects in Asymmetric Reactions

“…Since the 1990s, asymmetric PTC has emerged as a topic of scientific interest. Consequently, different chiral catalysts derived from cinchona alkaloids, amino acids, and 1,1 -bi-2-naphthol (BINOL) alongside macrocyclic compounds have been synthesized and applied [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35].…”