General procedure for the synthesis of 4′-O-substituted
2,2′:6′,2″-terpyridine-6,6′
′-dicarboxylic acid. Diethyl
1′-hydro-4′-oxo-2,2′:6′,2″-terpyridine-6,6″-dicarboxylate
was reacted with an electrophile in the presence of NaH in DMF for 15 h.
Purification using SiO2 gel column chromatography afforded
4′-O-substituted diethyl
2,2′:6′,2″-terpyridine-6,6″-dicarboxylate
derivative (Step-B). The product was hydrolyzed using NaOH to yield
4′-O-substituted
2,2′:6′,2″-terpyridine-6,6″-dicarboxylic acid
(Step-C).