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

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Reaction Steps

To a solution of 2-methyl-4-nitro-pyrazole-3-carbaldehyde (370 mg, 2.39 mmol, intermediate 3) in toluene (50 mL) was added 2-ethyl-2-(hydroxymethyl)propane-1,3-diol (315 mg, 2.35 mmol) followed by p-toluenesulfonic acid (20 mg, 0.10 mmol). The reaction mixture was heated at reflux for 36 hr whilst azeotropically removing the water. The mixture was cooled to room temperature and concentrated under reduced pressure. Purification via silica gel column chromatography (0-100% EtOAc/isohexane) gave (5-ethyl-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 (244 mg, 38%). 1H NMR (400 MHz, CDCl3) δ 8.02 (s, 1H), 6.38 (s, 1H), 4.16 (s, 3H), 4.02 (d, J=11.5 Hz, 2H), 3.97 (d, J=5.2 Hz, 2H), 3.42 (d, J=3.8 Hz, 2H), 1.90 (m, 3H), 0.99 (t, J=7.6 Hz, 3H).

Provenance & Evidence