Experimental and computational studies on the Cinchona anchored calixarene catalysed asymmetric Michael addition reaction

Abstract

Lower-rim Cinchona anchored calix[4]arene cationic catalysts were developed for asymmetric Michael addition of acetylacetone to β-nitrostyrenes. The desired Michael adducts formed with high yields and enantioselectivities. Density functional theory investigations...

α‐Methylbenzylamine Functionalized Crown‐Ether‐Appended Calix[4]arene Phase Transfer Catalyst for Enantioselective Henry Reaction

“…In this letter, we wish to report noteworthy progress based on our initial investigations on the design of new α‐methylbenzylamine functionalized crown‐ether‐appended calix[4]arenes PTCs (V I and VII ) for asymmetric nitroaldol reaction with high yield (>99 %) and enantiomeric excess (99.8 %) under ambient conditions with a scant catalytic amount (0.1 mol %). Mechanistically, our studies suggested that calixarene‐anchored amines served as bifunctional catalysts via hydrogen bonding interactions with the Michael acceptor and donor through the N−H and phenolic oxygen, respectively [19] . With this understanding, we predicted that PTCs VI & VII could be able to favor the transition states involving aldehyde and nitromethanide during chirality transfer.…”

“…Mechanistically, our studies suggested that calixarene-anchored amines served as bifunctional catalysts via hydrogen bonding interactions with the Michael acceptor and donor through the NÀ H and phenolic oxygen, respectively. [19] With this understanding, we predicted that PTCs VI & VII could be able to favor the transition states involving aldehyde and nitromethanide during chirality transfer. Additionally, selective binding of K + with crown ether generates chiral ion pairs, [20] augmenting enantioselectivities and rate of reaction (See Supporting Information for 39 K NMR).…”

Fluorescein-appended calixarene-functionalized supramolecular AIE-active liquid crystalline materials for self-assembly and bio-imaging applications

“…[12][13][14][15] Calixarene core contains p-electronic conjugative systems with hydrophobic and hydrophilic sides, which provides a good platform for further functionalization by various groups and moieties to enhance the activity in various applications. 16 The literature presents several supramolecular LCs based on the calix [4]arene core, [17][18][19][20] however, very few display fluorescent properties. Previously, our research group reported fluorescent calix [4]arene functionalized LCs and explored their optical, gelation in OLED device fabrication.…”

Enantioselective Alkylation of Glycine Imines Using a Cinchona-Functionalized Crown Ether-Strapped Calixarene Phase-Transfer Catalyst

“…Finally, the reactions of bromo derivatives 1 and 3 with cinchonidine in dry toluene at 100 °C delivered corresponding off-white crystalline VI and VII in excellent yields. Catalysts IV and V were synthesized via our recently reported procedure …”

“…Catalysts IV and V were synthesized via our recently reported procedure. 27 Our studies started with an examination of asymmetric αalkylation of model substrate N-(diphenylmethylene)glycine ethyl ester 4a with benzyl bromide 5a to form optically active N-(diphenylmethylene)phenylalanine ethyl ester 6a. Initially, the catalysts I−VII were tested at 1 mol % catalyst loading in toluene (Table 1) using 50% aq NaOH at RT to afford the desired α-benzylated product 6a.…”