title: Study of spontaneous E/Z isomerization of bis[(Z)-cyanomethylidene]-diazapentacyclodienedicarboxylates by1H,13C, and15N NMR spectroscopy, X-ray, and quantum chemical calculation data.
abstract: X-ray data show that the diethyl 6,13-bis[(Z)-cyanomethylidene]-5,5,14,14-tetramethyl-4,15-dioxa-7,12-diazapentacyclo[9.5.2.02,10.03,7.012,16]octadeca-8,17-diene-10,17-dicarboxylate is formed as the ZZ isomer and diastereomer with the (1R*,2R*,3R*,10S*,11R*,12R*,16R*) configuration. The1H,13C, and15N NMR data exhibit that on standing in chloroform-d solution, there is a spontaneous isomerization of this compound resulting in a thermodynamically stable mixture of the ZZ, ZE, EE, and EZ isomers with the same backbone. Using the 2D [1H-1H] COSY, [1H-13C] HSQC, and [1H-13C,1H-15N] HMBC NMR techniques and quantum chemical calculations makes it possible a complete assignment of signals in the1H,13C, and15N NMR spectra of each of the isomers. Such isomerization does not occur for similar compounds with the more bulky substituents at the 1,3-oxazolidine rings. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia.
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Afonin
authors.affiliation: A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia.
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Vashchenko
authors.affiliation: A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia.
authors.forename: Alexander I
authors.initials: AI
authors.lastname: Albanov
authors.affiliation: A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia.
authors.forename: Valentina V
authors.initials: VV
authors.lastname: Nosyreva
authors.affiliation: A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia.
authors.forename: Anastasiya G
authors.initials: AG
authors.lastname: Mal'kina
authors.affiliation: A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia.
authors.forename: Boris A
authors.initials: BA
authors.lastname: Trofimov
keywords: 13C NMR; 15N NMR; 1H NMR; B3LYP and GIAO calculations; NMR; X-ray; bis[(Z)-cyanomethylidene]-diazapentacyclodienedicarboxylates; spontaneous E/Z isomerization