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(1R,2S)-N-Benzyl-N-[(2,2-dimethyl-1,3-dioxolan-4-yl)-(2-benzothiazolyl)methyl] Hydroxylamine

Department of Organic Chemistry. Faculty of Sciences-ICMA. University of Zaragoza. E-50009 Zaragoza. Spain
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Molecules 1998, 3(5), M79; https://doi.org/10.3390/M79
Received: 15 May 1998 / Published: 19 May 1998
(This article belongs to the Section Molbank Section of Molecules, 1997-2001)
Molecules 03 m79 i001
A cooled solution (-90°C) of benzothiophene (0.402 g, 3 mmol) in THF (10 mL) was treated with butyllithium (2 mL of a 1.6 M solution in hexanes, 3.2 mmol) under an inert atmopshere. The resulting solution was stirred at -80 °C for 15 min at which time the reaction mixture was cooled to -90 °C and treated via syringe with a solution of nitrone 1 (0.235 g, 1 mmol) in Et2O (10 mL), previously treated with Et2AlCl (1 mL of a 1.0 M solution in hexanes, 1 mmol) at ambient temperature for 5 min. The rate of the addition was adjusted so as to keep the internal temperature below -80°C. The reaction mixture was stirred for 30 min at -80 °C and then quenched with a 1N aqueous solution of sodium hydroxyde (10 mL). The mixture was stirred at ambient temperature for 10 min and diluted with ethyl acetate (15 mL). The organic layer was separated, and the aqueous layer was extracted with ethyl acetate (3 x 10 ml). The combined organic extracts were washed with brine and dried over magnesium sulfate, and the solvent was evaporated under reduced pressure to give the crude mixture of diastereomeric hydroxylamines. The NMR analysis of this mixture revealed a diastereoselectivity of 75%, the absolute configuration of the major adduct being confirmed by X-ray crystallography of the corresponding syn isomer [1]. Purification by column chromatography (hexane/diethyl ether 60:40) on silica gel afforded 3 as a white solid (0.241 g, 65%).
Mp 188-190°C
TLC (hexane/diethyl ether 60:40) Rf 0.37
[α]D20 = -31.2 (c 0.40, CHCl3)
1H NMR (CDCl3) δ 1.29 (s, 3H), 1.37 (s, 3H), 3.83 (d, 1H, J = 13.0 Hz), 3.95 (d, 1H, J = 13.0 Hz), 4.16 (dd, 1H, J = 5.1, 8.8 Hz), 4.19 (d, 1H, J = 8.5 Hz), 4.22 (dd, 1H, J =6.1, 8.8 Hz), 4.81 (ddd, 1H, J = 5.1, 6.1, 8.5 Hz), 6.36 (bs, 1H, ex. D2O), 7.24-7.53 (m, 7H), 7.92 (d, 1H, J = 8.0 Hz), 8.07 (d, 1H, J = 8.0 Hz).
13C NMR (CDCl3) δ 25.6, 27.1, 62.5, 68.0, 70.3, 77.0, 109.9, 119.4, 121.7, 123.3, 125.5, 126.2, 127.8, 128.6, 129.3, 136.0, 136.8, 170.4. Anal. Calcd. for C20H22N2O3S: C, 64.84; H, 5.99; N, 7.56. Found: C, 64.77; H, 6.18; N, 7.78.

Supplementary materials

Supplementary File 1Supplementary File 2Supplementary File 3

References and Notes

  1. Merino, P.; Franco, S.; Martinez, I.; Merchan, F. L.; Tejero, T. Unpublished results, Data is available from the authors.
  • Sample Availability: Available from the authors and MDPI: MDPI Reg. No. 15813
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