The development of a simple and highly selective method for the preparation of substituted U-shaped terpyridines is described. The treatment of imine 5 with ternary iminium salts 2 leads to the terpyridines 4. A possible mechanism is discussed. The terpyridine derivatives are used for the preparation of several platinum(II) complexes 14. Complex 14e is characterized by single-crystal X-ray analysis.

An annelation reaction is presented in which 1,3-cyclohexanedione (1) and Mannich bases 6a,b are used for the preparation of functionalized bipyridines 12a, 13a, 14a and dihydropyridine derivatives 10b, 11b. All these products possess a keto group which will allow further transformations. The same concept was applied for the synthesis of the S-shaped terpyridine 25. The reaction of the Mannich base 21 with 1,3-cyclohexanedione yielded the heptacyclic terpyridine 22, which is a key intermediate for the synthesis of torands and other tridentate clefts. The ketone 12a was used for the synthesis of the quaterpyridine 26.

Reaction of the bis(enamines) 2b and 3b with acetylenedicarboxylic ester gave stable tetracyclic compounds 4b and 5b. The related compound 3a, however, led to bicyclo[5.5.0]dodecatetraenes 6a, 6b, and 7a/7b directly. 7a/7b are interrelated by a rapid [1,5]-H shift, whereas 6a and 6b do not rearrange. Hydrolysis of 6b yielded the novel cage compound 10 by dual intramolecular Michael addition.

The reaction of the enamine 4 with different β-amino ketone hydrochlorides 3a–e affords the diketones 5a–e which can be cyclized to the corresponding mono- and disubstituted tetrahydroquinolines 6a–e. Furthermore the preparation of the octahydroacridines 8f and 8g by using a straightforward multi step sequence is described.