title: (13)C NMR spectral assignment of 1,4-diarylpiperazinones.
abstract: The piperazinone derivatives have potential application in the pharmaceutical, polymer and textile fields. The present work describes the preparation of a series of new 1,4-diarylsubstituted-2-piperazinones by condensation of substituted N,N'-bis-(2-hydroxyphenyl)-ethylenediamines with glyoxal and the complete (13)C NMR spectral assignment accomplished using APT, HMQC and HMBC techniques. Substituent chemical-shift effects (SCS) were calculated, which showed different values for the lactam- and amine-substituted aromatic rings. The results show that predictions based on SCS effects are not simple for these molecules due to electronic and steric effects. Moreover, in the case of the ortho-substituted derivative 2 g, the NMR spectra reveal a dynamic behavior related to restricted rotation of the phenyl groups (atropisomerism).
authors.affiliation: Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apdo. Postal 14-740, 07000, México, D.F., México.
authors.forename: Arturo
authors.initials: A
authors.lastname: Abreu
authors.forename: Ma Eugenia
authors.initials: ME
authors.lastname: Ochoa
authors.forename: Norberto
authors.initials: N
authors.lastname: Farfán
authors.forename: Rosa
authors.initials: R
authors.lastname: Santillan
mesh_terms: D002247:Carbon Isotopes; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D010879:Piperazines / Q000138:chemical synthesis* / Q000737:chemistry* / Q000145:classification
chemical_list: D002247:Carbon Isotopes; D010879:Piperazines