A convenient synthesis of substituted 2,2′:6′,2″-terpyridines

The 2,2′:6′,2″-terpyridines 7a–c were prepared in good yield by reacting α-acetoxy-α-chloro-β-keto-esters 3a–c with bis-amidrazone 4 and 2,5-norbornadiene 6 in ethanol at reflux. Compounds 3a and 3b gave the 2,2′:6′,2″-terpyridines 9a and 9b, respectively, in moderate yield when treated with compound 4 and enamine 8.