Scheme 3:

Synthesis of compounds (±)-6g-l^a

^aReagents and conditions: a) Appropriate aryl aldehyde, Cs₂CO₃, dioxane, 110 °C, 14 h 89–100%; b) for 23a-c: phenylhydrazine, AcOH, 80 °C, 14 h; for 23d: 4-methoxyphenylhydrazine, AcOH, 80 °C, 14 h, 30–48%; c) NaBH₄, MeOH, 25 °C, 12 h or H₂, Pd/C, MeOH, 25 °C, 12 h, 50–79%; d) for (±)-25a-c and 25f: methyl 4-formylbenzoate, EtOH, AcOH, NaBH₃CN, 40 °C, 14 h; for (±)-25d: 20, EtOH, AcOH, NaBH₃CN, 40 °C, 14 h; for (±)-25e: 16, NaBH(OAc)₃ DCM, 40 °C, 14 h, 20–84%; e) NH₂OH (50% in H₂O), KOH, DCM/MeOH from 0 °C to 25 °C, 12 h, 18–79%.