Preparation and molecular structures of N′-(2-heteroarylmethylidene)-3-(3-pyridyl)acrylohydrazides

The crystal and molecular structures of N′-(2-furylmethylidene)-3-(3-pyridyl)acrylohydrazide and N′-(2-thienylmethylidene)-3-(3-pyridyl)acrylohydrazide are reported, and the influence of the type of the heteroatom on the aromaticity of the aromatic rings is discussed. Both molecules are nearly planar. The geometry of the acrylohydrazide arrangement is comparable to that of homologous compounds. Density functional theory (DFT) calculations were performed in order to analyze the changes in the geometry of the studied compounds in the crystalline state and for the isolated molecule. The most significant changes were observed in the values of the N–N and C–N bond lengths. The harmonic oscillator model of aromaticity index, calculated for the furan and thiophene rings, demonstrated a noticeable increase in aromaticity in comparison to isolated rings and their DFT-calculated structures. By contrast, the nucleus independent chemical shift index indicated a decrease in aromatic character of the rings containing heteroatoms.

An Efficient Synthesis of New 2-Aryl-5-phenylazenyl-1,3,4-oxadiazole Derivatives from N,N'-Diarylcarbonohydrazides

A series of new 1,3,4-oxadiazoles conjugated to aromatic substituents by an azo linker was synthesized in a four-step reaction sequence, involving cyclodehydration of a N,N'-diacylhydrazine fragment and dehydrogenation of the neighboring hydrazine fragment of the intermediate N,N'-diarylcarbonohydrazide.