Hydrochloric Acid → 5-(5-(azidomethyl)-5-methyl-1,3-dioxan-2-yl)-1-methyl-4-nitro-1H-pyrazole

Participants

Reaction Steps

To a solution of (5-methyl-2-(1-methyl-4-nitro-1H-pyrazol-5-yl)-1,3-dioxan-5-yl)methanol (trans isomer) (248 mg, 1.02 mmol, intermediate 66) in dry DCM at 0° C. (10 mL) was added Et3N (0.20 mL, 1.53 mmol) followed by methanesulfonyl chloride (0.10 mL, 1.22 mmol). The reaction mixture was slowly warmed to room temperature over 1.5 hr. The mixture was re-cooled to 0° C. and 1 M aqueous HCl (5 mL) and DCM (20 mL) were added. The organic layer was washed with saturated aqueous NaHCO3 (10 mL) and water (10 mL), separated, dried over Na2SO4 and concentrated under reduced pressure to yield a colourless oil. This oil was dissolved in DMF (20 mL) and sodium azide (400 mg, 6.12 mmol) was added. The reaction mixture was heated at 140° C. for 18 hr behind a blast shield. The reaction mixture was cooled to room temperature and diluted with water (20 mL) and EtOAc (50 mL). The organic layer was washed with water (3×20 mL), separated, dried over Na2SO4 and concentrated under reduced pressure to give 5-(5-(azidomethyl)-5-methyl-1,3-dioxan-2-yl)-1-methyl-4-nitro-1H-pyrazole as a colourless solid (300 mg, quantitative over two steps). 1H NMR (400 MHz, CDCl3) δ 8.03 (s, 1H), 6.36 (s, 1H), 4.17 (s, 3H), 3.88 (s, 4H), 3.20 (s, 2H), 1.40 (s, 3H).

Provenance & Evidence