Scheme 2. Synthesis of DCF Derivatives 1b–1d.

Reagents and conditions: (a) SOCl₂, CH₂Cl₂, rt–50 °C, 1–3 h, then 40% NH(CH₃)₂-H₂O, 0 °C, 30 min, 71–83%; (b) 2,6-dichloroaniline (for 8c) or 2,6-dichloro-4-fluoroaniline (for 8b and 8d), K₂CO₃, Cu powder, CuI, toluene, reflux, 62–64 h, 66–90%; (c) NaOH, C₂H₅OH, H₂O, reflux, 2.5–4 h, 90–99%.