p-Toluenesulfonic acid → (2-(1-methyl-4-nitro-1H-pyrazol-5-yl)-1,3-dioxan-5-yl)methanol

Beteiligte Stoffe

Reaktionsschritte

To a solution of 2-methyl-4-nitro-pyrazole-3-carbaldehyde (718 mg, 4.63 mmol, intermediate 3) in toluene (100 mL) was added 2-(hydroxymethyl)propane-1,3-diol (700 mg, 6.73 mmol) followed by p-toluenesulfonic acid (88 mg, 0.463 mmol). The reaction mixture was heated at reflux for 18 hr whilst azeotropically removing the water. The mixture was cooled to room temperature and concentrated under reduced pressure. The residue was diluted with DCM (50 mL) and washed with a saturated aqueous NaHCO3 (50 mL). The organic layer was washed with water (20 mL) and brine (20 mL), separated, dried over Na2SO4 and concentrated under reduced pressure. Purification via silica gel column chromatography (0-100% EtOAc/isohexane) gave (2-(1-methyl-4-nitro-1H-pyrazol-5-yl)-1,3-dioxan-5-yl)methanol (trans isomer) as the first eluting isomer as a colourless solid (220 mg, 20%). 1H NMR (400 MHz, CDCl3) δ 8.02 (s, 1H), 6.42 (s, 1H), 4.34 (dd, J=11.6, 4.7 Hz, 2H), 4.12 (s, 3H), 3.81 (t, J=11.5 Hz, 2H), 3.56 (t, J=5.1 Hz, 2H), 2.53-2.38 (m, 1H), 1.67 (t, J=4.6 Hz, 1H).

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