Studies of NMR Chemical Shifts of Chalcone Derivatives of Five-membered Monoheterocycles and Determination of Aromaticity Indices

摘要

A series of the chalcone derivatives of the five-membered monoheterocyclic compounds, (￡)-l-aryl-3-heteroarylpropen-1-ones, were prepared by aldol condensation of the corresponding aldehydes of thiophene, pyrrole, and furan with m- and P-substituted acetophenones. Similar condensation of the acetyl compounds of the heterocycles with m- and P-substituted benzaldehydes gave another series of the chalcone derivatives, (E)-l-heteroaryl-3-arylpropen-l-ones. The 13C chemical shift values (5C) of the chalcone derivatives were determined in order to find if they correlated with the Hammett a values. A good correlation, especially for the β-C for both series, was found for the 13C chemical shift values (5C) of the chalcone derivatives with the Hammett o values. The chemical shift values of the β-C of the heterocyclic compounds were plotted against those of the benzene derivatives. The resulting slopes were found to be close to the values of the aromaticity indices.