Fig. 3. Synthetic pathways.

Synthesis of 13–15 (a), nitrobenzoic acid precursors 44g (b), 44h (c) and 44l (d), and 21 and 26 (e). Reagents and conditions: (i) K₂CO₃, DMF, 80 °C, 50–98%. (ii) H₂, Pd/C, EtOAc, rt, 64–86%. (iii) 2-nitrobenzoic acid (44 m), EDC·HCl, DMAP, CHCl₃, 75 °C, 54–93%. (iv) 2-naphthoic acid (48a), EDC·HCl, DMAP, CHCl₃, 75 °C, 65%. (v) 2-naphthoyl chloride (49a), pyridine, THF, 75 °C, 42–45%. (vi) (I) LiOH, THF, H₂O, rt – 50 °C (II) 5% HCl, 98–99%. (vii) (I) CuCN, DMF, 150 °C (II) toluene, 130 °C, 92%. (viii) 55% H₂SO₄ (aq.), 120 °C, 45%. (ix) HNO₃, HOAc, Ac₂O, 0 °C, 52–76%. (x) KMnO₄, pyridine, H₂O, 110 °C, 18%. (xi) BBr₃, CH₂Cl₂, 0 °C–rt, 22–65%. X = O, NH; R₁ = H, CH₃.