Scheme 4. Synthetic Route toward Novel Subsite 3 Aminobenzothiazole Derivatives.

Conditions: (a) tBuOOH, Cs₂CO₃, MeOH, 20–30 °C, 2 h, 81%; (b) NaOMe, MeOH, 1,4-dioxane, 80 °C, 2 h, 70%; (c) KSCN, Br₂, AcOH, 10 to 65 °C, 2.5 h, 61%; (d) CH₃CH₂Br, Cs₂CO₃, DMF, 60 °C, 4 h, 57%; (e) NIS, AcOH, 25 °C, 1 h, 96%; (f) N-TIPS-pyrrole derivative (27, 28, 30), KF, Cs₂CO₃, DMSO, 70 °C, 1 h, 50–73%; (g) BBr₃, CH₂Cl₂, 0 to 25 °C, 24 h, 73–79%.