Four-component synthesis of ferrocene-containing 1,3,4-oxadiazoles from N-isocyaniminotriphenylphosphorane (Ph₃PNNC), a primary amine, a cyclic ketone and ferrocene carboxylic acid

GRAPHICAL ABSTRACT

ABSTRACT

The 1:1 imine intermediate created by the addition of a primary amine to a cyclic ketone is trapped by N-isocyaniminotriphenylphosphorane (Ph₃PNNC) 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.

KEYWORDS:

• N-Isocyaniminotrip-henylphos-phorane (Ph₃PNNC)
• ferrocene carboxylic acid
• cyclic ketone
• primary amine
• 1,3,4-oxadiazole
• aza-Wittig reaction

Funding

This work is funded by the grant NRF-2015-002423 of the National Research Foundation of Korea.