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. 2019 Jul 26;9(40):23295-23301.
doi: 10.1039/c9ra03135a. eCollection 2019 Jul 23.

Synthesis, functionalization, and isolation of planar-chiral pillar[5]arenes with bulky substituents using a chiral derivatization agent

Talal F Al-Azemi  1 , Mickey Vinodh  1 , Fatemeh H Alipour  1 , Abdirahman A Mohamod  1
Affiliations

Synthesis, functionalization, and isolation of planar-chiral pillar[5]arenes with bulky substituents using a chiral derivatization agent

Talal F Al-Azemi et al. RSC Adv. .

Abstract

Bulky perneopentyloxy-pillar[5]arene (Pillar-1) was synthesized and its conformational mobility was investigated using variable-temperature 1H NMR spectroscopy. The host-guest interactions between Pillar-1 and n-octyltrimethylammonium hexafluorophosphate (OMA) were investigated, and the formation of a 1 : 1 complex was revealed via 1H NMR. Planar-chiral isomers were synthesized via the reaction of a hydroxy-functionalized pillar[5]arene with chiral derivatization agent (S)-(+)-MTPA-Cl. The (Sp, R)-and (Rp, R)-forms of the pillar[5]arene diastereomers were isolated by HPLC, and their structures were analyzed by 19F NMR. HPLC measurements indicated that racemization did not take place at 40 °C for 72 h.

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Conflict of interest statement

There are no conflicts to declare.

Figures

Scheme 1
Scheme 1. Synthesis of perneopentyloxy-pillar[5]arene (Pillar-1), and X-ray crystal structure.
Fig. 1
Fig. 1. Variable-temperature 1H NMR spectra (600 MHz, toluene-d8) of Pillar-1.
Fig. 2
Fig. 2. 1H NMR spectra (600 MHz, CDCl3, 25 °C) of (a) 12 mM OMA, (b) 12 mM OMA and 14 mM Pillar-1, and (c) Pillar-1.
Fig. 3
Fig. 3. (a) Job's plot of Pillar-1 with OMA determined from 1H NMR titration in CDCl3 at 25 °C. (b) ES-MS spectrum of [(Pillar-1⊃OMA)-PF6]+.
Scheme 2
Scheme 2. Synthesis and derivatization of monohydroxy-pillar[5]arene with (S)-(+)-Mosher's acid chloride.
Fig. 4
Fig. 4. (a) HPLC traces of Pillar-4 before and after separation. Hexane/CHCl3 = 95/5 (vol%) was used as the eluent. (b) 19F NMR spectra.
See this image and copyright information in PMC

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