Scheme 3.
Synthesis of Compounds for Exploring the Linking Heteroatom Moietya
aReagents and conditions: (a) Cs2CO3, DMSO, 125 °C, 48 h; (b) Pd(dppf)Cl2, KOAc, B2(pin)2, dioxane, 80 °C, 18 h; (c) Pd(PPh3)4, K2CO3, dioxane, H2O2, 120 °C, 25 min; (d) NaH, DMF, 1 h, 80 °C, then 25−0 °C, R-I, 2 h.