Scheme 3. Synthesis of 4-Oxo-[1]benzopyrano[4,3-c]pyrazole Analogue 8l–n (Method C).

Reagents and conditions: (a) 21 (4-Cl-3-OMePhNHMe) or 2k (4-Cl-3-OMePhNH₂), K₂CO₃, CH₂Cl₂, 0 °C to rt; (b) for 4l, t-butyl carbazate, K₂CO₃, KI, acetone, 65 °C, 18 h or for 4m, t-butyl carbazate, DIPEA, toluene 105 °C, 16 h; (c) TFA in CH₂Cl₂ (1:4), 2 h, then 7a (or 4-chloro-3-formyl-7-methylcoumarin, 7b), AcOH (cat.), EtOH, 105 °C, 20 min.