Curcumin Related 1,4_Diazepines: Regioselective Synthesis, Structure Analysis, Tautomerism, NMR Spectroscopy, X¿ray Crystallography, Density Functional Theory and GIAO Calculations

The reaction of 1,2¿ethylenediamine with seven fluorinated ß¿diketones affords two different 1,4¿diazepine series depending on the experimental conditions. Their structures as well as tautomerism have been established by 1H, 13C, 15N and 19F nuclear magnetic resonance in solution supported by density functional theory calculations at the B3LYP/6¿311++G(d,p) level. The two compounds obtained from (E)¿5¿(2¿fluoro¿4¿hydroxyphenyl)¿1¿phenylpent¿4¿ene¿1,3¿dione were analyzed by X¿ray crystallography and studied by solid¿state NMR.This work was supported by Ministerio de Economía y Competitividad of Spain (CTQ2014-56833-R and CTQ2015-63997-C2-2-P and MALTA-CONSOLIDER CSD2007-00045) and Comunidad Autónoma de Madrid (MADRISOLAR2, S2009/PPQ-1533). One of us (C. I. Nieto) is indebted to UNED for a predoctoral contract (FPI “Grupos de Investigacio´n” UNEDPeer Reviewe