Scheme 1. Synthesis of compounds 2–4, 6. Reagents and conditions: (a) (i) Pd(amphos)Cl2, bis(tributyltin), dioxane, reflux, 3 h; (ii) halide derivative, Pd(PPh3)4, dioxane, 90 °C, o/n; (iii) 1) Pd2(bda)3/xantphos, tert-butyl carbamate, Cs2CO3, dioxane, 90 °C, o/n, 2) HCl in dioxane (for 2); (iv) NH3 aq., DMSO, 100 °C, o/n (for 3). (b) (v) 1) boronic ester, XPhosPdG2 (cat.), K3PO4, dioxane/H2O, 95 °C, 2–16 h; 2) HCl, dioxane/H2O, 60 °C, 3–16 h; (c) (vi) tetraethylammonium cyanide, DABCO, DMSO, 140 °C, 1.5 h. (vii) TFA, 65 °C, o/n. See ESI† for details.
