Nitrogen → 3-Bromo-5-(piperazin-1-yl)pyrazolo[1,5-a]pyrimidine

Participants

Reaction Conditions

Reaction Steps

3-Bromo-5-chloro-pyrazolo[1,5-a]pyrimidine (15.4 g, 66.2 mmol) and piperazine [110-85-0] (56.8 g, 659.5 mmol) were ground together in a mortar to an intimate mixture and transferred to a 250 mL round bottomed flask containing a magnetic stir bar. The flask was fitted to a reflux condenser, N2 blanketed, and the reaction pot immersed in an ambient temperature oil bath. While the neat solid mixture stirred, the bath was heated to 120° C. over 0.5 h and held at nominal temperature for a total of 2 h. The bath was removed and the molten reaction allowed to cool to approximately 75° C. Ethyl acetate was cautiously added down the condenser to dissolve the reaction product to prevent its setting up into a solid mass. The reaction solution was transferred to a separatory funnel, further diluted with ethyl acetate, and washed with water. The ethyl acetate extract was dried (MgSO4) and evaporated to obtain 16.1 g of clear yellow oil. The oil was crystallized from methanol to provide 15.8 g of light yellow crystalline powder in two crops, mp. 108-109° C. 1H NMR (400 MHz, DMSO-d6) δ ppm 2.51 (s, 1 H) 3.16-3.24 (m, 3 H) 3.38 (s, 1 H) 3.93-4.00 (m, 3 H) 6.85 (d, J=7.83 Hz, 1 H) 8.03 (s, 1 H) 8.78 (d, J=8.08 Hz, 1 H) 9.61 (br. s., 1 H). 13C NMR (100 MHz, DMSO-d6) δ ppm 41.25, 42.16, 77.73, 97.78, 136.77, 144.01, 144.18, 155.53. LRMS (ESI) m/z 282.0/284.0 [(M+H)]+, calc'd for C10H12BrN5: 282.14.

Provenance & Evidence