13C NMR spectra of azachalcones

Abstract

13C NMR spectral parameters were obtained for chalcone and fourteen its aza- and diazaanalogues. Relative conformation of the carbonyl group with respect to the double bond was studied using changes in 3J(C(1')-Hα) and PCILO method. PCILO calculations together with experimental results show that with 2'-, 3'-, and 4'-azachalcones the s-cis isomer is the most stable form. Whereas the molecule of 2'-azachalcone is planar or nearly planar, in 3'- and 4'-azachalcones the carbonyl group and the olefinic bond planes make angle of 45°.