An efficient and rapid procedure for the N-alkyl enamination from thioketones to push–pull (E/Z)-enamine derivatives is reported. The starting thioketone 2 was obtained by regiose- lective thionation of 3-benzoylpyrrolo[2,3-b]quinoxalin-2-one (1) with Lawesson’s reagent (LR). NMR and X-ray crystal structure analyses of 1-aryl-3-(alkylaminophenylmethylidene)pyrrolo[2,3-b]quinoxalin-2-ones 3–6 confirmed that the E diastereoisomers predominated. Interconversion of the isolated E form of 3b and 4a into the Z configuration and their E/Z equilibria in []DMSO were studied by tempera- ture-dependent NMR spectroscopy. The photophysical properties of compounds 1–6 are also reported. We found that the non-fluorescent compounds 3a–6a are chemosensors for the zinc ion. Fluorescent titrations of these sensors with zinc- (II) acetate showed that compound 6a has the best working range of zinc concentrations with = 3.77 00 0.51 M.