SYNTHESIS OF STABLE TAIL-TO-TAIL CONJUGATED PRIMARY ENAMINES CONTAINING HETARENE SUBSTITUENTS

A method is described that allows the preparation of stable conjugated primary enamines containing furyl or pyridyl substituents. In a templ ate reaction (butadiene)zirconocene is 1,4-selectively coupled to two 2-cyanopyridine equivalents to give the nine-membered metallacycle 8b. Subsequent treatment with methanol removes the bent metallocene templ ate and leads to the formation of 1,6-diamino-1,6-bis(2-pyridyl)-1,3,5 -hexatriene (9b). The 1,6-diamino-1,6-bis(2-furyl)-1,3,5-hexatriene sy stem (9a) was prepared analogously (69% isolated). Subsequent addition of benzonitrile to (butadiene)ZrCp2, followed by 2-cyanopyridine or 2 -cyanofurane gave the respective unsymmetrically substituted 1,6-diami nohexatrienes in good yield.