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Synlett 2009(16): 2655-2658  
DOI: 10.1055/s-0029-1217973
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

A Facile Route towards the Preparation of Ultra-Long-Chain Amidosulfobetaine Surfactants

Zonglin Chua,b, Yujun Feng*a
a Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610041, P. R. of China
b Graduate School of Chinese Academy of Sciences, Beijing 100049, P. R. of China
Fax: +86(28)85236874; e-Mail: yjfeng@cioc.ac.cn;
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Publication History

Received 2 June 2009
Publication Date:
09 September 2009 (online)

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Abstract

A series of novel, ultra-long-chain amidosulfobetaine surfactants were prepared by amidation of ultra-long-chain fatty acids directly with N,N-dimethyl-1,3-propanediamine in the absence of solvents, followed by quaternization of the intermediates with 1,3-propanesultone in ethyl acetate.

Key words

ultra-long-chain surfactants - amidosulfobetaine surfactants - worm-like micelles - self-assembly aggregates - facile synthesis

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Preparation of 3-(N-behenamidopropyl-N,N-dimethyl-ammonium) propanesulfonate (C22AMP3SB); Typical Procedure: Behenic acid (200 mmol, 68.12 g), N,N-dimethyl-1,3-propanediamine (DMPDA; 300 mmol, 30.65 g), and NaF (0.30 g) were introduced into a three-necked flask. The reaction mixture was refluxed at 165 ˚C under N2 atmosphere for 6 h, during which the by-product H2O was absorbed continuously by Al2O3 placed in the solvent still head. Afterwards, further DMPDA (100 mmol, 10.22 g) was added and the reaction was continued for another 5 h. The excess of DMPDA was removed and the residues were washed with acetone [4 × 200 mL containing H2O (10 mL) to remove NaF]. The purified product was dried under vacuum at 40 ˚C for 24 h to give N-behenamidopropyl-N,N-dimethylamine (C22AMPM) with a purity 99.86% (HPLC) and a yield of 92.41% (78.50 g). ¹H NMR (300 MHz, CD3OD): δ = 0.90 (t, J = 6.66 Hz, 3H), 1.29 (m, 36H), 1.59-1.70 (m, 4H), 2.17 (t, J = 7.42 Hz, 2H), 2.25 (s, 6H), 2.35 (m, 2H), 3.19 (t, J = 6.94 Hz, 2H); ¹³C NMR (75 MHz, CD3OD): δ = 14.42, 23.72, 27.05, 28.20, 30.29-30.74, 33.06, 37.17, 38.57, 45.42, 58.21, 176.26; HRMS (ESI): m/z [M + H]+ calcd for C27H57N2O: 425.4465; found: 425.4444; Anal. Calcd for C27H56N2O: C, 76.35; H, 13.29; N, 6.60. Found: C, 76.13; H, 13.26; N, 6.45. In the next step, C22AMPM (20 mmol, 8.50 g), 1,3-propanesultone (30 mmol, 3.66 g), and EtOAc (100 mL) were introduced to a round-bottom flask. After 10 h of reflux (˜80 ˚C), the white precipitate was filtered from the solution and washed with EtOAc (3 × 200 mL) and Et2O (3 × 200 mL) successively. The product was dried under vacuum at 40 ˚C for 24 h, to give the final product C22AMP3SB with purity 99.35% (HPLC) and a yield of 84.52% (9.24 g). Detailed preparation procedures and structural characterizations of other amidosulfobetaines are available in the supporting information. ¹H NMR (300 MHz, CD3OD): δ = 0.90 (t, J = 6.66 Hz, 3H), 1.29 (m, 36H), 1.60 (m, 2H), 1.98 (m, 2H), 2.18-2.23 (m, 4H), 2.87 (t, J = 6.65 Hz, 2H), 3.10 (s, 6H), 3.25-3.36 (m, 4H), 3.53 (m, 2H); ¹³C NMR (75 MHz, CD3OD): δ = 14.39, 19.86, 23.70, 23.99, 26.90, 30.99-30.73, 33.05, 37.13, 48.71, 51.56, 63.26, 63.81 176.56; HRMS (ESI): m/z [M + Na]+ calcd for C30H62N2NaO4S: 569.4323; found: 569.4318; Anal. Calcd for C30H62N2O4S˙0.7H2O: C, 64.40; H, 11.42; N, 5.01; S, 5.73. Found: C, 64.51; H, 11.35; N, 5.06; S, 5.47.

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Data for UC18AMP3SB: ¹H NMR (300 MHz, CD3OD): δ = 0.93 (t, J = 6.70 Hz, 3H), 1.32-1.36 (m, 20H), 1.58 (m, 2H), 2.02-2.06 (m, 6H), 2.21-2.26 (m, 4H), 2.90 (t, J = 6.72 Hz, 2H), 3.13 (s, 6H), 3.28-3.39 (m, 4H), 3.56 (m, 2H), 5.37 (m, 2H); ¹³C NMR (75 MHz, CD3OD): δ = 14.47, 19.88, 23.72, 23.92, 26.91, 28.12, 28.14, 30.24-30.84, 33.04, 37.09, 37.14, 48.56, 51.48, 63.21, 63.80, 130.77, 130.87, 176.59; HRMS (ESI): m/z [M + Na]+ calcd for C26H52N2NaO4S: 511.3540; found: 511.3531; Anal. Calcd for C26H52N2O4S˙1.2H2O: C, 61.18; H, 10.74; N, 5.49; S, 6.28. Found: C, 61.28; H, 10.73; N, 5.45; S, 6.27.