Dialkyl Imidazolium Benzoates - Room Temperature Ionic Liquids Useful in the Peracetylation and Perbenzoylation of Simple and Sulfated Saccharides

Abstract

Dialkyl imidazolium benzoates, room temperature ionic liquids including 1-ethyl-3-methyl imidazolium benzoate, 1-butyl-3-methyl imidazolium benzoate and 1-hexyl-3-methyl imidazolium benzoate were used in the peracetylation and perbenzoylation of several simple and sulfated carbohydrates. Organic solvents and catalysts were not required in the syntheses and these ionic liquids gave excellent yields in short reaction times.

Key words

carbohydrates - sulfated sugars - acylation - ionic liquids - microwave

References

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• 13 NMR data: [emIm][ba]: ¹H NMR (DMSO, 400 MHz) δ 1.39 (3 H, t, CH₃), 3.84 (3 H, s, CH₃), 4.16 (2 H, q, CH₂), 7.44 (2 H, m, Ph), 7.54 (1 H, m, Ph), 7.70 (1 H, t, J = 1.7 Hz, Im), 7.79 (1 H, t, J = 1.8 Hz, Im), 7.92 (2 H, m, Ph), 9.25 (1 H, s, Im). [bmIm][ba]: ¹H NMR (DMSO, 400 MHz) δ 0.91 (3 H, t, CH₃), 1.28 (2 H, m, CH₂), 1.78 (2 H, m, CH₂), 3.88 (3 H, s, CH₃), 4.20 (2 H, t, CH₂), 7.49 (2 H, m, Ph), 7.60 (1 H, m, Ph), 7.77 (1 H, t, J = 1.7 Hz, Im), 7.84 (1 H, t, J = 1.7 Hz, Im), 7.96 (2 H, m, Ph), 9.36 (1 H, s, Im). [hmIm][ba]: ¹H NMR (DMSO, 400MHz) δ 0.84 (3 H, t, CH₃), 1.24 (6 H, m, 3 CH₂), 1.76 (2 H, m, CH₂), 3.84 (3 H, s, CH₃₎, 4.14 (2 H, t, CH₂), 7.16 (1 H, t, J = 1.7 Hz, Im), 7.47 (2 H, m, Ph), 7.59 (1 H, m, Ph), 7.87 (1H, t, J = 1.8 Hz, Im), 7.93 (2 H, m, Ph), 9.24 (1 H, s, Im).
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16

NMR data: Compound (1): ¹H NMR (D₂O, 400 MHz) δ 3.58 (1 H, dd, J = 7.8 Hz, 9.2 Hz, H-2), 3.62 (1 H, ddd, J = 2.1 Hz, 5.6 Hz, 9.8 Hz, H-5), 3.80 (2 H, m, H-3, H-6b), 3.95 (1 H, dd, J = 2.1 Hz, 12.5 Hz, H-6a), 4.24 (1 H, dd, J = 9.0 Hz, 9.8 Hz, H-4), 4.97 (1 H, d, J = 7.9 Hz, H-1), 7.01-7.32 (5 H, m, Ph). Compound (2): ¹H NMR (D₂O, 400 MHz) δ 3.43-3.51 (3 H, m, H-2, H-3, H-4), 3.69 (1 H, ddd, J = 2.0 Hz, 5.8 Hz, 7.6 Hz, H-5), 4.18 (1 H, dd, J = 5.8 Hz, 11.0 Hz, H-6b), 4.39 (1 H, dd, J = 2.0 Hz, 11.0 Hz, H-6a), 4.91 (1 H, d, J = 7.4 Hz, H-1), 7.00-7.32 (5 H, m, Ph). Compound (8): ¹H NMR (D₂O, 400 MHz) δ 2.04 (3 H, s, OAc), 2.05 (3 H, s, OAc), 2.06 (3 H, s, OAc), 4.98 (1 H, ddd, J = 2.5 Hz, 6.6 Hz, 9.7 Hz, H-5), 4.37 (1 H, dd, J = 6.6 Hz, 12.2 Hz, H-6b), 4.42-4.49 (2 H, m, H-4, H-6a), 5.14 (1 H, dd, J = 8.0 Hz, 9.7 Hz, H-2), 5.27 (1 H, d, J = 8.0 Hz, H-1), 5.38 (1 H, t, J = 9.7 Hz, H-3), 7.00-7.32 (5 H, m, Ph). Compound (9): ¹H NMR (D₂O, 400 MHz) δ 2.03 (3 H, s, OAc), 2.08 (3 H, s, OAc), 2.09 (3 H, s, OAc), 4.09-4.21 (3 H, m, H-5, H-6a, H-6b), 5.12 (1 H, t, J = 9.5 Hz, H-4), 5.21 (1 H, dd, J = 8.0 Hz, 9.5 Hz, H-2), 5.33 (1 H, d, J = 8.0 Hz, H-1), 5.42 (1 H, t, J = 9.5 Hz, H-3), 7.05-7.36 (5 H, m, Ph). Compounds (10) and (11): ¹H NMR (D₂O, 400 MHz) δ 4.39-4.69 (5.25 H, m, H-5α,β, H-6aα,β, H-6bα,β), 5.69 (1 H, dd, J = 3.7 Hz, 10.3 Hz, H-2α), 5.80-5.90 (2.5 H, m, H-4α, H-2β, H-4β), 6.05 (0.75 H, t, J = 9.4 Hz, H-3β), 6.30 (0.75 H, d, J = 7.9 Hz, H-1β), 6.33 (1 H, t, J = 10.0 Hz, H-3α), 6.85 (1 H, d, J = 3.7 Hz, H-1α), 8.18-7.27 (25 H, m, Ar).

17

MS (ESI): 461 [M + H⁺].