SYNTHESIS OF STABLE PRIMARY ENAMINES FROM (BUTADIENE)ZIRCONOCENE AND BENZYLIC NITRILES

(Butadiene)zirconocene adds two molar equivalents of benzyl cyanide to give the chiral nine-membered metallacycle 4. Controlled hydrolysis ( CH3OH) of 4 yields the stable conjugated primary enamine 2,7-diamino-1 ,8-diphenyl-2,4 6-octatriene (6) (greater than or equal to 70% isolate d). (2-Pyridyl)acetonitrile reacts similarly with the (butadiene)zirco nocene reagent. Subsequent controlled hydrolysis now produces a non-co njugated primary enamine, namely 2,7-diamino-1,8-di(2-pyridyl)-1,4,7-o ctatriene (9). In this case, conjugative stabilization of a primary en amine is overcome by functional group stabilization by the 2-pyridyl s ubstituent at the beta-enamine position.