Synthesis of Terpyridines: Simple Reactions—What Could Possibly Go Wrong?

The preparation of 2(4)-functionalized 1(2),2(2):2(6),3(2)-terpyridines (4′-functionalized 3,2:6′,3″-terpyridines) by the reaction of three 4-alkoxybenzaldehydes with 3-acetylpyridine and ammonia was investigated; under identical reaction conditions, two (R =(n)C(4)H(9), C(2)H(5)) gave the expected products whereas a third (R = (n)C(3)H(7)) gave only a cyclohexanol derivative derived from the condensation of three molecules of 3-acetylpyridine with two of 4-(n-propoxy)benzaldehyde. A comprehensive survey of “unexpected” products from reactions of ArCOCH(3) derivatives with aromatic aldehydes is presented. Three different types of alternative product are identified.