Preparation of sterically congested 1,3,4-oxadiazole derivatives from Nisocyaniminotriphenylphosphorane,aromatic acids, cyclopentanone andprimary amines

Reactions of N-isocyaniminotriphenylphosphorane with cyclopentanone have been studied in thepresence of aromatic carboxylic acids and primary amines. The reactions were proceededsmoothly at room temperature under neutral conditions in order to afford sterically congested1,3,4-oxadiazole derivatives by an intramolecular Aza-Wittig cyclization in CH2Cl2 in excellentyields. The structures of the products were deduced from their IR, Mass, ¹H NMR, and ¹³C NMRspectra. The reaction proceeds smoothly and cleanly under mild conditions and no side reactionswere observed. The method offers a mild, simple, and efficient route for the preparation of fullysubstituted 1,3,4-oxadiazoles from cyclopentanone, primary amines, Nisocyaniminotriphenylphosphoraneand aromatic carboxylic acids. Easy work-up, high yieldsand fairly mild reaction conditions make it a useful procedure in comparison to the modernsynthetic methodologies.

Keywords:

N-isocyaniminotriphenylphosphorane , cyclopentanone , aromatic carboxylic acids , primary amines , 1 , 3 , 4-oxadiazole