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Reactions of N-isocyaniminotriphenylphosphorane (Ph3PNNC) with aromatic bis-aldehydes (isophthalaldehyde and terphthalaldehyde) in the presence of 3-phenyl-2-propynoic acid and secondary amines proceed smoothly at room temperature and in neutral conditions to afford sterically congested 1,3,4-oxadiazole derivatives in high yields. The reaction proceeds smoothly and cleanly under mild conditions and no side reactions were observed. [ABSTRACT FROM AUTHOR]

New bis(thiadiazole) derivatives 7a-m were prepared in good yields by the reaction of the appropriate hydrazonoyl halides 4a-e with the bis-Schiff bases 9a-c. Similarly, the bis(thiadiazole) derivatives 17a-g were prepared by the reaction of the novel bis-hydrazonoyl halides 13a-d with schiff bases 3a-d. [ABSTRACT FROM AUTHOR]