Structure elucidation of configurational isomers of nitrile-substituted spirocyclopropyloxindoles by NMR spectroscopy, molecular modeling, and X-ray crystallography

Study of E/Z isomerization of (arylamino)methylidenefuran-2(3H)-ones by 1 H, 13 C, 15 N spectroscopy and DFT calculations in different solvents

The structure and configuration of the series of previously unknown arylaminomethylidenefuran-2(3H)-ones have been determined in solution by ¹ H, ¹³ C, ¹⁵ N nuclear magnetic resonance spectroscopy including two-dimensional experiments such as ¹ H─¹ H COSY, dqCOSY, ¹ H─¹³ C HSQC, ¹ H─¹³ C HMBC. It was found that synthesized substances exist as an equilibrium mixture of E- and Z-enamines in solution. It was established on the basis of density functional theory calculations that the exchange between the two push-pull enamines is a simple rotation around an exocyclic partial double bond that depends on the effect of the solvents. Copyright © 2017 John Wiley & Sons, Ltd.