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A. A solution of 3-amino-4-bromopyrazole (2.0 g, 12 mmol) and 1 ,1 ,3,3- tetramethoxypropane (4.1 mL, 25 mmol) in acetic acid (5 mL) was heated at reflux for 4 h. Water (2 mL) was added and the mixture heated at reflux for a further 0.5 h, allowed to cool to ambient temperature and concentrated in vacuo. The residue was triturated in methanol. The solid thus obtained was washed with cold methanol, ethyl acetate, and hexanes to provide 3-bromopyrazolo[1 ,5-a]pyrimidine as a brownish solid in 39% yield (0.953 g): 1H NMR (300 MHz, DMSO-d6) ￡9.13 (d, J = 6.5 Hz, 1 H), 8.61 (s, 1 H), 8.35 (s, 1 H), 7.19-7.02 (m, 1 H); MS (ES+) m/z 197.9 (M + 1), 199.9 (M + 1).
With hydrogenchloride; In ethanol; water; at 20 - 71℃;
A solution of the amino-bromo-pyrazole obtained above, dissolved in EtOH (23OmL) was treated with cone. HCl (13.6mL) followed by tetra-methoxypropane (3 ImL) at rt. The resulting turbid solution was heated to 71C for 2h, during this time, the reaction mixture turned into a suspension and a solid started separating out. The reaction mixture was cooled to rt, the precipitated solid was collected by filtration, washed with EtOH (min vol.) and dried to obtain the desired compound. The crude compound (C) was used as such for the next step without further purification (26.8 g, 74.1%). (M + H): 198.0.
ethyl 3-bromopyrazolo[1,5-a]pyrimidine-6-carboxylate[ No CAS ]
Yield
Reaction Conditions
Operation in experiment
100%
In ethanol; for 1.33333h;Reflux;
Ethyl 2-formyl-3-oxopropanoate (3.29 g, 22.84 mmol) and 4-bromo-lH-pyrazol-5 -amine (3.7 g, 22.84 mmol) were combined in ethanol (30 mL) and heated for 80 min at reflux. The mixture was cooled and the solid product was collected by filtration to give ethyl 3- bromopyrazolo[l,5-a]pyrimidine-6-carboxylate (6.17 g, 22.84 mmol, 100 percent yield) as a brown solid
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