Scheme 1. Synthetic methodology utilized to generate a focused library of 5,6,7-substituted pyrazolopyrimidines and ¹⁸F-6b^α.

^αReagents and conditions: (a) NaOH, NaI, microwave, 80 °C, 40 min, 80% EtOH in H₂O, 70%; (b) hydrazine, AcOH, microwave, 90 °C, 40 min, EtOH, 42%; (c) microwave, 140–190 °C, 45min, EtOH, 10–90%; (d) HTPB, microwave, 110 °C, 40 min, aqueous HBr; (e) NaH, 2-fluoroethyl-4-methylbenzenesulfonate, microwave, 120 °C, 30 min, dry THF. (f) ethylene di(p-toluenesulfonate), NaH, microwave, 120 °C, 30 min, dry THF, 45%. (g) Fluoride-18 ion, K⁺-K_2.2.2/K₂CO₃, 99 °C, 20 min, dry DMSO.