Scheme 1:

a) SOCl₂, CH₃OH, rt, 15 h, 98%; b) PTSA, NaNO₂ then NaN₃, H₂O, CH₃CN, rt, 15 h, 63%; c) 4-ethynyltrifluorotoluene, sodium ascorbate, CuSO₄, THF, H₂O, rt, 1 h, 84%; d) LiOH, MeOH, 60 °C, 2 h, 76%; e) B₂pin₂, KOAc, PdCl₂(dppf), dioxane, 70 °C, 15 h, 87%; f) i) 10% NaOH, H₂O₂, THF, 0 °C, 0.5 h; ii) KOH, MeOH, water, 50 °C, 5 h, 86%.