Scheme 2. Preparation of methylated arylbenzofuran 4 and diarylbenzofuran 5. Reagents and conditions: (a) K₂CO₃, acetone, CH₃I, r.t., 18 h, 42%; (b) K₂CO₃, acetone, reflux, 3 h, 98%; (c) Bi(OTf)₃, DCM, reflux, 23 h, 81%; (d) Pd(OAc)₂, PCy₃·HBF₄, Cs₂CO₃, Pivalic acid, DMA, 140 °C, 20 h, 87.0%.