Scheme 1.

2,5-bis(imidazolinyl)thiophene (L1–L3) and 2,5-bis(oxazolinyl) thiophene (L4 and L5). Reaction conditions: (I) SOCl₂ (8 mL/g), cat. DMF, 24 h, reflux; (II) i. CH₂Cl₂, TEA (5 eq.), −10 °C; ii. Amino alcohol (3a–c) (2.1 eq.); (III) 4a, SOCl₂ (8.8 mL/g), refluxed, 24 h; (IV) i. 5a, Et₂O, TEA (12.0 eq.), 0 °C; ii. 2.5 eq. R₁NH₂ (6a–c), 0 °C, then r.t., 12 h; (V) NaOH (15% aq. soln., 15 mL/g), r.t, 24 h; (VI) 4b–4c, Tosylchloride (1.25 eq.), DMAP (cat. 0.1 eq.), TEA (4.0 eq.), CH₂Cl₂, r.t, 48 h, N₂.