Four-component synthesis of ferrocene-containing 1,3,4-oxadiazoles from <i>N</i>-isocyaniminotriphenylphosphorane (Ph<sub>3</sub>PNNC), a primary amine, a cyclic ketone and ferrocene carboxylic acid

<p>The 1:1 imine intermediate created by the addition of a primary amine to a cyclic ketone is trapped by N-isocyaniminotriphenylphosphorane (Ph<sub>3</sub>PNNC) in the presence of ferrocene carboxylic acid and the corresponding iminophosphorane intermediate was formed. Afterwards, ferrocene containing 1,3,4-oxadiazole derivatives are formed via intramolecular aza-Wittig reaction of the iminophosphorane intermediate. The reaction proceeded under mild conditions at room temperature.</p>