Synthesis of 4- and additional 5-substituted analogues of 1a
aReagents and conditions: (a) bis(pinacolato)diboron, potassium acetate, PdCl2(dppf)2, DMF, 105 °C, 3 h; (b) 4-nitrophenyl boronic acid, Na2CO3, Pd(PPh3)4, DME, H2O, 70–80 °C, overnight; (c) boronic acids, Na2CO3, Pd(PPh3)4, DME, H2O, 70–80 °C, overnight; (d) CuI, KI, HMPA, 150 °C, 3 h;