Convenient multigram synthesis of monodisperse oligo(ethylene glycols): Effective reaction monitoring by infrared spectroscopy using an attenuated total reflection fibre optic probe

Tetrahedron Letters

Volumn 50, Issue 47, 2009, Pages 6469-6471

  Lumpi, Daniel ^a   Braunshier, Christian ^a   Hametner, Christian ^a   Horkel, Ernst ^a   Zachhuber, Bernhard ^a   Lendl, Bernhard ^a   Fr̈hlich, Johannes ^a  

^a VIENNA UNIVERSITY OF TECHNOLOGY   (Austria)

Author keywords

ATR IR sensor spectroscopy; In situ reaction monitoring; Monodisperse OEG PEG; Oligo(ethylene glycols); Trityl cleavage

Indexed keywords

ETHYLENE GLYCOL;

ARTICLE; DEPROTECTION REACTION; FIBER OPTICS; HYDROGENOLYSIS; INFRARED SPECTROSCOPY; REACTION OPTIMIZATION; REACTION TIME; SENSOR; SYNTHESIS;

EID: 78649863740     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.tetlet.2009.09.010     Document Type: Article

References (19)

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17. Synthesis of 1,1,1,27,27,27-hexaphenyl-2,5,8,11,14,17, 20,23,26-nonaoxahep-tacosane 3b. Under argon, a 4-neck round bottom flask equipped with mechanical stirrer, reflux condenser, thermometer (and dropping funnel, respectively) and the ATR-IR Probe inlet was charged with sodium hydride (12.00 g, 500 mmol, 2.5 equiv) and dry THF (500 mL). To the well stirred suspension was added a solution of mono-trityl protected glycol 1a (139.38 g, 400 mmol, 2.0 equiv) in dry THF (500 mL) at room temperature. After completion of the reaction according to IR-monitoring (4 h), the mixture was cooled to 0 °C and a solution of di-tosylated glycol 2b (100.52 g, 200 mmol, 1.0 equiv) in dry THF (500 mL) was added. The temperature was adjusted to 40 °C and the suspension was stirred for 80 h. For workup, the reaction mixture was poured onto ice water (1200 mL)/chloroform (800 mL). The phases were separated and the aqueous phase was extracted with chloroform (500 mL). The combined organic layers were washed with brine (500 mL) and dried over sodium sulfate. After removing the solvent under reduced pressure, the title compound was obtained as a clear, slightly orange, viscous oil. Yield: 165.36 g (97%). 1H NMR (200 MHz, DMSO-d6) δ = 7.48-7.15 (m, 30 H), 3.67-3.39 (m, 28 H), 3.06 (t, J = 4.8 Hz, 4 H); 13C APT NMR (50 MHz, DMSO-d6) δ = 143.8 (s), 128.2 (d), 127.8 (d), 126.9 (d), 85.9 (t), 70.1 (t), 69.9 (t), 69.85 (t), 69.82 (t), 69.77 (t), 69.7 (t), 63.0 (t). Anal. Calcd for C54H62O9 (855.09): C, 75.85; H, 7.31. Found: C, 76.15; H, 7.15;
18. Synthesis of 3,6,9,12,15,18,21-heptaoxatricosane-1,23-diol 4b. Compound 3b (128.26 g, 150 mmol) was stirred with 80% acetic acid (1200 mL) at 40 °C. After 2 h the reaction was completed according to HPLC analysis. The mixture was allowed to cool to room temperature and poured onto ice water (600 mL). The precipitate was filtered off over a glass sinter funnel. The filtrate was concentrated under reduced pressure leaving a cloudy oil. The crude product was mixed with cold water (500 mL) and the suspension was again filtered over the same glass sinter funnel, still containing the bed of triphenylmethanol formed during the first filtration. The filter cake was washed with cold water, giving 77.02 g (99%) of pure triphenylmethanol after drying at 40 °C/15 mbar. The solvent of the filtrate was removed under reduced pressure (0.05 mbar) to afford the title compound as a clear, slightly orange oil. Yield: 53.20 g (96%). 1H NMR (200 MHz, CDCl3) δ = 3.62-3.38 (m, 32 H), 3.30 (br s, 2 H). 13C NMR (50 MHz, CDCl3) δ = 72.2, 70.15, 70.10, 69.9, 61.1. Anal. Calcd for C16H34O9 (370.44): C, 51.88; H, 9.25. Found:C, 51.81; H,9.34;
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