Reagents and conditions:
(a)
(CF3CO)2O, CH2Cl2, Et3N, rt, 1 h, 87%; (b) (i) 2-chloropyridine, CH2Cl2, −78 °C, then Tf2O, (ii) μwave,
160 °C, 5 min, 56%; (c) MnO2, xylene, 130 °C,
18 h, 44%; (d) 70% mCPBA, CH2Cl2, 5–10 °C, then warm to rt for 18 h, 80%; (e) F3C-SiMe3, THF, molecular sieves, K–OtBu, −20 °C, 46–54%; (f) 1-(4-methoxybenzyl)-1H-pyrazolo[3,4-b]pyridine-3-amine, 5 mol
% Pd2(dba)3, 5 mol % XantPhos, Cs2CO3, 1,4-dioxane, μwave, 140 °C, 30 min, 65%;
(g) TFA, toluene, 100 °C, 30 min, 80%.